CN116710336A - Trailer braking control system - Google Patents

Abstract

A system and method for controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination is provided. The coupling force between the vehicle and the trailer is determined and used to control the operation of the trailer brake system in accordance therewith. Using a master control strategy based on the determined coupling force being within the coupling force range; and using one or more auxiliary control strategies based on the determined coupling force being outside of the coupling force range.

Description

Trailer braking control system

Technical Field

The present invention relates to control systems for vehicle trailer brakes, particularly for agricultural vehicles such as tractors.

Background

Many vehicles are provided with attached trailers for transporting items and materials. For large scale use, such trailers may be provided with trailer brake systems to enable safe control of the trailer and to prevent the trailer from buckling (jack-knifing) or slipping during braking.

Both V-bending or skidding occurs when the force (also called coupling force) exerted by the trailer on the tractor exceeds a certain level. The coupling force is mainly generated by the weight of the trailer and the inertia during braking. The first effect of excessive coupling force is that the tractor is excessively pushed (hereinafter referred to as a push condition) and the vehicle track guiding force is overcome. This results in a yaw moment/movement about the vertical vehicle axis of the tractor that is not tolerated by the wheel-ground contact. The tractor then begins to slip.

Another effect may be that in the case of a drawbar trailer in which the front wheels are pivotally attached to the chassis of the trailer, the drawbar may inadvertently pivot relative to the chassis by a coupling force such that the trailer behaves like a folding knife and deviates from its track.

These effects are particularly pronounced when the vehicle is decelerating without the driver activating the service brake system of the vehicle, and occur when the continuously variable transmission is downshifting or the retarder is used on a truck.

It is known to reduce these effects by activating the brakes of the trailer in response to the coupling force to stabilize the vehicle combination. However, the brake actuation must be applied appropriately to reduce the coupling force and to avoid over-braking to destabilize the vehicle combination, as over-stretching of the combination will also apply a yaw moment to the towing vehicle.

With the introduction of electronic brake systems in which the braking force can be controlled independently of the driver, input systems have been developed especially for trucks.

Thus, trailers used in conjunction with trucks primarily use information from on-board auxiliary systems (e.g., electronic trailer suspensions, ABS, ESP, ASR) to determine the coupling force. In particular, the trailer suspension helps to determine the weight of the trailer, and other ones of these sensors help to fine tune brake actuation by determining wheel speed and acceleration.

With the current focus on agricultural vehicle combinations (primarily tractors and agricultural trailers), it must be considered that the above-described braking systems are not as common as those used with trucks. In particular, trailers are rarely equipped with on-board auxiliary systems (e.g., electronic trailer suspensions, ABS, ESP, ASR), and it is therefore difficult to determine the coupling force.

It is therefore a primary object of the present invention to provide a method of controlling the braking force of a trailer independently of knowledge of trailer parameters, in particular the weight of the trailer. Furthermore, the method should include only parameters and components that are already installed on the tractor to reduce maintenance costs and complexity.

In addition, tractors, particularly tractors having a Continuously Variable Transmission (CVT) such as a hydrostatic-mechanical split transmission, are particularly provided with different modes of operation to determine driver demands for acceleration and deceleration of the vehicle, including a driver lever mode in which the driver inputs acceleration or deceleration (or a combination) of the vehicle by pushing or pulling a lever, and a foot pedal mode in which the vehicle speed is set by stepping on a foot pedal.

It is a further object of the invention to include different modes of operation in the method to provide improved trailer brake control.

It is an object of the present invention to provide a trailer brake control system that overcomes the above-mentioned problems to determine the braking force applied to a trailer.

Disclosure of Invention

An aspect of the invention provides a control system for controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination, the control system comprising a vehicle control unit and being configured to: determining a coupling force between the vehicle and the trailer; and generating and outputting a control signal for controlling the operation of the trailer brake system according to the determined coupling force; wherein the control system is configured to: controlling operation of the trailer brake system in accordance with a master control strategy in dependence on the determined coupling force being within a coupling force range; and controlling operation of the trailer brake system in accordance with one of one or more auxiliary control strategies depending on the determined coupling force being outside the coupling force range.

Another aspect of the invention provides a brake system comprising and/or controllable by the control system of the preceding aspect of the invention.

Another aspect of the invention provides an agricultural vehicle that can be coupled to a trailer to form a vehicle-trailer combination and that includes and/or can be controlled by the control system described herein.

Another aspect of the invention provides a method of controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination, comprising: determining a coupling force between the vehicle and the trailer; and generating and outputting a control signal for controlling the operation of the trailer brake system according to the determined coupling force; wherein the method comprises the following steps: controlling operation of the trailer brake system in accordance with a master control strategy in dependence on the determined coupling force being within a coupling force range; and controlling operation of the trailer brake system in accordance with one of one or more auxiliary control strategies depending on the determined coupling force being outside the coupling force range.

Other advantageous embodiments and features are described herein with reference to the following description and/or the appended claims.

Drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 schematically shows a side view of a vehicle combination using the invention,

figures 2, 3, 4, 5 are flowcharts showing the main processing steps of implementing the method of the invention,

figure 6a schematically shows a side view of a combination of applied force and vehicle using the invention,

FIG. 6b is a characteristic diagram showing resistance depending on the vehicle speed, and

fig. 7 is a characteristic diagram showing the result of a method for controlling a trailer brake control signal (TBS) according to the present invention.

Detailed Description

Fig. 1 shows a vehicle combination 1 comprising a tractor 10 and a trailer 20, which is attached to a tractor hitch system 11 of the tractor 10 via a trailer hitch lever 21. The tractor 10 includes front wheels 5 and rear wheels 6 that are braked by a service brake system and a parking brake system, which are not described in detail below, as is well known in the art. For braking the trailer, the trailer brake system 30 mainly comprises a trailer brake valve 30a and/or other valve arrangements and is arranged to forward a pneumatic or hydraulic brake signal to the trailer via a standardized trailer control coupling 31. Other trailer supply couplings 32 are provided to supply air or oil to the trailer brakes. At least the trailer brake system 30 is connected to the brake system 40 of the trailer using two couplings 31, 32. The brake system 40 is used to actuate brakes of the wheels 25 of the trailer 20.

For example, trailer brake actuation pressure may be generated by the trailer brake system 30 when a driver activates the service brake system and/or the park brake system (using a hand brake lever) of the tractor 10 with a brake pedal (not shown) such that the braking request is directly forwarded to the trailer brake system 30 by a pressurized fluid, such as air or oil. Alternatively, the trailer brake actuation pressure may be generated independently of direct driver actuation, but in response to a trailer brake signal TBS from an electronic vehicle control unit ECU, also referred to as electronic trailer braking. The following invention focuses on this type of brake signal generation.

To provide a control system for the trailer brakes of the tractor 10, trailer 20, the electronic vehicle control unit ECU receives parameters and/or sends control signals to various components of the tractor 10 such as:

the transmission 50 for adjusting the vehicle speed v or the vehicle acceleration a according to the driver's required set value, and receiving parameters such as the output rotation speed and rotation direction of the transmission output shaft and the system pressure of the hydraulic branch of the CVT (continuously variable transmission) 100.

A gyroscope 60 for determining the vehicle speed v or the vehicle acceleration and/or inclination α. The gyroscope may be part of a satellite-based navigation system.

HMI components such as the following:

an o-speed pedal 71 and/or a drive rod 72 for receiving driver input for vehicle speed or vehicle acceleration.

An o acceleration rate input 73 for adjusting the degree of acceleration/deceleration when the drive rod 72 is moved

An o-clutch pedal 74 for disconnecting the transmission 50 from a prime mover, such as an internal combustion engine.

An o HMI terminal 75 for enabling the driver to input or display various parameters relating to the vehicle 10, trailer 10 or vehicle combination 1.

o service brake foot pedal 76 for receiving driver input for activating a service brake of the tractor.

o a parking brake switch or parking brake lever 77 for receiving driver input for a service brake for activating the service brake of the tractor.

In summary, the main task of the electronic vehicle control unit ECU is to provide a processing method comprising:

receiving relevant parameters of the vehicle 10;

determining the set value of the trailer brake signal TBS according to the method described hereinafter; and

forwarding the trailer brake signal TBS to the trailer brake control system 30 to activate the trailer brakes.

In the illustrated embodiment, the trailer brake signal TBS is represented by a pressure demand that controls the pneumatic trailer brake system 30. Alternatively, the trailer brake signal TBS may be set to control the hydraulic brake system, and the trailer brake valve 30a is also hydraulically operated. Further alternatively, if the brake-by-wire system is mounted on the trailer, the trailer brake signal TBS may be forwarded to the trailer brake system by any other means, such as an electronic signal.

A method for controlling the trailer brake control system 30 will now be described with reference to the flowcharts of fig. 2, 3, 4, 5.

The method may be implemented on an electronic vehicle control unit ECU or may alternatively be part of the trailer brake control system 30 when equipped with a corresponding control unit and interface to receive the above mentioned parameters.

According to the ongoing method, the electronic vehicle control unit ECU iteratively generates a trailer brake signal TBS to be forwarded to the trailer valve 30 a. The trailer brake signal TBS receives different values as described below.

The electronic vehicle control unit ECU executes the method M100 as depicted in fig. 1. For clarity reasons, the main method M100 is depicted in terms of several sub-processes, wherein fig. 2 shows a main method M100 comprising a sub-process S200 as shown in fig. 3, a sub-process S300 as shown in fig. 4 and a sub-process S400 as shown in fig. 5.

Referring now to fig. 2, the electronic vehicle control unit ECU initializes the method with step S100. If ignition is started (ON) and the electronic vehicle control unit ECU is powered ON, an initialization may be triggered. Alternatively, if the electronic vehicle control unit ECU detects that the trailer 20 is attached to the vehicle 10, an initialization may be triggered. This may be determined if a standardized current supply connector (supplying current to the trailer 20 and/or turning on a light or turn indicator of the trailer 20) is connected to a receiving connector on the vehicle 10.

After initialization, if the electronic trailer brake function is started (etcv=1), the method checks in step S105 and then branches to the subroutine in steps S200, S300. When the ignition is started and the electronic vehicle control unit ECU is energized, the electronic trailer brake may be activated or may be initially activated/deactivated by driver input. Alternatively, the electronic trailer brake may be temporarily suspended by actuation of the service brake or the parking brake. Disabling the trailer brake function results in parameter etcv=0.

In subroutine S200, a number of prerequisites and start-up parameters, which are further carried out in method M100, are checked, as depicted in fig. 3. The term precondition means that these conditions must be met to generally allow the electronic trailer brake to be activated, while the activation parameters are used to determine what event causes deceleration, and in addition the degree of deceleration can be established and the trailer brake signal adjusted accordingly.

After starting in S201, step S205 sets the status parameter SP _DL 、SP _AS 、SP _CA 、SP _CC 、SP _REV 、SP _ENG (re) set to zero. The status parameters are described later.

Typically, this start-up check allows the preconditions that the electronic trailer brake function is activated and whether and how the vehicle is decelerating, especially but not exclusively if this is done by using an accelerator pedal 71 or a drive lever 72. Furthermore, this step is used to determine a driver demand for a degree of deceleration, which is also referred to as driver deceleration demand DD.

These preconditions attempt to avoid unsafe vehicle conditions caused by the electric trailer brakes, and serve to avoid unintended or unnecessary electric trailer brakes, which results in the driver possibly feeling uncomfortable when the auxiliary system initiates the trailer brakes when it is obviously unnecessary. In other words, when not needed, the electronic trailer brakes should be disabled.

Step S206a is performed by determining the coupling force F _C,real (see subroutine S300) whether or not it is lower than the set value F _CA,min (say, -3500N) (within the negative sign) to ensure that the trailer 20 is pushing the tractor 10 significantly (push condition) to check the first precondition. There is a possibility that a high coupling force F may occur _C,real (smaller when viewed with a negative sign) but should not activate the electric trailer brake. This condition may occur, for example, if the implement is initially coupled to a tractor, or if a pothole is passed. If not, the process returns to before step S206a with loop L207.

Step S206a must be regarded as a prerequisite for: once this precondition is met, the coupling force F is made _C,real Can take any value in the further processing, even above F _CA,min Without stopping the process or starting.

In the next step, a series of other preconditions are checked:

step S210a checks whether the driveline clutch is activated. This provision is necessary when, for example, the operator intends to have the vehicle combination roll towards the intersection. The method should not be further performed because this results in the CVT being drivingly disconnected from the wheels, making it impossible to determine the coupling force based on CVT parameters. Therefore, if yes, step S210b proceeds to check the next precondition, and if no, step S220, which will be described later, is performed later.

Step S210a is provided after step S206a (coupling force is required to be detected when the clutch is disengaged) to ensure that the start is suspended every time the clutch is subsequently disengaged.

Next, steps S210b and S210c proceed to check two preconditions in the OR relationship, OR meaning that one of the two is satisfied. According to step S210b, the vehicle speed should be v _V >0kph (or alternatively, v _SET >0 kph), or according to step S210c, when the negative sign is a downhill inclination, the tractor 10 is at a, for example, -4 °α<α _CA，max Uphill driving because both conditions are known to lead to a push condition. Alternatively, step S210b may consider the vehicle speed v _V Or vehicle speed set point v _set The minimum value is exceeded to avoid the start-up of the electronic trailer at low speeds where the push condition is less severe. When one of these preconditions is satisfied, the method proceeds to step S220 described later. Otherwise, in step S210d, the next precondition is checked.

Step S210d is provided to avoid that the electronic trailer brake is activated when stationary on flat ground (no grade or low grade). Therefore, step S210d checks whether v is satisfied _v =0kph (or alternatively, v _SET >0 kph) and whether the slope is close to zero. This is particularly important when a CVT with so-called "active rest" control is installed: if the vehicle is decelerated to rest (0 kph) by the speed foot pedal 71 or the drive lever 72 without actuating the service brake or the parking brake, the CVT operates in "active rest". Under this condition, electronic vehicle control The control unit ECU provides control of the transmission to maintain the output speed of the transmission (and hence the wheels) at 0rpm to compensate for unintentional movement caused by idle oil flow in the hydraulic branch of the CVT (as described in applicant's published patent applications EP 1 990 230 and EP 2 935 948). This means that the hydraulic unit is constantly regulated, which may lead to that coupling forces which should not lead to the actuation of the trailer brake can be detected.

In summary, steps S210b, S210c and S210d are used to allow electronic trailer braking when driving on flat ground, uphill or downhill and when the tractor is stationary on a downhill, as a push condition may exist. However, when standing on an uphill or flat ground, starting should be prohibited, as these conditions do not lead to a push condition.

When the result of step S210d is YES, loop L210 returns to before step 210, wherein the status parameter SP _CA Keep zero.

Alternatively, other preconditions indicated by step S210d may be checked and may lead to further processing of step S220 or to a loop back to step 210, where the status parameter SP _CA Keep zero.

Other preconditions not shown in fig. 3 may be:

CVT is switched to "neutral": in this operating condition, which is initiated via the HMI terminal, the CVT is brought into a condition similar to the clutch engagement described in step S210a, in which the CVT is drivingly disconnected from the wheels, so that it is impossible to determine the coupling force based on CVT parameters.

Condition "EU brake test": when applying the parking brake on the tractor at rest, the driver initiates this condition to inhibit actuation of the service braking function of the trailer brake. Due to EU regulations, this test procedure must be performed periodically to check if the tractor's parking brake system (energized by the spring load) is able to adequately hold the vehicle combination stationary (when closed) in the event that the trailer brake may fail due to a leak/malfunction of the trailer brake system. The electronic trailer brakes must be permanently disabled during testing without accidentally actuating the trailer brakes.

Activating the electronic trailer braking function: similar to step S105 (in fig. 3), the electronic trailer brake function (etcv=1) must be activated.

Maximum speed requirement: if the vehicle speed exceeds 25kph. Above a certain vehicle speed, the wheels tend to lock more when braked. This may cause dangerous situations, especially at high speeds, and thus inhibit the method when a certain vehicle speed is exceeded. The maximum vehicle speed value may be determined based on the driver's selection or may be set based on trailer parameters. For example, if the trailer is equipped with an ABS system, no restriction may be necessary.

The method detects in which way the operator inputs a request for deceleration of the vehicle (without actuating the service brake or the parking brake). This is done in startup branches B211, B212, B213, B214, and B215. The start-up branch B211 starts at step S220, in which the start-up via the drive lever 72 is checked. If the operator intends to slow the vehicle, he pushes the drive rod 72 back in the opposite direction as indicated by arrow DR. Thereby, the request value V forwarded to the ECU _DL In the negative range, and parameter V _DLminus Is set to 1. If the drive lever 72 is released, the vehicle speed remains constant, such that the parameter V _DLminus Is set to 0.

If the parameter V _DLminus Is set to 1, this leads to step S225, in which the status parameter SP _DL Is set to 1 to indicate that deceleration is input via the drive lever 72. The next step is step S226, wherein the value of the acceleration rate input 73 is determined. Acceleration rate input 73 is used to determine operator input regarding the driver deceleration request DD in response to operator input, thus providing four setpoints: stage I, stage II, stage III, stage IV. If the operator adjusts the acceleration rate input 73 to the status parameter SP _AS The I-level of the value 1 will be received, the running speed of the vehicle decreases most slowly, so that the deceleration is low and smooth. In the state parameter SP _AS Grade IV of value 4 will be received, the travel speed of the vehicle speed will decrease rapidly and will result in a "sharp" deceleration.

ReplaceableThe drive rod may provide proportional speed control, meaning that the acceleration rate depends on the deflection angle or deflection speed. In this case, the acceleration level input 73 may not be present, and the status parameter SP _AS Will be set according to the deflection angle or speed.

If the parameter V _DLminus Is set to 0 to indicate that the vehicle is not decelerating via the drive rod 72, the start branch B212 is further executed, wherein further operator input is checked.

Thus, branch B212 branches at branches B213, B214, and B215.

In step S230, with the branch B213, the process checks prohibition of cruise control. If so, the deceleration via the speed foot pedal 71 is checked in step S232. The speed foot pedal 71 is depressed by the operator's foot and forwards the speed request to the ECU. This differs from the driver joystick 72 in that the yaw angle is proportional to the desired value of the vehicle speed. In other words, if fully depressed, the requirement is a maximum vehicle speed, or alternatively, any vehicle speed limit value that the driver may set via the HMI terminal 75. For example, if the vehicle is operated for track-turning, the driver may set a lower speed assigned to full pedal depression to increase pedal resolution and enable finer control. If the speed foot pedal 71 is fully released (after any stepping), the vehicle speed is required to be 0kph, which means that the vehicle is decelerated. Therefore, step S232 checks whether the pedal mode is activated. If not, depressing the speed foot pedal 71 will not affect vehicle movement, but simply adjust the engine speed. As a result, the loop L233 returns to before step S205.

Step S234 checks whether the speed foot pedal 71 is completely released (after stepping on) so that V _FP Is set to 0. If not, loop L235 returns to before step S205.

If so, step S236 sets the state parameter sp _DL Set to zero. Referring to step S225, a parameter is set according to the operation of the drive lever 72, a state parameter sp _DL It is common to provide whether the speed foot pedal 71 or the drive lever 72 indicates a decelerationIs a piece of information of (a).

If step S230 indicates cruise control is enabled, branch B213 proceeds to determine the subsequent conditions that exist in the cruise control mode.

Thus, step S240 determines whether the current vehicle speed exceeds the cruise control set point.

This occurs in a first cruise control condition, wherein the cruise control set point is changed by:

first of all, the HMI terminal enables the driver to save the setpoints C1 and C2 for the different cruise control setpoints. Both of these values may be preselected by pressing a button assigned to C1 and C2, which may be disposed near the drive rod 72 or on the drive rod 72. For example, if C1 is 18kph for field operations and C1 is 60kph for fast driving on a road, the driver uses this HMI function to switch from a set point used in the field or on the road, for example. The driver initiates the cruise control set point by using the drive lever 72. When the drive lever 72 is used to accelerate or decelerate the vehicle by moving forward and backward in the drive direction, cruise control is activated by briefly moving the drive lever 72 to the right. If no value C1 or C2 is preselected, the current speed is considered a new setpoint value.

Second, the driver may adjust the cruise control set point in the HMI terminal 75, which may also lead to significant deceleration if a new set point below the current vehicle speed is selected.

Even without a significant set point speed reduction, the cruise control mode may still lead to a situation where electronic trailer braking is required, which situation is referred to as the second cruise control mode. This may occur if the vehicle combination is traveling in cruise control mode on a flat road and then enters a downhill path. The weight of the trailer will then begin to push the tractor, causing the vehicle speed to increase and deviate from the set point.

In summary, step S240 determines that the vehicle speed is at V in cruise control mode _V >f _CAv *v _SET A significantly changing condition, this is at the current vehicle speed v _V By a factor of f _CAv Exceeding the cruise control speed set point v _SET When (1). Factor f _CAv Representing a percentage change such that f _CAv =1.05 means the current vehicle speed v _v Exceeding the speed set point v _SET About 5%.

If the condition v is not satisfied _V >f _CAv *v _SET The loop L241 returns to before step S205.

If condition V is satisfied _V >f _CAv *v _SET Step S242 will be in cruise control mode SP _CC The status parameter of the down-start is set to 1, thereby indicating that the electronic trailer brake is started based on the condition in the cruise control mode.

As in the first cruise control mode, the degree of deceleration depends on the setting of the acceleration rate input 73, and in step S243 similar to step S226, the state parameter SP is stored _AS 。

The degree of deceleration is not dependent on the setting of the acceleration rate input 73, as in the second cruise control condition, and the state parameter SP when the set point is not changed but the vehicle speed is increased relative to the set point in downhill running in the second cruise control mode _As May always be set to a single value, say 2.

Other conditions are checked using branch B214, and in branch B214 the process determines that the tractor is reversing. Reversing of a tractor or combination of vehicles means that the operation of the tractor is changed from a first (say, forward) direction at a predetermined vehicle speed to an opposite direction having the same or a preselected vehicle speed. Thus, reversing always results in a deceleration, which may cause a push condition such that the electronic trailer brake must be activated. Reversing may be initiated through an operator user interface. The tractor then decelerates, goes through rest and changes to travel in the opposite direction without further manual intervention. This function provides for comfortable handling, for example during front loader operation. Reversing of the tractor 10 may be initiated by various inputs:

Reversing is initiated by moving the drive rod 72 to the left when the drive rod 72 is used to accelerate or decelerate the vehicle by moving forward and backward in the drive direction.

In addition, a button is provided near the steering wheel, for example, on the indicator lever, to reverse the tractor 10.

In addition, the driver may choose whether to provide reverse at the same speed by merely changing direction, or change direction and slow down/accelerate to a set point that may be preselected in the HMI terminal 75 for each direction of travel. This is advantageous in that the driver may prefer to travel slower when traveling backwards.

Thus, along branch B214, followed by step S250, the method checks if the tractor is reversing. If not, loop L251 returns to before step 205.

If the condition is satisfied, the status parameter SP in step S252 _REV Is set to 1, and since the degree of deceleration depends on the setting of the acceleration rate input 73, in step S253, the state parameter SP is stored _AS 。

In addition, branch B215 and step S260 monitor for a decrease in engine speed. The HMI terminal enables the driver to maintain setpoints MAX and MIN for different engine speed setpoints. Both of these values may be selected by pressing a button assigned to MAX and MIN, which may be disposed near the drive rod 72 or on the drive rod 72. Alternatively, the tractor 10 may be equipped with a manual throttle (not shown) that enables the driver to directly adjust the engine speed via rotational control. Since a significant decrease in engine speed results in deceleration, step S260 monitors an _ENG >Δn _CAmax And if the engine speed decreases by more than about say an _CAmax =200 rpm, then state parameter SP _ENG Is set to 1 to indicate that the electronic trailer brake is activated based on the engine speed decrease. The branching may additionally include determining other state parameters to account for the dependence on the engine speed difference Δn _ENG Is a degree of deceleration of the absolute value of (a). Δn _ENG The greater the deceleration, the higher the deceleration can be, thus for example Δn _ENG =200 rpm or Δn _ENG =400 rpm or Δn _ENG =600 rpm, there may be different values of the deceleration state parameters。

All the startup branches B211, B212, B213, B214, B215 are merged in step S270, wherein the status parameter SP when one of the startup requirements in branches B211 to B215 is met _AS Is set to 1 to indicate that actuation is normally enabled regardless of whether actuation is caused by the drive lever 72 or the speed foot pedal 71 or any other condition.

With step S250, the method proceeds to step 120, as depicted in fig. 2.

In parallel with step S200, step S300 determines the actual coupling force F by taking into account various driving dynamics parameters _c,actual As depicted in fig. 4.

Further description of the actual coupling force F is made with reference to FIG. 6a _c,actual The figure depicts the forces exerted on the vehicle combination 1, in particular on the tractor 10, for driving conditions in which the vehicle combination 1 is driving uphill and the risk of V-bending is particularly high.

The balance of forces exerted on the tractor 10 is well known in the art and results in the following equation:

F _TRC ＝F _IN +F _H +F _AR +F _R,RA +F _R,FA +F _C (E1)

wherein, the liquid crystal display device comprises a liquid crystal display device,

F _TRC is the traction that must be supplied by the IC engine and transmission 50 to the wheels 5, 6 of the tractor 1 to move the complete vehicle combination 1.

F _IN An inertial force applied due to inertia when the vehicle accelerates or decelerates:

F _A ＝m _v ·a (E2)

F _H is a downhill force applied due to inertia when the vehicle is traveling uphill or downhill:

F _H ＝m _v ·g·sin(α) (E3)

F _AR is the air resistance exerted by the air resistance and depends on various factors such as the geometry of the tractor

F _R,RA ,F _R,FA Is formed by the space between the wheel and the groundRolling resistance applied by the rolling resistance of (c) and depends on various parameters such as wheel load and ground/wheel contact parameters

F _C Is a coupling force representing the force applied by the trailer to the tractor. In the case of deceleration, the coupling force has a negative sign.

Mass m of vehicle _v Is determined according to the prior art and is not described in detail. The mass m can be determined by taking into account the empty weight of the tractor plus an additional ballast (ballast) attached thereto _v . These values may be stored in the ECU. Alternatively, the mass value may be detected from vehicle acceleration or wheel load. A method is described in patent application EP2766239 published by the applicant.

The same applies to the determination of the vehicle acceleration a, inclination α and speed v of the vehicle described and practiced in the art. These two values may be determined by a gyroscope 60, which may be part of a GPS navigation system.

Either a negative or positive sign must be inserted into the force according to the effective direction shown in fig. 6 a.

Similar forces will also occur due to the mass of the trailer and the resistance exerted on the trailer itself. However, the method only considers the resultant force exerted by the trailer on the tractor, i.e. the coupling force F _C . Considering only the parameters applied to the tractor has the main advantage that the trailer does not have to be equipped with sensors or be considered in detail. As mentioned above, various different trailers/implements and their basic technical configurations may hamper detailed consideration of the trailer.

Due to the main coupling force F _C Is a relevant parameter for controlling the trailer brake system, so the formula E1 is changed to:

F _C＝ F _TRC –(F _IN +F _H +F _AR +F _R,RA +F _R,FA ) (E4)

the forces in brackets represent the traction force F of the tractor _TRV 。

F _TRV ＝F _IN +F _H +F _AR +F _R,RA +F _R,FA (E5)

The inertial force F can be easily determined during operation using parameters already available on the tractor _IN And downhill force F _H While the air resistance F _AR And rolling resistance F _R,RA 、F _R,FA Is summed to become total resistance F _R 。

F _TRV ＝F _IN +F _H +F _R (E6)

Total resistance F _R Taken from the graph shown in fig. 6b in which the vertical axis represents the total resistance F _R And the horizontal axis represents the vehicle speed v. The graph is determined by a coasting test during development and then stored in the ECU for each vehicle series. The graph shown is determined for a vehicle on an asphalt road (or road operation). Alternatively, other graphs for grass, farmland or gravel tracks may be determined, which may then be considered when the vehicle is provided with means for detecting on which terrain the vehicle is travelling. This may be determined by a GPS navigation system transmitting geographical information, for example, if the vehicle is traveling on a public road (asphalt road), gravel road or off any road (possibly grassland or farmland).

For example, in the graph shown, the total resistance F at, for example, 25kph _R Regarded as 2575N

Thus, by using equations E1 and E2 and the graph shown in FIG. 6b, the traction force F of the tractor _TRV Can be sufficiently determined by the formula E6.

To receive the coupling force F _C The remainder are:

F _C＝ F _TRC -F _TRV (E7)

as is known in the art, the tractive effort of a vehicle combination FTRC is determined by measuring the fluid pressure in a hydrostatic-mechanical split Continuously Variable Transmission (CVT) that includes a hydraulic drive circuit in which a hydraulic pump supplies pressurized fluid to a hydraulic motor. Details are described in applicant's published patent application WO2013/053645 and are not described in detail. Alternatively, any other means may alternatively be employed to determine the tractive effort of the vehicle combination FTRC, such as using torque supplied by the engine to receive the tractive effort, as described in US 4 548 079.

(see GB 11/44)

The coupling force may then be received with equation E7.

The method in fig. 4 is performed using the equations and forces mentioned above. After starting from step 301, the first branch B305 determines the traction force F of the vehicle combination in step S335, as explained above _TRC 。

As explained above, the second branch B310 determines the mass m in step S320 _v Acceleration a and inclination α to further calculate inertial force F in step S325 _IN And in step 326 calculate the downhill force F _H 。

In the third branch B315, step S330 determines the velocity v as described above to further determine the total resistance F in step S331 with reference to fig. 6B _R 。

The second branch B310 and the third branch B315 then proceed to step S340 to calculate the traction force F of the tractor as defined by E6 _TRV 。

Finally, the actual coupling force F is then calculated from E7 using the values received in steps S335 and S340 _C.actual 。

Alternatively, the steps shown in fig. 4 may be performed one after the other, or in any reasonable order.

Referring to fig. 2, the sub-process S300 is continuously performed to transmit the actual coupling force F for further steps _C,actual 。

The method M100 in fig. 2 continues further, with the status parameter SP being continuously monitored in step S110 _CA This indicates that the driver still requires deceleration of the vehicle via the speed foot pedal 71 or the drive lever 72. If the start is interrupted and the status parameter SP _CA Changing to zero, the loop L211 resets all parameters in step S115 and returns to the beginning.

The method M100 in fig. 2 further continues with step S120 of setting the first interval counter c (also referred to as brake interval counter) to zero. ThenIn step S121, a first timer value t ₀ Is also set to zero (seconds) and the timer is started. These two parameters are provided to meet the requirements of the electronic trailer brake system according to EU regulations 2015/68 (date 2014, 10, 15) annex I, number 2.2.1.19.1 (also known as "european union master RVBR") that limit the duration of the electronically activated trailer brake (without the driver operating the service brake) to a maximum duration of 5 seconds. After this, the trailer brakes must be released.

Using a first time value t ₀ The time limit is monitored and the number of braking intervals is determined using a braking interval counter c. Thus, the braking interval is characterized by a period of time during which the electronic trailer braking control is activated/enabled, and may be followed by an optional pause time in which the trailer brakes are not activated. When the trailer brake is activated again after a pause, the next braking interval begins. Thus, if the start-up requirement as described in step 200 is not met and the status parameter SP _CA Returning to zero, the braking interval is interrupted. This results in a reset of all parameters in step 115, thereby also resulting in a first interval counter c and a first timer value t discussed in detail herein ₀ Is set in the reset state.

Step S125 checks whether the method is currently being performed in a first braking interval (meaning that the time limit has not been exceeded) or in a subsequent braking interval.

If so, step S131 sets the pilot pressure p _P ＝P _P,0 The pilot pressure depends only on the driver deceleration demand DD as determined in step S200. Typically, the pilot pressure P _P Increasing with higher deceleration requirements:

if the deceleration is caused by the operator using the speed foot pedal 71 (get status parameter SP _DL =0), then pilot pressure P _P,0 Is set to 70kPA.

If the deceleration is caused by the operator using the drive lever 72 (to obtain the state parameter SP _DL =1), the pressure level depends on the parameter SP _AS Setting of the acceleration rate input 73 provided:

for SP _AS =1 (acceleration rate input 73 is set to level I representing the slowest deceleration), pilot pressure P _P,0 Is set to 50kPA.

For SP _AS =2 (acceleration rate input 73 is set to stage II), pilot pressure P _P,0 Is set to 70kPA.

For SP _AS =3 (acceleration rate input 73 is set to class III), pilot pressure P _P,0 Is set to 100kPA.

For SP _AS =4 (acceleration rate input 73 is set to stage IV), pilot pressure P _P,0 Is set to 150kPA.

If the deceleration is caused by the cruise control (yes is received in step S240) to obtain the state parameter SP in step S242 _CC =1, or if deceleration is caused by the reverse mode being initiated (yes is received in step S250) to obtain the state parameter SP in step S252 _REV =1, then the same value is taken.

If the deceleration is caused by the engine speed decrease in step S260, a "Yes" is obtained (and the state parameter SP _ENG Set to 1), the pilot pressure P _P,0 Is set to 80kPA

In an embodiment, depending on the status parameter SP _AS Pilot pressure P of (2) _P,0 Is shared under different deceleration conditions (state parameter SP _DL 、SP _CA 、SP _CC 、SP _REV 、SP _ENG Is set to 1), but may alternatively be defined differently for each deceleration condition.

These values are held in the ECU and are further considered in step S140 described herein.

If step S125 shows that the method is currently in a subsequent braking interval, step S132 sets the pilot pressure p _P ＝p _P,c The pilot pressure is the trailer pressure signal TBS generated in step S150. This gives the advantage that after the end of the braking interval, the pilot pressure p _P The last generated value in the previous braking interval is always received. This avoids a braking intervalThe peak of the trailer brake signal in between, which will reduce driving comfort.

In step S135, a trailer brake signal TBS is generated, which is also referred to as "First-in-Shot". This step is used to provide a pressure spike that is used to fill the line on the trailer. This step is provided to keep the system biased and make it more responsive because the trailer's size in the agricultural business may vary, so the line of the trailer's braking system may also vary. The height of the trailer brake signal TBS or the trailer brake actuation pressure must be chosen to be high enough to fill the route, but low enough to avoid excessive braking reaction forces, which would cause jolts and negatively impact driving comfort. Thus, "preemption" is time-controlled and depends on the driver deceleration demand DD as determined in step S200.

If the deceleration is caused by the operator using the speed foot pedal 71 (get status parameter SP _DL =0), then the pilot pressure P _FIS Will be 300kPA and the duration is set to 0.03s

If the deceleration is caused by the operator using the drive lever 72 (to obtain the state parameter SP _DL =1), the pressure level and the duration depend on the parameter SP _AS Setting of the acceleration rate input 73 provided:

for SP _AS =1 (acceleration rate input 73 is set to level I representing the slowest deceleration), the prefire pressure P _FIS Will be 300kPA and the duration set to 0.02s.

For SP _AS =2 (acceleration rate input 73 is set to class II), prefire pressure P _FIS Will be 300kPA (alternatively 320 kPA) and the duration is set to 0.03s.

For SP _AS =3 (acceleration rate input 73 is set to class III), prefire pressure P _FIS Will be 300kPA (alternatively 340 kPA) and the duration is set to 0.04s.

For SP _AS =4 (acceleration rate input 73 is set to level IV), prefire pressure P _FIS Will be 300kPA (alternatively 360 kPA) and the duration is set to 0.05s.

If the deceleration is caused by the cruise control (yes is received in step S240) to obtain the state parameter SP in step S242 _CC =1, or if deceleration is caused by initiating the reverse mode (yes is received in step S250) to obtain the status parameter SP in step S252 _REV =1, then the same value is taken.

If the deceleration is caused by the reduction of the engine speed in step S260, a "Yes" is obtained (and the state parameter SP _ENG Set to 1), the pilot pressure P _P,0 Is set to 80kPA

In an embodiment, the pressure P is a pressure _FIS Will be 300kPA and is dependent on the state parameter SP _AS Is shared under different deceleration conditions (state parameter SP _DL 、SP _CA 、SP _CC 、SP _REV 、SP _ENG Is set to 1), but may alternatively be defined differently for each deceleration condition.

In addition, two correction factors f ₁ 、f ₂ Multiplied by the prefire pressure P _FIS To determine the trailer brake signal p _TBS ：

P _TBS ＝f ₁ ×f ₂ ×P _FIS (E8)

Correction factor f ₁ At the position of>In the range between 0.1, and taking into account the following facts: as vehicle speed increases, the high peak of the preemptive pressure causes the trailer to tend to jolt, which negatively impacts ride comfort. On the other hand, when the vehicle combination 1 is traveling downhill, the response of the trailer brake system should be as fast as possible. For correcting coefficient f ₁ The formula is:

thereby making it possible to

·v _Limit Is the vehicle speed below which the pre-roll pressure should be reduced. This value is set to 25kph

·α _Limit Is the inclination below which the pre-roll pressure should be at a maximum level, independent of the vehicle speed. The value is set to-5 DEG

Correction coefficient f ₂ Also at>In the range between 0.1, and taking into account the following facts: during this process, the "prefire" pressure level is reduced to avoid overshooting in the trailer brake actuation pressure such that driving comfort is reduced. For correcting coefficient f ₂ The formula is:

for the first braking interval (c=0):

for any subsequent braking interval (C > 0):

thereby making it possible to

·P _P,0 Is the pilot pressure determined in step S131 taken from the predetermined parameter set.

·P _P,c Is the pilot pressure determined in step S132 taken from the previous braking interval

·P _Limit Is the pressure limit below which the pressure gradually decreases. May be 100kPA

After generating the time-controlled trailer brake signal TBS in step S135, step S140 generates the trailer brake signal TBS directly based on the pressure determination as described in steps 131, 132. The trailer brake signal TBS generated in step S135 remains constant until the ECU is generating other pressure signals TBS, as described herein.

Applying the pilot pressure in accordance with the deceleration condition indicated by the HMI input provides the main advantage of initially initiating trailer brake actuation without first determining a physical value of deceleration or coupling force, such that trailer brake actuation is more active and faster. Even if the coupling force is taken into consideration using step S206a, the pilot pressure does not depend on the magnitude in the initial step.

In step S145, the process waits for 0.75 seconds to enable the ECU to determine the actual coupling force F as described with step S300 _C,actual . Considering the influence of the trailer brake signal TBS generated by steps S135, S140 and the resulting actual coupling force F _C,actual A waiting period is necessary. Otherwise, the ongoing process will be based on the coupling force F still changing under the influence of steps S135, S140 _C,actual 。

In particular, step S140 is used to provide a rapid response to deceleration in the form of a trailer brake signal TBS based on a predetermined pressure value, while a 3-point control algorithm is applied to determine the trailer brake signal TBS during ongoing operation. This causes the system to respond first.

As illustrated in detail in fig. 5, the control algorithm is executed with step S400.

Step S400 and subsequent steps S401 to S490 mainly comprise the step of controlling the trailer brake signal TBS by means of a 3-point controller. Typically, a 3-point controller represents a discontinuous controller type and takes three values 1, 0 and-1. With respect to the generation of the trailer brake signal TBS, the pressure value of the trailer brake signal TBS is increased, kept constant or decreased, respectively. A 3-point controller tends to overshoot less than a continuous controller type (such as P, I or D controller or a combination thereof) and is easier to handle in setting parameters to affect controller dynamics. In particular, these values can be adapted more easily to the operating conditions, which can be done by the driver or by trained maintenance personnel.

After starting from step S401, step S405 sets a state parameter, an In-Shot (In-Shot) parameter SP _IS . Similar to the prior described in step S135, the injection is a time-controlled pressure spike, but is applied in conjunction with a 3-point controller. If the injection parameter SP _IS If =0, no injection is provided, if the injection parameter SP _IS =1, then provide the injection. The injection serves to improve responsiveness by supporting pressure build-up in the trailer brake system 40. However, since the pressure peaks may cause jolt of the trailer, if the coupling force (display of constant determinationShow) falls rapidly, the injection can be deactivated. When a rapid drop (determined in step S300) indicates a rapid reaction to the trailer brake signal TBS, further injection may be omitted. The injection is described in more detail herein.

In parallel with step S405 (or after step S405), step S406 is performed in which the ECU takes a predetermined value defining the lower coupling force F _C,L And upper coupling force F _C,L A defined range of coupling forces, which is required to achieve a 3-point controller and is described herein.

Next, in step S407, a second interval counter i (also referred to as a controller interval counter) is set to zero.

In step S410, the number of control intervals is determined using the controller interval counter i. In a first interval of counter i=0, the method proceeds to step S415, where the controller pressure p _PC,0 Is set to the value p determined in step S140 _P 。

For the next interval (i>0) And with step S416, the controller pressure p _PC,0 Take the subsequent controller interval as stored in step S465 and use p _PC,i And (3) drawing. This gives the advantage that at the controller pressure p _PC,0 The last generated value in the previous controller interval is then always received. This avoids trailer brake signal peaks between the brake intervals, which peaks would reduce driving comfort.

With step S420, in steps S415, S416, the 3-point controller is based on the controller pressure p _PC,0 To adjust the pressure value.

Returning to step S406, the lower coupling force F will now be described in detail _C,L And upper coupling force F _C,L A defined coupling force strap. Both of these values are negative (because they are blocking the vehicle) and require operation of the 3-point controller.

Lower coupling force F _C,L Indicating a value that should not be lowered because this may cause the vehicle 10 to become unstable due to the applied forces and the resulting yaw moment about the vertical vehicle axis. The value is stored in the ECU and may Different for different vehicle configurations. For example, a lightweight vehicle may not be able to withstand the same force/yaw moment as a higher weight vehicle 10. The same applies depending on the track or the wheel width, which also affects the stability of the vehicle.

Upper coupling force F _C,L Indicating a value that should not be exceeded because brake actuation should be stopped before the coupling force is zero. The driver demands that the trailer is allowed to slide, for example, when the vehicle combination 1 approaches a road intersection. This means that a small coupling force is acceptable.

The 3-point controller checks the actual coupling force F with steps S420, S435 and S437 _C,actual Against the under-coupling force F _C,L And upper coupling force F _C,L A value of the defined coupling force band.

If the actual coupling force F _C,actual In the coupling force band, step S430 sets the controller pressure p _PC,i＝ p _PC,0 This means that the pressure value determined in step S415 or S416 is taken without pressure adjustment.

If, as checked in step S435, the actual coupling force F _C,actual Lower than the lower coupling force F _C,L Branch B436 is taken and step S438 sets the controller pressure increase, where Δp _PC ＝ΔP _PC,set 。ΔP _PC,set The value of (2) is stored in the ECU and is 15kPA. This means that the pressure will increase to increase the braking force on the trailer.

If step 435 is not satisfied, the actual bond force F _C,actual Exceeding the upper coupling force F _C,U Branch B437 and step S439 set the controller pressure increase, where Δp _PC ＝-ΔP _PC,set . This means that the pressure will be reduced to reduce the braking force on the trailer.

The method then proceeds in two parallel branches to steps surrounded by a dashed line 440, which are used to apply the shot.

After branch B436, if the injection parameter SP is to be entered in step S405 _IS Set to 1 (indicating injection start), step S441 results in proceeding to step S445. Otherwise, the method proceeds to step 451 without applying injection. At the step ofIn step S445, an injection parameter is set to define a time-controlled pressure increase, wherein for a duration t _IS ＝t _IS1 ，ΔP _IS ＝ΔP _IC . Value DeltaP _IC,set And time t _IS1 Is stored in the CU and is 100kpa and 0.05s.

After branch B437, if the injection parameter SP is to be entered in step S405 _IS Set to 1 (indicating injection start), step S442 results in proceeding to step S446. Otherwise, the method proceeds to step 451 without applying injection. In step S446, an injection parameter is set to define a time-controlled injection pressure increase, wherein for a duration t _IS ＝t _IS2 ，ΔP _IS ＝-ΔP _IC,set (reduced due to negative sign). Value DeltaP _IC,set And time t _IS2 Is stored in the CU and is 100kpa and 0.1s. As with step S445, the duration in this step is longer due to the fact that the response time of the trailer brake system is longer when the pressure is reduced. This is balanced by the longer duration of the injection.

Both steps S445 and S446 are continued in step S450, wherein the pressure value is set to:

when the injection is started, the injection pressure P _IS Calculated from the following

p _IS ＝p _PC,0 +Δp _PC +Δp _IS (E9.1)

This means that the pressure p is controlled by the controller _PC,0 (as set in step S415 or step S416), the controller pressure increases by Δp _PC (as set in step S438 or step S439) and injection pressure increase ΔP _IS The sum (as set in step S445 or step S446) receives the pressure for the injection.

In addition, the controller pressure p _PC,i Calculated from the following

P _PC,i ＝p _PC,0 +Δp _PC (E9.2)

This means that the pressure p is controlled by the controller _PC,0 (as set in step S415 or step S416), the controller pressure increases by Δp _PC (as in step S438 or step S439)Arranged) but without an increase in injection pressure deltap _IS Receives a pressure for the controller pressure.

In step S455, the ECU generates a trailer brake signal TBS, in which, for a duration t _IS Inner trailer brake signal p _TBS ＝p _IS . This step covers the trailer brake signal TBS (in fig. 2) generated in step S140.

If the injection is not started in step S441 or S442, the controller pressure p is calculated in step S451 by the following formula _PC,i

P _PC,i ＝p _PC,0 +Δp _PC (E9.3)

After one of step S430 or step S451 or step S455, the method proceeds to step S460, which generates the trailer brake signal p determined in step S430, step S450 or step S451 _TBS ＝P _PC,i . The brake signal is not time controlled and is thus held until the next controller interval.

The final value of the trailer brake signal TBS is then saved in the ECU for consideration in the next controller interval in step S416, using step S465.

Alternatively, step S430 may cause the method to proceed to step S465 because there is no pressure increase and the trailer brake pressure generated in step S140 (see fig. 2) is still maintained.

In step S475, the controller interval counter i is incremented by 1 to characterize the subsequent interval requested in step S410.

In step S480, for t ₀ Controlling the timer value if the timer value t ₀ Below 4S, the method proceeds to loop L481, which includes step S485, so that the process waits for t ₃ =0.5S to enable the ECU to determine the actual coupling force F as described with step S300 _C,actual And returns.

In step S145, the process waits for 0.75 seconds to enable the ECU to determine the actual coupling force F as described with step S300 _C,actual And then returns to before step 410.

If it isIn step S480, a timer value t ₀ Beyond 4S, step S490 aborts the sub-process S400 and returns to the main method M100 depicted in fig. 2.

In summary, the sub-process S400 continuously adjusts the trailer brake signal TBS by applying a 3-point controller and optional injection until a time of 4S is reached. At the same time, the process passes several controller intervals, whereby the subsequent interval is based on the trailer brake signal TBS generated in the previous interval.

Returning now to fig. 2, step S150 saves the last value of the trailer brake signal in the ECU for consideration in the next brake interval in step S132.

Thereafter, in step S475, the brake interval counter c is incremented by 1 to characterize the subsequent interval requested in step S125.

As already mentioned, a timer value T is provided ₀ To ensure that brake actuation does not start for more than 5s. To avoid a sudden drop of the trailer brake signal TBS (and brake actuation) to zero, the sub-process S400 is aborted after 4 seconds. The remaining 1s time is used to reduce the trailer brake signal TBS to zero before 5 seconds elapse.

Based on the last trailer brake signal TBS and the cycle time of the ECU (which is the time required to perform a simple processor operation in the ECU), step S156 calculates the ramp pressure drop Δp according to the following equation _R ：

Thereby making it possible to

·t _C Is the cycle time of the processing in the ECU, which is 50ms

·t _R Is a ramp time of 1s

·P _TBV Is the final trailer brake signal TBS

For a final trailer brake signal TBS of 100kPa, equation E10 will determine a ramp pressure drop Δp of 4kPa _R 。

Thus, loop L161 and step S16 as long as step S160 does not indicate that the trailer brake signal TBS is zero2 is repeated to generate a signal with delta p _R A reduced trailer brake signal TBS. The loop L161 repeats and returns to before step S160 until the trailer brake signal TBS is zero.

As long as there is an initiation signal (wherein SP _CA =1), the process continues to loop L166, where step S170 includes t ₂ A waiting period of=1s, and returns to before step S121 to continue with the next braking interval.

If step S165 determines that there is no start signal, step S175 checks whether the off condition is satisfied so that the method ends with step S180. We have selected ignition OFF (OFF) in step S175.

Fig. 7 schematically depicts the result of the method according to the invention.

The horizontal axis depicts the time that the method is proceeding.

The vertical axis represents two parts:

_· the upper part being under pressure p _TBS Depicting trailer brake signal TBS

The lower part depicts the measured coupling force F as determined with step S300 _C,actual Comprises F _C,U And F _C,L A defined coupling force strap, thereby F _C,U = -2000N and F _C,L＝ -4000N. Measured coupling force F _C,actual Is smoothed as if the curve would exhibit a 50ms cycle time of constant oscillation.

As best seen with graph a, in step S121, t ₀ Is set to zero. Since this is the first braking interval of c=0, step S131 determines the subsequent preceding pressure value P generated in step S135 _FIS . During the waiting period in step S145, the pilot pressure P is maintained _P . Then, the process advances to step S400.

Based on the actual pressure, based on the determination in steps S438, S445, S450, a pressure with p is applied with step S455 _IS Is a part of the injection of the laser beam. Then, in step S460, the controller pressure P is generated based on the determination in step S438 _PC . Steps S438, S445, S450 at coupling force F _C,actual Below F _C,L The positive pressure increase is transmitted. This process is repeated until the joining force F _C,actual Higher than F _C,L Until that point. Then, a negative pressure increase is determined in steps S439, S446, S450 to generate an injection p in step S455 _IS And generates a controller pressure P in step 460 _PC 。

This is provided until a timer t in step S480 ₀ The 4s is reached and the 3-point controller is terminated. Next, in step L161/s162, the trailer brake signal TBS and the pressure p _TBS Descending. After 5s (generally, or 1 second falling ramp), the pressure p _TBS Will be zero. Then, a waiting period of 1S is applied with step S170.

If the enable signal remains active, the process starts again with the next braking interval (c=1), but then with the signal from the previous interval P, via step S132 _PC,1 And apply priming, firing and pressure control as described previously.

At the time indicated by the broken line X, the coupling force F _C,actual Within the coupling force band, such that the trailer brake signal TBS and the pressure p _TBS Remain unchanged until reaching 4s again and starting downhill.

Claims (14)

1. A control system for controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination, the control system comprising a vehicle control unit and being configured to:

determining a coupling force between the vehicle and the trailer; and

generating and outputting a control signal for controlling the operation of the trailer brake system according to the determined coupling force;

wherein the control system is configured to:

controlling operation of the trailer brake system in accordance with a master control strategy in dependence on the determined coupling force being within a coupling force range; and

The operation of the trailer brake system is controlled in accordance with one of one or more auxiliary control strategies depending on the determined coupling force being outside the coupling force range.

2. The control system of claim 1, configured to compare the determined coupling force to an upper coupling force threshold and a lower coupling force threshold to determine whether the coupling force is within the coupling force range.

3. The control system of claim 2, wherein the lower coupling force threshold corresponds to a coupling force at or near a level such that the applied force and/or the resulting yaw moment exceeds an acceptable level for the vehicle-trailer combination.

4. A control system according to claim 3, wherein the acceptable level of applied force and/or yaw moment depends on the mass of the vehicle, the track size of the vehicle or trailer; and one or more of the wheel widths of the vehicle or trailer.

5. A control system according to claim 2 or any claim dependent on claim 2 wherein the upper coupling force is provided at a level that ensures that actuation of the trailer brake system is prevented until the coupling force is reduced to zero.

6. A control system according to claim 2 or any claim dependent on claim 2, configured to control operation of the trailer brake system in accordance with a first auxiliary control strategy in accordance with the determined coupling force being below the lower coupling force threshold; wherein the first auxiliary control strategy comprises increasing a pressure level of the trailer brake system to increase a braking force applied to the trailer.

7. A control system according to claim 2 or any claim dependent on claim 2, configured to control operation of the trailer brake system in accordance with a second auxiliary control strategy in accordance with the determined coupling force exceeding the upper coupling force threshold; wherein the second auxiliary control strategy comprises reducing a pressure level of the trailer brake system to reduce a braking force applied to the trailer.

8. A control system according to any preceding claim configured to determine the coupling force in accordance with one or more of:

traction applied to wheels of a vehicle provided by an engine and transmission of the vehicle;

inertial forces due to acceleration or deceleration of the vehicle-trailer combination;

Tilting forces due to tilting of the vehicle-trailer combination;

the mass of the vehicle and/or trailer;

air resistance; and

rolling resistance.

9. A control system according to any preceding claim, wherein the trailer brake system comprises a hydraulic brake system and the control system is configured to control oil pressure of one or more fluid lines of the hydraulic brake system.

10. The control system of any one of claims 1 to 8, wherein the trailer brake system comprises a pneumatic brake system and the control system is configured to control gas pressure for one or more gas lines of the pneumatic brake system.

11. A control system according to any preceding claim configured to determine a coupling force associated with a coupling between the vehicle and the trailer from measurements of operating parameters of a transmission of the vehicle-trailer combination.

12. A brake system comprising and/or being controllable by a control system as claimed in any preceding claim.

13. An agricultural vehicle coupleable to a trailer to form a vehicle-trailer combination and comprising and/or being controllable by a control system according to any one of claims 1 to 11.

14. A method for controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination, comprising:

determining a coupling force between the vehicle and the trailer; and

generating and outputting a control signal for controlling the operation of the trailer brake system according to the determined coupling force;

wherein the method comprises the following steps:

controlling operation of the trailer brake system in accordance with a master control strategy in dependence on the determined coupling force being within a coupling force range; and

the operation of the trailer brake system is controlled in accordance with one of one or more auxiliary control strategies depending on the determined coupling force being outside the coupling force range.