Speed control system and method for vehicle

Abstract

Aspects of the invention relate to a speed control system (15) for a vehicle (10), a method and a vehicle (10). The system (15) causes the vehicle (10) to drive at the target speed value. The speed control system determines when the vehicle is reaching the roof and causes a speed reduction of the vehicle when it is determined that the vehicle is reaching the roof. When it is determined that a speed of the vehicle needs to be reduced in response to a determination that the vehicle is reaching the roof, the speed control system limits a value of jerk associated with the speed reduction such that the value of jerk does not exceed the jerk limit value, the value of jerk being a rate of change in acceleration of the vehicle.

Description

Technical Field

[0001] The present disclosure relates to a control system and method for a vehicle. Aspects of the present invention relate to a speed control system for a vehicle, a system for controlling the speed of a vehicle, a vehicle, a method of controlling the speed of a vehicle, and a non-transitory computer readable storage medium.

[0002] The contents of WO 2013 / 124321 are hereby incorporated by reference. Background Art

[0003] It is known to provide speed control systems for vehicles, in particular speed control systems for causing a vehicle to operate in accordance with a target speed value. It is desirable to provide an improved speed control system to assist a driver in navigating terrain having obstacles such as a slope that must be negotiated.

[0004] In the case where the path through the front of the vehicle includes terrain with a slope crest that causes the front of the vehicle to lower, the driver may wish to reduce the speed of the vehicle as the vehicle passes over the crest. The speed reduction may help enable the driver to survey the terrain ahead of the vehicle and plan a path for the vehicle as the vehicle passes through the terrain.

[0005] It is an object of the present invention to address one or more of the disadvantages associated with the prior art. Summary of the invention

[0006] Aspects and embodiments of the present invention provide a speed control system, a system for controlling the speed of a vehicle, a vehicle and a method of controlling the speed of a vehicle as claimed in the accompanying claims.

[0007] According to one aspect of the present invention, there is provided a speed control system for a vehicle, the speed control system being configured to cause the vehicle to operate according to a target speed value, the speed control system comprising one or more controllers, the speed control system being configured to:

[0008] Determine when the vehicle is reaching the top, and

[0009] causing the speed of the vehicle to be reduced based on a determination that the vehicle is reaching a crest,

[0010] Wherein, when it is determined that a vehicle speed reduction is required in response to a determination that the vehicle is reaching a top, the speed control system is configured to limit a value of jerk associated with the speed reduction so that the value of jerk does not exceed a jerk limit value, the value of jerk being the rate of change of acceleration of the vehicle.

[0011] Embodiments of the present invention have the advantage that vehicle stability and occupant enjoyment of the vehicle may be enhanced when the vehicle speed is reduced in response to a determination that the vehicle is reaching a crest. This is achieved by limiting the value of the jerk experienced by the vehicle so that it does not exceed the jerk limit due to the speed control system causing the speed reduction as a result of reaching a crest. It will be appreciated that excessive values ​​of vehicle jerk may result in occupant discomfort and fatigue. Embodiments of the present invention mitigate these effects by limiting the maximum value of the jerk experienced by the vehicle when the system causes the speed reduction in response to a determination that the vehicle is reaching a crest.

[0012] The speed control system may be configured to receive an acceleration signal indicative of a rate of acceleration of the vehicle. The speed control system may be configured to calculate a jerk signal indicative of a rate of change of acceleration of the vehicle.

[0013] Additionally or alternatively, the speed control system may be configured to receive a jerk signal indicative of a rate of change of acceleration rate of the vehicle.

[0014] The speed control system may be configured to limit the value of the vehicle jerk by controlling an acceleration rate of the vehicle such that the jerk signal does not exceed a jerk signal limit value corresponding to the jerk limit value.

[0015] The speed control system may be an "off-road" or "off-highway" speed control system.

[0016] Optionally, the speed control system is configured to receive a driving surface grade signal indicative of the grade of a driving surface on which the vehicle is driving.

[0017] Optionally, the speed control system is configured to set the jerk limit value based at least in part on at least one vehicle parameter.

[0018] Optionally, the speed control system is configured to set the jerk limit value based at least in part on the driving surface gradient. For example, the jerk limit value may be further reduced for a lower grip driving surface such as grass, gravel or snow than for a higher grip driving surface such as asphalt or concrete.

[0019] It will be appreciated that the vehicle may continuously adjust the jerk limit value in response to changes in the driving surface grade as determined by reference to the driving surface grade signal. Thus, if the driving surface grade becomes increasingly negative as the distance traveled changes, the jerk limit value may decrease as the grade becomes more negative.

[0020] Optionally, the speed control system is configured to determine the jerk limit value at least partly in dependence on at least one vehicle parameter by means of a look-up table (LUT).

[0021] Optionally, the speed control system is configured to reduce the jerk limit value as the driving surface gradient becomes increasingly negative.

[0022] Optionally, the speed control system is configured to set the jerk limit value based at least in part on an occupant comfort parameter indicative of a desired level of occupant comfort.

[0023] The occupant comfort parameter may be set in response to user input of a desired occupant comfort via a user interface.The user interface may include one or more of a touch screen, a rotary dial, a selector button, and a voice recognition system.

[0024] Therefore, it will be appreciated that in some embodiments, the speed control system may set the jerk limit value based at least in part on both the driving surface gradient and the occupant comfort parameter. In some alternative embodiments, the jerk limit value may be set based at least in part on only one of the driving surface gradient and the occupant comfort parameter.

[0025] Optionally, the speed control system is configured to set the jerk limit value based at least in part on at least one of:

[0026] a terrain indicator parameter indicating the nature of the terrain on which the vehicle is traveling;

[0027] an occupancy parameter indicating the number of occupants of the vehicle;

[0028] a vehicle ride height parameter indicative of a selected vehicle ride height; and

[0029] A cross tracking parameter indicating the amount of cross tracking experienced by the vehicle.

[0030] The vehicle ride height parameter may be indicative of a vehicle suspension setting by which the height of the vehicle's body above a flat, level ground surface may be varied. For example, the suspension system may be an air suspension system by which the ride height may be varied by varying air pressure associated with the suspension system. For example, the suspension system may have a relatively low "entry" ride height setting, thereby allowing easy entry into the vehicle; a "highway" or "freeway" setting suitable for travel on freeways, which is higher than the entry ride height setting; and a "non-highway" setting suitable for travel under non-freeway conditions, which is higher than the freeway ride height setting.

[0031] The cross tracking parameter or value may indicate the amount of cross tracking for each pair of front and rear wheels of the vehicle.

[0032] Optionally, the cross-articulation value depends on:

[0033] a first tracking value indicating the extent to which the wheels of the first diagonal wheel pair are tracked in a positive or negative direction relative to a baseline value and the extent to which the wheels are tracking in phase with each other;

[0034] a second tracking value indicating the extent to which wheels of a second diagonal wheel pair different from the first diagonal wheel pair are being tracked in a positive or negative direction relative to the baseline value and the extent to which the wheels are tracking in phase with each other; and

[0035] The first tracking value and the second tracking value correspond to the extent to which the respective pairs move in anti-phase with respect to each other.

[0036] The baseline or reference value may correspond to a position midway between the upper and lower ends of travel of the suspension for a given wheel.

[0037] Optionally, the speed control system can be configured to receive wheel tracking signals S_FL, S_FR, S_RL, S_RR, wherein S_FL is a signal indicating the left front suspension height FL, S_FR is a signal indicating the right front suspension height FR, S_RL is a signal indicating the left rear suspension height RL, and S_RR is a signal indicating the right rear suspension height RR.

[0038] Optionally, the cross tracking value CrossArtc_L is calculated according to the following formula:

[0039] CrossArtc_L=abs(FL-FR)+abs(RL-RR)+abs(FL-RL)+abs(FR-RR)-abs(FL-RR)-abs(FR-RL)

[0040] Wherein FL is the left front suspension height, FR is the right front suspension height, RL is the left rear suspension height, and RR is the right rear suspension height.

[0041] It will be appreciated that if the vehicle is travelling over certain types of terrain, the speed control system may set the jerk limit value according to the nature of the terrain as indicated by the terrain indicator parameter. For terrain that is expected to be particularly uncomfortable to traverse, such as rocky terrain, the jerk limit value may be set to a higher value. It will be appreciated that a user may anticipate a greater amount of jerk when traversing certain types of terrain, and may therefore be prepared to experience a greater amount of jerk.

[0042] In some implementations, other means for determining the jerk limit value may be useful.

[0043] Optionally, the speed control system is further configured to receive a pitch rate signal indicating a rate of change of the pitch attitude of the vehicle, and the speed control system is configured to determine that the vehicle is reaching the top when the pitch rate information signal indicates that the change in the pitch attitude of the vehicle exceeds a predetermined rate value in a direction corresponding to a decrease in the pitch attitude, and the slope signal indicates that the slope value of the driving surface is lower than a limit value.

[0044] It will be appreciated that in some embodiments, a positive slope value corresponds to an uphill slope, and a negative slope value corresponds to a downhill slope.

[0045] Optionally, the speed control system is configured to cause a reduction in speed upon determining that the vehicle is reaching a crest by at least one of:

[0046] application of braking torque by means of a vehicle braking system; and

[0047] The amount of positive drive torque applied to one or more wheels of the vehicle is reduced.

[0048] In a further aspect of the invention, there is provided a system for controlling the speed of a vehicle, the system comprising:

[0049] A speed control system according to the previous aspect; and

[0050] One or more sensors configured to output information indicative of vehicle jerkiness.

[0051] In some embodiments, the one or more sensors may include an accelerometer or a gyroscope. Other suitable sensors are known to the skilled person and may be used in embodiments of the invention.

[0052] It will be appreciated that, by way of example, vehicle jerk may be determined by reference to a signal indicative of vehicle speed (e.g., by calculating the double differential of speed) or a signal indicative of vehicle acceleration (e.g., by calculating the rate of change of acceleration from the acceleration signal).

[0053] In yet another further aspect of the invention there is provided a vehicle comprising a speed control system according to the previous aspect or a system of the previous aspect.

[0054] In another aspect of the present invention, a method for controlling the speed of a vehicle implemented by a speed control system is provided, the method comprising:

[0055] causing the vehicle to operate according to the target speed value; and

[0056] Determine when the vehicle reaches the top,

[0057] The method includes causing a reduction in the speed of the vehicle when it is determined that the vehicle is reaching a crest,

[0058] Thus, when it is determined that a reduction in vehicle speed is required in response to a determination that the vehicle is reaching a crest, the method includes limiting a jerk value associated with the reduction in speed, the jerk value providing an indication of the rate of change of acceleration of the vehicle such that the jerk value does not exceed a jerk limit value.

[0059] Optionally, the method comprises setting the jerk limit value based at least in part on at least one vehicle parameter.

[0060] In yet another aspect of the present invention, a non-transitory computer-readable storage medium is provided having stored thereon instructions which, when executed by one or more electronic processors, cause the one or more electronic processors to perform the method of the previous aspect.

[0061] It is expressly intended that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular individual features thereof, may be employed independently or in any combination within the scope of the present application. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, unless such features are incompatible. Applicants reserve the right to change any originally filed claim or to file any new claim accordingly, including the right to amend any originally filed claim to be subordinate to any other claim and / or to incorporate any features of any other claim, even though protection was not originally claimed in this manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0063] Figure 1 A schematic diagram showing a vehicle having a speed control system according to an embodiment of the present invention is shown;

[0064] Figure 2 A schematic diagram showing a steering wheel of a vehicle having a speed control system according to an embodiment of the present invention;

[0065] Figure 3 A schematic diagram showing a speed control system according to an embodiment of the present invention;

[0066] Figure 4 A vehicle according to an embodiment of the present invention is shown going up a slope towards the top of the slope;

[0067] Figure 5A vehicle according to an embodiment of the present invention is shown going up a slope towards another top of a slope;

[0068] Figure 6 A vehicle according to an embodiment of the present invention is shown crossing a horizontal running surface towards a further hill crest;

[0069] Figure 7 The vehicle according to the embodiment of the present invention is shown going up the slope toward the top of the slope, and there is another top of the slope after passing the top of the slope;

[0070] Figure 8 is a graph of the target top-of-the-peak acceleration determined by the speed control system as a function of the grade of the driving surface and the comfort parameter setting;

[0071] Fig. 9 is a flow chart showing the operation of the speed control system to reduce jerk when a hill top is detected;

[0072] Fig.10 is a flow chart further illustrating the operation of the speed control system to mitigate jerk once the crest event is complete; and

[0073] Fig.11 is a schematic diagram of an electronic controller consisting of a vehicle control unit (VCU) and configured to implement a speed control system of the VCU. DETAILED DESCRIPTION

[0074] The contents of WO 2013 / 124321 are hereby incorporated by reference.

[0075] Figure 11 is a schematic diagram of a vehicle 10 according to an embodiment of the present invention. The vehicle 10 has a prime mover or motor 11 in the form of an internal combustion engine. The engine 11 is coupled to a transmission 12 by means of a coupling device 13. The coupling device 13 is arranged to allow the transmission 12 to gradually reach a speed compatible with the motor speed when the vehicle 10 accelerates from a standstill. The coupling device 13 is typically a friction clutch, a torque converter, etc. The transmission 12 is arranged to drive a pair of rear wheels 10RW and, in addition, optionally a pair of steerable front wheels 10FW. An accelerator pedal 1 allows the driver to control the amount of torque generated by the motor 11 under the control of a powertrain controller 17, while a brake pedal 2 allows the driver to apply the braking system under the control of a brake controller 16. A driving mode selector 19 is provided, by means of which the driver can select a road driving mode or one of a plurality of off-road driving modes, the plurality of off-road driving modes including a grass / gravel / snow (GGS) driving mode, a sand (S) driving mode, and a mud and rut (MR) driving mode. In some embodiments, the selector also allows selection of an "auto response mode" in which the vehicle 10 automatically determines the best driving mode at any given moment. The driving mode may be referred to as a "terrain response" (or "TR") mode.

[0076] The vehicle 10 has a vehicle control unit (VCU) 15 which is operable to implement a low speed vehicle speed control function or system. The low speed vehicle speed control function may also be referred to as an "off-road" or "non-highway" cruise control function or system. The low speed vehicle speed control function is operable if the vehicle speed VREF does not exceed a predetermined maximum speed. In the present embodiment, the predetermined maximum speed is 30 km / h. Above 30 km / h, the VCU 15 is operable to implement a higher speed speed control function or system. The VCU 15 may be described as implementing a low speed speed control system or a higher speed speed control system. Both the low speed speed control system and the higher speed speed control system functions are controlled by a user via input controls mounted to a steering wheel 171 of the vehicle 10. In Figure 2 171 is shown in more detail in . It will be appreciated that a low speed vehicle speed control function or system may be useful when driving in non-highway driving conditions, while a higher speed speed control function or system may be useful when driving in highway driving conditions (e.g., on a relatively smooth, dry asphalt or concrete driving surface).

[0077] The input controls include a "set speed" control 173, actuation of which sets the value of the parameter driver_set_speed to be substantially equal to the current vehicle speed. Pressing the "+" (or "plus") button 174 allows the set speed to be increased, while pressing the "-" (or "minus") button 175 allows the set speed to be decreased. In some embodiments, the speed control function is activated when the "+" button 174 is pressed while the speed control function is in an inactive state.

[0078] In the present embodiment, the VCU 15 is configured to implement an active speed control system (or "active cruise control") when a higher speed speed control system is operating. The active speed control system is configured to keep the vehicle 10 behind the vehicle in front at a predetermined distance in certain circumstances, as will be explained. The steering wheel 171 also has a pair of following distance control buttons 178, 179 for setting the value of the parameter distance_following, which is the distance that the driver expects the vehicle 10 to keep behind the vehicle in front. The VCU 15 is operable to control the vehicle 10 to keep a certain distance behind the vehicle in front, which is substantially equal to the distance represented by the parameter distance_following. The first button 178 of the buttons is operable to increase the value of the parameter distance_following, and thus increase the distance between the vehicle 10 and the vehicle in front, while the second button 179 of the buttons is operable to reduce the value of the parameter distance_following. The vehicle 10 has a radar module 5, which is mounted to the front of the vehicle and is arranged to project a radar beam in the front direction of the vehicle 10. The module 5 is arranged to detect radiation reflected by the preceding vehicle and to determine the distance of the preceding vehicle from the vehicle 10 (as the "host" vehicle). The module 5 is provided with a signal indicative of the current speed of the host vehicle 10. From this signal and data on the distance of the preceding vehicle from the host vehicle 10 over time, the module 5 is able to calculate the speed of the preceding vehicle. Other arrangements for determining the distance to the preceding vehicle and the speed of the preceding vehicle are also useful. In some embodiments, no active speed control functionality is provided and the following distance control buttons 178, 179 are omitted. In some embodiments, the radar module 5 is omitted.

[0079] Higher speed speed control systems are not the subject of the present application. Unless otherwise stated, the remainder of this specification relates to low speed speed control systems.

[0080] When the low speed control system is activated, the VCU 15 controls the speed of the vehicle 10 according to a target speed value, which is set to be substantially equal to the set speed selected by the driver, driver_set_speed, or a lower value (if this is desired), as described in more detail below. The VCU 15 achieves this by calculating the maximum allowed speed max_set_speed of the vehicle 10 at a given moment. Unless a lower value is desired, the VCU 15 sets the value of max_set_speed to the value of the driver set speed driver_set_speed, as described in more detail below. The VCU 15 controls the speed of the vehicle 10 according to max_set_speed as the target speed value of the vehicle by making the vehicle speed VREF equal to the value of max_set_speed.

[0081] The VCU 15 then outputs the acceleration target value acc_tgt at a given time to the powertrain controller 17 and the brake controller 16 so as to maintain the vehicle speed determined by referring to the vehicle reference speed VREF at a desired value. If the driver overrides the speed control system and VREF exceeds 30 km / h, the speed control system suspends operation until VREF drops to 30 km / h or less.

[0082] The driver can set the value of driver_set_speed of the low-speed speed control system to the current vehicle speed VREF (assuming VREF does not exceed 30km / h) by pressing the "set speed" control 173 while the vehicle 10 is moving. When the VCU 15 detects that the "set speed" control 173 is pressed, the VCU 15 captures a snapshot of the current speed VREF of the vehicle 10 and sets the value of driver_set_speed to correspond to the current speed. (It should be understood that if VREF exceeds 30km / h and the set speed control 173 is pressed, a higher speed speed control system is activated. In the present embodiment, if a higher speed speed control system is activated because the value of driver_set_speed has been set to a value exceeding 30km / h, the low-speed speed control system will not automatically reactivate once the speed drops below 30km / h).

[0083] As described above, when the vehicle 10 is traveling along a highway and the higher speed speed control system is active, i.e. VREF and driver_set_speed exceed the minimum allowed set speed set_speed_min (30 km / h in this embodiment), the VCU 15 is operable to allow the user to command the VCU 15 to maintain the current vehicle speed by pressing the set speed control 173. In the absence of vehicles on the road ahead of the vehicle 10 or other factors requiring a lower speed (see below), the VCU 15 controls the speed VREF of the vehicle 10 to maintain VREF substantially equal to the set speed value driver_set_speed.

[0084] In this embodiment, if the VCU 15 (by means of the radar module 5) detects the presence of a leading vehicle in front of the vehicle 10, the VCU 15 is operable to reduce the speed of the host vehicle 10 according to the speed of the leading vehicle so as to maintain a distance of no less than a prescribed distance behind the leading vehicle. The prescribed distance may be set by the driver by means of the "following distance" control buttons 178, 179 as described above. This function is only available when the higher speed speed control system is activated.

[0085] The vehicle 10 has a human-machine interface (HMI) in the form of a touch screen 18, by means of which the VCU 15 can communicate with the user. As described above, when the low speed control system is in an activated state, the VCU 15 is operable to calculate the maximum permissible value max_set_speed of the set speed according to the terrain on which the vehicle is traveling. Therefore, the VCU 15 is operable to limit the maximum speed at which it controls the operation of the vehicle 10 according to the terrain. Embodiments of the present invention allow for improved vehicle stability with reduced driver intervention when operating under non-highway conditions. That is, because the VCU 15 determines the maximum permissible value max_set_speed of the set speed and limits the set speed accordingly, the driver does not need to intervene to reduce the value of the vehicle set speed when the main terrain is necessary, and increase the set speed when the main terrain allows.

[0086] Figure 3 1 shows how the VCU 15 determines the value of max_set_speed. The VCU 15 includes a "maximum set speed calculation" section (or "engine") 15a, a "reach top acceleration requirement calculation" section (or "engine") 15b, and a "vehicle acceleration calculation" section (or "engine") 15c. In addition, the input to the "maximum set speed calculation" section (or "engine") 15a includes a "lateral acceleration limit calculation" section 15d.

[0087] The "vehicle acceleration calculation" portion 15c is configured to calculate the desired acceleration value acc_tgt of the vehicle 10 at a given moment based on received inputs, including inputs from the "maximum set speed calculation" portion 15a and the "reaching top acceleration requirement calculation" portion 15b. As described above, the "vehicle acceleration calculation" portion 15c outputs the desired acceleration value acc_tgt at a given moment, optionally as a speed reduction signal, to the powertrain controller 17 and the brake controller 16, which attempt to make the actual vehicle acceleration equal to acc_tgt as quickly as possible within any given comfort limit. The brake controller or powertrain controller can change the speed by applying brakes or braking torque to the wheels of the vehicle by means of the vehicle braking system. Alternatively or additionally, the reduction in the acceleration or speed of the vehicle can be performed by reducing the amount of positive drive torque applied to one or more wheels of the vehicle. The VCU 15 controls the rate of acceleration (positive or negative) at a given moment by causing the value of acc_tgt output by the "Vehicle Acceleration Calculation" section 15c to change at a desired rate of change. Figure 3 In some embodiments of the embodiments of the present invention, the "vehicle acceleration calculation" part 15c receives the value of the comfort parameter COMFORT indicative of the level of comfort required by the vehicle occupants, as described in more detail below. The "vehicle acceleration calculation" part 15c then adjusts the maximum allowable rate of change of acceleration (or "jerk") at a given moment in time based on the value of the comfort parameter to enable control of occupant comfort. Therefore, for the higher level of occupant comfort required, the "vehicle acceleration calculation" part 15c reduces the maximum allowable value of jerk so as to improve occupant comfort. Therefore, when a change in vehicle acceleration is required, the "vehicle acceleration calculation" part 15c limits the rate of change of acceleration so as to improve occupant comfort. The maximum allowable amount of jerk may also be referred to as a "jerk limit value."

[0088] The "maximum set speed calculation" portion 15a of the VCU 15 is configured to receive inputs corresponding to a plurality of vehicle parameters in addition to the current value of driver_set_speed. As described above, the "maximum set speed calculation" portion 15a outputs a value of max_set_speed that is no greater than the value of driver_set_speed, but may be lower if the "maximum set speed calculation" portion 15a determines that the driving conditions require it, as described in more detail below. The parameters are: (a) a current vehicle reference value of the coefficient of surface friction μmeas, which is a value calculated by the VCU 15 based on the value of one or more parameters (e.g., the amount of torque applied to the wheel causing excessive wheel slip); (b) an expected value of the coefficient of surface friction μTRmode corresponding to the currently selected vehicle driving mode, which is a prescribed value for each driving mode; (c) a current value of the steering angle “STEERING ANGLE, δ”, which corresponds to the steerable wheel angle or the steering wheel position in some embodiments; (d) a current yaw rate “YAW RATE” of the vehicle (determined by the output of a reference accelerometer); (e) a current measured value of the lateral acceleration “MEASURED LAT.ACC.” (also determined by the output of a reference accelerometer); (f) a current measured value of the surface roughness “SURFACE ROUGHNESS” (determined by reference to suspension tracking). In some embodiments, the VCU 15 may also receive (g) a signal "GPS LOCATION" indicating the current location of the vehicle (determined by reference to a global satellite positioning system (GPS) output or other global navigation satellite system or other positioning system); and / or (h) information "CAMERA" obtained with the aid of a camera system. The information obtained with the aid of a camera system or an imaging system may include, for example, an alarm in the event that it is determined that the vehicle 10 may be about to leave an off-road lane or track.

[0089] The "lateral acceleration limit calculation" section 15d of the VCU 15 is configured to determine the maximum permissible lateral acceleration rate max_lat_acc of the vehicle 10 during the driving process based on the reference value of the surface friction coefficient μmeas and the expected value of the surface friction coefficient μTRmode. The VCU 15 uses the value of max_lat_acc to limit the value of max_set_speed when the vehicle is turning to prevent understeering.

[0090] In the present embodiment, the "maximum set speed calculation" portion 15a of the VCU 15 is also operable to calculate the radius of curvature of the path of the vehicle 10 on the terrain based on the steering angle. The VCU 15 compares this radius of curvature with the vehicle yaw rate and the measured lateral acceleration. If the VCU 15 detects that understeer is present, the VCU 15 is operable to reduce the value of max_set_speed accordingly. In some embodiments where a signal indicative of the current position of the vehicle is received, the VCU 15 may also take into account the path of travel of the vehicle determined by the reference position signal to improve the reliability of the determination of the amount of understeer (if any) present.

[0091] In some embodiments, yaw rate and measured lateral acceleration are not used to determine the amount of understeer present. Other arrangements may also be used.

[0092] The "maximum set speed calculation" section 15a of the VCU 15 also determines the value of max_set_speed according to the value of the surface roughness of the terrain on which the vehicle 10 is traveling. The value of max_set_speed may decrease as the surface roughness increases.

[0093] In the present embodiment, the top-reaching acceleration demand calculation section 15b of the VCU 15 also receives a driving surface gradient signal indicating the gradient of the driving surface on which the vehicle 10 is traveling and a pitch rate signal indicating the rate of change of the pitch of the vehicle 10. The top-reaching acceleration demand calculation section 15b of the VCU 15 is configured to generate a value tgt_crest_acc of the desired acceleration rate of the vehicle 10 at a given moment. The top-reaching acceleration demand calculation section 15b outputs an acceleration demand signal acc_demand to the vehicle acceleration calculation section 15c to accelerate the vehicle 10 at the desired rate value tgt_crest_acc.

[0094] If the reaching top acceleration demand calculation part 15b determines that the vehicle has not reached the top, the value of the parameter acc_demand is set to correspond to the maximum allowable value Amax of the vehicle acceleration. This is to make the vehicle acceleration calculation part 15c not respond to the signal acc_demand but only respond to the signal max_set_speed received from the maximum set speed calculation part 15a to reduce the vehicle speed.

[0095] If the reaching top acceleration demand calculation part 15b determines that the vehicle is reaching the top, the value of the parameter acc_demand is set to correspond to the desired acceleration rate tgt_crest_acc. The reaching top acceleration demand calculation part 15b of the VCU 15 is configured to determine whether the vehicle is reaching the top based on the driving surface gradient signal ("GRADIENT") and the pitch rate signal ("PITCH RATE"). It should be understood that in order to reduce the vehicle speed when it is determined that the vehicle is reaching the top, the value of the acceleration rate acc_demand will correspond to a negative acceleration rate.

[0096] Specifically, the reaching-the-top acceleration requirement calculation section 15b of the VCU 15 is configured to determine that the vehicle is reaching the top when the following conditions are met:

[0097] (a) the rate of change of the pitch of the vehicle as determined by reference to the pitch rate signal exceeds a predetermined value for a predetermined period of time; and

[0098] (b) The value of the slope of the running surface as determined by referring to the running surface slope signal is lower than a predetermined value.

[0099] The grade value of the driving surface may be referred to herein as the driving surface grade value.

[0100] In the present embodiment, the predetermined value of the rate of change of the pitch of the vehicle is 5 degrees per second, the predetermined period is 1 second, and the predetermined slope value of the driving surface is +5%. Therefore, it should be understood that in order for the VCU 15 to determine that the vehicle is reaching the top, the driving surface slope must be less than the value of +5% ((is an uphill slope), that is, the driving surface must have a slope less than 5% uphill slope). It should be understood that, for example, if the driving surface slope is +4%, substantially zero (corresponding to a horizontal surface) or negative (corresponding to a downhill slope), the driving surface slope condition will be met. In some embodiments, other predetermined values ​​of the rate of change of pitch, the predetermined period, and the predetermined slope may be useful.

[0101] As described above, it should be understood that when the top-reaching acceleration demand calculation section 15b of the VCU 15 determines that the vehicle has not reached the top, the section 15b outputs a value of acc_demand corresponding to the maximum allowable value Amax of the acceleration rate of the vehicle. This is to allow the vehicle acceleration calculation section 15c to ignore the acc_demand signal and support the max_set_speed signal received from the maximum set speed calculation section 15a of the VCU 15.

[0102] In some embodiments, when the VCU 15 determines that the conditions for determining that the vehicle is reaching the top are met, the VCU 15 sets the value of acc_demand to a fixed predetermined value corresponding to a negative acceleration (i.e., a deceleration rate) so as to cause the vehicle acceleration calculation portion 15c to apply a deceleration rate to the vehicle 10. It should be understood that in response to the demand for a negative acceleration rate for the vehicle 10 received from the "reaching the top acceleration demand calculation" portion 15b, the vehicle acceleration calculation portion 15c of the VCU 15 causes the value of the vehicle speed VREF to decrease at a rate value corresponding to the requested deceleration rate acc_demand.

[0103] In some embodiments, acc_demand is output as a speed reduction signal operable to reduce or replace max_set_speed or driver_set_speed. The speed reduction signal may be output to another vehicle system, such as a powertrain controller or control system or a brake controller or brake controller or control system, to reduce the speed of the vehicle while recognizing reaching a top.

[0104] In this embodiment, the value of acc_demand itself depends on at least one parameter. In this embodiment, when the VCU 15 determines that the conditions for determining that the vehicle is reaching the crest are met, the "reaching crest acceleration demand" calculation part 15b of the VCU 15 calculates the value of tgt_crest_acc that depends on the following parameters:

[0105] (1) The current value of the driving surface slope, the value of tgt_crest_acc becomes increasingly negative (corresponding to increasingly higher deceleration rates) as the driving surface slope becomes increasingly negative;

[0106] (2) the driving mode in which the vehicle is currently operating (TR mode); and

[0107] (3) The value of the comfort parameter "COMFORT" (indicative of the desired comfort level of the vehicle occupants), the value of tgt_crest_acc becomes increasingly negative (corresponding to increasingly higher deceleration rates) as the desired comfort level increases. Thus, as the desired comfort level increases, the reduction in speed of the vehicle 10 during the period of applied deceleration will become greater.

[0108] It will be appreciated that the value of tgt_crest_acc may be set according to an empirically determined lookup table (LUT) in accordance with the driving mode. In the present embodiment, when the selected driving mode (TRmode) is the sand mode, in response to a determination that the vehicle is reaching the top, no reduction in vehicle speed is caused, whereas a reduction is caused in all other driving modes (e.g., the GGS driving mode and the highway driving mode). In the present embodiment, for a given set of conditions including the VREF value, the rate of change of the slope and the pitch, the values ​​of tgt_crest_acc calculated in driving modes other than the sand mode are substantially the same. In some alternative embodiments, for a given set of conditions, the values ​​of tgt_crest_acc calculated by the reaching-top acceleration demand calculation portion 15b in at least two driving modes other than the sand mode may be different.

[0109] In the present embodiment, the VCU 15 is configured to receive inputs indicating a desired level of occupant comfort via the touch screen 18, although other input devices (e.g., a rotary dial) may also be useful. In the present embodiment, the comfort signal indicates whether the comfort setting has a value of 0 (zero), 1, 2, 3, or 4. A value of zero is considered to correspond to an "off" condition of the comfort setting, indicating that passenger comfort is not considered when setting the value of tgt_crest_acc. In the present embodiment, the VCU determines the value of tgt_crest_acc based on the slope of the driving surface, and then increases the value of tgt_crest_acc by a certain factor, which makes the value of the comfort setting higher and the value of the vehicle speed gradually decrease. The input indicating the desired level of occupant comfort described in the present embodiment is user-selectable, and therefore can be referred to as a user-selectable input, which indicates the desired level of occupant comfort or the desired value of an occupant comfort parameter or a comfort parameter or the desired level of occupant comfort or the value of a comfort parameter, or indicates the desired comfort level of the vehicle occupant.

[0110] It will be appreciated that in some embodiments, the vehicle 10 is not provided with the capability to allow the driver to input desired values ​​for occupant comfort parameters.

[0111] It should be understood that in this embodiment, the VCU 15 is configured to not allow the value of max_set_speed to drop below a predetermined minimum value to avoid inconvenience to the user. Therefore, if the vehicle speed VREF reaches the predetermined minimum allowed value, the vehicle acceleration calculation part 15c does not attempt to reduce the vehicle speed in response to the negative acceleration demand from the top acceleration demand calculation part 15b. In this embodiment, the predetermined minimum value is 2km / h. In some embodiments, other values ​​may be useful.

[0112] As described above, in the present embodiment, the VCU 15 is configured to determine that the vehicle is reaching the crest when the above-mentioned crest conditions (a) and (b) are satisfied, and calculate the value of tgt_crest_acc based on the above-mentioned parameters (1)-(3).

[0113] As described above, in the present embodiment, the VCU 15 calculates the value of the parameter tgt_crest_acc, and causes the "vehicle acceleration calculation" section 15c to apply an acceleration rate corresponding to the value of tgt_crest_acc to the vehicle 10. In the present embodiment, after determining that the vehicle is reaching the top, the acceleration rate is applied for a predetermined period of time (referred to as a predetermined speed reduction period). The predetermined speed reduction period is 2s in the present embodiment, but may be any other suitable time period in some embodiments, such as 1s, 5s, 10s, or any other suitable value.

[0114] In an alternative embodiment, after determining that the vehicle is reaching the top, the VCU 15 can calculate the value of the parameter tgt_crest_acc, and cause the "vehicle acceleration calculation" section 15c to apply an acceleration rate corresponding to the value of tgt_crest_acc to the vehicle 10 for a predetermined distance (referred to as a predetermined speed reduction distance). The predetermined speed reduction distance can be any suitable distance, such as a single wheelbase, double wheelbase, triple wheelbase, or any suitable distance. It should be understood that the distance does not have to be an entire wheelbase or multiple entire wheelbases to be considered a suitable distance. It should be understood that the wheelbase means the center-to-center distance from the front wheels of the vehicle to the rear wheels of the vehicle in a direction parallel to the longitudinal axis of the vehicle.

[0115] Figure 4 The vehicle 10 is shown ascending a slope toward a crest C, after which the driving surface is substantially flat (horizontal). As the vehicle 10 passes through the crest C, the VCU 15 detects a decrease in the slope of the driving surface and a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). If the rate of change of pitch exceeds a predetermined value of 5 degrees per second, and the slope of the driving surface is less than a 5% (uphill) slope (i.e., the slope is less steep than 5%, is horizontal, or is a downhill slope), the VCU 15 determines that the vehicle 10 is reaching the crest and begins calculating the value of tgt_crest_acc based on the above parameters (1)-(3).

[0116] Figure 5The vehicle 10 is shown ascending a slope toward a crest C, beyond which the driving surface has a negative (downhill) gradient. As the vehicle 10 passes through the crest C, the VCU 15 detects a decrease in the gradient of the driving surface and a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). If the rate of change of pitch exceeds a predetermined value of 5 degrees per second, and the gradient of the driving surface is less than a 5% (uphill) gradient (i.e., the gradient is less steep than 5%, is horizontal, or is a downhill gradient), the VCU 15 determines that the vehicle 10 is reaching the crest and begins calculating the value of tgt_crest_acc based on the above parameters (1)-(3).

[0117] Figure 6 The path of the vehicle 10 is shown as it passes through a substantially horizontal driving surface (i.e., having a substantially 0% slope) toward a hill crest C, after which the driving surface has a negative (downhill) slope. Thus, the reaching-crest condition (b) is satisfied: the slope value of the driving surface as determined by reference to the driving surface slope signal is equal to or less than 5%. As the vehicle 10 passes through the hill crest C, the VCU 15 detects a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). If the rate of change of pitch exceeds a predetermined value of 5 degrees per second, the VCU 15 determines that the reaching-crest condition (a) is satisfied and the vehicle 10 is therefore reaching the crest. The VCU 15 then begins to calculate the value of tgt_crest_accin based on the above parameters (1)-(3).

[0118] In this embodiment, when the VCU 15 calculates the value of tgt_crest_acc in response to a first determination that the vehicle is reaching the crest, the VCU 15 will not subsequently apply further deceleration in response to a second subsequent determination that the vehicle is reaching the crest unless the second determination occurs within a predetermined crest detection period after the first determination that the vehicle is reaching the crest.

[0119] In some embodiments, the predetermined hill top detection period corresponds to substantially twice the predetermined speed reduction period. In some embodiments, other multiples may be useful.

[0120] In the present embodiment, the predetermined hill top detection period is a period of 4 s, which is twice the predetermined speed reduction period of 2 s, but in some embodiments may be any other suitable time period, such as 5 s, 10 s or any other suitable value.

[0121] In an alternative embodiment, when the VCU 15 calculates the value of acc_demand in response to a first determination that the vehicle is reaching the crest, the VCU 15 will not subsequently apply further deceleration in response to a second subsequent determination that the vehicle is reaching the crest unless the second determination occurs a predetermined crest detection period after the first determination that the vehicle is reaching the crest. The predetermined crest detection distance may be any suitable distance, such as a single wheelbase, double wheelbase, triple wheelbase, quadruple wheelbase, or any suitable distance.

[0122] In some embodiments, the predetermined crest detection distance corresponds to substantially twice the predetermined speed reduction distance. In some embodiments, other multiples may be useful.

[0123] In one embodiment, the predetermined speed reduction distance corresponds substantially to two times the wheelbase of the vehicle and the predetermined hill top detection distance corresponds substantially to four times the wheelbase.

[0124] Figure 7 The path of the vehicle 10 over two crests spaced a relatively short distance apart is shown. The vehicle 10 is shown climbing a hill toward the first crest C1. When the vehicle passes the crest C1, the condition for the VCU 15 to determine that the vehicle 10 is reaching the top is satisfied at position X1. Therefore, the VCU 15 calculates the value of the acceleration tgt_crest_acc to be applied to the vehicle when the vehicle passes the crest.

[0125] After passing through position X1, the VCU 15 starts the timer. The VCU 15 continues to calculate the value of tgt_crest_acc based on the values ​​of the parameters (a) to (c) described above. After the predetermined speed reduction period has passed (2s in the present embodiment), the vehicle 10 terminates the calculation of the value of tgt_crest_acc based on the values ​​of the parameters (a) to (c) described above, and sets the value acc_demand to the maximum allowable value Amax of the vehicle acceleration as described above. Therefore, the vehicle acceleration calculation part 15c ignores the received value of acc_demand when determining the vehicle speed, and restores the vehicle speed to the lower value of the current value of the driver set speed and the main value of max_set_speed.

[0126] Further references Figure 7, position X2 is the position of the vehicle 10 at which conditions (a) to (c) are again satisfied for the VCU 15 to make a second determination that the vehicle is reaching the top. However, if the time taken to travel from position X1 to position X2 is less than the predetermined crest detection period after the first determination that the vehicle has reached the top at position X1, which is 4s in this embodiment, the VCU 15 ignores the fact that reaching the top has been detected. However, if the predetermined crest detection period has expired when the vehicle reaches position X2, the VCU 15 responds in the manner described above with respect to the vehicle reaching position X1. That is, the VCU 15 starts a timer and applies deceleration to the vehicle by calculating the value of tgt_crest_acc based on the values ​​of parameters (a) to (c).

[0127] Figure 8 The VCU 15 determines the values ​​of tgt_crest_acc and acc_demand. Figure 8 , the horizontal axis is surface grade, where 0% represents a zero grade condition ("0% flat road"). On the horizontal axis, the road grade increases in an uphill direction as one moves to the left of the 0% flat road condition, and the surface grade increases in a downhill direction as one moves to the right of the 0% flat road condition.

[0128] As described above, when the VCU 15 determines that the vehicle has not reached the top, the value of the parameter acc_demand output from the reaching-top acceleration demand calculation section 15b is set to the maximum permissible value Amax. Therefore, the vehicle acceleration calculation section 15c does not cause a decrease in the value of acc_tgt in response to the reception of the signal acc_demand. Instead, the speed is controlled according to the value of max_set_speed received from the maximum set speed calculation section 15a.

[0129] As mentioned above, it will be appreciated that the speed control system implemented by the VCU 15 is configured so that the vehicle acceleration calculation portion 15c cannot cause the vehicle speed to drop below a predetermined minimum value. In this embodiment, the predetermined minimum value is 2km / h, but other values ​​may be useful in some embodiments.

[0130] In the case where the reaching top condition is met, the VCU 15 calculates the value of tgt_crest_acc as described above, and also Figure 8 Shown in.

[0131] like Figure 8 It can be seen that the value of tgt_crest_acc is set to an increasingly negative value (corresponding to increasingly severe vehicle deceleration) according to the value of the comfort parameter. Figure 8As shown by trace "A" in FIG. 1 , when the value of the comfort parameter is zero (corresponding to the "off" condition) or the value is "1", once the slope reaches a value of 2% in the downhill direction (i.e., the slope is negative 2% or "-2%"), the value of tgt_crest_acc changes from Amax to increasingly negative values. These conditions are determined by Figure 8 The mark in is indicated by a line “comfort=0,1”.

[0132] In the case of the value "2" of the comfort parameter, the value of acc_demand changes from Amax to the value of tgt_crest_acc, which corresponds to increasingly negative values ​​of acceleration once the slope reaches the value of 0%. This situation is caused by Figure 8 The trajectory “B” in and the line marked “comfort=2” are represented.

[0133] In the case where the value of the comfort parameter is "3" or "4", once the slope drops below the value of +5%, the value of tgt_crest_acc corresponds to increasingly negative values. In the case where the comfort parameter has a value of "4", the value of the rate of increase of tgt_crest_acc in the negative direction is more drastic, that is, the slope in the graph of tgt_crest_acc versus slope is steeper, resulting in a greater speed reduction than in the case where the comfort parameter has a value of "3" or less. This condition is caused by Figure 8 The trajectory “C” in the figure and the lines marked “Comfort = 3” or “Comfort = 4” are indicated.

[0134] In the present embodiment, in a case where the comfort parameter is set to a value of "4" (4 being the highest required value for occupant comfort), the VCU 15 is configured to determine that the vehicle is reaching the top when the pitch rate in the downward direction is at a lower value than in a case of a lower value of the comfort parameter. This condition is determined by Figure 8 , marked with "Comfort = 4". In this embodiment, when the comfort parameter is set to a value of "4", in addition to the slope being less than 5%, the VCU 15 is also configured to require a pitch rate exceeding a value of 3 degrees per second in order to determine that the vehicle is reaching the top. In some embodiments, other values ​​of the pitch rate may be useful, such as 2 degrees per second, 2.5 degrees per second, 4 degrees per second, or any other suitable value. Other values ​​of the slope may also be useful in some embodiments.

[0135] It will be appreciated that when the value of the comfort parameter has other values, such as when the value is 1, 2 or 3, different values ​​of the pitch rate may be required before reaching the top is determined.

[0136] As mentioned above, the "reach top acceleration demand calculation" portion 15b receives the value of the comfort parameter and determines the value of tgt_crest_acc based in part on the comfort parameter. In some embodiments, the "reach top acceleration demand calculation" portion 15b also adjusts the value of the rate at which the vehicle takes the desired acceleration rate tgt_crest_acc based on the value of the comfort parameter so as to limit the maximum value of the jerk experienced at a given moment. For a higher level of required occupant comfort, the maximum allowed value of jerk (i.e., the jerk limit value) is lower.

[0137] Fig. 9 shows a way to limit the value of jerk when a change in acceleration demand is made after detection of reaching the top. That is, Fig. 9 The operation of the jerk relief function of the "reach-top acceleration requirement calculation" section 15b when the top of a slope is detected is shown.

[0138] At step S101, the "reaching top acceleration requirement calculation" part 15b determines whether the top of the slope is detected. If the top of the slope is not detected, step S101 is repeated. If the top of the slope is detected, the method continues at step S103.

[0139] At step S103, the "reaching the top acceleration demand calculation" section 15b calculates a target value tgt_crest_acc of acceleration in response to the determination that the vehicle is reaching the top. The value of tgt_crest_acc is calculated based on the values ​​of the driving surface gradient, the driving mode, and the comfort parameter. The value of tgt_crest_acc is used to calculate the value of the desired acceleration rate acc_demand of the vehicle 10 at a given moment. The value of acc_demand is calculated based on the value of tgt_crest_acc so as to limit the maximum value of the jerk so that the maximum value of the jerk does not exceed the jerk limit value.

[0140] At step S105, the "reaching top acceleration requirement calculation" part 15b determines whether the current value of acc_tgt output by the "vehicle acceleration calculation" part 15c is less than zero meters per second squared. If the value of acc_tgt is less than zero, the method continues at step S107, otherwise the method continues at step S109.

[0141] At step S107, the "reach-top acceleration demand calculation" portion 15b sets the value of the signal acc_demand to the current value of acc_tgt output by the "vehicle acceleration calculation" portion 15c, and continues at step S111.

[0142] At step S109, the "reach-top acceleration demand calculation" section 15b sets the value of the signal acc_demand to zero, corresponding to an acceleration rate of zero.

[0143] At step S111 , the “reach-top acceleration demand calculation” section 15 b determines whether the value of acc_demand is equal to the value of tgt_crest_acc determined at step S103 .

[0144] If the value of acc_demand=tgt_crest_acc, the method continues at step S113 , otherwise the method continues at step S115 .

[0145] At step S113, the "reach-top acceleration demand calculation" section 15b exits the jerk mitigation function and continues to output a value of acc_demand equal to the value of tgt_crest_acc calculated at step S103.

[0146] At step S115, the "reach top acceleration demand calculation" portion 15b reduces the value of acc_demand by a calibratable amount, and then continues at step S111 after the predetermined time period has passed. It will be understood that step S111 will be repeated until the expected value of acceleration acc_demand output by the "reach top acceleration demand calculation" portion 15b corresponds to the expected value tgt_crest_acc. It will be understood that the amount by which the "reach top acceleration demand calculation" portion 15b reduces the value of acc_demand and the value of the predetermined time period are arranged so that the amount of jerk experienced by the vehicle does not exceed a predetermined jerk measure (jerk limit value). It will be understood that in the present embodiment, the predetermined jerk measure depends on the value of the comfort parameter, and the predetermined jerk measure is lower for higher levels of required comfort. As described above, in the present embodiment, higher values ​​of the comfort parameter correspond to higher levels of required comfort.

[0147] It will be appreciated that the amount by which the value of cc_demand is reduced by the "reach top acceleration demand calculation" portion 15b and the value of the predetermined time period are arranged so that the amount of jerk experienced by the vehicle does not exceed the predetermined jerk measure. Fig. 9 As described, it will be appreciated that in this embodiment, the predetermined jerkiness measure depends on the value of the comfort parameter, with the predetermined jerkiness measure being lower for a higher level of required comfort. Also as described above, in this embodiment, a higher value of the comfort parameter corresponds to a higher level of required comfort.

[0148] Fig.10 It shows how the VCU 15 controls the vehicle speed once the crest event is over.

[0149] At step S201, the "reach top acceleration requirement calculation" part 15b determines whether the reach top event is over. If the event is over, the method continues at step S203, otherwise step S201 is repeated.

[0150] At step S203, the "reach-top acceleration requirement calculation" section 15b sets the value of tgt_crest_acc to the maximum allowed value Amax of acceleration, and the method then continues at step S205.

[0151] At step S205, the "reach top acceleration demand calculation" part 15b determines whether the value of acc_demand currently output by the "reach top acceleration demand calculation" part 15b is equal to the value of tgt_crest_acc. If acc_demand=tgt_crest_acc, the method continues at step S207, otherwise the method continues at step S209.

[0152] At step S207, the "top arrival acceleration demand calculation" section 15b exits the jerk reduction function and maintains the value of acc_demand until the next top arrival is detected.

[0153] At step S209, the "reach top acceleration demand calculation" portion 15b increases the value of acc_demand by a calibratable amount. Then, once the predetermined period of time has elapsed, the method continues at step S205.

[0154] It will be appreciated that the amount by which the value of cc_demand is reduced by the "reach top acceleration demand calculation" portion 15b and the value of the predetermined time period are arranged so that the amount of jerk experienced by the vehicle does not exceed the predetermined jerk measure. Fig. 9 As described, it will be appreciated that in this embodiment, the predetermined jerkiness measure depends on the value of the comfort parameter, with the predetermined jerkiness measure being lower for a higher level of required comfort. Also as described above, in this embodiment, a higher value of the comfort parameter corresponds to a higher level of required comfort.

[0155] Fig.11 is a schematic diagram of an electronic controller 15 ′ including the VCU 15 and configured to implement a speed control system of the VCU 15 .

[0156] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the application.

Claims

1. A speed control system for a vehicle, the speed control system being configured to cause the vehicle to operate according to a target speed value, the speed control system comprising one or more controllers, the speed control system being configured to: determining when the vehicle is reaching the top, and causing a speed reduction of the vehicle based on a determination that the vehicle is reaching a crest, in, When a vehicle speed reduction is determined to be required in response to a determination that the vehicle is reaching a crest, the speed control system is configured to limit a value of jerk associated with the speed reduction so that the value of the jerk does not exceed a jerk limit value, the value of the jerk being a rate of change of acceleration of the vehicle. 2 . The speed control system of claim 2 , configured to receive a driving surface gradient signal indicative of a gradient of a driving surface on which the vehicle is driving.

3. A speed control system according to claim 1 or claim 2, configured to set the jerk limit value at least partly in dependence on at least one vehicle parameter.

4. A speed control system according to claim 3 when dependent on claim 2, the speed control system being arranged to set the jerk limit value at least partly in dependence on the gradient of the driving surface.

5. A speed control system according to claim 3 or 4, configured to determine the jerk limit value at least partly from the at least one vehicle parameter by means of a table look-up.

6. A speed control system according to claim 4 or 5, arranged to reduce the jerk limit value as the driving surface gradient becomes increasingly negative.

7. A speed control system according to any one of claims 3 to 6, configured to set the jerk limit value at least partly in dependence on an occupant comfort parameter indicative of a desired level of occupant comfort.

8. A speed control system according to any one of claims 3 to 7, the speed control system being configured to set the jerk limit value at least in part based on at least one of: a terrain indicator parameter indicative of a nature of the terrain on which the vehicle is travelling, an occupancy parameter indicative of the number of occupants of said vehicle, a vehicle ride height parameter indicative of the selected vehicle ride height; and A cross tracking parameter is indicative of an amount of cross tracking experienced by the vehicle.

9. A speed control system according to claim 2 or any one of claims 3 to 8 dependent on claim 2, wherein the speed control system is further configured to receive a pitch rate signal indicating the rate of change of the pitch attitude of the vehicle, and the speed control system is configured to: determine that the vehicle is reaching the top when the pitch change rate information signal indicates that the change in the pitch attitude of the vehicle exceeds a predetermined rate value in a direction corresponding to a decrease in the pitch attitude and the slope signal indicates that the slope value of the driving surface is lower than a limit value.

10. A speed control system according to any preceding claim, configured to cause the speed reduction upon determining that the vehicle is reaching a crest by at least one of: application of braking torque by means of a vehicle braking system; and An amount of positive drive torque applied to one or more wheels of the vehicle is reduced.

11. A system for controlling the speed of a vehicle, comprising: A speed control system according to any preceding claim; as well as One or more sensors configured to output information indicative of vehicle jerkiness.

12. A vehicle comprising a speed control system according to any one of claims 1 to 10 or a system according to claim 11.

13. A method for controlling the speed of a vehicle implemented by a speed control system, comprising: causing the vehicle to operate according to a target speed value; as well as determining when the vehicle is reaching the top, The method includes causing the speed of the vehicle to decrease upon determining that the vehicle is reaching a crest, Thus, when it is determined that a vehicle speed reduction is required in response to a determination that the vehicle is reaching a crest, the method includes limiting a value of jerk associated with the speed reduction so that the value of the jerk does not exceed a jerk limit value, the value of the jerk providing an indication of the rate of change of acceleration of the vehicle.

14. The method according to claim 13, comprising: The jerk limit value is set based at least in part on at least one vehicle parameter.

15. A non-transitory computer readable storage medium having stored thereon instructions which, when executed by one or more electronic processors, cause the one or more electronic processors to perform the method of claim 13 or 14.

Images