A control method and device for rear-wheel active steering

Abstract

An embodiment of the present disclosure provides a control method, device, storage medium, and electronic device for rear-wheel active steering. The control method includes determining a vehicle steady-state parameter based on an actual value of a front-wheel angle of the vehicle and an actual value of a vehicle speed of the vehicle. The vehicle steady-state parameter includes at least a given value of yaw rate and a given value of sideslip angle of the center of mass. Inputting the vehicle steady-state parameter, the actual value of the front-wheel angle, and the vehicle speed actual value into a specified model to determine a vehicle steering stability parameter. The vehicle steering stability parameter includes at least a target value of the rear-wheel angle, a target value of the compensating yaw moment, and a vehicle side force. Controlling the rear-wheel steering of the vehicle based on the vehicle steering stability parameter. In the process of controlling the rear wheels of the vehicle, the embodiment of the present disclosure adopts a model predictive control method, which not only controls the rear-wheel angle but also increases the control of the yaw moment and controls the braking pressure to ensure the stability of vehicle handling in the case of rear-wheel steering.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wheel control, and particularly to a control method, device, storage medium, and electronic device for active rear-wheel steering. Background Art

[0002] With the development of vehicle chassis electronic control systems and autonomous driving technologies, more and more vehicles are equipped with an active rear-wheel steering device (hereinafter referred to as ARS), which is integrated with the front-wheel steering system. It can reduce the turning radius of the vehicle during low-speed steering, improving the maneuverability of low-speed steering. During high-speed steering, it can keep the sideslip angle of the vehicle's center of mass basically zero, enhancing the dynamic response characteristics and handling stability of the vehicle to the steering wheel angle input.

[0003] Currently, the control method adopted for active rear-wheel steering is sliding mode control. However, when reaching the sliding surface, chattering will occur, which will affect the control accuracy, and the vehicle stability margin under extreme conditions is small, making it difficult to ensure vehicle stability. Summary of the Invention

[0004] The purpose of the embodiments of the present disclosure is to provide a control method, device, storage medium, and electronic device for active rear-wheel steering to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the embodiments of the present disclosure adopt the following technical solutions:

[0006] A control method for active rear-wheel steering, which includes: based on the actual value of the front-wheel angle of the vehicle and the actual value of the vehicle speed of the vehicle, determining the vehicle's vehicle stability parameters, where the vehicle stability parameters at least include a yaw rate set value and a sideslip angle set value of the center of mass; inputting the vehicle stability parameters, the actual value of the front-wheel angle, and the actual value of the vehicle speed into a specified model to determine the vehicle's steering stability parameters, where the steering stability parameters at least include a target value of the rear-wheel angle, a target value of the compensating yaw moment, and a vehicle lateral force; controlling the rear-wheel steering of the vehicle based on the steering stability parameters.

[0007] In some embodiments, the determining the vehicle's vehicle stability parameters based on the actual value of the front-wheel angle of the vehicle and the actual value of the vehicle speed includes: comparing the actual value of the vehicle speed with a vehicle speed threshold; determining the vehicle's vehicle stability parameters respectively based on the judgment result.

[0008] In some embodiments, determining the steering stability parameters of the vehicle based on the vehicle steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed includes: when the actual vehicle speed is less than the first vehicle speed threshold, inputting the actual front wheel steering angle and the actual vehicle speed into a function model to determine the target rear wheel steering angle; when the actual vehicle speed is greater than or equal to the first vehicle speed threshold, inputting the vehicle steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed into a prediction model to determine the target rear wheel steering angle, the target compensating yaw moment, and the vehicle side force.

[0009] In some embodiments, inputting the vehicle steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed into a prediction model to determine the target rear wheel steering angle, the target compensating yaw moment, and the vehicle side force includes: establishing a two-degree-of-freedom vehicle model and a non-linear simplified tire model; establishing a prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model; establishing an objective function based on the prediction model; and determining control variables based on the objective function and control variable constraints, where the control variables are the target rear wheel steering angle and the target compensating yaw moment.

[0010] In some embodiments, it further includes: obtaining the actual operating parameters of the vehicle;

[0011] Based on the vehicle side force, the actual front wheel steering angle, and the actual operating parameters, determining the actual value of the center of mass side slip angle; and adjusting the steering stability parameters based on the actual value of the center of mass side slip angle.

[0012] In some embodiments, the actual front wheel steering angle is obtained by the following method: obtaining the actual steering wheel angle; and determining the actual front wheel steering angle based on the actual steering wheel angle and the steering system transmission ratio.

[0013] In some embodiments, controlling the rear wheel steering of the vehicle based on the steering stability parameters includes: determining the braking pressure based on the target rear wheel steering angle and the target compensating yaw moment; and controlling the rear wheel steering of the vehicle based on the actual rear wheel steering angle, the target compensating yaw moment, and the braking pressure.

[0014] The embodiments of the present disclosure further provide a control device for rear-wheel active steering, which includes:

[0015] A vehicle steady-state parameter determination module, configured to determine the vehicle steady-state parameters of the vehicle based on the actual front wheel steering angle of the vehicle and the actual vehicle speed of the vehicle, where the vehicle steady-state parameters at least include a given yaw rate value and a given center of mass side slip angle value;

[0016] The steering stability parameter determination module is configured to input the vehicle's steady-state parameters, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a specified model to determine the vehicle's steering stability parameters, where the steering stability parameters at least include the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle side force.

[0017] The steering control module is configured to control the rear-wheel steering of the vehicle based on the steering stability parameters.

[0018] The present disclosure also provides a storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the method described in any one of the above are implemented.

[0019] The present disclosure also provides an electronic device including at least a memory and a processor. A computer program is stored on the memory, and when the processor executes the computer program on the memory, the steps of the method described in any one of the above are implemented.

[0020] In the process of controlling the rear wheels of the vehicle in the embodiments of the present disclosure, a model predictive control method is adopted. While controlling the rear wheel steering angle, the control of the yaw moment is also increased, and the control of the braking pressure is carried out. Further, through the hard constraints on multiple control variables, the stability of vehicle handling during rear-wheel steering is ensured. In addition, the embodiments of the present disclosure also implement different control methods and set the limit ranges of control variables for different working conditions and driving modes, taking into account the vehicle stability performance under different working conditions. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Schematic diagram of the steps of the control method for rear-wheel active steering in the embodiments of the present disclosure;

[0023] Figure 2 Schematic diagram of the steps of the control method for rear-wheel active steering in the embodiments of the present disclosure;

[0024] Figure 3 Schematic diagram of the steps of the control method for rear-wheel active steering in the embodiments of the present disclosure;

[0025] Figure 4 Schematic diagram of the steps of the control method for rear-wheel active steering in the embodiments of the present disclosure;

[0026] Figure 5Schematic diagram of the steps of the control method for rear-wheel active steering according to an embodiment of the present disclosure;

[0027] Figure 6 Schematic diagram of the steps of the control method for rear-wheel active steering according to an embodiment of the present disclosure;

[0028] Figure 7 Schematic diagram of the steps of the control method for rear-wheel active steering according to an embodiment of the present disclosure. Detailed implementation manners

[0029] Reference is made herein to the various solutions and features of the present disclosure with reference to the accompanying drawings.

[0030] It should be understood that various modifications can be made to the embodiments applied herein. Therefore, the above specification should not be regarded as a limitation, but only as an example of the embodiments. Those skilled in the art will think of other modifications within the scope and spirit of the present disclosure.

[0031] The accompanying drawings included in and forming a part of the specification illustrate embodiments of the present disclosure and, together with the general description of the present disclosure given above and the detailed description of the embodiments given below, are used to explain the principles of the present disclosure.

[0032] These and other features of the present disclosure will become apparent from the following description of the preferred forms of the embodiments given as non-limiting examples with reference to the accompanying drawings.

[0033] It should also be understood that although the present disclosure has been described with reference to some specific examples, those skilled in the art can surely implement many other equivalent forms of the present disclosure, which have the features as described in the claims and thus are all within the protection scope defined thereby.

[0034] When combined with the accompanying drawings, the above and other aspects, features, and advantages of the present disclosure will become more apparent in view of the following detailed description.

[0035] Hereinafter, specific embodiments of the present disclosure will be described with reference to the accompanying drawings; however, it should be understood that the embodiments applied are merely examples of the present disclosure and can be implemented in various ways. Well-known and / or repetitive functions and structures are not described in detail to avoid obscuring the present disclosure with unnecessary or redundant details. Therefore, the specific structural and functional details applied herein are not intended to be limiting, but merely serve as a basis for the claims and a representative basis for teaching those skilled in the art to use the present disclosure in substantially any suitable detailed structure in a variety of ways.

[0036] This specification may use the phrases "in one embodiment", "in another embodiment", "in yet another embodiment", or "in other embodiments", which may each refer to one or more of the same or different embodiments according to the present disclosure.

[0037] The first embodiment of the present disclosure provides a control method for rear-wheel active steering. The control method is used for a vehicle, which can be a general engine-driven vehicle, a hybrid vehicle, a pure electric vehicle, or various other vehicles. The control method involved in this embodiment can be separately set in the vehicle. For example, it can be set through the rear-wheel steering angle control mode, and the user can choose to enter or not enter the rear-wheel steering angle control mode in any way. As Figure 1 shown, the control method includes:

[0038] S101. Based on the actual value of the front-wheel steering angle and the actual vehicle speed of the vehicle, determine the vehicle stability parameters of the vehicle. The vehicle stability parameters at least include a yaw rate set value and a sideslip angle set value of the center of mass.

[0039] In this step, based on the actual value of the front-wheel steering angle and the actual vehicle speed of the vehicle, determine the vehicle stability parameters of the vehicle. The vehicle stability parameters at least include a yaw rate set value and a sideslip angle set value of the center of mass. Specifically, the actual value of the front-wheel steering angle here represents the steering intention of the user driving the vehicle. As Figure 2 shown, the actual value of the front-wheel steering angle is obtained through the following method:

[0040] S201. Obtain the actual value of the steering wheel angle.

[0041] In this step, obtain the actual value of the steering wheel angle. Here, first, the actual steering wheel angle δ sw of the user driving the vehicle can be obtained. The actual steering wheel angle δ sw represents the actual steering intention or steering demand of the user driving the vehicle, and it can be obtained through a sensing device provided on the steering wheel.

[0042] S202. Based on the actual value of the steering wheel angle and the steering system transmission ratio, determine the actual value of the front-wheel steering angle.

[0043] After obtaining the actual value of the steering wheel angle through the above step S201, in this step, based on the actual value of the steering wheel angle and the steering system transmission ratio, determine the actual value of the front-wheel steering angle. Specifically, input the actual steering wheel angle δ sw into, for example, a steering wheel angle - front-wheel steering angle conversion module to output the actual value of the front-wheel steering angle δ f of the vehicle, that is, convert the steering situation of the steering wheel into the actual value of the front-wheel steering angle of the vehicle. Among them, the relationship between the actual value of the front-wheel steering angle δ f and the actual steering wheel angle δ sw is as follows:

[0044] δ f = δ sw Z1

[0045] where Z1 is the steering system transmission ratio of the vehicle.

[0046] Furthermore, in step S101, the actual vehicle speed value V of the vehicle can also be obtained in advance. In step S101, the actual front wheel steering angle value δ f and the actual vehicle speed value V are input into, for example, the vehicle steady-state calculation module to output the yaw rate set value γ ref and the sideslip angle set value β ref . Wherein, the vehicle steady-state calculation module here can calculate separately according to the actual vehicle speed value V. For this purpose, as Figure 3 shown, this step further includes:

[0047] S301, comparing the actual vehicle speed value with the vehicle speed threshold.

[0048] In this step, the actual vehicle speed value is compared with the vehicle speed threshold. Specifically, the vehicle speed threshold here can be determined according to the actual situation. For example, it can be set to 30 km / h.

[0049] S302, respectively determining the vehicle steady-state parameters based on the judgment result.

[0050] After comparing the actual vehicle speed value with the vehicle speed threshold through the above step S301, in this step, the vehicle steady-state parameters are respectively determined based on the judgment result. Specifically, when the actual vehicle speed value V is less than the switching speed threshold V b in the rear wheel steering angle control mode (here, for example, V b = 30 km / h), it is defined as the low-speed flexible driving condition in this vehicle speed range. When the actual front wheel steering angle value is δ f at this time, the yaw rate set value γ ref and the sideslip angle set value β ref obtained after the vehicle reaches the steady state are calculated by the following method:

[0051]

[0052] Wherein, L1 here is the distance from the center of mass of the vehicle to the center of the front wheels, L2 is the distance from the center of mass of the vehicle to the center of the rear wheels, K1 is the front wheel cornering stiffness, K2 is the rear wheel cornering stiffness, μ is the road surface adhesion coefficient, g is the acceleration due to gravity, and m is the vehicle mass. In addition, based on the above formula, it is also necessary to establish the yaw rate set value γ ref and the sideslip angle set value β refThe boundary conditions are as follows:

[0053]

[0054] When the actual vehicle speed V is greater than or equal to the switching speed threshold V in the rear wheel steering angle control mode b it is defined as a high-speed stable driving condition within this vehicle speed range. When the actual front wheel steering angle is δ f when the given yaw rate γ obtained after the vehicle reaches a steady state ref and the given sideslip angle β of the center of mass ref are calculated by the following method:

[0055]

[0056] β ref = 0

[0057] Here, the given yaw rate γ ref and the given sideslip angle β of the center of mass ref have the boundary conditions as described above.

[0058] S102. Input the vehicle steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed into a specified model to determine the vehicle's steering stability parameters. The steering stability parameters at least include the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle side force.

[0059] After determining the vehicle's steady-state parameters based on the actual front wheel steering angle and the actual vehicle speed of the vehicle through the above step S101, where the vehicle's steady-state parameters at least include the given yaw rate and the given sideslip angle of the center of mass, in this step, input the vehicle's steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed into a specified model to determine the vehicle's steering stability parameters. The steering stability parameters at least include the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle side force. Here, the steering stability parameters have corresponding determination methods based on different actual vehicle speeds.

[0060] Specifically, determine the vehicle's steering stability parameters based on the vehicle's steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed. As Figure 4 shown, it includes:

[0061] S401. When the actual vehicle speed is less than the vehicle speed threshold, input the actual front wheel steering angle and the actual vehicle speed into a function model to determine the target value of the rear wheel steering angle and the target value of the compensating yaw moment.

[0062] In this step, when the actual vehicle speed is less than the vehicle speed threshold, the actual front wheel steering angle and the actual vehicle speed are input into the function model to determine the target rear wheel steering angle and the target compensating yaw moment. Specifically, the vehicle speed threshold here can be determined according to the actual situation, for example, it can be set to 30 or 40 km / h.

[0063] When the actual vehicle speed V is less than the switching speed threshold V of the rear wheel steering angle control mode b (here, for example, V b = 30 km / h), it is defined as the low-speed flexible driving condition within this vehicle speed range. Here, the target rear wheel steering angle δ rref has a, for example, linear proportional relationship with the actual vehicle speed V and the actual front wheel steering angle δ f That is, the larger the actual vehicle speed V, the smaller the target rear wheel steering angle δ rref , and the larger the actual front wheel steering angle δ f , the larger the target rear wheel steering angle δ rref . In this way, a calibration MAP is formed between the target rear wheel steering angle δ rref and the actual vehicle speed V and the actual front wheel steering angle δ f to form the formula δ rref = f1(V, δ f ); at the same time, the target compensating yaw moment M z here is 0.

[0064] S402. When the actual vehicle speed is greater than or equal to the first vehicle speed threshold, the vehicle steady-state parameters, the actual front wheel steering angle, the actual yaw rate, and the actual sideslip angle of the center of mass are input into the prediction model to determine the target rear wheel steering angle, the target compensating yaw moment, and the vehicle side force.

[0065] In this step, when the actual vehicle speed is greater than or equal to the first vehicle speed threshold, the vehicle steady-state parameters, the actual front wheel steering angle, and the actual vehicle speed are input into the prediction model to determine the target rear wheel steering angle, the target compensating yaw moment, and the vehicle side force.

[0066] Here, for example, it is implemented by the steering stability control module based on the model predictive control method. The inputs here are the given yaw rate γ ref and the given sideslip angle β ref of the vehicle steady-state parameters, the actual front wheel steering angle δ f , and the actual vehicle speed V. The output steering stability parameters of the vehicle include the target rear wheel steering angle δ rref, the target value M of the compensating yaw moment z and the lateral force F of the vehicle y . It should be noted that in this step, the actual yaw rate γ and the actual sideslip angle β of the center of mass also need to be input into the prediction model as state variables.

[0067] Specifically, the vehicle steady-state parameters, the actual value of the front wheel steering angle, and the actual value of the vehicle speed are input into the prediction model to determine the target value δ of the rear wheel steering angle rref , the target value M of the compensating yaw moment z and the lateral force F of the vehicle y , as Figure 5 shown, including:

[0068] S501, establish a two-degree-of-freedom vehicle model and a non-linear simplified tire model.

[0069] In this step, a two-degree-of-freedom vehicle model and a non-linear simplified tire model are established. Specifically, when the actual vehicle speed V is greater than, for example, the switching speed threshold V of the rear wheel steering angle control mode b (here, for example, V b = 30 km / h), it is defined as a high-speed stable driving condition within this vehicle speed range. In this step, first establish the two-degree-of-freedom vehicle model as follows:

[0070]

[0071] where I z is the moment of inertia of the vehicle rotating about the center of mass along the Z-axis, F yf is the lateral force of the front wheels, F yr is the lateral force of the rear wheels, L1 is the distance from the center of mass to the front axle, L2 is the distance from the center of mass to the rear axle, and m is the total mass of the vehicle.

[0072] Furthermore, establish the tire model as follows, for example, establish the Fiala non-linear simplified tire model.

[0073] [[ID=4s]]

[0074] where K1 is the front wheel cornering stiffness, K2 is the rear wheel cornering stiffness, α f is the front wheel tire slip angle, α r is the rear wheel tire slip angle, F yf is the lateral force of the front wheels, F yr is the lateral force of the rear wheels, μ is the road surface adhesion coefficient, F z is the vertical load; specifically, the calculation methods of F z , α f , α r are as follows:

[0075]

[0076] S502. Establish a prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model.

[0077] After establishing the two-degree-of-freedom vehicle model and the non-linear simplified tire model through the above step S501, in this step, a prediction model is established based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model. Based on the above formula, the two-degree-of-freedom vehicle model is discretized to establish the prediction model as follows:

[0078]

[0079] where the state variables are \(x = [x_1, x_2]\) T = [β, γ] T , and the control variables are \(u = [u_1, u_2]\) T =

[0080] [δ rref , M z T , T s , and \(T\) is the sampling time (for example, it can be taken as 0.001 s);

[0081] S503. Establish an objective function based on the prediction model.

[0082] After establishing the prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model through the above step S502, an objective function is established based on the prediction model. Specifically, before establishing the objective function, the prediction horizon \(N\) p (\(N\) p = 8), the control horizon \(N\) c (\(N\) c = 2) are set, \(k\) is the current sampling time, \(k + 1\) is the next sampling time, and the objective function is established as follows:

[0083]

[0084] where \(J\) is the value of the objective function, the minimum value that needs to be calculated in real time at each sampling time. When \(J\) takes the minimum value, the control variables \(u = [u_1, u_2]\) at the current time are determined T ​Values. After the calculation of the current moment is completed, the calculation of the next moment is carried out. P1 is the weighting coefficient of the yaw rate, P2 is the weighting coefficient of the sideslip angle of the center of mass, P3 is the weighting coefficient of the change in the rear wheel steering angle, and P4 is the weighting coefficient of the change in the target value of the compensating yaw moment. The above coefficients are all obtained from the experience of engineering practice. In this embodiment, different P values can also be taken under different actual vehicle speeds. For example, in a relatively low-speed driving condition, P1 = 2P2 = 10P3 = 0.1P4 = 0.02, and in a relatively high-speed stable driving condition, it is switched to P1 = 10P2 = 1P3 = 0.1P4 = 0.02.

[0085] S504. Based on the objective function and the control quantity constraints, determine the control quantity, where the control quantity is the target value of the rear wheel steering angle and the target value of the compensating yaw moment.

[0086] After establishing the objective function based on the prediction model through the above step S503, in this step, based on the objective function and the control quantity constraints, determine the control quantity, where the control quantity is the target value of the rear wheel steering angle and the target value of the compensating yaw moment. Specifically, first establish the control quantity constraints around the objective function involving the control quantity as follows:

[0087] |u1(k i )|≤δ rmax (k + 1 ≤ k i ≤ k + N c )

[0088] |u2(k i )|≤M zmax (k + 1 ≤ k i ≤ k + N c )

[0089] Where, δ rmax is the maximum value of the absolute value of the rear wheel steering angle, and M zmax is the maximum value of the absolute value of the target value of the compensating yaw moment, which is determined by the physical characteristics of the vehicle and the actuator. For example, in a relatively low-speed driving condition, take δ rmax = 0.1M zmax = 2000; in a relatively high-speed driving condition, it is switched to δ rmax = 0.05M zmax = 2000.

[0090] The embodiments of the present disclosure ensure the stability of vehicle handling in the case of rear wheel steering by restricting the control quantity so that it does not exceed the physical limits of the vehicle and the actuator.

[0091] Furthermore, the above steps further include:

[0092] Determine the vehicle lateral force based on the rear wheel steering angle target value and the non-linear simplified tire model.

[0093] Specifically, after obtaining the rear wheel steering angle target value δ rref the calculated rear wheel steering angle target value δ rref is substituted into the above non-linear simplified tire model to calculate and obtain the vehicle lateral force F y as:

[0094] F y = F yf + F yr

[0095] In another embodiment, as Figure 6 shown, it further includes:

[0096] S601, obtain the actual operating parameters of the vehicle.

[0097] S602, determine the actual value of the center of mass side slip angle based on the vehicle lateral force, the actual value of the front wheel steering angle, and the actual operating parameters.

[0098] S603, adjust the steering stability parameter based on the center of mass side slip angle.

[0099] The above steps S601 - S603 are mainly used to adjust the steering stability parameter through the vehicle lateral force, so as to achieve closed-loop control, which is realized by a center of mass side slip angle calculation module here. Specifically, the center of mass side slip angle calculation module here is designed using a non-linear state observer, and its input parameters are the longitudinal acceleration a x of the actual operating parameters, the actual vehicle speed V, and the lateral acceleration a y , and also include the actual yaw rate γ, the actual front wheel steering angle δ f and the vehicle lateral force F y , and the output is the actual value of the center of mass side slip angle β.

[0100] Furthermore, the actual value of the center of mass side slip angle β here is realized by an iterative method. For example, the calculation method of the actual value of the center of mass side slip angle β is:

[0101] Set k as the current sampling time and k + 1 as the next sampling time. After the calculation at the current time is completed, the calculation at the next time is carried out, which is represented by the following method:

[0102]

[0103] where is the estimated value of the vehicle longitudinal speed at the previous time, is the estimated value of the vehicle longitudinal speed at the current time, is the estimated value of the vehicle's lateral speed at the previous moment, is the estimated value of the vehicle's lateral speed at the current moment, K x is the correction parameter for estimating the vehicle's longitudinal speed, K y is the correction parameter for estimating the vehicle's lateral speed.

[0104] S103. Control the rear-wheel steering of the vehicle based on the steering stability parameter.

[0105] After inputting the vehicle's steady-state parameter, the actual value of the front-wheel steering angle, and the actual value of the vehicle speed into the specified model to determine the steering stability parameter of the vehicle through the above step S102, in this step, control the rear-wheel steering of the vehicle based on the steering stability parameter.

[0106] In this step, as Figure 7 shown, it specifically includes:

[0107] S701. Determine the braking pressure based on the target value of the rear-wheel steering angle and the target value of the compensating yaw moment.

[0108] In this step, determine the actual value of the rear-wheel steering angle and the braking pressure based on the target value of the rear-wheel steering angle and the target value of the compensating yaw moment. In this step, for example, it can be implemented by an actuator control module. The input of the actuator control module here is the target value of the rear-wheel steering angle δ rref and the target value of the compensating yaw moment M z , and determine the actual value of the rear-wheel steering angle and the braking pressure.

[0109] S702. Control the rear-wheel steering of the vehicle based on the actual value of the rear-wheel steering angle, the target value of the compensating yaw moment, and the braking pressure.

[0110] After determining the braking pressure based on the target value of the rear-wheel steering angle and the target value of the compensating yaw moment through the above step S701, in this step, control the rear-wheel steering of the vehicle based on the actual value of the rear-wheel steering angle and the braking pressure. Specifically, the rear-wheel steering gear drives the steering tie rod in real time through the rear-wheel steering gear assist motor according to the target value of the rear-wheel steering angle, and the four-wheel brakes convert the target value of the compensating yaw moment into the braking pressure of the four wheel hubs for braking.

[0111] In an actual implementation, the driver turns the steering wheel. The steering wheel angle sensor is integrated in the vehicle's steering system and rotates at the same speed as the steering wheel. It sends the actual value of the steering wheel angle δ sw to the steering wheel angle - front-wheel steering angle conversion module to generate the actual value of the front-wheel steering angle δ f . The actual value of the front-wheel steering angle δf and send the actual vehicle speed value V to the vehicle steady-state calculation module.

[0112] Based on δ, the vehicle steady-state calculation module f calculates the yaw rate set value γ ref and the sideslip angle set value β of the center of mass ref and sends them to the steering stability control module.

[0113] The steering stability control module simultaneously receives the actual front wheel angle δ f , the actual yaw rate γ and the actual vehicle speed V sent by the inertial navigation unit integrated on the vehicle, and the actual sideslip angle β of the center of mass sent by the sideslip angle calculation module of the center of mass, and calculates two control quantities, the target value of the rear wheel angle δ rref and the target value of the compensating yaw moment M z , and sends them to the actuator control module.

[0114] The sideslip angle calculation module of the center of mass receives the longitudinal acceleration a sent by the inertial navigation unit x , the actual yaw rate γ, the actual vehicle speed V, the lateral acceleration a y , the lateral force F of the vehicle sent by the steering stability control module y , the actual front wheel angle δ sent by the steering wheel angle - front wheel angle conversion module f , and estimates the actual sideslip angle β of the center of mass.

[0115] The actuator control module controls the front wheel steering gear, the rear wheel steering gear, and the brakes of the four wheels for steering and pressure braking, and adjusts the vehicle attitude in real time. The inertial navigation unit sends the actual yaw rate γ at the current moment, the actual wheel speeds V of the four wheels wi (i = 1, 2, 3, 4), and the actual vehicle speed V to the vehicle steady-state calculation module, the steering stability control module, and the sideslip angle calculation module of the center of mass to achieve closed-loop control. In this way, in the embodiment of the present disclosure, while controlling the rear wheel angle, the control of the yaw moment is also increased and reflected in the braking pressure.

[0116] In the process of controlling the rear wheels of the vehicle, the embodiment of the present disclosure adopts a model predictive control method. While controlling the rear wheel angle, the control of the yaw moment is also increased, and the control of the braking pressure is carried out; in addition, through the hard constraints on multiple control quantities, the stability of vehicle handling in the case of rear wheel steering is ensured. In addition, the embodiment of the present disclosure also implements different control methods for different working conditions and driving modes and sets the limit ranges of the control quantities, further taking into account the vehicle stability performance under different working conditions.

[0117] The second embodiment of the present disclosure relates to a control device for rear-wheel active steering, which includes a vehicle steady-state parameter determination module, a steering stability parameter determination module, and a steering control module. These modules are coupled to each other. Specifically:

[0118] The vehicle steady-state parameter determination module is configured to determine the vehicle steady-state parameters of the vehicle based on the actual value of the front-wheel steering angle of the vehicle and the actual value of the vehicle speed. The vehicle steady-state parameters at least include a yaw rate set value and a centroid side slip angle set value;

[0119] The steering stability parameter determination module is configured to input the vehicle steady-state parameters, the actual value of the front-wheel steering angle, and the actual value of the vehicle speed into a specified model to determine the steering stability parameters of the vehicle. The steering stability parameters at least include a rear-wheel steering angle target value, a compensating yaw moment target value, and a vehicle side force;

[0120] The steering control module is configured to control the rear-wheel steering of the vehicle based on the steering stability parameters.

[0121] The vehicle steady-state parameter determination module includes:

[0122] A comparison unit configured to compare the actual value of the vehicle speed with a vehicle speed threshold;

[0123] A determination unit configured to respectively determine the vehicle steady-state parameters based on the judgment result.

[0124] The steering stability parameter determination module is specifically configured to, when the actual value of the vehicle speed is less than a first vehicle speed threshold, input the actual value of the front-wheel steering angle and the actual value of the vehicle speed into a function model to determine the rear-wheel steering angle target value; when the actual value of the vehicle speed is greater than or equal to the first vehicle speed threshold, input the vehicle steady-state parameters, the actual value of the front-wheel steering angle, and the actual value of the vehicle speed into a prediction model to determine the rear-wheel steering angle target value, the compensating yaw moment target value, and the vehicle side force.

[0125] Further, the steering stability parameter determination module includes:

[0126] A vehicle model establishment unit configured to establish a two-degree-of-freedom vehicle model and a non-linear simplified tire model;

[0127] A prediction model establishment unit configured to establish a prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model;

[0128] A target function establishment unit configured to establish a target function based on the prediction model;

[0129] A control quantity determination unit for determining a control quantity based on the objective function and control quantity constraints, where the control quantity is the target value of the rear wheel steering angle and the target value of the compensating yaw moment.

[0130] Further, it further includes:

[0131] An acquisition module for acquiring the actual operating parameters of the vehicle;

[0132] An adjustment module for determining the actual value of the center of mass side slip angle based on the lateral force of the vehicle, the actual value of the front wheel steering angle, and the actual operating parameters; and adjusting the steering stability parameters based on the center of mass side slip angle.

[0133] Further, the actual value of the front wheel steering angle is obtained in the following manner: obtaining the actual value of the steering wheel angle; and determining the actual value of the front wheel steering angle based on the actual value of the steering wheel angle and the steering system transmission ratio.

[0134] The steering control module includes:

[0135] A brake pressure determination unit for determining the brake pressure based on the target value of the rear wheel steering angle and the target value of the compensating yaw moment;

[0136] A steering control unit for controlling the rear wheel steering of the vehicle based on the actual value of the rear wheel steering angle, the target value of the compensating yaw moment, and the brake pressure.

[0137] In the process of controlling the rear wheels of the vehicle in the embodiments of the present disclosure, a model predictive control method is adopted. While controlling the rear wheel steering angle, the control of the yaw moment is also increased, and the control of the brake pressure is carried out. In addition, through the hard constraints on multiple control quantities, the stability of vehicle handling in the case of rear wheel steering is ensured. In addition, the embodiments of the present disclosure also implement different control methods for different working conditions and driving modes and set the limit ranges of control quantities, which better takes into account the vehicle stability performance under different working conditions.

[0138] The third embodiment of the present disclosure provides a storage medium, which is a computer-readable medium and stores a computer program. When the computer program is executed by a processor, it implements the method provided in the first embodiment of the present disclosure, including the following steps S11 to S13:

[0139] S11, determining the vehicle steady-state parameters of the vehicle based on the actual value of the front wheel steering angle of the vehicle and the actual value of the vehicle speed, where the vehicle steady-state parameters at least include the given value of the yaw rate and the given value of the center of mass side slip angle;

[0140] S12. Input the vehicle's steady-state parameters, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a specified model to determine the vehicle's steering stability parameters. The steering stability parameters at least include the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle side force.

[0141] S13. Control the rear wheel steering of the vehicle based on the steering stability parameters.

[0142] Furthermore, when the computer program is executed by a processor, it implements the other methods provided in the first embodiment of the present disclosure.

[0143] In the process of controlling the rear wheels of the vehicle in the embodiments of the present disclosure, a model predictive control method is adopted. While controlling the rear wheel steering angle, the control of the yaw moment is also increased, and the control of the braking pressure is carried out. In addition, through the hard constraints on multiple control variables, the stability of the vehicle operation in the case of rear wheel steering is ensured. In addition, the embodiments of the present disclosure also implement different control methods for different working conditions and driving modes and set the limit ranges of the control variables, which better takes into account the vehicle stability performance under different working conditions.

[0144] The fourth embodiment of the present disclosure provides an electronic device. The electronic device at least includes a memory and a processor. A computer program is stored on the memory. When the processor executes the computer program on the memory, it implements the methods provided in any embodiment of the present disclosure. Exemplarily, the computer program steps of the electronic device are as follows: S21 to S23:

[0145] S21. Based on the actual value of the front wheel steering angle of the vehicle and the actual value of the vehicle speed, determine the vehicle's steady-state parameters of the vehicle. The vehicle's steady-state parameters at least include the given value of the yaw rate and the given value of the sideslip angle of the center of mass.

[0146] S22. Input the vehicle's steady-state parameters, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a specified model to determine the vehicle's steering stability parameters. The steering stability parameters at least include the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle side force.

[0147] S23. Control the rear wheel steering of the vehicle based on the steering stability parameters.

[0148] Furthermore, the processor also executes the computer program in the above-mentioned third embodiment.

[0149] In the process of controlling the rear wheels of a vehicle in the embodiments of the present disclosure, a model predictive control method is adopted. While controlling the rear wheel steering angle, the control of the yaw moment is also increased, and the brake pressure is controlled. In addition, through the hard constraints on multiple control variables, the stability of vehicle handling in the case of rear wheel steering is ensured. In addition, the embodiments of the present disclosure also implement different control methods for different working conditions and driving modes and set the limit ranges of control variables, further taking into account the vehicle stability performance under different working conditions.

[0150] The above storage medium may be included in the above electronic device; or it may exist independently without being assembled into the electronic device.

[0151] The above storage medium carries one or more programs. When the above one or more programs are executed by the electronic device, the electronic device is caused to: obtain at least two Internet protocol addresses; send a node evaluation request including at least two Internet protocol addresses to a node evaluation device, wherein the node evaluation device selects an Internet protocol address from the at least two Internet protocol addresses and returns it; receive the Internet protocol address returned by the node evaluation device; wherein the obtained Internet protocol address indicates an edge node in a content delivery network.

[0152] Alternatively, the above storage medium carries one or more programs. When the above one or more programs are executed by the electronic device, the electronic device is caused to: receive a node evaluation request including at least two Internet protocol addresses; select an Internet protocol address from the at least two Internet protocol addresses; return the selected Internet protocol address; wherein the received Internet protocol address indicates an edge node in a content delivery network.

[0153] Computer program code for performing the operations of the present disclosure may be written in one or more programming languages or combinations thereof. The above programming languages include, but are not limited to, object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code may be executed entirely on the passenger computer, partially on the passenger computer, executed as an independent software package, partially on the passenger computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the passenger computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (for example, by connecting through an Internet service provider via the Internet).

[0154] It should be noted that the above storage medium in the present disclosure may be a computer-readable signal medium, a computer-readable storage medium, or any combination of the two. A computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present disclosure, a computer-readable storage medium may be any tangible medium that contains or stores a program, and this program can be used by or in combination with an instruction execution system, apparatus, or device. In the present disclosure, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries computer-readable program code. Such a propagated data signal may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any storage medium other than a computer-readable storage medium, and this computer-readable signal medium can send, propagate, or transmit a program for use by or in combination with an instruction execution system, apparatus, or device. The program code contained on the storage medium can be transmitted by any suitable medium, including but not limited to: wires, optical cables, RF (radio frequency), etc., or any suitable combination of the above.

[0155] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0156] The units involved in the embodiments of the present disclosure can be implemented in software or in hardware. In some cases, the name of a unit does not constitute a limitation on the unit itself.

[0157] The functions described above herein can be performed, at least in part, by one or more hardware logic components. By way of example, and without limitation, the types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on a chip (SOCs), complex programmable logic devices (CPLDs), and the like.

[0158] In the context of the present disclosure, a machine-readable medium may be a tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0159] The above description is only of the preferred embodiments of the present disclosure and an illustration of the technical principles applied. Those skilled in the art should understand that the scope of the disclosure involved in the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosure concept. For example, a technical solution formed by mutually replacing the above features with (but not limited to) technical features having similar functions disclosed in the present disclosure.

[0160] In addition, although the operations are depicted in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in sequential order. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present disclosure. Certain features described in the context of separate embodiments may also be implemented combinatorially in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments.

[0161] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. On the contrary, the specific features and acts described above are merely example forms for implementing the claims.

[0162] The above has described in detail multiple embodiments of the present disclosure, but the present disclosure is not limited to these specific embodiments. Based on the concept of the present disclosure, those skilled in the art can make various variations and modifications to the embodiments, and these variations and modifications should all fall within the scope protected by the present disclosure.

Claims

1. A control method for rear-wheel active steering, characterized in that including: determining a vehicle steady-state parameter of the vehicle based on an actual value of a front wheel steering angle of the vehicle and an actual value of a vehicle speed of the vehicle, where the vehicle steady-state parameter at least includes a given value of yaw rate and a given value of sideslip angle of the center of mass; inputting the vehicle steady-state parameter, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a specified model to determine a steering stability parameter of the vehicle, where the steering stability parameter at least includes a target value of a rear wheel steering angle, a target value of a compensating yaw moment, and a vehicle lateral force; controlling rear wheel steering of the vehicle based on the steering stability parameter; wherein, the inputting the vehicle steady-state parameter, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a prediction model to determine the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle lateral force includes: establishing a two-degree-of-freedom vehicle model and a non-linear simplified tire model; establishing a prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model; establishing an objective function based on the prediction model; determining a control quantity based on the objective function and control quantity constraints, where the control quantity is the target value of the rear wheel steering angle and the target value of the compensating yaw moment; the non-linear simplified tire model is defined as: Among them, K1 is the cornering stiffness of the front wheels, K2 is the cornering stiffness of the rear wheels, α f is the cornering angle of the front-wheel tires, α r is the cornering angle of the rear-wheel tires, F yf is the lateral force of the front wheels, F yr is the lateral force of the rear wheels, μ is the road adhesion coefficient, F z is the vertical load.

2. The control method according to claim 1, wherein the determining the vehicle steady-state parameter of the vehicle based on the actual value of the front wheel steering angle of the vehicle and the actual value of the vehicle speed of the vehicle includes: comparing the actual value of the vehicle speed with a vehicle speed threshold; respectively determining the vehicle steady-state parameter based on a judgment result.

3. The control method according to claim 1, wherein determining the steering stability parameter of the vehicle based on the vehicle steady-state parameter, the actual value of the front wheel steering angle, and the actual value of the vehicle speed includes: when the actual value of the vehicle speed is less than a first vehicle speed threshold, inputting the actual value of the front wheel steering angle and the actual value of the vehicle speed into a function model to determine the target value of the rear wheel steering angle; when the actual value of the vehicle speed is greater than or equal to the first vehicle speed threshold, inputting the vehicle steady-state parameter, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a prediction model to determine the target value of the rear wheel steering angle, the target value of the compensating yaw moment, and the vehicle lateral force.

4. The control method according to claim 1, wherein also including: acquiring an actual operating parameter of the vehicle; determining an actual value of the sideslip angle of the center of mass based on the vehicle lateral force, the actual value of the front wheel steering angle, and the actual operating parameter; adjusting the steering stability parameter based on the sideslip angle of the center of mass.

5. The control method according to claim 1, wherein the actual value of the front wheel steering angle is acquired by the following method: acquiring an actual value of the steering wheel angle; determining the actual value of the front wheel steering angle based on the actual value of the steering wheel angle and a steering system transmission ratio.

6. The control method according to claim 1, wherein the controlling the rear wheel steering of the vehicle based on the steering stability parameter includes: determining a braking pressure based on the target value of the rear wheel steering angle and the target value of the compensating yaw moment; controlling the rear wheel steering of the vehicle based on the actual value of the rear wheel steering angle, the target value of the compensating yaw moment, and the braking pressure.

7. A control device for rear-wheel active steering, characterized in that, including: A vehicle steady-state parameter determination module, configured to determine vehicle steady-state parameters of the vehicle based on an actual value of a front wheel steering angle of the vehicle and an actual value of a vehicle speed of the vehicle, where the vehicle steady-state parameters at least include a yaw rate set value and a sideslip angle of the center of mass set value; A steering stability parameter determination module, configured to input the vehicle steady-state parameters, the actual value of the front wheel steering angle, and the actual value of the vehicle speed into a specified model to determine steering stability parameters of the vehicle, where the steering stability parameters at least include a rear wheel steering angle target value, a compensating yaw moment target value, and a vehicle lateral force; A steering control module, configured to control rear wheel steering of the vehicle based on the steering stability parameters; Wherein, the steering stability parameter determination module includes: A vehicle model establishment unit, configured to establish a two-degree-of-freedom vehicle model and a non-linear simplified tire model; A prediction model establishment unit, configured to establish a prediction model based on the two-degree-of-freedom vehicle model and the non-linear simplified tire model; An objective function establishment unit, configured to establish an objective function based on the prediction model; A control quantity determination unit, configured to determine a control quantity based on the objective function and control quantity constraints, where the control quantity is the rear wheel steering angle target value and the compensating yaw moment target value; Wherein, the non-linear simplified tire model is defined as: Among them, K1 is the cornering stiffness of the front wheels, K2 is the cornering stiffness of the rear wheels, α f is the cornering angle of the front-wheel tires, α r is the cornering angle of the rear-wheel tires, F yf is the lateral force of the front wheels, F yr is the lateral force of the rear wheels, μ is the road adhesion coefficient, F z is the vertical load.

8. A storage medium stores a computer program, characterized in that, When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

9. An electronic device, at least comprising a memory and a processor, wherein a computer program is stored on the memory, characterized in that When the processor executes the computer program on the memory, the steps of the method according to any one of claims 1 to 6 are implemented.

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