Device and method for controlling speed of vehicle on abrupt slope in off-road environment

Abstract

The invention discloses a device and method for controlling the speed of a vehicle on an abrupt slope in an off-road environment, and the method comprises the steps: monitoring the slope of a road at a fixed distance in front in real time when a low-speed off-road cruise function is activated in the running process of the vehicle; if the road gradient is greater than the set gradient, determining a steep slope road section, controlling the target vehicle speed to be a set safe vehicle speed based on the road gradient, and adjusting the distribution ratio of front and rear axle driving torque; if the road gradient is smaller than or equal to the set gradient, the vehicle speed is automatically controlled based on cross-country cruise; when the vehicle runs to the abrupt slope road section, the vehicle speed is controlled in different modes based on different positions of the abrupt slope road section where the vehicle runs, and vehicle speed control on the abrupt slope is achieved. The method can assist a driver in changing the vehicle speed and the vehicle driving state in a safe mode, and the situation that the driver feels uncomfortable or uncomfortable in the process is avoided.

Description

Technical Field

[0001] The invention belongs to the field of automobile technology, and in particular relates to a device and method for controlling vehicle speed on a steep slope in an off-road environment. Background Art

[0002] With the advancement of chassis technology, off-road vehicles developed in recent years have set corresponding terrain modes for different off-road conditions. In each terrain mode, the vehicle's power system, four-wheel drive system, body stability system, and suspension system are pre-calibrated and coordinated. When entering the target terrain, the driver drives the vehicle by reasonably controlling the accelerator pedal, brake pedal, and steering wheel. Experienced drivers can easily control the vehicle through complex off-road terrain.

[0003] However, when a vehicle is driving on an off-road road with bumps, potholes, steep slopes, etc., it is a challenge for drivers who lack driving experience, because they have to operate the accelerator pedal, brake pedal and steering wheel at the same time, which may easily cause personal injury or vehicle damage due to improper operation.

[0004] The invention of CN104583031B provides a method for operating a speed control system of a vehicle, the method comprising: a detection step, in which an external force acting on the vehicle is detected, wherein the external force has an accelerating or decelerating effect on the vehicle; an adjustment step, in which the rate of change of at least one component of the net torque being applied to one or more wheels of the vehicle is automatically adjusted to compensate for the accelerating or decelerating effect of the external force on the vehicle, wherein the adjustment step comprises applying a predetermined gain to the at least one component of the net torque being applied to the one or more wheels of the vehicle, thereby increasing or decreasing the rate of change of the at least one component of the net torque, the method further comprising A command is received to change the set speed of the speed control system from a first set speed to a lower target set speed, and wherein the adjustment step includes adjusting the rate of change of at least one component of the net torque being applied to decelerate the vehicle to the target set speed, wherein when the external force has a decelerating effect due to the vehicle climbing up a slope, and further wherein, in the case where the received command to change the set speed will result in a rate of change of at least one component of the net torque being applied such that the net torque will not be sufficient to keep the vehicle moving up the slope, the method further includes reducing the rate of change of at least one component of the net torque being applied to prevent the vehicle from moving down the slope. The problem of the vehicle sliding down the slope or rushing forward due to the lack of sufficient compensation for external forces caused by the slope when the target speed of the vehicle changes is solved, which may cause damage to personnel and the vehicle.

[0005] CN106660530B invention provides a method for operating an automatic speed control system of a vehicle according to a set speed, the method comprising: receiving at least one electrical signal representing a braking command initiated by a vehicle occupant to slow the vehicle to a stop; in response to the braking command, while maintaining the speed control system in an activated state, suspending the increase of the driving torque to the wheels of the vehicle for the duration of the braking command, and applying a retarding torque to one or more wheels of the vehicle to stop the vehicle; gradually reducing the driving torque from the driving torque level being applied when stopping the vehicle over time; receiving at least one electrical signal representing a brake release command initiated by a vehicle occupant; and in response to the brake release command, while maintaining the speed control system in an activated state, automatically commanding the generation of a driving torque sufficient to propel the vehicle in the intended direction of travel, and automatically controlling the speed of the vehicle according to the set speed. The problem that the driver may slide back on a slope due to overspeed parking and the problem that the restart system requires manual operation by the driver are solved.

[0006] Both of the above patents have the following problems:

[0007] 1. Failure to recognize steep slopes in advance;

[0008] 2. The vehicle speed will not automatically adjust according to the slope before going up or down a steep slope;

[0009] 3. The entire process of going up and down steep slopes cannot be handled in a targeted manner. Summary of the invention

[0010] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and to provide a vehicle speed control device and method on a steep slope in an off-road environment.

[0011] The technical solution adopted by the present invention is: a method for controlling vehicle speed on a steep slope in an off-road environment, when the low-speed off-road cruise function is activated during vehicle driving, the road slope at a fixed distance ahead is monitored in real time;

[0012] If the road slope is greater than the set slope, it is determined to be a steep slope section, and the target vehicle speed is controlled to be the set safe vehicle speed based on the road slope, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time;

[0013] If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on off-road cruise control;

[0014] When a vehicle reaches a steep slope, different methods are used to control the vehicle speed based on the different positions of the steep slope the vehicle enters, thereby achieving vehicle speed control on the steep slope.

[0015] Further, the low-speed off-road cruise function is activated by a low-speed off-road cruise function start switch and a low-speed off-road cruise function confirmation switch.

[0016] Furthermore, the road slope and the safe speed are based on:

[0017] When the road slope is greater than the set slope and less than or equal to the first slope threshold, the safe speed is A;

[0018] When the road slope is greater than the first slope threshold and less than or equal to the second slope threshold, the safe vehicle speed decreases linearly with the increase of the road slope;

[0019] The road slope is greater than the second slope threshold, and the safe speed is B.

[0020] Furthermore, the process of automatically controlling the vehicle speed based on off-road cruise is: collecting vehicle parameters in real time, determining the target acceleration and the target control speed according to the vehicle parameters, determining the torque required to control the vehicle's travel based on the target acceleration and the target control speed, and automatically controlling the vehicle speed by using speed closed-loop control according to the torque.

[0021] Furthermore, when the vehicle is driving on a steep slope, if it is detected that the driver intends to change the current vehicle speed, the driver controls the vehicle and limits the corresponding torque, including:

[0022] If the driver intends to reduce the speed when going uphill, the driving torque is controlled to be the minimum driving torque to prevent rolling down the slope;

[0023] If the driver intends to increase the vehicle speed when going uphill, the increase rate of the driving torque is controlled to be less than the set range;

[0024] If the driver intends to increase the vehicle speed when going downhill, the vehicle is accelerated by reducing the braking torque until the acceleration caused by the vehicle's gravity component is lower than a predetermined threshold.

[0025] Furthermore, the different positions of the steep slope section include an uphill bottom access point, and the vehicle speed is controlled and adjusted by compensating the driving torque.

[0026] Furthermore, the different positions of the steep slope section include an uphill slope top access point, and the vehicle speed is controlled and adjusted by reducing the driving torque.

[0027] Furthermore, the different positions of the steep slope section include a downhill slope top access point, and the vehicle speed is controlled and adjusted by reducing the driving torque and applying braking compensation at the same time.

[0028] Furthermore, the different positions of the steep slope section include a downhill bottom access point, and the vehicle is controlled to maintain the current braking until the vehicle posture is lower than a threshold angle and then the braking is released, and the vehicle speed is controlled to be lower than a set value when the braking is released.

[0029] Furthermore, when the vehicle rolls down a slope while traveling on an uphill section, the rolling can be improved by driver intervention or active application of braking force and redistribution of braking force on the front and rear axles.

[0030] A vehicle speed control device on a steep slope in an off-road environment, comprising:

[0031] Off-road cruise activation detection module, used to monitor whether the low-speed off-road cruise function is activated;

[0032] Slope detection module, used to monitor the slope of the road at a fixed distance ahead in real time when the low-speed off-road cruise function is activated;

[0033] The off-road cruise control module is used to determine the road slope. If the road slope is greater than the set slope, it is determined to be a steep slope section. Based on the road slope, the target vehicle speed is controlled to be the set safe speed, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time. If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on the off-road cruise. When the vehicle is driving on a steep slope section, it is used to control the vehicle speed in different ways based on the different positions of the steep slope section that the vehicle enters, so as to achieve vehicle speed control on the steep slope.

[0034] Furthermore, it also includes a driver intention recognition module, which is used to identify whether the driver intends to control the vehicle speed when the low-speed off-road cruise function is activated. If it is recognized that the driver intends to change the current vehicle speed, the driver controls the vehicle and at the same time limits the corresponding torque through the off-road cruise speed control module to control the vehicle speed.

[0035] The beneficial effects of the present invention are:

[0036] The present invention can activate the low-speed off-road cruise function in the off-road terrain mode. When encountering an uphill or downhill slope with a large slope change, the driver only needs to operate the steering wheel, and the system can timely reduce the actual vehicle speed, control the acceleration and deceleration, avoid vehicle overshoot, pass slowly, and avoid personal injury or vehicle damage caused by excessive speed; at the same time, if the driver intervenes on the slope, the system can also assist the driver to change the vehicle speed and vehicle driving status in a safe manner, avoiding the vehicle from making the driver feel uncomfortable or uneasy during this process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the principle of the control device of the present invention.

[0038] Figure 2 Flow chart of the control method of the present invention.

[0039] Figure 3 Schematic diagram of road slope recognition according to the present invention.

[0040] Figure 4It is a schematic diagram of the slope and safe speed of the present invention.

[0041] Figure 5 Schematic diagrams of different positions of the vehicle of the present invention when traveling on a steep slope.

[0042] Figure 6 The figure is a schematic diagram of the change of pitch rate when the vehicle of the present invention is traveling on a steep slope.

[0043] Figure 7 The figure is a schematic diagram of the change of the pitch angle when the vehicle of the present invention is traveling on a steep slope.

[0044] Figure 8 The figure is a schematic diagram of the change of the front and rear axle loads when the vehicle of the present invention is traveling on a steep slope.

[0045] Fig. 9 The figure is a schematic diagram of the change of the vertical force on the front and rear wheels when the vehicle of the present invention is traveling on a steep slope.

[0046] Fig.10 It is a schematic diagram of the vehicle of the present invention sliding down a slope when going uphill.

[0047] Fig.11 It is a schematic diagram of a vehicle of the present invention driving to an access point 2 on a steep slope.

[0048] Fig.12 It is a schematic diagram of the vehicle of the present invention driving to access point 2 on a steep slope and sliding down the slope.

[0049] Fig.13 This is a schematic diagram of the present invention showing that a vehicle driving on a steep slope identifies an access point 3 .

[0050] Fig.14 This is a schematic diagram of the present invention showing that a vehicle driving on a steep slope identifies an access point 4 .

[0051] Fig.15 It is a schematic diagram of the vehicle speed change when the vehicle of the present invention travels to the access point 4 on the steep slope. DETAILED DESCRIPTION

[0052] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] like Figure 1 As shown, the present invention provides a vehicle speed control device on a steep slope in an off-road environment, comprising

[0054] The off-road cruise activation detection module is used to monitor whether the low-speed off-road cruise function is activated when the vehicle is driving in off-road terrain mode;

[0055] The slope detection module is used to monitor the slope of the road at a fixed distance ahead in real time by receiving information such as vehicle speed, acceleration, drive torque, brake torque, gear position, and front wheel angle on the CAN bus when the low-speed off-road cruise function is activated;

[0056] The off-road cruise control module is used to determine the road slope. If the road slope is greater than the set slope, it is determined to be a steep slope section. Based on the road slope, the target vehicle speed is controlled to be the set safe vehicle speed, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time. If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on the off-road cruise. When the vehicle is driving on a steep slope section, the vehicle speed is controlled in different ways based on the different positions of the steep slope section that the vehicle enters, so as to achieve vehicle speed control on the steep slope. Specifically, it includes a road surface detection module, an up and down steep slope control module, a target vehicle speed setting module and a vehicle speed control module. Among them, the road surface detection module is used to determine the initial safe vehicle speed of the up and down steep slopes if the low-speed off-road cruise function is activated; the target vehicle speed setting module is used to set the target vehicle speed; the up and down steep slope control module is used to control the vehicle speed in combination with the vehicle speed control module when the vehicle is driving on a steep slope section.

[0057] The driver intention recognition module is used to identify whether the driver intends to control the vehicle speed when the low-speed off-road cruise function is activated. If it is recognized that the driver intends to change the current vehicle speed, the driver controls the vehicle and at the same time limits the corresponding torque through the off-road cruise speed control module to control the vehicle speed.

[0058] Based on the above control device, the present invention also provides a method for controlling vehicle speed on a steep slope in an off-road environment. Figure 2 As shown, when the low-speed off-road cruise function is activated during vehicle driving, the road slope at a fixed distance ahead is monitored in real time;

[0059] If the road slope is greater than the set slope, it is determined to be a steep slope section. The target vehicle speed is controlled to be the set safe vehicle speed based on the road slope, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time: on a steep slope on a flat ground, the proportion of the rear axle drive torque is gradually increased, while the proportion of the front axle drive torque is gradually reduced; if there is no sudden change in ground adhesion at the top of a steep slope, the proportion of the rear axle drive torque is gradually reduced, while the proportion of the front axle drive torque is gradually increased; if there is a sudden change in ground adhesion at the top of a steep slope, the proportion of the rear axle drive torque is appropriately reduced, while the proportion of the front axle drive torque is increased, or the distribution of the front and rear axle torques remains unchanged;

[0060] If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on off-road cruise control;

[0061] When a vehicle reaches a steep slope, different methods are used to control the vehicle speed based on the different positions of the steep slope the vehicle enters, thereby achieving vehicle speed control on the steep slope.

[0062] In the above scheme, the low-speed off-road cruise function is activated by the low-speed off-road cruise function on switch and the low-speed off-road cruise function confirmation switch. Specifically, when the vehicle is traveling in the off-road terrain mode, the off-road cruise activation monitoring module further detects whether the low-speed off-road cruise control function is in an activated state by detecting the activation signal of the low-speed off-road cruise control function. When the low-speed off-road cruise control function switch is pressed, the off-road cruise activation monitoring module determines that the driver intends to use the low-speed off-road cruise control. The driver further presses the confirmation switch, and the off-road cruise activation monitoring module confirms that the driver's low-speed off-road cruise control function is activated.

[0063] In the above scheme, the road slope and safe speed are based on:

[0064] When the road slope is greater than the set slope and less than or equal to the first slope threshold, the safe speed is A;

[0065] When the road slope is greater than the first slope threshold and less than or equal to the second slope threshold, the safe vehicle speed decreases linearly with the increase of the road slope;

[0066] When the road slope is greater than the second slope threshold, the safe speed is B, A>B, and A and B are both calibrated values.

[0067] In the above scheme, the process of automatically controlling the vehicle speed based on off-road cruise is: real-time collection of vehicle parameters, determination of target acceleration and target control speed based on the vehicle parameters, determination of the torque required to control the vehicle's travel based on the target acceleration and target control speed, and automatic control of the vehicle speed using speed closed-loop control based on the torque. The specific process is described later.

[0068] In the above scheme, when the vehicle is driving on a steep slope, if it is detected that the driver intends to change the current speed, the driver controls the vehicle and limits the corresponding torque, including:

[0069] If the driver intends to reduce the speed when going uphill, the driving torque is controlled to be the minimum driving torque to prevent rolling down the slope;

[0070] If the driver intends to increase the vehicle speed when going uphill, the increase rate of the driving torque is controlled to be less than the set range;

[0071] If the driver intends to increase the vehicle speed when going downhill, the vehicle is accelerated by reducing the braking torque until the acceleration caused by the vehicle's gravity component is lower than a predetermined threshold.

[0072] Specifically, if the low-speed off-road cruise function is turned on, the target working speed setting module sets the target speed, and the vehicle state and driving intention recognition module recognizes the vehicle driving state and the driver's intention, including:

[0073] If the low-speed off-road cruise function is activated, the target speed setting module sets the target working speed, including: the target working speed setting module sets a default target working speed according to the current off-road terrain mode and the gear position signal, and the driver can adjust the target working speed according to actual needs;

[0074] The driver can adjust the target working speed according to actual needs, including: adjusting the increase or decrease of the target working speed through the speed control switch device or lowering the target working speed through the brake pedal or raising the target speed through the accelerator pedal and the speed control switch.

[0075] The identifying of the vehicle driving state and the driver's intention by the driver intention identification module includes: acquiring the vehicle driving state and the driving intention by receiving the vehicle driving information.

[0076] The vehicle driving information includes a slope signal, a longitudinal acceleration signal, an accelerator pedal position signal, a front and rear axle driving torque requested by the driver, actual front and rear axle torque, a front and rear axle maximum allowable torque signal, a brake pedal signal, etc.

[0077] The obtaining of the vehicle driving state and driving intention includes: calculating the available driving torque of the front and rear axles and judging the driver's acceleration intention according to the accelerator pedal position signal, the front and rear axle driving torque requested by the driver, the actual torque of the front and rear axles, and the maximum allowable torque signal of the front and rear axles; judging the driver's deceleration intention according to the brake pedal signal; and calculating the slope change rate α' and the slope acceleration α" according to the slope signal α.

[0078] The step of taking over the vehicle control by the driver if the driver intends to accelerate includes: when the driver's requested torque is greater than or equal to the driving torque requested by the low-speed off-road cruise function, it is determined that the driver intends to accelerate, and at this time the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0079] The step of the driver taking over the vehicle control if the driver has a braking intention includes: when a brake pedal signal is monitored, it is determined that the driver has a deceleration request, and the driver controls the vehicle according to a control strategy preset by the off-road terrain control module.

[0080] If the driver has neither acceleration intention nor braking intention, the off-road cruise speed control module controls the actual vehicle speed, including: the off-road cruise speed control module calculates the target control speed and target acceleration according to the input signal, then calculates the required driving torque or braking torque, and sends a braking pressure or driving torque request to the braking control device or the driving control device to automatically control the vehicle.

[0081] In the above scheme, the different positions of the steep slope section include the uphill bottom access point, the uphill top access point, the downhill top access point and the downhill bottom access point. The identification of each access point and the vehicle speed and torque change adjustment are as follows:

[0082] Receive signals on the vehicle CAN bus, including vehicle pitch angle, pitch rate, vertical force at the center of each wheel, axle load, longitudinal acceleration and longitudinal speed.

[0083] If there is a sharp change in pitch rate, a continuous decrease in pitch angle (a negative change in uphill pitch angle), a decrease in the vertical force at the center of the front wheel, an increase in the vertical force at the center of the rear wheel, a decrease in the front axle load, an increase in the rear axle load, a large negative longitudinal acceleration, and a decreasing speed trend, it is recognized as the vehicle entering the uphill access point of the steep slope, i.e., access point 1. After identifying access point 1, the drive torque is compensated to control the speed fluctuation within a range that is difficult for the driver to detect subjectively. At the same time, if it is found that the safety control speed and front and rear axle torque distribution determined in the early stage are not appropriate during the process of crossing access point 1 to the full uphill, it can continue to adjust adaptively.

[0084] After going uphill, if the pitch angle continues to increase (the pitch angle changes to a negative value when going uphill), the vertical force at the center of the front wheel increases, the vertical force at the center of the rear wheel decreases, the front axle load increases, and the rear axle load decreases (increase and decrease here specifically refers to restoring the change of the corresponding signal caused by going uphill to the initial state before going uphill), the longitudinal acceleration appears to be a large positive value, and the speed tends to increase, then it is recognized that the vehicle begins to enter the access point from the steep slope to the top of the slope, that is, access point 2. After identifying access point 2, the driving torque is reduced to control the speed fluctuation within a range that is difficult for the driver to detect subjectively. After completely crossing access point 2 to the top of the slope for more than a certain set distance or time, the target vehicle speed set by the driver in the early stage and the front and rear axle torque distribution ratio in normal mode are gradually restored.

[0085] After the road detection module recognizes that the vehicle is about to go down a long slope, if the pitch rate changes dramatically, the pitch angle continues to increase, the vertical force at the center of the front wheel increases, the vertical force at the center of the rear wheel decreases, the front axle load increases, the rear axle load decreases, the longitudinal acceleration has a large positive value, and the speed tends to increase, it is recognized that the vehicle begins to enter the access point from the top of the slope to the downhill, that is, access point 3. After identifying access point 3, the driving torque is reduced, and braking compensation is applied at the same time to control the speed fluctuation within the range that the driver is difficult to detect subjectively. At the same time, the proportion of front axle braking force is increased, and the proportion of rear axle braking force is reduced, and the speed continues to be corrected according to the slope to the safe downhill speed corresponding to the slope.

[0086] After going downhill, if the pitch angle continues to decrease, the vertical force at the center of the front wheel increases, the vertical force at the center of the rear wheel decreases, the front axle load increases, the rear axle load decreases, the longitudinal acceleration shows a large negative value, and the speed tends to increase, it is recognized that the vehicle begins to enter the access point to the bottom of the downhill slope, that is, access point 4. After identifying access point 4, continue to brake until the vehicle posture is lower than the threshold angle, start to slowly release the brake, and ensure that the speed does not overshoot during this process, that is, it does not exceed the control safety control speed.

[0087] In the above scheme, when the vehicle rolls down a slope while driving on an uphill section, the rolling can be improved by driver intervention or active application of braking force and redistribution of braking force between the front and rear axles.

[0088] Example

[0089] This embodiment uses the following specific steps to describe the above control method in detail.

[0090] Step 101, the vehicle activates a low-speed off-road cruise function.

[0091] In the embodiment of the present invention, when the vehicle is traveling on an off-road terrain, the off-road cruise activation monitoring module further detects whether the low-speed off-road cruise control function is in an activated state by detecting an activation signal of the low-speed off-road cruise control function.

[0092] Among them, the off-road terrain mode management module receives the terrain mode switch signal or the road type and confidence signal of the binocular camera. The off-road terrain mode management module converts these signals into terrain mode request signals (DriveModreq) according to a certain logic and sends them to the CAN bus. Each subsystem receives the terrain mode request signal of the off-road terrain mode management module and completes the switching of their respective parameters, and then feeds back their respective status signals to the off-road terrain mode management module. The synchronized off-road terrain mode management module sends the terrain mode signal to the HMI display.

[0093] For example Figure 3 The vehicle shown has entered a certain off-road terrain mode. When the LSCC (Low Speed ​​Off-Road Cruise) switch is pressed, the low speed off-road cruise switch signal is sent to the off-road cruise activation monitoring module. The off-road cruise activation monitoring module determines that the driver intends to use the low speed off-road cruise control, and then sends a message to the HMI (Human Machine Interaction System) to prompt the driver to press the confirmation switch to activate the function. The driver presses the confirmation switch, and the off-road cruise activation monitoring module receives the confirmation switch signal to confirm the activation of the low speed off-road cruise function.

[0094] In actual applications, the low-speed off-road cruise function activation instruction can be generated and triggered by a low-speed off-road cruise function activation switch, which can be a physical button set on the vehicle or a virtual touch button set on the vehicle MP5. The embodiment of the present invention is not limited to this.

[0095] In actual applications, the confirmation instruction of the low-speed off-road cruise function can be generated and triggered by a low-speed off-road cruise function confirmation switch, which can be a physical button set on the vehicle or a virtual touch button set on the vehicle MP5, which is not limited in the embodiment of the present invention. The physical button can be a single button or a button multiplexed with other functions, which is not limited in the embodiment of the present invention.

[0096] Step 102, after the low-speed off-road cruise function is activated, the steep slope at a fixed distance L ahead is continuously identified;

[0097] In the embodiment of the present invention, the road detection module receives the signal sent by the visual system, monitors the steep slope that exceeds the set slope threshold at a fixed distance L in front of the vehicle's driving trajectory, and changes the target vehicle speed to a safe control speed according to the slope information. If it is recognized that a steep slope is about to be encountered ahead, the vehicle speed is adjusted and controlled in advance, which not only ensures driving safety in an off-road environment, but also conforms to actual driving habits and can reduce the driver's manual operation. In actual applications, the detection device of the visual system can be a binocular camera or an ultrasonic radar, or a combination of the two for joint detection, which is not limited in the embodiment of the present invention.

[0098] The method of determining the safe control speed according to the slope information can refer to Figure 4 The road surface detection module always monitors the road slope θ at a fixed distance L from the axle in front of the vehicle's driving trajectory. When θ≤the set slope, it is a safe working condition and the vehicle speed is not corrected. At this time, the vehicle speed is the target working speed set above; when the set slope is <θ≤the first slope threshold θ1, the safe speed is A; when θ>the second slope threshold θ2, the safe speed is B; when the first slope threshold is <θ≤the second slope threshold, the safe control speed decreases linearly with the increase of the slope; in actual applications, the safe control speed thresholds A and B can be changed according to the vehicle positioning, and the embodiments of the present invention are not limited to this.

[0099] Step 103: If no steep slope is detected ahead, the low-speed off-road cruise module continues to control the vehicle speed;

[0100] In the example of the present invention, the off-road cruise speed control module receives signals input from other modules, calculates target braking deceleration, target control speed and other signals, and sends braking pressure or driving torque requests to the braking control device or driving control device in a timely manner according to the current state of the vehicle and the control target, so as to automatically control the vehicle.

[0101] The vehicle speed V is controlled ctl The calculation is based on the correction coefficient K of the control speed and the target speed V initially set by the user. target To determine, V ctl =KV target ; where V ctl Adjust according to the following conditions: The next speed correction factor K n+1 >This speed correction coefficient K n When the target control speed V ctl According to K n+1 Adjustment; when K n+1 ≤K n When V ctl The obstacle remains unchanged until the vehicle has completely passed it.

[0102] The target acceleration a target The calculation is based on the off-road terrain mode signal and the gear position signal to set the basic acceleration a base , when the actual vehicle speed> control vehicle speed (V act >V ctl ), a base is a negative value, indicating deceleration; when V act >V ctl When base is a positive value, representing acceleration; when the slope change rate α′ exceeds the slope change rate threshold and the slope acceleration α″ exceeds the slope acceleration threshold, base On the basis of adding an additional deceleration offset, the target acceleration a target =a base +offset1;

[0103] The dynamic equation of the vehicle when driving is as follows:

[0104] M=(F R +F W +F St +F)r din Formula 1

[0105] in:

[0106] M-heading torque, when M is positive, it represents the driving torque, and when M is negative, it represents the braking torque

[0107] F R -Rolling resistance, F R =fmg, where f is the rolling resistance coefficient and m is the vehicle mass

[0108] F W - air resistance, where c wis the air resistance coefficient, A is the frontal area, ρ is the air density, and v is the vehicle speed;

[0109] F St - Slope resistance, F St = mgsinθ, where θ is the slope;

[0110] F-acceleration resistance, F=kma target , where k is the acceleration drag coefficient;

[0111] r din - wheel rolling radius;

[0112]

[0113] According to the signals from other modules such as the current ramp signal, the actual vehicle speed signal, and the target control vehicle speed signal and the target acceleration signal calculated by this module, the required torque M can be calculated by formula 2.

[0114] When M is positive, representing the driving torque, the off-road cruise speed control module sends a driving torque request for the front and / or rear axles to the power control unit, and uses speed closed-loop control to automatically control vehicle driving.

[0115] When M is negative, representing the braking torque, the off-road cruise speed control module automatically calls the active boost function of the brake hydraulic control unit and uses speed closed-loop control to automatically control vehicle driving.

[0116] Step 104, if it is recognized that a steep slope is about to be encountered ahead, in addition to adjusting the vehicle speed to a safe control speed, the distribution ratio of the front and rear axle drive torque is also adjusted;

[0117] In the example of the present invention, considering making full use of the ground adhesion conditions and enhancing the vehicle's climbing ability, the rear axle driving force ratio is increased and the front axle driving force ratio is reduced according to the detected slope signal. In actual applications, the specific allocation ratio can be specifically adjusted according to different vehicle model parameters, and the present invention is not limited to this.

[0118] Step 105, after identifying the uphill bottom access point, applying progressive drive torque compensation to prevent the vehicle speed from being drastically reduced due to encountering a steep slope;

[0119] In the example of the present invention, after the vehicle speed is changed to a safe speed in the step 102, the vehicle enters the steep slope condition at a safe speed. Within a number of control cycles, if the vehicle pitch rate changes drastically or exceeds a set threshold (here, the pitch angle rate is a negative change when going uphill, for example, from 0deg / s to -10deg / s), the vehicle pitch angle decreases by more than a set threshold (here, the pitch angle is a negative change when going uphill, for example, from 0deg to -20deg), the vertical force at the center of the front wheel decreases by more than a set threshold (for example, a decrease of 10%), the vertical force at the center of the rear wheel increases by more than a set threshold (for example, an increase of 10%), the front axle load decreases by more than a set threshold (for example, a decrease of 10%), and the rear axle load increases by more than a set threshold (for example, an increase of 10%), then it is identified as the vehicle starting to enter the bottom access point of the steep slope, that is, access point 1, see Figure 6-9 After the access point 1 is identified, the compensatory driving torque is applied according to Formula 3 according to the change in the road slope value, so as to control the vehicle speed fluctuation within a range that is difficult for the driver to perceive subjectively. In this example, the various chassis dynamics signal thresholds for identifying the access point 1 include but are not fixed to the example thresholds given in this example, and other thresholds are also optional.

[0120] M drv_θ =mgsinθ*r din Formula 3

[0121] Where M drv_θ is the compensated driving torque, θ is the slope in degrees (deg), r din is the wheel rolling radius.

[0122] In the process of crossing access point 1 to the complete uphill, the slope signal estimated in real time by the slope detection module is received. If it is found that the safety control vehicle speed and front and rear axle torque distribution determined before entering the steep slope are not appropriate, it can continue to adjust adaptively. Figure 5 The visual system predicts the slope and modifies the vehicle speed to the safe control speed for the first time. After the front wheels start to enter access point 1, the safe control speed is modified for the second time in combination with the accurate slope signal estimated in real time by the slope estimation module. If the first modified safe control speed is greater than the safe control speed corresponding to the real-time estimated slope signal, the safe control speed is further reduced to Figure 4 The corresponding value of the medium slope is to ensure that the vehicle crosses the slope at a speed that makes the driver feel safe and comfortable, reducing the driver's manual operation process. Regarding the adjustment of the front and rear axle torque distribution during the uphill process, an optional way to adjust according to the front and rear axle loads in this example is:

[0123]

[0124] Where, μ is the front axle torque distribution ratio, 1-μ is the rear axle torque distribution ratio, θ is the slope, the unit is angle (deg), F Z1 is the front axle load, F Z2 is the rear axle load, G is the vehicle gravity, a is the distance from the center of mass to the front axle, b is the distance from the center of mass to the rear axle, L is the wheelbase, h is g is the centroid height.

[0125] Step 106, during the uphill process, if the driver intends to accelerate or brake, the driver takes over the vehicle control;

[0126] In the example of the present invention, when the driver's requested torque is greater than or equal to the driving torque requested by the low-speed off-road cruise function, it is determined that the driver has an acceleration intention, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0127] In the example of the present invention, when the driver presses the set+ button, it is determined that the driver intends to accelerate, and the vehicle is controlled by the new speed set by the driver;

[0128] In the example of the present invention, when the brake pedal signal is detected to be set to 1 or the pedal travel sensor signal value is greater than the set threshold, it is determined that the driver has a deceleration request, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0129] In the example of the present invention, when the driver presses the set-button, it is determined that the driver intends to decelerate, and the vehicle is controlled at the new speed set by the driver;

[0130] If the driver has no intention to accelerate or brake, the off-road cruise speed control module continues to control the actual vehicle speed according to the safety control speed set in step 102 .

[0131] In practical application, the present invention only specifies two ways of determining the driver's intention, but is not limited to these two ways, as long as it can determine that the driver has changed the current vehicle speed.

[0132] Step 107, when the driver intends to change the current vehicle speed, the minimum driving torque to prevent rolling down the slope is maintained when the driving torque is reduced; when the driving torque is increased, the increase rate is controlled to keep the acceleration rate within the set threshold.

[0133] In the example of the present invention, the uphill and downhill steep slope control module receives signals from the vehicle status and driving intention recognition module. When it indicates that the driver has the intention to accelerate, the uphill and downhill steep slope control module controls the driving torque to increase slowly and controls the torque increase rate within the set threshold, thereby ensuring that the acceleration change is within the expected range.

[0134] When the driver indicates that he intends to slow down, the up and down steep slope control module controls the driving torque to slowly decrease, and the minimum torque value must not be lower than the torque value corresponding to the vehicle's gravity component caused by the slope to prevent the vehicle from moving in the opposite direction, that is, sliding down the slope.

[0135] In practical applications, the torque increase rate threshold and acceleration range may be designed according to the subjective feelings of different drivers, and the present invention is not limited thereto.

[0136] Step 108, identifying whether the vehicle has rolled down the slope during the uphill process, if it has rolled down the slope, go to step 109, if it has not rolled down the slope, go to step 112. Fig.10 As shown, the vehicle is moving on the slope in the direction opposite to the desired direction of movement.

[0137] Step 109, when rolling down a slope, determine whether the driver takes over the vehicle control through pedals and buttons. If the driver does not intervene in time, go to step 110; if the driver intervenes in time, go to step 111.

[0138] In the example of the present invention, the up and down steep slope control module will not work when the low-speed off-road cruise is manually turned off, in order to ensure that the driver's intention takes priority; it plays an auxiliary role when the driver intervenes through the accelerator pedal and the brake pedal.

[0139] Step 110, if the driver does not intervene in the slope control in time, the up and down steep slope control module automatically controls the braking torque value corresponding to the vehicle gravity component caused by the applied slope, and slowly reduces the driving torque. If the vehicle still does not stop sliding down the slope at this time, the braking torque continues to increase, and the braking force proportion of the front and rear axles is redistributed, specifically, the braking force proportion of the rear axle is increased and the braking force proportion of the front axle is reduced. An optional adjustment method refers to formula 4, increasing the braking torque proportion of the rear axle with a large axle load and reducing the braking torque proportion of the front axle with a small axle load.

[0140] If the driver has no intention to move forward for a certain period of time after the vehicle stops, the parking brake is automatically controlled to intervene. Here, the driver's intention to move forward includes but is not limited to the driver stepping on the accelerator pedal.

[0141] Step 111: If the driver intervenes in time, the driver will be allowed to control the vehicle.

[0142] Step 112, if there is no slipping during the uphill process, continue to control the vehicle speed to climb the slope according to the safe speed set in step 102. At the same time, receive the signal of the ground detection module, and continue to identify the slope change at a fixed distance ahead, the steps include;

[0143] In the embodiment of the present invention, the road detection module receives the signal sent by the visual system to monitor the access point 2 that exceeds the set slope change threshold at a fixed distance ahead of the vehicle's driving trajectory, see Fig.11 , detect the slope change point at L1 in front of the vehicle, and detect whether the ground can be detected at a distance L2 in front to identify the size of the slope change in advance.

[0144] If it is recognized that a steep slope access point is about to be encountered ahead, first check whether the current actual vehicle speed exceeds the preset safety control speed C. If it exceeds, reduce the speed to the safety control speed C in advance; if it does not exceed, maintain the current speed unchanged.

[0145] If no steep slope is detected ahead, the low-speed off-road cruise module will continue to control the vehicle speed;

[0146] By adjusting the vehicle speed in advance, driving safety in off-road environments is ensured, and it also complies with actual driving habits, which can reduce the driver's manual operation. In practical applications, the detection device of the visual system can be a binocular camera or an ultrasonic radar, or a combination of the two for joint detection, which is not limited in the embodiments of the present invention.

[0147] Step 113, identifying the slope change access point in real time based on the vehicle dynamics signal, and controlling the vehicle speed, torque, and front and rear axle torque distribution ratio;

[0148] The steep slope control module can automatically identify the special access point of the steep slope, and the steps include:

[0149] Receive signals on the vehicle CAN bus, including vehicle pitch angle, pitch rate, vertical force at the center of each wheel, axle load, longitudinal acceleration and longitudinal speed.

[0150] After going uphill, within several control cycles, if the pitch rate changes drastically or exceeds the set threshold (for example, from 0deg / s to 10deg / s), the pitch angle increases by more than the set threshold (for example, from -20deg to 0deg), the vertical force at the center of the front wheel increases by more than the set threshold (for example, increases by 10%), the vertical force at the center of the rear wheel decreases by more than the set threshold (for example, decreases by 10%), the front axle load increases by more than the set threshold (for example, increases by 10%), and the rear axle load decreases by more than the set threshold (for example, decreases by 10%) (increase and decrease here specifically refers to restoring the change of the corresponding signal caused by going uphill to the initial state before going uphill), it is recognized as the vehicle starting to enter the access point to the top of the steep slope, that is, access point 2. For a schematic diagram of parameter changes, see Figure 6-9 In this example, the chassis dynamics signal thresholds for identifying access point 2 include but are not fixed to the example thresholds given in this example, and other thresholds are also optional.

[0151] The step of timely and continuously adjusting the vehicle speed, torque change, and front and rear axle driving force distribution ratio according to the real-time slope value includes:

[0152] When access point 2 is identified, the system first checks whether the current actual vehicle speed exceeds the preset safety control speed C. If it exceeds, the vehicle speed is reduced to the safety control speed C in advance. If it does not exceed, the current vehicle speed is maintained unchanged. As the road slope changes, the driving torque is reduced according to formula 2 to control the speed fluctuation within a range that is difficult for the driver to detect subjectively.

[0153] When the front wheels enter the access point, the distribution of the driving torque between the front and rear axles is adjusted according to the real-time slope change, gradually increasing the proportion of the front axle driving torque and reducing the proportion of the rear wheel driving torque. An optional way to adjust according to the change of the road slope value is shown in Formula 4.

[0154] When the distance or time from the access point to the top of the slope exceeds a certain set distance or time, the target vehicle speed set by the driver before going uphill and not modified according to the slope is gradually restored. At the same time, the driving torque is slowly applied, the braking compensation torque is released, and the acceleration change is controlled within the set range.

[0155] Step 114, during the uphill process, if the driver intends to accelerate or brake, the driver takes over the vehicle control;

[0156] In the example of the present invention, when the driver's requested torque is greater than or equal to the driving torque requested by the low-speed off-road cruise function, it is determined that the driver has an acceleration intention, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0157] In the example of the present invention, when the driver presses the set+ button, it is determined that the driver intends to accelerate, and the vehicle is controlled by the new speed set by the driver;

[0158] In the example of the present invention, when the brake pedal signal is detected to be set to 1 or the pedal travel sensor signal value is greater than the set threshold, it is determined that the driver has a deceleration request, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0159] In the example of the present invention, when the driver presses the set-button, it is determined that the driver intends to decelerate, and the vehicle is controlled at the new speed set by the driver;

[0160] If the driver has no intention to accelerate or brake, the process goes to step 116 , where the off-road cruise speed control module continues to control the actual vehicle speed; otherwise, the process goes to step 115 .

[0161] In practical application, the present invention only specifies two ways of determining the driver's intention, but is not limited to these two ways, as long as it can determine that the driver has changed the current vehicle speed.

[0162] Step 115, when the driver intervenes, controls the torque change rate and acceleration change range, including:

[0163] If the driver reduces the speed by pressing the button when crossing the access point, the maximum reduction of the driving torque must at least maintain the torque value corresponding to the slope to prevent the vehicle from rolling back. Fig.12 ;

[0164] If the driver steps on the brake pedal when crossing the access point, when the applied braking torque does not reach the torque value corresponding to the real-time slope, the driving torque is maintained to ensure that the vehicle has a net torque value that is at least the torque value corresponding to the slope; when the applied torque value is greater than the torque value corresponding to the real-time slope, the driving torque is slowly reduced to ensure that the vehicle does not slide down the slope;

[0165] If the driver increases the vehicle speed by pressing a button when crossing the access point, the rate of increase of the drive torque must be within the set range to control the acceleration within the preset range to ensure smooth acceleration;

[0166] If the driver steps on the accelerator pedal when crossing the access point, the rate of increase of the drive torque must be within the set range to control the acceleration within the preset range to ensure smooth acceleration;

[0167] In practical applications, the torque increase rate threshold and acceleration range may be designed according to the subjective feelings of different drivers, and the present invention is not limited thereto.

[0168] Step 116, detecting whether the ground adhesion coefficient changes, includes:

[0169] The steep slope control module receives the ground adhesion coefficient signal from the ground detection module. The ground detection module is not limited to receiving the perception signal of the visual system, and can also receive other sensor signals of the vehicle through the CAN bus to estimate the change of the ground adhesion coefficient experienced by the wheel. The present invention does not limit the adhesion coefficient identification method in practical application. If it is identified that the front wheel is experiencing the ground with a change in adhesion condition, then go to step 117, otherwise the steep slope control module continues to control the vehicle to move forward, and go to step 118.

[0170] Step 117, when the ground adhesion condition changes, controls the torque change rate and acceleration change range, including:

[0171] If the front wheel's road adhesion suddenly decreases and the wheel tends to slip, stop increasing the front axle drive torque distribution ratio and appropriately increase the rear axle torque distribution ratio; when the rear wheel crosses the access point, restore the front and rear axle drive torque distribution ratio on flat roads, and then adjust the front and rear axle drive torque distribution ratio in real time according to the changes in ground adhesion conditions experienced by the front and rear wheels, so as to enhance the vehicle's ability to overcome slippage and pass steep slope access points.

[0172] Step 118, to ensure that the vehicle completely reaches the top of the slope and crosses the access point 2, only after detecting that the rear wheels completely cross the access point 2 and have traveled for a period of time, will the initial target vehicle speed set by the driver before going uphill be gradually restored.

[0173] In the example of the present invention, the uphill and downhill steep slope control module receives signals from the ground detection module, the slope estimation module and the target speed setting module. After recognizing that a steep slope is about to be climbed, the vehicle speed is first reduced to the safe control speed. After recognizing the uphill access point 1, the safe control speed will continue to be adjusted according to the real-time slope during the formal uphill process. Therefore, during the uphill process, the actual vehicle speed tracks the safe control speed, not the target speed set by the user. After the uphill is completed, the uphill and downhill steep slope control module will gradually restore the controlled speed to the target speed initially set by the driver. In practical applications, there is no specific restriction on the speed recovery rate.

[0174] Step 119, the ground detection module receives the signal from the visual system. It is easy to detect the raised obstacles and steep slopes ahead, but it is not easy to detect the depth of the depression ahead and the slope of a long steep slope. Therefore, it is impossible to determine the safe control speed for downhill driving based on the preview slope value. The only thing to do is to reduce the speed to the safe control speed C if the vehicle speed is above the preset safe control speed C when it is detected that the vehicle is about to go down a long steep slope. If the vehicle speed is below the safe control speed C, the current speed is maintained unchanged.

[0175] In the present example, referring to Fig.13 , showing a schematic diagram of the method for detecting a long steep slope. The ground detection module identifies the sudden change point of the ground slope at the front L1. At a farther distance L2, if the ground is detected, the downhill slope ahead is a short downhill slope, or a downhill slope with a small slope change, or a gentle shell crater-like terrain, and there is no need to change the vehicle speed in advance; if the ground cannot be detected at L2, it means that the downhill slope ahead is a long steep slope, and it is necessary to check in advance whether the vehicle speed meets the safety control speed C of the steep slope. If not, it needs to be reduced to the safety control speed C in advance. In actual application, the present invention does not limit the specific value of the downhill safety control speed C, nor does it limit the detection distance value of the ground detection module.

[0176] Step 120 , after identifying the downhill access point 3 , actively apply sufficient braking force to keep the vehicle speed from overshooting, and adjust the braking force distribution of the front and rear axles at the same time.

[0177] In this embodiment, after the road detection module recognizes that a long slope is about to be descended, within several control cycles, if the pitch rate changes drastically or exceeds a set threshold (for example, increases from 0deg / s to 10deg / s), the pitch angle increases by more than a set threshold (from 0deg to 20deg), the vertical force at the center of the front wheel increases by more than a set threshold (for example, increases by 19%), the vertical force at the center of the rear wheel decreases by more than a set threshold (for example, decreases by 19%), the front axle load increases by more than a set threshold (for example, increases by 19%), and the rear axle load decreases (for example, decreases by 19%), then it is recognized that the vehicle begins to enter the access point of descending from the top of the slope, that is, access point 3, see Figure 6-9 At t3. After identifying access point 3, according to the change in the road slope value, the driving torque is reduced to 0, and braking compensation is applied at the same time (refer to formula 3) to control the vehicle speed fluctuation within a range that is difficult for the driver to detect subjectively. In this example, the various chassis dynamics signal thresholds for identifying access point 3 include but are not fixed to the example thresholds given in this example, and other thresholds are also optional. At the same time, the proportion of front axle braking force is increased, and the proportion of rear axle braking force is reduced, and the vehicle speed continues to be corrected according to the slope to a safe downhill speed corresponding to the slope. Ensure that the ground adhesion conditions are fully utilized when going down a steep slope to maintain a stable vehicle speed. In this example, an optional adjustment method for downhill braking torque distribution can refer to formula 4, increasing the proportion of braking torque of the front axle with a large axle load, and reducing the proportion of braking torque of the rear axle with a small axle load.

[0178] Step 121, whether the driver adjusts the vehicle speed or steps on the pedal to override during the downhill process. If it is determined that the driver intends to change the vehicle speed, jump to step 122, if not, directly jump to step 123.

[0179] In the example of the present invention, when the driver's requested torque is greater than or equal to the driving torque requested by the low-speed off-road cruise function, it is determined that the driver has an acceleration intention, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0180] In the example of the present invention, when the driver presses the set+ button, it is determined that the driver intends to accelerate, and the vehicle is controlled by the new speed set by the driver;

[0181] In the example of the present invention, when the brake pedal signal is detected to be set to 1 or the pedal travel sensor signal value is greater than the set threshold, it is determined that the driver has a deceleration request, and the driver controls the vehicle according to the control strategy preset by the off-road terrain control module;

[0182] In the example of the present invention, when the driver presses the set-button, it is determined that the driver intends to decelerate, and the vehicle is controlled at the new speed set by the driver;

[0183] If the driver has no intention to accelerate or brake, the off-road cruise speed control module will continue to control the actual vehicle speed.

[0184] In practical application, the present invention only specifies two ways of determining the driver's intention, but is not limited to these two ways, as long as it can determine that the driver has changed the current vehicle speed.

[0185] Step 122 : When the driver intends to accelerate, the vehicle is accelerated by reducing part of the braking force through the gravity component.

[0186] In the present invention, during the acceleration process on a steep downhill slope, the braking force is not allowed to be completely withdrawn, nor is it allowed to accelerate the vehicle by applying a de-driving torque. During the acceleration process of the vehicle by reducing the braking torque, the acceleration is ensured to be within a set range to ensure slow acceleration and to ensure that there is no acceleration process that makes the driver feel uneasy.

[0187] Step 123 , when the access point 4 is recognized by preview and dynamics, the braking is maintained until the vehicle posture is lower than the threshold angle, and the braking begins to be slowly released, and it is ensured that the speed does not overshoot during this process.

[0188] In the example of the present invention, the road detection module always monitors the slope θ at a fixed distance L from the axle in front of the vehicle's driving trajectory. When θ<the third slope threshold θ3, it can be considered that the front is about to encounter the access point 4, that is, the downhill is about to end and the flat ground is encountered. Fig.14 .

[0189] In the example of the present invention, after going downhill, within several control cycles, if the pitch rate changes drastically or exceeds a set threshold (for example, from 0 deg / s to -10 deg / s), the pitch angle decreases by more than a set threshold (for example, from 20 deg to 0 deg / s), the vertical force at the center of the front wheel decreases by more than a set threshold (for example, decreases by 19%), the vertical force at the center of the rear wheel increases by more than a set threshold (for example, increases by 19%), the front axle load decreases by more than a set threshold (for example, decreases by 19%), and the rear axle load increases by more than a set threshold (for example, increases by 19%), then it is recognized that the vehicle begins to enter the access point to the bottom of the downhill slope, that is, access point 4, see Figure 6-9 At t4. After identifying access point 4, continue to brake until the vehicle posture is lower than the threshold angle, start to slowly release the brake, and ensure that the speed does not overshoot during this process, that is, it does not exceed the control safety control speed. After the rear wheels have completely reached the bottom of the slope for more than a certain time or distance, gradually restore the target speed set by the user before going downhill. In this example, the various chassis dynamics signal thresholds for identifying access point 4 include but are not fixed to the example thresholds given in this example, and other thresholds are also optional.

[0190] Reference Fig.15, shows the change in speed of method 100 during the process of crossing access point 4 and crossing the process from downhill to the bottom of the slope. At time t4, the front wheels of the vehicle begin to encounter access point 4. Since the brakes need to be maintained, the acceleration caused by the gravity component decreases during the process of the slope becoming gentle, and the vehicle speed begins to decrease; at time t5, the vehicle posture is lower than the threshold angle, the brakes begin to be slowly released, and the vehicle speed begins to increase; at time t6, the vehicle completely descends to the bottom of the slope, and the driving torque begins to be slowly applied to track the target vehicle speed set by the driver.

[0191] In practical applications, the present invention does not impose specific numerical restrictions on the above-mentioned parameters such as the set threshold value and the threshold angle.

[0192] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A method for controlling vehicle speed on a steep slope in an off-road environment, characterized in that: When the low-speed off-road cruise function is activated during vehicle driving, the road slope at a fixed distance ahead is monitored in real time; If the road slope is greater than the set slope, it is determined to be a steep slope section, and the target vehicle speed is controlled to be the set safe vehicle speed based on the road slope, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time; If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on off-road cruise control; When a vehicle reaches a steep slope, different methods are used to control the vehicle speed based on the different positions of the steep slope the vehicle enters, thereby achieving vehicle speed control on the steep slope.

2. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The road slope and safe speed are based on: When the road slope is greater than the set slope and less than or equal to the first slope threshold, the safe speed is A; When the road slope is greater than the first slope threshold and less than or equal to the second slope threshold, the safe vehicle speed decreases linearly with the increase of the road slope; The road slope is greater than the second slope threshold, and the safe speed is B.

3. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The process of automatically controlling the vehicle speed based on off-road cruise control is: collecting vehicle parameters in real time, determining the target acceleration and the target control speed according to the vehicle parameters, determining the torque required to control the vehicle driving based on the target acceleration and the target control speed, and automatically controlling the vehicle speed by using speed closed-loop control according to the torque.

4. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: When the vehicle is driving on a steep slope, if it is detected that the driver intends to change the current speed, the driver will control the vehicle and limit the corresponding torque, including: If the driver intends to reduce the speed when going uphill, the driving torque is controlled to be the minimum driving torque to prevent rolling down the slope; If the driver intends to increase the vehicle speed when going uphill, the increase rate of the driving torque is controlled to be less than the set range; If the driver intends to increase the vehicle speed when going downhill, the vehicle is accelerated by reducing the braking torque until the acceleration caused by the vehicle's gravity component is lower than a predetermined threshold.

5. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The different positions of the steep slope section include an uphill bottom access point, and the vehicle speed is controlled and adjusted by compensating the driving torque.

6. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The different positions of the steep slope section include an uphill slope top access point, and the vehicle speed is controlled and adjusted by reducing the driving torque.

7. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The different positions of the steep slope section include a downhill slope top access point, and the vehicle speed is controlled and adjusted by reducing the driving torque and applying braking compensation.

8. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: The different positions of the steep slope section include a downhill bottom access point, and the vehicle is controlled to maintain the current braking until the vehicle posture is lower than a threshold angle and then the braking is released. When the braking is released, the vehicle speed is controlled to be lower than a set value.

9. The method for controlling vehicle speed on a steep slope in an off-road environment according to claim 1, characterized in that: When a vehicle rolls down a slope while driving on an uphill road, the rolling situation can be improved by driver intervention or by actively applying braking force and redistributing the braking force on the front and rear axles.

10. A vehicle speed control device on a steep slope in an off-road environment, characterized in that: include Off-road cruise activation detection module, used to monitor whether the low-speed off-road cruise function is activated; Slope detection module, used to monitor the slope of the road at a fixed distance ahead in real time when the low-speed off-road cruise function is activated; The off-road cruise control module is used to determine the road slope. If the road slope is greater than the set slope, it is determined to be a steep slope section. Based on the road slope, the target vehicle speed is controlled to be the set safe speed, and the distribution ratio of the front and rear axle drive torque is adjusted at the same time. If the road slope is less than or equal to the set slope, the vehicle speed is automatically controlled based on the off-road cruise. When the vehicle is driving on a steep slope section, it is used to control the vehicle speed in different ways based on the different positions of the steep slope section that the vehicle enters, so as to achieve vehicle speed control on the steep slope.

Images