SE544138C2 - A method for controlling an electrical circuit controlling a direct current motor and such an electrical circuit - Google Patents

Abstract

A control arrangement (150) and a method for controlling an electrical circuit (202) configured to control a direct current motor (185), which is operable between a first end stop (S1) and a second end stop (S2). The electrical circuit (202) comprises first, second and third switching devices (R1, R2, Rs). The first switching device (R1) controls the direct current motor (185) in a first direction. The second switching device (R2) controls the direct current motor (185) in a second direction. The third switching device (Rs) is an electric power supply switching device (Rs). The method comprises: while the second switching device (R2) is controlled to remain open and the third switching device (Rs) is controlled to remain open, controlling (301) the first switching device (R1) to switch from an open position to a closed position; and when the first switching device (R1) has been controlled to switch from an open position to a closed position and is controlled to remain closed while the second switching device (R2) is controlled to remain open, controlling (304) the third switching device (Rs) to switch from an open position to a closed position in order to operate the direct current motor (185) in the first direction toward the second end stop (S2). An electrical circuit (202) including the control arrangement. A direct current motor unit (204) including the electrical circuit (202).

Description

A METHOD FOR CONTROLLING AN ELECTRICAL CIRCUIT CONTROLLING ADIRECT CURRENT MOTOR AND SUCH AN ELECTRICAL CIRCUIT Technical field Aspects of the present invention relate to a method for controlling an electrical circuit,the electrical circuit being configured to control a direct current motor. Further, aspectsof the present invention relate to a control arrangement for controlling an electricalcircuit, the electrical circuit being configured to control a direct current motor. Aspectsof the present invention also relate to such an electrical circuit for controlling a direct current motor.

Background ln general, for operating a direct current (DC) motor, for example in two differentdirections, an electrical circuit, which includes switching devices, such as relays, isused. When at least two relays are used, the direct current motor may be operated intwo different directions, for example a forward direction and a backward direction.These two relays may be included in a so-called H-bridge. A third relay may be addedbetween the H-bridge and an electric power source energizing the direct current motor in order to improve safety, for example.

Summary The inventors of the present invention have found that special attention should be paidto each relay, which is an example of a switching device, of the electrical circuitcontrolling the direct current motor. Over time, a relay may be subjected to mechanicalfailures. The inventors of the present invention have found that there are primarily twotypes of mechanical failures of the relays that should be considered and addressedwith regard to an electrical circuit using relays for controlling a direct current motor.

When a relay is closed (i.e. switched to a closed position) to form a capacitive circuit,the relay may exhibit a large electric current at the moment of contact. Said largeelectric current may weld the contact surfaces of the relay such that the relay gets stuck in a closed position. For relays, this phenomenon may be called “welding” and isone of the primarily two types of mechanical failures mentioned above.

When a re|ay opens an inductive circuit the back electromotive force (EMF) will besignificant. The direct current motor may be seen as an inductive circuit. The back EMFproduces a significantly high voltage across the re|ay, whereby the re|ay exhibits arcing(electricity flowing through the air). The discharge during arcing will decomposeorganic matter contained in the air and form black deposits, which contaminate thecontact surfaces of the re|ay such that the re|ay may get stuck in an open position. Forrelays, this phenomenon may be called “arcing” and is the other one of the primarilytwo types of mechanical failures mentioned above.

When a direct current motor is used for operating a movable mechanical apparatus orstructure which is movable between a first end position and a second end position, thedirect current motor may be operable between a first end stop and a second end stop.The first end position of the mechanical apparatus and the corresponding first end stopof the direct current motor may be safe positions. The second end position of themechanical apparatus and the corresponding second end stop of the direct currentmotor may be unsafe positions. Thus, in order to control the mechanical apparatusand the direct current motor in a secure and safe manner, it should be avoided that thedirect current motor gets stuck at the second end stop, which is an unsafe position, incase of a re|ay failure, since then the mechanical apparatus would also be stuck in anunsafe position, i.e. its second end position. This is disclosed and exemplified in furtherdetail in the detailed description hereinbelow.

Some conventional electrical circuits for controlling a direct current motor orconventional controlling of such electrical circuits do not provide a control of the directcurrent motor which is sufficiently secure. For example, in some conventional electricalcircuits configured to control a direct current motor, the security measures to avoid thatthe direct current motor gets stuck in an unsafe position are missing or are notsufficient.

An object of the embodiments of the invention is to provide a solution which mitigatesor solves drawbacks and problems of conventional solutions.

The above and further objects are solved by the subject matter of the independentclaims. Further advantageous embodiments of the invention can be found in thedependent claims.

According to a first aspect of the invention, the above mentioned and other objects areachieved with a method for controlling an electrical circuit, the electrical circuit beingconfigured to control a direct current motor, the direct current motor being operablebetween a first end stop and a second end stop, the electrical circuit comprising an electrically operable first switching device switchable between an openposition and a closed position, an electrically operable second switching device switchable between an openposition and a closed position, and an electrically operable third switching device switchable between an openposition and a closed position, wherein in the closed position the first switching device is configured to providea first connection of the direct current motor to an electric power source to operate thedirect current motor in a first direction toward the second end stop, wherein in the open position the first switching device is configured to beconnected to ground, wherein in the closed position the second switching device is configured toprovide a second connection of the direct current motor to the electric power source tooperate the direct current motor in a second direction toward the first end stop, wherein in the open position the second switching device is configured to beconnected to ground, and wherein in the closed position the third switching device is configured toprovide a third connection between the electric power source and the first connectionand between the electric power source and the second connection, wherein the method comprises: while the second switching device is controlled to remain in the open positionand the third switching device is controlled to remain in the open position, controllingthe first switching device to switch from the open position to the closed position; and when the first switching device has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position whilethe second switching device is controlled to remain in the open position, controlling thethird switching device to switch from the open position to the closed position in orderto operate the direct current motor in the first direction toward the second end stop.

The inventors of the present invention have concluded that the following unwantedsituations should be avoided, since they may lead to that the direct current motor getsstuck at the second end stop, which may be an unsafe position, because of or in caseof a switching device failure (such as a relay failure), i.e. if one or more of the switchingdevices fails/fail: o The third switching device is stuck in the open position when the direct current motor is away from the first end stop (safe end position);o The first switching device is stuck in the closed position; and o The second switching device is stuck in the open position.

Since the first and third switching devices are controlled to switch from the openposition to the closed position, the direct current motor is operated in the first directiontoward the second end stop (unsafe end position) and away from the first end stop(safe end position). Thus, assuming that there is no switching device failure and thefirst, second and third switching devices are initially in the open position, the directcurrent motor will move toward the second end stop (unsafe end position) when thefirst and third switching devices are in the closed position. Since the first switchingdevice closes an open circuit, i.e. the first switching device is being closed, or switchedto the closed position, to form an open circuit, there is no load and the first switchingdevice is exposed to minimal wear. Thus, there is no risk, or a minimal risk, that thefirst switching device will get stuck in the closed position. When the third switchingdevice is closed subsequently to the closing of the first switching device, there is a riskof welding, as discussed above. However, if the third switching device gets stuck at this stage, it will get stuck in the closed position. The initial control of the first switchingdevice to switch from the open position to the closed position and the subsequentcontrol of the third switching device to switch from the open position to the closedposition may be seen as a first part of a first sequence, when the direct current motoris to be operated in the first direction, away from the first end stop (safe end position)and toward the second end stop (unsafe end position).

According to the method of the first aspect, the first switching device will never closethe circuit last, when the direct current motor is operated in the first direction towardthe second end stop (unsafe end position), whereby at least one of the above-mentioned unwanted situations to be avoided is avoided in an efficient manner. Anadvantage of the method according to the first aspect is that an improved and moresecure control of the direct current motor is provided. An advantage of the methodaccording to the first aspect is that an improved control of the electrical circuit isprovided, which efficiently controls the direct current motor such that the direct currentmotor does not get stuck in an unsafe position, or at least the risk of having the directcurrent motor getting stuck in an unsafe position is effectively reduced or minimized.

According to an advantageous embodiment of the method according to the first aspect,the method comprises: when the direct current motor has been operated to a first position while thesecond switching device is controlled to remain in the open position and the thirdswitching device is controlled to remain in the closed position, controlling the firstswitching device to switch from the closed position to the open position; and when the first switching device has been controlled to switch from the closedposition to the open position and is controlled to remain in the open position while thesecond switching device is controlled to remain in the open position, controlling thethird switching device to switch from the closed position to the open position.Since the first switching device opens a circuit, i.e. the first switching device is beingopened, or switched to the open position, to form an open circuit, there is a risk ofarcing, as discussed above. However, if the first switching device gets stuck at thisstage, it will get stuck in the open position, and it will not be possible to operate thedirect current motor in the first direction toward the second end stop (unsafe end lO position) next time the direct current motor is controlled to operate toward the secondend stop (unsafe end position). However, it will be possible to operate the direct currentmotor in the second direction toward the first end stop (safe end position). Since thethird switching device opens an already open circuit, i.e. the third switching device isbeing opened, or switched to the open position, to open an already open circuit, thereis no load and the third switching device is exposed to minimal wear. Thus, there is norisk, or a minimal risk, that the third switching device will get stuck in the open position.The control of the first switching device to switch from the closed position to the openposition and the subsequent control of the third switching device to switch from theclosed position to the open position may be seen as a second part of said firstsequence, when the direct current motor is to be operated in the first direction, awayfrom the first end stop (safe end position) toward the second end stop (unsafe endposition). According to this embodiment, the third switching device will never open thecircuit first, when the direct current motor is operated in the first direction toward thesecond end stop (unsafe end position), whereby at least one of the above-mentionedunwanted situations to be avoided is avoided in an efficient manner. An advantage ofthis embodiment is that an improved and more secure control of the direct currentmotor is provided. An advantage of this embodiment is that an improved control of theelectrical circuit is provided, which efficiently controls the direct current motor such thatthe direct current motor does not get stuck in an unsafe position, or at least the risk ofhaving the direct current motor getting stuck in an unsafe position is effectively reducedor minimized. The first position may be a desired first position. The first position maycorrespond to the second end stop.

According to a further advantageous embodiment of the method according to the firstaspect, the method comprises: while the first switching device is controlled to remain in the open position andthe second switching device is controlled to remain in the open position, controlling thethird switching device to switch from the open position to the closed position; and when the third switching device has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position whilethe first switching device is controlled to remain in the open position, controlling the second switching device to switch from the open position to the closed position in orderto operate the direct current motor in the second direction toward the first end stop.Since the second and third switching devices are controlled to switch from the openposition to the closed position, the direct current motor is operated in the seconddirection toward the first end stop (safe end position) and away from the second endstop (unsafe end position). Thus, assuming that there is no switching device failureand the first, second and third switching devices are initially in the open position, thedirect current motor will move toward the first end stop (safe end position) when thesecond and third switching devices are in the closed position. Since the third switchingdevice closes an open circuit, i.e. the third switching device is being closed, or switchedto the closed position, to form an open circuit, there is no load and the third switchingdevice is exposed to minimal wear. Thus, there is no risk, or a minimal risk, that thethird switching device will get stuck in the closed position. When the second switchingdevice is closed subsequently to the closing of the third switching device, there is arisk of welding, as discussed above. However, if the second switching device getsstuck at this stage, it will get stuck in the closed position. Then, the third switchingdevice will be able to stop the direct current motor at the first end stop (safe endposition) by being controlled to switch from the closed position to the open position.The control of the third switching device to switch from the open position to the closedposition and the subsequent control of the second switching device to switch from theopen position to the closed position may be seen as a first part of a second sequence,when the direct current motor is to be operated in the second direction, away from thesecond end stop (unsafe end position) and toward the first end stop (safe end position).An advantage of this embodiment is that an improved and more secure control of thedirect current motor is provided. An advantage of this embodiment is that an improvedcontrol of the electrical circuit is provided, which efficiently controls the direct currentmotor such that the direct current motor does not get stuck in an unsafe position, or atleast the risk of having the direct current motor getting stuck in an unsafe position iseffectively reduced or minimized.

According to another advantageous embodiment of the method according to the firstaspect, the method comprises: when the direct current motor has been operated to a second position whilethe first switching device is controlled to remain in the open position and the secondswitching device is controlled to remain in the closed position, controlling the thirdswitching device to switch from the closed position to the open position; and when the third switching device has been controlled to switch from the closedposition to the open position and is controlled to remain in the open position while thefirst switching device is controlled to remain in the open position, controlling the secondswitching device to switch from the closed position to the open position.Since the third switching device opens a circuit, i.e. the third switching device is beingopened, or switched to the open position, to form an open circuit, there is a risk ofarcing, as discussed above. However, if the third switching device gets stuck at thisstage, it will get stuck in the open position, and it will not be possible to operate thedirect current motor next time the direct current motor is controlled to operate towardany direction. Thus, the direct current motor will be incapacitated at the first end stop(safe end position). Since the second switching device opens an already open circuit,i.e. the second switching device is being opened, or switched to the open position, toopen an already open circuit, there is no load and the second switching device isexposed to minimal wear. Thus, there is no risk, or a minimal risk, that the secondswitching device will get stuck in the open position. The control of the third switchingdevice to switch from the closed position to the open position and the subsequentcontrol of the second switching device to switch from the closed position to the openposition may be seen as a second part of said second sequence, when the directcurrent motor is to be operated in the second direction, away from the second end stop(unsafe end position) and toward the first end stop (safe end position). According tothis embodiment, the second switching device will never open the circuit first, when thedirect current motor is operated in the second direction toward the first end stop (safeend position), whereby at least one of the above-mentioned unwanted situations to beavoided is avoided in an efficient manner. An advantage of this embodiment is that animproved and more secure control of the direct current motor is provided. Anadvantage of this embodiment is that an improved control of the electrical circuit isprovided, which efficiently controls the direct current motor such that the direct currentmotor does not get stuck in an unsafe position, or at least the risk of having the directcurrent motor getting stuck in an unsafe position is effectively reduced or minimized.

The second position may be a desired second position. The second position maycorrespond to the first end stop.

According to yet another advantageous embodiment of the method according to thefirst aspect, the method comprises: while the second switching device is controlled to remain in the open position,while the third switching device is controlled to remain in the open position, and whilethe first switching device is controlled to switch from the open position to the closedposition, monitoring any movement of the direct current motor; and if a movement of the direct current motor is registered, determining that thethird switching device is stuck in the closed position.lf the third switching device, which may be considered to be a safety switching device,is stuck in the closed position, the direct current motor may still be operated toward thefirst end stop and the second end stop, as long as the first and second switching deviceare still working. However, the third/safety switching device will be incapacitated andthe operation of the direct current motor is dependent on the first and second switchingdevices only. This is an unwanted situation with regard to a secure control of the directcurrent motor. Therefore, it may be critical to diagnose that the third/safety switchingdevice is stuck in the closed position. The sequences of the control of the electricalcircuit can continue until the direct current motor is back at the first end stop (safe endposition) or the second position, but the direct current motor should thereafter not becontrolled or operated until the failed third switching device, which is stuck in the closedposition, has been replaced by a unbroken controllable and switchable third switchingdevice, or possibly repaired. An advantage of this embodiment is that a faulty or failedthird/safety switching device, which is stuck in the closed position, can be diagnosedwhile ensuring that the direct current motor can be returned to the first end stop (safeend position) or the second position in case of a failed third/safety switching device.An advantage of this embodiment is that an improved and more secure control of thedirect current motor is provided. An advantage of this embodiment is that an improvedcontrol of the electrical circuit is provided, which efficiently controls the direct currentmotor such that the direct current motor does not get stuck in an unsafe position, or atleast the risk of having the direct current motor getting stuck in an unsafe position iseffectively reduced or minimized.

According to still another advantageous embodiment of the method according to thefirst aspect, the method comprises: when the first switching device has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position, whilethe second switching device is controlled to remain in the open position, and while thethird switching device is controlled to switch from the open position to the closedposition, monitoring any movement of the direct current motor; and if a non-movement of the direct current motor (i.e. the direct current motor doesnot move) is registered, determining that one or more of the following group ofsituations is/are valid: o The third switching device is stuck in the open position;o The first switching device is stuck in the open position; ando The second switching device is stuck in the closed position.

An advantage of this embodiment is that one or more faulty or failed switching devicescan be diagnosed while ensuring that the direct current motor does not leave the firstend stop (safe end position) or the second position in case of a failed switching device.An advantage of this embodiment is that an improved and more secure control of thedirect current motor is provided. An advantage of this embodiment is that an improvedcontrol of the electrical circuit is provided, which efficiently controls the direct currentmotor such that the direct current motor does not get stuck in an unsafe position, or atleast the risk of having the direct current motor getting stuck in an unsafe position iseffectively reduced or minimized. lf both the first and second switching devices are inthe closed position while the third switching device is in the open position, the electricalcircuit may be short-circuited and connected to ground, whereby no movement of thedirect current motor is provided. lf all three of the first, second and third switchingdevices are in the closed position, the electrical circuit may be short-circuited andconnected to the electric power source via the third switching device, whereby no movement of the direct current motor is provided.

According to an advantageous embodiment of the method according to the first aspect,the method comprises: ll while the first switching device is controlled to remain in the open position,while the second switching device is controlled to remain in the open position, andwhile the third switching device is controlled to switch from the open position to theclosed position, monitoring any movement of the direct current motor; and if a movement of the direct current motor is registered, determining that one ofthe following group of situations is valid: o The second switching device is stuck in the closed position; ando The first switching device is stuck in the closed position.

An advantage of this embodiment is that a faulty or failed second switching device,which is stuck in the closed position, can be diagnosed while ensuring that the directcurrent motor can be operated to the first end stop (safe end position) or the secondposition in case of a failed second switching device. An advantage of this embodimentis that an improved and more secure control of the direct current motor is provided. Anadvantage of this embodiment is that an improved control of the electrical circuit isprovided, which efficiently controls the direct current motor such that the direct currentmotor does not get stuck in an unsafe position, or at least the risk of having the direct current motor getting stuck in an unsafe position is effectively reduced or minimized.

According to a further advantageous embodiment of the method according to the firstaspect, the method comprises: when the third switching device has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position, whilethe first switching device is controlled to remain in the open position, and while thesecond switching device is controlled to switch from the open position to the closedposition, monitoring any movement of the direct current motor; and if a non-movement of the direct current motor (i.e. the direct current motor doesnot move) is registered, determining that one or more of the following group ofsituations is/are valid: o The third switching device is stuck in the open position;o The second switching device is stuck in the open position; and o The first switching device is stuck in the closed position. 12 The risk that one or more of the above-mentioned group of situations is/are valid isminimal thanks to the innovative embodiments of the method according to the firstaspect. However, if one or more of the above-mentioned group of situations is/arevalid, the direct current motor will remain at the second end stop (unsafe end position)or at the first position. An advantage of this embodiment is that one or more faulty orfailed switching devices, can be diagnosed.

According to a second aspect of the invention, the above mentioned and other objectsare achieved with a computer program comprising instructions which, when theprogram is executed by a computer, cause the computer to carry out the methodaccording to any one of the embodiments disclosed above or below. The advantagesof the computer program according to the second aspect correspond to the above- orbelow-mentioned advantages of the method according to the first aspect and its embodiments.

According to a third aspect of the invention, the above mentioned and other objectsare achieved with a computer-readable medium comprising instructions which, whenthe instructions are executed by a computer, cause the computer to carry out themethod according to any one of the embodiments disclosed above or below. Theadvantages of the computer-readable medium according to the third aspectcorrespond to the above- or below-mentioned advantages of the method according to the first aspect and its embodiments.

According to an aspect of the present invention, the above-mentioned computerprogram and computer-readable medium are configured to implement the method and its embodiments described herein.

According to a fourth aspect of the invention, the above mentioned and other objectsare achieved with a control arrangement for controlling an electrical circuit, theelectrical circuit being configured to control a direct current motor, the direct currentmotor being operable between a first end stop and a second end stop, the electrical circuit comprising 13 an electrically operable first switching device switchable between an openposition and a closed position, an electrically operable second switching device switchable between an openposition and a closed position, and an electrically operable third switching device switchable between an openposition and a closed position, wherein in the closed position the first switching device is configured to providea first connection of the direct current motor to an electric power source to operate thedirect current motor in a first direction toward the second end stop, wherein in the open position the first switching device is configured to beconnected to ground, wherein in the closed position the second switching device is configured toprovide a second connection of the direct current motor to the electric power source tooperate the direct current motor in a second direction toward the first end stop, wherein in the open position the second switching device is configured to beconnected to ground, and wherein in the closed position the third switching device is configured toprovide a third connection between the electric power source and the first connectionand between the electric power source and the second connection, wherein the control arrangement is configured to: while the second switching device is controlled to remain in the open positionand the third switching device is controlled to remain in the open position, control thefirst switching device to switch from the open position to the closed position, and when the first switching device has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position whilethe second switching device is controlled to remain in the open position, control thethird switching device to switch from the open position to the closed position in orderto operate the direct current motor in the first direction toward the second end stop.

The advantages of the control arrangement according to the fourth aspect correspondto the above or below-mentioned advantages of the method according to the firstaspect and its embodiments. 14 lt will be appreciated that all the embodiments described for the method aspects of theinvention are applicable also to the control arrangement aspects of the invention. Thus,all embodiments described for the method aspects of the invention may be performedby the control arrangement, which may include a control unit or a control device. Asmentioned above, the control arrangement and its embodiments have advantagescorresponding to the advantages mentioned above for the fire protection apparatusand its embodiments.

According to a fifth aspect of the invention, the above mentioned and other objects areachieved with an electrical circuit for controlling a direct current motor, the direct currentmotor being operable between a first end stop and a second end stop, the electricalcircuit comprising an electrically operable first switching device configured to switch between anopen position and a closed position, an electrically operable second switching device configured to switch betweenan open position and a closed position, and an electrically operable third switching device configured to switch between anopen position and a closed position, wherein in the closed position the first switching device is configured to providea first connection of the direct current motor to an electric power source to operate thedirect current motor in a first direction toward the second end stop, wherein in the open position the first switching device is configured to beconnected to ground, wherein in the closed position the second switching device is configured toprovide a second connection of the direct current motor to the electric power source tooperate the direct current motor in a second direction toward the first end stop, wherein in the open position the second switching device is configured to beconnected to ground, wherein in the closed position the third switching device is configured toprovide a third connection between the electric power source and the first connectionand between the electric power source and the second connection, and wherein the electrical circuit comprises a control arrangement according to any one of the embodiments disclosed above or below.

The advantages of the electrical circuit according to the fifth aspect correspond to theabove or below-mentioned advantages of the method according to the first aspect andits embodiments.

According to a sixth aspect of the invention, the above mentioned and other objectsare achieved with a direct current motor unit comprising a direct current motor and an electrical circuit according to any one of the embodiments disclosed above or below.

The advantages of the direct current motor unit according to the sixth aspectcorrespond to the above or below-mentioned advantages of the method according tothe first aspect and its embodiments.

According to a seventh aspect of the invention, the above mentioned and other objectsare achieved with a vehicle comprising one or more of the group of:o a control arrangement according to any one of the embodimentsdisclosed above or below;o an electrical circuit according to any one of the embodiments disclosedabove or below; ando a direct current motor unit according to any one of the embodiments disclosed above or below.

The vehicle may for example be a bus, a tractor vehicle, a truck or a car. The vehicle may have wheels.

According to an advantageous embodiment of the vehicle according to the seventhaspect, the vehicle comprises a pantograph operable by the direct current motor. Thevehicle may comprise a roof, wherein the pantograph is mounted to the roof.

The above-mentioned features and embodiments of the method, the computerprogram, the computer-readable medium, the control arrangement, the electrical 16 circuit, the direct current motor unit and the vehicle, respectively, may be combined invarious possible ways providing further advantageous embodiments.

Further advantageous embodiments of the method, the computer program, thecomputer-readable medium, the control arrangement, the electrical circuit, the directcurrent motor unit and the vehicle according to the present invention and furtheradvantages with the embodiments of the present invention emerge from the detaileddescription of embodiments.

Brief Description of the DrawingsEmbodiments of the invention will now be illustrated, for exemplary purposes, in moredetail by way of embodiments and with reference to the enclosed drawings, where similar references are used for similar parts, in which: Figure 1 is a schematic view illustrating an embodiment of the vehicle according tothe seventh aspect of the invention, in which embodiments of the presentinvention may be implemented; Figure 2 is a schematic side view of the vehicle of figure 1; Figure 3 is a schematic side view of the vehicle of figure 1; Figure 4 is a schematic diagram illustrating an embodiment of the controlarrangement according to the fourth aspect, an embodiment of theelectrical circuit according to the fifth aspect and an embodiment of thedirect current motor unit according to the sixth aspect; Figure 5 is a schematic diagram illustrating the operation of the direct current motorunit according to the sixth aspect; Figure6 is a flow chart illustrating aspects of an embodiment of the methodaccording to the first aspect of the invention; Figure 7 is a flow chart illustrating aspects of another embodiment of the methodaccording to the first aspect of the invention; and Figure 8 is a schematic view illustrating an embodiment of the control arrangement according to the fourth aspect of the invention, in which a methodaccording to any one of the herein described embodiments may be implemented. lO 17 Detailed Description With reference to figure 1, a vehicle 100 is schematically illustrated. The vehicle 100may be called a motor vehicle 100. The vehicle 100 may be a bus, a tractor vehicle ora truck, for example a heavy truck, which for example may be provided with a trailer.The vehicle 100 comprises a powertrain 102, which in the shown embodimentcomprises a combustion engine 104, for example an internal combustion engine oranother combustion engine, which in a conventional manner, via a first output shaft106 and usually via a flywheel, is connected to a gearbox 108 via a clutch 110. lngeneral, the combustion engine 104 comprises cylinders. ln addition to the powertrain102 comprising a combustion engine 104, the vehicle 100 may include one or moreelectrical machines for driving drive wheels 114, 116, 118, 120 of the vehicle 100 and may thus for example be a so-called hybrid vehicle.

The electrical machines may be provided with electric power from an electrical energyunit 121 which may be included in the vehicle 100. ln some embodiments, the electricalenergy unit 121 may for example include one or more electric battery units 123. Thus,the electrical energy unit 121 may be configured to power, i.e. to provide electric powerto, the electrical machines. Each of the electric battery units 123 may be configured topower, i.e. to provide electric power to, the electrical machines. The electric batteryunit 123 may be a rechargeable electric battery unit 123. instead of the powertrain 102comprising a combustion engine 104, the vehicle 100 may include only electricalmachines for driving the drive wheels 114, 116, 118, 120 of the vehicle 100, whereby the vehicle 100 may be a pure electrical vehicle.

The combustion engine 104 is controlled by the engine's control system via an enginecontrol device 112. Likewise, the clutch 110 and the gearbox 108 may be controlled bythe engine's control system, with the help of one or more control devices (not shown).The engine control device 112 and/or another control device may thus be configuredto control the combustion engine 104, the clutch 110, the gearbox 108, and/or anyother units/devices/entities of the vehicle 100. However, in figure 1, only a few of theunits/devices/entities of the vehicle 100 are illustrated. lO 18 Naturally, the powertrain 102 of the vehicle 100 may be of a different type, such as atype with a conventional automatic gearbox, a type with a hybrid driveline etc. Asmentioned above, the powertrain 102 may include one or more electrical machines fordriving the drive wheels 114, 116, 118, 120 of the vehicle 100, implementing a so-called hybrid drive. ln the shown embodiment, the vehicle 100 comprises a plurality ofwheels 114, 116, 118, 120. ln the shown embodiment, the vehicle 100 has four wheels114, 116, 118, 120, but may have more wheels. The electrical machine may bearranged essentially anywhere, as long as torque is provided to one or more of thewheels 114, 116, 118, 120, for example adjacent to one or more of the wheels 114,116, 118, 120, or along a propeller shaft 122 of the vehicle 100, for example betweenthe gearbox 108 and the clutch 110, as is understood by a skilled person.

The vehicle 100 may comprise a propeller shaft 122 from the gearbox 108 which drivestwo of the wheels 114, 116 via a central gear 124, for example a conventionaldifferential, and two drive shafts 126, 128 of the vehicle 100. The two drive shafts 126,128 are connected to the central gear 124. lf the vehicle 100 has a powertrain 102including a combustion engine 104, the vehicle 100 may comprise a fuel tank 129coupled to the combustion engine 104, and the combustion engine 104 may beprovided with fuel from the fuel tank 129.

The vehicle 100 may comprise an exhaust gas after-treatment system 130, which alsomay be called an exhaust gas purification system, for treatment/purification of theexhaust gas/emissions resulting from the combustion in the combustion chamber ofthe combustion engine 104. The exhaust gas after-treatment system 130 may becontrolled by an exhaust gas after-treatment control device 132, which maycommunicate with the engine control device 112 or another device of the engine'scontrol system.

With reference to figure 1, the vehicle 100 may comprise a control arrangement 150for controlling an electrical circuit 202 (see figure 4), wherein the electrical circuit 202is configured to control or operate a direct current motor 185 (see figures 2 and 3). Thecontrol arrangement 150 is disclosed in further detail herein below. lO 19 With reference to figure 2, the vehicle 100, which may be a bus, may include one ormore vehicle doors 160, 162 for entering or exiting the vehicle 100. The vehicle 100may include a chassis unit 167 including a floor 164. As mentioned above in connectionwith figure 1, the vehicle 100 may include a plurality of wheels 114, 116, 118, 120, forexample four or more wheels 114, 116, 118, 120 (only two wheels 114, 118 are shownin figure 2).

With reference to figure 2, the chassis unit 167 may include the electrical energy unit121, for example the electric battery unit 123, which may be located under floor 164,on the floor 164, at least partly in the floor 164, or completely in the floor 164 of thechassis unit 167. For example, the electrical energy unit 121 may be mounted orattached to an underside 180 of the floor 164 of the chassis unit 167. The electricalenergy unit 121 may be attached or mounted to the floor 164 in various possible ways,for example by means of various possible members or means of attachment, forexample brackets or bolts etc. Naturally, the electrical energy unit 121 may be locatedelsewhere in the vehicle 100, and the vehicle 100 may be of a different kind than whatis shown in figures 2 and 3. The electrical energy unit 121 may be located in the front(front portion) of the vehicle 100 or in the back (back portion) of the vehicle 100. lnsteadof being located in the floor region, the electrical energy unit 121 may be locatedadjacent to a roof 182 of the vehicle 100, for example on top of the roof 182 or underthe roof 182. When the vehicle 100 includes a roof unit including the roof 182, the roofunit may include the electrical energy unit 121. Other locations for the electrical energyunit 121 are possible. Naturally, combinations of the above-mentioned locations of theelectrical energy unit 121 are possible. For example, the electric battery units 123 ofthe electrical energy unit 121 may be located at a plurality of locations of the vehicle 100, for example the plurality of locations mentioned above.

With reference to figure 2, the vehicle 100 may include a roof 182. The vehicle 100may include a pantograph 184, which may be mounted to the roof 182 and may beoperable by a direct current (DC) motor 185, which is also marked with M in the figures.ln general, a pantograph 184 is an apparatus which comprises an electrical contact186, or an electrical trolley, and a collapsible and adjustable frame 188, wherein theelectrical contact 186 is carried by the collapsible and adjustable frame 188. The lO electrical contact 186 of the pantograph 184 is configured to make contact with anoverhead contact to carry electric current from the overhead contact to the vehicle 100via the electrical contact 186 of the pantograph 184, for example to the electric batteryunit 121 of the vehicle 100 in order to charge the electric battery unit 121. An electricaltrolley is a device that carries electric current from an overhead wire to an electrically driven vehicle.

With reference to figures 2 and 3, the pantograph 184 and the frame 188 are movablebetween a retracted, or folded, position and an extended position. ln the retractedposition of the frame 188 and the pantograph 184, the electrical contact 186 is in aresting or retracted position and adjacent to the roof 182, for example a lower position(first end position) in relation to the chassis unit 167. ln the extended position of theframe 188 and the pantograph 184, the electrical contact 186 is in an active orextended position and configured to be in contact with the overhead contact or beready to connect with the overhead contact. The extended position of the of the frame188 and the pantograph 184 may be an upper position (second end position) in relationto the chassis unit 167. ln the upper position (second position) the electrical contact186 is further away from the roof 182 and the chassis unit 167 compared to theretracted position of the electrical contact 186. ln figure 2, the pantograph 184 and/or the frame 188 are/is in the retracted position(first end position), and the electrical contact 186 is in the retracted lower position. Theretracted position (first end position) of the pantograph 184, the frame 188 and/or theelectrical contact 186 may be considered to be a safe position (first end position), whenthe vehicle 100 can be driven and move without risking that the pantograph 184 hitsany stationary overhead structures. When the pantograph 184 and/or the frame 188are/is in the retracted position (first end position), the direct current motor 185, whichcontrols the pantograph 184, may be considered to be at a first end stop S1, which isa safe end position. ln figure 3, the pantograph 184 and/or the frame 188 are/is in the extended position(second end position), and the electrical contact 186 is in the extended upper position.The extended position (second end position) of the pantograph 184, the frame 188 lO 21 and/or the electrical contact 186 may be considered to be an unsafe position (secondend position), when the pantograph 184 of the vehicle 100 may risk hitting stationaryoverhead structures if the vehicle 100 is driven and moves. When the pantograph 184and/or the frame 188 are/is in the extended position (second end position), the directcurrent motor 185 may be considered to be at a second end stop S2, which is anunsafe end position. Thus, retracted position (first end position) of the pantograph 184,which represents the safe end position, is preferred over the extended position (secondend position) pantograph 184, which represents the unsafe end position, if thepantograph 184 gets stuck. Thus, the first end stop S1 (safe end position) of the directcurrent motor 185, which represents the safe end position, is preferred over the secondend stop S2 (unsafe end position) of the direct current motor 185, which representsthe unsafe end position, if the direct current motor 185 gets stuck, for example becauseof switching device failure.

With reference to figure 4, an embodiment of the control arrangement 150 accordingto the fourth aspect of the present invention, an embodiment of the electrical circuit202 according to the fifth aspect of the present invention and an embodiment of thedirect current (DC) motor unit 204 according to the sixth aspect of the present inventionare schematically illustrated.

With reference to figure 4, the electrical circuit 202 is configured to control, or operate,a direct current (DC) motor 185, which is also marked with M in figure 4. The directcurrent motor 185 is an electric motor. With reference to figure 5, the direct currentmotor 185 is operable, i.e. configured to be operated, between a first end stop S1, ora first end position, and a second end stop S2, or a second end position. The electricalcircuit 202 may thus be configured to control or operate the direct current motor 185between the first end stop S1 and the second end stop S2. With reference to figure 2and 3, the first end stop S1 may be a safe end position while the second end stop S2may be an unsafe end position. Direct current motors of various known types areknown to the skilled person and are thus not described in further detail herein. Theelectrical circuit 202 may correspond to an electrical network. lO 22 With reference to figure 4, the electrical circuit 202 includes an electrically operablefirst switching device R1 configured to switch between an open position and a closedposition. The electrical circuit 202 includes an electrically operable second switchingdevice R2 configured to switch between an open position and a closed position. Theelectrical circuit 202 includes an electrically operable third switching device Rsconfigured to switch between an open position and a closed position. The thirdswitching device Rs may be defined as, or called, an electric power supply switchingdevice or a safety switching device. The fact that each switching device R1, R2, Rs iselectrically operable means that the switch R1, R2, Rs is configured to be electricallyoperated. When each of the first, second and third switching devices R1, R2, Rs is inthe closed position, each of the first, second and third switching devices R1, R2, Rs isconfigured to conduct an electric current or allow an electric current to pass. ln figure4, each of the first, second and third switching devices R1, R2, Rs is illustrated in theopen position while the closed positions of the first, second and third switching devicesR1, R2, Rs are illustrated by dotted lines in figure 4. When being in the open position,the third switching device Rs may be connected, or configured to be connected, toground 206, i.e. electrically connected to ground 206, i.e. electrical ground 206 (orearth). ln alternative embodiments, the third switching device Rs may not beconnected, or may not be configured to be connected, to ground 206 when being inthe open position. The open position of each switching device R1, R2, Rs may be anopen position of a plurality of open positions. The closed position of each switching device R1, R2, Rs may be a closed position of a plurality of closed positions. ln some embodiments, each of the first, second and third switching devices R1, R2,Rs may comprise a plurality of switches, or switching units. The plurality of switches,or switching units, may be connected, or connectable, in parallel, i.e. electricallyconnected, or electrically connectable, in parallel. Each switch of the plurality ofswitches may be called an electrical switch. Each switching unit of the plurality ofswitching units may be called an electrical switching unit.

With reference to figure 4, the electrical circuit 202 may include a control arrangement150 for controlling the electrical circuit 202, for example according to any one of theembodiments of the control arrangement 150 mentioned above or below. Each of the lO 23 first, second and third switching devices R1, R2, Rs may be controllable by the controlarrangement 150 disclosed in further detail hereinbelow. The control arrangement 150may be connected to each of the first, second and third switching devices R1, R2, Rsin order to transmit or send operation signals for contro||ing each of the first, secondand third switching devices R1, R2, Rs to switch to the open position or the closedposition or remain in the open position or closed position. Each first, second and thirdswitching devices R1, R2, Rs may be controlled to remain in an open or closed positionsimply by sending no control signal to the respective switching device R1, R2, Rs ofthe first, second and third switching devices R1, R2, Rs. The signal connections, forexample including signal lines, between the control arrangement 150 and the first,second and third switching devices R1, R2, Rs are illustrated by dotted lines 208, 210,212. Each of the first, second and third switching devices R1, R2, Rs may comprise ormay be called a relay. ln alternative embodiments, the control arrangement 150 may be wirelessly connected to the first, second and third switching devices R1, R2, Rs.

The electrical circuit 202 may include one or more electrical conductors 214 carryingan electric current. The electrical circuit 202 may include one or more additionalelectrical or electronic components in addition to what is shown in figure 4 anddisclosed in this disclosure.

With reference to figure 4, in the closed position, i.e. in the closed position of the firstswitching device R1 (or when the first switching device R1 is in the closed position),the first switching device R1 is configured to provide a first connection 216 of the directcurrent motor 185 to an electric power source 218 to operate the direct current motor185 in a first direction toward the second end stop S2 (see figure 5). The firstconnection 216 may be called a first electrical connection. The closed position of thefirst switching device R1, or the closed first switching device R1, which in the shownembodiment is included in the first connection 216, is illustrated by a dotted line infigure 4. The first connection 216 may be called a first electrical path. The firstconnection 216, or the first electrical path, may include the first switching device R1,especially when the first switching device R1 is in the closed position. ln the openposition, i.e. in the open position of the first switching device R1 (or when the firstswitching device R1 is in the open position), the first switching device R1 is connected, 24 or configured to be connected, i.e. electrically connected, to ground 206, i.e. electricalground 206 (or earth). lt may be stated that the first switching device R1 is configuredto provide a connection to ground 206, for example for the electrical circuit 202, whenbeing in the open position.

The electric power source 218 may correspond to an electrical energy source. Theelectric power source 218 may correspond to the electrical energy unit 121 included ina vehicle 100 as disclosed in connection with figures 1 to 3. The electric power source218 may for example include one or more electric battery units 123, for example as illustrated in connection with figures 1 to 3.

With reference to figure 4, in the closed position, i.e. in the closed position of thesecond switching device R2 (or when the second switching device R2 is in the closedposition), the second switching device R2 is configured to provide a second connection220 of the direct current motor 185 to the electric power source 218 to operate thedirect current motor 185 in a second direction toward the first end stop S1 (see figure5). The second connection 220 may be called a second electrical connection. Theclosed position of the second switching device R2, or the closed second switchingdevice R2, which in the shown embodiment is included in the second connection 220,is illustrated by a dotted line in figure 4. The second connection 220 may be called asecond electrical path. The second connection 220, or the second electrical path, mayinclude the second switching device R2, especially when the second switching deviceR2 is in the closed position. ln the open position, i.e. in the open position of the secondswitching device R2 (or when the second switching device R2 is in the open position),the second switching device R2 is connected, or configured to be connected, i.e.electrically connected, to ground 206, i.e. electrical ground 206 (or earth). lt may bestated that the second switching device R2 is configured to provide a connection toground 206, for example for the electrical circuit 202, when being in the open position.

With reference to figure 4, in the closed position, i.e. the closed position of the thirdswitching device Rs (or when the third switching device Rs is in the closed position),the third switching device Rs is configured to provide a third connection 222 betweenthe electric power source 218 and the first connection 216 and between the electric power source 218 and the second connection 220. Thus, the third connection 222 isprovided between the electric power source 218 and the first connection 216, and atthe same time, the third connection 222 is provided between the electric power source218 and the second connection 220. The third connection 222 may be called a thirdelectrical connection. The closed position of the third switching device Rs, or the closedthird switching device Rs, which in the shown embodiment is included in the thirdconnection 222, is illustrated by a dotted line in figure 4. The third connection 222 maybe called a third electrical path. The third connection 222, or the third electrical path,may include the third switching device Rs, especially when the third switching deviceRs is in the closed position. ln the closed position the third switching device Rs maybe configured to electrically connect the electric power source 218 to the first and the second connections 216, 220.

The third switching device Rs may be electrically connected or connectable to theelectric power source 218 via a fuse 224. ln alternative embodiments, there mayinstead, or in addition thereto, be one or more fuses between the first switching deviceR1 and the second switching device R2, between the first switching device R1 and thethird switching device Rs and/or between the second switching device R2 and the thirdswitching device Rs. However, in some embodiments, the fuse 224 or fuses may be excluded, providing an electrical circuit without any fuse.

The electric power source 218 may be provided in one single unit providing electricpower to the first, second and third connections 216, 220, 222, for example asillustrated in figure 4. ln alternative embodiments, the power source may be providedin a plurality of separate units, for example, three units, providing electric power thefirst, second and third connections 216, 220, 222. Thus, a first unit of the electric powersource may provide electric power to the first connection 216, a second unit of theelectric power source may provide electric power to the second connection 220, and athird unit of the electric power source may provide electric power to the third connection222.

With reference to figure 4, the control arrangement 150, which is configured to controlan electrical circuit 202, for example according to any one of the embodiments 26 mentioned above or below, is configured to control or operate a direct current motor185, for example according to any one of the embodiments mentioned above or below.As mentioned above, the direct current motor 185 is operable, or movable, between afirst end stop S1 (see figure 5) and a second end stop S2 (see figure 5).

According to an embodiment of the control arrangement 150, the control arrangement150 is configured to: while the second switching device R2 is controlled to remain in the openposition and while the third switching device Rs is controlled to remain in the openposition, control the first switching device R1 to switch from the open position to theclosed position, and when the first switching device R1 has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position whilethe second switching device R2 is controlled to remain in the open position, control thethird switching device Rs to switch from the open position to the closed position in orderto operate the direct current motor 185 in the first direction toward the second end stopS2 (see figure 5).

Further, all embodiments described for the method aspects of the present invention inthis disclosure may be performed by the control arrangement 150, for example themethod steps disclosed hereinbelow.

With reference to figures 2 to 4, embodiments of the direct current motor unit 204according to the sixth aspect comprise a direct current motor 185, for exampleaccording to any one of the embodiments of the direct current motor 185 mentionedabove or below. Further, with reference to figure 4, embodiments of the direct currentmotor unit 204 comprise an electrical circuit 202, for example according to any one ofthe embodiments of the electrical circuit 202 mentioned above or below.

With reference to figure 5, the operation of the direct current motor unit 204 as well asthe operation of the direct current motor 185 are schematically illustrated in aschematic diagram, for example to illustrate a plurality of positions, or states, of thedirect current motor 185 and aspects of the electrical circuit 202 and the control lO 27 arrangement 150. The direct current motor 185 is operable, for example movable,between a first end stop S1 and a second end stop S2 by controlling the switchingdevices R1, R2, Rs of the electrical circuit 202. The direct current motor unit 204 or thedirect current motor 185 may include the first end stop S1 and the second end stop S2.Figure 5 is a very schematic view and does not necessarily represent that themovement or rotation of the direct current motor 185 is restricted to less than one turn(360 degrees). Certainly, the direct current motor 185 may rotate several turns beforereaching the firs end stop S1 or the second end stop S2. ln general, the second end stop S2 may be an unsafe end stop, or an unsafe endposition. For example, when the direct current motor 185 has been operated to thesecond end stop S2, the pantograph 184 shown in figure 3, to which the direct currentmotor 185 may be connected to operate the pantograph 184, has been moved to andis in the extended position shown in figure 3, the extended position of the pantograph184 representing an unsafe position. ln general, the first end stop S1 may be a safeend stop, or a safe end position or resting position. For example, when the directcurrent motor 185 has been operated to the first end stop S1, the pantograph 184shown in figure 2 has been moved to and is in the retracted position shown in figure 2,the retracted position of the pantograph 184 representing a safe position.

With reference to figure 5, the direct current motor unit 204 or the direct current motor185 may include a first end stop sensor 226 configured to detect that the direct currentmotor 185 has been operated to and has reached the first end stop S1. The directcurrent motor unit 204 or the direct current motor 185 may include a second end stopsensor 228 configured to detect that the direct current motor 185 has been operatedto and has reached the second end stop S2. Various known sensors, for exampleposition or contact sensors, which may be used as end stop sensor 226, 228, areknown to the skilled person and thus not disclosed in further detail.

With reference to figure 5, the direct current motor 185 may be configured to beoperated, or moved, to a first position S2a. ln the shown embodiment, the first positionS2a is located somewhere between the first end stop S1 and the second end stop S2.The first position S2a may be a desired first position, to which the direct current motor 28 185 may be operated. The first position S2a may represent an unsafe position. ln someembodiments, the first position S2a may correspond to the second end stop S2 (or thesecond end position). The direct current motor 185 may be configured to be operated,or moved, to a second position S1a. ln the shown embodiment, the second positionS1a is located somewhere between the first end stop S1 and the second end stop S2.More specifically, in the shown embodiment, the second position S1a is locatedsomewhere between the first end stop S1 and the first position S2a. The secondposition S1a may be a desired second position, to which the direct current motor 185may be operated. The second position S1a may represent a safe position. ln someembodiments, the second position S1a may correspond to the first end stop S1 (or thefirst end position).

With reference to figure 5, the direct current motor unit 204 or the direct current motor185 may include a first position sensor 230 configured to detect or determine theposition of the direct current motor 185 between the first end stop S1 and the secondend stop S2, for example between the first end stop S1 and the first position S2a. Forexample, the first position sensor 230 may be configured to determine or detect thatthe direct current motor 185 has been operated to the second position S1 a. The directcurrent motor unit 204 or the direct current motor 185 may include a second positionsensor 232 configured to detect or determine the position of the direct current motor185 between the first end stop S1 and the second end stop S2, for example betweenthe second end stop S2 and the second position S1 a. For example, the second positionsensor 232 may be configured to determine or detect that the direct current motor 185has been operated to the first position S2a. However, in alternative embodiments, thedirect current motor unit 204 or the direct current motor 185 may include only oneposition sensor configured to determine or detect the position of the direct currentmotor 185 between the first end stop S1 and the second end stop S2, for exampleconfigured to determine or detect that the direct current motor 185 has been operatedto the first position S2a or the second position S1a. Various known sensors, forexample position or contact sensors, which may be used as position sensor 228, 230,are known to the skilled person and thus not disclosed in further detail. 29 With reference to figure 5, one or more of the first and second position sensors 230,232 and the first and second end stops sensors 226, 228 may be configured to detectany movement, and/or optionally any non-movement, of the direct current motor 185.With reference to figure 4, the control arrangement 150 may be connected to one ormore of the first and second position sensors 230, 232 and the first and second endstops sensors 226, 228. The signal connection or connections, for example includingsignal lines, between the control arrangement 150 and one or more of the first andsecond position sensors 230, 232 and the first and second end stops sensors 226, 228are illustrated by a dotted line 233. ln alternative embodiments, the controlarrangement 150 may be wirelessly connected to one or more of the first and secondposition sensors 230, 232 and the first and second end stops sensors 226, 228. ln alternative embodiments, the direct current motor 185 may be mechanicallyconnected or connectable to any kind of mechanical power transfer system, forexample including an actuator, such as a linear actuator (for example a linear gear rod)or a snail gear. For example, the mechanical power transfer system may in turn bemechanically connected or connectable to the pantograph 184 illustrated in figures 2and 3 to operate the pantograph 184. Then, the power transfer system may includethe end stop sensors 226, 228, and optionally in addition thereto the first positionsensor 230 and/or second position sensor 232. ln alternative embodiments, anactuator, for example a linear actuator (such as a linear gear rod), mechanicallyconnected or connectable to the direct current motor 185 and configured to becontrolled or operated by the direct current motor 185 may include the end stopsensors 226, 228. ln addition, the actuator may optionally include the first positionsensor 230 and/or second position sensor 232. For example, the actuator may in turnbe mechanically connected or connectable to the pantograph 184 illustrated in figures 2 and 3 and configured to operate the pantograph 184.

With reference to figure 1 to 4, embodiments of the vehicle 100 according to theseventh aspect of the invention may include one or more of the group of: a controlarrangement 150 according to any one of the embodiments disclosed above or below;an electrical circuit 202 according to any one of the embodiments disclosed above or below; and a direct current motor unit 204 according to any one of the embodimentsdisclosed above or below.

With reference to figure 6, aspects of a first embodiment of the method for contro||ingan electrical circuit 202 according to the first aspect are illustrated. With reference tofigure 7, aspects of a second embodiment of the method for contro||ing an electricalcircuit 202 according to the first aspect are illustrated. The electrical circuit 202 isconfigured to control or operate the direct current motor 185 between the first end stopS1 and the second end stop S2. The electrical circuit 202 may correspond to any oneof the embodiments disclosed above or below. The direct current motor 185 maycorrespond to any one of the embodiments disclosed above or below.

As mentioned above, the inventors of the present invention have concluded that thefollowing unwanted situations should be avoided, since they may lead to that the directcurrent motor 185 gets stuck at the second end stop S2, which may be an unsafeposition as disclosed above, because of or in case of a switching device failure, i.e. ifone or more of the switching devices R1, R2, Rs fails/fail:o The third switching device Rs is stuck in the open position when the directcurrent motor 185 is away from the first end stop S1 or the second position S1 a;o The first switching device R1 is stuck in the closed position; and o The second switching device R2 is stuck in the open position.

Further, in view of the above-mentioned unwanted situations, the inventors of thepresent invention have concluded that in order to avoid the above-mentionedunwanted situations, the following switching rules for the switching devices R1, R2, Rsshould apply when considering the primarily two types of mechanical failures: “welding”and “arcing”, which have been described in further detail in the introductory part of thisdisclosure:o The third switching device Rs should never open the circuit first, when the directcurrent motor 185 is operated in the first direction toward, or to, the second endstop S2 (unsafe end position) or the first position S2a; 31 The first switching device R1 should never close the circuit last, when the directcurrent motor 185 is operated in the first direction toward, or to, the second endstop S2 (unsafe end position); and The second switching device R2 should never open the circuit first, when thedirect current motor 185 is operated in the second direction toward, or to, thefirst end stop S1 (safe end position).

With reference to figure 6, the first embodiment of the method, which will result in an operation of the direct current motor 185 in the first direction, for example from the first end stop S1 (safe end position), toward, or to, the second end stop S2 (unsafe end position), includes the following steps, which may be considered to be included in a first sequence: While, or when, the second switching device R2 is controlled to remain in theopen position and the third switching device Rs is controlled to remain in theopen position, controlling 301 the first switching device R1 to switch from theopen position to the closed position. ln this step, the first switching device R1closes an open circuit, i.e. the circuit remains open after closing first switchingdevice R1, whereby there is no load, and the first switching device R1 isexposed to minimal wear; While the second switching device R2 is controlled to remain in the openposition, while the third switching device Rs is controlled to remain in the openposition, and while the first switching device R1 is, or has been, controlled toswitch from the open position to the closed position, monitoring 302, ordetecting, any movement of the direct current motor 185, for example if thedirect current motor 185 leaves the first end stop S1; lfa movement of the direct current motor 185, for example in relation to a vehicle100, the chassis unit 167 of the vehicle 100, and/or the roof 182 of the vehicle100, is registered, determining 303 that the third switching device Rs is stuck inthe closed position. The steps 302 and 303 are part of a diagnosis procedureand may be excluded if the diagnosis of failed switching devices is of no interest.lf the third switching device Rs is stuck in the closed position, the performanceof the steps of the method can continue until the direct current motor 185 is back 32 at the first end stop S1 (safe end position), and then the direct current motor185 should not be operated again until the failed switching device Rs has beenreplaced, or possibly repaired. The monitoring 302 and detection of anymovement of the direct current motor 185 may be performed by means of oneor more of the first and second position sensors 230, 232 and the first andsecond end stops sensors 226, 228 mentioned above;When the first switching device R1 has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed positionwhile the second switching device R2 is controlled to remain in the openposition, controlling 304 the third switching device Rs to switch from the openposition to the closed position in order to operate the direct current motor 185in the first direction toward the second end stop S2. When closing the thirdswitching device Rs in this step, there is a risk of welding. lf the third switchingdevice Rs welds, this will be registered or noted next time the direct currentmotor 185 is operated toward the second end stop S2;When the first switching device R1 has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position,while the second switching device R2 is controlled to remain in the openposition, and while the third switching device Rs is, or has been, controlled toswitch from the open position to the closed position, monitoring 305, ordetecting, any movement of the direct current motor 185;lf a non-movement, or no movement, of the direct current motor 185 isregistered, for example that the direct current motor 185 remains at the first endstop S1, determining 306 that one or more of the following group of situationsis/are valid:I The third switching device Rs is stuck in the open position;I The first switching device R1 is stuck in the open position; andI The second switching device R2 is stuck in the closed position.

The monitoring 305 and detection of any movement of the direct current motor 185 may be performed by means of one or more of the first and second position sensors 230, 232 and the first and second end stops sensors 226, 228 mentioned above. The steps 305 and 306 are part of a diagnosis procedure 33 and may be excluded if the diagnosis of failed switching devices is of nointerest. As mentioned above, in general, if both the first and second switchingdevices R1, R2 are in the closed position while the third switching device Rsis in the open position, the electrical circuit 202 is short-circuited and connectedto ground 206, whereby no movement of the direct current motor 185 isprovided. ln general, if all three of the first, second and third switching devicesR1, R2, Rs are in the closed position, the electrical circuit 202 is short-circuitedand connected to the electric power source 218 via the third switching deviceRs, whereby no movement of the direct current motor 185 is provided; o When, and if, the direct current motor 185 has been operated to a desired firstposition S2a while the second switching device R2 is controlled to remain in theopen position and the third switching device Rs is controlled to remain in theclosed position, controlling 307 the first switching device R1 to switch from theclosed position to the open position in order to stop the operation or movementof the direct current motor 185. When opening the first switching device R1 inthis step, there is a risk of arcing. lf the first switching device R1 gets stuck inthe open position, the direct current motor 185 cannot be operated next time thedirect current motor 185 is to be operated toward the second end stop S2(unsafe end position). However, the direct current motor 185 can be operatedback to the first end stop S1 (safe end position); o When the first switching device R1 has been controlled to switch from the closedposition to the open position and is controlled to remain in the open positionwhile the second switching device R2 is controlled to remain in the openposition, controlling 308 the third switching device Rs to switch from the closedposition to the open position. ln this step, the third switching device Rs opensan already open circuit, whereby there is no load, and the third switching device Rs is exposed to minimal wear. lt should be noted that the step of controlling a switching device R1, R2, Rs to remainin an open or closed position, may be a passive step not involving any actual action.ln general, if the controlling of a switching device R1, R2, Rs to switch to the openposition or the closed position is unsuccessful, the switching device R1, R2, Rs in 34 question is stuck in the closed position or the open position, and a switching does not OCCUI”.

With reference to figure 7, the second embodiment of the method, which will result in an operation of the direct current motor 185 in the second direction, for example from the second end stop S2 (unsafe end position), toward, or to, the first end stop S1 (safe end position), includes the following steps, which may be considered to be included in While, or when, the first switching device R1 is controlled to remain in the openposition and the second switching device R2 is controlled to remain in the openposition, controlling 401 the third switching device Rs to switch from the openposition to the closed position. ln this step, the third switching device Rs closesan open circuit, i.e. the circuit remains open after closing the third switchingdevice Rs, whereby there is no load, and the third switching device Rs isexposed to minimal wear; While the first switching device R1 is controlled to remain in the open position,while the second switching device R2 is controlled to remain in the openposition, and while the third switching device Rs is, or has been, controlled toswitch from the open position to the closed position, monitoring 402 anymovement of the direct current motor 185, for example if the direct current motor185 leaves the second end stop S2; lf a movement of the direct current motor 185 is registered, determining 403 thatone of the following group of (two) situations is valid: The second switchingdevice R2 is stuck in the closed position; The first switching device R1 is stuckin the closed position. lf it is registered that the direct current motor 185 movesin the first direction toward the second end stop S2, then it can be determinedthat the first switching device R1 is stuck in the closed position. lf it is registeredthat the direct current motor 185 moves in the second direction toward the firstend stop S1, then it can be determined that the second switching device R2 isstuck in the closed position. The steps 402 and 403 are part of a diagnosisprocedure and may be excluded if the diagnosis of failed switching devices is ofno interest. lf the second switching device R2 is stuck in the closed position, the direct current motor 185 will continue to the first end stop S1 where the directcurrent motor 185 will be incapacitated until the failed switching device R2 hasbeen replaced, or possibly repaired. The monitoring 402 and detection of anymovement of the direct current motor 185 may be performed by means of oneor more of the first and second position sensors 230, 232 and the first andsecond end stops sensors 226, 228 mentioned above;When the third switching device Rs has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed positionwhile the first switching device R1 is controlled to remain in the open position,controlling 404 the second switching device R2 to switch from the open positionto the closed position in order to operate the direct current motor 185 in thesecond direction toward the first end stop S1. When closing the secondswitching device R2 in this step, there is a risk of welding. lf the secondswitching device R2 welds, the third switching device Rs will be able to stop thedirect current motor 185 at the first end stop S1, where the direct current motor185 will be incapacitated until the failed switching device R2 has been replaced,or possibly repaired;When the third switching device Rs has been controlled to switch from the openposition to the closed position and is controlled to remain in the closed position,while the first switching device R1 is controlled to remain in the open position,and while the second switching device R2 is, or has been, controlled to switchfrom the open position to the closed position, monitoring 405, or detecting, anymovement of the direct current motor 185;lf a non-movement of the direct current motor 185, for example that the directcurrent motor 185 remains at the second end stop S2, is registered, determining406 that one or more of the following group of situations is/are valid:I The third switching device Rs is stuck in the open position;I The second switching device R2 is stuck in the open position; andI The first switching device R1 is stuck in the closed position.

The monitoring 405 and detection of any movement of the direct current motor 185 may be performed by means of one or more of the first and second position sensors 230, 232 and the first and second end stops sensors 226, 228 36 mentioned above. The risk that one or more of the above-mention group ofsituations is/are valid is minimal thanks to the innovative embodiments of themethod according to the first aspect. However, if one or more of the above-mentioned group of situations is/are valid, the direct current motor 185 willremain at the second end stop S2 (unsafe end position) or at the first positionS2a. The steps 405 and 406 are part of a diagnosis procedure and may beexcluded if the diagnosis of failed switching devices is of no interest. o When, and if, the direct current motor 185 has been operated to a desiredsecond position S1a while the first switching device R1 is controlled to remainin the open position and the second switching device R2 is controlled to remainin the closed position, controlling 407 the third switching device Rs to switchfrom the closed position to the open position in order to stop the operation ofthe direct current motor 185. When opening the third switching device Rs in thisstep, there is a risk of arcing. lf the third switching device Rs gets stuck in theopen position, the direct current motor 185 will be incapacitated at the first endstop S1 until the failed switching device Rs has been replaced, or possiblyrepaired; o When the third switching device Rs has been controlled to switch from theclosed position to the open position and is controlled to remain in the openposition while the first switching device R1 is controlled to remain in the openposition, controlling 408 the second switching device R2 to switch from theclosed position to the open position. ln this step, the second switching deviceR2 opens an already open circuit, whereby there is no load, and the second switching device R2 is exposed to minimal wear.

The embodiments of the method of figures 6 and 7 may be combined to present aninnovative procedure including both the first sequence of figure 6 and the secondsequence of figure 7. When combined, the step 308 of figure 6 may continue (orproceed) to step 401 of figure 7 and/or the step 408 of figure 7 may continue (orproceed) to step 301 of figure 6. Thus, for example, the first and second sequences of figures 6 and 7 may be repeated several times, and may, for example, be repeated lO 37 until one or more switching devices R1, R2, Rs fails/fail and/or until one or more failedswitching devices R1, R2, Rs is/are detected or registered.

One or more additional steps may be added to the method without departing from thescope of the appended claims. One or more steps may be excluded from the methodwithout departing from the scope of the appended claims. For example, as mentionedabove, one or more of the step for diagnosis 302, 303, 305, 306, 402, 403, 405, 406may be excluded if diagnosis of failed switching devices R1, r2, Rs is of no interest.

With reference to figure 4, the shown control arrangement 150 may include a firstswitch control unit 234 for controlling the first switching device R1 to switch betweenthe open position and the closed position. The shown control arrangement 150 mayinclude a second switch control unit 236 for controlling the second switching device R2to switch between the open position and the closed position. The shown controlarrangement 150 may include a third switch control unit 238 for controlling the thirdswitching device Rs to switch between the open position and the closed position. lnalternative, embodiments, one or two switch control units may be configured to controlall three of the first, second and third switching devices R1, R2, Rs to switch betweenthe open position and the closed position.

With reference to figure 4, the shown control arrangement 150 may include amovement monitoring unit 240 for monitoring and/or detecting any movement and/ornon-movement of the direct current motor 185. The movement monitoring unit 240 maybe connected to one or more of the first and second position sensors 230, 232 and thefirst and second end stops sensors 226, 228. The movement monitoring unit 240 maybe configured to determine the position of the direct current motor 185 in view of signalsfrom one or more of the first and second position sensors 230, 232 and the first andsecond end stops sensors 226, 228.

With reference to figure 4, the shown control arrangement 150 may include a failuredetermination unit 242 for determining that one or more of the first, second and thirdswitching devices R1, R2, Rs is/are stuck in the open or closed position. The failuredetermination unit 242 may be connected to the movement monitoring unit 240. 38 Figure 8 shows in schematic representation an embodiment of the control arrangement150 according to the fourth aspect of the invention, which may include a control unit800, which may correspond to or may include one or more of the above-mentionedunits 234, 236, 238, 240, 242 of the control arrangement 150. The control unit 800 maycomprise a computing unit 801, which can be constituted by essentially any suitabletype of processor or microcomputer, for example a circuit for digital signal processing(Digital Signal Processor, DSP), or a circuit having a predetermined specific function(Application Specific Integrated Circuit, ASIC). The computing unit 801 is connected toa memory unit 802 arranged in the control unit 800. The memory unit 802 provides thecomputing unit 801 with, for example, the stored program code and/or the stored datawhich the computing unit 801 requires to be able to perform computations. Thecomputing unit 801 is also arranged to store partial or final results of computations in the memory unit 802. ln addition, the control unit 800 may be provided with devices 811, 812, 813, 814 forreceiving and transmitting input and output signals. These input and output signals cancontain waveforms, impulses, or other attributes which, by means of the devices 811,813 for the reception of input signals, can be detected as information and can beconverted into signals which can be processed by the computing unit 801. Thesesignals are then made available to the computing unit 801. The devices 812, 814 forthe transmission of output signals are arranged to convert signals received from thecomputing unit 801 in order to create output signals by, for example, modulating thesignals, which can be transmitted to other parts of and/or systems in the vehicle 100.

Each of the connections to the devices for receiving and transmitting input and outputsignals can be constituted by one or more of a cable; a data bus, such as a CAN bus(Controller Area Network bus), a MOST bus (Media Orientated Systems Transportbus), or some other bus configuration; or by a wireless connection.

Control systems in modern vehicles commonly comprise communication bus systemsconsisting of one or more communication buses for linking a plurality of electronic control units (ECU's), or controllers, and various components located on the vehicle. 39 Such a control system can comprise a large number of control units and/or controlarrangements and the responsibility for a specific function can be divided amongstmore than one control unit. Vehicles of the shown type thus often comprise significantlymore control units or control arrangements than are shown in figures 1 and 4, which iswell known to the person skilled in the art within this technical field. Alternatively or inaddition thereto, the embodiments of the present invention may be implemented whollyor partially in one or more other control units already present in the vehicle.

Here and in this document, units are often described as being provided for performingsteps of the method according to embodiments of the invention. This also includes thatthe units are designed to and/or configured to perform these method steps.

The units 234, 236, 238, 240, 242 of the control arrangement 150 are in figure 4illustrated as separate units. These units 234, 236, 238, 240, 242 may, however, belogically separated but physically implemented in the same unit, or can be both logicallyand physically arranged together. These units 234, 236, 238, 240, 242 may forexample correspond to groups of instructions, which can be in the form of programmingcode, that are input into, and are utilized by a processor/computing unit 801 (see figure8) when the units are active and/or are utilized for performing its method step.

The control arrangement 150, which may include one or more control units 800, e.g. adevice or a control device, according to embodiments of the present invention may bearranged to perform all of the method steps mentioned above, in the claims, and inconnection with the herein described embodiments. The control arrangement 150 isassociated with the above described advantages for each respective embodiment.

According to the second aspect of the invention, a computer program 803 (see figure8) is provided, comprising instructions which, when the program is executed by acomputer, cause the computer to carry out the method according to one or more of the embodiments disclosed above.

According to the third aspect of the invention, a computer-readable medium isprovided, comprising instructions which, when the instructions are executed by a computer, cause the computer to carry out the method according to one or more of theembodiments disclosed above.

The person skilled in the art will appreciate that the herein described embodiments ofthe method according to the first aspect may be implemented in a computer program,which, when it is executed in a computer, instructs the computer to execute themethod. The computer program is usually constituted by a computer program product803 stored on a non-transitory/non-volatile digital storage medium, in which thecomputer program is incorporated in the computer-readable medium of the computerprogram product. The computer-readable medium comprises a suitable memory, suchas, for example: ROM (Read-Only Memory), PROM (Programmable Read-OnlyMemory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically ErasablePROM), a hard disk unit, etc. ln the embodiments illustrated above, embodiments of the present invention have beenapplied to a pantograph 184 operable by the direct current motor 185. However, it isto be understood that embodiments of the present invention may be applied to otherconfigurations or apparatuses, where a direct current motor 185 is used, and, for example, where an unsafe end position is present. One of many example is an awning.

Any electrical connection mentioned above may, or may not, include one or more of the group of: a capacitive coupling, an inductive coupling and an electrical transformer.

The present invention is not limited to the above described embodiments. lnstead, thepresent invention relates to, and encompasses all different embodiments being included within the scope of the appended independent claims.

Claims (15)

Claims

1. A method for controlling an electrical circuit (202), the electrical circuit (202)being configured to control a direct current motor (185), the direct current motor (185)being operable between a first end stop (S1) and a second end stop (S2), the electricalcircuit (202) comprising an electrically operable first switching device (R1) switchable between an openposition and a closed position, an electrically operable second switching device (R2) switchable between anopen position and a closed position, and an electrically operable third switching device (Rs) switchable between anopen position and a closed position, wherein in the closed position the first switching device (R1) is configured toprovide a first connection (216) of the direct current motor (185) to an electric powersource (218) to operate the direct current motor (185) in a first direction toward thesecond end stop (S2), wherein in the open position the first switching device (R1) is configured to beconnected to ground (206), wherein in the closed position the second switching device (R2) is configuredto provide a second connection (220) of the direct current motor (185) to the electricpower source (218) to operate the direct current motor (185) in a second directiontoward the first end stop (S1), wherein in the open position the second switching device (R2) is configured tobe connected to ground (206), and wherein in the closed position the third switching device (Rs) is configured toprovide a third connection (222) between the electric power source (218) and the firstconnection (216) and between the electric power source (218) and the secondconnection (220), wherein the method comprises: while the second switching device (R2) is controlled to remain in the openposition and the third switching device (Rs) is controlled to remain in the open position,controlling (301) the first switching device (R1) to switch from the open position to the closed position; and when the first switching device (R1) has been controlled to switch from theopen position to the closed position and is controlled to remain in the closed positionwhile the second switching device (R2) is controlled to remain in the open position,controlling (304) the third switching device (Rs) to switch from the open position to theclosed position in order to operate the direct current motor (185) in the first directiontoward the second end stop (S2).

2. A method according to claim 1, wherein the method comprises: when the direct current motor (185) has been operated to a first position (S2a)while the second switching device (R2) is controlled to remain in the open position andthe third switching device (Rs) is controlled to remain in the closed position, controlling(307) the first switching device (R1) to switch from the closed position to the openposition; and when the first switching device (R1) has been controlled to switch from theclosed position to the open position and is controlled to remain in the open positionwhile the second switching device (R2) is controlled to remain in the open position,controlling (308) the third switching device (Rs) to switch from the closed position to the open position.

3. A method according to claim 1 or 2, wherein the method comprises: while the first switching device (R1) is controlled to remain in the open positionand the second switching device (R2) is controlled to remain in the open position,controlling (401) the third switching device (Rs) to switch from the open position to theclosed position; and when the third switching device (Rs) has been controlled to switch from theopen position to the closed position and is controlled to remain in the closed positionwhile the first switching device (R1) is controlled to remain in the open position,controlling (404) the second switching device (R2) to switch from the open position tothe closed position in order to operate the direct current motor (185) in the seconddirection toward the first end stop (S1).

4. A method according to claim 3, wherein the method comprises: when the direct current motor has been operated to a second position (S1a)while the first switching device (R1) is controlled to remain in the open position and thesecond switching device (R2) is controlled to remain in the closed position, controlling(407) the third switching device (Rs) to switch from the closed position to the openposition; and when the third switching device (Rs) has been controlled to switch from theclosed position to the open position and is controlled to remain in the open positionwhile the first switching device (R1) is controlled to remain in the open position,controlling (408) the second switching device (R2) to switch from the closed position to the open position.

5. A method according to any one of the claims 1 to 4, wherein the methodcomprises: while the second switching device (R2) is controlled to remain in the openposition, while the third switching device (Rs) is controlled to remain in the openposition, and while the first switching device (R1) is controlled to switch from the openposition to the closed position, monitoring (302) any movement of the direct currentmotor (185); and if a movement of the direct current motor (185) is registered, determining (303)that the third switching device (Rs) is stuck in the closed position.

6. A method according to any one of the claims 1 to 5, wherein the methodcomprises: when the first switching device (R1) has been controlled to switch from theopen position to the closed position and is controlled to remain in the closed position,while the second switching device (R2) is controlled to remain in the open position, andwhile the third switching device (Rs) is controlled to switch from the open position tothe closed position, monitoring (305) any movement of the direct current motor; and if a non-movement of the direct current motor (185) is registered, determining(306) that one or more of the following group of situations is/are valid: o The third switching device (Rs) is stuck in the open position; o The first switching device (R1) is stuck in the open position; and o The second switching device (R2) is stuck in the closed position.

7. A method according to any one of the claims 1 to 6, wherein the methodcomprises: while the first switching device (R1) is controlled to remain in the open position,while the second switching device (R2) is controlled to remain in the open position, andwhile the third switching device (Rs) is controlled to switch from the open position tothe closed position, monitoring (402) any movement of the direct current motor (185);and if a movement of the direct current motor (185) is registered, determining (403)that one of the following group of situations is valid: o The second switching device (R2) is stuck in the closed position; and o The first switching device (R1) is stuck in the closed position.

8. A method according to any one of the claims 1 to 7, wherein the methodcomprises: when the third switching device (Rs) has been controlled to switch from theopen position to the closed position and is controlled to remain in the closed position,while the first switching device (R1) is controlled to remain in the open position, andwhile the second switching device (R2) is controlled to switch from the open positionto the closed position, monitoring (405) any movement of the direct current motor (185);and if a non-movement of the direct current motor (185) is registered, determining(406) that one or more of the following group of situations is/are valid: o The third switching device (Rs) is stuck in the open position;o The second switching device (R2) is stuck in the open position; and o The first switching device (R1) is stuck in the closed position.

9. A computer program (803) comprising instructions which, when the programis executed by a computer, cause the computer to carry out the method according toany one of the claims1 to 8.

10. A computer-readable medium comprising instructions which, when theinstructions are executed by a computer, cause the computer to carry out the method according to any one of the claims 1 to 8.

11. A control arrangement (150) for contro||ing an electrical circuit (202), theelectrical circuit (202) being configured to control a direct current motor (185), the directcurrent motor (185) being operable between a first end stop (S1) and a second endstop (S2), the electrical circuit comprising an electrically operable first switching device (R1) switchable between an openposition and a closed position, an electrically operable second switching device (R2) switchable between anopen position and a closed position, and an electrically operable third switching device (Rs) switchable between anopen position and a closed position, wherein in the closed position the first switching device (R1) is configured toprovide a first connection (216) of the direct current motor to an electric power source(218) to operate the direct current motor (185) in a first direction toward the secondend stop (S2), wherein in the open position the first switching device (R1) is configured to beconnected to ground (206), wherein in the closed position the second switching device (R2) is configuredto provide a second connection (220) of the direct current motor (185) to the electricpower source (218) to operate the direct current motor (185) in a second directiontoward the first end stop (S1), wherein in the open position the second switching device (R2) is configured tobe connected to ground (206), and wherein in the closed position the third switching device (Rs) is configured toprovide a third connection (222) between the electric power source (218) and the firstconnection (216) and between the electric power source (218) and the secondconnection (220), wherein the control arrangement (150) is configured to: while the second switching device (R2) is controlled to remain in the openposition and the third switching device (Rs) is controlled to remain in the open position, control (301) the first switching device (R1) to switch from the open position to theclosed position, and when the first switching device (R1) has been controlled to switch from theopen position to the closed position and is controlled to remain in the closed positionwhile the second switching device (R2) is controlled to remain in the open position,control (304) the third switching device (Rs) to switch from the open position to theclosed position in order to operate the direct current motor (185) in the first directiontoward the second end stop (S2).

12. An electrical circuit (202) for controlling a direct current motor (185), the directcurrent motor (185) being operable between a first end stop (S1) and a second endstop (S2), the electrical circuit (202) comprising an electrically operable first switching device (R1) configured to switchbetween an open position and a closed position, an electrically operable second switching device (R2) configured to switchbetween an open position and a closed position, and an electrically operable third switching device (Rs) configured to switchbetween an open position and a closed position, wherein in the closed position the first switching device (R1) is configured toprovide a first connection (216) of the direct current motor (185) to an electric powersource (218) to operate the direct current motor (185) in a first direction toward thesecond end stop (S2), wherein in the open position the first switching device (R1) is configured to beconnected to ground (206), wherein in the closed position the second switching device (R2) is configuredto provide a second connection (220) of the direct current motor (185) to the electricpower source (218) to operate the direct current motor (218) in a second directiontoward the first end stop (S1), wherein in the open position the second switching device (R2) is configured tobe connected to ground (206), wherein in the closed position the third switching device (Rs) is configured toprovide a third connection (222) between the electric power source (218) and the first connection (216) and between the electric power source (218) and the secondconnection (220), and wherein the electrical circuit (202) comprises a control arrangement (150)according to claim 11.

13. A direct current motor unit (204) comprising a direct current motor (185) andan electrical circuit (202) as claimed in claim 12,

14. A vehicle (100) comprising one or more of the group of:o a control arrangement (150) as claimed in claim 11;o an electrical circuit (202) as claimed in claim 12; and o a direct current motor unit (204) as claimed in claim 13.

15. A vehicle (100) according to claim 14, wherein the vehicle (100) comprises apantograph (184) operable by the direct current motor (185).