Distributed direct current driving control method and device, equipment and storage medium

Abstract

The application relates to a control method, device and equipment of a distributed direct drive and a storage medium, wherein the method comprises the following steps: determining a desired slip rate corresponding to a current driving condition of a vehicle; establishing a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle; selecting a sliding mode surface of a sliding mode control based on a vehicle slip rate, the desired slip rate, a vehicle yaw angular velocity and a desired yaw angular velocity; determining a reaching law function of the sliding mode control; determining a control function of the sliding mode control based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and controlling the vehicle based on the control function. Thus, the situation that the vehicle is unstable due to wheel slip can be effectively avoided, and the safety of the vehicle is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle sliding mode control, and particularly relates to a control method, device and equipment of distributed straight driving and a storage medium. BACKGROUND

[0002] Due to the advantage that four-wheel motors can be controlled individually, the discussion on distributed driving is gradually increasing in popularity. For a vehicle with distributed driving, the traditional control method has problems of low control precision and low accuracy. Therefore, a sliding mode variable structure control is proposed to control the vehicle with distributed driving, and good results are achieved.

[0003] However, in the process of straight driving, the wheels of the vehicle with distributed driving are still prone to slipping, which causes the vehicle to lose stability and poses a safety hazard. SUMMARY

[0004] The present application provides a control method of distributed straight driving, which can effectively avoid the situation that wheel slipping causes the vehicle to lose stability and improve the safety of the vehicle.

[0005] In a first aspect, the present application provides a control method of distributed straight driving, comprising:

[0006] determining an expected slip rate corresponding to a current driving condition of the vehicle;

[0007] establishing a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle;

[0008] selecting a sliding mode surface of sliding mode control based on a vehicle slip rate, the expected slip rate, a vehicle yaw angular velocity and an expected yaw angular velocity;

[0009] determining a reaching law function of the sliding mode control;

[0010] determining a control function of the sliding mode control based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and controlling the vehicle based on the control function.

[0011] In a second aspect, the present application provides a control device of distributed straight driving, comprising:

[0012] an expected slip rate determination module configured to determine an expected slip rate corresponding to a current driving condition of the vehicle;

[0013] a two-degree-of-freedom model establishment module configured to establish a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle;

[0014] a sliding mode surface selection module configured to select a sliding mode surface of the sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw rate, and a desired yaw rate;

[0015] a reaching law function determination module configured to determine a reaching law function of the sliding mode control;

[0016] a control function determination module configured to determine a control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model, and to control the vehicle based on the control function.

[0017] In a third aspect, an electronic device is provided, and the electronic device comprises:

[0018] a memory configured to store a computer program;

[0019] a processor configured to execute the computer program stored in the memory, and the computer program, when executed, implements the method provided in the embodiments of the present application.

[0020] In a fourth aspect, a computer readable storage medium is provided, and the computer readable storage medium stores a computer program, and the computer program, when executed by a processor, implements the method provided in the embodiments of the present application.

[0021] The above technical solutions provided in the embodiments of the present application have the following advantages compared with the prior art:

[0022] The technical solutions provided in the embodiments of the present application select a sliding mode surface of the sliding mode control based on a vehicle slip ratio, a desired slip ratio, a vehicle yaw rate, and a desired yaw rate, determine a control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model, and control the vehicle based on the control function, so that the vehicle slip ratio approaches the desired slip ratio, the vehicle yaw rate approaches the desired yaw rate, and the problem of vehicle instability caused by easy skidding is effectively avoided, and the safety of the vehicle is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the specification.

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced, and obviously, other drawings can be obtained by those skilled in the art without creative labor.

[0025] One or more embodiments are illustrated by way of example in the drawings and described herein in connection with the appended drawings, which are not to scale, where like references numerals designate corresponding, analogous, or like parts and in which:

[0026] Figure 1 A control method flow chart of the distributed straight driving provided by the embodiment of the present application;

[0027] Figure 2 A control method flow chart of the distributed straight driving provided by the embodiment of the present application;

[0028] Figure 3 A flow chart of selecting a sliding mode surface based on a vehicle slip rate, a desired slip rate, a vehicle yaw angular velocity and a desired yaw angular velocity to select a sliding mode control provided by the embodiment of the present application;

[0029] Figure 4 A flow chart of determining a control function of the sliding mode control based on a sliding mode surface, a reaching law function and a two-degree-of-freedom model provided by the embodiment of the present application;

[0030] Figure 5 A structural block diagram of the control device of the distributed straight driving provided by the embodiment of the present application;

[0031] Figure 6 A structural schematic diagram of the electronic device provided by the embodiment of the present application. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0033] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplicity, the components and arrangements of the particular examples are shown in the following description. These are, of course, merely examples and are not intended to limit the present application. Moreover, the present application can be practiced with the exact arrangement shown in the figures or with other similar arrangements. Finally, the present application can be implemented by any number of hardware and / or software components, and is not limited to the examples given herein.

[0034] In order to solve the technical problem that wheels of a distributed drive vehicle are prone to skidding and cause the vehicle to lose stability during driving in the prior art, the application provides a control method, device and equipment for distributed straight driving and a storage medium, which can effectively avoid the situation that wheels are prone to skidding and cause the vehicle to lose stability, and improve the safety of the vehicle.

[0035] Figure 1 A flow chart of a control method for distributed straight driving is provided in the embodiments of the application, and the method can be executed by a control device for distributed straight driving, which can be configured in an electronic device such as a vehicle-mounted device.

[0036] As shown in the figure, the technical scheme provided by the embodiments of the application includes the following steps: Figure 1

[0037] Step 101: determining a desired slip ratio of the vehicle.

[0038] In this embodiment, the desired slip ratio is used to define the standard that the wheels are basically not skidding. The desired slip ratio can be obtained by calibrating the value near the vertex of the curve of the vehicle slip ratio and the road adhesion coefficient obtained by the equation of the vehicle slip ratio and the road adhesion coefficient. The equation of the vehicle slip ratio and the road adhesion coefficient can use the existing equation in the prior art. For example, in the dry cement road, the equation of the vehicle slip ratio and the road adhesion coefficient can be u = 1.197 (1-e 23.168λ )-0.537λ; and for example, in the dry asphalt road, the equation of the vehicle slip ratio and the road adhesion coefficient can be u = 1.28 (1-e 23.99λ )-0.52λ. Wherein, u is the road adhesion coefficient; and λ is the vehicle slip ratio.

[0039] In the case of straight driving of the distributed drive vehicle, two driving conditions can be included, which are the uniform straight driving mode condition and the extreme speed mode condition. Different desired slip ratios can be used for different driving conditions, or the same desired slip ratio can be used.

[0040] In the case of using different desired slip ratios for different driving conditions, for the uniform straight driving mode condition, the desired slip ratios of the four wheels can be Wherein, the subscripts 1, 2, 3 and 4 represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel respectively, and the superscript * represents the desired value. For the extreme speed mode condition, the desired slip ratios of the four wheels can be Wherein, ΔS is obtained by calibration, and specifically, calibration can be performed on the curve of the slip ratio and the road adhesion coefficient. ΔS can be different for wheels on different roads; and ΔS can be between 0.01 and 0.05, and calibration can be performed every 0.01.​

[0041] In the case of adopting the same expected slip ratio in different forms of working conditions, the expected slip ratio adopted can be the same as that in the uniform straight driving mode working condition, or the same as that in the maximum speed mode working condition, or can be determined based on the expected slip ratios in the two working conditions (for example, based on the average value of the two), or other reasonable expected slip ratios can also be adopted.

[0042] Step 102: Establish a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle.

[0043] In the present embodiment, only the longitudinal motion dimension and the yaw motion dimension of the vehicle are considered for the distributed straight driving, and the lateral motion dimension of the vehicle is not considered.

[0044] Wherein, the two-degree-of-freedom model of the vehicle can be:

[0045] ma x = F x1 cosδ - F y1 sinδ + F x2 cosδ - F y2 sinδ + F x3 + F x4 =

[0046] F x - F f - F w - F i - F j ; (1)

[0047]

[0048] Wherein, the above formula (1) is the longitudinal kinematics equation of the vehicle; and the above formula (2) is the yaw kinematics equation of the vehicle.

[0049] In the above formula (1) and formula (2), wherein, F x1 , F x2 , F x3 and F x4 are driving forces of the four wheels respectively; F y1 , F y2 , F y3 and F y4 are lateral forces of the four wheels respectively;

[0050] F f is friction resistance, F w is air resistance, F i is slope resistance, F j is acceleration resistance; a xis the longitudinal acceleration of the vehicle; m is the mass of the vehicle; a is the distance from the front axle to the center of mass, b is the distance from the rear axle to the center of mass, δ is the front wheel steering angle, d is the distance between the left and right wheels; M zd is the yaw moment; I z is the moment of inertia; is the vehicle yaw angular velocity.

[0051] Step 103: selecting a sliding mode surface of the sliding mode control based on the vehicle slip ratio, the expected slip ratio, the vehicle yaw angular velocity, and the expected yaw angular velocity.

[0052] In the embodiment of the present application, the slip ratio is the proportion of the sliding component in the wheel movement; the braking process of the vehicle from pure rolling to locked drag sliding is a gradual process, which experiences three stages of pure rolling, rolling and sliding, and pure sliding. In order to evaluate the proportion of the wheel slip component, the slip ratio is commonly used to represent. The vehicle slip ratio can be understood as the actual slip ratio of the vehicle.

[0053] In the embodiment of the present application, in order to let the vehicle not slip as much as possible, not appear yaw motion as much as possible, and keep the target driving torque of the vehicle, the sliding mode surface can be selected by the vehicle slip ratio, the expected slip ratio, the vehicle yaw angular velocity, and the expected yaw angular velocity; wherein the sliding mode surface is a plane of S = 0, and the system is in a stable state on the sliding mode surface.

[0054] Specifically, in order to let the vehicle not slip as much as possible and effectively avoid the slippage caused by the vehicle speed, the vehicle slip ratio and the expected slip ratio are considered as factors for selecting the sliding mode surface; in order to let the vehicle not appear yaw motion and effectively avoid the slippage caused by the vehicle yaw motion, the vehicle yaw angular velocity and the expected angular velocity are considered as factors for selecting the sliding mode surface. Wherein, when the vehicle slip ratio reaches the expected slip ratio, the vehicle yaw angular velocity reaches the expected yaw angular velocity, the system is in a stable state, and the vehicle motion state reaches the expected target, therefore, the sliding mode surface is selected by the vehicle slip ratio, the expected slip ratio, the vehicle yaw angular velocity, and the expected yaw angular velocity.

[0055] Step 104: determining a reaching law function of the sliding mode control.

[0056] In the embodiment, a constant reaching law function can be used, or an exponential reaching law function can also be used, and generally a reaching law function can be used. Wherein, in order to reduce the disturbance of the system, a constant reaching function can be used, which can also simplify the subsequent operation.

[0057] Step 105: determining a control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model, and controlling the vehicle based on the control function.

[0058] In the embodiment, for the case of straight motion of the vehicle, the control function is a function of the longitudinal driving force of the vehicle; the longitudinal acceleration of the vehicle can be calculated through the sliding mode surface and the reaching law function, and the control function of the sliding mode control can be obtained by formula combination of the longitudinal acceleration and the two-degree-of-freedom model, and the vehicle is controlled through the control function. The control function can be a control function of the longitudinal driving force, and thus the vehicle is controlled through the control function, so that the vehicle yaw rate approaches the desired yaw rate, and the vehicle slip ratio approaches the desired slip ratio, so that the motion state of the vehicle reaches the desired target, avoiding the instability caused by easy slippage of the vehicle.

[0059] The technical scheme provided by the embodiment of the application selects the sliding mode surface of the sliding mode control through the vehicle slip ratio, the desired slip ratio, the vehicle yaw rate and the desired yaw rate, determines the control function of the sliding mode control through the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and controls the vehicle based on the control function, so that the vehicle yaw rate approaches the desired yaw rate, and the vehicle slip ratio approaches the desired slip ratio, so that the motion state of the vehicle reaches the desired target, effectively avoiding the instability problem caused by easy slippage of the vehicle, and improving the safety of the vehicle.

[0060] Figure 2 is a control method flowchart of the distributed straight driving provided by the embodiment of the application, which limits the desired slip ratio of the vehicle, as shown in Figure 2 The method comprises the following steps:

[0061] Step 201: determining the desired slip ratio of the vehicle corresponding to the current driving condition.

[0062] In the embodiment, the distributed driving has many bright functions due to the independent driving of the four motors, and the implementation logic of the basic functions is also different from that of the traditional vehicle. The desired slip ratios are different between different functions, and if the unified target slip ratio of the traditional vehicle is adopted to control the distributed vehicle, many bright functions cannot be implemented, and therefore different desired slip ratios can be determined for different functions.

[0063] In the case of straight driving of the distributed driving vehicle, two driving condition bright functions can be included, which are the uniform straight driving mode condition and the extreme speed mode condition. First, it can be judged whether the current driving condition is the uniform straight driving mode condition or the extreme speed mode condition. For the uniform straight driving mode condition, the value of the acceleration is less than an acceleration threshold value, the acceleration threshold value is small and close to 0, and the pedal opening degree change rate is less than a change rate threshold value, the change rate threshold value is close to 0. In this condition, the vehicle wheels need to have sufficient friction with the road surface to provide driving force, and the desired slip ratios of the four wheels can be: Wherein, the subscripts 1, 2, 3, 4 represent the front left wheel, the front right wheel, the rear left wheel and the rear right wheel respectively, and the superscript * represents the expected value.

[0064] For the extreme speed mode working condition, U<80m / s, i.e. the acceleration is greater than 2m / s 2 , the pedal opening rate of change is greater than 15° / s, and the speed of the vehicle is less than 80m / s. This mode increases the longitudinal moment when the vehicle accelerates to start, so that the vehicle can quickly reach the target speed, at which time the vehicle is prone to slipping and reaching the critical value. The expected slip ratio of the four wheels can be Wherein, ΔS is obtained by calibration, and ΔS can be different for wheels on different road surfaces; wherein, ΔS can be between 0.01 and 0.05, and can be calibrated every 0.01.

[0065] Step 202: Establish a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle.

[0066] Step 203: Select a sliding mode surface of the sliding mode control based on the vehicle slip ratio, the expected slip ratio, the vehicle yaw angular velocity and the expected yaw angular velocity.

[0067] Step 204: Determine the reaching law function of the sliding mode control.

[0068] Wherein, the introduction of steps 202-204 can refer to the above embodiments.

[0069] Step 205: Determine the control function of the sliding mode control based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model.

[0070] In an optional embodiment, before S201, it can also include: in the case that the vehicle is driving straight, determining the current driving working condition of the vehicle based on the longitudinal acceleration of the vehicle and the rate of change of the accelerator pedal opening. Specifically, if the longitudinal acceleration of the vehicle is less than a first acceleration threshold, and the rate of change of the accelerator pedal opening is less than a first rate of change threshold, it is judged as a uniform straight driving mode working condition, and if the longitudinal acceleration of the vehicle is greater than a second acceleration threshold, and the rate of change of the accelerator pedal opening is greater than a second rate of change threshold and the speed is less than a speed threshold, it is judged as an extreme speed mode working condition. Wherein, the first acceleration threshold can be a small value, for example, it can be a value close to 0, and the first rate of change threshold can be a small value, for example, it can be a value close to 0. The second acceleration threshold is greater than the first acceleration threshold, and the second rate of change threshold is greater than the first rate of change threshold. Wherein, the second acceleration threshold can be 2m / s 2 , the second rate of change threshold can be 15° / s; and the speed threshold can be 80m / s.

[0071] In the embodiment of the present application, if the current driving condition is the uniform straight driving mode, the acceleration resistance F j is 0 in the longitudinal kinematic equation of the two-degree-of-freedom model, in this condition, the vehicle longitudinal acceleration is determined based on the sliding surface and the approaching law function, and the control function of the sliding mode control is obtained by combining the vehicle longitudinal acceleration with the two-degree-of-freedom model.

[0072] In the embodiment of the present application, if the current driving condition is the extreme speed mode, the acceleration resistance F j is not 0 in the longitudinal kinematic equation of the two-degree-of-freedom model, in this condition, the vehicle longitudinal acceleration is determined based on the sliding surface and the approaching law function, and the control function of the sliding mode control is obtained by combining the vehicle longitudinal acceleration with the two-degree-of-freedom model.

[0073] In the related art, with the development of distributed functions, the expected slip rates of different functions are different, and the states of the vehicle are different, so that the traditional open-loop control, proportional-integral-derivative (PID) control method is used to make the control precision, accuracy and regulation ability of the vehicle low. The sliding mode variable structure control has the advantages of easy implementation, strong robustness, fast response speed and anti-interference. Compared with other conventional control strategies, the system structure is not fixed, although the system may have a shaking phenomenon, a reasonable approaching law function can be used to reduce the shaking of the system by switching the control amount according to the current state of the system. However, in the case of distributed straight driving, the vehicle is prone to skidding and instability, which causes safety hazards.

[0074] The embodiment of the present application considers the current driving condition, selects the sliding surface by the vehicle slip rate, the expected slip rate, the vehicle yaw speed and the expected yaw angular speed, obtains the control function in different driving conditions through the sliding surface, so that the state of the vehicle can reach the expected target, the instability problem caused by the skidding of the vehicle can be avoided, the vehicle can be controlled according to different driving conditions, the vehicle control is more in line with the actual situation, and the control precision is improved.

[0075] Figure 3 A flowchart of selecting a sliding surface of a sliding mode control based on a vehicle slip rate, an expected slip rate, a vehicle yaw angular speed and an expected yaw angular speed is provided in the embodiment of the present application, as shown in the flowchart of Figure 2 or Figure 1 based on the flowchart shown in Figure 3 , the method comprises the following steps:

[0076] Step 301: determining a slip rate deviation based on the vehicle slip rate and the expected slip rate.

[0077] In the embodiments of the present application, the vehicle slip ratio U is the speed of the vehicle; U w is the wheel speed of the vehicle. Different driving conditions correspond to different expected slip ratios, and the slip ratio deviation can be the difference between the vehicle slip ratio and the expected slip ratio.

[0078] Step 302: determining a yaw rate deviation based on the vehicle yaw rate and the expected yaw rate.

[0079] In the embodiments, the yaw rate deviation can be the difference between the vehicle yaw rate and the expected yaw rate. The expected yaw rate can be determined based on the steering wheel angle, the accelerator pedal opening, and other parameters of the driver. Specifically, the specific calculation of the expected yaw rate can refer to the following formula: where δ ′ is the steering wheel angle, L is the wheelbase of the vehicle, K is the stability coefficient of the vehicle, i is the wheel angle ratio, m is the mass of the vehicle, a and b are the distances from the mass center to the front axle and the rear axle, respectively, K f and K r are the stiffness of the front axle and the rear axle, respectively; u is the peak adhesion coefficient of the road surface; and g is the acceleration of gravity. The expected yaw rate can be obtained by the above formula.

[0080] Step 303: selecting a sliding mode surface of the sliding mode control based on the slip ratio deviation and the yaw rate deviation.

[0081] In an optional embodiment, the selecting a sliding mode surface of the sliding mode control based on the slip ratio deviation and the yaw rate deviation includes: weighting and combining the slip ratio deviation and the yaw rate deviation to obtain the sliding mode surface of the sliding mode control. Specifically, the slip ratio deviation and the yaw rate deviation can be linearly weighted and combined to obtain the sliding mode surface of the sliding mode control, or the slip ratio deviation and the yaw rate deviation can be exponentially weighted and combined, or the slip ratio deviation and the yaw rate deviation can be integrally weighted and combined, so as to achieve the expected yaw rate and the expected slip ratio, stabilize the system, and reduce system jitter.

[0082] In an optional embodiment, the weighting and combining the slip ratio deviation and the yaw rate deviation to obtain the sliding mode surface of the sliding mode control includes: determining the sliding mode surface of the sliding mode control based on the following formula:

[0083]

[0084] where Δλ = λ - λ * ; Δλ is the slip ratio deviation; λ is the slip ratio of the vehicle, U is the speed of the vehicle; U w is the wheel speed of the vehicle; wherein, λ * is the desired slip ratio; is the yaw rate deviation; is the yaw rate of the vehicle; is the desired yaw rate; S is the switching function of the sliding mode surface; and ξ is a weight coefficient, 0 < ξ < 1. In the above formula (3), the sliding mode surface is established by linearly weighting and combining the slip ratio deviation and the yaw rate deviation. In this way, the sliding mode surface established in this way can simplify the calculation and improve the response speed when calculating the control function.

[0085] Therefore, by selecting the sliding mode surface through the slip ratio deviation and the yaw rate deviation to calculate the control function, the motion state of the vehicle can reach the desired target, the slip ratio control of the vehicle is more stable, and the adaptability to the environment is stronger. The sliding mode surface is obtained by linearly weighting and combining the slip ratio deviation and the yaw rate, which can simplify the calculation and improve the response speed.

[0086] Figure 4 is a flowchart for determining a control function of a sliding mode control based on a sliding mode surface, a reaching law function and a two-degree-of-freedom model provided by the embodiment of the present application, and Figure 2 on the basis of the flowchart shown in Figure 4 , the method comprises the following steps:

[0087] Step 401: determining a dynamic equation of the sliding mode control based on the sliding mode surface.

[0088] In an optional embodiment, the step of determining the dynamic equation of the sliding mode control based on the sliding mode surface comprises: obtaining the dynamic equation of the sliding mode control by taking the first-order derivative of the sliding mode surface. Specifically, when the state reaches the sliding mode surface, the sliding mode control enters the sliding mode at this time, and the dynamic equation of the sliding mode control can be obtained by taking the first-order derivative of the sliding mode surface.

[0089] Step 402: determining the longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function and the integral function of the longitudinal speed of the vehicle.

[0090] In the embodiment, in order to reduce the disturbance of the system, a constant-speed reaching law function can be used.

[0091] In an optional embodiment, the step of determining the longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function and the integral function of the longitudinal speed of the vehicle comprises: determining the longitudinal acceleration of the vehicle based on the following formula:

[0092]

[0093] wherein the dynamic equation of the sliding mode control is: wherein, is the first derivative of the vehicle slip ratio; U is the speed of the vehicle, wherein U = U x ; U w is the wheel speed of the vehicle; is the first derivative of the desired slip ratio; is the first derivative of the vehicle yaw rate; is the first derivative of the desired yaw rate;

[0094] the approaching law function is a constant speed approaching law function, which is k > 0; k is a design parameter of the sliding mode controller; wherein k determines the speed of the system reaching the sliding surface, the greater k is, the faster the speed of reaching the sliding surface is.

[0095] the integral function of the longitudinal speed of the vehicle is: wherein U x is the longitudinal speed of the vehicle, U x0 is the initial longitudinal speed of the vehicle; a x is the longitudinal acceleration of the vehicle; the vehicle longitudinal acceleration can be obtained through the above formula (4).

[0096] Step 403: determining the control function of the sliding mode control based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model and the current driving condition.

[0097] In this embodiment, the longitudinal acceleration of the vehicle is combined with the two-degree-of-freedom model to obtain the control function of the sliding mode control. In the case that the current driving condition is the uniform straight driving mode condition, the acceleration resistance in the two-degree-of-freedom model is 0; in the case that the current driving condition is the extreme speed mode, the acceleration resistance in the two-degree-of-freedom model is not 0.

[0098] The control function of the sliding mode control is determined based on the following formula:

[0099]

[0100] wherein F f = Wf; wherein W = mg; wherein m is the mass of the vehicle; g is the acceleration of gravity; f is the rolling friction coefficient, F x is the control function;

[0101] In the case that the current driving condition is the uniform straight driving mode condition, F i = 0; F j = 0; In a case where the current driving condition is the extreme speed mode, F i = 0,

[0102] wherein C D is a drag coefficient of the vehicle, A f is a windward area of the vehicle; and p a is air density.

[0103] Thus, by calculating the vehicle longitudinal acceleration, and determining the control function of the sliding mode control through the vehicle longitudinal acceleration and the two-degree-of-freedom model, the calculation logic can be simplified, and the response speed can be improved.

[0104] Figure 5 is a structure block diagram of a control device of a distributed straight driving provided by an embodiment of the present application, as shown in the figure, comprising: an expected slip rate determination module 510, a two-degree-of-freedom model establishment module 520, a sliding mode surface selection module 530, a reaching law function determination module 540 and a control function determination module 550. Figure 5

[0105] The expected slip rate determination module 510 is configured to determine an expected slip rate corresponding to a current driving condition of the vehicle.

[0106] The two-degree-of-freedom model establishment module 520 is configured to establish a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle.

[0107] The sliding mode surface selection module 530 is configured to select a sliding mode surface of the sliding mode control based on a vehicle slip rate, the expected slip rate, a vehicle yaw angular velocity and an expected yaw angular velocity.

[0108] The reaching law function determination module 540 is configured to determine a reaching law function of the sliding mode control.

[0109] The control function determination module 550 is configured to determine a control function of the sliding mode control based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and control the vehicle based on the control function.

[0110] In a possible embodiment, the sliding mode surface selection module 530 is specifically configured to:

[0111] determine a slip rate deviation based on the vehicle slip rate and the expected slip rate;

[0112] determine a yaw angular velocity deviation based on the vehicle yaw angular velocity and the expected yaw angular velocity;

[0113] select the sliding mode surface of the sliding mode control based on the slip rate deviation and the yaw angular velocity deviation. ​

[0114] In a possible implementation, the selecting the sliding mode surface of the sliding mode control based on the slip ratio deviation and the yaw rate deviation comprises:

[0115] The sliding mode surface of the sliding mode is determined based on the following formula:

[0116]

[0117] wherein, Δλ = λ - λ * ; Δλ is the slip ratio deviation; λ is the slip ratio of the vehicle, U is the speed of the vehicle; U w is the wheel speed of the vehicle; λ * is the expected slip ratio;

[0118] wherein, is the yaw rate deviation; is the yaw rate of the vehicle; is the expected yaw rate; S is a switching function of the sliding mode surface.

[0119] In a possible implementation, the control function determining module 550 is configured to:

[0120] determine a dynamic equation of the sliding mode control based on the sliding mode surface;

[0121] determine a longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function, and an integral function of the longitudinal speed of the vehicle;

[0122] determine a control function of the sliding mode control based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model, and the current driving condition.

[0123] In a possible implementation, the control function determining module 550 further comprises a condition determining module configured to:

[0124] determine the current driving condition of the vehicle based on the longitudinal acceleration of the vehicle and a rate of change of the accelerator pedal opening degree when the vehicle is driving straight.

[0125] In a possible implementation, the determining the longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function, and the integral function of the longitudinal speed of the vehicle comprises:

[0126] the longitudinal acceleration of the vehicle is determined based on the following formula:

[0127]

[0128] wherein, is a dynamic equation of the sliding mode control; wherein, is a first derivative of the vehicle slip ratio; U is a speed of the vehicle; wherein, U = U x ; U w is a wheel speed of the vehicle; is a first derivative of the desired slip ratio; is a first derivative of the vehicle yaw rate; is a first derivative of the desired yaw rate;

[0129] wherein, the reaching law function is a constant reaching law function, is k > 0; k is a design parameter of the sliding mode control;

[0130] wherein, is an integral function of the vehicle longitudinal speed; wherein, U x is a longitudinal speed of the vehicle, U x0 is an initial longitudinal speed of the vehicle; a x is a longitudinal acceleration of the vehicle.

[0131] In a possible embodiment, the determining the control function of the sliding mode control based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model and the current driving condition comprises:

[0132] The control function of the sliding mode control is determined based on the following formula:

[0133]

[0134] wherein, F x1 , F x2 , F x3 and F x4 are driving forces of four wheels respectively; F y1 , F y2 , F y3 and F y4 are lateral forces of four wheels respectively; F f is a friction resistance, F w is an air resistance, F i is a slope resistance, F j is an acceleration resistance; a x is a longitudinal acceleration of the vehicle; m is a mass of the vehicle; a is a distance from a front axle to a center of mass, b is a distance from a rear axle to the center of mass, δ is a front wheel steering angle, d is a distance between left and right wheels; M zd is a yaw moment; I z is a moment of inertia; is a vehicle yaw rate;

[0135] wherein, F fWf; W=mg; wherein, m is the mass of the vehicle; g is the acceleration of gravity; f is the rolling friction coefficient;

[0136] In the case of the current driving condition being the uniform straight driving mode condition, F i = 0, F j = 0; In the case of the current driving condition being the extreme speed mode, F i = 0, wherein, C D is the automobile drag coefficient, A f is the automobile wind area; p a is the air density.

[0137] In the embodiment, the vehicle slip rate, the expected slip rate, the vehicle yaw rate and the expected yaw rate are selected to select the sliding mode surface of the sliding mode control, the sliding mode surface, the approaching law function and the two-degree-of-freedom model are used to determine the control function of the sliding mode control, and the vehicle is controlled based on the control function, so that the vehicle slip rate approaches the expected slip rate, the vehicle slip condition can be effectively avoided, the vehicle yaw rate approaches the expected yaw rate, the yaw condition can be effectively avoided, and thus the problem that the vehicle is prone to slip and unstable is effectively avoided, and the safety of the vehicle is improved.

[0138] As shown in Figure 6 , the embodiment of the application provides a structural schematic diagram of an electronic device, which comprises a processor 111, a communication interface 112, a memory 113 and a communication bus 114, wherein the processor 111, the communication interface 112 and the memory 113 complete mutual communication through the communication bus 114,

[0139] The memory 113 is used for storing a computer program.

[0140] In an embodiment of the application, the processor 111 is used for executing the program stored in the memory 113, and realizes the control method of the distributed straight driving provided by any one of the preceding method embodiments, which comprises the following steps:

[0141] determining the expected slip rate corresponding to the current driving condition of the vehicle;

[0142] establishing a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle;

[0143] selecting a sliding mode surface of the sliding mode control based on the vehicle slip rate, the expected slip rate, the vehicle yaw rate and the expected yaw rate;

[0144] determining an approaching law function of the sliding mode control;

[0145] A control function of the sliding mode control is determined based on the sliding surface, the approaching law function and the two-degree-of-freedom model, and the vehicle is controlled based on the control function.

[0146] The embodiment of the present application further provides a computer readable storage medium, which has a computer program stored thereon, and the computer program is executed by a processor to implement the steps of the control method of the distributed straight driving provided by any one of the foregoing method embodiments.

[0147] The apparatus embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Part or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0148] Through the description of the foregoing embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, and of course can also be implemented by hardware. Based on such understanding, the foregoing technical solutions can be embodied in the form of a software product, and the computer software product can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, and the like, and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0149] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "includes", "including" and the like are to be construed to be inclusive (i.e., to include both instances) unless otherwise indicated herein with certainty. The methods described herein can be implemented by one or more computer modules, and the method steps, processes, and operations described herein are not to be interpreted as necessarily requiring their performance in the particular order in which they are described, unless otherwise indicated. It is also to be understood that additional or alternative steps can be employed.

[0150] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A control method of distributed forward drive, characterized by, The method comprises: determining a desired slip ratio corresponding to a current driving condition of the vehicle; establishing a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle; selecting a sliding mode surface of the sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw angular velocity, and a desired yaw angular velocity; determining a reaching law function of the sliding mode control; determining a control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model, and controlling the vehicle based on the control function; wherein determining the control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model comprises: determining the control function of the sliding mode control based on a longitudinal acceleration of the vehicle, the two-degree-of-freedom model, and the current driving condition; wherein in the case of straight driving of the vehicle, the current driving condition of the vehicle is determined based on the longitudinal acceleration of the vehicle and a rate of change of a throttle pedal opening.

2. The method of claim 1, wherein, The selecting of the sliding mode surface of the sliding mode control based on the vehicle slip ratio, the desired slip ratio, the vehicle yaw angular velocity, and the desired yaw angular velocity comprises: determining a slip ratio deviation based on the vehicle slip ratio and the desired slip ratio; determining a yaw angular velocity deviation based on the vehicle yaw angular velocity and the desired yaw angular velocity; selecting the sliding mode surface of the sliding mode control based on the slip ratio deviation and the yaw angular velocity deviation.

3. The method of claim 2, wherein, The selecting of the sliding mode surface of the sliding mode control based on the slip ratio deviation and the yaw angular velocity deviation comprises: determining the sliding mode surface of the sliding mode control based on the following formula: wherein = 0.5 ; is the slip ratio deviation; = 0.5 ; is the vehicle slip ratio, is the vehicle speed; is the vehicle wheel speed; is the desired slip ratio; is a weighting factor, ; wherein = 0 ; is the yaw angle velocity deviation; is the vehicle yaw angle velocity; is the desired yaw angle velocity; is the switching function of the sliding mode surface.

4. The method of claim 1, wherein, The determining of the control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model further comprises: determining a dynamic equation of the sliding mode control based on the sliding mode surface; determining a longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function, and an integral function of a vehicle longitudinal velocity.

5. The method of claim 4, wherein, The determining of the longitudinal acceleration of the vehicle based on the dynamic equation of the sliding mode control, the reaching law function, and the integral function of the vehicle longitudinal velocity comprises: determining the longitudinal acceleration of the vehicle based on the following formula: wherein, is the dynamic equation of the sliding mode control; wherein, , is the first derivative of the vehicle slip ratio; is the speed of the vehicle, wherein, ; is the wheel speed of the vehicle; is the first derivative of the desired slip ratio; is the first derivative of the vehicle yaw rate; is the first derivative of the desired yaw rate; Wherein, the approaching law function is a constant speed approaching law function, and ; is a design parameter of the sliding mode control. wherein is an integral function of the longitudinal velocity of the vehicle; wherein is the longitudinal velocity of the vehicle, is the initial longitudinal velocity of the vehicle; is the longitudinal acceleration of the vehicle.

6. The method of claim 5, wherein, The determining of the control function of the sliding mode control based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model, and the current driving condition comprises: determining the control function of the sliding mode control based on the following formula: wherein, , , and are driving forces of the four wheels, respectively; , , and are lateral forces of the four wheels, respectively; is a frictional resistance, is an air resistance, is a slope resistance, is an acceleration resistance; is a longitudinal acceleration of the vehicle; is a mass of the vehicle; is a distance from the front axle to the center of mass, is a distance from the rear axle to the center of mass, is a front wheel steering angle, is a distance between the left and right wheels; is a yaw moment; is a moment of inertia; is a yaw angular velocity of the vehicle; is the control function; in, = ; ;in, For the quality of the vehicle; It is the acceleration due to gravity; The coefficient of rolling friction; In the case of the current driving condition being a uniform straight driving mode condition, , =0, = ; in the case of the current driving condition being an extreme speed mode, , , =0; wherein, is a car drag coefficient, is a car wind area; is air density.

7. A control device for distributed forward drive, characterized by The method comprises: an expected slip ratio determination module configured to determine a desired slip ratio corresponding to a current driving condition of the vehicle; a two-degree-of-freedom model establishment module configured to establish a two-degree-of-freedom model of the vehicle based on a longitudinal motion dimension and a yaw motion dimension of the vehicle; a sliding mode surface selection module configured to select a sliding mode surface of the sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw angular velocity, and a desired yaw angular velocity; a reaching law function determination module configured to determine a reaching law function of the sliding mode control; a control function determination module configured to determine a control function of the sliding mode control based on the sliding mode surface, the reaching law function, and the two-degree-of-freedom model, and control the vehicle based on the control function. The control function of the sliding mode control is determined based on the sliding surface, the approaching law function and the two-degree-of-freedom model, and comprises: The control function of the sliding mode control is determined based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model and the current driving condition; wherein, in the case of straight driving of the vehicle, the current driving condition of the vehicle is determined based on the longitudinal acceleration of the vehicle and the rate of change of the accelerator pedal opening.

8. An electronic device, comprising: The method comprises: a memory for storing a computer program; a processor for executing the computer program stored in the memory, and when the computer program is executed, the method of any one of claims 1-6 is implemented.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor, and the method of any one of claims 1-6 is implemented.

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