Torque arbitration for an electric drive unit of a vehicle

Abstract

Aspects of the disclosure relate to an electric drive unit (208), to a control system (300), to a system (209), to a vehicle (1), to a method (500), and to computer readable instructions (308) for a vehicle (1). The electric drive unit (208) comprises an inverter controller (301) for controlling an inverter 5 (206) for a traction electric machine (210) of the electric drive unit (208). The inverter controller (301) comprises one or more processors (304) collectively configured to: receive a torque request (508); receive a plurality of torque restrictor parameters (506, 507, 511A, 513A, 553); determine, in an arbitration function (515) of the inverter controller (301), a first arbitrated torque request (516) in dependence on the plurality of torque restrictor parameters (506, 507, 511A, 513A, 553) and the received torque request (508); and output a torque control signal (557) in dependence on the first arbitrated torque request (516).

Description

[0001] TORQUE ARBITRATION FOR AN ELECTRIC DRIVE UNIT OF A VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to torque arbitration for an electric drive unit of a vehicle. Aspects of the invention relate to an electric drive unit, to a control system, to a system, to a vehicle, to a method, and to computer readable instructions.

[0004] BACKGROUND

[0005] It is known to provide a torque arbitration function in a controller of a vehicle. The torque arbitration function receives a plurality of different torque parameters simultaneously, and outputs an arbitrated torque request towards a torque source of the vehicle, such as an electric drive unit, wherein the arbitrated torque request is dependent on values of the plurality of torque parameters. For example, the arbitrated torque request may be a selected one of the plurality of torque parameters with the highest or lowest magnitude.

[0006] An electric drive unit is a term of the art for a functional module comprising an electric machine, power electronics for controlling the electric machine, and usually a gearbox. The electric drive unit provides propulsive torque for a battery electric vehicle or hybrid electric vehicle.

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

[0008] SUMMARY OF THE INVENTION

[0009] Aspects and embodiments of the invention provide an electric drive unit, a control system, a system, a vehicle, a method, and computer readable instructions as claimed in the appended claims.

[0010] According to an aspect of the present invention there is provided an electric drive unit for a vehicle, comprising an inverter controller for controlling an inverter for a traction electric machine of the electric drive unit, the inverter controller comprising one or more processors collectively configured to:

[0011] receive a torque request;

[0012] receive a plurality of torque restrictor parameters;

[0013] determine, in an arbitration function of the inverter controller, a first arbitrated torque request in dependence on the plurality of torque restrictor parameters and the received torque request; and

[0014] output a torque control signal in dependence on the first arbitrated torque request.

[0015] An advantage is improved control performance because the arbitration function is hosted inside the power electronics (inverter controller) of the electric drive unit, having a very low communication latency connection to the inverter. This obviates the need to receive and send torque requests via a significantly slower vehicle communication network.

[0016] The inverter controller comprises 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:

[0017] receive the torque request;

[0018] receive the plurality of torque restrictor parameters;

[0019] determine, in the arbitration function of the inverter controller, the first arbitrated torque request; and

[0020] output the torque control signal.

[0021] Optionally, the torque request is a pre-arbitrated torque request. Optionally, the inverter controller is configured to receive the torque request from a vehicle communication network. Optionally, in a vehicle with multiple torque sources, the torque request is an electric drive unit torque request for the electric drive unit, split from an overall vehicle torque request by a torque split controller. Optionally, the torque request is dependent on accelerator pedal depression. Optionally, the torque request is dependent on torque demand from an autonomous driving controller.Optionally, the plurality of torque restrictor parameters comprise a plurality of de-rate parameters. Optionally, each de-rate parameter comprises a torque limit.

[0022] An advantage of hosting the arbitration function in the inverter controller is improved control performance because one or more of the plurality of derate parameters may be determined internally within the electric drive unit, for example by the inverter controller. This allows the inverter controller to host fast control loops for the arbitration function.

[0023] Optionally, the arbitration function is configured to:

[0024] arbitrate the de-rate parameters to determine a most restrictive (e.g. , minimum magnitude) one of the plurality of de-rate parameters; and determine the first arbitrated torque request in dependence on the most restrictive one of the plurality of de-rate parameters and the torque request.

[0025] Optionally, the arbitration function is configured to determine the first arbitrated torque request in dependence on only the most restrictive one of the plurality of de-rate parameters and the torque request. Optionally, the inverter controller is configured to determine the most restrictive one of the plurality of de-rate parameters and the torque request, comprising determining a minimum torque magnitude of the torque request and the plurality of de-rate parameters. Optionally, the arbitration function comprises a minimum magnitude torque selector.

[0026] Optionally, the plurality of torque restrictor parameters comprise an axle torque de-rate parameter to limit a total torque produced at an axle of the vehicle. Optionally, the axle torque de-rate parameter comprises a torque limit. Optionally, the axle torque de-rate parameter is configured to limit a total torque produced at the axle of the vehicle by the electric drive unit and a second electric drive unit. The torque produced at an axle refers to the cumulative torque produced at aligned front left and front right wheels of the vehicle, or at aligned rear left and rear right wheels of the vehicle. The wheels may or may not be mechanically coupled, such that the axle may be a real or virtual axle.

[0027] Optionally, the plurality of torque restrictor parameters comprise an individual electric drive unit de-rate parameter to limit torque produced by the electric drive unit separately from another electric drive unit, such as the second electric drive unit described above. Optionally, the individual electric drive unit de-rate parameter comprises a torque limit.

[0028] Optionally, the plurality of torque restrictor parameters comprise a traction control de-rate parameter to limit torque produced by the electric drive unit in dependence on a fraction control function. Optionally, the fraction control de-rate parameter comprises a torque limit. Optionally, the inverter controller hosts at least part of the fraction control function configured to determine the fraction control de-rate parameter in dependence on sensed feedback indicating one or more state parameters of the electric drive unit. Optionally, the fraction control function hosted in the inverter controller is configured to receive a motor speed target. Optionally, the motor speed target is dependent on a detected difference between a sensed wheel speed of a wheel driven by the electric drive unit, and sensed vehicle speed. Optionally, the traction control function is configured to determine the traction control de-rate parameter in dependence on the motor speed target and the current speed of the electric drive unit.

[0029] Optionally, the plurality of torque restrictor parameters comprise a stability intervention de-rate parameter to limit torque produced by the electric drive unit in dependence on a vehicle stability control scheme. Optionally, the stability intervention de-rate parameter comprises a torque limit.

[0030] An advantage of hosting traction control and / or stability control arbitration in the inverter controller is enabling accurate tracking of a fraction control target or a stability control target, due to the low communication latency involved.

[0031] Optionally, the plurality of torque restrictor parameters comprise an energy availability de-rate parameter to limit torque produced by the electric drive unit in dependence on a capability of an electrical energy storage apparatus of the vehicle. Optionally, the capability comprises an electrical power limit. Optionally, the energy availability de-rate parameter comprises a torque limit.

[0032] Optionally, the inverter controller comprises a first monitor to check an output of the arbitration function, and output a de-rate parameter to the arbitration function in dependence on the checked output. Optionally, the de-rate parameter output by the first monitor forms one of the plurality oftorque restrictor parameters. Optionally, the de-rate parameter comprises a torque limit. Optionally, the first monitor comprises a traction control plausibility monitor. An advantage is prioritising accurate traction control parameters over other torque parameters.

[0033] Optionally, the inverter controller comprises an imbalance limiting function configured to:

[0034] receive one or more torque parameters associated with a different electric drive unit coupled to a wheel located on an opposite lateral side of the vehicle than a wheel coupled to the electric drive unit; and

[0035] determine a second arbitrated torque request in dependence on

[0036] the first arbitrated torque request, and

[0037] the one or more torque parameters, and

[0038] wherein the inverter controller is configured to output the torque control signal in dependence on the second arbitrated torque request.

[0039] Optionally, the different electric drive unit is the second electric drive unit. The electric drive unit and second electric drive unit are coupled to different wheels across the axle of the vehicle. Optionally, the imbalance limiting function is configured to limit a differential torque produced at the axle of the vehicle by the electric drive unit and the second electric drive unit.

[0040] An advantage is improved vehicle dynamics because the imbalance limiting function is configured to further arbitrate the arbitrated torque requests for the left and right electric drive units across the axle, to prevent vehicle yaw in situations such as driving on unequal friction surfaces.

[0041] Optionally, the one or more torque parameters comprise a torque request for the different electric drive unit, and at least one torque imbalance limit for limiting differential torque between torque requests for the electric drive units.

[0042] Optionally, the inverter controller comprises an oscillation damping function configured to:

[0043] determine a mechanical resonance associated with the first or second arbitrated torque request;

[0044] determine an anti-phase torque in dependence on the determined mechanical resonance; and

[0045] determine a further torque request in dependence on the anti-phase torque and the respective first or second arbitrated torque request, wherein the inverter controller is configured to output the torque control signal in dependence on the further torque request.

[0046] An advantage is improved vehicle comfort because the anti-phase torque is configured to damp the determined mechanical resonance.

[0047] Optionally, the oscillation damping function is downstream of the imbalance limiting function.

[0048] An advantage is that the oscillation damping is accurate because it is performed once the torque request is close to its final form.

[0049] Optionally, the inverter controller comprises a damping function monitor to receive an output of the oscillation damping function, and output an override parameter to the oscillation damping function in dependence on the output of the oscillation damping function, and wherein the oscillation damping function is configured to determine the anti-phase torque in dependence on the override parameter.

[0050] An advantage is ensuring that the oscillation damping function outputs plausible values.

[0051] Optionally, the inverter controller comprises a torque ripple mitigation function configured to:

[0052] determine an anti-ripple torque in dependence on an output of the oscillation damping function; and

[0053] determine a modified torque request in dependence on the anti-ripple torque and the further torque request, and

[0054] wherein the inverter controller is configured to output the torque control signal in dependence on the modified torque request.

[0055] An advantage is improved noise or vibration because torque ripple is minimised.

[0056] Optionally, the inverter controller comprises a torque magnitude limiter configured to:determine a fixed torque magnitude limit;

[0057] determine a saturated torque request in dependence on the fixed torque magnitude limit and an arbitrated torque request, such as the further torque request output by the oscillation damping function,

[0058] and wherein the inverter controller is configured to output the torque control signal in dependence on the saturated torque request.

[0059] Optionally, the fixed torque magnitude limit is a predetermined hardware protection limit. An advantage is hardware protection of the electric drive unit, which ensures that the earlier functions do not output signals beyond the capabilities of the electric drive unit.

[0060] According to a further aspect of the present invention there is provided a method of controlling an inverter of an electric drive unit of a vehicle, the method comprising:

[0061] receiving a torque request;

[0062] receiving a plurality of torque restrictor parameters;

[0063] determining, in an arbitration function of an inverter controller of the electric drive unit, a first arbitrated torque request in dependence on the plurality of torque restrictor parameters and the received torque request; and

[0064] outputting a torque control signal in dependence on the first arbitrated torque request.

[0065] According to a further aspect of the invention there is provided computer readable instructions which, when executed by a computer, are arranged to perform any one or more of the methods described herein. 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 one or more electronic processors, causes the one or more electronic processors to carry out any one or more of the methods described herein.

[0066] According to a further aspect of the present invention there is provided a control system comprising for controlling an electric drive unit of a vehicle, the control system comprising one or more controllers, the control system comprising one or more processors collectively configured to:

[0067] receive a torque request;

[0068] modify the torque request using any one or more of the following functions:

[0069] an arbitration function;

[0070] an imbalance limiting function;

[0071] an oscillation damping function;

[0072] a torque ripple mitigation function; or

[0073] a torque magnitude limiter; and

[0074] wherein at least one of the used functions is optionally hosted in an inverter controller of the control system,

[0075] and wherein the control system is further configured to output a torque control signal in dependence on the modified torque request.

[0076] 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:

[0077] receive the torque request;

[0078] modify the torque request using the one or more functions; and

[0079] output the torque control signal in dependence on the modified torque request.

[0080] According to another aspect of the present invention there is provided a system comprising the electric drive unit, the electric drive unit comprising the inverter, the traction electric machine, and the inverter controller / control system.

[0081] According to a further aspect of the present invention there is provided a system comprising a pair of the electric drive units, one of which is configured to drive a left wheel of the vehicle and the other is configured to drive a right wheel of the vehicle.According to a further aspect of the present invention there is provided a vehicle comprising the system or the control system or the electric drive unit.

[0082] 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 falls within the scope of the appended claims. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination that falls within the scope of the appended claims, 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.

[0083] BRIEF DESCRIPTION OF THE DRAWINGS

[0084] 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 illustrates a perspective view illustrating an example of a vehicle;

[0085] FIG. 2 illustrates a schematic view illustrating an example of an electric drive system of a vehicle;

[0086] FIG. 3 illustrates a schematic view illustrating an example of a control system;

[0087] FIG. 4 illustrates a schematic view illustrating an example of a computer-readable storage medium;

[0088] FIG. 5 illustrates a flowchart illustrating an example of a method;

[0089] FIG. 6 illustrates a graph illustrating an example of an arbitrated torque request; and

[0090] FIG. 7 illustrates a graph illustrating an example of a torque control signal.

[0091] DETAILED DESCRIPTION

[0092] A vehicle 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying FIG. 1. 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.

[0093] FIG. 2 illustrates a schematic view of the vehicle 1 where the vehicle is a battery electric vehicle (BEV) or hybrid electric vehicle (HEV).

[0094] FIG. 2 illustrates components of an electric drive system 200. The vehicle 1 comprises a fraction battery 202 or an equivalent electrical energy storage means. The traction battery 202 is electrically connected to a DC bus 204.

[0095] The DC bus 204 is an electrical bus for transferring DC power. DC means direct current and AC means alternating current. The DC bus 204 comprises positive and negative conductors, each connected to the fraction battery 202 and to one or more loads. In FIG. 2, the loads comprise a pair of electric drive units (EDUs) 208A, 208B, together defining a system 209. In other examples, only a single EDU 208 is provided.

[0096] A first EDU 208A drives a right wheel of the vehicle 1 and the second EDU 208B drives a left wheel of the vehicle 1 , or vice versa. The vehicle 1 comprises an axle 214 connected to the left and right wheels. In some examples, the axle 214 may be a virtual axle such that the left and right wheels are rotationally decoupled from one other, with no mechanical torque transfer therebetween. The virtual axle simply refers to the wheels being aligned longitudinally such that they are both rear wheels or both front wheels, for example.

[0097] In other examples, one EDU 208A is configured to drive a front wheel or wheels, and the other EDU 208B is configured to drive a rear wheel or wheels.

[0098] The EDUs 208A, 208B share the same DC bus 204 and traction battery 202, but could alternatively be connected to separate DC buses 204 and traction batteries 202.

[0099] Each EDU 208 comprises an inverter 206, an inverter controller 301 configured to control the inverter 206, an electric machine 210 operable as a traction electric machine, and a transmission 212.The inverter 206 is a DC-AC power converter to convert between DC electrical energy on the DC bus 204 and AC energy for the electric machine 210. The inverter 206 is further configured to control the torque of the electric machine 210. The conversion and torque control are controlled by the inverter controller 301.

[0100] The inverter 206, when controlled by the inverter controller 301 , is configured to control the frequency and magnitude of electrical signals supplied to the electric machine 210. The inverter controller 301 regulates the torque of an electric motor primarily by controlling the frequency and magnitude of the electrical signals supplied to the electric machine 210.

[0101] For example, the inverter controller 301 may be configured to adjust the magnitude of the voltage supplied by the inverter 206 to the electric machine 210 to control the EDU's torque output. The inverter controller 301 may be configured to adjust the frequency of the electrical signals supplied to the electric machine 210, to control the electric machine’s speed, thus indirectly controlling torque output.

[0102] The inverter controller 301 may be configured to control a gate control section of the inverter 206 to adjust the magnitude and frequency by pulsewidth modulation (PWM), which comprises adjusting the duty cycle of transistor gates in the gate control section such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors). The inverter controller 301 transmits gate control signals to the transistor gates, to control the torque output of the electric machine 210. The gate control signals are transmitted over a local communication network / bus of the electric machine 210 or of the inverter 206, to the gate control section. The inverter controller 301 has a low-latency connection to the gate control section, and for example may comprise a microcontroller mounted to a same circuit board as the gate control section.

[0103] The electric machine 210 comprises a rotor-stator pair. The electric machine 210 can comprise a Permanent Magnet Synchronous Motor (PMSM), or alternatively an Induction Motor (IM) or Switched Reluctance Motor (SRM) or axial flux motor.

[0104] The transmission 212 is located in a torque path between the electric machine 210 and one or more wheels of the vehicle 1. The transmission 212 provides at least one gear ratio between an output of the electric machine 210 and the one or more wheels of the vehicle 1. In another example, the electric machine 210 comprises a direct drive motor so lacks a transmission 212.

[0105] In some embodiments, the inverter controller 301 , inverter 206, electric machine 210, and transmission 212 may be integrated into a single unit or housing to provide the EDU 208 for the vehicle 1. The EDU 208 comprises a housing arrangement. For example, the housing arrangement comprises one or more enclosures containing various components of the EDU 208. If there are multiple enclosures, the enclosures may be connected to each other, for example by mechanical fixings / sealant, to form a module.

[0106] With reference to FIG. 3, there is illustrated a control system 300 for a vehicle 1. The control system 300 comprises one or more controllers 300.

[0107] The control system 300 is configured to receive one or more torque requests from a module 314 of the vehicle 1 and determine one or more arbitrated torque requests. The control system 300 may then output a control signal to control the inverter 206 in dependence on the one or more arbitrated torque requests.

[0108] The control system 300 as illustrated in FIG. 3 comprises one inverter controller 301 , although it will be appreciated that this is merely illustrative. The controller 301 comprises processing means 304 and memory means 306. The processing means 304 may be one or more electronic processing device 304 which operably execute computer-readable instructions. The memory means 306 may be one or more memory device 306. The memory means 306 is electrically coupled to the processing means 304. The memory means 306 is configured to store instructions, and the processing means 304 is configured to access the memory means 306 and execute the instructions stored thereon.

[0109] The controller 301 comprises an input means 310 and an output means 312. The input means 310 may comprise an electrical input 310 of the controller 301. The output means 312 may comprise an electrical output 312 of the controller 301. The controller 301 may have an interface 302 comprising an electrical input / output I / O 310, 312, or an electrical input 310, or an electrical output 312, for receiving information and interacting with external components. The input 310 is arranged to receive a torque request signal from a module 314. The torque request is an electrical signal whichis indicative of a pre-arbitrated requested torque of the vehicle 1 or of the EDU 208. The output 312 is arranged to output a torque control signal, indicative of a gate control signal for controlling the gate control section of the inverter 206.

[0110] FIG. 4 illustrates a non-transitory computer-readable storage medium 400 comprising the instructions (computer software).

[0111] FIG. 5 illustrates a method 500 according to an embodiment of the invention. The method 500 is a method of controlling an inverter 206 of a traction electric machine 210 of an electric drive unit 208 of a vehicle 1 , such as the vehicle 1 illustrated in FIG. 5. In particular, the method 500 is a torque arbitration method. In particular, the memory 306 may comprise computer-readable instructions 308 which, when executed by the processor 304, perform the method 500. The method 500 is performed by the inverter controller 301 of the control system 300 illustrated in FIG. 3.

[0112] Before describing the method 500 in full, some advantages are summarised below.

[0113] An advantage of hosting the method 500 in the inverter controller 301 is that the torque arbitration is carried out with low latency. Therefore, control loops can be executed at a significantly faster frequency than a vehicle communication network which has higher latency. Examples of vehicle communication networks are a Controller Area Network (CAN) bus or Flexray(TM) bus. The transport delay expected over the vehicle communication network may be greater than 100 milliseconds.

[0114] In particular, the later-described blocks 511 and 522 significantly benefit from being hosted in the inverter controller 301 , because they comprise fast control loops and therefore benefit significantly from the low latency of the inverter controller 301 .

[0115] Furthermore, the method 500 sets a particular order of priority of the arbitration blocks. If a priority were not specified, this can lead to a conflict of requests which can lead to unintended acceleration or deceleration of the EDU 208. Therefore, the method 500 is robust against conflicting requests.

[0116] In vehicles with multiple EDUs 208A, 208B as shown in FIG. 2, the method 500 may be implemented concurrently by both EDUs 208A, 208B, with messages exchanged between their respective inverter controllers 301 (501, 502, 517, 518, 519, 520).

[0117] Blocks 501 , 502, 503, 504, 505, 506, 507, 508, 510, 511 , 512, 513, 513A, 511 A, 515, 553 relate to an arbitration function 515.

[0118] The arbitration function 515 receives a torque request 508 and a plurality of torque restrictor parameters 506, 507, 511A, 513A, 553. Each of these torque restrictor parameters is a separate de-rate parameter such as a torque limit or demand. A limit as defined herein may be implemented as a ‘hard limit’ or a ‘soft limit’.

[0119] The arbitration function 515 comprises a minimum magnitude torque selector. The minimum magnitude torque selector of the arbitration function 515 is configured to determine and output a first arbitrated torque request 516 in dependence on the plurality of torque restrictor parameters 506, 507, 511 , 513A, 553 and the received torque request 508.

[0120] Specifically, the minimum magnitude torque selector arbitrates the de-rate parameters 506, 507, 511 , 513A, 553 to determine a most restrictive one of the plurality of de-rate parameters. The arbitration function 515 saturates the torque request 508 in dependence on the most restrictive one of the de-rate parameters 506, 507, 511 , 513A, 553. Therefore, the first arbitrated torque request 516 comprises a saturated torque request 508. Where the de-rate parameters may comprise torque limits, the most restrictive one may be the one with the lowest positive or negative magnitude.

[0121] The torque request 508 received by the arbitration function 515 may be a pre-arbitrated torque request. The torque request 508 may be determined, either locally or remotely, in dependence on sensed accelerator pedal depression. If the vehicle 1 is autonomously driven, the torque request 508 may be determined by an autonomous driving controller in dependence on a vehicle speed target and in dependence on machine vision sensing. If the torque request 508 is determined externally, the signal 508 may arrive at the inverter controller 301 over the vehicle communication network.Optionally, in a vehicle with multiple torque sources, the torque request 508 is an EDU torque request for the EDU 208A, split from an overall vehicle torque request by an external torque split controller (not shown). The torque split controller may split the overall vehicle torque request between the various torque sources of the vehicle, such as the EDUs 208A and 208B. The torque split controller may output an EDU torque request for each EDU 208A, 208B. The illustrated torque request 508 is for the EDU 208A but not the EDU 208B.

[0122] The de-rate parameters for saturating the torque request 508 are now described.

[0123] FIG. 5 illustrates an axle torque de-rate parameter 506 to limit a total torque produced at the axle 214 of the vehicle 1. The axle torque de-rate parameter 506 may comprise a torque limit of the total torque request for the axle 214, defined as the sum of pre-arbitrated torque requests for both EDUs 208A, 208B. This is useful for the architecture of FIG. 2 in which the EDUs 208A, 208B are configured to drive different wheels of the same axle 214 of the vehicle 1. Such an arrangement may be described as a ‘Twin EDU’ architecture. Other architectures may not require an axle torque de-rate parameter 506.

[0124] To determine the axle torque de-rate parameter 506, FIG. 5 illustrates an axle torque de-rate function 504 configured to:

[0125] - receive a first signal 501 indicative of a torque request of the host EDU 208A that the method 500 is controlling;

[0126] - receive a second signal 502 indicative of a torque request of the other EDU 208B;

[0127] - receive a third signal 503 indicative of a de-rate limit; and

[0128] - determine the axle torque de-rate parameter 506 in dependence on the signals 501 , 502, 503.

[0129] The torque request 508 may be the same as the torque request signal 501 for the host EDU 208A in which the method 500 is being executed.

[0130] In an implementation, determining the axle torque de-rate parameter 506 comprises determining whether the sum of the EDU torque requests 501 , 502 exceeds the de-rate limit 503. The de-rate limit 503 sets an axle-level torque limit to limit the total torque produced at the axle 214 of the vehicle 1. The de-rate limit 503 may be calculated by the inverter controllers 301 of both EDUs 208A, 208B.

[0131] The axle torque de-rate parameter 506 may comprise a self-inverter torque limit imposing a peak allowable torque for the inverter 206 of the host EDU 208A. The self-inverter torque limit 506 is in respective proportion to the other inverter torque request 502. The signals 502 and 506 may collectively adhere to the axle-level limit 503. For example, the self-inverter torque limit 506 may be substantially equal to the axle-level limit 503 minus the other inverter torque request 502.

[0132] The signals 501, 502 are received from one or more upstream torque requesting controllers, configured to output torque requests. The signal 503 may be received from a de-rate function within the inverter controller 301 of the host EDU 208A.

[0133] The axle torque de-rate function 504 of the inverter controller 301 of the EDU 208A may also output a second signal 505 sending the axle torque derate parameter 506 to the inverter controller 301 of the other EDU 208B. This signal 505 may be utilised in the corresponding flowchart 500 for the other EDU 208B.

[0134] FIG. 5 also illustrates an individual EDU de-rate parameter 507 to limit torque produced by the host EDU 208A separately from the other EDU 208B. The individual EDU de-rate parameter 507 is a torque limit of the requested torque of the EDU 208A, independently of the requested torque of the EDU 208B. Therefore, each EDU 208A, 208B may have a different individual EDU de-rate parameter 507.

[0135] The arbitration function 515 receives the individual EDU de-rate parameter 507 from a de-rate function within the inverter controller 301 of the host EDU 208A. For example, the de-rate function can comprise a diagnostic function configured to monitor one or more sensors of the host EDU 208A to monitor a diagnostic condition, and output an individual EDU de-rate parameter 507 in dependence on the diagnostic condition being satisfied.FIG. 5 also illustrates a traction control de-rate parameter 511 A to limit torque produced by the EDU 208 in dependence on a traction control function 511. This may comprise a torque limit or demand which is dependent on a detected difference between a sensed wheel speed of the vehicle 1 , and a sensed vehicle speed of the vehicle 1.

[0136] Traction control is usually implemented by controlling friction brakes, so it is advantageous to incorporate it within the method 500 of FIG. 5 because the EDU 208 is very responsive in comparison to friction brakes.

[0137] FIG. 5 illustrates the inverter controller 301 hosting at least part of the traction control function 511. This is advantageous compared to hosting all of the function 511 in an external controller, separated from the inverter controller 301 across the vehicle communication network. The local hosting of the function 511 allows a fast control loop for traction control, to allow rapid responses to detected traction loss events.

[0138] The traction control function 511 is configured to receive a torque request 510 for the host EDU 208. This may be the same as the torque request 508 and the torque request 501 for the host EDU 208.

[0139] Although not shown, the traction control function 511 may receive a motor speed target as well as sensed feedback indicative of the current speed of the EDU 208. The motor speed target is determined externally or internally in dependence on a detected difference between a sensed wheel speed of the wheel driven by the EDU 208, and the sensed vehicle speed. The traction control function 511 is configured to reduce the sensed wheel speed towards the sensed vehicle speed. Specifically, the traction control function 511 may be configured to determine a torque limit in dependence on the motor speed target and current speed of the EDU 208.

[0140] Then, the traction control function 511 may output a de-rate parameter 511 A such as a torque demand or limit, which is dependent on the torque request 510 and the torque limit determined above. The de-rate parameter 511A restricts the maximum allowable torque which the EDU 208 can output while the traction control function 511 is active. The de-rate parameter 511 A could comprise a negative torque limit or a much lower magnitude positive torque limit, so that if the torque request 508 is positive it will be saturated to a negative value or a low positive value. Therefore, the speed of a spinning wheel will decrease until traction is regained.

[0141] The traction control function 511 may also output a second signal 514 sending the traction control de-rate parameter 511 A to a first monitor 548, 551 which is described later.

[0142] It is not essential for the arbitration function 515 to receive all of the illustrated parameters 506, 507, 511 A, 513A, 553. One or more of the parameters could be omitted. One or more functions 504, 511 , 513, 551 for calculating the omitted parameters could therefore be omitted, or implemented outside the inverter controller 301.

[0143] FIG. 5 also shows an energy availability de-rate parameter 513A to limit torque produced by the electric drive unit 208 in dependence on a capability of an electrical energy storage apparatus 202 of the vehicle 1. This may comprise a torque limit which is dependent on an electrical power limit of the DC bus 204 and / or traction battery 202.

[0144] FIG. 5 illustrates the inverter controller 301 hosting an energy availability de-rate function 513 configured to determine the energy availability de-rate parameter 513A.

[0145] To determine the energy availability de-rate parameter 513A, the energy availability de-rate function 513 is configured to receive one or more signals 512 indicative of one or more electrical power limits associated with the traction battery 202 (and / or DC bus 204), and determine the energy availability de-rate parameter 513A in dependence on the electrical power limit or limits 512. For example, the electrical power limit 512 may be converted to a torque limit 513A.

[0146] The energy availability de-rate function 513 may be configured to receive the electrical power limit 512 from another controller of the vehicle.FIG. 5 further illustrates a first monitor 548 configured to monitor an output 547 of the arbitration function 515. The output 547 comprises the first arbitrated torque request 516.

[0147] The first monitor 548 may comprise a traction control plausibility monitor. The traction control plausibility monitor 548 may be configured to receive a first signal 547 comprising the first arbitrated torque request 516, and a second signal 514 comprising the traction control de-rate parameter 511A. The traction control plausibility monitor 548 may be configured to determine a traction control override parameter 549 in dependence on the signals 547, 514 indicating the first arbitrated torque request 516 and the traction control de-rate parameter 511A.

[0148] For example, the determination by the traction control plausibility monitor 548 may comprise determining if the first signal 547 is less than or equal to the second signal 514. The traction control override parameter may be set to ONm if signal 547 is less than signal 514, for example.

[0149] The first monitor 548 outputs the traction control override parameter 549 to a second monitor 551 , which is now described. Alternatively, the parameter 549 may be output directly to the arbitration function 515.

[0150] The second monitor 551 may comprise a vehicle stability control scheme. The second monitor 551 is configured to determine a stability intervention torque limit parameter 553 to limit torque produced by the EDU 208 in dependence on the vehicle stability control scheme. Stability in this context refers to the stability of motion of the vehicle 1 over ground, such as yaw stability.

[0151] The stability intervention torque limit parameter 553 forms one of the torque restrictor parameters input to the arbitration function 515. The effect of the second monitor 551 is therefore to ensure that the arbitration function 515 takes into account torque limit parameters for ensuring vehicle stability.

[0152] The second monitor 551 may comprise an arbitration function. The vehicle stability control scheme of the second monitor 551 may comprise an arbitration function comprising a minimum magnitude torque selector.

[0153] The minimum magnitude torque selector of the second monitor 551 receives a signal 545 indicative of the torque request 508 for the EDU 208, and also receives a plurality of torque restrictor parameters 544, 546, 549. Unlike the arbitration function 515, the minimum magnitude torque selector of the second monitor 551 is only dependent on parameters configured to control vehicle stability (544, 546, 549), and ignores parameters which are not configured to control vehicle stability (506, 507, 513A).

[0154] The parameter 549 is a traction control override parameter is as described above. The parameter 546 is an override torque request parameter, configured to impose a torque limit in dependence on a controller determining that the vehicle 1 is braking above a threshold while vehicle-accelerating torque is being requested.

[0155] The parameter 544 is indicative of a set of one or more stability control torque limits.

[0156] The minimum magnitude torque selector of the second monitor 551 arbitrates the torque limit parameters 544, 546, 549 to determine a most restrictive one of the plurality of torque limit parameters. The minimum magnitude torque selector of the second monitor 551 saturates the signal 545 indicative of the torque request 508 in dependence on the most restrictive one of the torque limit parameters 544, 546, 549. Therefore, the stability intervention torque limit parameter 553 sent to the arbitration function 515 comprises a saturated torque request. Where the torque limit parameters 544, 546, 549 may comprise torque limits, the most restrictive one may be the one with the lowest positive or negative magnitude.

[0157] FIG. 5 next illustrates an imbalance limiting function 521 after the arbitration function 515, which is configured to control torque imbalance between EDUs 208A, 208B, in implementations comprising two EDUs 208A, 208B comprising one EDU 208A coupled to a first wheel and the other EDU 208B coupled to a second wheel located on an opposite lateral side of the vehicle 1 than the first wheel (e.g., left and right wheels). In other words, the EDUs 208A, 208B are separately configured to drive wheels which are separated across the axle 214 of the vehicle 1.The imbalance limiting function 521 may be configured to further arbitrate the first arbitrated torque request 516 to prevent yaw of the vehicle 1 during driving of the vehicle 1 on surfaces with unequal surface friction beneath the first and second wheels, for example. The imbalance limiting function 521 may be configured to limit a difference in magnitude between requested output torques of the EDUs 208A, 208B.

[0158] The imbalance limiting function 521 is configured to receive the first arbitrated torque request 516, and receive one or more torque parameters 517, 518, 519, 520, wherein at least some of the torque parameters are associated with the other EDU 208B than the one which hosts the presently executed method 500.

[0159] The imbalance limiting function 521 is configured to determine a second arbitrated torque request 554 in dependence on the first arbitrated torque request 516 and the one or more torque parameters 517, 518, 519, 520.

[0160] The torque parameter 517 (same as 501) comprises the pre-arbitrated torque request of the EDU 208A. When the method 500 is executed by the inverter controller 301 of the EDU 208A, the pre-arbitrated torque request 517 of the EDU 208A may be the same as the torque request 508. When the method 500 is executed by the inverter controller 301 of the EDU 208B, the pre-arbitrated torque request 517 indicates the request for the other EDU 208A.

[0161] The torque parameter 518 comprises the arbitrated torque request of the other EDU 208B, and the torque parameter 519 comprises a clockwise torque imbalance limit and a counter-clockwise torque imbalance limit for limiting differential torque to limit vehicle yaw. The arbitrated torque request 518 of the other EDU 208B refers to the signal 554 of the flowchart 500 for the other EDU 208B.

[0162] The torque parameter 520 (same as 502) comprises the pre-arbitrated torque request of the EDU 208B.

[0163] To provide a numerical example, the pre-arbitrated torque requests 517, 520 of the EDUs 208A, 208B may both be 100 Newton-metres (Nm). The arbitrated torque requests 516, 518 of the EDUs 208A, 208B may be 40Nm, 10ONm respectively. This indicates that the EDU 208A is being requested to output a lower torque than the EDU 208B, creating a torque imbalance.

[0164] The imbalance limiting function 521 may be configured to: determine one or more torque imbalance limits; and determine the second arbitrated torque request 554 in dependence on the first arbitrated torque request 516 and the one or more torque imbalance limits. Determining the torque imbalance limits may comprise receiving the clockwise and counter-clockwise torque imbalance limits from the received signal 519.

[0165] A torque imbalance limit may comprise a range of allowable torque imbalance. The range may be in the order of tens of Nm, such as 50Nm. For example, the signal 519 may comprise the 50Nm imbalance limit. Therefore, the simultaneous torque imbalance between the EDUs 208A, 208B is not allowed to exceed 50Nm.

[0166]

[0167] The imbalance limiting function 521 may be configured to determine one or more torque limits in dependence on the one or more torque imbalance limits, and determine the second arbitrated torque request 554 in dependence on the first arbitrated torque request 516 and the one or more torque limits.

[0168] In the above example, the torque imbalance limits (±50Nm) are applied to the arbitrated torque request 518 (40Nm) of the EDU 208A. Therefore, the torque limits for the EDU 208B are 40+50=90Nm, and 40-50=-10Nm. The first arbitrated torque request 516 for the EDU 208B is therefore saturated from 100Nm down to 90Nm. The imbalance limiting function 521 therefore outputs a second arbitrated torque request 554 of 90Nm.The imbalance limiting function 521 has a higher priority than the arbitration function 515, meaning it is downstream of the function 515 and arbitrates the output 516 of the function 515 to ensure that imbalance limits are respected.

[0169] FIG. 5 further illustrates an oscillation damping function 522, 526 configured to: determine a mechanical resonance associated with the second arbitrated torque request 554; determine an anti-phase torque in dependence on the determined mechanical resonance; and determine a further torque request 555 in dependence on the anti-phase torque and the second arbitrated torque request 554.

[0170] The oscillation damping function 522, 526 may comprise a mechanical oscillation damping function, configured to damp driveline oscillations in dependence on calibration data based on torsional vibration characteristics of the driveline from the EDU 208 to the wheel. The mechanical resonant frequency of the driveline depends on the components along the torque path between the EDU 208 and the wheel.

[0171] The anti-phase torque may comprise a mechanical vibration damping torque which is applied when a frequency of the electric motor is detected to pass through a mechanical resonance range, such as 10Hz - 20Hz (varies with each motor). This helps to minimise any perceptible vibrations from the EDU 208. In an implementation, the frequency is indicated by sensed electric machine speed. An external or internal controller is configured to detect this frequency and trigger an activation request. The controller implementing the oscillation damping function 522, 526 will in response activate the logic and calculate the damping delta torque, the magnitude of which may be dependent on the frequency. Once the oscillation is back in control, the activation request may be stopped.

[0172] FIG. 6 illustrates a graph of the second arbitrated torque request 554 with respect to time, with a solid line showing the request 554 oscillating at a particular frequency.

[0173] FIG. 6 also includes a broken line illustrating an anti-phase torque which is opposite in phase, e.g., 180 degrees out of phase, with the second arbitrated torque request 554.

[0174] In FIG. 5, the anti-phase torque is determined by the anti-phase torque calculation block 522. The calculation block 522 outputs a torque delta (antiphase torque) to the summation block 526, which sums the second arbitrated torque request 554 with the anti-phase torque. The output of the summation block 526 is defined as a further torque request 555.

[0175] The anti-phase torque calculation block 522 of the oscillation damping function 522 may work by receiving the sensed feedback indicative of the current speed of the EDU 208A, and determining the anti-phase torque in dependence on the current speed of the EDU 208A.

[0176] The oscillation damping function 522, 526 is downstream of the function 521 and arbitrates the output 554 of the function 521. This beneficially ensures that balancing has been carried out before the anti-phase torque is applied. If the anti-phase torque were applied before the oscillation damping function 522, 526, some of the anti-phase torque may be sent to the inverter 206 of the other EDU 208B, causing unintended torque to be produced by the other EDU 208B.

[0177] However, it is possible for the oscillation damping function 522, 526 to arbitrate the output 516 of the function 515 instead. Suitable measures can be provided to prevent the issues described above.

[0178] The anti-phase torque calculation block 522 of the oscillation damping function 522, 526 may be configured to perform arbitration of a plurality of received parameters. For example, the anti-phase torque calculation block 522 may be configured to receive the second arbitrated torque request 554, and an override parameter 530 from a damping function monitor 528 which is described below. The anti-phase torque calculation block 522 may be configured to arbitrate between the anti-phase torque and the override parameter 530.

[0179] The damping function monitor 528 may comprise a plausibility monitor to monitor the output 555 of the oscillation damping function 522, 526, and control the oscillation damping function 522, 526 in dependence on the monitored output. The damping function monitor 528 receives a signal 527indicating the further torque request 555 of the oscillation damping function 522, 526. The damping function monitor 528 may also receive a signal 529 indicating the second arbitrated torque request 554.

[0180] In an implementation, the damping function monitor 528 monitors the difference between the signals 527 and 529, determines whether the difference is within an allowable limit, and outputs an override parameter 530 to the anti-phase torque calculation block 522 of the oscillation damping function 522, 526 in dependence on whether the allowable limit is exceeded.

[0181] The damping function monitor 528 may also receive a signal 535 indicating the output of a later-described torque limiter 531 , 532. This allows the damping function monitor 528 to detect whether the downstream torque limiter 531 , 532 is saturating the torque request 555. The override parameter 530 from the damping function monitor 528 to the anti-phase torque calculation block 522 may depend on said signal 535.

[0182] In an example implementation, the override parameter 530 comprises an error flag, such as a Boolean value. The error flag may indicate an error state in dependence on whether the allowable limit is exceeded. The error flag may be conditionally sent and / or may indicate error and non-error states.

[0183] The anti-phase torque calculation block 522 may be configured to inhibit the anti-phase torque in dependence on receiving the error flag indicating the error state. For example, the anti-phase torque may be set to zero.

[0184] Moving downstream through the flowchart, FIG. 5 further illustrates a torque magnitude limiter 531, 532 configured to: determine a fixed torque magnitude limit or limits (e.g., positive and negative torque limits); and determine a saturated torque request in dependence on the fixed torque magnitude limit and the further torque request 555. The block 531 is a calculation block to determine the fixed torque magnitude limit. The block 532 is configured to saturate the request 555 in dependence on the fixed torque magnitude limit 531.

[0185] The torque magnitude limiter 531, 532 may have a higher priority than the functions 515, 521, 522 by being implemented downstream of them. The fixed torque magnitude limit may be a predetermined ‘never exceed’ hardware protection limit for the EDU 208. Therefore, the torque magnitude limiter is placed close to the end of the flowchart, just in case any of the upstream operations 515, 521 , 526 increase the original torque request 508 beyond the ‘never exceed’ limit. For example, the oscillation damping function 522, 526 can request additional torque rather than just decreasing torque. Therefore, the torque magnitude limiter 531 , 532 is located downstream of the oscillation damping function 522, 526.

[0186] FIG. 7 illustrates an example of a waveform of a torque request after application of the torque magnitude limiter 531 , 532. The peaks of the waveform are clipped.

[0187] FIG. 5 further illustrates a torque ripple mitigation function 533 configured to: determine an anti-ripple torque in dependence on an output of the torque magnitude limiter 531 , 532; and determine a modified torque request 556 in dependence on the anti-ripple torque and the torque request output by the limiter 531, 532.

[0188] Unlike the oscillation damping function 522, 526 which is for mechanical vibrations, the torque ripple mitigation function 533 is configured to control electrical ripple in the inverter 206, by applying an anti-ripple torque to cancel out electrical harmonics associated with switching voltages of the inverter 206.

[0189] Although it is not essential to include both mechanical and electrical damping functions 522, 526 and 533, their combined use provides optimal minimisation of vibrations from the EDU 208 across a wide range of operating conditions. Some implementations may comprise one of, or neither of these functions.

[0190] FIG. 5 further illustrates a second torque magnitude limiter 531, 534, configured to apply the fixed torque limit to the modified torque request 556 output from the torque ripple mitigation function 533, just in case the function 533 increased the magnitude beyond the fixed limit. The arbitration block 534 is similar to the block 532, and it is shown as being connected to the calculation block 531.The torque limiter is applied twice (532, 534), to either side of the torque ripple mitigation function 533, because if it is applied only at block 534, the damping function monitor 528 would not be able to determine whether torque has been limited at block 534 due to the oscillation damping function 522, 526 or due to the torque ripple mitigation function 533.

[0191] In some implementations, one of the torque limiter blocks 532 or 534, or both of them, may be omitted. If they are both omitted, the calculation block 531 can be omitted.

[0192] FIG. 5 further illustrates a torque control signal block 536 which is configured to output a control signal 557 (torque control signal) to the inverter 206 in dependence on the torque request output from the final block, which in FIG. 5 is the second torque magnitude limiter 531, 534. If FIG. 5 is implemented in full, the control signal is arbitrated and / or modified by the blocks 515, 521 , 526, 532, 533, and 534.

[0193] The block 536 may comprise a torque-to-current block configured to determine the control signal 557 in the form of gate control signals (electrical currents) to control the gate control section of the inverter 206.

[0194] In summary, the various blocks 515, 521 , 526, 532, 533, 534 collectively define a method 500 comprising:

[0195] in an arbitration function 515:

[0196] receiving a torque request 508;

[0197] receiving a plurality of torque restrictor parameters 506, 507, 511 A, 513A, 553;

[0198] determining, in an arbitration function 515 of the inverter controller 301 of the EDU 208 (e.g. , EDU 208A), a first arbitrated torque request 516 in dependence on the plurality of torque restrictor parameters 506, 507, 511 A, 513A, 553 and the received torque request 508; in an imbalance limiting function 521 downstream of the arbitration function 515:

[0199] receiving one or more torque parameters 517 or 518, 519, 520 associated with a different EDU 208B coupled to a wheel located on an opposite lateral side of the vehicle 1 to a wheel coupled to the EDU 208A;

[0200] determining a second arbitrated torque request 554 in dependence on the first arbitrated torque request 516, and the one or more torque parameters 517, 518, 519, 520;

[0201] in an oscillation damping function 522, 526:

[0202] determining a mechanical resonance associated with the second arbitrated torque request 554;

[0203] determining an anti-phase torque in dependence on the determined mechanical resonance;

[0204] determining a further torque request 555 in dependence on the anti-phase torque and the respective second arbitrated torque request 554;

[0205] in a first torque magnitude limiter 532:

[0206] determining a fixed torque magnitude limit;

[0207] determining a saturated torque request in dependence on the fixed torque magnitude limit and the further torque request 555, in a torque ripple mitigation function 533:

[0208] determining an anti-ripple torque in dependence on the saturated torque request; and

[0209] determining a modified torque request 556 in dependence on the anti-ripple torque and the saturated torque request,

[0210] in a second torque magnitude limiter 532:

[0211] determining a fixed torque magnitude limit; and

[0212] determining a second saturated torque request in dependence the fixed torque magnitude limit and the modified torque request 556; and outputting a torque control signal 557 in dependence on the first arbitrated torque request 516, the second arbitrated torque request 554, the further torque request 555, the saturated torque request, the modified torque request 556, and the second saturated torque request.

[0213] Any one or more of the above functions / limiters may be omitted.

[0214] The above method 500 also sets a particular order of the functions / limiters. Reasons are given earlier in the document about why some functions / limiters may advantageously come before or after others. If an advantage is not specified, then there is no reason for the order to be asdescribed. Furthermore, even if an advantage to a particular order has been mentioned, this does not mean that this order / prionty is essential for all implementations of the invention.

[0215] It is to be understood that the or each controller 301 can comprise a control unit or computational device having one or more electronic processors (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.), and may comprise a single control unit or computational device, or alternatively different functions of the or each controller 301 may be embodied in, or hosted in, different control units or computational devices. As used herein, the term “controller,” “control unit,” or “computational device” will be understood to include a single controller, control unit, or computational device, and a plurality of controllers, control units, or computational devices collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause the controller 301 to implement the control techniques described herein (including some or all of the functionality required for the method(s) described herein) . The set of instructions 308 could be embedded in said one or more electronic processors 304 of the controller 301 ; or alternatively, the set of instructions 308 could be provided as software to be executed in the controller 301. A first controller or control unit may be implemented in software run on one or more processors. One or more other controllers or control units may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller or control unit. Other arrangements are also useful.

[0216] The, or each, electronic processor 304 may comprise any suitable electronic processor (e.g., a microprocessor, a microcontroller, an ASIC, etc.) that is configured to execute electronic instructions 308. The, or each, electronic memory device 306 may comprise any suitable memory device and may store a variety of data, information, threshold value(s), lookup tables or other data structures, and / or instructions therein or thereon. In an embodiment, the memory device 306 has information and instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored therein or thereon that may govern all or part of the methodology described herein. The processor, or each, electronic processor 304 may access the memory device 306 and execute and / or use that or those instructions and information to carry out or perform some or all of the functionality and methodology described herein.

[0217] The at least one memory device 306 may comprise a computer-readable storage medium (e.g. a non-transitory or non-transient storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors / computational devices. Examples of the form include, 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 ad EEPROM); flash memory; or electrical or other types of medium for storing such information / instructions.

[0218] It will be appreciated that embodiments of the present invention can be realised in any suitable form of hardware, software or a combination of hardware and software. For example, it is contemplated that the present invention is not limited to being implemented by way of programmable processing devices, and that at least some of, and in some embodiments all of, the functionality and or method steps of the present invention may equally be implemented by way of non-programmable hardware, such as by way of non-programmable ASIC, Boolean logic circuitry, etc.

[0219] 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. For example, some or all of the method 500 may be implemented by a control system 300 without an inverter controller 301.

[0220] The blocks illustrated in FIG. 5 may represent steps in a method and / or sections of code in the computer program 308. 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.

[0221] 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.

Claims

1. CLAIMS1. An electric drive unit for a vehicle, comprising an inverter controller for controlling an inverter for a traction electric machine of the electric drive unit, the inverter controller comprising one or more processors collectively configured to:receive a torque request;receive a plurality of torque restrictor parameters;determine, in an arbitration function of the inverter controller, a first arbitrated torque request in dependence on the plurality of torque restrictor parameters and the received torque request; andoutput a torque control signal in dependence on the first arbitrated torque request.

2. The electric drive unit of claim 1, wherein the plurality of torque restrictor parameters comprise a plurality of de-rate parameters, and wherein the arbitration function is configured to:arbitrate the de-rate parameters to determine a most restrictive one of the plurality of de-rate parameters; anddetermine the first arbitrated torque request in dependence on the most restrictive one of the plurality of de-rate parameters and the torque request.

3. The electric drive unit of claim 1 or 2, wherein the plurality of torque restrictor parameters comprise any two or more of:an axle torque de-rate parameter to limit a total torque produced at an axle of the vehicle; andan individual electric drive unit de-rate parameter to limit torque produced by the electric drive unit separately from another electric drive unit;a traction control de-rate parameter to limit torque produced by the electric drive unit in dependence on a traction control function; an energy availability de-rate parameter to limit torque produced by the electric drive unit in dependence on a capability of an electrical energy storage apparatus of the vehicle; ora stability intervention de-rate parameter to limit torque produced by the electric drive unit in dependence on a vehicle stability control scheme.

4. The electric drive unit of claim 3, wherein the inverter controller hosts at least part of the traction control function configured to determine the traction control de-rate parameter in dependence on sensed feedback indicating one or more state parameters of the electric drive unit.

5. The electric drive unit of any preceding claim, the inverter controller comprising a first monitor to check an output of the arbitration function, and output a de-rate parameter to the arbitration function in dependence on the checked output.

6. The electric drive unit of any preceding claim, the inverter controller comprising an imbalance limiting function configured to:receive one or more torque parameters associated with a different electric drive unit coupled to a wheel located on an opposite lateral side of the vehicle to a wheel coupled to the electric drive unit; anddetermine a second arbitrated torque request in dependence onthe first arbitrated torque request, andthe one or more torque parameters, andwherein the inverter controller is configured to output the torque control signal in dependence on the second arbitrated torque request.

7. The electric drive unit of claim 6, the inverter controller comprising an oscillation damping function configured to:determine a mechanical resonance associated with the first or second arbitrated torque request;determine an anti-phase torque in dependence on the determined mechanical resonance; anddetermine a further torque request in dependence on the anti-phase torque and the respective first or second arbitrated torque request, wherein the inverter controller is configured to output the torque control signal in dependence on the further torque request.

8. The electric drive unit of claims 6 and 7 in combination, wherein the oscillation damping function is downstream of the imbalance limiting function.

9. The electric drive unit of claim 7 or 8, the inverter controller comprising a damping function monitor to receive an output of the oscillation damping function, and output an override parameter to the oscillation damping function in dependence on the output of the oscillation damping function, and wherein the oscillation damping function is configured to determine the anti-phase torque in dependence on the override parameter.

10. The electric drive unit of claim 7, 8, or 9, the inverter controller comprising a torque ripple mitigation function configured to:determine an anti-ripple torque in dependence on an output of the oscillation damping function; anddetermine a modified torque request in dependence on the anti-ripple torque and the further torque request, andwherein the inverter controller is configured to output the torque control signal in dependence on the modified torque request.

11. The electric drive unit of any preceding claim, the inverter controller comprising a torque magnitude limiter configured to:determine a fixed torque magnitude limit;determine a saturated torque request in dependence on the fixed torque magnitude limit and an arbitrated torque request, and wherein the inverter controller is configured to output the torque control signal in dependence on the saturated torque request.

12. A system comprising an electric drive unit according to any one of the preceding claims, the electric drive unit comprising the inverter, the traction electric machine, and the inverter controller.

13. A vehicle comprising the system of claim 12 or the electric drive unit of any one of claims 1 to 11 .

14. A method of controlling an inverter of an electric drive unit of a vehicle, the method comprising:receiving a torque request;receiving a plurality of torque restrictor parameters;determining, in an arbitration function of an inverter controller of the electric drive unit, a first arbitrated torque request in dependence on the plurality of torque restrictor parameters and the received torque request; andoutputting a torque control signal in dependence on the first arbitrated torque request.

15. Computer readable instructions which, when executed by a computer, are arranged to perform a method according to claim 14.

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