Vehicle speed control system and method

Abstract

Aspects of the present invention relate to a speed control system (15), method, and vehicle (10). The system causes the vehicle (10) to travel at a target speed value. The speed control system (15) uses a pitch rate signal indicating the rate of change of the pitch of the vehicle (10) and a road surface gradient signal indicating the gradient of the road surface on which the vehicle (10) is traveling to determine whether the vehicle has reached the summit. The determination of reaching the summit depends on the rate of change of the pitch exceeding a predetermined value and the gradient value of the road surface being less than a predetermined value. The speed control system (15) outputs a speed reduction signal for reducing the speed of the vehicle when the vehicle reaches the summit.

Description

Technical Field

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

[0002] The content of WO2013 / 124321 is incorporated herein by reference.

Background Art

[0003] It is known to provide a speed control system for a vehicle, particularly a speed control system for operating a vehicle according to a target speed value. It is desirable to provide an improved speed control system to assist in traversing terrain with obstacles such as slopes that a driver must overcome.

Summary of the Invention

Problems to be Solved by the Invention

[0004] When traveling on terrain that includes the crest of a slope that causes the vehicle's nose to dip in front of the vehicle, the driver may want to reduce the vehicle's speed as the vehicle passes over the crest. Reducing the speed helps the driver survey the terrain in front of the vehicle and plan the vehicle's path as it passes through the terrain.

[0005] An object of the present invention is to solve one or more drawbacks associated with the prior art.

Means for Solving the Problems

[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 for controlling the speed of a vehicle as described in the appended claims.

[0007] According to one aspect of the present invention, a speed control system for a vehicle is provided. The speed control system is configured to operate the vehicle according to a target speed value and includes one or more controllers. The speed control system receives a pitch rate signal indicating a rate of change of the pitch of the vehicle; receives a road surface gradient signal indicating a gradient of the road surface on which the vehicle is traveling; and includes determining whether the vehicle has reached the top based on the following: the rate of change of the pitch exceeding a predetermined value; and the gradient value of the road surface being less than a predetermined value; The speed control system is configured to output a speed reduction signal for reducing the speed of the vehicle in response to a determination that the vehicle has reached the top.

[0008] Embodiments of the present invention have the advantage that the driver's workload is reduced because there is no need to decelerate the vehicle to survey the terrain in front of the vehicle before the vehicle crosses the terrain by reducing the speed when the speed control system determines that the vehicle has reached the top of the terrain. Rather, the speed control system determines when it is appropriate to decelerate the vehicle and takes appropriate measures. Furthermore, the speed control system decelerates the speed at an appropriate timing during the process of passing through the terrain, thereby improving the stability of the vehicle.

[0009] Some embodiments of the present invention have the advantage that they can also reduce the driver's discomfort. It should be understood that if the speed control system does not intervene to reduce the vehicle speed when it reaches the top, the driver may consider the speed to be too fast for the type of terrain, feel uneasy about the vehicle speed, and lose trust in the speed control system.

[0010] The applicant has recognized that when the speed reduction is triggered in response to specific conditions being met regarding the rate of change of pitch and the gradient of the driving surface, the speed control system may erroneously detect the summit, unnecessarily reduce the speed, and cause inconvenience to the user. By reducing this possibility, the user satisfaction may be improved. Therefore, embodiments of the present invention aim to mitigate the problem of being erroneously determined that the vehicle has reached the summit.

[0011] It should be understood that pitch means the pitch attitude of the vehicle.

[0012] Reaching the summit corresponds to a decrease in the pitch of the vehicle, that is, it should be understood that the front end of the vehicle is moving downward relative to the rear of the vehicle.

[0013] It should be understood that in this specification, a positive gradient corresponds to an uphill gradient and a negative gradient corresponds to a downhill gradient.

[0014] The speed control system is an "off-road" or "off-highway" speed control system. Optionally, the system can be configured to reduce the speed when the vehicle is determined to have reached the summit by at least one of the following: Application of braking torque by the vehicle braking system; and Reduction in the amount of positive drive torque applied to one or more wheels of the vehicle.

[0015] Optionally, the system may be configured to select the amount of speed reduction according to the gradient of the driving surface. For example, on a driving surface with low grip such as grass, gravel, or snow, the speed may be further reduced compared to a driving surface with high grip such as asphalt or concrete.

[0016] The advantage of this function is that the speed control system can reduce the speed according to the determination of whether the vehicle has climbed to an appropriate degree corresponding to the gradient of the driving surface.

[0017] Optionally, the amount by which the speed is decreased is selected substantially instantaneously according to the gradient of the driving surface.

[0018] Accordingly, the amount of deceleration is selected according to the gradient of the driving surface corresponding to the current position of the vehicle, but it should be understood that there may be a delay associated with the acquisition and processing of sensor data to obtain such data. Accordingly, if the gradient changes while the speed is decreasing, the amount of braking torque and / or the reduction in the propulsion drive torque applied can be changed accordingly. The speed can be decreased, for example, by less than 30 km / h, 30 km / h, 25 km / h, 20 km / h, 15 km / h, 12 km / h, 10 km / h, 5 km / h, 3 km / h, or 1 km / h.

[0019] Optionally, the system can be configured to calculate an estimated driving surface gradient value based on the driving surface gradient signal, and the speed control system is configured to decrease the vehicle speed if it is determined that the vehicle has reached the summit further according to the estimated driving surface gradient value.

[0020] Optionally, the system may be configured to decrease the speed of the vehicle if it is determined that the vehicle has reached the summit by at least one of the following: A predetermined speed reduction period after the determination that the vehicle has reached the summit, and A predetermined speed reduction distance after the determination that the vehicle has reached the summit.

[0021] The predetermined speed reduction period can be any appropriate time period, such as 1 second, 2 seconds, 5 seconds, 10 seconds, or other appropriate values. The predetermined speed reduction distance can be any appropriate distance, such as 1 times the wheelbase, 2 times the wheelbase, 3 times the wheelbase, or other appropriate distances. It should be understood that the wheelbase means the 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.

[0022] Optionally, if the system decelerates the vehicle's speed in response to the first determination that the vehicle has reached the summit, the control system may be configured not to further decelerate the vehicle's speed in response to the second determination that the vehicle has reached the summit, unless the second determination occurs under at least one of the following conditions: After at least a predetermined summit detection period has elapsed since the first determination that the vehicle has reached the summit, and After at least a predetermined summit detection distance has elapsed since the first determination that the vehicle has reached the summit.

[0023] The predetermined summit detection period can be any suitable time period such as 2 seconds, 5 seconds, 10 seconds, or other suitable values. The predetermined summit detection distance can be any suitable distance such as 1 times the wheelbase, 2 times the wheelbase, 3 times the wheelbase, or other suitable distances.

[0024] In some embodiments, the predetermined summit detection period is substantially 2 times the predetermined speed reduction period.

[0025] In one embodiment, the predetermined speed reduction period is 2 seconds and the predetermined summit detection period is 4 seconds.

[0026] In one embodiment, the predetermined speed reduction distance corresponds to approximately 2 times the vehicle's wheelbase, and the predetermined summit detection distance corresponds to approximately 4 times the wheelbase.

[0027] Optionally, a speed control system configured to output a speed reduction signal to reduce the vehicle's speed in response to a determination that the vehicle has reached the summit includes a speed control system configured to output a vehicle deceleration requirement corresponding to the required deceleration rate of the vehicle.

[0028] The deceleration requirement can also be said to be an acceleration requirement when the acceleration rate is negative. It should be understood that when speed reduction is required, the deceleration requirement usually corresponds to a negative acceleration rate, that is, the deceleration of the vehicle.

[0029] Optionally, the system can be configured such that the vehicle deceleration requirement depends at least in part on the grade of the driving surface.

[0030] Optionally, the system may be configured such that the magnitude of the deceleration requirement increases in response to an increase in the grade of the driving surface.

[0031] Optionally, the vehicle deceleration requirement depends at least in part on a user-selectable input indicating a desired level of passenger comfort.

[0032] Optionally, the system may be configured such that the magnitude of the deceleration requirement increases in response to an increase in the desired level of passenger comfort.

[0033] According to another aspect of the present invention, there is provided a system for controlling the speed of a vehicle, including: a speed control system according to the foregoing aspect; and one or more sensors configured to output signals indicating: the pitch of the vehicle and / or the rate of change of the pitch of the vehicle; and the grade of the driving surface.

[0034] In some embodiments, the one or more sensors can include an accelerometer or a gyroscope. Other suitable sensors are known to those skilled in the art and may be utilized in further embodiments.

[0035] According to yet another aspect of the present invention, there is provided a vehicle including the speed control system of the foregoing aspect or the system of the foregoing aspect.

[0036] According to a further aspect of the present invention, there is provided a method for controlling the speed of a vehicle executed by a speed control system, the method including operating the vehicle according to a target speed value, and further receiving a pitch rate signal indicating the rate of change of the pitch attitude of the vehicle; receiving a driving surface grade signal indicating the grade of the driving surface on which the vehicle is traveling; and Determining whether the vehicle has reached the summit, including: The rate of change of the pitch attitude exceeds a predetermined value; and The gradient value of the driving surface is less than a predetermined value; This method includes outputting a speed reduction signal for reducing the speed of the vehicle in response to a determination that the vehicle has reached the summit.

[0037] In one aspect of the present invention, there is provided a vehicle speed control system including: Means for automatically operating the vehicle according to a target speed value; Means for receiving pitch rate information indicating the rate of change of the pitch attitude of the vehicle; Means for receiving driving surface gradient information indicating the gradient of the driving surface on which the vehicle is traveling; and Means for determining that the vehicle has reached the summit, wherein the means for determining that the vehicle has reached the summit is configured to determine that the vehicle has reached the summit when it is shown as pitch rate information that the change in the pitch attitude of the vehicle exceeds a predetermined rate in the direction corresponding to the decrease in the pitch attitude and the gradient value of the driving surface is below the limit value, where the uphill gradient corresponds to a gradient value greater than zero and the downhill gradient corresponds to a gradient value less than zero. Including A speed control system configured to reduce the speed of the vehicle when it is determined that the vehicle has reached the summit.

[0038] According to yet another aspect of the present invention, there is provided a non-transitory computer-readable storage medium storing instructions that, when executed by one or more electronic processors, cause the one or more electronic processors to execute the method of the foregoing aspect.

[0039] Within the scope of the present application, it is expressly intended that the various aspects, embodiments, examples, and alternatives described in the preceding paragraph, claims, and / or the following description and drawings, particularly their individual features, can be employed independently or in any combination. That is, all embodiments and / or features of embodiments can be combined in any manner and / or combination as long as such features are not incompatible. The applicant reserves the right to amend the originally filed claims or to file new claims accordingly. This includes the right to amend the originally filed claims to be dependent on the features of other claims or to incorporate the features of other claims, even if they were not originally claimed as such.

[0040] One or more embodiments of the present invention will be described by way of example only with reference to the accompanying drawings.

Brief Description of the Drawings

[0041]

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DETAILED DESCRIPTION OF THE INVENTION

[0042] The content of WO2013 / 124321 is incorporated herein by reference.

[0043] FIG. 1 is a schematic view 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 a coupling 13. The coupling 13 is arranged such that when the vehicle 10 is accelerated from a stopped state, the transmission 12 can gradually reach a speed compatible with the motor speed. The coupling 13 is typically a friction clutch, a torque converter, or the like. The transmission 12 is configured to drive a pair of rear wheels 10RW and, optionally, a pair of steerable front wheels 10FW. The accelerator pedal 1 enables the driver to control the amount of torque generated by the motor 11 under the control of a powertrain controller 17, while the brake pedal 2 enables the driver to apply the brake system under the control of a brake controller 16. A driving mode selector 19 is provided, whereby the driver can select one of a plurality of off-road driving modes including an on-road driving mode, or 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 enables the vehicle 10 to select an "automatic response mode" in which the vehicle automatically determines the optimal driving mode at any given time. The driving mode may be referred to as a "terrain response" (or "TR") mode.

[0044] Vehicle 10 is equipped with a vehicle control unit (VCU) 15 that is operable to execute a low-speed vehicle speed control function or system. The low-speed vehicle speed control function is also referred to as an "off-road" or "off-highway" cruise control function or system. The low-speed vehicle speed control function is operable when the vehicle speed VREF does not exceed a predetermined maximum speed. In this embodiment, the predetermined maximum speed is 30 km / h. When exceeding 30 km / h, the VCU 15 can operate to execute a high-speed vehicle speed control function or system. The VCU 15 can be described as executing a low-speed vehicle speed control system or a high-speed vehicle speed control system. The functions of both the low-speed vehicle speed control system and the high-speed vehicle speed control system are controlled by the user via an input control attached to the steering wheel 171 of the vehicle 10. The steering wheel 171 is shown in more detail in FIG. 2. It should be understood that the low-speed vehicle speed control function or system is useful during off-highway driving conditions, while the high-speed vehicle speed control function or system is useful during on-highway driving conditions such as on a relatively smooth and dry paved road surface or a concrete driving surface.

[0045] The input control includes a "speed setting" control 173. When this is actuated, the value of the parameter driver_set_speed is set to be approximately equal to the current vehicle speed. Pressing the "+" (or "plus") button 174 can increase the set speed, and pressing the "-" (or "minus") button 175 can decrease the set speed. In some embodiments, when the speed control function is not active when the "+" button 174 is pressed, the speed control function becomes active.

[0046] In this embodiment, when the high-speed speed control system is operating, the VCU 15 is configured to execute an active speed control system (or "active cruise control"). As will be described later, the active speed control system is configured to maintain a predetermined distance behind a preceding vehicle when the vehicle 10 is in a specific situation. The wheel 171 also has a pair of following distance control buttons 178 and 179 for setting the value of the parameter distance_following. This parameter is the distance that the driver desires to maintain the vehicle 10 behind the preceding vehicle. The VCU 15 is operable to control the vehicle 10 to maintain a distance substantially equal to the distance represented by the parameter distance_following behind the preceding vehicle. The first button 178 is operable to increase the value of the parameter distance_following, and thus increase the distance between the vehicle 10 and the preceding vehicle, and the second button 179 is operable to decrease the value of the parameter distance_following. The vehicle 10 has a radar module 5 attached to its front surface and configured to project a radar beam in the forward direction of the vehicle 10. The module 5 is configured to detect the radiation reflected by the preceding vehicle and determine the distance between the preceding vehicle and the vehicle 10 ("host" vehicle). A signal indicating the current speed of the host vehicle 10 is provided to the module 5. From this signal and data regarding the change in the distance from the host vehicle 10 to the preceding vehicle as a function of time, the module 5 can calculate the speed of the preceding vehicle. Other configurations for determining the distance from the preceding vehicle and the speed of the preceding vehicle are also useful. In some embodiments, the active speed control function is not provided, and the subsequent following distance control buttons 178 and 179 are omitted. In some embodiments, the radar module 5 is omitted.

[0047] The high-speed speed control system is not the subject of this application. The remainder of this specification relates to the low-speed speed control system, unless otherwise specified.

[0048] When the low-speed speed control system is activated, the VCU 15 controls the speed of the vehicle 10 according to the set speed selected by the driver, driver_set_speed, or a target speed value that is substantially equal to a lower value if desired as described in more detail below. The VCU 15 accomplishes this by calculating the maximum allowable speed max_set_speed of the vehicle 10 at a particular point in time. The VCU 15 sets the value of max_set_speed to the value of the driver set speed driver_set_speed, except when a lower value is desired as described in more detail below. The VCU 15 controls the speed of the vehicle 10 according to max_set_speed, which is the target speed value of the vehicle, by causing the speed of the vehicle VREF to equal the value of max_set_speed.

[0049] Next, the VCU 15 outputs a target value of acceleration acc_tgt at a particular point in time to the power train controller 17 and the brake controller 16 so that the vehicle speed determined with reference to the vehicle reference speed VREF maintains a desired value. When the driver overrides the speed control system and VREF exceeds 30 km / h, the speed control system stops operating until VREF is 30 km / h or less.

[0050] The driver can set the value of driver_set_speed of the low-speed speed control system to the current vehicle speed VREF (conditioned on VREF not exceeding 30 km / h) by pressing the "Speed Setting" control 173 while the vehicle 10 is in motion. When the VCU 15 detects that the "Speed Setting" control 173 has been pressed, it takes 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 30 km / h and the set speed control 173 is pressed, the high-speed speed control system is activated. In this embodiment, since the value of driver_set_speed is set to a value exceeding 30 km / h, when the high-speed speed control system is activated, the low-speed speed control system does not automatically restart even if the speed drops below 30 km / h.)

[0051] As described above, when the vehicle 10 is traveling along the road and the high-speed speed control system is active, that is, when VREF and driver_set_speed exceed the minimum allowable set speed set_speed_min (30 km / h in this embodiment), the VCU 15 operates so that the user can command the VCU 15 to maintain the current vehicle speed by pressing the set speed control 173. When there is no traffic in front of the vehicle 10 or there are no other factors (described later) that require a low speed, the VCU 15 controls the speed VREF of the vehicle 10 to maintain VREF approximately equal to the set speed value driver_set_speed.

[0052] In this embodiment, when the VCU 15 detects (by the radar module 5) that there is a preceding vehicle in front of the vehicle 10, the VCU 15 can operate to reduce the speed of the host vehicle 10 according to the speed of the preceding vehicle in order to maintain a distance of a specified distance or more behind the preceding vehicle. The specified distance can be set by the driver using the "inter-vehicle distance" control buttons 178, 179 as described above. This function can only be used when the high-speed speed control system is active.

[0053] Vehicle 10 has a human machine interface (HMI) in the form of a touch screen 18 through which the VCU 15 can communicate with the user. As described above, when the low-speed speed control system is active, the VCU 15 is operable to calculate a maximum allowable 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 for controlling the vehicle 10 according to the terrain. Embodiments of the present invention can reduce driver intervention and improve vehicle stability when operating under off-highway conditions. That is, since the VCU 15 determines the maximum allowable value max_set_speed of the set speed and limits the set speed accordingly, the driver does not need to intervene to lower the value of the vehicle set speed when the terrain permits, or to increase the set speed when the terrain permits.

[0054] Figure 3 shows how the VCU 15 determines the value of max_set_speed. The VCU 15 includes a "maximum set speed calculation" part (or "engine") 15a, a "peak acceleration request calculation" part (or "engine") 15b, and a "vehicle acceleration calculation" part (or "engine") 15c. Further, the input to the "maximum set speed calculation" part (or "engine") 15a includes a "lateral acceleration limit calculation" part 15d.

[0055] The "Vehicle Acceleration Calculation" section 15c is configured to calculate a target value acc_tgt of the acceleration of the vehicle 10 at a specific point in time based on the received input including the inputs from the "Maximum Set Speed Calculation" section 15a and the "Summit Acceleration Requirement Calculation" section 15b. As described above, the "Vehicle Acceleration Calculation" section 15c outputs the value of the desired acceleration at a given point in time acc_tgt, optionally as a speed reduction signal, to the power train controller 17 and the brake controller 16, and the power train controller 17 and the brake controller 16 attempt to make the actual vehicle acceleration equal to acc_tgt as soon as possible within a given comfort limit. The brake controller or the power train controller can change the speed by applying brakes or brake torque to the wheels of the vehicle by the vehicle brake system. Alternatively, or in addition, the acceleration or deceleration of the vehicle can also be done by reducing the amount of positive drive torque applied to one or more wheels of the vehicle. The VCU 15 controls the acceleration (positive or negative) at a specific point in time by changing the value of acc_tgt output by the "Vehicle Acceleration Calculation" section 15c at the desired speed. In some embodiments including the embodiment of FIG. 3, the "Vehicle Acceleration Calculation" section 15c receives the value of the comfort parameter COMFORT indicating the level of comfort required by the vehicle occupants, as will be described in more detail below. Next, the "Vehicle Acceleration Calculation" section 15c adjusts the maximum allowable rate of change of acceleration (or "jerk") at a specific point in time according to the value of the comfort parameter, so as to be able to control the comfort of the occupants. Therefore, when the required level of comfort of the occupants is high, the "Vehicle Acceleration Calculation" section 15c reduces the maximum allowable value of jerk to enhance the comfort of the occupants. Therefore, when a change in vehicle acceleration is required, the "Vehicle Acceleration Calculation" section 15c limits the rate of change of acceleration to enhance the comfort of the occupants. The maximum allowable amount of jerk may be referred to as the "jerk limit value".

[0056] The "maximum set speed calculation" part 15a of the VCU15 is configured to receive inputs corresponding to several vehicle parameters in addition to the current value of driver_set_speed. As described above, the "maximum set speed calculation" part 15a outputs a value of max_set_speed that is not greater than the value of driver_set_speed, but as will be described in more detail below, it may be smaller if the "maximum set speed calculation" part 15a determines that the driving conditions so require. The parameters are as follows: (a) The reference value of the current vehicle's surface friction coefficient, "μmeas", is a value calculated by the VCU15 based on the value of one or more parameters such as the amount of torque applied to a wheel that has induced excessive wheel slip; (b) The value of the predicted surface friction coefficient corresponding to the currently selected vehicle driving mode, "μTRmode", is a value defined for each driving mode; (c) The current value of the steering angle corresponds to the steerable road wheel angle, or, in some embodiments, corresponds to the position of the steering wheel, "steering angle, δ"; (d) The current yaw rate of the vehicle (determined with reference to the output of the accelerometer), "yaw rate"; (e) The current measured value of the lateral acceleration, "MEASURED LAT.ACC." (determined with reference to the output of the accelerometer); (f) The current measured value of the surface roughness, "SURFACE ROUGHNESS" (determined with reference to the articulation of the suspension). In some embodiments, the VCU15 may also receive (g) a signal indicating the current position of the vehicle, "GPS position" (determined with reference to the output of the Global Positioning System (GPS) or other global navigation satellite systems or other positioning systems), and / or (h) information obtained by a camera system, "camera". The information obtained by the camera system or image system may include, for example, a warning when it is determined that the vehicle 10 may deviate from the off-road lane or the track.

[0057] The "Lateral Acceleration Limit Calculation" part 15d of the VCU 15 is configured to determine the maximum allowable lateral acceleration max_lat_acc of the vehicle 10 in motion from the reference value μmeas of the road surface friction coefficient and the expected value μTRmode of the road surface friction coefficient. The VCU 15 uses this value of max_lat_acc to limit the value of max_set_speed when the vehicle is cornering and prevent understeer.

[0058] In this embodiment, the "Maximum Set Speed Calculation" part 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 yaw rate and the measured lateral acceleration of the vehicle. When the VCU 15 detects the presence of understeer, the VCU 15 is operable to reduce the value of max_set_speed accordingly. In some embodiments where a signal indicating the current position of the vehicle is received, the VCU 15 can also consider the travel path of the vehicle determined with reference to the position signal and enhance the reliability of the determination of the amount of understeer present (if any).

[0059] In some embodiments, the yaw rate and the measured lateral acceleration are not used for determining the amount of understeer. Other configurations are also useful.

[0060] The "Maximum Set Speed Calculation" part 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 travels. When the surface roughness increases, the value of max_set_speed may decrease.

[0061] In this embodiment, the peak acceleration demand calculation unit 15b of the VCU 15 also receives a road surface gradient signal indicating the gradient of the road surface on which the vehicle 10 travels and a pitch rate signal indicating the rate of change of the pitch of the vehicle 10. The peak acceleration demand calculation unit 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 predetermined time point. The peak acceleration demand calculation unit 15b outputs an acceleration demand signal acc_demand to the vehicle acceleration calculation unit 15c in order to accelerate the vehicle 10 at the desired speed tgt_crest_acc.

[0062] When the peak acceleration demand calculation unit 15b determines that the vehicle has not reached the peak, the value of the parameter acc_demand is set to correspond to the maximum allowable value Amax of the vehicle acceleration. This is because the vehicle acceleration calculation unit 15c does not decrease the vehicle speed in response to the signal acc_demand, but only decreases the vehicle speed in response to the signal max_set_speed received from the maximum set speed calculation unit 15a.

[0063] When the peak acceleration demand calculation unit 15b determines that the vehicle has reached the peak, the value of the parameter acc_demand is set to correspond to the desired acceleration rate tgt_crest_acc. The peak acceleration demand calculation unit 15b of the VCU 15 is configured to determine whether the vehicle has reached the peak based on the road surface gradient signal ("GRADIENT") and the pitch rate signal ("PITCHRATE"). It should be understood that the value of the acceleration rate acc_demand corresponds to a negative acceleration rate in order to decrease the vehicle speed when it is determined that the vehicle has reached the peak.

[0064] In particular, the peak acceleration demand calculation unit 15b of the VCU 15 is configured to determine that the vehicle has reached the peak when the following conditions are satisfied: (a) The rate of change of the pitch of the vehicle determined with reference to the pitch rate signal exceeds a predetermined value over a predetermined period, and (b) The gradient value of the road surface determined with reference to the road surface gradient signal is below a predetermined value.

[0065] In this specification, the gradient value of the running surface may be referred to as the running surface gradient value.

[0066] In this embodiment, the predetermined value of the change rate of the pitch of the vehicle is 5 degrees per second, the predetermined period is 1 second, and the predetermined value of the gradient of the running surface is +5%. Therefore, in order for the peak acceleration requirement calculation unit 15b of the VCU 15 to determine that the vehicle has reached the peak, it is understood that the gradient of the running surface must be less than the value of +5% (uphill gradient), that is, the gradient of the running surface must be an uphill gradient of less than 5%. The running surface gradient condition should be understood to be satisfied, for example, when the gradient of the running surface is +4%, substantially zero (corresponding to a horizontal plane), or negative (corresponding to a downhill slope). Other predetermined values of the pitch change rate, the predetermined period, and the predetermined gradient may be useful in some embodiments.

[0067] As described above, it should be understood that when the peak acceleration requirement calculation unit 15b of the VCU 15 determines that the vehicle has not reached the peak, it outputs the value of acc_demand corresponding to the maximum allowable value Amax of the vehicle acceleration. This is to make the vehicle acceleration calculation unit 15c ignore the acc_demand signal and give priority to the max_set_speed signal received from the maximum set speed calculation unit 15a of the VCU 15.

[0068] In some embodiments, when the VCU 15 determines that the condition for determining that the vehicle has reached the peak is satisfied, in order to cause the vehicle acceleration calculation unit 15c to impose a deceleration rate on the vehicle 10, the value of acc_demand is set to a fixed predetermined value corresponding to a negative acceleration, that is, a deceleration rate. In response to receiving a request from the "peak acceleration requirement calculation" unit 15b for the negative acceleration rate of the vehicle 10, it should be understood that the vehicle acceleration calculation unit 15c of the VCU 15 decreases the value of the vehicle speed VREF at a rate corresponding to the requested deceleration rate acc_demand.

[0069] 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 a powertrain controller or control system, or another vehicle system such as a brake or braking controller or control system, such that the vehicle's speed is reduced while the peak is being identified.

[0070] In this embodiment, the value of acc_demand itself depends on at least one parameter. In this embodiment, when the VCU15 determines that the condition for determining that the vehicle has reached the peak is satisfied, the "peak acceleration request" calculation unit 15b of the VCU15 calculates the value of tgt_crest_acc that depends on the following parameters: (1) The current value of the road surface gradient. The value of tgt_crest_acc becomes more negative as the road surface gradient becomes more negative (corresponding to a gradually increasing deceleration rate); (2) The driving mode in which the vehicle is currently driving ("TR mode"); (3) The value of the comfort parameter "COMFORT" (indicating the level of comfort required by the vehicle's occupants). The value of tgt_crest_acc increases in the negative direction as the required level of comfort increases (corresponding to a gradually increasing deceleration rate). Therefore, the decrease in the speed of the vehicle 10 during the period when deceleration is imposed becomes greater as the required level of comfort increases.

[0071] It is understood that the value of tgt_crest_acc can be set according to the driving mode in accordance with an empirically determined look-up table (LUT). In the present embodiment, when the selected driving mode (TR mode) is the sandy mode, the vehicle speed does not decrease in response to the determination that the vehicle has reached the crest, but it does decrease in all other driving modes such as the GGS driving mode and the highway driving mode. In the present embodiment, the value of tgt_crest_acc calculated in driving modes other than the sandy mode is substantially the same for a given set of conditions including the value of VREF, the gradient, and the rate of change of pitch. In some alternative embodiments, the value of tgt_crest_acc calculated by the crest acceleration requirement calculation unit 15b in at least two driving modes other than the sandy mode may be different for a given set of conditions.

[0072] In the present embodiment, the VCU 15 is configured to receive an input indicating a desired level of occupant comfort via the touch screen 18, although other input devices such as a rotary dial may also be useful. In the present embodiment, the comfort signal indicates whether the value of the comfort setting is 0 (zero), 1, 2, 3, or 4. A value of zero is considered to correspond to the "off" state of the comfort setting and indicates that the occupant 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 according to the gradient of the driving surface and increases the value of tgt_crest_acc by a factor by which the vehicle speed value gradually decreases as the value of the comfort setting increases. The input indicating the desired level of occupant comfort described in the present embodiment is user-selectable and can thus be referred to as a user-selectable input indicating the desired level of occupant comfort, the desired value of the occupant comfort parameter, the comfort parameter, the desired level of occupant comfort, the value of the comfort parameter, or the level of comfort required by the vehicle occupants.

[0073] In some embodiments, it should be understood that the vehicle 10 is not provided with a function that allows the driver to input a desired value of the occupant comfort parameter.

[0074] In addition, in this embodiment, so as not to cause inconvenience to the user, the VCU 15 is configured such that the value of max_set_speed does not fall below a predetermined minimum value. Therefore, when the vehicle speed VREF reaches the predetermined minimum allowable value, the vehicle acceleration calculation unit 15c does not attempt to decrease the vehicle speed in response to the negative acceleration request from the peak acceleration request calculation unit 15b. In this embodiment, the predetermined minimum value is 2 km / h, but other values can also be used depending on the embodiment.

[0075] As described above, in this embodiment, the VCU 15 is configured to determine that the vehicle has reached the peak when the above peak conditions (a) and (b) are satisfied, and calculate the value of tgt_crest_acc according to the above parameters (1) to (3).

[0076] As described above, in this embodiment, the VCU 15 calculates the value of the parameter tgt_crest_acc, and causes the "vehicle acceleration calculation" unit 15c to apply an acceleration corresponding to the value of tgt_crest_acc to the vehicle 10. In this embodiment, after it is determined that the vehicle has reached the peak, this acceleration rate is applied for a predetermined period, that is, a predetermined vehicle speed reduction period. The predetermined vehicle speed reduction period is 2 seconds in this embodiment, but may be other appropriate periods such as 1 second, 5 seconds, 10 seconds, or other appropriate values depending on the embodiment.

[0077] In another embodiment, the VCU 15 calculates the value of the parameter tgt_crest_acc and, after it is determined that the vehicle has reached the crest, instructs the "vehicle acceleration calculation" part 15c to impose an acceleration rate corresponding to the value of tgt_crest_acc on the vehicle 10 over a predetermined distance called the predetermined speed reduction distance. The predetermined deceleration distance can be any suitable distance, such as 1 times the wheelbase, 2 times the wheelbase, 3 times the wheelbase, or any other appropriate distance. It should be understood that in order to be regarded as an appropriate distance, the distance does not necessarily have to be an integer or a multiple of an integer of the wheelbase. The wheelbase means the center-to-center distance from the front wheels to the rear wheels of the vehicle in a direction parallel to the longitudinal axis of the vehicle.

[0078] FIG. 4 shows the vehicle 10 climbing a slope towards the crest C, and the running surface becomes almost horizontal after passing over the crest C. When the vehicle 10 passes through the crest C, the VCU 15 detects a decrease in the slope of the running surface and a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). When the rate of change of the pitch exceeds a predetermined value of 5 degrees per second and the slope of the running surface is less than a 5% (uphill) slope, i.e., the slope is less than 5%, horizontal, or a downhill slope, the VCU 15 determines that the vehicle 10 has reached the crest and starts to calculate the value of tgt_crest_acc according to the above parameters (1) to (3).

[0079] FIG. 5 shows the vehicle 10 climbing a slope towards the crest C, and the running surface has a negative (downhill) slope after passing over the crest C. When the vehicle 10 passes through the crest C, the VCU 15 detects a decrease in the slope of the running surface and a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). When the rate of change of the pitch exceeds a predetermined value of 5 degrees per second and the slope of the running surface is less than a 5% (uphill) slope, i.e., the slope is less than 5%, horizontal, or a downhill slope, the VCU 15 determines that the vehicle 10 has reached the crest and starts to calculate the value of tgt_crest_acc according to the above parameters (1) to (3).

[0080] FIG. 6 shows the vehicle 10 moving towards the summit C across a substantially horizontal driving surface (i.e., a gradient of approximately 0%). Beyond the summit C, the driving surface has a negative gradient (downhill slope). Therefore, the summit condition (b) that the gradient value of the driving surface determined with reference to the driving surface gradient signal is 5% or less is satisfied. When the vehicle 10 passes through the summit C, the VCU 15 detects a decrease in the vehicle pitch (i.e., the vehicle pitch attitude). When the rate of change of the pitch exceeds a predetermined value of 5 degrees per second, the VCU 15 determines that the summit condition (a) is satisfied and that the vehicle 10 has reached the summit. Next, the VCU 15 begins to calculate the value of tgt_crest_accin according to the above parameters (1) to (3).

[0081] In the present embodiment, when the VCU 15 calculates the value of tgt_crest_acc in response to the first determination that the vehicle has reached the summit, the VCU 15 does not impose further deceleration in response to the second determination that the vehicle has reached the summit unless the second determination is made after a predetermined summit detection period has elapsed since the first determination that the vehicle has reached the summit.

[0082] In some embodiments, the predetermined summit detection period corresponds substantially to twice the predetermined speed reduction period. Other multiples may also be useful in some embodiments.

[0083] In the present embodiment, the predetermined summit detection period is a period of 4 seconds, which is twice the 2 - second predetermined speed reduction period. However, depending on the embodiment, other appropriate periods such as 5 seconds, 10 seconds, or other suitable values may also be used.

[0084] In another embodiment, when the VCU15 calculates the value of acc_demand in response to the first determination that the vehicle has reached the summit, the VCU15 will not impose further deceleration thereafter in response to the second determination that the vehicle has reached the summit, unless the second determination is made after a predetermined summit detection distance has elapsed since the first determination that the vehicle has reached the summit. The predetermined summit detection distance can be any appropriate distance, such as 1 times the wheelbase, 2 times the wheelbase, 3 times the wheelbase, 4 times the wheelbase, or any other appropriate distance.

[0085] In some embodiments, the predetermined summit detection distance corresponds substantially to 2 times the predetermined speed reduction distance. Other multiples may also be useful in some embodiments.

[0086] In one embodiment, the predetermined speed reduction distance corresponds approximately to 2 times the wheelbase of the vehicle, and the predetermined summit detection distance corresponds approximately to 4 times the wheelbase.

[0087] FIG. 7 shows the path of the vehicle 10 crossing two summits separated by a relatively short distance. The vehicle 10 is shown climbing the hill towards the first summit C1. When the vehicle passes the summit C1, at position X1, the condition for the VCU15 to determine that the vehicle 10 has reached the mountaintop is satisfied. Accordingly, the VCU15 calculates the value tgt_crest_acc of the acceleration imposed on the vehicle when the vehicle passes the summit.

[0088] After passing through position X1, VCU15 starts a timer. VCU15 continues to calculate the value of tgt_crest_acc according to the values of the aforementioned parameters (a) to (c). When a predetermined deceleration period (2 seconds in this embodiment) elapses, vehicle 10 finishes calculating the value of tgt_crest_acc according to the values of the aforementioned parameters (a) to (c), and sets the value of acc_demand to the maximum allowable value Amax of vehicle acceleration as described above. Therefore, vehicle acceleration calculation unit 15c ignores the value of acc_demand received when determining the vehicle speed, and returns the vehicle speed to the lower value of the current value of the driver-set speed and the current value of max_set_speed.

[0089] Referring further to FIG. 7, position X2 is the position of vehicle 10, where conditions (a) to (c) are satisfied again, and VCU15 makes a second determination that the vehicle has reached the crest. However, if the time required for the movement from position X1 to position X2 is less than a predetermined crest detection period (4 seconds in this embodiment) after the first determination that the vehicle has reached the crest at position X1, VCU15 ignores the fact that the crest has been detected. However, if the predetermined crest detection period has elapsed when the vehicle reaches position X2, VCU15 responds in the manner described above regarding the arrival at position X1. That is, VCU15 starts a timer, calculates the value of tgt_crest_acc according to the values of parameters (a)-(c), and imposes deceleration on the vehicle.

[0090] FIG. 8 shows the determination of the values of tgt_crest_acc and acc_demand by VCU15. In FIG. 8, the horizontal axis represents the road surface gradient, and 0% represents the state of zero gradient ("0% flat road"). On the horizontal axis, when moving to the left of the state of 0% flat road, the road surface gradient increases in the uphill direction, and when moving to the right of the state of 0% flat road, the road surface gradient increases in the downhill direction.

[0091] As described above, when the VCU 15 determines that the vehicle has not reached the summit, it sets the value of the parameter acc_demand output from the summit acceleration request calculation unit 15b to the maximum allowable value Amax. Therefore, the vehicle acceleration calculation unit 15c does not decrease 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 unit 15a.

[0092] As described above, it should be understood that the speed control system executed by the VCU 15 is configured such that the vehicle acceleration calculation unit 15c cannot decrease the vehicle speed to a value less than a predetermined minimum value. In this embodiment, the predetermined minimum value is 2 km / h, but other values may be useful depending on the embodiment.

[0093] When the summit condition is satisfied, the VCU 15 calculates the value of tgt_crest_acc as described above and also shown in FIG. 8.

[0094] As can be seen from FIG. 8, the value of tgt_crest_acc is set to a negative value according to the value of the comfort parameter (corresponding to a sharp deceleration of the vehicle). In this embodiment, as shown by the trace "A" in FIG. 8, when the value of the comfort parameter is zero (corresponding to the "off" state) or the value "1", when the gradient reaches a value of 2% in the downhill direction (i.e., the gradient is minus 2% or "-2%"), the value of tgt_crest_acc changes from Amax to a negative value. These states are shown by the lines labeled "Comfort = 0, 1" in FIG. 8.

[0095] When the value of the comfort parameter is "2", the value of acc_demand changes from Amax to the value of tgt_crest_acc. This means that when the gradient reaches 0%, the negative value of the acceleration increases. This state is shown by the trace "B" and the line labeled "Comfort = 2" in FIG. 8.

[0096] When the value of the comfort parameter is "3" or "4", if the gradient is less than +5%, the value of tgt_crest_acc increases to a negative value. When the value of the comfort parameter is "4", the rate of increase of tgt_crest_acc in the negative direction becomes steeper. That is, the gradient of the plot of tgt_crest_acc as a function of the gradient becomes steeper, and the speed reduction is greater than when the value of the comfort parameter is "3" or less. This state is shown by the traces "C" in FIG. 8 and the lines labeled "Comfort = 3" or "Comfort = 4".

[0097] In the present embodiment, when the comfort parameter is set to the value "4", which is the highest required value for occupant comfort, the VCU15 is configured to determine that the vehicle has reached the crest when the downward pitch rate is at a lower value than when the value of the comfort parameter is low. This state is shown by the line labeled "Comfort = 4" in FIG. 8. In this embodiment, when the comfort parameter is set to the value "4", the VCU15 is configured to require that, in addition to the gradient being less than 5%, the pitch rate exceeds 3 degrees / second. Other values of the pitch rate, such as 2 degrees / second, 2.5 degrees / second, 4 degrees / second, or other appropriate values, may be useful in some embodiments. Other values of the gradient may also be useful in some embodiments.

[0098] It should be understood that when the value of the comfort parameter is another value such as 1, 2, or 3, different values of the pitch rate may be required before reaching the crest.

[0099] As described above, the "crest acceleration request calculation" section 15b receives the value of the comfort parameter and determines the value of tgt_crest_acc partially depending on the comfort parameter. In some embodiments, the "crest acceleration request calculation" section 15b also adjusts the speed at which the vehicle takes the desired acceleration rate tgt_crest_acc depending on the value of the comfort parameter in order to limit the maximum value of the jerk experienced at a particular instant. The maximum allowable value of jerk (i.e., the jerk limit value) becomes lower as the required level of occupant comfort is higher.

[0100] Figure 9 shows the state of jerk value limitation when the acceleration request changes after the apex is detected. That is, Figure 9 shows the operation of the jerk relaxation function of the "apex acceleration request calculation" unit 15b at the time of apex detection.

[0101] In step S101, the "apex acceleration request calculation" unit 15b determines whether the apex has been detected. If the apex has not been detected, step S101 is repeated. If the apex has been detected, the process proceeds to step S103.

[0102] In step S103, in response to the determination that the vehicle has reached the apex, the "apex acceleration request calculation" unit 15b calculates the target value tgt_crest_acc of acceleration. The value of tgt_crest_acc is calculated according to the gradient of the driving surface, the driving mode, and the values of the comfort parameters. The value of tgt_crest_acc is used to calculate the value acc_demand of the desired acceleration rate of the vehicle 10 at a specific point in time. The value of acc_demand is calculated from the value of tgt_crest_acc and is limited so that the maximum value of jerk does not exceed the jerk limit value.

[0103] In step S105, the "maximum acceleration request calculation" part 15b determines whether the current value of acc_tgt output by the "vehicle acceleration calculation" part 15c is less than 0 meters / second. If the value of acc_tgt is less than 0, the method proceeds to step S107; otherwise, the method continues to proceed to step S109.

[0104] In step S107, the "apex acceleration request calculation" unit 15b sets the value of the signal acc_demand to the current value of acc_tgt output by the "vehicle acceleration calculation" unit 15c, and proceeds to step S111.

[0105] In step S109, the "apex acceleration request calculation" unit 15b sets the value of the signal acc_demand to zero, that is, the value corresponding to an acceleration rate of zero.

[0106] In step S111, the "Crest Acceleration Demand Calculation" unit 15b determines whether the value of acc_demand is equal to the value of tgt_crest_acc determined in step S103.

[0107] If the value of acc_demand is tgt_crest_acc, the method proceeds to step S113; otherwise, it continues to step S115.

[0108] In step S113, the "Crest Acceleration Demand Calculation" section 15b terminates the jerk mitigation function and continues to output the value of acc_demand that is equal to the value of tgt_crest_acc calculated in step S103.

[0109] In step S115, the "Crest Acceleration Demand Calculation" section 15b decreases the value of acc_demand by an adjustable amount, and then, after a predetermined time has elapsed, proceeds to step S111. Note that step S111 is repeated until the target value of acceleration acc_demand output by the "Crest Acceleration Demand Calculation" unit 15b matches the target value tgt_crest_acc. The amount by which the "Crest Acceleration Demand Calculation" unit 15b decreases the value of acc_demand and the value of the predetermined time are set so that the amount of jerk received by the vehicle does not exceed a predetermined amount of jerk (jerk limit value). In this embodiment, it should be understood that the predetermined amount of jerk depends on the value of the comfort parameter, and the higher the required level of comfort, the lower the predetermined amount of jerk. As described above, in this embodiment, the higher the value of the comfort parameter, the higher the required level of comfort.

[0110] The amount by which the "Top Acceleration Demand Calculation" section 15b decreases the value of acc_demand and the value of the predetermined time are to be understood as being adjusted so that the amount of jerk experienced by the vehicle does not exceed a predetermined amount of jerk. As described above with respect to FIG. 9, in the present embodiment, the predetermined amount of jerk depends on the value of the comfort parameter, and it is understood that the higher the required level of comfort, the lower the predetermined amount of jerk. Also, as described above, in the present embodiment, the higher the value of the comfort parameter, the higher the required level of comfort.

[0111] FIG. 10 shows how the VCU 15 controls the vehicle speed after the top event has ended.

[0112] In step S201, the "Top Acceleration Demand Calculation" section 15b determines whether the top event has ended. If the event has ended, the method proceeds to step S203; otherwise, step S201 is repeated.

[0113] In step S203, the "Top Acceleration Demand Calculation" section 15b sets the value of tgt_crest_acc to the maximum allowable acceleration value Amax, and the method proceeds to step S205.

[0114] In step S205, the "Top Acceleration Demand Calculation" section 15b determines whether the value of acc_demand currently output by the "Top Acceleration Demand Calculation" section 15b is equal to the value of tgt_crest_acc. If acc_demand = tgt_crest_acc, the method proceeds to step S207; otherwise, the method continues to step S209.

[0115] In step S207, the "Top Acceleration Demand Calculation" section 15b terminates the jerk mitigation function and maintains the value of acc_demand until the next top is detected.

[0116] In step S209, the "acceleration demand calculation" part 15b increases the value of acc_demand by an amount that can be calibrated. Then, when a predetermined time has elapsed, this method proceeds to step S205.

[0117] It should be understood that the amount by which the "top acceleration demand calculation" part 15b decreases the value of acc_demand and the value of the predetermined time are adjusted so that the amount of jerk experienced by the vehicle does not exceed a predetermined amount of jerk. As described above with respect to FIG. 9, in this embodiment, the predetermined amount of jerk depends on the value of the comfort parameter, and it is understood that the higher the required level of comfort, the lower the predetermined amount of jerk. Also, as described above, in this embodiment, the higher the value of the comfort parameter, the higher the required level of comfort.

[0118] FIG. 11 is a schematic diagram of an electronic control unit 15' included in the VCU 15 and configured to implement the speed control system of the VCU 15.

[0119] It is understood that various changes and modifications can be made to the present invention without departing from the scope of the present invention.

Claims

1. A system for controlling the speed of a vehicle, configured to operate the vehicle according to a target speed value and comprising one or more controllers, the speed control system comprising: receiving a pitch rate signal indicative of a rate of change of pitch of the vehicle; receiving a road surface gradient signal indicative of a gradient of a road surface on which the vehicle is traveling; and determining whether the vehicle has reached a peak based on the following: the rate of change of pitch exceeding a predetermined value; and the gradient value of the road surface being less than a predetermined value; A speed control system configured to output a speed reduction signal for reducing the speed of the vehicle in response to a determination that the vehicle has reached a peak.

2. The speed control system according to claim 1, configured to reduce speed in response to a determination that the vehicle has reached a peak by at least one of the following: application of braking torque by a vehicle braking system; and a decrease in the amount of positive driving torque applied to one or more wheels of the vehicle.

3. The speed control system according to claim 1 or 2, configured such that the amount of speed reduction is selected according to the gradient of the road surface.

4. The speed control system according to claim 3, wherein the amount of speed reduction is selected according to the gradient of the road surface substantially instantaneously.

5. Configured to calculate an estimated road surface gradient value based on the road surface gradient signal, and further configured to reduce the vehicle speed when it is determined that the vehicle has reached a peak according to the estimated road surface gradient value. The speed control system according to any one of claims 1 to 4.

6. The speed control system according to any one of claims 1 to 5, configured to reduce the speed of the vehicle in response to a determination that the vehicle has reached a peak by at least one of the following: a predetermined speed reduction period after the determination that the vehicle has reached a peak; and a predetermined speed reduction distance after the determination that the vehicle has reached a peak.

7. When the speed of the vehicle is decelerated in response to the first determination that the vehicle has reached a peak, the speed of the vehicle is not further reduced in response to the second determination that the vehicle has reached a peak unless the second determination occurs under at least one of the following conditions. The speed control system according to any one of claims 1 to 6. After a predetermined summit detection period has elapsed after the first determination that the vehicle has reached the summit; and / or After a predetermined summit detection distance has elapsed after the first determination that the vehicle has reached the summit.

8. The speed control system configured to output the speed reduction signal for reducing the speed of the vehicle in response to the determination that the vehicle has reached the summit includes a speed control system configured to output a vehicle deceleration request corresponding to a required deceleration rate of the vehicle. The speed control system according to any one of claims 1 to 7.

9. The speed control system according to claim 8, wherein the vehicle deceleration request is configured to at least partially depend on the gradient of the running surface.

10. The speed control system according to claim 9, wherein the magnitude of the deceleration request is configured to increase in response to an increase in the gradient of the running surface.

11. The speed control system according to any one of claims 8 to 10, wherein the vehicle deceleration request depends at least partially on a user-selectable input indicating a desired level of passenger comfort.

12. A system for controlling the speed of a vehicle, The speed control system according to any one of claims 1 to 11; and One or more sensors configured to output signals indicating the following: The pitch of the vehicle and / or the rate of change of the pitch of the vehicle; and The gradient of the running surface.

13. A vehicle including the speed control system according to any one of claims 1 to 11 or the system according to claim 12.

14. A method for controlling the speed of a vehicle executed by a speed control system, including operating the vehicle according to a target speed value, the method further including, Receiving a pitch rate signal indicating the rate of change of the pitch attitude of the vehicle; Receiving a running surface gradient signal indicating the gradient of the running surface on which the vehicle is traveling; and Determining whether the vehicle has reached the summit based on the following: The rate of change of the pitch attitude exceeds a predetermined value; and The gradient value of the running surface is less than a predetermined value; A method including outputting a speed reduction signal for reducing the speed of the vehicle in response to the determination that the vehicle has reached the summit.

15. A non-transitory computer-readable storage medium that, when executed by one or more electronic processors, stores instructions that cause the one or more electronic processors to execute the method according to claim 14.

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