Patent Publication Number: US-2023159017-A1

Title: Control system and method for controlling electrical power consumption by traction motor caused by wheel slip

Description:
TECHNICAL FIELD 
     The present disclosure relates to controlling electrical power consumption caused by wheel slip. In particular, but not exclusively, it relates to controlling electrical power consumption from energy storage means by a traction motor of a vehicle caused by a wheel slip event. 
     BACKGROUND 
     While driving on surfaces with a variable coefficient of friction, for example, one or more wheels of a vehicle may slip and so accelerate. 
     Since the inertia of an electric drive system is relatively low compared with the inertia of a convention engine and transmission system, the speed of wheels powered by an electric drive system can increase rapidly during a wheel slip event. 
     In conventional traction control systems, driving torque is reduced as soon as slip is detected. Due to higher inertia in conventional engine and transmission systems the wheels do not reach high speeds and so the time to respond to the wheel slip event is not so critical and the decelerating power requirement is also not high. 
     However, in electric drive systems, due to the low inertia of the system, the wheels can accelerate rapidly during a wheel slip event causing a rapid increase of electrical power consumption that can, for example, exceed the capability of the traction battery to deliver the required power. 
     SUMMARY OF THE INVENTION 
     It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. 
     Aspects and embodiments of the invention provide a control system, a vehicle system, a vehicle, a method, and computer software. 
     According to an aspect of the invention there is provided a control system for controlling electrical power consumption from energy storage means by a traction motor of a vehicle caused by a wheel slip event, the control system comprising one or more electronic controllers, the one or more electronic controllers configured to: receive a torque request for the traction motor; determine a prevailing speed value of the traction motor; determine a maximum allowable increase in speed of the traction motor to occur during a latency period associated with the prevailing speed value of the traction motor; determine an electrical power consumption limit in dependence on the torque request, the prevailing speed value of the traction motor and the maximum allowable increase in speed of the traction motor; and control torque provision of the traction motor in dependence on the torque request and the electrical power consumption limit. 
     The control system can prevent power consumption in excess of the capability of the battery. This can, therefore, prevent battery damage and/or intrusive battery protection features of a vehicle being activated. 
     The one or more controllers may collectively comprise: at least one electronic processor having an electrical input for receiving information associated with a torque request for the traction motor of the vehicle, determining a prevailing speed value of the traction motor, determining a maximum allowable increase in speed of the traction motor and determining an electrical power consumption limit; and at least one electronic 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 cause the control system to determine the prevailing speed value of the traction motor, determine the maximum allowable increase in speed of the traction motor, determine the electrical power consumption limit and control torque provision of the traction motor. 
     Determining a maximum allowable increase in speed of the traction motor may comprise determining a prevailing speed of the vehicle and determining the maximum allowable increase in speed of the traction motor in dependence on the prevailing speed of the vehicle. 
     Determining a maximum allowable increase in speed of the traction motor may comprise accessing at least one data structure in dependence on the prevailing speed of the vehicle. 
     Determining an electrical power consumption limit may comprise accessing at least one data structure in dependence on the torque request, the prevailing speed value of the traction motor and the maximum allowable increase in speed of the traction motor. 
     The at least one data structure may account for efficiencies in provision of torque by the traction motor. 
     The electrical power consumption limit may comprise a limit in terms of electrical current and/or power to be supplied to the traction motor. 
     The electrical power consumption limit may comprise a limit in terms of electrical current and/or power to be drawn from the energy storage means by the traction motor. 
     The latency period of the prevailing speed value of the traction motor may be approximately 50 to 100 milliseconds. 
     Controlling torque provision may comprise transmitting the torque request and electrical power consumption limit to control torque provision. 
     Controlling torque provision may comprise determining a speed value of the traction motor having a lower associated latency and determining a torque limit in dependence on the lower latency speed value of the traction motor, the torque request and the electrical power consumption limit. 
     According to an aspect of the invention there is provided a vehicle system comprising the control system, a traction motor and energy storage means. 
     According to an aspect of the invention there is provided a vehicle comprising the control system and/or the vehicle system. 
     According to an aspect of the invention there is provided a method for controlling electrical power consumption from energy storage means by a traction motor of a vehicle caused by a wheel slip event, the method comprising: receiving a torque request for the traction motor of the vehicle; determining a prevailing speed value of the traction motor; determining a maximum allowable increase in speed of the traction motor to occur during a latency period associated with the prevailing speed value of the traction motor; determining an electrical power consumption limit in dependence on the torque request, the prevailing speed value of the traction motor and the maximum allowable increase in speed of the traction motor; and 
     controlling torque provision of the traction motor in dependence on the torque request and the electrical power consumption limit. 
     Determining a maximum allowable increase in speed of the traction motor may comprise determining a prevailing speed of the vehicle and determining the maximum allowable increase in speed of the traction motor in dependence on the prevailing speed of the vehicle. 
     Determining a maximum allowable increase in speed of the traction motor may comprise accessing at least one data structure in dependence on the prevailing speed of the vehicle. 
     Determining an electrical power consumption limit may comprise accessing at least one data structure in dependence on the torque request, the prevailing speed value of the traction motor and the maximum allowable increase in speed of the traction motor. 
     The at least one data structure may account for efficiencies in provision of torque by the traction motor. 
     The electrical power consumption limit may comprise a limit in terms of electrical current and/or power to be supplied to the traction motor. 
     The electrical power consumption limit may comprise a limit in terms of electrical current and/or power to be drawn from the energy storage means by the traction motor. 
     The latency period of the prevailing speed value of the traction motor may be approximately 50 to 100 milliseconds. 
     Controlling torque provision may comprise transmitting the torque request and electrical power consumption limit to control torque provision. 
     Controlling torque provision may comprise determining a speed value of the traction motor having a lower associated latency and determining a torque limit in dependence on the lower latency speed value of the traction motor, the torque request and the electrical power consumption limit. 
     According to an aspect of the invention there is provided a non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, perform the method of at least one or more methods described herein. 
     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 following description and/or drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG.  1    illustrates an example of a vehicle; 
         FIG.  2 A  schematically illustrates an example of a control system; 
         FIG.  2 B  schematically illustrates an example of a non-transitory computer readable medium; 
         FIG.  3    schematically illustrates an example of a system; 
         FIG.  4    illustrates an example of a method; 
         FIG.  5    illustrates an example of a control system; and 
         FIG.  6    illustrates an example of controlling electrical power consumption from energy storage means by a traction motor of a vehicle caused by a wheel slip event. 
     
    
    
     DETAILED DESCRIPTION 
     Examples of the present disclosure relate to controlling electrical power consumption from energy storage means by a traction motor of a vehicle caused by a wheel slip event. 
     In examples, the energy storage means can be any suitable energy storage means to power one or more electric traction motors or traction motors of the vehicle to propel the vehicle. 
     In examples, the energy storage means can be considered: one or more components configured to store energy, energy storage circuitry, energy storage apparatus, energy storage mechanism and so on. 
     In examples, the energy storage means comprises or is one or more traction batteries which may be one or more high voltage batteries. 
     In examples, an electrical power consumption limit is determined and torque provision of the traction motor controlled in dependence on a torque request and the electrical power consumption limit. 
     For example, it can prevent power consumption in excess of the capability of the battery. This can, therefore, prevent battery damage and/or intrusive battery protection features of a vehicle being activated. 
     One or more of the features discussed in relation to  FIGS.  1 ,  2 A,  2 B and  3    can be found in the other figures. 
       FIG.  1    illustrates an example of a vehicle  10  in which embodiments of the invention can be implemented. In the illustrated example, the vehicle  10  is a hybrid electric vehicle (HEV). 
     In some, but not necessarily all, examples, the vehicle  10  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 industrial vehicles. 
     In examples, the hybrid electric vehicle has an electric only mode of propulsion among other modes of propulsion. In examples, the HEV is configured to operate as a parallel HEV. Parallel HEVs comprise a torque path between the engine and a least one vehicle wheel, as well as a torque path between an electric traction motor and at least one vehicle wheel. The torque path(s) may be disconnectable via a torque path connector such as a clutch. Parallel HEVs differ from series HEVs, because in series HEVs the purpose of the engine is to generate electrical energy and there is no torque path between the engine and the vehicle wheels. 
     The vehicle  10  comprises at least one traction motor  14 , energy storage means  16  and a control system  12  as described herein. The control system  12  is configured to operate as described herein. 
     Accordingly,  FIG.  1    illustrates a vehicle  10  comprising a control system  12  as described herein. 
       FIG.  2 A  illustrates an example of a control system  12 . 
     In the illustrated example, the control system  12  is a control system  12  for controlling electrical power consumption from energy storage means  16  by a traction motor  14  of a vehicle  10  caused by a wheel slip event. 
     In examples, any suitable control system  12  for controlling electrical power consumption from energy storage means  16  by a traction motor  14  of a vehicle  10  caused by a wheel slip event can be used. 
     The control system  12  of  FIG.  2 A  comprises an electronic controller  18 . In other examples, the control system  12  comprises a plurality of electronic controllers  18  on-board and/or off-board the vehicle  10 . 
     The electronic controller  18  of  FIG.  2 A  comprises at least one electronic processor  24  and at least one electronic memory device  28  coupled to the at least one electronic processor  24  and having instructions  31  (for example a computer program) stored therein, the at least one electronic memory device  28  and the instructions  31  configured to, with the at least one electronic processor  24 , cause any one or more of the method or methods described herein to be performed. 
     Accordingly,  FIG.  2 A  illustrates a control system  12  for controlling electrical power consumption from energy storage means  16  via a traction motor  14  of a vehicle  10  caused by a wheel slip event, the control system  12  comprising one or more electronic controllers  18 , the one or more electronic controllers  18  configured to: 
     receive a torque request  616  for the traction motor  14 ; 
     determine a prevailing speed value of the traction motor  14 ; 
     determine a maximum allowable increase in the speed of the traction motor  14  to occur during a latency period associated with the prevailing speed value of the traction motor  14 ; 
     determine an electrical power consumption limit  606  in dependence on the torque request  616 , the prevailing speed value of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14 ; and 
     control torque provision of the traction motor  14  in dependence on the torque request  616  and the electrical power consumption limit  606 . 
     Furthermore,  FIG.  2 A  therefore illustrates a control system  12 , wherein the one or more controllers  18  collectively comprise: 
     at least one electronic processor  24  having an electrical input for receiving information associated with a torque request  616  for the traction motor  14  of the vehicle  10 , determining a prevailing speed value of the traction motor  14 , determining a maximum allowable increase in speed of the traction motor  14  and determining an electrical power consumption limit  606 ; and 
     at least one electronic memory device  28  electrically coupled to the at least one electronic processor  24  and having instructions  31  stored therein; and wherein the at least one electronic processor  24  is configured to access the at least one memory device  28  and execute the instructions  31  thereon so as to cause the control system  12  to determine a prevailing speed value of the traction motor  14 , determine a maximum allowable increase in speed of the traction motor  14 , determine an electrical power consumption limit  606  and control torque provision of the traction motor  14 . 
     In examples the prevailing speed value can be considered to be the current speed value of the traction motor  14  received or known by the control system  12  or a controller  18  of the control system  12 . 
       FIG.  2 B  illustrates a non-transitory computer readable storage medium  40  comprising the instructions  31  (computer software). 
     Accordingly,  FIG.  2 B  illustrates a non-transitory computer readable medium  40  comprising computer readable instructions  31  that, when executed by a processor  24 , perform the method of  FIG.  4    and/or as described herein. 
       FIG.  3    schematically illustrates an example of a system  38 . The system  38  can be considered a vehicle system  38 . 
     In the illustrated example, the system  38  is a system  38  for controlling electrical power consumption from energy storage means via a traction motor  14  of a vehicle  10  caused by a wheel slip event. 
     In the example of  FIG.  3   , the system  38  comprises a control system  12  which may be as described in relation to  FIG.  2 A . 
       FIG.  3    also illustrates an example of a vehicle  10 , such as a hybrid electric vehicle, comprising a control system  12  as described herein or a vehicle system  38  as described herein. 
     In the example of  FIG.  3   , the vehicle system  38  comprises one or more traction motors  14  and one or more vehicle systems  42 . The one or more vehicle systems  42  can be considered one or more further vehicle system(s)  42 . 
     In the example of  FIG.  3   , the control system  12  provides means for controlling operation of the system  38 . However, in examples, any suitable means for controlling operation of the system  38  can be used. 
     The control system  12  of  FIG.  3    may comprise one or more of: a hybrid powertrain control module; an engine control unit; a transmission control unit; a traction battery management system; and/or the like. 
     As illustrated in the example of  FIG.  3   , the elements  14  and  42  are operationally coupled to the control system  12  and any number or combination of intervening elements can exist between them (including no intervening elements). 
     In some examples, the elements  14  and  42  are operationally coupled to each other and/or share one or more components. Additionally, or alternatively, the element  14  and/or  42  may be operationally coupled to and/or share one or more components with other elements not illustrated in the example of  FIG.  3   . 
     In examples, the one or more traction motor motors  14  can comprise or be any suitable traction motor(s)  14 . 
     In some examples, the traction motor(s)  14  may be an alternating current induction motor or a permanent magnet motor, another type of motor or a combination thereof. 
     In examples, any suitable traction motor(s)  14  suitable for providing torque to drive one or more wheels of the vehicle  10  can be used. In examples, the traction motor(s)  14  is configured to enable at least an electric vehicle mode comprising electric only driving. 
     In some examples, a traction motor  14  can be considered an electric driver unit or electric traction motor. 
     In some examples, the traction motor(s)  14  is configured to drive an electric only axle of vehicle  10  to enable all-wheel drive of the vehicle  10  in combination with a second axle driven by an internal combustion engine. 
     In examples, the control system  12  provides means to control, at least in part, directly or indirectly, operation of the traction motor(s)  14 . Information may be transmitted between the control system  12  and the traction motor(s). For example, control information may be transmitted from the control system  12  to the traction motor(s)  14  and/or information from the traction motor(s)  14  transmitted to the control system  12 . 
     This is illustrated in the example of  FIG.  3    by the double headed arrow linking the traction motor(s)  14  and the control system  12 . 
     In examples, the one or more vehicle systems  42  are or comprise any suitable vehicle system(s)  42  of the vehicle  10 . For example, the one or more vehicle systems  42  may comprise any suitable vehicle system(s)  42  of the vehicle  10 , controllable, at least in part, directly or indirectly, by the control system  12 . 
     In examples, the one or more vehicle systems  42  may be considered further vehicle systems in the vehicle system  38 . 
     In some examples, the one or more vehicle systems  42  may be considered to be further vehicle system(s)  42  separate from, but controlled, at least in part, directly or indirectly, by the vehicle system  38 . 
     The one vehicle systems  42  can comprise any suitable vehicle system or systems  42  from which a torque request  616  for the traction motor(s)  14  can be received. 
     For example, a torque request  616  may come from a physical driver of the vehicle  10 , that is a person who interacts with one or more accelerator controls of the vehicle  10 , and/or one or more virtual drivers of the vehicle  10 . 
     In examples, virtual drivers can form at least part of any driver assistance system such as one or more advanced driver assistance systems (ADAS), for example, a cruise control system, an autonomous cruise control system, park assist, an all-terrain progress control system (ATPC), all-surface progress control (ASPC), vehicle speed limiter, intelligent speed limiter and so on. An example of all-terrain progress control system (ATPC) or all-surface progress control (ASPC) is described in GB2507622. 
     In examples, the one or more vehicle systems  42  comprise electrical energy storage means  16  configured to store electrical power for the traction motor(s)  14 . 
     In examples, the energy storage means  16  comprises or is one or more traction batteries (not illustrated). The traction battery or batteries provide a nominal voltage required by electrical power users such as the traction motor(s)  14 . 
     In examples, the traction motor(s)  14  is configured to receive electrical energy from the traction battery of the vehicle system(s)  42 . 
     The traction battery may be a high voltage battery. High voltage traction batteries provide nominal voltages in the hundreds of volts. The traction battery may have a voltage and capacity to support electric only driving for sustained distances. The traction battery may have a capacity of several kilowatt hours to maximize range. The capacity may be in the tens of kilowatt hours, or even over a hundred kilowatt hours. 
     In examples, the function of the traction battery can be implemented using a plurality of small traction batteries in different locations on the vehicle  10 . 
     Accordingly,  FIG.  3    also illustrates a vehicle system  38  comprising a control system  12  as described herein, a traction motor  14  and energy storage means  16 . 
     In examples, the vehicle system(s)  42  provides one or more inverters for each traction motor  14 . 
     In examples, the control system  12  provides means to control, at least in part, directly or indirectly, of the one or more vehicle systems  42 . Information may be transmitted between the control system  12  and the one or more vehicle systems  42 . For example, control information may be transmitted from the control system  12  to the one more vehicle systems  42  and/or information from the one or more vehicle systems  42 , such as one or more torque requests  616 , transmitted to the control system  12 . 
     This is illustrated in the example of  FIG.  3    by the double headed arrow linking the one or more vehicle systems  42  and the control system  12 . 
     In examples, the control system  12  provides means for controlling the elements of the vehicle system  38 . The control system  12  may be configured to control the elements of the vehicle system  38  using one or more wired or wireless network systems/protocols. For example, USB, HDMI, Bluetooth, WiFi, CAN, LIN, I2C, FNET, FBD-LINK, UART, SBI, Flexray and so on may be used. 
     The vehicle system may comprise any number of additional elements not illustrated in the example of  FIG.  3   . Additionally, or alternatively, one or more elements of the vehicle system  38  illustrated in the example of  FIG.  3    may be integrated and/or combined. For example, one or more of the vehicle systems  42  and the traction motor(s)  14  may be at least partially combined. 
     In some examples, one or more of the elements illustrated in the example of  FIG.  3    may be omitted from the vehicle system  38 . 
       FIG.  4    illustrates an example of a method  400 . The method  400  is for controlling electrical power consumption from energy storage means  16  by a traction motor  14  of a vehicle  10  caused by a wheel slip event. 
     In examples, the vehicle  10  can be a vehicle  10  as illustrated in  FIGS.  1  and/or  3   . 
     In examples, the method  400  is performed by the control system  12  of  FIG.  2 A or  3    and/or as described herein or the vehicle system  38  of  FIG.  3    and/or as described herein. 
     That is, in examples, the control system  12  described herein comprises means for performing the method  400 . However, any suitable means can be used to perform the method  400 . 
     In examples, the method  400  can be considered a computer implemented method  400 . 
     The method  400  is for controlling electrical power consumption from energy storage means  16  by a traction motor  14  of a vehicle  10  caused by a wheel slip event, the method  400  comprising: 
     receiving a torque request  616  for the traction motor  14  of the vehicle  10 ; 
     determining a prevailing speed value of the traction motor  14 ; 
     determining a maximum allowable increase in speed of the traction motor  14  to occur during a latency period associated with the prevailing speed value of the traction motor  14 ; 
     determining an electrical power consumption limit  606  in dependence on the torque request  616 , the prevailing speed value of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14 ; and 
     controlling torque provision of the traction motor  14  in dependence on the torque request  616  and the electrical power consumption limit  606 . 
     At block  402 , the method  400  comprises receiving a torque request  616  for the traction motor  14  of the vehicle  10 . 
     Any suitable method for receiving a torque request  616  for the traction motor  14  of the vehicle  10  can be used. 
     For example, the torque request  606  can be received in any suitable way. 
     In some examples, the control system  12  receives one or more signals comprising information indicative of the torque request  606 . For example, the control system  12  can receive one or more signals comprising information indicative of the torque request  606  from one or more of the vehicle systems  42  of  FIG.  3   . 
     That is, in examples, the torque request  606  can be received by the control system  12  in dependence on a demand from a driver and/or virtual driver of the vehicle  10 . 
     At block  404 , the method  400  comprises determining a prevailing speed value of the traction motor  14 . 
     Any suitable method for determining a prevailing speed value of the traction motor  14  can be used. 
     In examples, the prevailing speed value of the traction motor  14  is received by the control system  12  from the traction motor  14 . The prevailing speed value of the traction motor  14  can be provided in any suitable way and/or in any suitable format. In some examples, the prevailing speed value of the traction motor  14  can be provided in terms of revolutions per minute (RPM). 
     In examples, there can be a lag in receiving the prevailing speed value of the traction motor  14  at the control system  12  compared to the actual, current, instantaneous speed value of the traction motor  14 . 
     For example, there can be a delay in the information concerning the speed value of the traction motor  14  reaching the control system  12  and therefore the actual, instantaneous speed value of the traction motor  14  can change during the delay period. 
     Accordingly, the speed value of the traction motor  14  received at the control system  12  can be considered a prevailing speed value as the actual, instantaneous speed value of the traction motor  14  can have changed since the received information was transmitted. It can therefore be understood that the prevailing speed value of the traction motor  14  has an associated latency period and that in the associated latency period the actual, instantaneous speed value of the traction motor  14  can change. 
     In examples, the latency period of the prevailing speed value of the traction motor  14  is approximately 50 to 100 milliseconds. 
     In some examples, the latency period of the prevailing speed value of the traction motor  14  is approximately 70 to 90 milliseconds. 
     In examples, the control system  12  comprises multiple electronic controllers  18 . In such examples, one or more electronic controllers  18  can be responsible for and/or associated with one or more actions and/or controls. 
     In some examples, one or more controllers  18 , responsible for determining available torque for a prevailing speed value of the traction motor  14  can be separate from the one or more controllers  18  responsible for controlling the traction motor  14 . See, for example,  FIG.  5   . 
     In such examples, a delay can be introduced in providing information from the traction motor  14  to the controller(s)  18  responsible for determining available torque and passing control information to controller(s)  18  responsible for controlling the traction motor  14 . 
     In such examples, this can result in the prevailing speed value known by the controller(s)  18  responsible for determining available torque having an associated latency period. 
     At block  406 , the method  400  comprises determining a maximum allowable increase in speed of the traction motor  14  to occur during a latency period associated with the prevailing speed value of the traction motor  14 . 
     Any suitable method for determining a maximum allowable increase in the speed of the traction motor  14  to occur during the latency period associated with the prevailing speed value of the traction motor  14  can be used. 
     In examples, determining a maximum allowable increase in speed of the traction motor  14  to occur during the latency period comprises determining the increase in speed of the traction motor that is feasible during the latency period without wheel slip or including an acceptable amount of wheel slip. 
     That is, in examples, determining a maximum allowable increase in speed of the traction motor  14  to occur during the latency period comprises determining an allowable increase in speed of the traction motor  14  during the latency period without causing unwanted wheel slip. 
     The maximum allowable increase in speed of the traction motor  14  to occur during the latency period associated with the prevailing speed value of the traction motor  14  can be determined in dependence on any suitable factor or factors. 
     For example, mass of vehicle, mass and rotational inertia of traction motor, vehicle speed, capability of traction motor, gradient, vehicle road load such as aero losses and/or rolling losses, gear, tyres and/or tyre size and so on can be considered. 
     In some examples, one or more of the factors can be considered consistent and variables such as vehicle speed and gradient could be taken into account as well as a driver demand influence on the maximum expected acceleration. In some examples, only a single factor such as vehicle speed, or equivalent traction motor speed, can be taken into account. 
     In some examples, the maximum allowable increase in speed of the traction motor  14  can be determined in dependence on the prevailing speed of the vehicle  10 . 
     Accordingly, in examples, determining a maximum allowable increase in speed of the traction motor  14  comprises determining a prevailing speed of the vehicle  10  and determining the maximum allowable increase in speed of the traction motor in dependence on the prevailing speed of the vehicle  10 . 
     Any suitable method for determining a prevailing speed of the vehicle  10  can be used. In some examples vehicle speed is derived as the average of the wheel speed sensors. Fault handling can be used to allow, for example, use of replacement values if use of the average of the wheel speed sensors is no longer appropriate. 
     In some examples, the prevailing speed of the vehicle  10  is determined by taking an average value from the wheel speed sensors associated with each road wheel of the vehicle  10 . The average wheel speed may be compared with the highest and/or lowest wheel speed value from the sensors, to determine whether a wheel slip event is taking place. A further comparison may be made between signals received from wheel speed sensors and signals received from a vehicle mounted inertial measurement unit (IMU). The IMU may comprise an array of accelerometers arranged to determine the acceleration of the vehicle body in the longitudinal, vertical and lateral directions. If a sudden change in wheel speed is detected but there is no corresponding change in vehicle body acceleration, then that may be indicative of a wheel slipping. 
     In examples, a latency period can also exist with regard to the vehicle speed. However, in practice vehicle speed does not change quickly enough for the associated latency period to cause a significant error in the determination of the maximum allowable increase in speed of the traction motor  14 . 
     In examples, any suitable method for determining the maximum allowable increase in speed of the traction motor  14  in dependence on the prevailing speed of the vehicle  10  can be used. 
     For example, the prevailing speed of the vehicle  10  can be used as an input into one or more functions which provide, as an output, the maximum allowable increase in speed of the traction motor  14 . 
     In examples, the function can comprise any number of further inputs and/or outputs. In examples, any suitable inputs can be used in determining the maximum allowable increase in speed of the traction motor  14 . 
     In some examples, determining a maximum allowable increase in speed of the traction motor  14  comprises accessing at least one data structure in dependence on the prevailing speed of the vehicle  10 . 
     In such examples, the at least one data structure can comprise any suitable form or forms and can be used in any suitable way. 
     In some examples, the at least one data structure can take the form of and/or represent a lookup table that can be accessed in dependence on the prevailing speed of the vehicle  10 . 
     Accordingly, in examples, determining a maximum allowable increase in speed of the traction motor  14  comprises accessing a lookup table using the prevailing speed of the vehicle  10 . 
     In some examples, the maximum allowable increase in speed of the traction motor  14  can be determined in terms of a maximum change in revolutions per minute of the traction motor during the latency period associated with the prevailing speed value of the traction motor  14 . 
     In examples, the at least one function, at least one data structure, such as at least one lookup table, can be determined using any suitable method. For example, the formula and/or data structure can be determined experimentally and/or using one or more models and so on. 
     In examples, the latency period of the prevailing speed value of the traction motor  14  is approximately 50 to 100 milliseconds. 
     However, in examples any suitable latency period can be accommodated in dependence on, for example, information flow to/from the control system  12 . 
     At block  408 , the method  400  comprises determining an electrical power consumption limit  606  in dependence on the torque request  616 , the prevailing speed value of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14 . 
     Any suitable method for determining an electrical power consumption limit  606  in dependence on the torque request  616 , the prevailing speed value of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14  can be used. 
     In examples, determining an electrical power consumption limit  606  comprises determining the maximum predicted speed of the traction motor  14  in the latency period by adding the maximum allowable increase in speed of the traction motor  14  to the prevailing speed value of the traction motor  14  and estimating the predicted electrical power consumption of the traction motor  14  at that maximum allowable speed. 
     In examples, determining an electrical power consumption limit  606  comprises using one or more functions in dependence on the torque request, prevailing speed value of the traction motor  14  and determined maximum allowable increase in speed of the traction motor  14 . 
     For example, the torque request  616 , the prevailing speed value of the traction motor  14  and the determined maximum allowable increase in speed of the traction motor during the latency period can be used as inputs into one or more functions which provide as an output an electrical power consumption limit  606 . 
     In examples, the function can comprise any number of further inputs and/or outputs. In examples, any suitable inputs can be used in determining an electrical power consumption limit  606 . 
     In examples, determining an electrical power consumption limit  606  comprises accessing at least one data structure in dependence on the torque request, prevailing speed value of the traction motor and the maximum allowable increase in speed of the traction motor  14 . 
     In examples, determining an electrical power consumption limit  606  comprises accessing at least one data structure in dependence on the torque request  616  and the maximum predicted speed of the traction motor  14  during the latency period, the maximum predicted speed determined from the prevailing speed value of the traction motor  14  and the determined maximum allowable increase in speed of the traction motor  14  during the latency period. 
     In such examples, the at least one data structure can comprise any suitable form or forms and can be used in any suitable way. 
     The at least one data structure can represent and/or take the form of a lookup table that can be accessed in dependence of the torque request  616 , prevailing speed value of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14 . 
     Accordingly, in examples, determining an electrical power consumption limit  606  comprises accessing a lookup table using the torque request  616 , prevailing speed of the traction motor  14  and the maximum allowable increase in speed of the traction motor  14 . 
     In examples, the at least function and/or at least one data structure for determining an electrical power consumption limit  606  accounts for efficiencies in provision of torque by the traction motor  14 . 
     That is, in examples, determining an electrical power consumption limit  606  comprises accounting for efficiencies in provision of torque by the traction motor  14 . 
     The electrical power consumption limit  606  can be determined in any suitable form. 
     In examples, the electrical power consumption limit  606  comprises a limit in terms of electrical current and/or power to be supplied to the traction motor 
     In examples, the electrical power consumption limit  606  comprises a limit in terms of electrical current and/or power to be drawn from the energy storage means  16  by the traction motor  14 . 
     In examples, the at least one function, at least one data structure, such as at least one lookup table, can be determined using any suitable method. For example, the formula and/or data structure can be determined experimentally and/or using one or more models and so on. 
     In some examples it is ensured that the electrical power consumption limit  606  takes into account ancillaries and/or other traction motor usage. 
     At block  410 , the method  400  comprises controlling torque provision of the traction motor  14  in dependence on the torque request  616  and the electrical power consumption limit  606 . 
     Any suitable method for controlling torque provision of the traction motor  14  in dependence on the torque request  616  and the electrical power consumption limit  606  can be used. 
     In examples, the traction motor  14  is controlled to provide the requested torque limited by the electrical power consumption limit  606 . 
     For example, the traction motor  14  can be controlled to provide the requested torque until the electrical power consumption limit  606  is reached after which the torque provided by the traction motor  14  is limited to prevent the electrical power consumption limit  606  being exceeded, such as during a wheel slip event. 
     In examples, controlling torque provision of the traction motor  14  comprises providing one or more signals comprising information to the traction motor  14  to control the traction motor  14 . 
     In examples, controlling torque provision comprises transmitting the torque request  616  and electrical power consumption limit  606  to control torque provision. 
     For example, a first controller or controllers  18   a  can perform blocks  402  to  408  of method  400  and can transmit the torque request  616  and electrical power consumption limit  606  to a further controller or controllers  18   b  configured to control the traction motor  14 . See, for example,  FIG.  5   . 
     In examples, controlling torque provision comprises determining a speed value of the traction motor  14  having a lower associated latency and determining a torque limit in dependence on the lower latency speed value of the traction motor, the torque request  616  and the electrical power consumption limit  606 . 
     For example, when the torque request  616  and electrical power consumption limit  606  are transmitted from a first controller or controllers  18   a  to a different controller or controllers  18   b  to control the traction motor  14  the further or different controller or controllers  18   b  may have access to a speed value of the traction motor  14  having a lower associated latency. 
     For example, the different or second controller or controllers  18   b  may be closer to the traction motor  14  and therefore the speed of the traction motor  14  may be determined at the different or second controller or controllers  18  with less lag or a lower latency period. 
     In such examples, the different or second controller or controllers  18   b  can determine a speed value of the traction motor  14  having a lower associated latency and determine a torque limit, for torque to be provided by the traction motor  14 , in dependence on the lower latency speed value of the traction motor  14 , the torque request  616  and the electrical power consumption limit  606 . 
     In examples, determining a torque limit comprises using a model of the electrical power to torque conversion of the traction motor  14  to calculate the torque limit using the value of speed of the traction motor having the lower associated latency. 
     Any suitable model can be used. In some examples, the torque limit can be applied directly in current and in such examples no conversion of the limit is performed. 
     The control system  12  can limit the requested torque using the determined torque limit if the electrical power consumption limit  606  will be exceeded, such as during a wheel slip event. 
     A technical effect of the method  400  is that a limit can be placed on electrical power consumption preventing traction battery damage and/or use of intrusive battery protection features when a wheel slip event occurs. 
     Additionally, or alternatively, in some examples, closed loop control is provided within a single controller which obviates issues with network latency. 
       FIG.  5    illustrates an example of a control system. The control system  12  of  FIG.  5    can be as described in relation to  FIG.  2 A  and/or  FIG.  3   . 
     In examples, the control system  12  of  FIG.  5    is configured to perform the method of  FIG.  4    and/or as described herein. 
     In the example of  FIG.  5   , the control system  12  comprises two controllers  18   a ,  18   b . However, in some examples the control system can comprise any suitable number of controllers  18 . 
     In the example of  FIG.  5   , the first and second controllers  18   a ,  18   b  are configured to perform different parts of the method  400 . Accordingly, it can be considered, in examples, that in the example of  FIG.  5    the first and second controllers  18   a ,  18   b  are responsible for different parts of the method  400 . 
     In the example of  FIG.  5   , information can flow to and from the first and second controllers  18   a  and  18   b  and between the first and second controllers  18   a  and  18   b  as illustrated by the double headed arrows in  FIG.  5   . 
     In the example of  FIG.  5   , the first controller  18   a  is configured to perform, at least, blocks  402  to  408  of the method  400  of  FIG.  4   . 
     However, in the example of  FIG.  5   , controller  18   b  is configured to perform, at least, block  410  and is therefore configured to control provision of torque by the traction motor or motors  14 . In some examples, the controller(s)  18   b  can be an inverter. 
     Accordingly, the first controller  18   a  has a prevailing speed value of the traction motor  14  having a larger associated latency period than the second controller  18   b  which is closer to the traction motor  14 . 
     Therefore, in the example of  FIG.  5   , the controller  18   a , configured to perform blocks  402  to  408  of  FIG.  4    and provide the control information to controller  18   b  to control torque provision from the traction motor  14  can do so while implementing closed loop control at the controller  18   b  despite the latency period associated with the speed value of the traction motor  14  accessible at the controller  18   a.    
     It can be seen, therefore, in the example of  FIG.  5    that by using the inventive method  400  described herein power spikes from a traction battery can be avoided during a wheel slip event. 
     This is because an electrical power consumption limit  606  is used to limit the torque provided to prevent excessive power being drawn from a traction battery due to a wheel accelerating quickly during a latency period of the speed value of the traction motor  14  known by controller  18   a.    
       FIG.  6    illustrates an example of controlling electrical power consumption from energy storage means  16  by a traction motor  14  of a vehicle  10  caused by a wheel slip event. 
     In examples, the vehicle  10  is the vehicle illustrated in  FIG.  1    or  FIG.  3   . 
     The example of  FIG.  6    is split into three sections, an upper section A, a middle section B. and a lower section C. The upper section of  FIG.  6    can therefore be considered  FIG.  6 A , the middle section of  FIG.  6    can be considered  FIG.  6 B  and the lower section of  FIG.  6    can be considered  FIG.  6 C . 
       FIG.  6 A  illustrates traction motor current as a function of time. 
       FIG.  6 B  illustrates traction motor speed as a function of time. 
       FIG.  6 C  illustrates traction motor torque as a function of time. 
     Also illustrated in  FIG.  6    are four times t 1 , t 2 , t 3  and t 4  which are common to  FIGS.  6 A,  6 B and  6 C . 
     In  FIG.  6 C , a torque request for the traction motor  14  is illustrated by dashed line  616 . It can be seen In  FIG.  6 C  that the torque request is constant up until time t 2 . 
     In  FIG.  6 A  the traction motor current without use of the inventive method described herein is illustrated by the solid line  602 . 
     Before time t 1  the current  602  drawn by the traction motor  14  increases in line with the increasing speed of the traction motor  14  due to the torque request  616 . 
     However, at time t 1  there is a wheel slip event and the speed of the traction motor  14  increases rapidly as illustrated by the solid line  610  in  FIG.  6 B . 
     It can be seen that between times t 1  and t 2  the current  602  drawn by the traction motor  14  increases rapidly and passes above the battery discharge current limit illustrated by the solid horizontal line labelled  604 . 
     Accordingly, without the inventive method described herein, repeated exposure to events such as these may lead to battery damage. 
     In the example of  FIG.  6   , at time t 2 , implausible wheel acceleration is determined and therefore the torque request  616  is limited. This can be seen in  FIG.  6 C  by the torque request  616  reducing between times t 2  and t 3 . 
     Accordingly, the current  602  drawn by the traction motor  14  also reduces between times t 2  and t 3  passing below the battery discharge current limit  604  around time t 3 . 
     The corresponding speed  610  of the traction motor  14  also reduces during times t 2  and t 3 . 
     At time t 3  the wheel slipping event is detected by a system of the vehicle  10 , such as a stop control system, and further torque intervention  614  is then applied. 
     This can be seen in  FIG.  6 C  as between times t 3  and t 4  the torque request  616  is further limited and, in  FIG.  6 A  the current  602  by the traction motor  14  also further reduces. 
     Similarly, in  FIG.  6 B , the corresponding speed  610  of the traction motor  14  also continues to reduce between times t 3  and t 4 . 
     The torque provided by the traction motor  14  in this example is illustrated in  FIG.  6 C  by the solid line labelled  618 . The torque provided  618  without the method described herein follows the torque request  616 . 
     It can be therefore seen in the example of  FIG.  6    that a wheel slip event can, without the inventive method described herein, can lead to unnecessarily large power drawn from a traction battery, for example. 
     Also illustrated in the example of  FIG.  6    is an example of applying the inventive electrical power consumption control described herein. 
     In this example, the torque request  616  in  FIG.  6 C  remains the same. The current drawn in this case is illustrated by the dot-dashed line  608  and it can be seen that prior to time t 1  the current  608  matches the current  602  drawn without using the method described herein. However, in the example of  FIG.  6 A  the lines  602  and  608  have been offset slightly for the purpose of illustration. 
     At time t 1  the current  608  drawn while using the method described herein also increases after the wheel slip event but is limited by the electrical consumption power limit  606  shown as a dashed line in  FIG.  6 A . 
     It can therefore be seen that the electrical current drawn  608  rises sharply but then is prevented from exceeding the electrical consumption power limit  606 . This also, therefore, prevents the battery discharge current limit  604  from being exceeded. 
     The corresponding traction motor speed is illustrated in  FIG.  6 B  by the dot-dashed line  612 . It can be seen that the speed  612  of the traction motor  14  does not increase as much as the speed  610  without the method described herein. 
     The current  608  drawn by the traction motor  14  continues to follow the electrical consumption power limit  606  until time t 3  in which intervention  614  further limits the torque provided. 
     The associated torque provided by the traction motor  14  is shown by the dot-dashed line  620  in  FIG.  6 C . 
     It can be seen in  FIG.  6 C  that, for the example using the method described herein, the torque provided by the traction motor  14 , compared to the torque requested, is limited between times t 1  and t 3  compared to the case (line  618  in  FIG.  6 C ) where the inventive method described herein is not used. This is illustrated by the hashed area in  FIG.  6 C . 
     As used herein “for” should be considered to also include “configured or arranged to”. For example, “a control system for” should be considered to also include “a control system configured or arranged to”. 
     For purposes of this disclosure, it is to be understood that the controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on one or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions. 
     It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. 
     The blocks illustrated in the  FIG.  4    may represent steps in a method and/or sections of code in the computer program  31 . The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.