Vehicle body stability control method and device and vehicle

Abstract

The invention discloses a vehicle body stability control method and device and a vehicle, the vehicle body stability control method is applied to a four-wheel-drive vehicle, and for each wheel, the method comprises the steps that when vehicle braking is detected, a braking torque request of the wheel is obtained; according to the braking torque request, the control state of the current vehicle is judged; wherein when the anti-lock control system and the vehicle body stability control system are triggered at the same time, the brake torque values of the anti-lock control system and the vehicle body stability control system are compared; and the smaller braking torque value in the two braking torque values is used for carrying out braking control on the wheels. According to the vehicle body stability control method and device and the vehicle, anti-lock control, traction control and vehicle body stability control are mixed through optimization of the control priority, and the safety of a driver is guaranteed to the maximum extent within the physical limit of the vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control, and particularly to a vehicle body stability control method, device and vehicle. Background Art

[0002] With the continuous enrichment of materials, people's pursuit of vehicle functions is getting higher and higher, the requirements for driving performance and driving pleasure are increasing day by day, the driving conditions are becoming more intense and the scenario applications are also increasing; at the same time, automobile manufacturers are also constantly increasing the functional requirements for vehicles, and improving the safety performance of vehicle body stability and the driving control performance. Therefore, the stability, controllability and safety of vehicle driving become more important.

[0003] Currently, with the rapid development of electric vehicles, the power, transmission and braking devices are integrated into the wheels through in-wheel motors, and control systems for multiple different scenarios are applied to vehicles in combination with power, transmission and braking. However, the multi-system control in multiple scenarios makes the whole vehicle control process less smooth, the safety will also be reduced, and at the same time, the driving experience of users is also reduced. Summary of the Invention

[0004] The purpose of the present invention is to provide a vehicle body stability control method, device and vehicle, which can perform priority overall control on the multi-functional control system to achieve the purposes of vehicle driving stability, controllability and safety.

[0005] According to the first aspect of the embodiments of the present invention, a vehicle body stability control method is provided, which is applied to a four-wheel drive vehicle. For each wheel, the method includes:

[0006] When it is detected that the vehicle brakes, obtain the braking torque request of the wheel;

[0007] Judge the control state of the current vehicle according to the braking torque request;

[0008] Among them, when the anti-lock braking system (ABS) and the vehicle stability control system (VSC) are triggered simultaneously, compare the braking torque values of the two; and perform braking control on the wheel with the smaller braking torque value of the two.

[0009] A further improvement of the method of the present invention is that in the anti-lock braking system, the method includes:

[0010] Obtain the wheel slip rate of the vehicle;

[0011] Calculate the wheel slip rate deviation according to the wheel slip rate;

[0012] When the wheel slip rate is greater than zero, obtain the braking torque value according to the slip rate deviation and through the PID control algorithm;

[0013] Among them, the formula of the PID control algorithm is as follows:

[0014]

[0015] Among them, the u(t) brake is the braking torque, the K1 is the initial value of the PID control, and the K p1 is the coefficient calibration value of the proportional part, and the K i1 is the coefficient calibration value of the integral part, and the K d1 is the coefficient calibration value of the differential part, and the e(t) is the wheel slip rate deviation value.

[0016] A further improvement of the method of the present invention is that the method further includes:

[0017] Judging whether braking control is established simultaneously for two front wheels or two rear wheels;

[0018] If so, restricting the braking torque on the high-adhesion side of two front wheels or two rear wheels;

[0019] If not, controlling the four wheels to perform braking control according to the braking torque requests of the four wheels.

[0020] A further improvement of the method of the present invention is that in the vehicle stability control system, the method includes:

[0021] Obtaining the actual yaw rate of the vehicle;

[0022] Calculating the reference yaw rate of the vehicle according to the actual steering angle of the front wheels;

[0023] Comparing the reference yaw rate with the actual yaw rate;

[0024] Among them, if the absolute value of the reference yaw rate is less than the absolute value of the actual yaw rate, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0025] A further improvement of the method of the present invention is that the method further includes:

[0026] When it is detected that the vehicle reduces torque, obtaining the drive torque request of the wheels;

[0027] Judging the control state of the current vehicle according to the drive torque request;

[0028] Among them, when the traction control system and the vehicle stability control system are triggered simultaneously, comparing the drive torque values of the two; and performing drive control on the wheels with the smaller drive torque value of the two.

[0029] A further improvement of the method of the present invention lies in that in the traction control system, the method includes:

[0030] Obtain the wheel slip ratio of the vehicle;

[0031] Calculate the wheel slip ratio deviation according to the wheel slip ratio;

[0032] When the wheel slip ratio is less than or equal to zero, obtain the driving torque value of traction control according to the slip ratio deviation and through the PID control algorithm;

[0033] Wherein, the formula of the PID control algorithm is:

[0034]

[0035] Wherein, the u(t) drive is the braking torque, the K2 is the initial value of the PID control, the K p2 is the coefficient calibration value of the proportional part, the K i2 is the coefficient calibration value of the integral part, the K d2 is the coefficient calibration value of the differential part, and e(t) is the wheel slip ratio deviation value.

[0036] A further improvement of the method of the present invention lies in that the method further includes:

[0037] Judge whether two front wheels or two rear wheels are on a split road surface;

[0038] If so, correct the slip threshold of the high-adhesion side among the two front wheels or two rear wheels;

[0039] If not, control the four wheels to perform driving control according to the driving torque requests of the four wheels.

[0040] A further improvement of the method of the present invention lies in that in the vehicle stability control system, the method includes:

[0041] Obtain the actual yaw rate of the vehicle;

[0042] Calculate the reference yaw rate of the vehicle according to the actual steering angle of the front wheels;

[0043] Compare the reference yaw rate with the actual yaw rate;

[0044] Wherein, if the absolute value of the reference yaw rate is greater than or equal to the absolute value of the actual yaw rate, obtain the braking torque value of the vehicle through the PID control algorithm.

[0045] According to a second aspect of an embodiment of the present invention, a vehicle body stability control method is provided, which is applied to a four-wheel drive vehicle. For each wheel, the method includes:

[0046] When it is detected that the vehicle reduces torque, obtain the drive torque request of the wheel;

[0047] According to the drive torque request, judge the control state of the current vehicle;

[0048] Wherein, when the traction control system and the vehicle body stability control system are triggered simultaneously, compare the drive torque values of the two, and use the smaller drive torque value of the two to perform drive control on the wheel.

[0049] A further improvement of the method of the present invention is that the method further includes:

[0050] When it is detected that the vehicle brakes, obtain the braking torque request of the wheel;

[0051] According to the braking torque request, judge the control state of the current vehicle;

[0052] Wherein, when the anti-lock braking system and the vehicle body stability control system are triggered simultaneously, compare the braking torque values of the two, and use the smaller braking torque value of the two to perform braking control on the wheel.

[0053] According to a third aspect of an embodiment of the present invention, a vehicle body stability control device is provided, which is applied to a four-wheel drive vehicle. For each wheel, the device includes:

[0054] A first acquisition module, configured to obtain the braking torque request of the wheel when it is detected that the vehicle brakes;

[0055] A first judgment module, configured to judge the control state of the current vehicle according to the braking torque request;

[0056] A first processing module, configured to compare the braking torque values of the two when the anti-lock braking system and the vehicle body stability control system are triggered simultaneously, and use the smaller braking torque value of the two to perform braking control on the wheel.

[0057] According to a fourth aspect of an embodiment of the present invention, a vehicle body stability control device is provided, which is applied to a four-wheel drive vehicle. For each wheel, the device includes:

[0058] A second acquisition module, configured to obtain the drive torque request of the wheel when it is detected that the vehicle reduces torque;

[0059] A second judgment unit, configured to judge the control state of the current vehicle according to the drive torque request;

[0060] A second processing module, configured to compare the drive torque values of a traction control system and a vehicle stability control system when both are triggered simultaneously, and perform drive control on the wheel with the smaller drive torque value of the two.

[0061] According to a fifth aspect of an embodiment of the present invention, a vehicle is provided, including a controller and four motor controllers communicatively connected to the controller. The four motor controllers are configured to independently control four wheels, and the controller is configured to execute the vehicle stability control method described in any one of the above.

[0062] The vehicle stability control method, device and vehicle provided by the present invention realize the integration of anti-lock control, traction control and vehicle stability control through the optimization of control priorities, and ensure the safety of the driver to the greatest extent within the physical limits of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be described in detail below with reference to the accompanying drawings via exemplary embodiments, where:

[0064] Figure 1 A flowchart showing a vehicle stability control method provided by an embodiment of the present invention;

[0065] Figure 2 A flowchart showing a vehicle stability control method provided by another embodiment of the present invention;

[0066] Figure 3 A flowchart showing a vehicle stability control method provided by another embodiment of the present invention;

[0067] Figure 4 A flowchart showing a vehicle stability control method provided by another embodiment of the present invention;

[0068] Figure 5 A flowchart showing a vehicle stability control method provided by another embodiment of the present invention;

[0069] Figure 6 A block diagram showing the structure of a vehicle stability control device provided by an embodiment of the present invention;

[0070] Figure 7 A block diagram showing the structure of a vehicle stability control device provided by another embodiment of the present invention;

[0071] Figure 8 A block diagram showing the structure of a vehicle stability control device provided by another embodiment of the present invention;

[0072] Figure 9 A block diagram showing the structure of a vehicle stability control device provided by another embodiment of the present invention;

[0073] Figure 10A structural block diagram of a vehicle body stability control device provided by another embodiment of the present invention is shown.

[0074] The accompanying drawings are only schematic and are not necessarily drawn to scale. In addition, they only show those parts necessary to illustrate the present invention, while other parts may be omitted or only briefly mentioned. That is, in addition to the components shown in the drawings, the present invention may also include other components. Detailed implementation manners

[0075] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention will be introduced in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this implementation manner. On the contrary, the purpose of introducing the invention in conjunction with the implementation manner is to cover other alternatives or modifications that may be extended based on the claims of the present invention. To provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention can also be implemented without using these details. In addition, to avoid confusing or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0076] It should be noted that in this specification, similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0077] In the description of this embodiment, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "inner", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0078] Terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0079] In the description of this embodiment, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this embodiment can be understood according to specific situations.

[0080] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0081] Figure 1 The flowchart of a vehicle body stability control method provided by an embodiment of the present invention is shown.

[0082] Refer to Figure 1 In the vehicle body stability control method of the embodiment of the present invention, it is applied to a four-wheel drive vehicle, which includes a controller and four motor controllers communicatively connected to the controller. The controller is used to execute the vehicle body stability control method of the present invention, and the four motor controllers are used to independently control four wheels. Each wheel is equipped with a hub motor, and the motor controller is used to control the hub motor to perform traction control or braking control on the wheel.

[0083] The vehicle body stability control method of the present invention is directed to each wheel, and the vehicle body stability control method includes:

[0084] S101. When it is detected that the vehicle brakes, obtain the braking torque request of the wheel.

[0085] S102. Judge the control state of the current vehicle according to the braking torque request.

[0086] S103. When the anti-lock braking system (ABS) and the vehicle stability control (VSC) system are triggered simultaneously, compare the braking torque values of the two; and perform braking control on the wheel with the smaller braking torque value of the two.

[0087] In this embodiment, when the braking of the anti-lock braking control and the vehicle stability control are triggered simultaneously, in order to ensure that the wheel does not lock, the smaller braking value of the anti-lock braking system and the vehicle stability control system is taken. In the embodiment of the present invention, the braking values of the anti-lock braking system and the vehicle stability control system are implemented by the PID (Proportional Integral Derivative) control algorithm, which will be described in detail below.

[0088] As Figure 2 shown, in the anti-lock braking system, the vehicle body stability control method of the present invention includes:

[0089] S201. Obtain the wheel slip ratio of the vehicle.

[0090] S202. Calculate the wheel slip ratio deviation according to the wheel slip ratio.

[0091] S203. When the wheel slip ratio is greater than zero, obtain the braking torque value according to the slip ratio deviation and through the PID control algorithm.

[0092] In this embodiment, first, the slip ratio of the wheel is calculated. The absolute value of the wheel slip ratio is taken, and the calculation formula for the absolute value of the wheel slip ratio is:

[0093]

[0094] where ω w is the angular velocity of the wheel, u w is the reference vehicle speed of the vehicle. The reference vehicle speed is obtained by correcting and calculating through lateral and longitudinal acceleration sensors, and r r0 is the rolling radius of the wheel.

[0095] In the step of calculating the wheel slip ratio deviation, the wheel slip ratio deviation of the present invention is the difference between the absolute value of the wheel slip ratio and the optimal slip value. When the wheel slip ratio is greater than zero, the braking torque value is obtained according to the slip ratio deviation and through the PID control algorithm. Among them, the PID control algorithm formula is:

[0096]

[0097] where u(t) brake is the braking torque, K1 is the initial value of the PID control, K p1 is the coefficient calibration value of the proportional part, K i1 is the coefficient calibration value of the integral part, K d1 is the coefficient calibration value of the differential part, and e(t) is the wheel slip ratio deviation value.

[0098] Furthermore, the vehicle body stability control method of the present invention further includes:

[0099] Judging whether braking control is established simultaneously for two front wheels or two rear wheels; if so, restricting the braking torque of the high-adhesion side among the two front wheels or two rear wheels; if not, controlling the four wheels to perform braking control according to the braking torque requests of the four wheels.

[0100] In one embodiment, it is pre-judged whether braking control is established simultaneously for two front wheels. If so, the braking torque of the high-adhesion side among the two front wheels is restricted to achieve braking balance on both sides and prevent the yaw torque generated by left and right braking. If not, the four wheels are controlled to perform braking control according to the braking torque requests of the four wheels. When the two front wheels satisfy the condition of simultaneously establishing braking control, it is judged whether braking control is established simultaneously for two rear wheels. If so, the braking torque of the high-adhesion side among the two rear wheels is restricted to achieve braking balance on both sides and prevent the yaw torque generated by left and right braking. If not, the four wheels are controlled to perform braking control according to the braking torque requests of the four wheels.

[0101] As Figure 3 shown, in the vehicle body stability control system, the vehicle body stability control method of the present invention includes:

[0102] S301. Obtain the actual yaw rate of the vehicle.

[0103] S302. Calculate the reference yaw rate of the vehicle according to the actual steering angle of the front wheels.

[0104] S303. Compare the reference yaw rate with the actual yaw rate; wherein, if the absolute value of the reference yaw rate is less than the absolute value of the actual yaw rate, obtain the braking torque value of the vehicle through the PID control algorithm.

[0105] In this embodiment, the measured yaw rate is obtained through the sensors on the vehicle, and according to the two-degree-of-freedom vehicle motion differential equation, the reference yaw rate ω at this time is calculated through the actual steering angle of the front wheels (the actual steering angle of the front wheels is converted from the actual steering angle of the steering wheel). r .

[0106]

[0107] In the formula:

[0108] m′ = muI Z

[0109] h = -[m(a 2 k1 + b 2 k2) + I Z (k1 + k2)]

[0110]

[0111] b1 = -muak1

[0112] b0 = Lk1k2

[0113] Among them, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, k1 is the front wheel cornering stiffness value, k2 is the rear wheel cornering stiffness value, I Z is the moment of inertia about the Z axis, L is the wheelbase between the front axle and the rear axle, u is the longitudinal speed at the vehicle's center of mass, v is the lateral speed at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel angle at the vehicle's center of mass.

[0114] Then compare the reference yaw rate with the actual yaw rate. Among them, it is necessary to first judge whether the absolute value of the difference between the absolute value of the reference yaw rate and the absolute value of the actual yaw rate satisfies being less than the vehicle speed stability control entry threshold, that is, if it is satisfied, further judge the absolute value of the reference yaw rate and the absolute value of the actual yaw rate, that is: ||ω r |-|ω actual||<Δ3. If the absolute value of the reference yaw rate is less than the absolute value of the actual yaw rate, obtain the braking torque value of the vehicle through the PID control algorithm.

[0115] Furthermore, the vehicle body stability control method of the present invention further includes: when it is detected that the vehicle reduces torque, obtain the driving torque request of the wheel; according to the driving torque request, judge the control state of the current vehicle; wherein, when the traction control system and the vehicle body stability control system are triggered simultaneously, compare the driving torque values of the two; and perform driving control on the wheel with the smaller driving torque value of the two.

[0116] In this vehicle body control system, the traction control system and the vehicle body stability control system will not be triggered simultaneously. For each vehicle of the present invention, if the anti-lock braking control system and the vehicle stability control system are braked simultaneously, take the smaller value, so as to make the pressure on the wheel small and ensure that the wheel does not lock. If the traction control system and the torque request (torque reduction) of the vehicle body stability control are triggered simultaneously, take the smaller value, so as to make more torque that meets the request and the vehicle is more stable.

[0117] In the traction control system, the vehicle body stability control method of the present invention includes: obtaining the wheel slip ratio of the vehicle;

[0118] According to the wheel slip ratio, calculate the wheel slip ratio deviation; when the wheel slip ratio is less than or equal to zero, obtain the driving torque value of the traction control through the slip ratio deviation and the PID control algorithm;

[0119] Among them, the PID control algorithm formula is:

[0120]

[0121] Among them, u(t) drive is the braking torque, K2 is the initial value of the PID control, K p2 is the coefficient calibration value of the proportional part, K i2 is the coefficient calibration value of the integral part, K d2 is the coefficient calibration value of the differential part, and e(t) is the wheel slip ratio deviation value.

[0122] In this embodiment, first calculate the wheel slip ratio, and take the absolute value of the wheel slip ratio. The absolute value calculation formula of the wheel slip ratio is:

[0123]

[0124] Among them, ω w is the angular velocity of the wheel, u w is the reference vehicle speed of the vehicle, and the reference vehicle speed is obtained by correcting and calculating through the lateral and longitudinal acceleration sensors, r r0 is the wheel rolling radius.

[0125] In the step of calculating the slip rate deviation of the wheel, the wheel slip rate deviation of the present invention is the difference between the absolute value of the wheel slip rate and the optimal slip value. When the wheel slip rate satisfies being not greater than zero, the braking torque value is obtained according to the slip rate deviation through the PID control algorithm. Among them, the PID control algorithm formula is:

[0126]

[0127] Among them, u(t) brake is the braking torque, K2 is the initial value of the PID control (calibratable), K p2 is the coefficient calibration value of the proportional part, K i2 is the coefficient calibration value of the integral part, K d2 is the coefficient calibration value of the differential part, and e(t) is the wheel slip rate deviation value.

[0128] Furthermore, the vehicle body stability control method of the present invention further includes: judging whether two front wheels or two rear wheels are on a split road surface; if so, correcting the slip threshold of the high-adhesion side among the two front wheels or two rear wheels; if not, controlling the four wheels to perform drive control according to the drive torque requests of the four wheels.

[0129] In an embodiment, it is pre-judged whether two front wheels are on a split road surface. If so, the optimal slip threshold of the high-adhesion side is corrected (i.e., reduced), because when on a split road surface, it is necessary to use the high-adhesion road surface to accelerate, and the wheels on the high-adhesion side cannot have large slips. If not, the torque reduction request for the four wheels is executed. When the two front wheels are on a split road surface, it is judged whether two rear wheels are on a split road surface. If so, the optimal slip threshold of the high-adhesion side is corrected (i.e., reduced), because when on a split road surface, it is necessary to use the high-adhesion road surface to accelerate, and the wheels on the high-adhesion side cannot have large slips. If not, the torque reduction request for the four wheels is executed.

[0130] As Figure 4 shown, in the vehicle body stability control system, the vehicle body stability control method includes:

[0131] S401. Obtain the actual yaw rate of the vehicle.

[0132] S402. Calculate the reference yaw rate of the vehicle according to the actual steering angle of the front wheels.

[0133] S403. Compare the reference yaw rate with the actual yaw rate. Among them, if the absolute value of the reference yaw rate is greater than or equal to the absolute value of the actual yaw rate, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0134] In this embodiment, the measured yaw rate is obtained through the sensors on the vehicle. According to the two-degree-of-freedom vehicle motion differential equation, the reference yaw rate ω at this time is calculated through the actual front wheel angle (the actual front wheel angle is converted from the actual steering wheel angle). r .

[0135]

[0136] In the formula:

[0137] m′ = muI Z

[0138] h = -[m(a 2 k1 + b 2 k2) + I Z (k1 + k2)]

[0139]

[0140] b1 = -muak1

[0141] b0 = Lk1k2

[0142] Wherein, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, k1 is the front wheel cornering stiffness value, k2 is the rear wheel cornering stiffness value, I Z is the moment of inertia about the Z-axis, L is the wheelbase between the front axle and the rear axle, u is the longitudinal speed at the vehicle's center of mass, v is the lateral speed at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel angle at the vehicle's center of mass.

[0143] Then, the reference yaw rate is compared with the actual yaw rate. Among them, it is necessary to first determine whether the absolute value of the difference between the absolute value of the reference yaw rate and the absolute value of the actual yaw rate satisfies being less than the vehicle speed stability control entry threshold, that is, if it is satisfied, then further determine the absolute value of the reference yaw rate and the absolute value of the actual yaw rate, that is: ||ω r | - |ω actual || < Δ3. If the absolute value of the reference yaw rate is less than the absolute value of the actual yaw rate, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0144] As Figure 5 shown, in another aspect of the embodiment of the present invention, a vehicle body stability control method is also proposed. This method is applied to four-wheel drive vehicles. For each wheel, the vehicle body stability control method of the present invention includes:

[0145] S501. When it is detected that the vehicle reduces torque, obtain the drive torque request of the wheel.

[0146] S502. Determine the control state of the current vehicle according to the driving torque request.

[0147] S503. When the traction control system and the vehicle stability control system are triggered simultaneously, compare the driving torque values of the two, and perform driving control on the wheels with the smaller driving torque value of the two.

[0148] Further, the vehicle stability control method further includes: when it is detected that the vehicle is braking, obtain the braking torque request of the wheels; determine the control state of the current vehicle according to the braking torque request; wherein, when the anti-lock braking system and the vehicle stability control system are triggered simultaneously, compare the braking torque values of the two, and perform braking control on the wheels with the smaller braking torque value of the two.

[0149] In this embodiment, when the braking of the anti-lock braking control and the vehicle stability control is triggered simultaneously, in order to make the vehicle more stable, take the smaller one of the driving torque values of the anti-lock braking system and the vehicle stability control system. The more the torque reduction requested, the more stable the vehicle will be when driving.

[0150] As Figure 6 shown, the present invention also provides a vehicle stability control device, which is applied to a four-wheel drive vehicle. For each wheel, the device includes:

[0151] The first acquisition module 601 is used to obtain the braking torque request of the wheels when it is detected that the vehicle is braking;

[0152] The first judgment module 602 is used to determine the control state of the current vehicle according to the braking torque request;

[0153] The first processing module 603 is used to compare the braking torque values of the two when the anti-lock braking system and the vehicle stability control system are triggered simultaneously, and perform braking control on the wheels with the smaller braking torque value of the two.

[0154] In this embodiment, when the braking of the anti-lock braking control and the vehicle stability control is triggered simultaneously, in order to ensure that the wheels do not lock, take the smaller one of the braking values of the anti-lock braking system and the vehicle stability control system. In the embodiments of the present invention, the braking values of the anti-lock braking system and the vehicle stability control system are implemented by the PID (Proportional Integral Derivative) control algorithm, which will be described in detail below.

[0155] As Figure 7 shown, in the anti-lock braking system, the vehicle stability control device of the present invention includes:

[0156] The second acquisition module 701 is used to obtain the wheel slip rate of the vehicle.

[0157] The first calculation module 702 is configured to calculate the slip rate deviation of the wheel according to the slip rate of the wheel.

[0158] The second processing module 703 is configured to, when the slip rate of the wheel is greater than zero, obtain the braking torque value according to the slip rate deviation and through the PID control algorithm.

[0159] In this embodiment, first, the slip rate of the wheel is calculated. The absolute value of the slip rate of the wheel is taken. The calculation formula for the absolute value of the slip rate of the wheel is:

[0160]

[0161] where ω w is the angular velocity of the wheel, u w is the reference vehicle speed of the vehicle, which is obtained by correcting and calculating through lateral and longitudinal acceleration sensors, and r r0 is the rolling radius of the wheel.

[0162] In the step of calculating the slip rate deviation of the wheel, the slip rate deviation of the wheel in the present invention is the difference between the absolute value of the slip rate of the wheel and the optimal slip value. When the slip rate of the wheel is greater than zero, the braking torque value is obtained according to the slip rate deviation and through the PID control algorithm. Among them, the PID control algorithm formula is:

[0163]

[0164] where u(t) brake is the braking torque, K1 is the initial value of the PID control, K p1 is the coefficient calibration value of the proportional part, K i1 is the coefficient calibration value of the integral part, K d1 is the coefficient calibration value of the differential part, and e(t) is the slip rate deviation value of the wheel.

[0165] Furthermore, the vehicle body stability control device of the present invention further includes:

[0166] A judgment module, configured to judge whether braking control is established simultaneously for two front wheels or two rear wheels; if so, limit the braking torque of the high-adhesion side among the two front wheels or two rear wheels; if not, control the four wheels to perform braking control according to the braking torque requests of the four wheels.

[0167] In one embodiment, it is pre - judged whether the braking control is established for both front wheels simultaneously. If so, the braking torque on the high - adhesion side of the two front wheels is restricted to achieve braking balance on both sides and prevent the yaw torque generated by left - right braking. If not, the braking control of the four wheels is performed according to the braking torque requests of the four wheels. When the two front wheels meet the condition of simultaneously establishing braking control, it is judged whether the braking control is established for both rear wheels simultaneously. If so, the braking torque on the high - adhesion side of the two rear wheels is restricted to achieve braking balance on both sides and prevent the yaw torque generated by left - right braking. If not, the braking control of the four wheels is performed according to the braking torque requests of the four wheels.

[0168] As Figure 8 shown, in the vehicle stability control system, the vehicle stability control device of the present invention includes:

[0169] A third acquisition module 801, configured to acquire the actual yaw angular velocity of the vehicle.

[0170] A second calculation module 802, configured to calculate the reference yaw angular velocity of the vehicle according to the actual steering angle of the front wheels.

[0171] A third processing module 803, configured to compare the reference yaw angular velocity with the actual yaw angular velocity; wherein, if the absolute value of the reference yaw angular velocity is less than the absolute value of the actual yaw angular velocity, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0172] In this embodiment, the measured yaw angular velocity is obtained through the sensors on the vehicle, and according to the two - degree - of - freedom vehicle motion differential equation, the reference yaw angular velocity ω at this time is calculated through the actual steering angle of the front wheels (the actual steering angle of the front wheels is converted from the actual steering angle of the steering wheel). r .

[0173]

[0174] In the formula:

[0175] m ′ = muI Z

[0176] h = -[m(a 2 k1 + b 2 k2)+I Z (k1 + k2)]

[0177]

[0178] b1 = -muak1

[0179] b0 = Lk1k2

[0180] Wherein, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, k1 is the front wheel cornering stiffness value, k2 is the rear wheel cornering stiffness value, I Z is the moment of inertia about the Z-axis, L is the wheelbase between the front axle and the rear axle, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0181] Then, the reference yaw angular velocity is compared with the actual yaw angular velocity. Among them, it is necessary to first judge whether the absolute value of the difference between the absolute value of the reference yaw angular velocity and the absolute value of the actual yaw angular velocity satisfies being less than the vehicle speed stability control entry threshold, that is, if it is satisfied, then further judge the absolute value of the reference yaw angular velocity and the absolute value of the actual yaw angular velocity, that is: ||ω r |-|ω actual || < Δ3. If the absolute value of the reference yaw angular velocity is less than the absolute value of the actual yaw angular velocity, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0182] Furthermore, the vehicle body stability control device of the present invention further includes: when it is detected that the vehicle reduces torque, obtaining the driving torque request of the wheel; judging the control state of the current vehicle according to the driving torque request; wherein, when the traction control system and the vehicle body stability control system are triggered simultaneously, comparing the driving torque values of the two; and performing driving control on the wheels with the smaller driving torque value of the two.

[0183] In this vehicle body control system, the traction control system and the vehicle body stability control system will not be triggered simultaneously. For each vehicle of the present invention, if the anti-lock braking control system and the vehicle stability control system brake are triggered simultaneously, the smaller value is taken, so as to make the pressure on the wheels small and ensure that the wheels do not lock. If the traction control system and the torque request (torque reduction) of the vehicle body stability control are triggered simultaneously, the smaller value is taken, so as to make the more torque reduction that meets the request and the vehicle is more stable.

[0184] In the traction control system, the vehicle body stability control method of the present invention includes: obtaining the wheel slip ratio of the vehicle;

[0185] According to the wheel slip ratio, calculating the wheel slip ratio deviation; when the wheel slip ratio is less than or equal to zero, obtaining the driving torque value of the traction control through the PID control algorithm according to the slip ratio deviation;

[0186] Among them, the PID control algorithm formula is:

[0187]

[0188] Among them, u(t) driveis the braking torque, K2 is the initial value of PID control, K p2 is the coefficient calibration value of the proportional part, K i2 is the coefficient calibration value of the integral part, K d2 is the coefficient calibration value of the derivative part, and e(t) is the wheel slip rate deviation value.

[0189] In this embodiment, first, the slip rate of the wheel is calculated. The absolute value of the wheel slip rate is taken, and the calculation formula for the absolute value of the wheel slip rate is:

[0190]

[0191] where ω w is the angular velocity of the wheel, u w is the reference vehicle speed of the vehicle, and this reference vehicle speed is obtained by correcting and calculating through lateral and longitudinal acceleration sensors, r r0 is the rolling radius of the wheel.

[0192] In the step of calculating the wheel slip rate deviation, the wheel slip rate deviation of the present invention is the difference between the absolute value of the wheel slip rate and the optimal slip value. When the wheel slip rate is not greater than zero, the braking torque value is obtained according to the slip rate deviation and through the PID control algorithm. Among them, the PID control algorithm formula is:

[0193]

[0194] where u(t) brake is the braking torque, K2 is the initial value (calibratable) of PID control, K p2 is the coefficient calibration value of the proportional part, K i2 is the coefficient calibration value of the integral part, K d2 is the coefficient calibration value of the derivative part, and e(t) is the wheel slip rate deviation value.

[0195] Furthermore, the vehicle body stability control device of the present invention further includes: determining whether two front wheels or two rear wheels are on a split road surface; if so, correcting the slip threshold of the high-adhesion side among the two front wheels or two rear wheels; if not, controlling the four wheels to perform drive control according to the drive torque requests of the four wheels.

[0196] In one embodiment, it is pre-determined whether the two front wheels are on a split road surface. If so, the optimal slip threshold on the high-grip side is corrected (i.e., reduced), because when on a split road surface, it is necessary to use the high-grip road surface to accelerate, and the wheels on the high-grip side cannot have large slips. If not, a torque reduction request for all four wheels is executed. When the two front wheels are on a split road surface, it is determined whether the two rear wheels are on a split road surface. If so, the optimal slip threshold on the high-grip side is corrected (i.e., reduced), because when on a split road surface, it is necessary to use the high-grip road surface to accelerate, and the wheels on the high-grip side cannot have large slips. If not, a torque reduction request for all four wheels is executed.

[0197] As Figure 9 shown, in the vehicle stability control system, the vehicle stability control device includes:

[0198] A fourth acquisition module 901, configured to acquire the actual yaw rate of the vehicle.

[0199] A third calculation module 902, configured to calculate the reference yaw rate of the vehicle according to the actual steering angle of the front wheels.

[0200] A fourth processing module 903, configured to compare the reference yaw rate with the actual yaw rate. Among them, if the absolute value of the reference yaw rate is greater than or equal to the absolute value of the actual yaw rate, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0201] In this embodiment, the measured yaw rate is obtained through the sensors on the vehicle, and according to the two-degree-of-freedom vehicle motion differential equation, the reference yaw rate ω at this time is calculated through the actual steering angle of the front wheels (the actual steering angle of the front wheels is converted from the actual steering angle of the steering wheel). r .

[0202]

[0203] In the formula:

[0204] m ′ = muI Z

[0205] h = -[m(a 2 k1 + b 2 k2) + I Z (k1 + k2)]

[0206]

[0207] b1 = -muak1

[0208] b0 = Lk1k2

[0209] Wherein, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, k1 is the front wheel cornering stiffness value, k2 is the rear wheel cornering stiffness value, I Z is the moment of inertia about the Z-axis, L is the wheelbase between the front axle and the rear axle, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0210] Then, the reference yaw angular velocity is compared with the actual yaw angular velocity. Among them, it is necessary to first determine whether the absolute value of the difference between the absolute value of the reference yaw angular velocity and the absolute value of the actual yaw angular velocity satisfies being less than the vehicle speed stability control entry threshold, that is, if it is satisfied, then further determine the absolute value of the reference yaw angular velocity and the absolute value of the actual yaw angular velocity, that is: ||ω r |-|ω actual || < Δ3. If the absolute value of the reference yaw angular velocity is less than the absolute value of the actual yaw angular velocity, the braking torque value of the vehicle is obtained through the PID control algorithm.

[0211] As Figure 10 shown, in another aspect of the embodiment of the present invention, a vehicle body stability control device is also proposed. This device is applied to four-wheel drive vehicles. For each wheel, the vehicle body stability control device of the present invention includes:

[0212] The fifth acquisition module 1001 is used to acquire the drive torque request of the wheel when it is detected that the vehicle reduces torque.

[0213] The judgment module 1002 is used to judge the control state of the current vehicle according to the drive torque request.

[0214] The fifth processing module 1003 is used to compare the drive torque values of the traction control system and the vehicle body stability control system when both are triggered simultaneously, and perform drive control on the wheel with the smaller drive torque value of the two.

[0215] Furthermore, the vehicle body stability control device further includes: when it is detected that the vehicle brakes, acquiring the braking torque request of the wheel; judging the control state of the current vehicle according to the braking torque request; wherein, when the anti-lock braking system and the vehicle body stability control system are triggered simultaneously, comparing the braking torque values of the two, and performing braking control on the wheel with the smaller braking torque value of the two.

[0216] In this embodiment, when the braking of the anti-lock control and the vehicle body stability control is triggered simultaneously, in order to make the vehicle more stable, take the smaller drive torque value of the anti-lock braking system and the vehicle body stability control system. The more the requested torque reduction, the more stable the vehicle travels.

[0217] The vehicle body stability control method, device and vehicle provided by the present invention realize the integration of anti-lock control, traction control and vehicle body stability control through the optimization of control priorities, and ensure the safety of the driver to the greatest extent within the physical limits of the vehicle.

[0218] Although the present invention has been illustrated and described by referring to some preferred embodiments thereof, those of ordinary skill in the art should understand that the above content is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. Those skilled in the art can make various changes in form and details, including making several simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A vehicle body stability control method is applied to a four-wheel drive vehicle, characterized in that, For each wheel, the method includes: When vehicle braking is detected, obtain the braking torque request of the wheel; Based on the braking torque request, determine the control state of the current vehicle; Wherein, when the anti-lock braking system (ABS) and the vehicle stability control system (VSC) are triggered simultaneously, compare the braking torque values of the two; and perform braking control on the wheel with the smaller of the two braking torque values.

2. The method according to claim 1, wherein In the anti-lock braking system, the method includes: Obtain the wheel slip ratio of the vehicle; Based on the wheel slip ratio, calculate the wheel slip ratio deviation; When the wheel slip ratio is greater than zero, obtain the braking torque value based on the slip ratio deviation and through a PID control algorithm; Wherein, the formula of the PID control algorithm is: wherein, the u(t) brake is the braking torque, the K1 is the initial value of the PID control, and the K p1 is the coefficient calibration value of the proportional part, and the K i1 is the coefficient calibration value of the integral part, the K d1 is the coefficient calibration value of the derivative part, and e(t) is the wheel slip rate deviation value.

3. The method according to claim 2, wherein The method further includes: Determine whether braking control is established simultaneously for two front wheels or two rear wheels; If so, limit the braking torque of the high-adhesion side of the two front wheels or two rear wheels; If not, based on the braking torque requests of the four wheels, control the four wheels to perform braking control.

4. The method according to claim 1, wherein In the vehicle stability control system, the method includes: Obtain the actual yaw rate of the vehicle; Based on the actual steering angle of the front wheels, calculate the reference yaw rate of the vehicle; Compare the reference yaw rate with the actual yaw rate; Wherein, if the absolute value of the reference yaw rate is less than the absolute value of the actual yaw rate, obtain the braking torque value of the vehicle through a PID control algorithm.

5. The method according to claim 1, characterized in that, The method further includes: When vehicle torque reduction is detected, obtain the driving torque request of the wheel; Based on the driving torque request, determine the control state of the current vehicle; Wherein, when the traction control system (TCS) and the vehicle stability control system (VSC) are triggered simultaneously, compare the driving torque values of the two; and perform driving control on the wheel with the smaller of the two driving torque values.

6. The method according to claim 5, characterized in that In the traction control system, the method includes: Obtain the wheel slip ratio of the vehicle; Based on the wheel slip ratio, calculate the wheel slip ratio deviation; When the wheel slip ratio is less than or equal to zero, obtain the driving torque value for traction control based on the slip ratio deviation and through a PID control algorithm; Wherein, the formula of the PID control algorithm is: wherein, the u(t) drive is the braking torque, the K2 is the initial value of the PID control, and the K p2 is the coefficient calibration value of the proportional part, and the K i2 is the coefficient calibration value of the integral part, the K d2 is the coefficient calibration value of the derivative part, and the e(t) is the wheel slip rate deviation value.

7. The method according to claim 6, wherein The method further includes: Determine whether two front wheels or two rear wheels are on a split friction road surface; If so, correct the slip threshold of the high-adhesion side of the two front wheels or two rear wheels; If not, based on the driving torque requests of the four wheels, control the four wheels to perform driving control.

8. The method according to claim 5, wherein In the vehicle stability control system, the method includes: Obtain the actual yaw rate of the vehicle; Based on the actual steering angle of the front wheels, calculate the reference yaw rate of the vehicle; Compare the reference yaw rate with the actual yaw rate; Wherein, if the absolute value of the reference yaw rate is greater than or equal to the absolute value of the actual yaw rate, obtain the braking torque value of the vehicle through a PID control algorithm.

9. A vehicle body stability control method is applied to a four-wheel drive vehicle, characterized in that, For each wheel, the method includes: When vehicle torque reduction is detected, obtain the driving torque request of the wheel; Based on the driving torque request, determine the control state of the current vehicle; Wherein, when the traction control system and the vehicle stability control system are triggered simultaneously, the drive torque values of the two are compared, and the wheel is driven and controlled with the smaller drive torque value of the two.

10. The method according to claim 9, characterized in that The method further includes: When it is detected that the vehicle brakes, obtaining a braking torque request of the wheel; Judging the control state of the current vehicle according to the braking torque request; Wherein, when the anti-lock braking system and the vehicle stability control system are triggered simultaneously, the braking torque values of the two are compared, and the wheel is braked and controlled with the smaller braking torque value of the two.

11. A vehicle body stability control device is applied to a four-wheel drive vehicle, characterized in that, For each wheel, the device includes: A first obtaining module, configured to obtain a braking torque request of the wheel when it is detected that the vehicle brakes; A first judging module, configured to judge the control state of the current vehicle according to the braking torque request; A first processing module, configured to compare the braking torque values of the two when the anti-lock braking system and the vehicle stability control system are triggered simultaneously, and brake and control the wheel with the smaller braking torque value of the two.

12. A vehicle body stability control device is applied to a four-wheel drive vehicle, characterized in that For each wheel, the device includes: A second obtaining module, configured to obtain a drive torque request of the wheel when it is detected that the vehicle reduces torque; A second judging unit, configured to judge the control state of the current vehicle according to the drive torque request; A second processing module, configured to compare the drive torque values of the two when the traction control system and the vehicle stability control system are triggered simultaneously, and drive and control the wheel with the smaller drive torque value of the two.

13. A vehicle, characterized in that, Four motor controllers including a controller and communicatively connected to the controller, the four motor controllers are used to independently control four wheels, and the controller is used to execute the vehicle stability control method according to any one of claims 1-10.

Images