Patent Description:
A conventional powertrain for a vehicle delivers a given amount of resistive torque due to the internal losses of an internal combustion engine (ICE) when the accelerator pedal is released. The level of restive torque or "overrun" provided by the ICE by can be increased by downshifting gears, which increases the frictional and pumping losses of the ICE. With electrification of the powertrain, it is now possible to offer a customisable level of resistive torque when the accelerator pedal is released by emulating the internal losses of an ICE to single-pedal driving. However, known emulations of these losses fail to reproduce accurately the experience that drivers expect from driving a vehicle comprising an ICE.

The present invention has been devised to mitigate or overcome the above-mentioned problem.

In <CIT>, a motor controller for a motor vehicle employing a motor as a drive source can exhibit regenerative brake power corresponding to that of an engine brake for a vehicle employing an internal-combustion engine as a drive source and the regenerative brake power can be controlled smoothly over a wide range.

Aspects and features of the present invention are defined in the claims.

According to an aspect of the present invention there is provided a controller for a vehicle, the controller being configured to:.

Optionally, the road load signal is a function of at least one of:.

Optionally, the maximum torque signal is a function of at least one of:.

Optionally, the overrun torque demand signal is a function of at least one of:.

In an embodiment, the acceleration pedal map comprises a low-speed acceleration pedal map and a high-speed acceleration pedal map.

In an embodiment, the deceleration pedal map comprises a low-speed deceleration pedal map and a high-speed deceleration pedal map.

The controller may be configured to determine a torque output in dependence on the low-speed acceleration pedal map and the high-speed acceleration pedal map if the position of the accelerator pedal is greater than the reference accelerator pedal position and the vehicle speed is between the low-speed limit and the high-speed limit.

The controller may be configured to determine a torque output in dependence on the low-speed deceleration pedal map and the high-speed deceleration pedal map if the position of the accelerator pedal is less than the reference accelerator pedal position and the vehicle speed is between the low-speed limit and the high-speed limit.

The controller may be configured to determine the torque output in dependence on the vehicle speed.

According to a further embodiment of the present invention there is provided a control system according to claim <NUM>.

According to a further embodiment of the present invention there is provided a vehicle according to claim <NUM>.

According to a further embodiment of the present invention, the controller may be configured to selectively inhibit or modify the application of acceleration or deceleration pedal maps in dependence on the surface over which the vehicle is travelling.

The controller may be configured to selectively inhibit or modify the application of acceleration or deceleration pedal maps in dependence on a received or determined terrain mode, or a terrain type received from a further vehicle system or controller.

According to a further embodiment of the invention is provided a method according to claim <NUM>.

With reference to <FIG>, a powertrain, designated generally as <NUM>, of an electric vehicle <NUM> is shown in plan view. The powertrain <NUM> comprises an energy storage means, in the form of a battery <NUM>, operatively connected via an inverter <NUM> to an electric motor <NUM>, which generates torque, and a drive transmission <NUM>. The drive transmission <NUM> could take the form of a differential (no disconnection mechanism or gears). The torque is transferred through a driveline <NUM> to wheels <NUM> that generate a tractive force to move the vehicle <NUM>. A controller <NUM> is operatively connected to the electric motor <NUM> by the inverter <NUM>, and functions to control the generation of torque by converting an accelerator pedal position to a torque output using an accelerator pedal map. Although <FIG> only shows one motor <NUM> driving the wheels of a rear axle, it will apparent that the vehicle <NUM> may be arranged so that it has one motor driving the wheels of a front axle, or may have at least one additional motor to drive the wheels of both the front a and rear axles, or additional motors to drive individual wheels.

<FIG> shows a graph <NUM>, in the form of an accelerator pedal map, relating the torque requested from the electric motor <NUM> to the travel of the accelerator pedal. The skilled reader will understand that this is a simplified section through a map that may also incorporates vehicle speed or actuator speed. A full map would consist of a torque surface in the Z (vertical) axis based on the accelerator pedal position in one axis and the motor speed or vehicle speed in another axis. The required torque is the output. Line <NUM> shows the road load plotted against the position of the accelerator pedal. For clarity, the term "road load" refers to the torque that opposes the movement of the vehicle <NUM> or, in other words, the torque necessary for maintaining the speed of the vehicle <NUM>. Line <NUM> shows that the torque increases with respect to the accelerator pedal position to a maximum torque output relating to the maximum torque deliverable by the powertrain <NUM> when the accelerator pedal is fully pressed (<NUM>% accelerator pedal position). Conversely, the torque output decreases with respect to pedal position to a minimum when the accelerator pedal is fully released (<NUM>% accelerator pedal position), which relates to the maximum resistive torque or overrun torque requested from the electric motor <NUM> by a powertrain control unit <NUM>. The relationship between the road load and the accelerator pedal position can be characterised generally as being constantly proportional. However, such a relationship cannot deliver a driving experience comparable to what the driver would expect from driving a vehicle comprising an ICE. To this end, the controller <NUM> functions to provide an intuitive driving experience.

With reference to <FIG>, in accordance with embodiments of the invention, the controller <NUM> is operable to receive input data regarding the operation of the vehicle <NUM> and to issue a torque request to the powertrain control unit <NUM> to achieve a control objective, such as an acceleration demand from the driver of the vehicle <NUM>. The input data comprises a plurality of electrical signals relating to: the accelerator pedal position <NUM>; the vehicle speed <NUM>; the vehicle longitudinal inclination <NUM>; a terrain response mode <NUM>; the current torque <NUM> being delivered by the electric motor <NUM>; the road load <NUM>; optionally, the road load accelerator pedal position <NUM>; the maximum torque <NUM> deliverable by the powertrain <NUM>; the overrun torque <NUM> requested by the powertrain control unit <NUM>; and, the state of charge <NUM> of the battery <NUM>. In this instance, the vehicle longitudinal inclination <NUM> relates to the gradient of the surface the vehicle <NUM> is traversing. These electrical signals, together with the controller <NUM> and the powertrain control unit <NUM> form part of a control system <NUM>. The controller <NUM> comprises a processor <NUM> configured to convert an accelerator pedal position to a torque output based on one or more accelerator pedal maps, which can be stored in and read from a memory module <NUM>. Alternatively, the controller may be configured to determine the one or more accelerator pedal maps. The skilled reader will appreciate that <FIG> is provided only to illustrate an example of a controller <NUM> architecture in which the invention may be implemented.

With reference to <FIG>, in accordance with an embodiment of the invention, the controller <NUM> incorporates software to implement the process <NUM> shown in the block diagram. The process <NUM> initiates at step <NUM>, which may be when the vehicle <NUM> is operating under road load conditions. At step <NUM>, the current position of the accelerator pedal is determined. The position of the accelerator pedal is then compared, at step <NUM>, against a reference accelerator pedal position to determine if it is greater than the reference accelerator pedal position. The reference accelerator pedal position relates to the road load accelerator pedal position <NUM>. If it is determined that the accelerator pedal position is greater than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where a torque output is determined using an acceleration pedal <NUM> map before the process <NUM> terminates at step <NUM>. However, if at step <NUM> it is determined that the accelerator pedal position is not greater than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where it is determined if the accelerator pedal position equals or is less than the reference accelerator pedal position. If the accelerator pedal position equals the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where the current torque output is maintained before the process <NUM> terminates at step <NUM>. However, if it is determined, at step <NUM>, that the accelerator pedal position is less than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where a torque output is determined using a deceleration pedal map <NUM> before the process <NUM> terminates at step <NUM>. It is envisaged that the process <NUM> could repeat continually (e.g. at every execution cycle of a given software task).

<FIG> shows a graph <NUM>, in the form of an accelerator pedal map, illustrating the operation carried out by the process <NUM>. The relationship between the road load and the accelerator pedal position is shown by line <NUM>. The controller <NUM> is configured to receive a road load signal <NUM>, indicative of the road load (toRL), and determine a road load accelerator pedal position signal <NUM>. The road load accelerator pedal position signal <NUM> is indicative of the reference accelerator pedal position (aref). In this example, the reference accelerator pedal position is the road load accelerator pedal position (aref), but for some implementations or circumstances, it may be desirable to determine the reference accelerator pedal position on the basis of other factors in addition to the road load accelerator pedal position. The controller <NUM> is further configured to receive an accelerator pedal position signal <NUM>, which indicates the current accelerator pedal position, and compare the reference accelerator pedal position signal <NUM> and the accelerator pedal position signal <NUM> to determine the position of the accelerator pedal with respect to the reference accelerator pedal position (aref). If the accelerator pedal position is greater than the reference accelerator pedal position (aref), the controller <NUM> determines that an acceleration demand has been requested by the driver of the vehicle <NUM>. In this case, a torque output is determined using an acceleration pedal map <NUM>. On the other hand, if the accelerator pedal position is less than the reference accelerator pedal position (aref), the controller <NUM> decides that a deceleration demand has been requested and determines a torque output using a deceleration pedal map <NUM>. The lower and upper limits of the acceleration pedal map <NUM> are set by the road load (toRL) and the maximum torque deliverable by the powertrain <NUM>, respectively. Whereas, the lower and upper limits of the deceleration pedal map <NUM> are set by the maximum resistive torque and the road load (toRL), respectively. The acceleration and deceleration pedal maps <NUM>, <NUM> are customisable to provide an intuitive driving experience more akin to driving a vehicle comprising an ICE. For example, the acceleration and deceleration pedal maps <NUM>, <NUM> could be customised according to the speed of the vehicle <NUM>.

In an embodiment of the invention, the acceleration pedal map <NUM> comprises a low-speed acceleration pedal map and a high-speed acceleration pedal map. Similarly, the deceleration pedal map <NUM> comprises a low-speed deceleration pedal map and a high-speed deceleration pedal map. The controller <NUM> is configured to receive a vehicle speed signal <NUM>, indicative of the speed of the vehicle <NUM>, and determine a torque output in dependence on the vehicle speed signal <NUM>. If the accelerator pedal position is greater than the reference accelerator pedal position (aref) and it is determined that the speed of the vehicle <NUM> is below a predetermined threshold speed the controller <NUM> determines a torque output using the low-speed acceleration pedal map. However, if the accelerator pedal position is greater than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> is greater than the predetermined threshold speed, the controller <NUM> determines a torque output using the high-speed acceleration pedal map. Similarly, if the accelerator pedal position is less than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> is below the predetermined threshold speed, the controller <NUM> determines a torque output using the low-speed deceleration pedal map. Moreover, if the accelerator pedal position is less than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> is greater than the predetermined threshold speed, the controller <NUM> determines a torque output using the high-speed deceleration pedal map.

Alternatively, selection of the low-speed and high-speed acceleration and deceleration pedal maps may be dependent on the vehicle speed relative to different speed limits. If the accelerator pedal position is greater than the reference accelerator pedal position (aref) and it is determined that the speed of the vehicle <NUM> equals or is below a predetermined low-speed limit, the controller <NUM> determines a torque output using the low-speed acceleration pedal map. However, if the accelerator pedal position is greater than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> equals or is greater than a predetermined high-speed limit, the controller <NUM> determines a torque output using the high-speed acceleration pedal map. Similarly, if the accelerator pedal position is less than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> equals or is below a predetermined low-speed limit, the controller <NUM> determines a torque output using the low-speed deceleration pedal map. Moreover, if the accelerator pedal position is less than the reference accelerator pedal position (aref) and the speed of the vehicle <NUM> equals or is greater than a predetermined high-speed limit, the controller <NUM> determines a torque output using the high-speed deceleration pedal map. The controller <NUM> is further configured to determine a torque output based a combination of the low-speed and high-speed acceleration pedal maps if the accelerator pedal position is greater than the reference accelerator pedal position (aref), but the speed of the vehicle <NUM> is between the low-speed and high-speed limits. Likewise, a torque output is determined based a combination of the low-speed and high-speed deceleration pedal maps when the accelerator pedal position is less than the reference accelerator pedal position (aref), but the speed of the vehicle <NUM> is between the low-speed and high-speed limits. Combining pedal maps may be done by interpolating between the low-speed and high-speed pedal maps in dependence on the vehicle speed.

In a further embodiment of the invention, the controller <NUM> may also be configured to modify the acceleration and deceleration pedal maps, or the low-speed and high-speed versions thereof, using a gradient modifier to take into account a gradient of the surface the vehicle <NUM> is traversing. The controller <NUM> determines the gradient modifier in dependence on the vehicle longitudinal inclination or gradient signal <NUM>.

With reference to <FIG>, in accordance with an implementation, the controller <NUM> incorporates software to implement the process <NUM> shown in the block diagram. The process <NUM> initiates at step <NUM> and progresses to step <NUM>, where it is determined whether the vehicle <NUM> is traversing a gradient. This can be done using the vehicle longitudinal inclination or gradient signal <NUM>. If it is determined that the vehicle <NUM> is traversing a gradient, the process <NUM> moves to step <NUM> where it is determined whether the gradient is a positive gradient or a negative gradient. If, at step <NUM>, it is determined that the vehicle <NUM> is traversing a positive gradient, the process <NUM> moves to step <NUM> and a torque output is determined using a positive gradient pedal map. However, if, at step <NUM>, it is determined that the vehicle <NUM> is traversing a negative gradient, the process <NUM> moves to step <NUM> and a torque output is determined using a negative gradient pedal map. Following steps <NUM>, <NUM>, the process <NUM> terminates at step <NUM>. Basing the torque output on accelerator pedal maps that have been modified to account for the gradient of the surface the vehicle <NUM> is traversing prevents the perceived performance reduction that occurs in electric vehicles, which do not have a traditional gearbox, and offers the opportunity to enhance an electrified powertrain capability feel over a conventional one.

<FIG> shows a graph <NUM> illustrating the operation carried out by the process <NUM>. The graph <NUM> comprises three accelerator pedal maps. Line <NUM> shows an accelerator pedal map under road load conditions, and lines <NUM>, <NUM> are the positive gradient and the negative gradient accelerator pedal maps respectively. That is, lines <NUM>, <NUM> are accelerator pedal maps that have been altered to account for a positive gradient and a negative gradient respectively. The degree to which lines <NUM>, <NUM> are altered may also be influenced by the terrain response mode selected by the driver of the vehicle <NUM>, in addition to gradient. The controller <NUM> is configured to determine the selected terrain response mode using the terrain response mode signal <NUM>. It can be seen from line <NUM> that the torque output is greater, for the same accelerator pedal position, when compared to road load conditions. Conversely, line <NUM> shows that the torque output is less when compared to road load conditions for the same accelerator pedal position.

The graph <NUM> comprises two additional accelerator pedal maps, lines <NUM>, <NUM>. These lines <NUM>, <NUM> represent the torque output necessary for maintaining the speed of the vehicle <NUM> when going from road load conditions to traversing a positive gradient or a negative gradient respectively. Lines <NUM>, <NUM> have been altered to account for the same gradients as lines <NUM>, <NUM>. When the vehicle <NUM> is traversing a positive gradient, the controller <NUM> functions to determine torque output using the positive gradient accelerator pedal map, line <NUM>. It can be seen from comparing lines <NUM>, <NUM> that, for the same accelerator pedal position (a<NUM>), the torque output (to<NUM>) from the positive gradient accelerator pedal map, line <NUM>, is less than the torque (to<NUM>) necessary for maintaining the speed of the vehicle <NUM> while traversing the positive gradient. That is, the positive gradient accelerator pedal map, line <NUM>, used by the controller <NUM> purposively under compensates for the positive gradient. In order to maintain the speed of the vehicle <NUM>, the driver of the vehicle <NUM> is required to press the accelerator pedal to position (a<NUM>) to achieve the required torque output (to<NUM>). This situation is constructed by the controller <NUM> in order to provide an intuitive driving experience in which the driver would expect to have to press the accelerator pedal to some extent when traversing a positive gradient based on their experience of driving a vehicle comprising an ICE.

Similarly, the driver would expect to have to lift-off or release the accelerator pedal when going downhill. In view of that, the negative gradient accelerator pedal map, line <NUM>, used by the controller <NUM> purposively over compensates for the negative gradient, and so the driver of the vehicle <NUM> is required to release the accelerator pedal in order to maintain the speed of the vehicle <NUM> when traversing a negative gradient.

It can be seen that the upper limit of the positive gradient accelerator pedal map, line <NUM>, is offset from the road load accelerator pedal map, line <NUM>, such that it exceeds the maximum torque deliverable by the powertrain <NUM>. This is done in order to prevent the effect of the gradient modification from dissipating, as indicated by line <NUM>, as the torque demand increases away from the road load and towards the maximum torque deliverable by the powertrain <NUM>, which would be counter-intuitive for the driver of the vehicle <NUM>.

In a further embodiment of the invention, the controller <NUM> may determine an accelerator pedal map on receiving the state of charge signal <NUM>, which indicates that the state of charge of the battery <NUM> is below a predetermined threshold, and determine a torque output in dependence on the accelerator pedal map.

<FIG> shows a graph <NUM> including an accelerator pedal map <NUM> in accordance with this implementation. The graph <NUM> includes an additional accelerator pedal map <NUM>. The additional accelerator pedal map <NUM> is an example of how known accelerator pedal maps are modified when the state of charge of an energy storage means on an electric vehicle falls below a threshold. In this example, it can be seen that the accelerator pedal map <NUM> initially increases with the accelerator pedal position, after which a torque limit is applied and the torque output remains constant as the accelerator pedal position increases. However, rather than applying a torque limit, the accelerator pedal map <NUM> is configured to deliver increasing amounts of torque with respect to pedal position up to a maximum which is less that the maximum torque deliverable by the powertrain <NUM>. Although this results in an overall lower output torque, the behaviour of the vehicle <NUM> is made to be more intuitive for the driver when compared to simply applying a torque limit. In embodiments of the invention, the accelerator pedal map <NUM> is configured to maximise the range of the vehicle <NUM>, increasing the likelihood of the vehicle <NUM> reaching its destination. Moreover, the accelerator pedal map <NUM> could be configured so that the torque delivered over the first part of the accelerator pedal range is delivered at a higher rate when compared to the torque delivered over the second part of the accelerator pedal range. This means that the driver is able to accelerate in city traffic conditions and maintain a high cruising speed, but the vehicle <NUM> will have a lower acceleration in the second part of the accelerator pedal range.

The controller may be configured to selectively inhibit or modify the application of acceleration or deceleration pedal maps in dependence on the surface over which the vehicle is travelling.

Any controller or controllers described herein may suitably comprise a control unit or computational device having one or more electronic processors. Thus the system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term "controller" or "control unit" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said computational device. A first controller may be implemented in software run on one or more processors. One or more other controllers may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used.

With reference to <FIG>, in accordance with embodiments of the invention, the controller <NUM> is operable to receive input data regarding the operation of the vehicle <NUM> and to issue a torque request to the powertrain control unit <NUM> to achieve a control objective, such as an acceleration demand from the driver of the vehicle <NUM>. The input data comprises a plurality of electrical signals relating to: the accelerator pedal position <NUM>; the vehicle speed <NUM>; the vehicle longitudinal inclination <NUM>; a terrain response mode <NUM>; the current torque <NUM> being delivered by the electric motor <NUM>; the road load <NUM>; optionally, the road load accelerator pedal position <NUM>; the maximum torque <NUM> deliverable by the powertrain <NUM>; the overrun torque <NUM> requested by the powertrain control unit <NUM>; and, the state of charge121 of the battery <NUM>. In this instance, the vehicle longitudinal inclination <NUM> relates to the gradient of the surface the vehicle <NUM> is traversing. These electrical signals, together with the controller <NUM> and the powertrain control unit <NUM> form part of a control system <NUM>. The controller <NUM> comprises a processor <NUM> configured to convert an accelerator pedal position to a torque output based on one or more accelerator pedal maps, which can be stored in and read from a memory module <NUM>. Alternatively, the controller may be configured to determine the one or more accelerator pedal maps. The skilled reader will appreciate that Figure <NUM> is provided only to illustrate an example of a controller <NUM> architecture in which the invention may be implemented.

<FIG> shows a graph <NUM>, in the form of an accelerator pedal map, illustrating the operation carried out by the process <NUM>. The relationship between the road load and the accelerator pedal position is shown by line <NUM>. The controller <NUM> is configured to receive a road load signal <NUM>, indicative of the road load (toRL), and determine a road load accelerator pedal position signal <NUM>. The road load accelerator pedal position signal <NUM> is indicative of the reference accelerator pedal position (aref). In this example, the reference accelerator pedal position is the road load accelerator pedal position (aref), but for some implementations or circumstances, it may be desirable to determine the reference accelerator pedal position on the basis of other factors in addition to the road load accelerator pedal position. The controller <NUM> is further configured to receive an accelerator pedal position signal <NUM>, which indicates the current accelerator pedal position, and compare the reference accelerator pedal position signal <NUM> and the accelerator pedal position signal <NUM> to determine the position of the accelerator pedal with respect to the reference accelerator pedal position (aref). If the accelerator pedal position is greater than the reference accelerator pedal position (aref), the controller <NUM> determines that an acceleration demand has been requested by the driver of the vehicle <NUM>. In this case, a torque output is determined using an acceleration pedal map <NUM>. On the other hand, if the accelerator pedal position is less than the reference accelerator pedal position (aref), the controller <NUM> decides that a deceleration demand has been requested and determines a torque output using a deceleration pedal map <NUM>. The lower and upper limits of the acceleration pedal map <NUM> are set by the road load (toRL) and the maximum torque deliverable by the powertrain <NUM>, respectively. Whereas, the lower and upper limits of the deceleration pedal map <NUM> are set by the maximum resistive torque and the road load (toRL), respectively. The acceleration and deceleration pedal maps <NUM>,<NUM> are customisable to provide an intuitive driving experience more akin to driving a vehicle comprising an ICE. For example, the acceleration and deceleration pedal maps <NUM>, <NUM> could be customised according to the speed of the vehicle <NUM>.

In some circumstances, particularly in off-highway or off-road terrain, it may be undesirable to modify the pedal response in this way, for example when traversing some terrain types where consistent control of the vehicle torque irrespective of the gradient is desirable. The controller may be configured to inhibit the positive gradient pedal map and / or the negative gradient pedal map in dependence on a terrain mode of the vehicle. The terrain mode may be selected by a driver of the vehicle, or determined automatically by a control system of the vehicle. For example, the controller may be configured to inhibit the positive gradient pedal map and / or the negative gradient pedal map the terrain mode of the vehicle is a sand mode or a rock mode.

In a further implementation, the controller <NUM> may determine an accelerator pedal map on receiving the state of charge signal <NUM>, which indicates that the state of charge of the battery <NUM> is below a predetermined threshold, and determine a torque output in dependence on the accelerator pedal map.

With reference to <FIG>, a powertrain, designated generally as <NUM>, of an electric vehicle <NUM> is shown in plan view. The powertrain <NUM> comprises an energy storage means, in the form of a battery <NUM>, operatively connected via an inverter <NUM> to an electric motor <NUM>, which generates torque, and a drive transmission <NUM>. The drive transmission <NUM> could take the form of a differential. The torque is transferred through a driveline <NUM> to wheels <NUM> that generate a tractive force to move the vehicle <NUM>. A controller <NUM> is operatively connected to the electric motor <NUM> by the inverter <NUM>, and functions to control the generation of torque by converting an accelerator pedal position to a torque output using an accelerator pedal map. Although <FIG> only shows one motor <NUM> driving the wheels of a rear axle, it will apparent that the vehicle <NUM> may be arranged so that it has one motor driving the wheels of a front axle, or may have at least one additional motor to drive the wheels of both the front a and rear axles, or additional motors to drive individual wheels.

<FIG> shows a graph <NUM>, in the form of an accelerator pedal map, relating the torque requested from the electric motor <NUM> to the travel of the accelerator pedal. The skilled reader will understand that this is a simplified section through a map that may also incorporates vehicle speed or actuator speed. A full map would consist of a torque surface in the Z axis based on the accelerator pedal position in one axis and the motor speed or vehicle speed in another axis. The required torque is the output. Line <NUM> shows the road load plotted against the position of the accelerator pedal. For clarity, the term "road load" refers to the torque that opposes the movement of the vehicle <NUM> or, in other words, the torque necessary for maintaining the speed of the vehicle <NUM>. Line <NUM> shows that the torque increases with respect to the accelerator pedal position to a maximum torque output relating to the maximum torque deliverable by the powertrain <NUM> when the accelerator pedal is fully pressed. Conversely, the torque output decreases with respect to pedal position to a minimum when the accelerator pedal is fully released, which relates to the maximum resistive torque or overrun torque requested from the electric motor <NUM> by a powertrain control unit <NUM>. The relationship between the road load and the accelerator pedal position can be characterised generally as being constantly proportional. However, such a relationship cannot deliver a driving experience comparable to what the driver would expect from driving a vehicle comprising an ICE. To this end, the controller <NUM> functions to provide an intuitive driving experience.

With reference to <FIG>, in accordance with an implementation, the controller <NUM> incorporates software to implement the process <NUM> shown in the block diagram. The process <NUM> initiates at step <NUM>, which may be when the vehicle <NUM> is operating under road load conditions. At step <NUM>, the current position of the accelerator pedal is determined. The position of the accelerator pedal is then compared, at step <NUM>, against a reference accelerator pedal position to determine if it is greater than the reference accelerator pedal position. The reference accelerator pedal position relates to the road load accelerator pedal position <NUM>. If it is determined that the accelerator pedal position is greater than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where a torque output is determined using an acceleration pedal <NUM> map before the process <NUM> terminates at step <NUM>. However, if at step <NUM> it is determined that the accelerator pedal position is not greater than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where it is determined if the accelerator pedal position equals or is less than the reference accelerator pedal position. If the accelerator pedal position equals the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where the current torque output is maintained before the process <NUM> terminates at step <NUM>. However, if it is determined, at step <NUM>, that the accelerator pedal position is less than the reference accelerator pedal position, the process <NUM> progresses to step <NUM> where a torque output is determined using a deceleration pedal map <NUM> before the process <NUM> terminates at step <NUM>. It is envisaged that the process <NUM> could repeat continually.

<FIG> shows a graph <NUM>, in the form of an accelerator pedal map, illustrating the operation carried out by the process <NUM>. The relationship between the road load and the accelerator pedal position is shown by line <NUM>. The controller <NUM> is configured to receive a road load signal <NUM>, indicative of the road load, and determine a road load accelerator pedal position signal <NUM>. The road load accelerator pedal position signal <NUM> is indicative of the reference accelerator pedal position. In this example, the reference accelerator pedal position is the road load accelerator pedal position, but for some implementations or circumstances, it may be desirable to determine the reference accelerator pedal position on the basis of other factors in addition to the road load accelerator pedal position. The controller <NUM> is further configured to receive an accelerator pedal position signal <NUM>, which indicates the current accelerator pedal position, and compare the reference accelerator pedal position signal <NUM> and the accelerator pedal position signal <NUM> to determine the position of the accelerator pedal with respect to the reference accelerator pedal position. If the accelerator pedal position is greater than the reference accelerator pedal position, the controller <NUM> determines that an acceleration demand has been requested by the driver of the vehicle <NUM>. In this case, a torque output is determined using an acceleration pedal map <NUM>. On the other hand, if the accelerator pedal position is less than the reference accelerator pedal position, the controller <NUM> decides that a deceleration demand has been requested and determines a torque output using a deceleration pedal map <NUM>. The lower and upper limits of the acceleration pedal map <NUM> are set by the road load and the maximum torque deliverable by the powertrain <NUM>, respectively. Whereas, the lower and upper limits of the deceleration pedal map <NUM> are set by the maximum resistive torque and the road load, respectively. The acceleration and deceleration pedal maps <NUM>, <NUM> are customisable to provide an intuitive driving experience more akin to driving a vehicle comprising an ICE. For example, the acceleration and deceleration pedal maps <NUM>, <NUM> could be customised according to the speed of the vehicle <NUM>.

In an embodiment of the invention, the acceleration pedal map <NUM> comprises a low-speed acceleration pedal map and a high-speed acceleration pedal map. Similarly, the deceleration pedal map <NUM> comprises a low-speed deceleration pedal map and a high-speed deceleration pedal map. The controller <NUM> is configured to receive a vehicle speed signal <NUM>, indicative of the speed of the vehicle <NUM>, and determine a torque output in dependence on the vehicle speed signal <NUM>. If the accelerator pedal position is greater than the reference accelerator pedal position and it is determined that the speed of the vehicle <NUM> is below a predetermined threshold speed the controller <NUM> determines a torque output using the low-speed acceleration pedal map. However, if the accelerator pedal position is greater than the reference accelerator pedal position and the speed of the vehicle <NUM> is greater than the predetermined threshold speed, the controller <NUM> determines a torque output using the high-speed acceleration pedal map. Similarly, if the accelerator pedal position is less than the reference accelerator pedal position and the speed of the vehicle <NUM> is below the predetermined threshold speed, the controller <NUM> determines a torque output using the low-speed deceleration pedal map. Moreover, if the accelerator pedal position is less than the reference accelerator pedal position and the speed of the vehicle <NUM> is greater than the predetermined threshold speed, the controller <NUM> determines a torque output using the high-speed deceleration pedal map.

Alternatively, selection of the low-speed and high-speed acceleration and deceleration pedal maps may be dependent on the vehicle speed relative to different speed limits. If the accelerator pedal position is greater than the reference accelerator pedal position and it is determined that the speed of the vehicle <NUM> equals or is below a predetermined low-speed limit, the controller <NUM> determines a torque output using the low-speed acceleration pedal map. However, if the accelerator pedal position is greater than the reference accelerator pedal position and the speed of the vehicle <NUM> equals or is greater than a predetermined high-speed limit, the controller <NUM> determines a torque output using the high-speed acceleration pedal map. Similarly, if the accelerator pedal position is less than the reference accelerator pedal position and the speed of the vehicle <NUM> equals or is below a predetermined low-speed limit, the controller <NUM> determines a torque output using the low-speed deceleration pedal map. Moreover, if the accelerator pedal position is less than the reference accelerator pedal position and the speed of the vehicle <NUM> equals or is greater than a predetermined high-speed limit, the controller <NUM> determines a torque output using the high-speed deceleration pedal map. The controller <NUM> is further configured to determine a torque output based a combination of the low-speed and high-speed acceleration pedal maps if the accelerator pedal position is greater than the reference accelerator pedal position, but the speed of the vehicle <NUM> is between the low-speed and high-speed limits. Likewise, a torque output is determined based a combination of the low-speed and high-speed deceleration pedal maps when the accelerator pedal position is less than the reference accelerator pedal position, but the speed of the vehicle <NUM> is between the low-speed and high-speed limits. Combining pedal maps may be done by interpolating between the low-speed and high-speed pedal maps in dependence on the vehicle speed.

The graph <NUM> comprises two additional accelerator pedal maps, lines <NUM>, <NUM>. These lines <NUM>, <NUM> represent the torque output necessary for maintaining the speed of the vehicle <NUM> when going from road load conditions to traversing a positive gradient or a negative gradient respectively. Lines <NUM>, <NUM> have been altered to account for the same gradients as lines <NUM>, <NUM>. When the vehicle <NUM> is traversing a positive gradient, the controller <NUM> functions to determine torque output using the positive gradient accelerator pedal map, line <NUM>. It can be seen from comparing lines <NUM>, <NUM> that, for the same accelerator pedal position, the torque output from the positive gradient accelerator pedal map, line <NUM>, is less than the torque necessary for maintaining the speed of the vehicle <NUM> while traversing the positive gradient. That is, the positive gradient accelerator pedal map, line <NUM>, used by the controller <NUM> purposively under compensates for the positive gradient. In order to maintain the speed of the vehicle <NUM>, the driver of the vehicle <NUM> is required to press the accelerator pedal to position to achieve the required torque output. This situation is constructed by the controller <NUM> in order to provide an intuitive driving experience in which the driver would expect to have to press the accelerator pedal to some extent when traversing a positive gradient based on their experience of driving a vehicle comprising an ICE.

Similarly, the driver would expect to have to lift-off or release the accelerator pedal when going downhill. In view of that, the negative gradient accelerator pedal map, line <NUM>, used by the controller <NUM> purposively over compensates for the negative gradient, and so the driver of the vehicle <NUM> is required to release the accelerator pedal in order to maintain the speed of the vehicle <NUM> when traversing a negative gradient. It can be seen that the upper limit of the positive gradient accelerator pedal map, line <NUM>, is offset from the road load accelerator pedal map, line <NUM>, such that it exceeds the maximum torque deliverable by the powertrain <NUM>. This is done in order to prevent the effect of the gradient modification from dissipating, as indicated by line <NUM>, as the torque demand increases away from the road load and towards the maximum torque deliverable by the powertrain <NUM>, which would be counter-intuitive for the driver of the vehicle <NUM>.

Claim 1:
A controller for a vehicle, the controller being configured to:
receive a road load signal (<NUM>) indicative of a torque output suitable for maintaining the current speed of the vehicle;
determine a road load accelerator pedal position signal in dependence on the road load signal, the road load accelerator pedal position signal being indicative of a reference accelerator pedal position;
determine a reference accelerator pedal position signal (<NUM>) in dependence on the road load accelerator pedal position signal;
receive an accelerator pedal position signal (<NUM>) indicative of the current position of the accelerator pedal; and,
compare the reference accelerator pedal position signal (<NUM>) and the accelerator pedal position signal (<NUM>) to determine the position of the accelerator pedal with respect to the reference accelerator pedal position; and,
determine a torque output in dependence on an acceleration pedal map (<NUM>) if the position of the accelerator pedal is greater than the reference accelerator pedal position; or,
determine a torque output in dependence on a deceleration pedal map (<NUM>) if the position of the accelerator pedal is less than the reference accelerator pedal position.