Control of an electrical drive unit for a vehicle

Abstract

Aspects of the present invention relate to a control system for controlling an electrical drive unit for a vehicle. The electrical drive unit comprises an electric motor. The vehicle comprises: an anti-lock braking system for modulating a braking torque applied to a wheel of the vehicle. The vehicle further comprises a driveshaft, which operatively couples the electrical drive unit to the wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel. The control system comprises: one or more processors collectively configured to: receive a wheel speed signal that indicative of a rotational speed of the wheel of the vehicle. The one or more processors are further configured to determine an angular acceleration of the wheel of the vehicle based on the wheel speed signal and determine a target torque for the electric motor based on the angular acceleration of the wheel. The one or more processors output a torque control signal for controlling the electric motor based on the target torque. A system for a vehicle comprising the control system and a vehicle comprising the system are also provided. Also provided is a method for controlling an electrical drive unit for a vehicle.

Description

[0001] CONTROL OF AN ELECTRICAL DRIVE UNIT FOR A VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to control of an electrical drive unit for a vehicle. Aspects of the invention relate to a control system for controlling an electrical drive unit for a vehicle, to a system for a vehicle, to a vehicle, and to a method for controlling an electrical drive unit for a vehicle.

[0004] BACKGROUND

[0005] It is known to provide an anti-lock braking system for a vehicle which controls the torque provided by brakes of the vehicle to the vehicle wheels based on the rotational speed of the wheels. In particular the torque is controlled in order to slow the vehicle without the wheels of the vehicle becoming locked.

[0006] It is also known for a vehicle to be powered by an electrical drive unit comprising an electric motor and gear assembly configured to generate and supply torque to the wheels of the vehicle via one or more, e.g. respective, driveshafts. In particular, a torque supplied by the electrical drive unit to the wheels may be determined based on an accelerator driving input provided on the vehicle.

[0007] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0008] SUMMARY OF THE INVENTION

[0009] Aspects and embodiments of the invention provide a control system, a system, a vehicle, and a method for controlling an electrical drive unit for a vehicle as claimed in the appended claims.

[0010] According to an aspect of the present invention there is provided a control system for controlling an electrical drive unit for a vehicle, wherein the electrical drive unit comprises an electric motor, and wherein the vehicle comprises: a driveshaft, for operatively coupling the electrical drive unit to a wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel, wherein the control system comprises: one or more processors collectively configured to: receive a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determine an angular acceleration of the wheel of the vehicle; determine a target torque for the electric motor based on the angular acceleration of the wheel; and output a torque control signal for controlling the electric motor based on the target torque.

[0011] The vehicle may further comprise an anti-lock braking system for modulating a braking torque applied to the wheel of the vehicle.

[0012] According to another aspect of the present invention there is provided a control system for controlling an electrical drive unit for a vehicle, wherein the electrical drive unit comprises an electric motor, and wherein the vehicle comprises: an anti-lock braking system for modulating a braking torque applied to a wheel of the vehicle, a driveshaft, for operatively coupling the electrical drive unit to the wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel, wherein the control system comprises: one or more processors collectively configured to: receive a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determine an angular acceleration of the wheelof the vehicle; determine a target torque for the electric motor based on the angular acceleration of the wheel; and output a torque control signal for controlling the electric motor based on the target torque.

[0013] The angular acceleration of the wheel of the vehicle may be determined based on differentiating the wheel speed signal with respect to time.

[0014] During heavy breaking of a vehicle, particularly when the vehicle is operating on rough or uneven ground, the operation of an Anti-lock Braking System of the vehicle can result in a speed of rotation of a wheel of the vehicle varying out of phase with a speed of rotation of a rotor of an electric motor forming part of an electrical drive unit of the vehicle. These out of phase variations in speed can lead to undesirable vibrations. By controllably varying a torque output of the electric motor based on an acceleration of the wheel, so that a rotation of the electric motor rotor follows the wheel, a magnitude of driveshaft torques in such operating regimes can be reduced.

[0015] The vehicle may comprise a brake pedal and a brake pedal sensor. The one or more processors may be further configured to receive a brake pedal signal indicating whether a brake pedal of the vehicle is depressed. The torque control signal may be output based on the brake pedal being depressed. In this way, the electric motor may be controlled to follow the angular accelerations of the wheel to counteract torque oscillations in the driveshaft only when the vehicle is braking. This may be the time when undesirable vibrations are experienced. At other times, the electric motor may continue to be controlled to generate torque to drive the wheels, as determined based on accelerator input.

[0016] The wheel may be a first, e.g. left, wheel of the vehicle and the driveshaft may be a first, e.g. left, driveshaft. The vehicle may further comprise a second, e.g. right, wheel, and a second, e.g. right, driveshaft for operatively coupling the electrical drive unit to the second, e.g. right, wheel of the vehicle. The one or more processors may be further configured to: receive a second, e.g. right, wheel speed signal indicative of a rotational speed of the second, e.g. right, wheel of the vehicle and determine an average of the angular accelerations of the first, e.g. left, wheel of the vehicle and the second, e.g. right, wheel of the vehicle. The target torque for the electric motor may determined based on the average angular acceleration of the first, e.g. left, wheel and the second, e.g. right, wheel.

[0017] The one or more processors may be configured to: based on, e.g. by differentiating, the second, e.g. right, wheel speed signal, determine a second, e.g. right, wheel acceleration of the wheel of the vehicle. The average of the accelerations may be determined by summing the result of differentiating the first and second, e.g. left and right, wheel speed signals.

[0018] By averaging the wheel speeds of the left and right wheels of the vehicle, the control system may account for arrangements in which a single electric motor provides torque to both left and right wheels of the vehicle. In this way, the control system may control the torque supplied by the electric motor to reduce torque vibrations in both the left and right driveshafts. The electric motor may provide torque to the left and right driveshafts viaa differential. Alternatively, the left and right driveshafts may be connected, e.g. fixedly connected, so as to rotate together.

[0019] The electrical drive unit may comprise a gear assembly arranged to transmit torque between the electric motor and the driveshaft. The one or more processors may be configured to determine the target torque for the electric motor further based on a gear ratio of the gear assembly.

[0020] Including a gear assembly as part of the electrical drive unit may increase a maximum torque which can be provided to the driveshaft from the electrical drive unit. Accounting for the presence of the gear assembly may enable torsional vibrations of the driveshaft to be more accurately accounted for.

[0021] The one or more processors may be configured to determine the target torque for the electrical motor further based on an inertia of the driveshaft.

[0022] Including considerations of the inertia of the driveshaft in the target torque to be provided by the electric motor may improve the accuracy with which the electric motor is controlled to account for torsional vibrations in the driveshaft.

[0023] The one or more processors may be further configured to apply a predetermined proportional gain to the target torque.

[0024] Applying a gain to the target torque may improve the stability of the torsional vibrations in the driveshaft when the electric motor is providing torque to counteract these torsional vibrations.

[0025] The electric motor of the electrical drive unit may be configured to act as a generator to generate electricity during regenerative braking of the vehicle. Outputting the torque control signal may comprise combining, e.g. summing, a torque requirement of the electric motor to perform the regenerative braking with the target torque.

[0026] In this way, the electric motor may continue operating to supply electrical power to the vehicle whilst operating to counteract torsional vibrations in the driveshaft during braking.

[0027] The wheel speed sensor may be directly communicatively coupled to the one or more processors, e.g. without an intervening vehicle communications network, optionally having a communication protocol by which the wheel speed signal is transmitted.

[0028] Directly communicatively coupling the wheel speed sensor to the one or more processors may reduce a latency of wheel speed signals received by the one or more processors, which may in turn enable a delay with which the control system controls the torque provided by the electric motor, in response to changes in the rotational speed of the wheel, to be reduced.

[0029] The anti-lock braking system may comprise an anti-lock braking system controller configured to output a brake signal to modulate a braking torque applied to the wheel of the vehicle based on the rotational speed of thewheel. The wheel speed sensor may be directly communicatively coupled to the anti-lock braking system controller.

[0030] When the wheel speed sensor is directly connected to both the one or more processors of the control system for controlling the electrical drive unit for a vehicle and the anti-lock braking system controller, both control systems may operate, to control the electric motor and brakes respectively, based on input signals with reduced delay, e.g. compared to if the wheel speed signal was received from another controller of the vehicle via a vehicle network, such as a controller area network.

[0031] The anti-lock braking system controller may be communicatively coupled to the control system, e.g. the one or more processors, via a vehicle communications network. The one or more processors may be configured to receive the wheel speed signal from the anti-lock braking system controller via the vehicle communications network.

[0032] In some arrangements, the wheel speed sensor may be directly communicatively coupled to a further control system of the vehicle, e.g. the anti-lock braking control system. The further control system may be communicatively coupled to the control system via a vehicle communications network. The one or more processors may be configured to receive the wheel speed signal from the further control system via the vehicle communications network.

[0033] Configuring the one or more processors to receive the wheel speed signal from the anti-lock braking system (further control system) via the vehicle communications network may simplify the direct connections between the wheel speed sensor and control systems of the vehicle.

[0034] The control system may comprise a filter, such as a low pass filter, configured to introduce a delay to the wheel speed signal received via the vehicle communications network, such that the one or more processors receive the wheel speed signal with a total delay approximately equal to a period of a torsional vibrational mode of the driveshaft, such as a lowest frequency torsional vibration mode of the driveshaft or drivetrain of the vehicle.

[0035] In this way, torque generated by the electric motor in order to counteract torsional vibrations in the driveshaft may be applied by the electric motor in phase with the torsional vibrations.

[0036] The filter may be configured to pass signals with a frequency less than or equal to a natural frequency of the torsional vibration mode of the driveshaft or driveline of the vehicle, e.g. the lowest frequency torsional vibration mode, such as a shuffle frequency.

[0037] In this way, fluctuations in torsional vibrations of the driveshaft, which are occurring at frequencies greater than the natural frequency of the driveshaft, and hence, which may not be present at the point at which the corrective torque is provided by the electric motor, may be filtered from the wheel speed signal and may not influence the torque provided by the electric motor to the driveshaft.A system for a vehicle may comprise the above-mentioned control system and an anti-lock braking control system for the anti-lock braking system. The anti-lock braking control system may comprise one or more further processors, wherein the one or more further processors are directly communicatively coupled to the wheel speed sensor. The one or more further processors may be collectively configured to: receive the wheel speed signal indicative of the rotational speed of the wheel of the vehicle; and output the wheel speed signal to the control system via a vehicle communications network.

[0038] A vehicle may comprise the above-mentioned control system or the above-mentioned system.

[0039] According to an aspect of the present invention there is provided a method for controlling an electrical drive unit for a vehicle, wherein the electrical drive unit comprises an electric motor, and wherein the vehicle comprises: an anti-lock braking system for modulating a braking torque applied to a wheel of the vehicle, a driveshaft, for operatively coupling the electrical drive unit to the wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel. The method comprises: receiving a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determining an angular acceleration of the wheel of the vehicle; determining a target torque for the electric motor based on the angular acceleration of the wheel; and outputting a torque control signal for controlling the electric motor based on the target torque.

[0040] According to an aspect of the present invention there is provided computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the above-mentions method.

[0041] The control system comprises one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: receive a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determine an angular acceleration of the wheel of the vehicle; determine a target torque for the electric motor based on the angular acceleration of the wheel; and output a torque control signal for controlling the electric motor based on the target torque.

[0042] 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

[0043] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0044] Figure 1 shows a front perspective view of a vehicle according to an embodiment of the invention;

[0045] Figure 2 shows a schematic plan view of a system of the vehicle;

[0046] Figure 3a is a graph illustrating a relationship between wheel speed and electric motor rotor speed, and time; Figure 3b is a graph illustrating a relationship between driveshaft torque and time;

[0047] Figure 4 is schematic view of a control system according to an embodiment of the invention; and

[0048] Figure 5 is a flow chart illustrating a method according to an embodiment of the invention.

[0049] DETAILED DESCRIPTION

[0050] A vehicle 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 1. As shown in Figure 1 , vehicle 1 comprises a control system 400 according to embodiments of the present invention. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles.

[0051] Referring now to Figure 2, the vehicle 1 comprises a system 100, which may comprise an electrical drive unit 110, one or more driveshafts 120, 122, and one or more wheels, e.g. road wheels 130, 132. The system 100 may further comprise the control system 400 for controlling the operation of the electrical drive unit 110.

[0052] The one or more driveshafts 120, 122 are for transmitting drive torque from the electrical drive unit 110 to the one or more road wheels, e.g. respectively. In the arrangement depicted, the system 100 comprises a left hand drive shaft 120 and a right hand drive shaft 122 operatively coupled between the electrical drive unit 110 and left and right road wheels 130, 132 of the vehicle respectively. As illustrated, first ends 120a, 122a of the driveshafts may be operatively coupled to the electrical drive unit 110 and second ends 120b, 122b of the driveshafts may be coupled to the respective road wheels.

[0053] The electrical drive unit 110 comprises an electric motor 112 and a gear assembly 114 operatively coupled to the electric motor. The electric motor comprises a rotor 112a, and a stator 112b disposed at least partially about the rotor 112a. In use of the electrical drive unit 110, electric currents may be supplied to electric coils provided on the rotor and / or stator in order to drive the rotor 112a to rotate with respect to the stator and generate torque, which is supplied to the gear assembly 114.

[0054] The gear assembly 114 comprises one or more drive gears meshingly coupled together and configured to provide a gear ratio, e.g. a torque or speed ratio, between the electric motor and the driveshafts 120, 122. In particular, the gear assembly may be configured to provide a gear ratio to enable an increased torque to be supplied to the driveshafts than can be developed by the electric motor 112 at a particular drive speed. For example, the gear assembly may be configured to provide a gear ratio of about 11 or greater than 11 , such as 11.1. In some arrangements, the system 100 may comprise a differential 140 operatively connected betweenthe gear assembly 114 and the driveshafts 120, 122. The differential 140 may be configured such that the torque provided from the electrical drive unit 110 is divided between the driveshafts 120, 122.

[0055] The electrical drive unit 110, e.g. the electric motor 112, may comprise a rotor speed sensor 112c configured to measure, e.g. directly measure, a rotational speed of the rotor 112a of the electric motor. The rotor speed sensor 112c may output a rotor speed signal indicative of the rotational speed of the rotor. In other arrangements, the rotor speed sensor 112c may be configured to measure a rotational speed of a shaft of the gear assembly 114, or another shaft of the electrical drive unit, and may determine the speed of rotation of the rotor 112a based on the measured rotational speed.

[0056] The vehicle 1 , e.g. the system 100, may further comprise one or more driving controls, such as an accelerator control 162, e.g. an accelerator pedal, and a brake control 164, such as a brake pedal.

[0057] The torque generated by the electric motor 112 may be controlled based on an accelerator input signal, which may by output by an accelerator input sensor 163 operatively coupled to the accelerator control 162. The accelerator input signal may be indicative of an accelerator input provided by an operator of the vehicle using the accelerator control. For example, the accelerator input sensor may be an accelerator pedal position sensor configured to determine an extent to which the accelerator pedal is depressed. The control system 400, or another control system of the vehicle, may receive the accelerator input signal and may determine a torque demand signal indicative of an amount of torque to be supplied by the electric motor 112, which may then be output to the electric motor 112. The electric motor 112 may operate to generate drive torque based on the torque demand signal. In other arrangements, the electric motor 112 may be configured to receive the accelerator input signal and may be controlled to supply drive torque based on the accelerator input signal directly.

[0058] The vehicle, e.g. the system 100, may further comprise one or more brakes 150, 152 configured to brake the road wheels 130, 132 of the vehicle, e.g. in order to decelerate the vehicle. In particular, the vehicle may comprise a left brake 150 configured to brake the left road wheel 130 of the vehicle and a right brake configured to brake the right road wheel 132 of the vehicle. In some arrangements, the brakes 150, 152 may comprise disc brakes each comprising a brake disc 150a, 152a fixedly coupled to the corresponding wheel for rotation together with the wheel, and a brake calliper 150b, 152b configured to selectively engage the corresponding brake disc and apply a braking torque to the wheel via the brake disc. In other arrangements, the brakes may be any other type of brakes.

[0059] The system 100 may further comprise a brake control system 200 configured to control the operation of the brakes 150, 152 to decelerate the vehicle. For example, the brake control system 200 may be configured to receive a brake input signal output by a brake position sensor 165 operatively coupled to the brake control 164. The brake input signal is indicative of a braking input provided by the operator using the brake control 164. For example, the brake input sensor may be a brake pedal position sensor configured to determine an extent to which the brake pedal is depressed or a brake pressure sensor configured to determine a pressure of brake fluid. The brake control system 200 may output one or more, e.g. respective, brake demand signalsto the brakes 150, 152 and the operation of the brakes, e.g. the braking torque provided by the brakes, or the braking pressure applied by the brake callipers 150a, 150b to the brake discs 152a, 152b, may be controlled at least partially based on the brake demand signal.

[0060] The vehicle, e.g. the system 100, may further comprise one or more wheel speed sensors 166, 168 configured to measure a rotational speed of the road wheels of the vehicle. In particular, the system may comprise a left wheel speed sensor 166 configured to measure a rotational speed of the left road wheel 130 and a right wheel speed sensor 168 configured to measure a rotational speed of the right wheel 132. The wheel speed sensors may be configured to output wheel speed signals, e.g. respective wheel speed signals, indicative of the rotational speeds of the corresponding wheels.

[0061] The brake control system 200 may be configured to receive the wheel speed signals, and may output the one or more brake demand signal at least partially based on the wheel speed signals. In some arrangements, the brake control system is an anti-lock braking control system configured to control the braking torque provided by the brakes 150, 152 based, at least partially, on the rotational speed of the corresponding wheel, in order to reduce risks of the wheels becoming locked by the brakes.

[0062] While the vehicle 1 shown in Figures 1 and 2 is an electric vehicle (EV), e.g. a plug-in electric vehicle, without an internal combustion engine. The vehicle 1 may be alternatively a hybrid electric vehicle (HEV), such as a plug-in HEV or a mild HEV. The vehicle may have an electric-only mode of propulsion or the electric motor 112 may be configured to provide assistance such as supplementing an output torque of an internal combustion engine. Further, while in the arrangements illustrated the vehicle is a front wheel drive vehicle, in other arrangements, the invention may be implemented on a rear wheel drive vehicle, or on a 4-wheel or allwheel drive vehicle.

[0063] With reference to Figure 3a, when the vehicle is decelerating, particularly on rough or uneven ground, the operation of the anti-lock brake system 200 to control the braking torque applied to a particular wheel to reduce the risk of the particular wheel becoming locked due to the applied braking torque may lead to the rotational speed of the wheel varying as illustrated by line 302 as the brake torque is modulated. When the vehicle is decelerating, substantially no torque may be being generated by the electric motor 112. Torque transmitted by the driveshafts 120, 122 between the road wheels 130, 132 of the vehicle and the electrical drive unit 110 may therefore depend on the variations in the rotational speed of the wheels.

[0064] When an effective inertia of the rotor 112a of the electric motor 112 is high, for example, due to the gear ratio of the gear assembly 114 being high, a rotational speed of the rotor 112a, and hence, a rotational speed of the first ends 120a, 122a of the driveshafts may vary as illustrated by line 304, e.g. as the rotor 112a of the electric motor is driven to rotate, in order to follow changes in speed of rotation of the road wheels 130, 132.

[0065] Accordingly, as illustrated in Figure 3a, a variation in rotational speed of the first ends 120a, 122a of the drive shaft may be out of phase with a variation in rotational speed of the road wheels coupled to the second ends of the driveshafts at one or more instances whilst the vehicle is decelerating. This out of phase variation inrotational speeds may in turn lead to oscillations in torque being transmitted through the driveshaft as illustrated in Figure 3b, in which line 306 shows torque oscillations of the drive shaft 120. Such oscillations in torque may lead to undesirable vibrations of the electrical drive unit, and result in undesirable loads and torques.

[0066] With reference to Figure 4, in order to reduce oscillations in the torque transmitted by the driveshaft 120, 122 during braking, the vehicle 1 may comprise the control system 400, according to the present invention.

[0067] The control system 400, as illustrated in Figure 4, comprises one controller 410, although it will be appreciated that this is merely illustrative. The controller 410 comprises one or more processors 420 and may comprise one or more memories 430. The one or more processors may be configured operably execute computer-readable instructions. The one or more memories 430 may be electrically coupled to the processors 420. The one or more memories 430 may be configured to store instructions, and the one or more processors 420 may be configured to access the one or more memories and execute the instructions stored thereon.

[0068] The controller 410 comprises an input means and an output means. To this end, the controller 410 may have an interface 412 comprising an electrical input 414 of the controller 410 and an electrical output means 416. The electrical input 414 may be for receiving one or more input signals relevant to the methods described herein. In particular, the controller 410 may be configured to receive one or more signals from one or more sensors of the vehicle, such as the brake input sensor 165, the accelerator input sensor 163, the wheel speed sensors 166, 168 and / or the rotor speed sensor 112c. The controller 410 may be further configured to receive one or more signals from one or more further controllers or processors 450 of the control system. Additionally or alternatively, the electrical input 414 of the controller 410 may be coupled to a signal bus 452, such as a Controller Area Network (CAN) bus, and may be configured to retrieve one or more inputs, e.g. from the sensors and / or further controllers / processors, via the signal bus. The signal bus, e.g. CAN bus, may be an example of a vehicle communications network. References in this specification to receiving a signal may correspond to retrieving the signal from the signal bus 452.

[0069] The electrical output 416 is for outputting control signals (directly or indirectly) to external actuators such as the electrical motor 112. In particular, the controller 410 may be configured to output the torque demand signal to the electrical motor 112, as described above. In some arrangements, the controller may output the torque demand signal (or any other signal) via the signal bus 452.

[0070] Figure 5 illustrates a method 500 according to an embodiment of the invention. The method 500 is a method of controlling a system, such as the system 100, or an electrical drive unit, such as the electrical drive unit 110, of a vehicle, such as the vehicle 1 illustrated in Figure 1. The method 500 may be performed by the control system 400 illustrated in Figure 4. In particular, the memory 430 may comprise computer-readable instructions which, when executed by the processor 420, perform the method 500 according to an embodiment of the invention.

[0071] According to the method 500, the system or electrical drive unit may be controlled to reduce a magnitude of oscillations in torque transmitted by the driveshafts during deceleration of the vehicle.The method 500 comprises a first block 502, in which the controller, e.g. the one or more processors, receive a wheel speed signal indicative of a rotational speed of a wheel, e.g. the left road wheel or right road wheel, of the vehicle. For example, the wheel speed signal may be received by the controller 410 from the left wheel speed sensor 166 or the right wheel speed sensor 168 via the electrical input 416.

[0072] The method 500 comprises a second block 504, in which the controller, e.g. the one or more processors, determine an angular acceleration of the wheel of the vehicle, e.g. the left road wheel or the right road wheel, based on the wheel speed signal. In particular, the angular acceleration of the one of the left or right road wheel to which the wheel speed signal relates may be determined.

[0073] The angular acceleration of the wheel of the vehicle may be determined, e.g. in the second block 504, by differentiating the rotational speed of the wheel, e.g. the wheel speed signal, with respect to time.

[0074] The method 500 further comprises a third block 506, in which the controller, e.g. the one or more processors, determine a target torque for an electric motor 112 of the electrical drive unit based on the angular acceleration of the wheel. In particular, the target torque may be determined in order to counteract the torque transmitted through the driveshaft to thereby reduce oscillations in the torque transmitted by the driveshaft. In this way, the electric motor 112 may be driven to rotate in order to follow accelerations and / or decelerations of the road wheels of the vehicle during braking.

[0075] In some arrangements, the controller, e.g. the one or more processors may be configured to determine the target torque for the electrical motor at least partially based on an inertia, e.g. a combined referred inertia, of the driveshaft, the gear assembly 114 and / or the rotor 112a of the electric motor . For example, the target torque may be determined based on multiplying the angular acceleration by the inertia, e.g. the combined referred moment of inertia or a pre-determined portion, e.g. fraction or multiple, of the inertia.

[0076] Additionally or alternatively, the controller, e.g. the one or more processors may be configured to determine the target torque for the electric motor 112 further based on a gear ratio of the gear assembly of the electrical drive unit. For example, the target torque may be determined based on multiplying the angular acceleration of the wheel by the gear ratio of the gear assembly. The angular acceleration may be multiplied by the gear ratio of the gear assembly in addition or as an alternative to multiplying the angular acceleration by the inertia of the driveshaft, or a pre-determined portion thereof.

[0077] Additionally or alternatively again, the controller, e.g. one or more processors, may be configured to apply a predetermined proportional gain to the target torque. For example, the controller may be configured to multiple the target torque value by a gain value of between 0.1 and 1 or between 0.1 and 0.5.

[0078] The method comprises a fourth block 508 in which a torque control signal is output by the controller, e.g. the one or more processors, for controlling the electric motor 112 based on the target torque. The torque control signal may be output to the electrical drive unit 110 or electric motor 112.As described above, during normal operation of the vehicle 1 , the electric motor 112 may be controlled based on the torque demand signal to supply torque to drive the road wheel to rotate, e.g. in order to accelerate the vehicle. Further, the oscillations in torque being transmitted through the driveshaft, as shown in Figure 3b, may be generated whilst the vehicle is braking. Hence, it may be desirable that the electric motor is driven based on the torque control signal, e.g. according to the method 500, when, e.g. only when, the vehicle is braking.

[0079] The controller 410, e.g. the one or more processors, may be configured to receive a brake input signal, such as a brake pedal signal, which may be the output by the brake position sensor 165. The brake input signal may indicate whether a brake control is being operated by an operator of the vehicle, e.g. whether the brake pedal of the vehicle is depressed. The torque control signal may be output, e.g. in the fourth block, based on the brake control being operated, e.g. the brake pedal being depressed.

[0080] As described above, the vehicle 1 may have a left wheel, e.g. left road wheel 130, operatively coupled to the electric drive unit by a left drive shaft 120. References to the wheel and driveshaft when describing the method 500 above may refer to the left wheel and left drive shaft. The vehicle may further comprise a right wheel, and a right driveshaft for operatively coupling the electrical drive unit to the right wheel of the vehicle.

[0081] The controller, e.g. the one or more processors, may be further configured to receive a right wheel speed signal indicative of a rotational speed of the right wheel of the vehicle. The right wheel speed signal may be received in the first block 502 together with the wheel speed signal, e.g. the left wheel speed signal.

[0082] The method 500 may further comprise, e.g. as part of the second block 504, determining an average of the angular accelerations of the left wheel of the vehicle and the right wheel of the vehicle. As described above, the vehicle may comprise the differential 140 configured to distribute torque from the electrical drive unit 110 between the left and right drive shafts. Accoridngly, the effect of variations in accelerations of the driveshafts on the electrical drive unit, e.g. on rotations of the rotor of the electric motor 112, may correspond to the average of the variations in angular acceleration of the driveshafts.

[0083] The average acceleration of the left and right wheel may be determined by differentiating, the right wheel speed signal to determine a right wheel acceleration of the wheel of the vehicle, and determining an average of the left wheel acceleration and the right wheel acceleration. Alternatively, the average acceleration of the left and right wheel may be determined by determining an average of the wheel speed signal and right wheel speed signal, and differentiating the average of the signals.

[0084] In other arrangements in which the vehicle does not comprise the differential 140, the average of the accelerations on the driveshafts may similarly provide a useful indication of the effect of the combined variations in wheel speed on the electrical drive unit.

[0085] The target torque for the electric motor may then be determined, e.g. in the third block 506, based on the average angular acceleration of the left wheel and the right wheel. For example, the target torque may bedetermined by multiplying the average angular acceleration by the inertias of the driveshaft, the gear assembly 114 and / or the rotor 122a of the electric motor, the gear ratio of the gear assembly, and / or the predetermined gain value, as described above.

[0086] In some arrangements, the electric motor 112 of the electrical drive unit may be configured to act as a generator to generate electricity during regenerative braking of the vehicle. In particular, whilst the vehicle is braking, the electric motor may be operated as a generator. When the electric motor is operating as a generator, the electric motor may apply a decelerating torque, which acts to reduce a rotational speed of the road wheels via the respective driveshafts. The decelerating torque may be a constant toque applied by the electric motor during regenerative braking. Outputting the torque control signal, e.g. in the further block, may comprise combining a torque requirement of the electric motor to perform the regenerative braking with the target torque, so that the electric motor can continue regenerative braking whilst also acting to reduce torque oscillations in the driveshafts.

[0087] Returning now to Figure 2, in vehicle 1 , the wheel speed sensors 166, 168, e.g. the left and right wheel speed sensors, may not be directly communicatively coupled to the control system 400, e.g. to the one or more processors of the controller 410. Instead the wheel speed sensors may be directly communicatively connected to a different, further control system of the vehicle. In the arrangement shown in Figure 2, the wheel speed sensors are directly communicatively connected to the brake control system 200. As illustrated, the further control system, e.g. the brake control system, is communicatively coupled to the control system 400 via a vehicle communications network, e.g. the signal bus 452, such as a CAN bus. The controller 410, e.g. the one or more processors, are configured to receive the wheel speed signal and / or the right wheel speed signal from the further control system, e.g. the brake system, via the vehicle communications network. The controller 410 may receive the wheel speed signal in this way in the first block 502 of the method 500.

[0088] Returning briefly to Figure 3b, a frequency of the oscillations in torque transmitted by the driveshaft may be equal, e.g. approximately equal, to a natural frequency of a torsional vibration mode of the vehicle, e.g. of the wheels 130, 132, driveshafts 120, 122, gear assembly 114 and rotor 112a, the combination of which may be referred to as a driveline of the vehicle.. In particular, the frequency of oscillation in the torque transmitted by the driveshaft may be approximately equal to a natural frequency of a first, e.g. lowest frequency, torsional vibration mode of the vehicle, e.g. the driveline, , which may be referred to as a shuffle frequency. In the arrangement illustrated in Figure 3b, the shuffle frequency is approximately 12Hz.

[0089] Due to the controller 410, e.g. the one or more processors, receiving the wheel speed signal from the further control system, e.g. the brake control system 200, via the vehicle communications network, there may be a delay introduced into the signal received by the controller. The delay may be less than the period of torsional vibrations within the driveshaft, e.g. vibrations corresponding to the first mode of vibration of the vehicle, e.g. driveline. In some arrangements, the delay may be greater than a quarter or greater than a half of the period of the torsional vibrations. Accordingly, corrections to the torsional vibrations made by controlling the electric motor, as described above, may be delayed relative to the torsional vibrations and may be at least partially inphase with the torsional vibrations, which may reduce the efficacy of the system in reducing the torsional vibrations or lead to an increase in the magnitude of the torsional vibrations in some instances.

[0090] The control system 400 may further comprises a filter, such as a low pass filter 412, or other signal delay component configured to introduce a delay to the wheel speed signal received via the vehicle communications network, e.g. the signal bus 452, such that the controller 410, e.g. the one or more processors, receive the wheel speed signal with a total delay approximately equal to a period of the torsional vibrational mode of the driveshaft, e.g. the lowest frequency torsional vibration mode of the driveshaft. In this way, the control system 400 may control the electric motor 112 to counteract the torsional vibrations in the driveshafts based on wheel speed signals with variations in speed which are in phase, e.g. approximately in phase, with current variations in the rotational speed of the wheel. The torque generated by the electric motor 112 in order to counteract torsional vibrations in the driveshaft may thereby be applied by the electric motor in phase with the torsional vibrations in the driveshaft.

[0091] In some arrangement, the low pass filter 412 may be configured to pass signals with a frequency less than or equal to the natural frequency of the torsional vibration mode of the driveshaft, e.g. the lowest frequency torsional vibration mode, such as the shuffle frequency. In this way, oscillations in the rotational speed of the wheels which are occurring with a frequency greater than the natural frequency of the torsions vibrations of the driveshaft may not be used to determine the torque to be supplied by the electric motor to counteract torsional vibrations in the next period of the oscillations.

[0092] In other arrangements, the wheel speed sensor may be directly communicatively coupled to the control system 400, e.g. to the one or more processors of the controller 410, without an intervening communications network, e.g. a signal bus, in between. Accordingly, the wheel speed signal may be not encoded in or translated to a communication protocol used by the network in order to transmit the wheel speed signal over the communications network / signal bus. Hence, the wheel speed signal may be received by the controller 410, e.g. the one or more processors, with substantially no delay. In this case, the filter or other delay component may be omitted.

[0093] As described above with reference to Figure 2, the brake control system 200 (anti-lock braking control system) may be configured to receive the wheel speed signals, and may output the one or more brake demand signal at least partially based on the wheel speed signals in order to control the brake to apply a specified brake torque to the wheels.

[0094] In some arrangements, the brake control system 200 may be configured to determine the brake torque to be applied based on the wheel speed signal, in order to reduce, e.g. damp, oscillations in wheel speed. In particular, the brake control system may be configured to apply proportional, differention and / or integral control to the brake demand signal based on the wheel speed signals, e.g. the respective wheel speed signals, in order to damp oscillations in the wheel speeds of the left and right wheels. This action may be performed together with the steps of the method 500 and may function in combination with the method 500 to reduce drive shaft oscillations.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.

Claims

CLAIMS1. A control system for controlling an electrical drive unit for a vehicle, wherein the electrical drive unit comprises an electric motor, and wherein the vehicle comprises: an anti-lock braking system for modulating a braking torque applied to a wheel of the vehicle, a driveshaft, for operatively coupling the electrical drive unit to the wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel, wherein the control system comprises:one or more processors collectively configured to:receive a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determine an angular acceleration of the wheel of the vehicle; determine a target torque for the electric motor based on the angular acceleration of the wheel; and output a torque control signal for controlling the electric motor based on the target torque.

2. The control system of claim 1 , wherein the vehicle comprises a brake pedal and a brake pedal sensor, wherein the one or more processors are further configured to receive a brake pedal signal indicating whether a brake pedal of the vehicle is depressed, wherein the torque control signal is output based on the brake pedal being depressed.

3. The control system of claim 1 or 2, wherein the wheel is a left wheel of the vehicle and the driveshaft is a left driveshaft, wherein the vehicle further comprises a right wheel, and a right driveshaft for operatively coupling the electrical drive unit to the right wheel of the vehicle, wherein the one or more processors are further configured to:receive a right wheel speed signal indicative of a rotational speed of the right wheel of the vehicle; determine an average of the angular accelerations of the left wheel of the vehicle and the right wheel of the vehicle, wherein the target torque for the electric motor is determined based on the average angular acceleration of the left wheel and the right wheel.

4. The control system of any of the preceding claims, wherein the electrical drive unit comprises a gear assembly arranged to transmit torque between the electric motor and the driveshaft, wherein the one or more processors are configured to determine the target torque for the electric motor further based on a gear ratio of the gear assembly.

5. The control system of any of the preceding claims, wherein the one or more processors are configured to determine the target torque for the electrical motor further based on an inertia of the driveshaft.

6. The control system of any of the preceding claims, wherein the one or more processors are further configured to apply a predetermined proportional gain to the target torque.

7. The control system of any of the preceding claims, wherein the electric motor of the electrical drive unit is configured to act as a generator to generate electricity during regenerative braking of the vehicle, wherein outputting the torque control signal comprises combining a torque requirement of the electric motor to perform the regenerative braking with the target torque.

8. The control system of any of the preceding claims, wherein the wheel speed sensor is directly communicatively coupled to the one or more processors.

9. The control system of any of the preceding claims, wherein the anti-lock braking system comprises an anti-lock braking system controller configured to output a brake signal to modulate a braking torque applied to the wheel of the vehicle based on the rotational speed of the wheel, wherein the wheel speed sensor is directly communicatively coupled to the anti-lock braking system controller.

10. The control system of claim 9, wherein the anti-lock braking system controller is communicatively coupled to the control system via a vehicle communications network, wherein the one or more processors are configured to receive the wheel speed signal from the anti-lock braking system controller via the vehicle communications network.

11. The control system of claim 10, wherein the control system comprises a filter configured to introduce a delay to the wheel speed signal received via the vehicle communications network, such that the one or more processors receive the wheel speed signal with a total delay approximately equal to a period of a torsional vibrational mode of the driveshaft.

12. The control system of claim 11 , wherein the filter is configured to pass signals with a frequency less than or equal to a natural frequency of the torsional vibration mode of the driveshaft.

13. A system for a vehicle comprising the control system of any of claims 1 to 12 and an anti-lock braking control system for the anti-lock braking system, wherein the anti-lock braking control system comprises one or more further processors, wherein the one or more further processors are directly communicatively coupled to the wheel speed sensor, and wherein the one or more further processors are collectively configured to:receive the wheel speed signal indicative of the rotational speed of the wheel of the vehicle; and output the wheel speed signal to the control system via a vehicle communications network.

14. A vehicle comprising the control system of any of claims 1 to 12 or the system of claim 13.

15. A method for controlling an electrical drive unit for a vehicle, wherein the electrical drive unit comprises an electric motor, and wherein the vehicle comprises: an anti-lock braking system for modulating a braking torque applied to a wheel of the vehicle, a driveshaft, for operatively coupling the electrical drive unit to the wheel of the vehicle, and a wheel speed sensor configured to measure a rotational speed of the wheel, wherein the method comprises:receiving a wheel speed signal indicative of a rotational speed of the wheel of the vehicle; based on the wheel speed signal, determining an angular acceleration of the wheel of the vehicle;determining a target torque for the electric motor based on the angular acceleration of the wheel; andoutputting a torque control signal for controlling the electric motor based on the target torque.

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