GB2581777A

GB2581777A - A control system and method for controlling operation of a powertrain of a vehicle

Info

Publication number: GB2581777A
Application number: GB1902246.6A
Authority: GB
Inventors: Abenojar Jesus
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2019-02-19
Filing date: 2019-02-19
Publication date: 2020-09-02
Anticipated expiration: 2039-02-19
Also published as: GB201902246D0; GB2581777B

Abstract

A control system to control a powertrain comprising a combustion engine, an electric motor, and a transmission. The system is configured to determine a currently selected gear 502, determine a rotational speed of the transmission 503 and whether said speed is within a predetermined range associated with the currently selected gear 504, and in dependence on the rotational speed being within the range, determine torque values for the combustion engine and electric motor 505. A torque output is then provided based on these values 506. Preferably, the rotational speed is determined to be within the predetermined range based on stored data related to frequency bands in which parts of the powertrain are caused to resonate. The system may further determine a torque demand 501 and determine the torque values based on this. A slip value may also be determined, wherein the system causes a clutch to slip by an amount depending on the slip value. A further independent claim relates to outputting a torque ratio based on a determined total torque demand, a current gear, and rotational speed of a transmission corresponding to a frequency of the combustion engine.

Description

A CONTROL SYSTEM AND METHOD FOR CONTROLLING OPERATION OF A POWERTRAIN OF A VEHICLE

TECHNICAL FIELD

The present disclosure relates to a control system and method for controlling operation of a powertrain of a vehicle, a powertrain, a vehicle and a non-transitory computer readable medium. In particular, but not exclusively it relates to a control system and method for controlling operation of a powertrain of a road vehicle such as a car.

BACKGROUND

Powertrains of vehicles are generally the source of unwanted vibrations. The vibrations may be perceptible, and an annoyance, to occupants of the vehicle. The vibrations may also have an adverse effect on the useful life of some components of the vehicle.

It is known to dampen vibrations caused by rotating shafts by providing a mass damper that rotates with the shaft. However, these add weight to a vehicle and only act to mitigate vibrations over a narrow frequency range.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control system, a powertrain, a vehicle a method and a non-transitory computer readable medium as claimed in the appended claims.

According to an aspect of the invention there is provided a control system comprising at least one controller for controlling operation of a powertrain of a vehicle, in which the powertrain comprises an internal combustion engine, an electric motor and a transmission, wherein the control system is configured to: determine a currently selected gear of the transmission; determine a rotational speed of the transmission; determine if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed being within a predetermined range associated with the currently selected gear, determine a first torque value for the internal combustion engine and a second torque value for the electric motor; cause the internal combustion engine to provide a first torque output dependent on the first torque value; and cause the electric motor to provide a second torque output dependent on the second torque value.

This provides the advantage that, where the rotational speed with the currently selected gear corresponds to a frequency band comprising a resonant frequency of a part of the powertrain or another part of the vehicle, the first torque output and the second torque output may be arranged to minimize excitation of vibrations in that part. For example, the rotational speed corresponds to a harmonic component of torque generated by the internal combustion engine and when that harmonic component comprises a frequency that is similar to a resonant frequency of a part of the vehicle, the first torque output by the engine may be reduced and thereby reduce the vibration within that part.

Optionally, the control system comprises at least one electronic processor having an electrical input for receiving a signal indicative of a rotational speed of transmission; and at least one electronic memory device electrically coupled to the at least one electronic processor and having instructions stored therein, the at least one processor being configured to access the at least one memory device and execute the instructions stored therein such that it is operable to: determine the currently selected gear of the transmission; determine the rotational speed of the transmission; determine if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed with the currently selected gear being within a predetermined range associated with the currently selected gear, determine a first torque value for the internal combustion engine and a second torque value for the electric motor; cause the internal combustion engine to provide the first torque output dependent on the first torque value; and cause the electric motor to provide the second torque output dependent on the second torque value.

Optionally, the control system is configured to determine if the rotational speed is within the predetermined range associated with the currently selected gear by determining from stored data if the rotational speed with the currently selected gear corresponds to a frequency band in which a part of the powertrain is caused to resonate.

Optionally, the control system is configured to determine the first torque value and/or the second torque value in dependence on a predetermined relationship.

Optionally, the control system is configured to determine the first torque value and/or the second torque value by retrieving stored data corresponding to the rotational speed of the transmission and the currently selected gear. This provides the advantage that the first torque value and the second torque value may be rapidly determined with minimal need of processing.

Optionally, the control system is configured to: determine a torque demand; and determine the first torque value and/or the second torque value in dependence on the torque demand.

This provides the advantage that, where a torque demand varies, the current torque demand may be met.

Optionally, the first torque value and the second torque value are indicative of a torque ratio; and the first torque output and the second torque output are caused to be in said torque ratio.

This provides the advantage that the amplitude of vibrations excited by the internal combustion engine and/or the electric motor may be reduced so that they are within an acceptable limit.

Optionally, the control system is configured to: determine a slip value in dependence on the rotational speed and a torque input to the transmission; and cause a clutch of the powertrain to slip by an amount that depends on the slip value. When the first torque provided by the internal combustion engine and the second torque provided by the electric motor have been adjusted to minimize excitation of resonances within the vehicle, the vibrations may still have amplitudes above acceptable limits. However, slipping the clutch provides the advantage that the vibrations may be further reduced so that they are within the acceptable limits.

Optionally, the control system is configured to: determine the slip value by retrieving stored data corresponding to the rotational speed and the currently selected gear. This provides the advantage that slip values may be determined rapidly with minimal processing being necessary.

Optionally, the control system is configured to select the clutch to be slipped from a plurality of clutches of the powertrain in dependence on the rotational speed and the currently selected gear. This provides the advantage of being able to optimize the reduction in vibrations and/or minimize the power lost by slipping the clutch.

According to another aspect of the invention there is provided a powertrain comprising the control system of any one of the previous paragraphs, an internal combustion engine, an electric motor and a transmission.

Optionally, the transmission comprises an automatic transmission. This provides the advantage that where clutch slipping is used to dampen vibration, this may be controlled by a controller of the automatic transmission.

Optionally, the powertrain comprises at least one clutch; the control system is configured to cause the at least one clutch to slip in dependence on the rotational speed and the currently selected gear; and the at least one clutch is configured to provide an operational connection between a first part of the powertrain and a second part of the powertrain, the first part and the second part being items selected from the group: the internal combustion engine; the electric motor; a gear train of the transmission; and a shaft connecting the transmission to one or more road wheels. This provides the advantage that vibrations may be further reduced so that they are within the acceptable limits.

In some embodiments, a harmonic component of torque generated by the internal combustion engine corresponds to a resonance frequency of a part of the powertrain, and the first torque value and the second torque value are arranged to minimize the torque output of the internal combustion engine while meeting a torque demand. This provides the advantage that vibrations excited in said part of the powertrain may be minimized.

According to a further aspect of the invention there is provided a vehicle comprising the powertrain of any one of the previous paragraphs.

According to yet another aspect of the invention there is provided a method of controlling a powertrain of a vehicle, the powertrain comprising an internal combustion engine, an electric motor and a transmission, and the method comprising: determining a currently selected gear of the transmission; determining a rotational speed of the transmission; determining if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed being within a predetermined range associated with the currently selected gear, determining a first torque value for the internal combustion engine and a second torque value for the electric motor; causing the internal combustion engine to provide a first torque output dependent on the first torque value; and causing the electric motor to provide a second torque output dependent on the second torque value.

This provides the advantage that, where the rotational speed with the currently selected gear corresponds to a frequency band comprising a resonant frequency of a part of the powertrain or another part of the vehicle, the first torque output and the second torque output may be arranged to minimize excitation of vibrations in that part.

Optionally, said determining if the rotational speed is within the predetermined range associated with the currently selected gear comprises determining from stored data, if the rotational speed with the currently selected gear corresponds to a frequency band in which a part of the powertrain is caused to resonate. This provides the advantage that it may be rapidly determined if the rotational speed is within a predetermined range with minimal need of processing.

Optionally, the method comprises determining the first torque value and/or the second torque value in dependence on a predetermined relationship.

Optionally, the method comprises determining the first torque value and/or the second torque value by retrieving stored data corresponding to the rotational speed of the transmission. This provides the advantage that the first torque value and the second torque value may be rapidly determined with minimal need of processing.

Optionally, the method comprises: determining a torque demand; and determining the first torque output and/or the second torque output in dependence on the torque demand.

Optionally, the method comprises: determining a slip value in dependence on the rotational speed, the currently selected gear and the torque demand; and causing a clutch of the powertrain to slip by an amount that depends on the slip value. This provides the advantage that vibrations may be further reduced so that they are within the acceptable limits.

Optionally, the method comprises: determining if the rotational speed with the currently selected gear and the first torque output and/or the second torque output is likely to cause a vibration amplitude to be above a threshold level; and determining the slip value in dependence on the rotational speed with the currently selected gear and the first torque output and/or the second torque output being likely to cause a vibration amplitude above a threshold level. This provides the advantage that even when the first torque output and the second torque output have been adjusted to minimize an unwanted vibration, but the amplitude of the vibration is still above a threshold level, the amplitude of the vibration may be further reduced so that it is below the threshold level.

Optionally, the method comprises selecting at least one clutch to be slipped from a plurality of clutches of the powertrain in dependence on the rotational speed, and causing the at least one clutch to be slipped. This provides the advantage of being able to optimize the reduction in vibrations and/or minimize the power lost by slipping the clutch.

In some embodiments, a harmonic component of torque generated by the internal combustion engine corresponds to a resonance frequency of a part of the powertrain, and the first torque value and the second torque value are arranged to minimize the torque output of the internal combustion engine. This provides the advantage that vibrations excited in said part of the powertrain may be minimized.

According to a further aspect of the invention there is provided a non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of a method according to any one the previous paragraphs.

According to yet another aspect of the invention there is provided a control system comprising at least one controller for controlling operation of a powertrain of a vehicle, in which the powertrain comprises an internal combustion engine, an electric motor and a transmission, wherein the control system is configured to: determine a total torque required to be produced by the powertrain; determine a currently selected gear of the transmission; determine a rotational speed of the transmission; determine, from stored data, if the rotational speed and the currently selected gear correspond to a frequency at which a part of the powertrain is caused to resonate; cause the internal combustion engine to provide a first torque output; cause the electric motor to provide a second torque output; wherein the combination of the first torque output and the second torque output provides the total torque required to be produced; and the first torque output is minimized in dependence on the frequency being a harmonic component of torque of the internal combustion engine.

According to a further aspect of the invention there is provided a control system comprising at least one controller for controlling operation of a powertrain of a vehicle, in which the powertrain comprises an internal combustion engine, an electric motor and a transmission, wherein the control system is configured to: determine a total torque demand; determine a currently selected gear of the transmission and a rotational speed of the transmission corresponding to a frequency of the internal combustion engine; retrieve stored data corresponding to the currently selected gear and the rotational speed; cause the internal combustion engine to provide a first torque output in dependence on the retrieved stored data; cause the electric motor to provide a second torque output in dependence on the retrieved stored data; wherein the combination of the first torque output and the second torque output meets the total torque demand; and the stored data is configured to cause the ratio of the first torque output to the second torque output to be dependent on whether or not the frequency is a frequency at which a part of the powertrain is caused to resonate.

Optionally, the control system is configured to: at a first rotational speed corresponding to a frequency of pulses in the first torque output at which a part of the powertrain is caused to resonate, cause the combination of the first torque output and the second torque output to meet the total torque demand, while minimizing the first torque output; and cause the combination of the first torque output and the second torque output to meet the total torque demand, while minimizing the second torque output at a second rotational speed that is greater than the first rotational speed. For example, in the case of the engine being a four-cylinder engine, it may generate torque comprising pulses at a frequency that is double the rotational speed of the input to the transmission. If the vehicle has a component that resonates at this frequency, then minimizing the torque output by the engine provides the advantage that the excitation of the resonance may be minimized.

Optionally, the control system is configured to: determine a slip value in dependence on the rotational speed and a torque input to the transmission; and cause a clutch of the powertrain to slip by an amount that depends on the slip value.

Optionally, the control system is configured to: determine the slip value by retrieving stored data corresponding to the rotational speed and the currently selected gear.

Optionally, the control system is configured to select the clutch to be slipped from a plurality of clutches of the powertrain in dependence on the rotational speed and the currently selected g ear.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic plan view of a vehicle according to an embodiment of the invention; Fig. 2 shows a graph of frequency response curves for the rear prop-shaft in combination with gears of the gear train that are driving the rear prop-shaft; Fig. 3 shows a graph of the frequency response curve for the rear prop-shaft in combination with the gear train when the transmission is in its sixth gear, and graphs illustrating an example of the operation of the powertrain control system as the vehicle is accelerated in sixth gear by a constant mean torque provided by a combination of torque generated by the engine and the electric motor; Fig. 4 shows schematic diagram of the powertrain control system; Fig. 5 shows a flowchart illustrating a first method embodying the present invention and performable by the powertrain control system; Figs. 6 and 7 show examples of processes that may be performed within the method of Fig. 30 5; Fig. 8 shows a flowchart illustrating a second method embodying the present invention and performable by the powertrain control system; Fig. 9 shows an example of processes that may be performed within the method of Fig. 8; Fig. 10 shows a flowchart illustrating a third method embodying the present invention and performable by the powertrain control system; Fig. 11 shows a portion of a look-up table storing data for use in the method of Fig. 10; and Fig. 12 shows a flowchart illustrating a fourth method embodying the present invention and performable by the powertrain control system.

DETAILED DESCRIPTION

A vehicle 101, a powertrain 126, a control system 126 and a method 500, 800 in accordance with embodiments of the present invention are described herein with reference to the accompanying Figs. 1 to 12.

The vehicle 101 is shown in a schematic plan view in Fig. 1. In the present embodiment, the vehicle 101 is a road vehicle having four road wheels 102: two rear wheels 102A and two front wheels 102B. The vehicle 101 is a four-wheel drive vehicle 101 but alternative vehicles embodying the present invention may be two-wheel drive, with either front wheels 1028 or rear wheels 102A being driven.

The vehicle 101 is a hybrid vehicle comprising both an internal combustion engine 103 (referred to below simply as the engine 103) and an electric motor 104 configured to provide torque for driving the vehicle 101. Operation of the engine 103 is controlled by an engine control unit (ECU) 123 and operation of the electric motor 104 is controlled by an electric motor controller (EMC) 124. Torque generated by the engine 103 and the electric motor 104 is provided to a transmission 105 via a transmission input shaft 106. In the present arrangement, the engine 103 has an output shaft 107 which is connectable to the transmission input shaft 106 by a clutch 108, and therefore the engine 103 may be disconnected from the transmission input shaft 106 by disengaging the clutch 108. For example, the clutch 108 may be disengaged at low speeds of the vehicle 101 to enable the vehicle 101 to be driven by the electric motor 104 while the engine 103 is maintained in an inactive state.

The electric motor 104 comprises a stator 110, within which is located a rotor 109 that is fixed to the transmission input shaft 106. A second clutch 111, which may be referred to as a launch clutch, connects the transmission input shaft 104 to a gear train 112. As is known in the art, the gear train 112 comprises a plurality of different gearing arrangements to enable a selectable gear ratio to be provided between the transmission input shaft 104 and a transmission output shaft 113. In the present embodiment the transmission 105 is an automatic transmission having odd numbered gears and even numbered gears and the second clutch 111 is a double clutch enabling either one of the odd gears or one of the even gears to be selected. Gear selection is performed under the control of a transmission control unit 114. In an alternative embodiment, the transmission 105 is an automatic transmission having only a single clutch 111.

The transmission output shaft 113 is connected via a transfer case 115 to a rear prop-shaft 116, which is configured to drive rear driveshafts 117 via a rear differential 118, and each of the two rear driveshafts 118 is configured to drive one of the two rear wheels 102A. The transmission output shaft 113 is also connected via a chain drive 119 within the transfer case 115 to a front prop-shaft 120. The front prop-shaft 120 is configured to drive front driveshafts 121 via a front differential 122, and each of the two front driveshafts 121 is configured to drive one of the two front wheels 102B.

The front prop-shaft 120 may be operatively connected to the output shaft 113 of the transmission 105 by a releasable connection mechanism, such as a clutch 131, so that the vehicle 101 may be operated in a four-wheel-drive mode when the clutch 131 is engaged or a two-wheel-drive mode, in which only the rear wheels are driven, when the clutch 131 is disengaged.

The vehicle 101 further comprises a powertrain control system 125 which is arranged to provide overall control of the powertrain 126, including the engine 103, the electric motor 104 and the transmission 105. Although the powertrain control system 125, the transmission control unit 114, the electric machine controller 124 and the engine control unit 123 are shown as separate entities in Fig. 1, it should be appreciated that they may all be embodied within a single processing unit or their functions may be distributed over several processing units.

The powertrain control system 125 is arranged to receive input signals indicative of a torque demand, i.e. a request for an amount of torque that is required to be provided by the powertrain 126 to drive the vehicle 101. In the present embodiment, the vehicle 101 comprises an accelerator pedal 127 and an associated accelerator pedal sensor 128, to enable a user of the vehicle 101 to provide inputs indicating a torque demand. However, in some alternative embodiments, in which the vehicle 101 is self-driving or comprises a driver assistance system, such as adaptive cruise control, the input signals indicative of a torque demand may be received from a controller configured to control the speed of the vehicle 101 in response to sensor signals configured to sense the environment.

Depending upon the current speed of the vehicle 101 and the required torque, the powertrain control system 125 provides signals to cause the transmission 105 to change to a selected gear; to open one or more of the clutches 108, 111, 131; to cause the engine 103 to provide a first torque; and/or to cause the electric motor 104 to provide a second torque. For example, when the vehicle 101 is stationary or at low speeds, the powertrain control system 125 may cause the transmission control unit 114 to select a first gear; cause the clutch 108 to open to disengage the internal combustion 103 from the input shaft 106 of the transmission 105; and cause the electric motor 104 to provide a required torque, while keeping the engine 103 dormant. At higher speeds, the powertrain control system 125 may cause the transmission control unit 114 to select a suitable higher gear; cause the clutch 108 to close to connect the internal combustion 103 to the input shaft 106 of the transmission 105; and cause the engine 103 to provide all, or a large portion, of the torque that is required to be provided to the transmission 105, while the electric motor 104 may not be energised, or may provide only a portion of the required torque.

As is known, to enable the powertrain control system 125 to operate, it may receive input signals from many sensors located within the vehicle 101, but these sensors are generally not shown in Fig. 1. However, in the present embodiment, there is a sensor 129 configured to provide a signal indicative of the rotational speed of the input shaft 106 of the transmission to the powertrain control system 125.

During its operation, the engine 103 provides a mean average torque to the input shaft 106 of the transmission 105. However, the engine 103 comprises a number of cylinders 130, and the energy required for the engine 103 to produce torque is generated by combustion that periodically takes place in each of the cylinders 130. Consequently, the engine 103 produces torque that is momentarily increased as combustion takes place in a cylinder. i.e. the torque produced by the engine 103 includes a pulsed or harmonic component, so that the instantaneous torque provided by the engine oscillates about the mean average torque. For example, in the case of an engine having four cylinders 130, the torque produced by the engine 103 includes two pulses for each revolution of its output shaft 107. The amplitude of the pulses is proportional to the mean torque provided by the engine 103. i.e. when the engine is working hard and producing a large amount of torque the harmonic component of the torque is proportionately large.

Similarly, during its operation, the torque produced by the electric motor 104 includes a pulsed, or harmonic, component that has a frequency depending on the speed of rotation of its rotor 109 (i.e. the speed of rotation of the transmission input shaft 106) and the number of poles on its stator 110 and the number of slots on its stator 110 and rotor 109. The number of slots on the stator 110 and rotor 109 are sufficiently large so that for a given rate of rotation of the transmission input shaft 106 the pulses produced by the electric motor 104 are at a much higher frequency than the pulses produced by the engine 103.

Operation of the engine 103 and/or the electric motor 104 typically causes parts of the vehicle 101 to vibrate. If the harmonic component of the torque generated by the engine 103 or the electric motor 104 comprises a frequency within a frequency band that includes a resonant frequency of one of those parts, then that part could potentially be caused to vibrate excessively. The part may be a panel of the body of the vehicle 101 or a portion of its powertrain 126, such as the front prop-shaft 120 or the rear prop-shaft 116 in combination with the gears of the gear train 112 that are driving the rear prop-shaft 116.

By way of example, a graph of frequency response curves for the rear prop-shaft 116 in combination with gears of the gear train 112 that are driving the rear prop-shaft 116 is shown in Fig. 2. Three curves are shown on the graph: a first curve 201 shown in a dashed line illustrates the frequency response when a fourth gear of the transmission 105 is selected; a second curve 202 shown in a dotted line illustrates the frequency response when a fifth gear of the transmission 105 is selected; and a third curve 203 shown in an unbroken line illustrates the frequency response when a sixth gear of the transmission 105 is selected. Each of the curves 201, 202 and 203 illustrates the second order harmonic of the rotational speed, and also shows that a resonance occurs when the speed of rotation of the transmission input shaft 106 is between 2700 and 3200 RPM (revolutions per minute).

For example, the third curve 203 shows that this portion of the powertrain resonates at a frequency of about 6000 per minute (i.e. about 100 Hz) when the input shaft 106 rotates at about 3000 RPM. At this speed of rotation, the engine 103 generates pulses of torque at a rate of 6000 per minute and therefore it is efficient at exciting the resonance in this portion of the powertrain. In contrast, the electric motor 104 is configured to generate torque with pulses at a much higher frequency than the engine 103 for a given rate of rotation of the input shaft 106. Consequently, torque provided by the electric motor 104 at a rotational speed of 3000 RPM has relatively little effect in exciting the resonance. The powertrain control system 125 makes use of this fact by reducing the torque generated by the engine 103 and increasing the torque generated by the electric motor 104 at rotational speeds neighbouring the rotational speed that corresponds to the resonant frequency.

This is further illustrated in the graphs 301, 302 and 303 of Fig. 3. The graph 301 shows the frequency response curve 203 for the rear prop-shaft 116 in combination with the gear train 112 when the transmission 105 is in its sixth gear. A line 304 representing a threshold amplitude is also shown on the graph 301. At a range of speeds of rotation between a lower threshold speed of rotation 305 and a higher threshold speed of rotation 306, the amplitude of vibration in this part of the powertrain exceeds the threshold amplitude 304. The threshold amplitude 304 therefore defines a range of speeds of rotation of the transmission input shaft 106 over which the engine 103 is likely to cause excessive vibration.

The graphs 302 and 303 illustrate an example of the operation of the powertrain control system as the vehicle 101 is accelerated in sixth gear by a constant mean torque provided by a combination of torque generated by the engine 103 and the electric motor 104. Graph 302 shows the rotational speed of the transmission input shaft 106 as it increases with time, and graph 303 shows torque plotted against time over the same period as graph 302. In graph 303, the total torque, which is equal to a torque demand, is illustrated by an unbroken line 307; torque provided by the engine 103 is illustrated by dotted line 308; and torque provided by the electric motor 104 is illustrated by dashed line 309.

Initially in this example, the engine 103 is providing most of the torque that is required and the electric motor 104 is providing a relatively small amount. However, when the speed of rotation of the transmission input shaft 106 reaches the lower threshold speed of rotation 305 at time t1, the torque 309 provided by the electric motor 104 is increased and the torque 308 provided by the engine 103 is decreased by a similar amount, so that the total torque 307 remains substantially constant. When the speed of rotation of the transmission input shaft 106 reaches the higher threshold speed of rotation 306 at time t2, the torque 309 provided by the electric motor 104 is decreased and the torque 308 provided by the engine 103 is increased by a similar amount, so that the total torque 307 once again remains substantially constant.

By reducing the contribution of the engine 103 between the time ti and the time t2 the amplitude of the pulses in the torque provided by the engine 103 are reduced and the degree of vibration produced in the rear prop-shaft 106 is maintained at a tolerable level. In the present example the torque 309 provided by the electric motor 104 is maximised during the period between times ti and t2 so that the torque 308 provided by the engine 103 may be minimised while maintaining the total torque 307 at the required level.

It will therefore be understood from this that at a first speed of rotation, between the thresholds of speed of rotation 305 and 306, the engine 103 is caused to produce a first torque output 310 and the electric motor 104 is caused to produce a second torque output 311, while at a slower second speed, below the lower threshold speed of rotation 305, the engine 103 is caused to produce a third torque output 312 that is greater than the first torque output 311 and the electric motor 104 is caused to produce a fourth torque output 313 that is lower than the second torque output 311. Thus, at the higher first speed of rotation between the lower and the higher thresholds of speed of rotation 305 and 306, the engine 103 is actually caused to generate less torque than when it is at the slower second speed of rotation, below the lower threshold 305, in order to avoid exciting excessive vibration in a resonating part.

To avoid excessive vibrations in this way, the powertrain control system 125 refers to stored data that defines rotational speed ranges associated with each selectable gear of the transmission 105 that are likely to cause an excessive amount of vibration in a part of the powertrain 126, or any other part of the vehicle 101. The stored data may also define a relationship between the torque of the engine 103 and the torque of the electric motor 104 that is to be used over each of the defined speed ranges. For example, the relationship may indicate a ratio of engine torque to motor torque that is to be used, or it may indicate that all possible torque should be provided by the engine 103, or all possible torque should be provided by the electric motor 104.

The powertrain control system 125 is shown schematically in Fig. 4. The control system 125 comprises an electronic processor 401 having an electrical input 402 for receiving signals and an electrical output 403 for outputting signals. The input 402 and output 403 may be embodied by one or more ports of one or more transceivers configured to provide communications over one or more data buses of the vehicle 101. The input 402 enables signals to be received from the sensor 129 that are indicative of a rotational speed of the transmission 105 and received from the accelerator pedal sensor 128 indicative of a torque demand.

The powertrain control system 125 also comprises an electronic memory device 404 electrically coupled to the electronic processor 401. The electronic memory device 404 stores instructions 405 which the electronic processor 401 is configured to execute so that it becomes operable to perform the functions of the powertrain control system 125 as described above in regard to Figs. 1 to 3 and below in regard to Figs. 4 to 9.

The electronic memory device 404 also stores data 406 defining at least one predetermined range of rotational speed of the transmission input shaft that is associated with at least one selectable gear of the transmission 105. Each predetermined range corresponds to a range of frequencies at which a part of the powertrain 126, such as a prop-shaft 116, 120, or another part of the vehicle 101 is likely to vibrate excessively due to resonance excited by either the engine 103 or the electric motor 104. The predetermined ranges may be determined from computer modelling and/or test bed measurements. The stored data 406 also defines values that enable the powertrain control system 125 to determine torque values for the engine 103 and the electric motor 104 to cause the torque output by the engine 103 and electric motor 104 to be reduced when the rotational speed of the transmission 105 is within a predetermined range.

Although Fig. 4 shows the powertrain control system 125 as having one electronic processor 401 and one electronic memory device 404, it will be appreciated that the powertrain control system 125 may comprise several electronic processors 401 and several electronic memory devices 404.

A flowchart illustrating a method 500 embodying the present invention and performable by the powertrain control system 125 is shown in Fig. 5. The method 500 is continuously performable during operation of the vehicle 101 in order to maintain vibration within the vehicle 101 within an acceptable level. At block 501 of the method 500 a torque demand is determined. For example, a torque required to be provided by the powertrain 126 may be determined from a signal received from an accelerator pedal sensor 128 or a controller configured to control speed of the vehicle 101. At block 502 of the method 500, a currently selected gear of the transmission 105 is determined. This information may be determined from signals provided by the transmission control unit 114.

At block 503 a rotational speed of the transmission is determined. This may be determined from signals received from the sensor 129 which senses rotational speed of the input shaft 106 of the transmission 105. At block 504 it is determined whether or not the rotational speed of the transmission 105 is within a predetermined range associated with the currently selected gear. An example of the processes that may be performed at block 504 are illustrated in Fig. 6. Initially at block 601 stored data corresponding to the rotational speed of the transmission and the currently selected gear is retrieved from a memory device 404. Then at block 602 it is determined whether the retrieved data indicates that the rotational speed with the currently selected gear corresponds to a frequency band in which a part of the powertrain 126, or another part of the vehicle 101, is caused to resonate.

If it does, a first torque value for the internal combustion engine and a second torque value for the electric motor are determined at block 505 of the method 500 illustrated in Fig. 5. As illustrated in Fig. 7, the process at block 505 may comprise determining the first torque value and the second torque value from stored data that corresponds to the rotational speed of the transmission and the currently selected gear. For example, data retrieved at block 601 (shown in Fig. 6) may indicate a ratio in which the first torque output by the internal combustion engine 103 and the second torque output by the electric motor 104 should be, in order to minimise vibrations caused by one or more resonances in part(s) of the vehicle 101. Thus, the first torque value and the second torque value may be calculated by splitting a torque demand according to the ratio.

Alternatively, the stored data retrieved at block 601 may simply indicate that the electric motor 104 should provide a specified torque, such as the smaller of: the torque demand; and a maximum torque that the electric motor 104 is capable of delivering. The first torque value for the internal combustion engine 103 is then calculated so that the torque output by the internal combustion engine 103 added to the torque output by the electric motor 104 provides a required torque (i.e. meets a torque demand).

Having determined the first torque value for the internal combustion engine 103 and the second torque value for the electric motor at block 505, the internal combustion engine 103 is caused to provide a first torque output dependent on the first torque value and the electric motor 104 is caused to provide a second torque output dependent on the second torque value at block 506, as shown in Fig. 5. For example, a signal indicative of the first torque value may be provided to the engine control unit 123 to cause it to control the engine 103 to provide the first torque output, and similarly a signal indicative of the second torque value may be provided to the electric motor controller 124 to cause it to control the electric motor 104 to provide the second torque output.

If it is determined at block 504 that the rotational speed is not within a predetermined range associated with the currently selected gear, the internal combustion engine 103 and the electric motor 104 may be caused to provide output torque that is determined in a standard or conventional manner to meet a torque demand. For example, at a constant moderately high speed, the engine 103 may provide most, or all, of the torque required to meet a torque demand. Thus, a third torque value is determined for the engine and a fourth torque value is determined for the electric motor 104 at block at block 507, and at block 508 the engine 103 is caused to provide a third torque output dependent on the third torque value and the electric motor 104 is caused to provide a fourth torque output dependent on the fourth torque value.

For example, a signal indicative of the third torque value may be provided to the engine control unit 123 to cause it to control the engine 103 to provide the third torque output, and similarly a signal indicative of the fourth torque value may be provided to the electric motor controller 124 to cause it to control the electric motor 104 to provide the fourth torque output. Typically, where possible, the engine 103 is caused to provide a third torque output equal to the torque demand and where the engine 103 cannot meet the torque demand alone, the electric motor 104 provides torque output to make up the difference between the third torque output and the torque demand.

Following the processes at block 506 or block 508, the processes at blocks 501 to 504 and either blocks 505 and 506 or blocks 507 and 508 are repeatedly performed.

A flowchart illustrating a second method 800 embodying the present invention and performable by the powertrain control system 125 is shown in Fig. 8. Several of the processes performed in the method 800 may be similar to those described above for the method 500 and they have been similarly labelled in Fig. 8. Thus, initially in method 800, at block 501 a torque demand is determined, at block 502 a currently selected gear is determined and a block 503 a rotational speed of the transmission is determined. At block 504 it is determined whether or not the rotational speed is within a predetermined range associated with the currently selected gear and if it is not, the internal combustion engine 103 and the electric motor 104 may be caused to provide output torque that is determined in a standard or conventional manner to meet a torque demand. Thus, a third torque value is determined for the engine 103 and a fourth torque value is determined for the electric motor 104 at block at block 507, and at block 508 the engine 103 is caused to provide a third torque output dependent on the third torque value and the electric motor 104 is caused to provide a fourth torque output dependent on the fourth torque value. The processes at blocks 501 to 504 are then repeated.

Alternatively, if it is determined at block 504 that the rotational speed is within a predetermined range associated with the currently selected gear, then at block 505 a first torque value for the engine 103 and a second torque value for the electric motor 104 are determined in dependence on the current torque demand, which was determined at block 501. At block 506 the internal combustion engine 103 is caused to provide a first torque output dependent on the first torque value and the electric motor 104 is caused to provide a second torque output dependent on the second torque value. The first torque value and the second torque value are selected to minimise resonances excited in the vehicle 101 by the engine 103 and the electric motor 104.

At block 801 it is determined whether or not the rotational speed with the currently selected gear and the first torque output and/or the second torque output is likely to cause a vibration amplitude to be above a threshold level. i.e. it is determined whether the engine 103 and/or the electric motor 104 are likely to excite an excessive vibration within the vehicle 101, even though the ratio of torque output by the engine 103 to that of the electric motor 104 has been adjusted to minimise the vibration. If it is determined at block 801 that the rotational speed with the currently selected gear and the first torque output and/or the second torque output is likely to cause a vibration amplitude to be above a threshold level, then a process at block 802 is performed. At block 802 a slip value, or target slip, is determined in dependence on the rotational speed, the currently selected gear and the torque demand. At block 803 a clutch 108, 111 or 131 of the powertrain is caused to slip by an amount that depends on the slip value. By allowing a clutch to slip, the harmonic characteristics of the powertrain 126 may be adjusted so that the degree of resonance in the powertrain is reduced.

The slip value is a function of the torque input to the clutch that is to be slipped and the current speed of rotation input into the transmission 105. The slip value may be quantified in terms of the portion of rotational speed that is lost across the clutch. In the present embodiment, the slip value is an absolute value, i.e. the input rotational speed of the clutch minus the output rotational speed of the clutch, but in alternative embodiments, the slip value may be a proportional amount, i.e. the difference between the input rotational speed and the output rotational speed divided by the input rotational speed.

The slip value may be determined at block 802 by retrieving stored data corresponding to: the current torque input to the clutch and a rotational speed band that includes the current rotational speed input into the transmission. Alternatively, the slip value may be determined at block 802 by retrieving stored data corresponding to: the current torque demand; the currently selected gear; and a rotational speed band that includes the current rotational speed of the transmission. The retrieved stored data may also comprise a value for a pressure that may be applied to the clutch to produce an amount of slip that approximates the slip value. The actual difference between the input rotational speed and the output rotational speed of the clutch is measured by sensors (such as sensor 129) in the drivetrain, and the pressure on the clutch may be adjusted from the retrieved value so that the measured difference matches the slip value. The stored data is predetermined from computer modelling and/or test bed measurements.

An example of the process that may be performed at block 803 is illustrated in the flowchart of Fig. 9. Initially at block 901 a clutch to be slipped is selected from a plurality of clutches 108, 111, 131 of the powertrain 126 in dependence on the rotational speed and the currently selected gear. The selection of the clutch to be slipped may be determined by retrieving stored data from a look-up table that corresponds to: a rotational speed band that includes the current rotational speed; and the currently selected gear. At block 902, the selected clutch is then caused to be slipped by an amount that depends on the slip value. Following the process at block 803, the processes at blocks 501 to 504 are then repeated.

The clutch chosen to be slipped may be selected to minimise the amount of torque that is lost, while causing vibration damping in the powertrain 126. The clutches that are to be slipped are predetermined by determining which torque source (i.e. the engine 103 or the electric motor 104) causes which parts of the powertrain 126 to resonate at each one of a plurality of bands of rotational speed of the transmission 105. Typically, the clutch to be slipped is located within the powertrain 126 between the torque source and the part that is caused to resonate at that rotational speed. For example, if the engine 103 is responsible for exciting a resonance in the powertrain 126, it might be most appropriate to cause a clutch 108 between the engine 103 and the electric motor 104 to slip so that none of the torque provided by the electric motor 104 is lost. If the electric motor 104 is responsible for exciting a resonance in the powertrain 126 it might be most appropriate to cause the clutch 111 between the electric motor 104 and the gear train 112 to slip. If the front prop-shaft is the part likely to resonate it might be most appropriate to allow a clutch 131 that engages the front prop-shaft to slip.

A flowchart illustrating a third method 1000 embodying the present invention and performable by the powertrain control system 125 is shown in Fig. 10. Several of the processes performed in the method 800 may be similar to those described above for the method 500 and they have been similarly labelled in Fig. 10. Thus, initially in method 1000, at block 501 a torque demand is determined, at block 502 a currently selected gear is determined and at block 503 a rotational speed of the transmission is determined. At block 1001, stored data is retrieved corresponding to the current rotational speed of the transmission input shaft 106 and the currently selected gear.

An example of stored data that might be retrieved at block 1001 is illustrated in Fig. 11. In the present embodiment, the stored data comprises a look-up table, a portion of which is illustrated in Fig. 11. The look-up table indicates which of the engine 103 and the electric motor 104 is to be used as the primary source of torque within each one of a plurality of bands of rotational speed for each of the selectable gears of the transmission 105. As illustrated in Fig. 11, when the sixth gear of the transmission 105 is selected, the engine 103 should be used as the primary source of torque within all bands of rotational speed except those corresponding to frequencies in the neighbourhood of the resonant frequency, i.e. between 2700 and 3199 RPM (revolutions per minute). In the bands of rotational speed between 2700 and 3199 RPM, the electric motor 104 should be used as the primary torque source instead of the engine 103, so that excitation of vibration caused by the engine 103 is reduced.

At block 1002 a first torque value for the engine 103 and a second torque value for the electric motor 104 are determined in dependence on the current torque demand determined at block 501 and in dependence on the data retrieved at block 1001. For example, the determination at block 1002 may be arranged to cause the ratio of torque output by the primary torque source to the other torque source to be maximised.

For example, when the primary torque source is the engine 103, a first torque value is determined to cause the engine 103 to provide a first torque output that is the smaller of: the torque demand; and a maximum torque output providable by the engine 103. The second torque value is determined to cause the electric motor 104 to provide a second torque output that is the difference between the first torque output and the torque demand. Therefore, the torque output by the electric motor 104 is minimised, while the torque demand is met.

Alternatively, for speeds of rotation of between 2700 and 3199 RPM, the primary torque source is the electric motor 104, and the second torque value is determined to cause the electric motor 104 to provide a second torque output that is the smaller of: the torque demand; and a maximum torque output for the electric motor 104. The first torque value is determined to cause the engine 103 to provide a first torque output that is the difference between the second torque output and the torque demand. Therefore, the torque output by the engine 103 is minimised, while the torque demand is met.

At block 1003 the internal combustion engine 103 is caused to provide a first torque output dependent on the first torque value and the electric motor 104 is caused to provide a second torque output dependent on the second torque value; the first torque output and the second torque output providing a total torque to meet the torque demand.

Following the process at block 1003, the processes at blocks 501 to 503 and 1001 to 1003 are repeatedly performed.

In alternative embodiments, the stored data retrieved at block 1001 may include values indicating a ratio of the first output torque for the engine 103 and the second output torque for the electric motor 104, rather than just indicating which should be the primary torque source.

For example, in some bands of rotational speed, the engine 103 may excite a resonance in one part of the vehicle 101 and the electric motor may excite a resonance in another part of the vehicle 101. In such a situation, the ratio of the first torque to the second torque defined by the stored data may effectively be a compromise to limit the amplitude each of the resonances.

A flowchart illustrating a fourth method 1200 embodying the present invention and performable by the powertrain control system 125 is shown in Fig. 12. The method 1200 is like method 1000 but additionally comprises the processes of blocks 801 to 803 as described above for method 800, following the process at block 1003. Thus, it is determined at block 801 whether or not the rotational speed with the currently selected gear and torque demand is likely to cause a vibration amplitude above a threshold level, even though the primary source of torque may have been selected to minimize vibration. If the rotational speed is likely to cause a vibration amplitude above the threshold level, at block 802 a slip value is determined in dependence on the rotational speed, the currently selected gear and the torque demand. A clutch 108, 111 and/or 131 of the powertrain 126 is then caused to slip by an amount that depends on the slip value at block 803. The processes at blocks 501 to 503, 1001 to 1003 and 801 are then repeated.

For purposes of this disclosure, it is to be understood that the control system(s)/controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the control system(s)/controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on one or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

The blocks illustrated in the Figs. 5 to 10 and 12 may represent steps in a method and/or sections of code in the computer program 405. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A control system comprising at least one controller for controlling operation of a powertrain of a vehicle, in which the powertrain comprises an internal combustion engine, an electric motor and a transmission, wherein the control system is configured to: determine a currently selected gear of the transmission; determine a rotational speed of the transmission; determine if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed being within a predetermined range associated with the currently selected gear, determine a first torque value for the internal combustion engine and a second torque value for the electric motor; cause the internal combustion engine to provide a first torque output dependent on the first torque value; and cause the electric motor to provide a second torque output dependent on the second torque value.
2. A control system according to claim 1, wherein said control system comprises at least one electronic processor having an electrical input for receiving a signal indicative of a rotational speed of transmission; and at least one electronic memory device electrically coupled to the at least one electronic processor and having instructions stored therein, the at least one processor being configured to access the at least one memory device and execute the instructions stored therein such that it is operable to: determine the currently selected gear of the transmission; determine the rotational speed of the transmission; determine if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed with the currently selected gear being within a predetermined range associated with the currently selected gear, determine a first torque value for the internal combustion engine and a second torque value for the electric motor; cause the internal combustion engine to provide the first torque output dependent on the first torque value; and cause the electric motor to provide the second torque output dependent on the second torque value.
3. A control system according to claim 1 or claim 2, wherein the control system is configured to determine if the rotational speed is within the predetermined range associated with the currently selected gear by determining from stored data, if the rotational speed with the currently selected gear corresponds to a frequency band in which a part of the powertrain is caused to resonate.
4. A control system according to any one of claims 1 to 3, wherein the control system is configured to determine the first torque value and/or the second torque value in dependence on a predetermined relationship.
5. A control system according to any one of claims 1 to 4, wherein the control system is configured to determine the first torque value and/or the second torque value by retrieving stored data corresponding to the rotational speed of the transmission and the currently selected gear.
6. A control system according to any one of claims 1 to 5, wherein the control system is configured to: determine a torque demand; and determine the first torque value and/or the second torque value in dependence on the torque demand.
7. A control system according to any one of claims 1 to 6, wherein the first torque value and the second torque value are indicative of a torque ratio; and the first torque output and the second torque output are caused to be in said torque ratio.
8. A control system according to any one of claims 1 to 7, wherein the control system is configured to: determine a slip value in dependence on the rotational speed and a torque input to the transmission; and cause a clutch of the powertrain to slip by an amount that depends on the slip value.
9. A control system according to claim 8, wherein the control system is configured to select the clutch to be slipped from a plurality of clutches of the powertrain in dependence on the rotational speed and the currently selected gear.
10. A powertrain comprising the control system of any one of claims 1 to 9, an internal combustion engine, an electric motor and a transmission.
11. A powertrain according to claim 10, wherein the transmission comprises an automatic 5 transmission.
12. A powertrain according to claim 10 or claim 11, wherein the powertrain comprises at least one clutch; the control system is configured to cause the at least one clutch to slip in dependence on the rotational speed and the currently selected gear; and the at least one clutch is configured to provide an operational connection between a first part of the powertrain and a second part of the powertrain, the first part and the second part being items selected from the group: the internal combustion engine; the electric motor; a gear train of the transmission; and a shaft connecting the transmission to one or more road wheels.
13. A powertrain according to any one of claims 1 to 12, wherein a harmonic component of torque generated by the internal combustion engine corresponds to a resonance frequency of a part of the powertrain, and the first torque value and the second torque value are arranged to minimize the torque output of the internal combustion engine while meeting a torque demand.
14. A vehicle comprising the powertrain of any one of claims 10 to 13.
15. A method of controlling a powertrain of a vehicle, the powertrain comprising an internal combustion engine, an electric motor and a transmission, and the method comprising: determining a currently selected gear of the transmission; determining a rotational speed of the transmission; determining if the rotational speed is within a predetermined range associated with the currently selected gear; in dependence on the rotational speed being within a predetermined range associated with the currently selected gear, determining a first torque value for the internal combustion engine and a second torque value for the electric motor; causing the internal combustion engine to provide a first torque output dependent on the first torque value; and causing the electric motor to provide a second torque output dependent on the second torque value.
16. A method according to claim 15, wherein said determining if the rotational speed is within the predetermined range associated with the currently selected gear comprises determining from stored data, if the rotational speed with the currently selected gear corresponds to a frequency band in which a part of the powertrain is caused to resonate.
17. A method according to claim 15 or claim 16, wherein the method comprises determining the first torque value and/or the second torque value in dependence on a predetermined relationship.
18. A method according to any one of claims 15 to 17, wherein the method comprises determining the first torque value and/or the second torque value by retrieving stored data corresponding to the rotational speed of the transmission.
19. A method according to any one of claims 15 to 18, wherein the method comprises: determining a torque demand; and determining the first torque output and/or the second torque output in dependence on the torque demand.
20. A method according to claim 19, wherein the method comprises: determining a slip value in dependence on the rotational speed, the currently selected gear and the torque demand; and causing a clutch of the powertrain to slip by an amount that depends on the slip value.
21. A method according to claim 20, wherein the method comprises: determining if the rotational speed with the currently selected gear and the first torque output and/or the second torque output is likely to cause a vibration amplitude to be above a threshold level; and determining the slip value in dependence on the rotational speed with the currently selected gear and the first torque output and/or the second torque output being likely to cause a vibration amplitude above a threshold level.
22. A method according to claim 20 or claim 21, wherein the method comprises selecting at least one clutch to be slipped from a plurality of clutches of the powertrain in dependence on the rotational speed, and causing the at least one clutch to be slipped.
23. A method according to any one of claims 15 to 21, wherein a harmonic component of torque generated by the internal combustion engine corresponds to a resonance frequency of a part of the powertrain, and the first torque value and the second torque value are arranged to minimize the torque output of the internal combustion engine.
24. A non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of a method according to any one of claims 15 to 23.
25. A control system comprising at least one controller for controlling operation of a powertrain of a vehicle, in which the powertrain comprises an internal combustion engine, an electric motor and a transmission, wherein the control system is configured to: determine a total torque demand; determine a currently selected gear of the transmission and a rotational speed of the transmission corresponding to a frequency of the internal combustion engine; retrieve stored data corresponding to the currently selected gear and the rotational speed; cause the internal combustion engine to provide a first torque output in dependence on the retrieved stored data; cause the electric motor to provide a second torque output in dependence on the retrieved stored data; wherein the combination of the first torque output and the second torque output meets the total torque demand; and the stored data is configured to cause the ratio of the first torque output to the second torque output to be dependent on whether or not the frequency is a frequency at which a part of the powertrain is caused to resonate.