Automobile chassis domain unified yaw motion control method and device based on three-step method

Abstract

The invention belongs to the technical field of vehicle chassis coordination control, and particularly relates to an automobile chassis domain unified yaw motion control method and device based on a three-step method. Comprising the following steps: calculating a required yaw target; sensor, vehicle state and road surface information are acquired, and internal information resource sharing is realized; fault failure recognition of software and hardware is achieved, and corresponding driving safety is guaranteed. Aiming at an automobile of a four-wheel steering distributed driving electric automobile, a yaw stability integrated control system of a chassis domain based on a three-step method is designed; distributing the additional yawing moment, and distributing the additional yawing moment to four rounds for execution; and executing the distributed yawing moment control instruction and executing a front and rear wheel turning angle command to realize expected vehicle yawing dynamic control. Based on intelligent driving requirements of L2 + and above levels, the dynamic performance and the handling stability of the vehicle are improved, and the problem that yaw control in a traditional drive-by-wire chassis system is insufficient is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle chassis coordinated control, and in particular to a method and device for unified yaw motion control of a vehicle chassis domain based on a three-step method. Background Art

[0002] With the rapid development of autonomous driving and the gradual maturity of the intelligent assisted driving systems independently developed by automobile companies, the chassis domain architecture has emerged and gradually developed on the basis of chassis electronic control. The new chassis domain architecture and the chassis control technology under the chassis domain architecture have become one of the relevant hot spots. As a very important yaw control in vehicle dynamics control, the control based on a single electronic system has been quite mature, and the control interference and coupling problems of multiple electronic control systems under the chassis domain architecture will become more prominent with the development of the chassis domain.

[0003] For yaw control, the active front-wheel steering system and the active rear-wheel steering system achieve the desired steering. Due to the steering of the tires, the tire force will change, which will naturally help the car to establish additional yaw torque under certain working conditions. With the development of distributed drive vehicles, the four-wheel vehicles driven independently by wheel hub motors have brought more possibilities. The independent control of the torque of the four tires brings the freedom of each wheel to change the torque individually. As a result, the research on torque vector control system has emerged, which applies additional yaw torque to the vehicle through differential drive to help steering. The control objectives of the two systems are basically the same in the yaw problem, but the actuators are completely different. The working areas of the two systems are limited. Therefore, it is necessary to develop integrated control for yaw motion. Summary of the invention

[0004] The present invention provides a unified yaw motion control method and device for the automobile chassis domain based on a three-step method, which improves the vehicle's dynamic performance and handling stability based on the intelligent driving requirements of L2+ and above levels, and solves the problem of insufficient yaw control in traditional wire-controlled chassis systems.

[0005] The technical solution of the present invention is described as follows in conjunction with the accompanying drawings: In a first aspect, the present invention provides a method and device for unified yaw motion control in the chassis domain of an automobile based on a three-step method, comprising the following steps: Calculate yaw target; Obtain sensor, vehicle status, and road information to achieve internal information resource sharing; Identify software and hardware failures to ensure driving safety; For four-wheel steering distributed drive electric vehicles, a chassis domain yaw stability integrated control system based on a three-step method is designed to obtain the yaw moment and the front and rear wheel angle additional values, and send the front and rear wheel angle additional values ​​to the vehicle; Distribute the yaw moment and distribute it to the four wheels for execution; The allocated yaw moment control command is executed, as well as the front and rear wheel angle additional value commands to achieve the expected vehicle yaw dynamic control.

[0006] Furthermore, the specific method for calculating the yaw target is as follows: 11) Design the ideal center of mass sideslip angle ; 12) Design the ideal yaw rate as follows: Calculate the front and rear tire slip angles of a distributed drive four-wheel steering vehicle as follows: ; (1) In the formula, is the front wheel tire slip angle; is the vehicle's center of mass sideslip angle; is the vehicle yaw angular velocity; is the distance from the front axle of the chassis to the center of mass of the vehicle; is the vehicle longitudinal velocity; is the front wheel turning angle; is the rear wheel tire slip angle; is the distance from the rear axle of the vehicle to the center of mass of the vehicle; Combining formula (1) we can get: ; (2) The above formula can be further written as: ; (3) In the formula, is the distance between the front and rear axles, ; is the distance from the vehicle's turning center to its center of mass, which is the vehicle's turning radius; The formula for the lateral and yaw motion of the vehicle in a steady state is established as follows: ; (4) In the formula, is the vehicle mass; is the lateral acceleration of the vehicle; is the lateral force on the front axle; is the lateral force on the rear axle; is the moment of inertia of the vehicle around the vertical axis; is the yaw angular acceleration; Calculate the lateral forces on the front and rear axles as follows: ; (5) In the formula, is the lateral stiffness of the front wheel; is the lateral stiffness of the rear wheel; Since in steady state, , , so the above formula can be written as follows: ; (6) Substituting formula (6) and formula (5) into formula (3), we get: ; (7) The above formula is written as: ; (8) In the formula, is the stability factor of the car, namely: ; (9) 13) Introducing understeer factor , as shown below: ; (10) Therefore, transform equation (8) into: ; (11) 14) Set the front wheel angle to the Ackermann steering angle and dynamic steering angle as follows: ; (12) ; (13) ; (14) In the formula, is the Ackermann steering angle; For dynamic corners; is the actual front wheel steering angle; 15) Convert equation (11) into: ; (15) 16) Set the reference yaw rate to: ; (16) In the formula, is the reference yaw rate; 17) Set the ideal yaw rate to be constrained as: ; (17) In the formula, is the road adhesion coefficient; is the acceleration of gravity; 0.85 is the safety factor set; 18) Calculate the actual reference yaw rate as follows: ; (18) In the formula, is the Laplace operator; is the appropriate first-order inertia link time constant 19) Introduce the fitting function and add the nonlinear steering characteristic fitting curve to calculate the lateral acceleration, as shown below: ; In the formula, is the lateral acceleration limit value in the linear region; is the maximum achievable lateral acceleration; The dynamic front wheel steering angle is calculated as follows: ; The ideal yaw rate of the design is obtained as follows: .

[0007] Furthermore, obtaining the sensor, vehicle status, and road surface information includes obtaining the lateral and longitudinal vehicle speeds, lateral and longitudinal accelerations, road adhesion coefficients, and longitudinal tire lateral forces.

[0008] Furthermore, the specific method for designing a chassis domain yaw stability integrated control system based on a three-step method for a four-wheel steering distributed drive electric vehicle is as follows: 41) The vehicle dynamics equations for the lateral and yaw motions of the vehicle are established as follows: ; (19) ; (20) In the formula, is the sideslip angular velocity of the center of mass; is the yaw angular acceleration; Additional yaw moment for differential drive; and The lateral reaction force of the ground on the front and rear axles of the vehicle’s front and rear wheels; is the vehicle mass; is the yaw moment of inertia of the vehicle; 42) Define the relationship between the front and rear wheel angles; define the ratio of the rear wheel angle to the front wheel angle for: ;(twenty one) In the formula, is the front wheel turning angle; is the rear wheel turning angle; 43) Establish the relationship between the ratio of the front axle lateral force and the rear axle lateral force to the rear wheel turning angle and the front wheel turning angle, as follows: ;(twenty two) In the formula, is the proportional coefficient of the lateral force of the front and rear axles; 44) Set the control quantity of the three-step method to , and ; 45) Based on the current measured values ​​of the vehicle, the steady-state value is calculated as follows: In formulas (19) and (20), , , obtain the steady-state control input, and use , and Indicates, as follows: ; ; ; Solve for the desired steady-state control input as follows: ; ; ; In the formula, for The steady-state control input quantity; for The steady-state control input quantity; The steady-state control input quantity; 46) Introduce the feedforward control of reference dynamics, consider the transient response of the sideslip angle and yaw rate, and set the control input conditions as follows: ; ; ; In the formula, , , is the feedforward control quantity; Substituting into formulas (19), (20) and (22), , and is the feedforward control quantity; ; ; ; make , The feedforward control input is solved as: ; ; ; 47) Introduce tracking error feedback control and set the control input as follows: ; ; ; Substituting into formulas (19), (20) and (22), , and is the feedback control quantity: ; ; ; The steady-state control and feedforward control inputs are used , , and , and The expression of is: ;(twenty three) ;(twenty four) ; (25) Define tracking error as follows: ; ; (26) In the formula, is the vehicle center of mass sideslip angle error; is the vehicle yaw rate error; is the reference center of mass sideslip angle; is the reference yaw rate; Then equation (23) and equation (24) become: ; (27) ; (28) Select a certain control error term, namely the center of mass sideslip angle and yaw rate error in equation (26), so that equations (27) and (28) become The case where the exponential is asymptotically stable; Formula (27) and formula (28) are combined with formula (25) to form the following form: ; (29) ; (30) In the formula, is the proportional gain; is the integral gain; That is to obtain , and Values: ; ; ; 48) Set the control law of the three-step controller as follows: ; (31) In the formula, is the control input; is the steady-state control term; is the feedforward control term; is the error feedback control term; and: ; ; ; 49) Based on the three-step control law, the yaw moment is converted into tire angle and additional torque output by solving the lateral force of the front and rear wheels, as follows: Before solving, analyze the resultant lateral forces on the front and rear axles; The motion equations of the vehicle in three degrees of freedom are established as follows: ; (32) In the formula, is the total longitudinal force of the vehicle; is the total lateral force of the vehicle; and , i=1, 2, 3, 4, respectively, are the longitudinal force and lateral force of the two front wheels and two rear wheels of the vehicle; is the front and rear wheel track; is the rear wheel turning angle; The relationship between the four-wheel side slip angle and the four-wheel turning angle is established as follows: ; ; ; ; In the formula, , , , They are the tire slip angles of the four wheels respectively; Therefore, the lateral force of the four-wheel tires is expressed as follows: ; ; ; ; The lateral force of the front and rear axles is expressed as follows: ; ; Therefore, by inversely solving the above formula, we can get the decision value of the front and rear wheel angles: ; ; In the formula, is the calculated front wheel steering angle value; To calculate the rear wheel steering angle, the driver's steering wheel angle Transmission ratio to steering system Get the nominal value of the front wheel angle , and the nominal value of the rear wheel angle is constant at 0, so the final additional value of the front and rear wheel angles is obtained to complete the final control output, as shown below: ; .

[0009] In a second aspect, the present invention further provides a unified yaw motion control device for a vehicle chassis domain based on a three-step method, which is used to implement a unified yaw motion control method for a vehicle chassis domain based on a three-step method, comprising: A unified yaw motion controller 110 for calculating a yaw target; The environment analysis module 120 is used to uniformly obtain sensor, vehicle status, and road surface information to achieve internal information resource sharing; A failure redundancy control module 130 is used to identify failures of software and hardware to ensure the safety of corresponding driving; The sub-function control module 140 is used to design a chassis domain yaw stability integrated control system based on a three-step method for a four-wheel steering distributed drive electric vehicle, obtain yaw moment and front and rear wheel angle additional values, and send the front and rear wheel angle additional values ​​to the vehicle; An output arbitration module 150 is used to distribute the additional yaw moment and distribute it to four wheels for execution; The actuator 160 is used to execute the allocated yaw moment control command and the front and rear wheel angle additional value command to achieve the expected vehicle yaw dynamic control.

[0010] The beneficial effects of the present invention are: 1) The present invention is conducive to the complementary advantages of each independent system, and makes joint decisions based on the functions of the integrated subsystems to avoid coordination problems. At the same time, it retains independent control algorithms, which not only avoids failure problems but also retains the ability of the subsystems to work independently, improves the stability margin and handling stability of the vehicle, simplifies the automotive electronic and electrical architecture, and proposes a feasible solution to the redundant wiring harnesses in the vehicle and the complex and independent controllers; 2) The present invention aims at a unified ideal yaw target for yaw motion, replaces the original simple linear steering characteristic, reintroduces the fitting function, and adds a nonlinear steering characteristic fitting curve. The ideal target change trend is closer to the basic steering characteristic curve of the vehicle. Therefore, the chassis domain yaw control algorithm can better approach the ideal target and thus better improve the dynamic performance and handling stability of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0012] Figure 1 It is a schematic diagram of a unified yaw motion control device for a vehicle chassis domain based on a three-step method according to the present invention; Figure 2 A schematic diagram of a unified yaw motion control method for a vehicle chassis domain based on a three-step method according to the present invention; Figure 3 It is a schematic diagram comparing the sideslip angle of the center of mass under three kinds of control; Figure 4 It is a schematic diagram of the comparison of actual yaw angular velocity under three kinds of control; Figure 5 It is a schematic diagram of the front wheel turning angle and the added value of the front and rear wheel turning angles; Figure 6 Schematic diagram comparing the steering wheel angles under three types of control. DETAILED DESCRIPTION

[0013] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0014] Embodiment 1: See also Figure 1This embodiment provides a unified yaw motion control method for a vehicle chassis domain based on a three-step method, and the specific method is as follows: A. Calculate the yaw target as follows: 11) Since the driver expects the vehicle to be stable and the center of mass slip angle to be as small as possible, the ideal center of mass slip angle is designed. ; 12) Design the ideal yaw rate; Calculate the front and rear tire slip angles of a distributed drive four-wheel steering vehicle as follows: ; (1) In the formula, is the front wheel tire slip angle; is the vehicle's center of mass sideslip angle; is the vehicle yaw angular velocity; is the distance from the front axle of the chassis to the center of mass of the vehicle; is the vehicle longitudinal velocity; is the front wheel turning angle; is the rear wheel tire slip angle; is the distance from the rear axle of the vehicle to the center of mass of the vehicle; Combining formula (1) we can get: ; (2) The above formula can be further written as: ; (3) In the formula, is the distance between the front and rear axles, ; is the distance from the vehicle's turning center to its center of mass, which is the vehicle's turning radius; The vehicle is in a steady state, and the lateral and yaw motions of the vehicle are determined by the following formulas, as shown below: ; (4) In the formula, is the vehicle mass; is the lateral acceleration of the vehicle; is the lateral force on the front axle; is the lateral force on the rear axle; is the moment of inertia of the vehicle around the vertical axis; is the yaw angular acceleration; Calculate the lateral forces on the front and rear axles as follows: ; (5) In the formula, is the lateral stiffness of the front wheel; is the lateral stiffness of the rear wheel; Since in steady state, , , so the above formula can be written as follows: ; (6) Substituting formula (6) and formula (5) into formula (3), we get: ; (7) The above formula is written as: ; (8) In the formula, is the stability factor of the car, namely: ; (9) 13) In order to Distinguish, introduce understeer factor as , only the stability factor Multiply one more , as shown below: ; (10) In the formula, is the understeer factor; Therefore, transform equation (8) into: ; (11) 14) It can be clearly seen from formula (11) that the front wheel steering angle consists of two parts. The front part is the Ackerman steering angle, and the rear part can be understood as the dynamic steering angle, that is: ; (12) ; (13) ; (14) In the formula, is the Ackermann steering angle; For dynamic corners; is the actual front wheel steering angle; 15) Convert equation (11) into: ; (15) 16) Set the reference yaw rate to: ; (16) In the formula, is the reference yaw rate; 17) In the above formula, the tire limit stress condition is not considered. Due to the influence of the road adhesion coefficient, the ideal yaw rate of the vehicle is subject to the following constraints: ; (17) In the formula, is the road adhesion coefficient; is the acceleration of gravity; 0.85 is the safety factor set; 18) In practical applications, a first-order inertia link is used to provide smoothing, and the actual reference yaw rate is: ; (18) In the formula, is the Laplace operator; is the appropriate first-order inertia link time constant.

[0015] Among them, equation (16) describes the linear relationship between the dynamic steering angle and the lateral acceleration. When the lateral acceleration is small, the fitting is more accurate and can represent the approximate value of the real vehicle. When the lateral acceleration is large, the deviation from the actual characteristics of the vehicle is large. Therefore, through the curve fitting design of the lateral acceleration, when the lateral acceleration changes, the steering characteristics of the vehicle tend to be able to exert the maximum performance of the vehicle and change continuously.

[0016] 19) Therefore, the steering characteristics are designed, the fitting function is reintroduced, and the nonlinear steering characteristic fitting curve is added. The lateral acceleration is: ; In the formula, is the lateral acceleration limit value in the linear region, is the maximum achievable lateral acceleration; Calculate the dynamic front wheel steering angle as: ; Furthermore, the ideal yaw rate of the design can be obtained as follows: ; B. Obtain sensor, vehicle status, and road information to achieve internal information resource sharing; The information includes the vehicle's lateral and longitudinal speeds, lateral and longitudinal accelerations, road adhesion coefficient and tire longitudinal lateral force.

[0017] C. Vehicle control when software and hardware fail, i.e. fault state control, including torque vector control (TVC) / integrated brake control (IBC) to achieve steering, and IBC fault redundant brake unit (RBU) to start the failure redundant control algorithm to ensure the corresponding driving safety; D. For four-wheel steering distributed drive electric vehicles, a chassis domain yaw stability integrated control system based on a three-step method is designed, as follows: 41) The vehicle dynamics equations for the lateral and yaw motions of the vehicle are established as follows: ; (19) ; (20) In the formula, is the sideslip angular velocity of the center of mass; is the yaw angular acceleration; Additional yaw moment for differential drive; and The lateral reaction force of the ground on the front and rear axles of the vehicle’s front and rear wheels; is the vehicle mass; is the yaw moment of inertia of the vehicle; 42) The definition of the front and rear wheel angle relationship determines the steering characteristics of the vehicle. The proportionality coefficient is used to describe the dependence between the rear wheel angle and the front wheel angle. Therefore, the front and rear wheel angle relationship is defined; the ratio of the rear wheel angle to the front wheel angle is defined. for: ;(twenty one) In the formula, is the front wheel turning angle; is the rear wheel turning angle; 43) Lateral force is the force generated by the interaction between the tire and the ground, and its magnitude and direction determine the driving stability of the vehicle. Define the formula for the front and rear axle lateral force ratio, which reflects the distribution of the front and rear axle lateral forces and is crucial for stability control; therefore, establish the ratio relationship between the front axle lateral force and the rear axle lateral force and the rear wheel turning angle and the front wheel turning angle, as follows: ;(twenty two) In the formula, is the proportional coefficient of the lateral force of the front and rear axles; 44) Set the control quantity of the three-step method to , and ; The three-step control method is used in vehicle stability control systems and is decomposed into three control variables: rear axle lateral force (Adjust the lateral force of the rear wheels to affect the vehicle's center of mass sideslip angle), additional yaw moment (Generate additional yaw torque through differential drive or other means to directly adjust the yaw rate), front axle lateral force : Adjusts the lateral force of the front wheels to help stabilize the vehicle's yaw motion. The control variables work together to ensure vehicle stability and handling under different driving conditions.

[0018] 45) The first step of the three-step method: The calculation of the steady-state value is based on the dynamic equation of the vehicle during stable driving. Assume that the vehicle reaches a steady state ( , ), the desired steady-state control inputs can be solved. These steady-state control inputs are used to calculate the target lateral force and yaw moment of the vehicle. Therefore, based on the current measured values ​​of the vehicle, the steady-state values ​​are calculated to ensure that the vehicle operates within the linear range of yaw rate and sideslip angle to avoid excessive tire slip: In formulas (19) and (20), , , obtain the steady-state control input, and use , and Indicates, as follows: ; ; ; make , The feedforward control input is solved as: ; ; ; In the formula, for The steady-state control input quantity; for The steady-state control input quantity; The steady-state control input quantity; 46) The second step of the three-step method: In order to improve the transient response of the vehicle, it is necessary to introduce a feedforward control of the reference dynamics. When the dynamic model undergoes dynamic changes, the system can respond to it in a timely manner, improving the rapidity and transient characteristics of the system response; considering the transient response of the center of mass sideslip angle and yaw angular velocity, the control input satisfies: ; ; ; In the formula, 、 、 is the feedforward control quantity; Substituting into formulas (19), (20) and (22), , and is the feedforward control quantity; ; ; ; make , The feedforward control input is solved as: ; ; ; 44) The third step of the three-step method: In order to further improve the control accuracy, it is necessary to add tracking error feedback control; define the error as equation (26), and design the proportional integral (PI) feedback control law to make the error exponentially decay steadily. This error feedback control can effectively compensate for the possible deviation between steady-state control and feedforward control, so that the system can reach the desired trajectory, as follows: Let the control input satisfy: ; ; ; In the formula, is the additional yaw moment; Substituting into formulas (19), (20) and (22), , and is the feedback control quantity: ; ; ; The steady-state control and feedforward control inputs are used , , and , and The expression of is: ;(twenty three) ;(twenty four) ; (25) Define tracking error, ; ; (26) In the formula, is the vehicle center of mass sideslip angle error; is the vehicle yaw rate error; is the reference center of mass sideslip angle; is the reference yaw rate; Then equation (23) and equation (24) become: ; (27) ; (28) In order to ensure the asymptotic stability of the error exponential, a suitable error feedback control law is usually selected, such as proportional control (P control) or PI control (proportional-integral control), so that Equations (27) and (28) become exponentially asymptotically stable.

[0019] Formula (27) and formula (28) are combined with formula (25) to form the following form: ; (29) ; (30) In the formula, is the proportional gain; is the integral gain; That is to obtain , and Values: ; ; ; 48) Set the control law of the three-step controller. The overall control law of the three-step controller consists of three parts: : Steady-state control term, which calculates the control input based on steady-state conditions; : Feedforward control term, used to improve transient response. : Error feedback control item, used to compensate for system error; The controller control law is as follows: ; (31) In the formula, is the control input; is the steady-state control term; is the feedforward control term; is the error feedback control term; and: ; ; ; 49) Based on the three-step control law, the yaw moment is converted into tire angle and additional torque output by solving the lateral force of the front and rear wheels, as follows: Before solving, analyze the resultant lateral forces on the front and rear axles; The force on the vehicle is given by the equation of motion. The equation of motion of the vehicle in three degrees of freedom is as follows: ; (32) In the formula, is the total longitudinal force of the vehicle; is the total lateral force of the vehicle; and , i=1, 2, 3, 4, respectively, are the longitudinal force and lateral force of the two front wheels and two rear wheels of the vehicle; is the front and rear wheel track; is the rear wheel turning angle; The subsequent calculation of tire lateral force depends on the sideslip angle, so the formula for calculating the sideslip angle is given as follows: ; ; ; ; In the formula, , , , They are the tire slip angles of the four wheels respectively; The reasonable derivation and calculation of the lateral force of the front and rear axles depends on the lateral force of the four-wheel tires. The expression of the lateral force of the four-wheel tires is as follows: ; ; ; ; One of the control quantities in the control law is the resultant lateral force of the front and rear axles, which is: ; ; Therefore, by inversely solving the above formula, the front and rear wheel angle decision values ​​are obtained for the control needs of the four-wheel steering system, as shown below: ; ; In the formula, is the calculated front wheel steering angle value; To calculate the rear wheel steering angle, the driver's steering wheel angle Transmission ratio to steering system Get the nominal value of the front wheel angle , and the nominal value of the rear wheel steering angle is constant at 0, so the final front and rear wheel steering angle additional value is obtained to complete the final control output; ; .

[0020] At this point, the control law and control output of the three-step method are completed, and the obtained front and rear wheel angle added values ​​are sent to the vehicle; Among them, the additional yaw moment and the additional values ​​of the front and rear wheel angles are the two core control outputs of the three-step controller. They interact with each other and jointly affect the stability of the vehicle.

[0021] The additional yaw torque directly adjusts the driving torque of the four wheels to achieve yaw stability control, mainly through the torque vectoring control (TVC) mechanism to optimize the driving force distribution of the tires, so that the vehicle can maintain stability under high speed and complex working conditions.

[0022] The added value of the front and rear wheel angles directly affects the steering actuator, determines the change in the front and rear wheel angles of the vehicle, and mainly optimizes the steering characteristics of the vehicle through the four-wheel steering (4WS) mechanism to reduce the risk of skidding. E. Additional yaw moment is distributed and distributed to the four wheels for execution; The present invention does not limit the specific structure of the yaw moment distribution controller, as long as it can complete the function. In a preferred method of real-time deployment on a real vehicle, an average distribution method is used to distribute the yaw moment; F. Execute the allocated yaw moment control command and the front and rear wheel steering angle commands to achieve the expected vehicle yaw dynamic control.

[0023] Embodiment 2: This embodiment provides a double lane change condition at 80 km / h on a low adhesion road: the vehicle speed is set to 80 km / h, the road adhesion coefficient is set to 0.3, and simulation verification is performed under the double lane change condition. The control effect of the three-step controller is compared with that of the torque vector control (TVC) function with no control and only PID control.

[0024] like Figure 3 and Figure 4 As shown in the figure, the uncontrolled vehicle can complete the double lane change test, but the sideslip angle and yaw rate are large; only turning on the TVC algorithm will suppress the yaw rate and the sideslip angle, and get closer to the ideal target; and after the unified yaw motion control algorithm is turned on, the suppression effect on the sideslip angle and yaw rate is more obvious, the stability of the vehicle under low adhesion and high speed conditions is also better, and there is almost no control lag, which is conducive to maintaining real-time control.

[0025] like Figure 5 As shown, from the added values ​​of the front wheel angle and the rear wheel angle, it can be seen that the three-step controller makes decisions on the front wheel angle and the rear wheel angle at the same time, and the directions of the front and rear wheel angle added values ​​are opposite, but the directions of the front and rear wheel angles remain consistent, which meets the recognition of four-wheel steering and is beneficial to help the car maintain high-speed driving stability.

[0026] like Figure 6The figure shows the comparison of the steering wheel angles under the three control modes. For the same working condition, the smaller the steering wheel angle, the lower the driver's operating load. Under the three-step controller, after completing the double lane change condition, the steering wheel angle applied by the driver is the smallest, with the lowest operating load.

[0027] Embodiment three: See also Figure 2 This embodiment provides a unified yaw motion control device for a vehicle chassis domain based on a three-step method, which is used to implement a unified yaw motion control method for a vehicle chassis domain based on a three-step method described in Embodiment 1, including: A unified yaw motion controller 110 for calculating a yaw target; The environment analysis module 120 is used to obtain sensor, vehicle status, and road surface information to achieve internal information resource sharing; A failure redundancy control module 130 is used to identify failures of software and hardware to ensure the safety of corresponding driving; The sub-function control module 140 is used to design a chassis domain yaw stability integrated control system based on a three-step method for a four-wheel steering distributed drive electric vehicle, obtain yaw moment and front and rear wheel angle additional values, and send the front and rear wheel angle additional values ​​to the vehicle; An output arbitration module 150 is used to distribute the additional yaw moment and distribute it to four wheels for execution; The actuator 160 is used to execute the allocated yaw moment control command and the front and rear wheel angle additional value command to achieve the expected vehicle yaw dynamic control.

[0028] Embodiment 4: This embodiment provides a terminal, including: one or more processors; a memory for storing said one or more processor executable instructions; Wherein, the one or more processors are configured to: A unified yaw motion control method for a vehicle chassis domain based on a three-step method as described in Example 1 is implemented.

[0029] Embodiment five: This embodiment provides a non-temporary computer-readable storage medium. When the instructions in the storage medium are executed by the processor of the terminal, the terminal can execute a unified yaw motion control method in the chassis domain of an automobile based on the three-step method as described in Example 1.

[0030] In summary, the present invention can improve the dynamic performance and handling stability of the vehicle and solve the problem of insufficient yaw control in the traditional wire-controlled chassis system.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A unified yaw motion control method for vehicle chassis domain based on a three-step method, characterized in that: The following steps are involved: Calculate yaw target; Obtain sensor, vehicle status, and road information to achieve internal information resource sharing; Identify software and hardware failures to ensure driving safety; For four-wheel steering distributed drive electric vehicles, a chassis domain yaw stability integrated control system based on a three-step method is designed to obtain additional yaw moment and additional values ​​of front and rear wheel steering angles, and send the additional values ​​of front and rear wheel steering angles to the vehicle; Distribute the yaw moment and distribute it to the four wheels for execution; The allocated yaw moment control command is executed, as well as the front and rear wheel angle additional value commands to achieve the expected vehicle yaw dynamic control.

2. The unified yaw motion control method for chassis domain of an automobile based on the three-step method according to claim 1 is characterized in that: The specific method for calculating the yaw target is as follows: 11) Design the ideal center of mass sideslip angle ; 12) Design the ideal yaw rate as follows: Calculate the front and rear tire slip angles of a distributed drive four-wheel steering vehicle as follows: ；（1） In the formula, is the front wheel tire slip angle; is the vehicle's center of mass sideslip angle; is the vehicle yaw angular velocity; is the distance from the front axle of the chassis to the center of mass of the vehicle; is the vehicle longitudinal speed; is the front wheel turning angle; is the rear wheel tire slip angle; is the distance from the rear axle of the vehicle to the center of mass of the vehicle; Combining formula (1) we can get: ；（2） The above formula can be further written as: ；（3） In the formula, is the distance between the front and rear axles, ; is the distance from the vehicle's turning center to its center of mass, which is the vehicle's turning radius; The formula for the lateral and yaw motion of the vehicle in a steady state is established as follows: ；（4） In the formula, is the vehicle mass; is the vehicle lateral acceleration; is the lateral force on the front axle; is the lateral force on the rear axle; is the moment of inertia of the vehicle around the vertical axis; is the yaw angular acceleration; Calculate the lateral forces on the front and rear axles as follows: ；（5） In the formula, is the lateral stiffness of the front wheel; is the lateral stiffness of the rear wheel; Since in steady state, , , so the above formula can be written as follows: ；（6） Substituting formula (6) and formula (5) into formula (3), we get: ；（7） The above formula is written as: ；（8） In the formula, is the stability factor of the car, namely: ； （9） 13) Introducing understeer factor , as shown below: ；（10） Therefore, transform equation (8) into: ；（11） 14) Set the front wheel angle to the Ackermann steering angle and dynamic steering angle as follows: ；（12） ；（13） ； （14） In the formula, is the Ackermann steering angle; For dynamic corners; is the actual front wheel steering angle; 15) Convert equation (11) into: ；（15） 16) Set the reference yaw rate to: ；（16） In the formula, is the reference yaw rate; 17) Set the ideal yaw rate to be constrained as: ；（17） In the formula, is the road adhesion coefficient; is the acceleration of gravity; 0.85 is the safety factor set; 18) Calculate the actual reference yaw rate as follows: ； （18） In the formula, is the Laplace operator; is the appropriate first-order inertia link time constant; 19) Introduce the fitting function and add the nonlinear steering characteristic fitting curve to calculate the lateral acceleration, as shown below: ； In the formula, is the lateral acceleration limit value in the linear region; is the maximum achievable lateral acceleration; The dynamic front wheel steering angle is calculated as follows: ； The ideal yaw rate of the design is obtained as follows: 。 3. The unified yaw motion control method for chassis domain of an automobile based on a three-step method according to claim 1, characterized in that: The acquisition of sensor, vehicle status, and road surface information includes acquiring transverse and longitudinal vehicle speeds, transverse and longitudinal accelerations, road surface adhesion coefficients, and longitudinal tire lateral forces.

4. The unified yaw motion control method for chassis domain of an automobile based on a three-step method according to claim 1, characterized in that: The above-mentioned design of a chassis domain yaw stability integrated control system based on a three-step method for a four-wheel steering distributed drive electric vehicle is as follows: 41) The vehicle dynamics equations for the lateral and yaw motions of the vehicle are established as follows: ；（19） ； （20） In the formula, is the sideslip angular velocity of the center of mass; is the yaw angular acceleration; Additional yaw moment for differential drive; and The lateral reaction force of the ground on the front and rear axles of the vehicle’s front and rear wheels; is the vehicle mass; is the yaw moment of inertia of the vehicle; 42) Define the relationship between the front and rear wheel angles; define the ratio of the rear wheel angle to the front wheel angle for: ； （21） In the formula, is the front wheel turning angle; is the rear wheel turning angle; 43) Establish the relationship between the ratio of the front axle lateral force and the rear axle lateral force to the rear wheel turning angle and the front wheel turning angle, as follows: ；（22） In the formula, is the proportional coefficient of the lateral force of the front and rear axles; 44) Set the control quantity of the three-step method to , and ; 45) Based on the current measured values ​​of the vehicle, the steady-state value is calculated as follows: In formulas (19) and (20), , , obtain the steady-state control input, and use , and Indicates, as follows: ； ； ； Solve for the desired steady-state control input as follows: ； ； ； In the formula, for The steady-state control input quantity; for The steady-state control input quantity; The steady-state control input quantity; 46) Introduce the feedforward control of reference dynamics, consider the transient response of the sideslip angle and yaw rate, and set the control input conditions as follows: ； ； ； In the formula, 、 、 is the feedforward control quantity; Substituting into formulas (19), (20) and (22), , and is the feedforward control quantity; ； ； ； make , The feedforward control input is solved as: ； ； ； 47) Introduce tracking error feedback control and set the control input as follows: ； ； ； Substituting into formulas (19), (20) and (22), , and is the feedback control quantity: ； ； ； The steady-state control and feedforward control inputs are used , , and , and The expression of is: ；（23） ；（24） ；（25） Define tracking error as follows: ； ； （26） In the formula, is the vehicle center of mass sideslip angle error; is the vehicle yaw rate error; is the reference center of mass sideslip angle; is the reference yaw rate; Then equation (23) and equation (24) become: ；（27） ；（28） Select a certain control error term, namely the center of mass sideslip angle and yaw rate error in equation (26), so that equations (27) and (28) become The case where the exponential is asymptotically stable; Formula (27) and formula (28) are combined with formula (25) to form the following form: ；（29） ；（30） In the formula, is the proportional gain; is the integral gain; That is to obtain , and Values: ； ； ； 48) Set the control law of the three-step controller as follows: ；（31） In the formula, is the control input; is the steady-state control term; is the feedforward control term; is the error feedback control term; and: ； ； ； 49) Based on the three-step control law, the yaw moment is converted into tire angle and additional torque output by solving the lateral force of the front and rear wheels, as follows: Before solving, analyze the resultant lateral forces on the front and rear axles; The equations of motion of the vehicle in three degrees of freedom are as follows: ； （32） In the formula, is the total longitudinal force of the vehicle; is the total lateral force of the vehicle; and , i=1, 2, 3, 4, respectively, are the longitudinal force and lateral force of the two front wheels and two rear wheels of the vehicle; is the front and rear wheel track; is the rear wheel turning angle; The relationship between the four-wheel side slip angle and the four-wheel turning angle is given as follows: ； ； ； ； In the formula, , , , They are the tire slip angles of the four wheels respectively; Therefore, the lateral force of the four-wheel tires is expressed as follows: ； ； ； ； The lateral force of the front and rear axles is expressed as follows: ； ； Therefore, by inversely solving the above formula, we can get the decision value of the front and rear wheel angles: ； ； In the formula, is the calculated front wheel steering angle value; To calculate the rear wheel steering angle, the driver's steering wheel angle Transmission ratio to steering system Get the nominal value of the front wheel angle , and the nominal value of the rear wheel angle is constant at 0, so the final additional value of the front and rear wheel angles is obtained to complete the final control output, as shown below: ； 。 5. A unified yaw motion control device for automobile chassis domain based on a three-step method, used to implement a unified yaw motion control method for automobile chassis domain based on a three-step method as described in any one of claims 1 to 4, characterized in that: include: A unified yaw motion controller (110) for calculating a desired yaw target; An environment analysis module (120) is used to uniformly obtain sensor, vehicle status, and road surface information to achieve internal information resource sharing; A failure redundancy control module (130) is used to identify software and hardware failures and ensure the safety of corresponding driving; A sub-function control module (140) is used to design a chassis domain yaw stability integrated control system based on a three-step method for a four-wheel steering distributed drive electric vehicle; An output arbitration module (150) is used to distribute the additional yaw moment and distribute it to four wheels for execution; The actuator (160) is used to execute the allocated yaw moment control command and the front and rear wheel angle additional value command to achieve the expected vehicle yaw dynamic control.

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