System and method for monitoring vehicle dynamics

Abstract

Aspects of the present invention relate to control system (100) for detecting a dynamic steering event of a vehicle (200) the control system (100) comprising one or more processor (120) collectively c

Description

[0001] SYSTEM AND METHOD FOR MONITORING VEHICLE DYNAMICS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a system and method for monitoring vehicle dynamics. Aspects of the invention relate to a control system, a system, a vehicle, a method and computer-readable instructions.

[0004] BACKGROUND

[0005] In use, a road vehicle may undergo a dynamic steering event, such as oversteer or understeer. There is a higher likelihood of a dynamic steering event occurring when driving on a surface having a low coefficient of friction (a low-mu surface). In these operating conditions, understeer is the prevalent form of dynamic steering event. It would be advantageous to detect the dynamic steering event to enable the vehicle subsystems to be configured accordingly.

[0006] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0007] SUMMARY OF THE INVENTION

[0008] Aspects and embodiments of the invention provide a control system, a system, a vehicle, a method and computer-readable instructions as claimed in the appended claims.

[0009] According to an aspect of the present invention there is provided a control system for detecting a dynamic steering event of a vehicle, the control system comprising one or more processor collectively configured to: receive a first signal comprising a measured yaw parameter of the vehicle; determining an estimated yaw parameter of the vehicle; determine an absolute difference between the measured yaw parameter and the estimated yaw parameter; compare the absolute difference to a yaw parameter threshold; and output a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than the yaw parameter threshold.

[0010] By comparing the measured and estimated yaw parameters, the control system identifies the occurrence of a dynamic steering event, for example at least one of an understeer event and an oversteer event. The dynamic steering event signal is output to indicate that the dynamic steering event has been identified. One or more vehicle subsystem may be controlled in dependence on the dynamic steering event signal. The one or more vehicle subsystem may be controlled to facilitate control of the vehicle during the dynamic steering event. In certain embodiments, the control system may be configured to differentiate between an understeer event and an oversteer event.

[0011] The control system comprises one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein, wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: receive the first signal indicating the measured yaw parameter of the vehicle; determining the estimated yaw parameter of the vehicle; and determining the absolute difference between the measured yaw parameter and the estimated yaw parameter. The at least one electronic processor may be configured to access the at least one memory device and execute the instructions thereon so as to: compare the absolute difference to a yaw parameter threshold; and output a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than the yaw parameter threshold.

[0012] The measured yaw parameter and the estimated yaw parameter relate to the same yaw parameter. The yaw parameter may comprise a yaw rate. The measured yaw parameter may comprise a measured yaw rate; and the estimated yaw parameter may comprise an estimated yaw rate. Alternatively, the yaw parameter may comprise a yaw angle. The measured yaw parameter may comprise a measured yaw angle; and the estimated yaw parameter may comprise an estimated yaw angle. The absolute difference is the difference between the estimated yaw parameter and the measured yaw parameter. The absolute difference may, for example, be the absolute yaw angle difference or the absolute yaw rate difference.

[0013] The measured yaw parameter may be determined in dependence on one or more signal received from at least one sensor provided on the vehicle. The at least one sensor may comprise a yaw rate sensor. The at least one sensor may comprise a gyroscope. In use, the yaw rate sensor may generate a yaw rate signal indicating a yaw rate of the vehicle. The measured yaw parameter may comprise a measured yaw rate. Alternatively, the measured yaw parameter may comprise a measured yaw angle. The measured yaw angle may be determined by integrating the yaw rate signal with respect to time. The measured yaw parameter may be determined by another vehicle subsystem, such as an inertial measurement unit.

[0014] The estimated yaw parameter may be estimated using a vehicle model, for example a kinematic vehicle model or a dynamic vehicle model. The estimated yaw parameter may refer to the kinematically estimated yaw parameter. The vehicle model may be configured to model the dynamic behaviour of the vehicle. The estimated yaw parameter may be estimated in dependence on one or more signal received from at least one sensor provided on the vehicle. The estimated yaw parameter may be an estimated yaw rate. Alternatively, the estimated yaw parameter may be an estimated yaw angle. The estimated yaw angle may be determined in dependence on the steering wheel angle of the steering wheel. A steering wheel position sensor may measure at least one of: the steering wheel angle and the steering speed. Alternatively, or in addition, the estimated yaw angle may be determined in dependence on one or more wheel speed signal from a wheel speed sensor. The or each wheel speed signal provide an indication of a wheel speed of a respective wheel of the vehicle. The estimated yaw parameter may be determined in dependence on the radius of the wheel (tire radius). The one or more processor may collectively determine the estimated yaw parameter. Alternatively, the estimated yaw parameter may be determined by another vehicle subsystem, such as an inertial measurement unit. The control system may receive an estimated yaw parameter signal indicating the estimated yaw parameter.

[0015] The vehicle model used to determine the estimated yaw parameter may be a bicycle model. The bicycle model may, for example, be represented by the equation k(vA2) + L, whereby k is an understeer gradient, v is an absolute longitudinal velocity of the vehicle and L is a wheel base of the vehicle. An estimated yaw rate may be calculated as a product of the model value determined using the bicycle model, a front (road) wheel angle and the absolute longitudinal velocity of the vehicle. The front (road) wheel angle may be determined in dependence on a steering wheel angle, for example in dependence on a steering gear ratio. If the vehicle comprises a rear wheel steering system, a rear wheel steering compensator may be applied to the front (road) wheel angle. The understeer gradient may be modelled or may be determined in dependence on empirical data. Other vehicle models may be used to determine the estimated yaw parameter.

[0016] The estimated yaw parameter may be determined in dependence on one or more of the following: a steering wheel angle, a steering speed, a velocity of the vehicle; a measured longitudinal acceleration of the vehicle, for example measured by a longitudinal accelerometer; a measured lateral acceleration of the vehicle, for example measured by a lateral (transverse) accelerometer; and one or more wheel speed.

[0017] The control system is configured to determine the yaw parameter threshold in dependence on one or more dynamic operating parameter of the vehicle. The yaw parameter threshold may be defined by one or more yaw parameter threshold map. The one or more yaw parameter threshold map may be calibratable. For example, the one or more yaw parameter threshold may be tuned for different vehicles have different dynamic characteristics. The one or more yaw parameter threshold map may define the yaw parameter threshold with respect to the one or more dynamic operating parameter of the vehicle. The control system may access the one or more yaw parameter threshold map to determine the yaw parameter threshold in dependence on the one or more dynamic operating parameter. The control system may be configured to select one of a plurality of yaw parameter threshold maps in dependence on a dynamic operating parameter of the vehicle.

[0018] The one or more dynamic operating parameter may comprise or consist of a velocity (or longitudinal speed). The control system may determine the yaw parameter threshold in dependence on a measured velocity or an estimated velocity of the vehicle. The estimated velocity may be more appropriate due to inaccuracies in the measured velocity of the vehicle which may occur during a dynamic steering event. The measured velocity may be inaccurate due to wheel slip at one or more wheels of the vehicle. The control system may be configured to determine the yaw parameter threshold in dependence on the velocity of the vehicle. A first yaw parameter threshold map may be defined for a first velocity range of the vehicle; and a second yaw parameter threshold map may be defined for a second velocity range of the vehicle (wherein the first and second yaw parameter threshold maps are different from each other). The one or more yaw parameter threshold map may define a relationship between the yaw parameter threshold and the velocity of the vehicle. At least in certain embodiments, the yaw parameter threshold may be adjusted with respect to the velocity of the vehicle. This may help to increase the accuracy with which the dynamic steering events are identified, for example by reducing the identification of false positives. The yaw parameter threshold may be directly proportional to the velocity of the vehicle. At low speeds, the yaw parameter threshold may be relatively small. At high speeds, the yaw parameter threshold may be relatively large. The control system may be configured not to identify dynamic steering events below a threshold velocity, for example below 5 m / s or below 3 m / s.

[0019] The one or more dynamic operating parameter may comprise or consist of a rate of acceleration or deceleration of the vehicle. The one or more dynamic operating parameter may comprise or consist of a determination that the vehicle is accelerating (positive acceleration) or decelerating (negative acceleration). The control system may be configured to select a first yaw parameter threshold map in dependence on a determination that the vehicle is accelerating; and a second yaw parameter threshold map in dependence on a determination that the vehicle is decelerating.

[0020] The control system may be configured to detect the dynamic steering event in dependence on a determination that the vehicle is travelling in a forward direction. For example, the control system may be configured to operate only when the velocity of the vehicle is positive. Alternatively, or in addition, the control system may receive a transmission signal indicating a selected transmission ratio. The control system may be configured to detect a dynamic steering event only when a forward drive ratio is selected. A reverse gear blocker may be incorporated to ensure events are not erroneously detected. Alternatively, the direction of travel of the vehicle may be determined in dependence on a rotational direction of an electric traction machine. The control system may be configured to detect a dynamic steering event only when the rotational direction of the electric traction machine corresponds to a forward direction of travel.

[0021] The control system may be configured to receive an ambient temperature signal indicating an ambient temperature. The ambient temperature signal may be received from a temperature sensor provided on the vehicle. The control system may be configured to detect the dynamic steering event in dependence on a determination that the ambient temperature is less than or equal to an ambient temperature threshold. The control system may be configured not to detect the dynamic steering event in dependence on a determination that the ambient temperature is greater than the ambient temperature threshold. The ambient temperature threshold may define a lower temperature threshold. The ambient temperature threshold may be defined as 279 Kelvin. The ambient temperature threshold may be greater than or less than 279 Kelvin. The control system may be configured to detect the dynamic steering event only when the ambient temperature is less than or equal to the ambient temperature threshold. The ambient temperature threshold may be defined such that the dynamic steering event is detected only when the ambient temperature is sufficiently low that there is a risk of ice.

[0022] The output of the dynamic steering event signal may be suppressed or inhibited when the ambient temperature is less than or equal to the ambient temperature threshold. Alternatively, or in addition, the determination of the absolute difference and / or the comparison may be inhibited.

[0023] The control system may be configured to receive a terrain condition indicator providing an indication of one or more terrain parameters. The terrain condition indicator may indicate that the terrain has a low coefficient of friction (low-mu surface). The control system may be configured to operate so as to detect a dynamic steering event in dependence on a determination that the terrain condition indicator indicates that the terrain has a low coefficient of friction. The control system may not operate to detect a dynamic steering event in dependence on a determination that the terrain condition indicator indicates that the terrain has a high coefficient of friction. A coefficient of friction less than a predetermined friction threshold may be defined as being a low coefficient of friction. The friction threshold may, for example, be defined as 0.4. A coefficient of friction greater than the predetermined friction threshold may be defined as being a high coefficient of friction. The control system may be configured to update or modify an estimated coefficient of friction in dependence on detection of a dynamic steering event. For example, the control system may be configured to reduce the estimated coefficient of friction in dependence on detection of a dynamic steering event. I n a variant, a separate vehicle subsystem may update the estimated coefficient of friction in dependence on the dynamic steering event signal.

[0024] The control system may be configured to detect a dynamic steering event in dependence on a determination that the absolute difference is greater than the yaw parameter threshold for at least a first time threshold. The first time threshold may be a predefined time threshold. The control system may be configured to output the dynamic steering event signal in dependence on a determination that the absolute difference is greater than the yaw parameter threshold for at least the first time threshold. The first time threshold implements a delay logic which filters the signal. At least in certain embodiments, this may help to detect only those events that are most likely to be a dynamic steering event. This may reduce the identification of false positives.

[0025] After detecting a dynamic steering event, the control system may be configured to determine that the dynamic steering event has ended in dependence on a determination that the absolute difference is less than the yaw parameter threshold for at least a second time threshold. The second time threshold may be a predefined time threshold. The control system may be configured to halt or interrupt the output of the dynamic steering event signal in dependence on a determination that the absolute difference is less than the yaw parameter threshold for at least the second time threshold.

[0026] The first and second time thresholds may be the same as each other. Alternatively, the second time threshold may be greater than the first time threshold. The first time threshold may be 0.3 seconds; and the second time threshold may be 0.9 seconds.

[0027] The dynamic steering event may comprise or consist of a vehicle understeer event. The control system may be configured to identify the dynamic steering event as a vehicle understeer event in dependence on a determination that the measured yaw parameter is less than the estimated yaw parameter.

[0028] The dynamic steering event may comprise or consist of a vehicle oversteer event. The control system may be configured to identify the dynamic steering event as a vehicle oversteer event in dependence on a determination that the measured yaw parameter is greater than the estimated yaw parameter.

[0029] The control system may be configured to quantify the dynamic steering event in dependence on a magnitude of the absolute difference between the measured yaw parameter and the estimated yaw parameter. The dynamic steering event may be quantified as a value or a percentage. The control system may quantify the dynamic steering event in direct proportion to the magnitude of the absolute difference. This may provide additional information regarding the extent of the dynamic steering event. This may enable more accurate classification than an ON / OFF detection of the dynamic steering event.

[0030] According to a further aspect of the present invention there is provided a control system for detecting a dynamic steering event of a vehicle, the control system comprising one or more processor collectively configured to: determine a measured yaw parameter of the vehicle; determine an estimated yaw parameter of the vehicle; calculate a difference between the measured yaw parameter and the estimated yaw parameter; compare the difference to a yaw parameter threshold; and output a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the difference is greater than the yaw parameter threshold.

[0031] According to a further aspect of the present invention there is provided a system comprising the control system described herein and a vehicle control unit for controlling at least one vehicle subsystem of the vehicle. The vehicle control unit may be configured to modify the operation of the at least one vehicle subsystem in dependence on receipt of the dynamic steering event signal from the control system. The at least one vehicle subsystem may be operable in a plurality of subsystem control modes.

[0032] A plurality of vehicle subsystem control modes may be defined, for example in a memory device. The vehicle subsystem control modes may be defined to control operation of the at least one vehicle subsystem. The vehicle control unit may be configured to determine a combined probability value of each of the vehicle subsystem control modes. One of the plurality of vehicle subsystem control modes may be selected in dependence on the determined combined probability values. The vehicle control unit may then operate in the selected one of the plurality of vehicle subsystem control modes.

[0033] The plurality of vehicle subsystem control modes may include a low-friction surface subsystem control mode. The vehicle control unit may be configured to increase the combined probability value associated with the low-friction surface subsystem control mode in dependence on the receipt of the dynamic steering event signal from the control system indicating detection of a dynamic steering event. The likelihood of the low-friction surface subsystem control mode being selected is thereby increased. At least in certain embodiments, the low-friction surface subsystem control mode configures the vehicle subsystems to facilitate control of the vehicle on a low-friction surface.

[0034] The vehicle control unit may be configured to determine if an ambient temperature is less than or equal to a temperature threshold. The vehicle control unit may be configured to select the low-friction surface subsystem control mode in dependence on a determination that the ambient temperature is than or equal to the temperature threshold.

[0035] The vehicle control unit may be configured to select a predetermined one of the subsystem control modes in dependence on receipt of the dynamic steering event signal. The vehicle control unit may, for example, request a control mode which is pre-configured to implement suitable control parameters for the vehicle subsystems when the vehicle is operating on a low friction surface. The vehicle control unit may, for example, select a Grass, Gravel Sand control mode in dependence on the receipt of the dynamic steering event signal.

[0036] In dependence on the receipt of the dynamic steering event signal, the vehicle subsystems may implement one or more of the following control strategies: reduce throttle response rate; reduce power output to rear axle; and increase power output to the front axle.

[0037] One or more of these control strategies may facilitate control of the vehicle during the dynamic steering event.

[0038] According to a further aspect of the present invention there is provided a vehicle comprising the system described herein, or the control system described herein.

[0039] According to a further aspect of the present invention there is provided a method of detecting a dynamic steering event of a vehicle, the method comprising: measuring a yaw parameter of the vehicle; estimating a yaw parameter of the vehicle; determining an absolute difference between the measured yaw parameter and the estimated yaw parameter; comparing the absolute difference to a yaw parameter threshold; and outputting a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than or equal to the yaw parameter threshold.

[0040] Measuring the yaw parameter of the vehicle may comprise measuring a yaw rate of the vehicle. The yaw rate may optionally be converted to a yaw angle, for example by integrating the yaw rate. The method may comprise receiving a first signal comprising a measured yaw parameter of the vehicle. Estimating the yaw parameter of the vehicle may comprise modelling dynamic behaviour of the vehicle, for example using a vehicle model. The yaw parameter may be estimated in dependence on one or more of the following: a steering wheel angle, a steering speed, a velocity of the vehicle; a measured longitudinal acceleration, for example measured by a longitudinal accelerometer; a measured lateral acceleration, for example measured by a lateral (transverse) accelerometer; and one or more wheel speed.

[0041] The measured yaw parameter and the estimated yaw parameter relate to the same yaw parameter. The yaw parameter may comprise a yaw rate. Alternatively, the yaw parameter may comprise a yaw angle. The measured yaw parameter may comprise a measured yaw angle; and the estimated yaw parameter may comprise an estimated yaw angle.

[0042] According to a further aspect of the present invention there is provided a computer readable instructions which, when executed by a computer, are arranged to perform a method(s) as described herein.

[0043] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0046] Figure 1 shows a schematic representation of a vehicle incorporating a control system for detecting a dynamic steering event according to an embodiment of the present invention;

[0047] Figure 2 shows a schematic representation of the control system and the subsystems of the vehicle shown in Figure 1 ;

[0048] Figure 3 shows a schematic representation of an inertial measurement unit for determining an estimated and a measured yaw parameter for the control system;

[0049] Figure 4 shows a schematic representation of the control system according to an embodiment of the present invention;

[0050] Figure 5A shows a block diagram representing a method of detecting a dynamic steering event;

[0051] Figure 5B shows a block diagram representing the implementation of the method shown in Figure 5A to select a subsystem control mode to facilitate vehicle control in dependence on detection of a dynamic steering event;

[0052] Figure 6 shows a first plot illustrating the operation of the control system to detect an oversteer event in an anti-clockwise direction;

[0053] Figure 7 shows a second plot illustrating the operation of the control system to detect an oversteer event in a clockwise direction;

[0054] Figure 8 shows a third plot illustrating the operation of the control system to detect an understeer event in an anti-clockwise direction;

[0055] Figure 9 shows a fourth plot illustrating the operation of the control system to detect an understeer event in a clockwise direction;

[0056] Figure 10 is a schematic representation of the vehicle showing the geometry for calculating the estimated yaw rate; and

[0057] Figure 11 is a block diagram illustrating the calculation of the estimated yaw rate.

[0058] DETAILED DESCRIPTION

[0059] A control system 100 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures. As shown in Figure 1 , the control system 100 is installed in a vehicle 200. The control system 100 is configured to identify a dynamic steering event in the vehicle 200. The dynamic steering event may be one of an oversteer event and an understeer event.

[0060] The vehicle 200 is described herein with reference to a reference frame comprising a longitudinal axis X, a transverse axis Y and a vertical axis Z. The reference signs herein include a suffix in the form of a whole number to differentiate between a plurality of like components on the vehicle 200. The same suffix is applied for components associated with each other, for example components forming part of the same sub-assembly of the vehicle 200. The roll, pitch and yaw of the vehicle 200 are rotations about the longitudinal axis X, the transverse axis Y and the vertical axis Z, respectively. A yaw angle of the vehicle is the instantaneous angle of the vehicle as it rotates about an axis, here defined as the vertical axis Z. A yaw rate wzof the vehicle 200 is a rate of change of the yaw angle with respect to time. The yaw angle can be calculated by integration of the yaw rate wzwith respect to time.

[0061] The vehicle 200 is a road vehicle, such as an automobile, a sports utility vehicle (SUV) or a utility vehicle. As shown in Figures 1 and 2, the vehicle 200 in the present embodiment is an automobile. The vehicle 200 comprises one or more torque-generating machine, such as an internal combustion engine (ICE) and / or an electric traction motor. The vehicle 200 may be a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) or an internal combustion engine (ICE) vehicle. The vehicle 200 comprises a vehicle body 205. The vehicle 200 comprises four (4) wheels W which movably carry the vehicle body 205 in a driving direction. The wheels W comprise a front left wheel WFL, a front right wheel WFR, a rear left wheel WRL and a rear right wheel WRR. The front left and right wheels WFL, WFR and / or the rear left and right wheels WRL, WRR may be driven by the one or more torque-generating machine. In the present embodiment, the vehicle 200 is four-wheel drive and each of the wheels W is driven by the one or more torque-generating machine. A wheel speed sensor WS1 -WS4 is associated with each of the wheels W. The wheel speed sensors WS1-WS4 may, for example, form part of an antilock braking system (ABS). The wheel speed sensors WS1-WS4 are configured to output wheel speed signals SWS1-SWS4. The wheel speed signals SWS1-SWS4 are electrical signals which are indicative of the rotational (angular) speed w of each of the wheels W of the vehicle 200. In a variant, the wheel speed signals SWS1-SWS4 may be indicative of a linear velocity of the each of the wheels W.

[0062] The vehicle 200 comprises a plurality of vehicle subsystems. The vehicle subsystems in the present embodiment include, but are not limited to, a traction control system 220A (shown in Figure 4), a propulsion (or engine) management system 220B, a transmission system 220C, a steering system 220D, an anti-lock braking system (ABS) 220E, a suspension system 220F and a differential system 220G. Although seven (7) subsystems are illustrated, the vehicle 200 may include additional vehicle subsystems and are collectively referred to with the reference numeral 220. One or more vehicle control unit 225 is provided to control operation of the vehicle subsystems 220. The control system 100 and the one or more vehicle control unit 225 in combination form a system VS1 for controlling operation of the vehicle subsystems 220 in dependence on the detection of a dynamic steering event.

[0063] The steering system 220D comprises a steering wheel 230 which is rotatable in response to steering inputs from a driver of the vehicle 200. The trajectory of the vehicle 200 is controlled in dependence on the steering inputs. The orientation of each of the front wheels WFR, WFL is controlled in dependence on the orientation of the steering wheel 230. A steering angle sensor 235 monitors a steering wheel angle a of the steering wheel 230. A front (road) wheel angle p is controlled in dependence on the steering wheel angle a to steer the vehicle 200. The steering angle sensor 235 outputs a steering wheel angle signal 240. The relationship between the steering wheel angle a and the front (road) wheel angle p is known, for example in dependence on a steering gear ratio. The front (road) wheel angle p can be determined in dependence on the steering wheel angle a. The steering system 220D may optionally comprise a rear wheel steering system operable to control a rear (road) wheel angle. The dynamic behaviour of the vehicle 200 is modelled in dependence on the front (road) wheel angle and optionally also the rear (road) wheel angle. The steering wheel angle signal 240 is an electrical signal which is indicative of the steering wheel angle a measured by the steering angle sensor 235. In the present embodiment, the front left and right wheels WFL, WFR are steerable to control the trajectory of the vehicle 200. A wheel angle of each of the front left and right wheels WFL, WFR is controlled in dependence on the steering wheel angle a to steer the vehicle 200. The steering wheel angle a thereby determines a turning radius (trajectory) of the vehicle 200. In a variant, a wheel angle of the rear left and right wheels WRL, WRR is also controlled in dependence on the steering wheel angle a to provide additional steering control. The front (road) wheel angle p may be adjusted to compensate for rear wheel steering (if fitted to the vehicle 200). The steering angle sensor 235 may optionally also monitor a steering wheel angle velocity of the steering wheel 230.

[0064] The propulsion (or engine) management system 220B comprises a propulsion controller (not shown). The vehicle 200 comprises a throttle (accelerator) pedal 250 and a throttle pedal position sensor 255. The throttle pedal 250 is operable by a driver of the vehicle 200 to control operation of the torque-generating machine. The throttle pedal position sensor 255 is configured to measure a position of the throttle pedal 250. The throttle pedal position sensor 255 outputs a pedal position signal 260S to the propulsion controller. The pedal position signal 260S is an electrical signal which is indicative of the position of the throttle pedal 250. The propulsion controller (not shown) determines a torque request in dependence on the pedal position signal 260S. Alternatively, or in addition, the torque request may be generated by an onboard system, such as a cruise control system or other vehicle control system.

[0065] The vehicle 200 comprises a temperature sensor 265 configured to measure the ambient temperature. The temperature sensor 265 outputs an ambient temperature signal STA indicating the measured ambient temperature.

[0066] The control system 100 is configured to detect a dynamic steering event. For a constant steering wheel angle a on a flat and level surface, the vehicle 200 follows a trajectory having a constant radius. A dynamic steering event represents a variation or deviation in the trajectory of the vehicle 200 from these steady-state conditions. The dynamic steering event may be an oversteer event or an understeer event. An oversteer event occurs when the vehicle 200 turns (steers) by more than the steering input from the driver. Conversely, an understeer event occurs when a vehicle 200 turns (steers) by less than the steering input from the driver. Both involve wheel slippage on the ground. In the case of understeer, the front wheels do not grip and so the vehicle turns less than the front wheels would direct in the absence of slippage. In the case of oversteer, the rear wheels do not grip and the vehicle rotates (yaws) to a greater extent than the front wheels would direct in the absence of slippage.

[0067] The control system 100 is configured to detect the dynamic steering event by comparing a measured yaw parameter and an estimated yaw parameter of the vehicle 200. The yaw parameter in the present embodiment is a yaw rate wzof the vehicle 200. The yaw angle is defined as the angle between the longitudinal axis X of the vehicle 200 and an axis parallel to the surface of the earth in an earth-fixed coordinate system. The yaw rate Wz is the rate of change of the yaw angle with respect to time. The suffixes (E) and (M) are used herein to differentiate between the estimated yaw rate wz(E) and the measured yaw rate wz(M). In a variant, the yaw parameter is a yaw rate of the vehicle 200. The control system 100 in this arrangement is configured to compare the measured yaw rate and the estimated yaw rate.

[0068] The vehicle 200 comprises an inertial measurement unit (IMU) 300 (see Figure 3) for determining the (instantaneous) measured yaw rate wz(M) of the vehicle 200. The IMU 300 comprises a yaw rate sensor 305 disposed on a vertical axis Z of the vehicle 200. The yaw rate sensor 305 is configured to measure rotation about the vertical axis Z. The yaw rate sensor 305 in the present embodiment is a gyroscope 305. The yaw rate sensor 305 is configured to output a yaw rate signal SYR to the IMU 300. The yaw rate signal SYR is an electrical signal which is indicative of the yaw rate of the vehicle 200. The IMU 300 comprises one or more controller 310 configured to determine the measured yaw rate wz(M). The one or more controller 310 comprises at least one electrical processor 315 having an electrical input 320 for receiving the yaw rate signal SYR. The one or more controller 310 may optionally integrate the yaw rate signal SYR to determine the measured yaw angle (M) . The at least one electrical processor 315 comprises an electrical output 325 for outputting a measured yaw rate signal SYA(M). The measured yaw rate signal SYA(M) is an electrical signal indicative of the measured yaw rate wz(M). The one or more controller 310 comprises memory means 330. The memory means 330 may be one or more memory device 330. In a variant, the control system 100 may determine the (instantaneous) measured yaw angle (M).

[0069] The one or more controller 310 of the IMU 300 is configured to implement an absolute velocity estimator. The IMU 300 comprises one or more accelerometer 335. The one or more accelerometer 335 output an accelerometer signal indicating a longitudinal acceleration along the longitudinal axis X of the vehicle 200. The one or more controller 310 is configured to estimate the absolute velocity of the vehicle 200 in dependence on the accelerometer signal. The electrical output 325 of the at least one electrical processor 315 is configured to output an absolute velocity signal SAV. The absolute velocity signal SAV is an electrical signal which indicates an estimated absolute velocity VLS of the vehicle 200.

[0070] As shown in Figure 4, the control system 100 comprises one or more controller 110. The control system 100 is configured to receive the measured yaw rate signal SYA(M) and the absolute velocity signal SAV. The one or more controller 110 is configured to detect a dynamic steering event of the vehicle 200. The control system 110 is configured to output a dynamic steering event signal 155. The operation of one or more of the vehicle subsystems 220 may be controlled in dependence on the dynamic steering event signal 155.

[0071] The control system 100 as illustrated in Figure 4 comprises one controller 110, although it will be appreciated that this is merely illustrative. The controller 110 comprises processing means 120 and memory means 130. The processing means 120 may be one or more electronic processing device 120 which operably executes computer-readable instructions. The one or more electronic processing device 120 are referred to herein as one or more processor 120. The one or more processor 120 collectively implement the method(s) 400 described herein. The memory means 130 may be one or more memory device 130. The memory means 130 is electrically coupled to the processing means 120. The memory means 130 is configured to store instructions, and the processing means 120 is configured to access the memory means 130 and execute the instructions stored thereon.

[0072] The controller 110 comprises an input means 140 and an output means 150. The input means 140 may comprise an electrical input 140 of the controller 110. The output means 150 may comprise an electrical output 150 of the controller 110. The input 140 is arranged to receive, among other signals, the measured yaw rate signal SYA(M) and the absolute velocity signal SAV. The output 150 is arranged to output a dynamic steering event signal 155 which is indicative of the detection of a dynamic steering event. The dynamic steering event signal 155 is output to control operation of one or more of the vehicle subsystems 220. The output 150 may be arranged to output a signal to indicate that the dynamic steering event has concluded. Alternatively, an absence of the dynamic steering event signal 155 may indicate that the dynamic steering event has concluded.

[0073] The controller 110 is configured to determine an estimated yaw rate wz(E). The estimated yaw rate wz(E) is determined in dependence on the steering wheel angle a of the steering wheel 230. In the present embodiment, the controller 110 is configured to determine the (instantaneous) estimated yaw rate wz(E) of the vehicle 200. The control system 100 implements a yaw rate estimator to determine the estimated yaw rate wz(E). The one or more processor 120 receives the steering wheel angle signal 240 from the by the steering angle sensor 235. The one or more electronic processing device 120 calculates the estimated yaw rate wz(E) using one or more vehicle model. The estimated yaw rate wz(E) is determined in dependence on the steering wheel angle a of the steering wheel 230 and on the wheel speed signals SWS1-SWS4 from the wheel speed sensors WS1-WS4. The calculation of the estimated yaw rate wz(E) is described below with reference to Figures 10 and 11. The electrical output 150 of the one or more processor 120 outputs a first signal SYA(E). The first signal SYA(E) is a yaw parameter signal indicating the estimated yaw parameter. I n the present embodiment, the first signal SYA(E) is an estimated yaw rate signal SYA(E).

[0074] The estimated yaw rate signal SYA(E) indicates the estimated yaw rate wz(E); and the measured yaw rate signal SYA(M) indicates the measured yaw rate wz(M). The one or more processor 120 collectively determine the absolute difference between the estimated yaw rate wz(E) and the measured yaw rate wz(M). The absolute difference is compared to a yaw parameter threshold YPT. The one or more processor 120 is configured to output a dynamic steering event signal 155 indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than the yaw parameter threshold. The determination of the yaw parameter threshold YPT will now be described.

[0075] The yaw parameter threshold YPT is determined in dependence on one or more yaw parameter threshold map YPM-n (where the suffix n is an integer greater than or equal to one and applied to identify one of the one or more yaw parameter threshold map). The one or more yaw parameter threshold map YPM-n are stored in the memory device 130. The one or more yaw parameter threshold map YPM-n is calibratable. In the present embodiment, the yaw parameter threshold YPT is determined in dependence on a plurality of the yaw parameter threshold maps. The yaw parameter threshold maps YPM-n are each associated with one or more dynamic operating parameter of the vehicle 200. The one or more processor 120 is configured to select one of the plurality of yaw parameter threshold maps YPM-n in dependence on the one or more dynamic operating parameter. In the present embodiment, one of the plurality of yaw parameter threshold maps YPM-n is selected in dependence on the current (instantaneous) absolute velocity of the vehicle 200. A first yaw parameter threshold map YPM-1 is defined for a first velocity range of the vehicle 200; and a second yaw parameter threshold map YPM-2 is defined for a second velocity range of the vehicle 200. The first velocity range may, for example, be Okph to 60kph; and the second velocity range may, for example, be 60kph to 10Okph. The one or more processor 120 is configured to determine the estimated absolute velocity VLS in dependence on the absolute velocity signal SAV. The controller 110 selects one of the plurality of yaw parameter threshold maps YPM-n in dependence on the estimated absolute velocity VLS. The yaw parameter threshold YPT is read from the selected yaw parameter threshold map YPM-n.

[0076] In the present embodiment, the one or more processor 120 is configured to implement a timer function to control the output of the dynamic steering event signal 155. The one or more processor 120 is configured to output the dynamic steering event signal 155 in dependence on a determination that the determined absolute difference is greater than the yaw parameter threshold YPT for at least a predetermined first time threshold. The first time threshold functions as a filter to ensure that only the most likely dynamic steering events are detected. Conversely, the one or more processor 120 is configured to determine that the dynamic steering event has concluded in dependence on a determination that the absolute difference is less than the yaw parameter threshold YPT for at least a predetermined second time threshold. The one or more processor 120 is configured to halt (or stop) the output of the dynamic steering event signal 155 upon expiry of the second time threshold. The second time threshold may be greater than the first time threshold. For example, the first time threshold may be 0.3 seconds; and the second time threshold may be 0.9 seconds. The first and second time thresholds are calibratable.

[0077] A method 400 of detecting a dynamic steering event is illustrated in Figure 5A. The method 400 comprises determining the measured yaw rate wz(M) (BLOCK 405); and determining the estimated yaw rate wz(E) (BLOCK 410). The estimated yaw rate wz(E) is subtracted from the measured yaw rate wz(M) (BLOCK 415) to determine yaw rate difference. An absolute value of the yaw rate difference is determined (BLOCK 420). The determined absolute yaw rate difference (Awz) is output for comparison to a yaw parameter threshold YPT. The yaw parameter threshold YPT is determined in dependence on the estimated absolute velocity of the vehicle 200. The absolute velocity estimate is determined (BLOCK 425). One of the plurality of yaw parameter threshold maps YPM-n is selected in dependence on the absolute velocity estimate (BLOCK 430). The absolute yaw rate difference (Awz) is compared to the determined yaw parameter threshold YPT read from the selected yaw parameter threshold map YPM-n. A determination is made if the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT (BLOCK 435). A dynamic steering event signal 155 in the form of an understeer or oversteer event signal is output if the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. A timer delay and / or reverse block logic is implemented (BLOCK 440). The dynamic steering event signal 155 indicating detection of a dynamic steering event is generated (BLOCK 445).

[0078] A method 450 of selecting a vehicle subsystem control mode in dependence on the detection of a dynamic steering event is illustrated in Figure 5B. The vehicle subsystem control mode defines operating parameters of the one or more vehicle subsystems 220 to control the dynamic operation of the vehicle 200. The selected subsystem control mode controls the vehicle subsystems 220 to configure the vehicle 200 for operation on a surface / terrain having a low surface friction. The selected subsystem control mode is referred to herein as a low-friction surface subsystem control mode. The low-friction surface subsystem control mode may, for example, be a Grass / Gravel / Snow subsystem control mode. The method 450 is described with reference to the detection of a dynamic steering event in the form of an understeer event. It will be understood that the method 450 could be implemented for a dynamic steering event in the form of an oversteer event.

[0079] The method 450 comprises determining a vehicle speed Vref (BLOCK 455). The vehicle speed may, for example, be determined in dependence on a vehicle speed signal. An understeer probability map is selected in dependence on the determined vehicle speed Vref (BLOCK 460). One of a plurality of understeer probability maps may be selected in dependence on the determined vehicle speed Vref. A dynamic steering event (in the form of an understeer event) is detected (BLOCK 465). The dynamic steering event is detected using the method 400 described herein. An ambient temperature is determined (BLOCK 470). The ambient temperature in the present embodiment is indicated by the ambient temperature signal STA indicated by the temperature sensor 265. A check is performed to determine if the ambient temperature is less than or equal to a temperature threshold (BLOCK 475). The temperature threshold in the present embodiment is defined as 279 Kelvin. The temperature threshold may be greater than or less than 279 Kelvin. A first conditional check is implemented to determine if the ambient temperature is less than or equal to the temperature threshold and the understeer steering event is detected (BLOCK 480). In dependence on a determination that the ambient temperature is less than or equal to the temperature threshold and the understeer steering event is detected, a second conditional check is performed to analyse the selected understeer probability map (BLOCK 485). A combined probability value is output from the second switch (BLOCK 490). The combined probability value is associated with the low-friction surface subsystem control mode. The combined probability value is applied to increase the probability that the low-friction surface subsystem control mode is selected. There is a corresponding increase in the probability of selecting the low-friction surface subsystem control mode. The low-friction surface subsystem control mode is selected more quickly, thereby facilitating control of the vehicle 200 during the dynamic steering event. The combined probability value is not modified if the ambient temperature is greater than the ambient temperature threshold. At least in certain embodiments, the selection of the low-friction surface subsystem control mode facilitates control of the vehicle 200 to conclude the dynamic steering event.

[0080] A first plot 500 shown in Figure 6 illustrates a dynamic steering event in the form of an oversteer dynamic steering event in an anti-clockwise (counter clockwise) direction (a generally positive steering angle a of the steering wheel). A first plot line 510 represents the measured yaw rate wz(M); and a second plot line 520 represents the estimated yaw rate wz(E). A third plot line 530 represents the output of the dynamic steering event signal 155 to indicate the detection of the dynamic steering event. A fourth plot line 540 represents a determination that the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The third and fourth plot lines 530, 540 are plotted on the same axis. The third plot line 530 has a value of “1” when the dynamic steering event signal 155 is not output; and a value of “2” when the dynamic steering event signal 155 is output. The fourth plot line 540 has a value of “0” when the absolute yaw rate difference (Awz) is less than the determined yaw parameter threshold YPT; and a value of “1” when the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The application of the timer function to filter the output of the dynamic steering event signal 155 results in the variations between the third and fourth plot lines 530, 540. In the present example, the third plot line 530 represents the output of the dynamic steering event signal 155 for the time period from t1 to t2. A fifth plot line 550 represents the steering wheel angle a of the steering wheel 230.

[0081] A second plot 600 shown in Figure 7 illustrates a dynamic steering event in the form of an oversteer dynamic steering event in a clockwise direction (a generally negative steering angle a of the steering wheel). A first plot line 610 represents the measured yaw rate wz(M); and a second plot line 620 represents the estimated yaw rate Wz(E). A third plot line 630 represents the output of the dynamic steering event signal 155 to indicate the detection of the dynamic steering event. A fourth plot line 640 represents a determination that the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The third and fourth plot lines 630, 640 are plotted on the same axis. The third plot line 630 has a value of “1” when the dynamic steering event signal 155 is not output; and a value of “2” when the dynamic steering event signal 155 is output. The fourth plot line 640 has a value of “0” when the absolute yaw rate difference (Awz) is less than the determined yaw parameter threshold YPT; and a value of “1” when the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The application of the timer function to filter the output of the dynamic steering event signal 155 results in the variations between the third and fourth plot lines 630, 640. In the present example, the third plot line 630 represents the output of the dynamic steering event signal 155 for a first time period from t1 to t2 and a second time period from t3 to t4. A fifth plot line 650 represents the steering wheel angle a of the steering wheel 230.

[0082] A third plot 700 shown in Figure 8 illustrates a dynamic steering event in the form of an understeer dynamic steering event in an anti-clockwise (counter-clockwise) direction (a generally positive steering angle a of the steering wheel). A first plot line 710 represents the measured yaw rate Wz(M); and a second plot line 720 represents the estimated yaw rate Wz(E). A third plot line 730 represents the output of the dynamic steering event signal 155 to indicate the detection of the dynamic steering event. A fourth plot line 740 represents a determination that the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The third and fourth plot lines 730, 740 are plotted on the same axis. The third plot line 730 has a value of “1” when the dynamic steering event signal 155 is not output; and a value of “2” when the dynamic steering event signal 155 is output. The fourth plot line 740 has a value of “0” when the absolute yaw rate difference (Awz) is less than the determined yaw parameter threshold YPT; and a value of “1” when the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The application of the timer function to filter the output of the dynamic steering event signal 155 results in the variations between the third and fourth plot lines 730, 740. In the present example, the third plot line 730 represents the output of the dynamic steering event signal 155 for the time period from t1 to t2. A fifth plot line 750 represents the steering wheel angle a of the steering wheel 230.

[0083] A fourth plot 800 shown in Figure 9 illustrates a dynamic steering event in the form of an understeer dynamic steering event in a clockwise direction (a generally negative steering angle a of the steering wheel). A first plot line 810 represents the measured yaw rate wz(M); and a second plot line 820 represents the estimated yaw rate Wz(E). A third plot line 830 represents the output of the dynamic steering event signal 155 to indicate the detection of the dynamic steering event. A fourth plot line 840 represents a determination that the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The third and fourth plot lines 830, 840 are plotted on the same axis. The third plot line 830 has a value of “1” when the dynamic steering event signal 155 is not output; and a value of “2” when the dynamic steering event signal 155 is output. The fourth plot line 840 has a value of “0” when the absolute yaw rate difference (Awz) is less than the determined yaw parameter threshold YPT; and a value of “1” when the absolute yaw rate difference (Awz) is greater than the determined yaw parameter threshold YPT. The application of the timer function to filter the output of the dynamic steering event signal 155 results in the variations between the third and fourth plot lines 830, 840. In the present example, the third plot line 830 represents the output of the dynamic steering event signal 155 for the time period from t1 to t2. A fifth plot line 850 represents the steering wheel angle a of the steering wheel 230. The dynamic steering event may comprise or consist of a vehicle understeer event or a vehicle oversteer event. In a variant, the control system 100 may be configured to differentiate between an understeer event and an oversteer event. The dynamic steering event may comprise or consist of a vehicle understeer event. The control system 100 may be configured to identify the dynamic steering event as a vehicle understeer event in dependence on a determination that the measured yaw parameter is less than the estimated yaw parameter. The control system 100 may be configured to identify the dynamic steering event as a vehicle oversteer event in dependence on a determination that the measured yaw parameter is greater than the estimated yaw parameter.

[0084] The control system 100 may be configured to update or modify an estimated coefficient of friction in dependence on detection of a dynamic steering event. For example, the control system 100 may be configured to reduce the estimated coefficient of friction in dependence on detection of a dynamic steering event. In a variant, a separate vehicle 200 subsystem may update the estimated coefficient of friction in dependence on the dynamic steering event signal.

[0085] As described herein, the yaw rate is measured by the gyroscope 305 that measures a rate of change of the angle of the vehicle 200 about a vertical axis Z. A difference in the heading of the vehicle 200 (direction of travel) and the velocity is referred to as the slip angle. The slip angle is related to the yaw rate.

[0086] A vehicle model is used to calculate the estimated yaw rate wz(E). The vehicle model in the present embodiment is a simplified vehicle model for lateral dynamics using a bicycle model, where both right hand and left-hand tyres are grouped in a single entity and the vehicle 200 is assumed to have its mass distributed along its centre line. The estimated yaw rate wz(E) is calculated in dependence on an understeer gradient k. The understeer gradient k is the derivative of the average front (road) wheel steer angle p with respect to the lateral acceleration imposed to the vehicle 200 at its centre of gravity. The lateral acceleration is measured through a constant radius circular manoeuvre with progressively increasing the longitudinal velocity (resulting in a corresponding increase in the lateral acceleration) while remaining proximal to a steady-state condition. The understeer gradient k evaluates the tendency of the vehicle 200, when in a steady-state curve manoeuvre, to understeer (where the vehicle 200 requires a greater steering wheel angle to keep the same curve radius at higher speeds) or oversteer (where the vehicle 200 requires a lower steering wheel angle to keep the same curve radius at higher speeds). The vehicle 200 is neutral when the steering wheel angle to keep a curve trajectory is dependant only on the curve radius and not on the vehicle speed.

[0087] The calculation of an estimated yaw rate (E) will now be described with reference to Figures 10 and 11. The geometry of the vehicle 200 is shown in Figure 10. The wheels W each have an effective tire radius r. A front track width WTF is the transverse distance between the front left wheel WFL and the front right wheel WFR. A rear track width WTR is the transverse distance between the rear left wheel WRL and the rear right wheel WRR. A distance between the reference vertical axis Z and the front axle is referred to as the front longitudinal base WLF. A distance between the reference vertical axis Z and the rear axle is referred to as the rear longitudinal base WLR. The wheel speed sensors WS1 -WS4 measure the rotational (angular) speed w of each of the wheels W. A front right rotational (angular) speed wFR is the angular speed of the front right wheel WFR; a front left rotational (angular) speed wFL is the angular speed of the front left wheel WFL; a rear right rotational (angular) speed wRR is the angular speed of the rear right wheel WRR; and a rear left rotational (angular) speed wRL is the angular speed of the rear left wheel WRL. The product of the rotational (angular) speed w and the effective tire radius r provides a linear velocity value of each wheel W. The linear velocity may be output from the wheel speed sensors WS1-WS4. The front left and front right wheels WFL, WFR are inclined relative to the longitudinal axis X at the front (road) wheel angle p (which is determined in dependence on the steering wheel angle a).

[0088] The estimated yaw rate wz(E) is calculated using the following equation: where wz(E) = Estimated Yaw Rate

[0089] 6 = Compensated Roadwheel Angle k = Understeer Gradient

[0090] L = Vehicle Wheelbase Length, and v = Vehicle Velocity

[0091] The understeer gradient k is a calibrated value in the present embodiment. In a variant, the understeer gradient k may be calculated or modelled.

[0092] The compensated roadwheel angle is an angle derived to account for the utilisation of rear wheel steering (also referred to as all wheel steering), as required.

[0093] The vehicle model may be a bicycle model represented by the equation: fc(v2) + L (5)

[0094] Whereby : k is the understeer gradient; v is the absolute longitudinal velocity of the vehicle; and L is the vehicle wheel base.

[0095] The estimated yaw rate wz(E) is the product of the following: a (bicycle) model value determined using the bicycle model, a front (road) wheel angle and the absolute longitudinal velocity of the vehicle 200.

[0096] A block diagram 900 representing the operation of the processor 110 to calculate the estimated yaw rate wz(E) is shown in Figure 11. The steering wheel angle a is input (BLOCK 905). A rear (road) wheel angle is input (BLOCK 910). A signal indicating whether the steering system 220D comprises a rear wheel steering system is input (BLOCK 915). A front (road) wheel angle p is determined (BLOCK 920). If the steering system 220D comprises a rear wheel steering system, a front (road) wheel angle compensation factor 6 is determined to compensate for the rear (road) wheel angle. The front (road) wheel angle is modified to compensate for the rear (road) wheel angle. An absolute longitudinal velocity of the vehicle 200 is input (BLOCK 925). The product of the front (road) wheel angle p and the absolute longitudinal velocity v is determined (BLOCK 930). The absolute longitudinal velocity v is squared (BLOCK 935). The understeer gradient k is calculated (BLOCK 940). The product of the understeer gradient k and the square of the absolute longitudinal velocity v is determined (BLOCK 945). The wheelbase L is determined (BLOCK 950). The wheel base L and the product of the understeer gradient k and the value vA2 are summed (BLOCK 955). The bicycle model represented by the equation k(vA2) + L is thereby calculated. A software protection is implemented to protect against dividing by zero (BLOCK 960). The product of the front (road) wheel angle and the absolute longitudinal velocity determined at BLOCK 930 is multiplied by the model value determined at BLOCK 960 to determine the estimated yaw rate wz(E) (BLOCK 965). The estimated yaw rate wz(E) is output (BLOCK 970).

[0097] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1. A control system for detecting a dynamic steering event of a vehicle, the control system comprising one or more processor collectively configured to: receive a first signal comprising a measured yaw parameter of the vehicle; determine an estimated yaw parameter of the vehicle; determine an absolute difference between the measured yaw parameter and the estimated yaw parameter; compare the absolute difference to a yaw parameter threshold; and output a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than the yaw parameter threshold.

2. A control system as claimed in claim 1 , wherein the control system is configured to determine the yaw parameter threshold in dependence on one or more dynamic operating parameter of the vehicle.

3. A control system as claimed in claim 2, wherein the one or more dynamic operating parameter comprise a velocity of the vehicle, the control system being configured to determine the yaw parameter threshold in dependence on the velocity of the vehicle.

4. A control system as claimed in claim 3, wherein the control system is configured to access a yaw parameter threshold map defining a relationship between the yaw parameter threshold and the velocity of the vehicle.

5. A control system as claimed in any one of the preceding claims, wherein the control system is configured to detect the dynamic steering event in dependence on a determination that the vehicle is travelling in a forward direction.

6. A control system as claimed in any one of the preceding claims, wherein the control system is configured to output the dynamic steering event signal in dependence on a determination that the absolute difference is greater than the yaw parameter threshold for at least a first time threshold.

7. A control system as claimed in any one of the preceding claims, wherein the control system is configured to halt the output of the dynamic steering event signal in dependence on a determination that the absolute difference is less than the yaw parameter threshold for at least a second time threshold.

8. A control system as claimed in any one of the preceding claims, wherein the dynamic steering event comprises or consists of a vehicle understeer event.

9. A control system as claimed in any one of the preceding claims, wherein the control system is configured to identify the dynamic steering event as a vehicle understeer event in dependence on a determination that the measured yaw parameter is less than the estimated yaw parameter; and / or the control system is configured to identify the dynamic steering event as a vehicle oversteer event in dependence on a determination that the measured yaw parameter is more than the estimated yaw parameter.

10. A control system as claimed in any one of the preceding claims, wherein the control system is configured to quantify the dynamic steering event in dependence on a magnitude of the absolute difference between the measured yaw parameter and the estimated yaw parameter.

11. A system comprising the control system of any preceding claim and a vehicle control unit for controlling at least one vehicle subsystem of the vehicle, the vehicle control unit being configured to modify the operation of the at least one vehicle subsystem in dependence on receipt of the dynamic steering event signal from the control system.

12. A system as claimed in claim 1 , wherein a plurality of vehicle subsystem control modes are defined to control operation of the at least one vehicle subsystem, the vehicle control unit being configured to determine a combined probability value of each of the vehicle subsystem control modes and to select one of the plurality of vehicle subsystem control modes in dependence on the determined combined probability values; wherein the plurality of vehicle subsystem control modes include a low-friction surface subsystem control mode, the vehicle control unit being configured to increase the combined probability value associated with the low-friction surface subsystem control mode in dependence on the receipt of the dynamic steering event signal from the control system indicating detection of a dynamic steering event.

13. A vehicle comprising the system of claim 11 or claim 12 or the control system of claims 1 to 11.

14. A method of detecting a dynamic steering event of a vehicle, the method comprising: measuring a yaw parameter of the vehicle; estimating a yaw parameter of the vehicle; determining an absolute difference between the measured yaw parameter) and the estimated yaw parameter); comparing the absolute difference to a yaw parameter threshold; and outputting a dynamic steering event signal indicating detection of a dynamic steering event in dependence on a determination that the absolute difference is greater than or equal to the yaw parameter threshold.

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

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