Distributed straight driving control method and device, equipment and storage medium

Abstract

The invention relates to a distributed straight driving control method, device and equipment and a storage medium, and the method comprises the steps that the expected slip rate corresponding to the current driving working condition of a vehicle is determined; establishing a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle; selecting a sliding mode surface of sliding mode control based on the vehicle slip rate, the expected slip rate, the vehicle yaw velocity and the expected yaw velocity; determining a reaching law function of sliding mode control; and determining a control function of 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. Therefore, the situation that the vehicle is unstable due to wheel slipping 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 in particular to a control method, device, equipment and storage medium for distributed straight-line driving. Background Art

[0002] Distributed drive has the advantage of being able to control four-wheel motors individually, and the discussion on it is gradually heating up. For distributed drive vehicles, traditional control methods have problems such as low control precision and low accuracy. Therefore, it is proposed to use sliding mode variable structure control to control distributed drive vehicles, which has achieved good results.

[0003] However, when distributed drive vehicles are driving straight, the wheels are still prone to slipping, causing the vehicle to become unstable, posing a safety hazard. Summary of the invention

[0004] The present application provides a distributed straight-line drive control method, which can effectively avoid vehicle instability caused by wheel slippage and improve vehicle safety.

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

[0006] Determine the expected slip ratio of the vehicle corresponding to the current driving condition;

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

[0008] selecting a sliding mode surface of sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw rate, and a desired yaw rate;

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

[0010] A control function of sliding mode control is determined based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and the vehicle is controlled based on the control function.

[0011] In a second aspect, the present application provides a distributed straight-line drive control device, comprising:

[0012] An expected slip ratio determination module, used to determine an expected slip ratio corresponding to the current driving condition of the vehicle;

[0013] A two-degree-of-freedom model building module, used to build a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle;

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

[0015] A reaching law function determination module, used for determining a reaching law function of sliding mode control;

[0016] A control function determination module is used to determine a control function of 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.

[0017] In a third aspect, an embodiment of the present application provides an electronic device, including:

[0018] Memory for storing computer programs;

[0019] The processor is used to execute the computer program stored in the memory, and when the computer program is executed, the method provided in the embodiment of the present application is implemented.

[0020] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method provided in the embodiment of the present application is implemented.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The technical solution provided in the embodiment of the present application selects the sliding surface of the sliding mode control through the vehicle slip rate, the expected slip rate, the vehicle yaw angular velocity and the expected yaw angular velocity, determines the control function of the sliding mode control through the sliding surface, the reaching law function and the two-degree-of-freedom model, and controls the vehicle based on the control function to make the vehicle slip rate approach the expected slip rate, which can effectively avoid the vehicle slipping, and can make the vehicle yaw angular velocity approach the expected angular velocity, which can effectively avoid the slipping caused by yaw, thereby effectively avoiding the problem of vehicle instability caused by easy slipping, thereby improving the safety of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

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

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

[0028] Figure 3 is a flow chart of selecting a sliding mode surface for sliding mode control based on a vehicle slip rate, a desired slip rate, a vehicle yaw rate, and a desired yaw rate, provided in an embodiment of the present application;

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

[0030] Figure 5 is a structural block diagram of a distributed straight-line drive control device provided in an embodiment of the present application;

[0031] Figure 6 It is a structural schematic diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0034] In order to solve the technical problem in the prior art that wheels of distributed drive vehicles are prone to slipping and causing vehicle instability during driving, the present application provides a distributed straight-line drive control method, device, equipment and storage medium, which can effectively avoid the situation where wheels are prone to slipping and causing vehicle instability, thereby improving the safety of the vehicle.

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

[0036] like Figure 1 As shown, the technical solution provided in the embodiment of the present application includes the following steps:

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

[0038] In this embodiment, the expected slip rate is used to define the standard for the wheels to basically not slip. The expected slip rate can be achieved by: obtaining a curve of the vehicle slip rate and the road adhesion coefficient through an equation established by the vehicle slip rate and the road adhesion coefficient, and calibrating and taking values ​​near the vertex of the curve to obtain the expected slip rate. The equation established by the slip rate and the road adhesion coefficient can adopt an existing equation in the prior art. For example, on a dry cement road, the equation established by the vehicle slip rate and the road adhesion coefficient can be u=1.197(1-e 23.168λ )-0.537λ; For example, on a dry asphalt road, the equation for the vehicle slip rate and the road adhesion coefficient can be u=1.28(1-e 23.99λ )-0.52λ. Where u is the road adhesion coefficient and λ is the vehicle slip rate.

[0039] Among them, when the distributed drive vehicle is moving straight, it can include two driving conditions, namely, a uniform speed straight driving mode condition and a high speed mode condition. Different expected slip rates can be used for different driving conditions, or the same expected slip rate can be used.

[0040] When different expected slip rates are used in different driving conditions, the expected slip rates of the four wheels for the uniform straight driving mode condition can be: The subscripts 1, 2, 3, and 4 represent the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, and the superscript * represents the expected value. For the extreme speed mode, the expected slip rate of the four wheels can be Wherein, ΔS is obtained by calibration, and specifically, the calibration can be performed on a curve of slip rate and road adhesion coefficient. When the wheel is on different road surfaces, ΔS may be different; wherein, ΔS may be between 0.01 and 0.05, and may be calibrated at intervals of 0.01.

[0041] When the same expected slip rate is used in different types of operating conditions, the expected slip rate may be the same as the expected slip rate in the uniform straight-line mode, or the same as the expected slip rate in the top-speed mode, or may be determined based on the expected slip rates in the two conditions (for example, based on an average of the two), or other reasonable expected slip rates may be used.

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

[0044] Among them, 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 kinematic equation of the vehicle; the above formula (2) is the yaw kinematic equation of the vehicle.

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

[0050] F f is the friction resistance, F w is the air resistance, F i is the ramp resistance, F j is the 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 turning angle, and 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 rate.

[0051] Step 103: Selecting a sliding mode surface of sliding mode control based on the vehicle slip rate, the desired slip rate, the vehicle yaw rate and the desired yaw rate.

[0052] In the embodiment of the present application, the slip ratio is the proportion of the sliding component in the wheel motion; the braking process of the vehicle from pure rolling to locking and sliding is a gradual process, which goes through three stages: pure rolling, rolling and sliding, and pure sliding. In order to evaluate the proportion of the wheel slip component, the slip ratio is often used to express it. 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 prevent the vehicle from slipping as much as possible, to prevent yaw motion and to maintain stability as much as possible, and to maintain the target driving torque of the vehicle, the sliding surface can be selected by the vehicle slip rate, the expected slip rate, the vehicle yaw angular velocity and the expected yaw angular velocity; wherein the sliding surface is a plane where S=0, and on the sliding surface, the system is in a stable state.

[0054] Specifically, in order to prevent the vehicle from slipping as much as possible and effectively avoid slipping caused by vehicle speed, the vehicle slip rate and expected slip rate are considered as factors for selecting the sliding surface. In order to prevent the vehicle from yaw motion and effectively avoid slipping caused by vehicle yaw motion, the vehicle yaw angular velocity and expected angular velocity are considered as factors for selecting the sliding surface. When the vehicle slip rate reaches the expected slip rate and 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 surface is selected by the vehicle slip rate, the expected slip rate, the vehicle yaw angular velocity and the expected yaw angular velocity.

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

[0056] In this embodiment, a constant speed convergence law function may be used, or an exponential convergence law function, a general convergence law function, etc. In order to reduce the disturbance of the system, a constant speed convergence function may be used, and subsequent operations may also be simplified.

[0057] Step 105: Determine a control function of 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.

[0058] In this embodiment, for the case of the vehicle moving straight, 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 surface and the reaching law function, and the longitudinal acceleration and the two-degree-of-freedom model are combined to obtain the control function of the sliding mode control, and the vehicle is controlled by the control function. Among them, the control function can be a control function of the longitudinal driving force, so that the vehicle can be controlled by the control function, so that the yaw angular velocity of the vehicle can be close to the expected angular velocity, and the slip rate of the vehicle can be close to the expected slip rate, so that the movement state of the vehicle reaches the expected target, and the situation that the vehicle is easy to slip and cause instability is avoided.

[0059] The technical solution provided in the embodiment of the present application selects the sliding surface of the sliding mode control through the vehicle slip rate, the expected slip rate, the vehicle yaw angular velocity and the expected yaw angular velocity, determines the control function of the sliding mode control through the sliding surface, the reaching law function and the two-degree-of-freedom model, and controls the vehicle based on the control function. The vehicle yaw angular velocity can be made close to the expected angular velocity, and the vehicle slip rate can be made close to the expected slip rate, so that the vehicle's motion state reaches the expected target, effectively avoiding the problem of vehicle instability caused by easy slipping, and improving the safety of the vehicle.

[0060] Figure 2 is a flow chart of a distributed straight driving control method provided in an embodiment of the present application, which defines the desired slip rate of the vehicle, such as Figure 2 As shown, the method comprises the following steps:

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

[0062] In this embodiment, the distributed drive has many highlight functions because the four motors can be driven independently. At the same time, the implementation logic of the basic functions is also different from that of traditional vehicles. The expected slip rates between different functions are different. If the unified target slip rate of traditional vehicles is adopted to control the distributed vehicle, many highlight functions will not be realized. Therefore, different expected slip rates can be determined for different functions.

[0063] In the case of a distributed drive vehicle driving straight, two highlight functions of driving conditions can be included, namely, a uniform speed straight driving mode condition and a maximum speed mode condition. Among them, it can be first determined whether the current driving condition is a uniform speed straight driving mode condition or a maximum speed mode condition. Among them, for the uniform speed straight driving mode condition, the acceleration value is less than an acceleration threshold, the acceleration threshold is small and close to 0, and the pedal opening change rate is less than a change rate threshold, the change rate threshold is close to 0. Under this condition, the wheels need to have sufficient friction with the road surface to provide driving force. The expected slip rate of the four wheels can be: Among them, the subscripts 1, 2, 3, and 4 represent the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, and the superscript * represents the expected value.

[0064] For extreme speed mode conditions, U<80m / s, that is, the acceleration is greater than 2m / s 2 , the pedal opening rate is greater than 15° / s, and the vehicle speed is less than 80m / s. This mode increases the longitudinal torque when the vehicle accelerates and starts, so that the vehicle can quickly reach the target speed. At this time, the vehicle slip probability increases and is easy to reach the critical value. The expected slip rate of the four wheels can be Wherein, ΔS is obtained through calibration, and ΔS may be different when the wheel is on different road surfaces; wherein, ΔS may be between 0.01 and 0.05, and may be calibrated at intervals of 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: Selecting a sliding mode surface of sliding mode control based on the vehicle slip rate, the desired slip rate, the vehicle yaw rate and the desired yaw rate.

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

[0068] The introduction of steps 202 - 204 may refer to the above embodiment.

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

[0070] In an optional embodiment, before S201, it may also include: when the vehicle is traveling straight, determining the current driving 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 the first acceleration threshold, and the rate of change of the accelerator pedal opening is less than the first rate of change threshold, it is judged to be a uniform speed straight driving mode condition; if the longitudinal acceleration of the vehicle is greater than the second acceleration threshold, and the rate of change of the accelerator pedal opening is greater than the second rate of change threshold and the speed is less than the speed threshold, it is judged to be a high speed mode condition. Among them, the first acceleration threshold may be a smaller value, for example, a value close to 0, and the first rate of change threshold may be a smaller value, for example, 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. Among them, the second acceleration threshold may be 2m / s 2 , the second change rate threshold may be 15° / s; the speed threshold may be 80m / s.

[0071] In the embodiment of the present application, if the current driving condition is a uniform straight driving mode, in the longitudinal kinematics equation in the two-degree-of-freedom model, the acceleration resistance F j is 0. Under this condition, the longitudinal acceleration of the vehicle is determined based on the sliding surface and the reaching law function, and the longitudinal acceleration of the vehicle is combined with the two-freedom model to obtain the control function of the sliding mode control.

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

[0073] In the related technology, with the development of distributed functions, the expected slip rates between different functions are different, and the car states are different. Therefore, the use of traditional open-loop control and proportional-integral-derivative (PID) control methods makes the car's control precision low, accuracy low, and adjustment ability weak. The sliding mode variable structure control has the advantages of easy control, strong robustness, fast response speed, and anti-interference. Compared with other conventional control strategies, its system structure is not fixed. Although the system jitter phenomenon may occur, the system jitter can be reduced by switching the control quantity according to the current state of the system and using a reasonable convergence law function. However, in the case of distributed straight-line driving, the vehicle is prone to slippage and instability, causing safety hazards.

[0074] The embodiment of the present application takes the current driving condition into consideration, and by corresponding different expected slip rates to different driving conditions, a sliding surface is selected according to the vehicle slip rate, expected slip rate, vehicle yaw speed and expected yaw angular velocity. The control function under different driving conditions is obtained through the sliding surface. The state of the vehicle can be made to reach the desired target, and the instability problem caused by vehicle skidding can be avoided. The vehicle can be controlled according to different driving conditions, so that the vehicle control is more in line with the actual situation and the control accuracy is improved.

[0075] Figure 3 is a flow chart of a sliding mode surface for selecting sliding mode control based on vehicle slip rate, expected slip rate, vehicle yaw rate and expected yaw rate provided by an embodiment of the present application. Figure 2 or Figure 1 Based on the process shown, Figure 3 As shown, the method comprises the following steps:

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

[0077] In the embodiment of the present application, the vehicle slip rate U is the speed of the vehicle; U w is the wheel speed of the vehicle. Different driving conditions correspond to different expected slip rates, and the slip rate deviation may be the difference between the vehicle slip rate and the expected slip rate.

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

[0079] In this embodiment, the yaw rate deviation may be the difference between the vehicle yaw rate and the desired yaw rate. The desired yaw rate may be determined based on parameters such as the driver's steering wheel angle and the accelerator pedal opening. Specifically, the desired yaw rate may be calculated with reference to the following formula: Among them, δ ′ is the steering wheel angle, L is the vehicle wheelbase, K is the vehicle stability coefficient, i is the wheel angle ratio, m is the vehicle mass, a and b are the distances from the center of mass to the front and rear axles respectively, and K f With K r are the stiffness of the front and rear axles respectively; u is the peak adhesion coefficient of the road surface; g is the acceleration of gravity. The expected angular velocity can be obtained through the above formula.

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

[0081] In an optional implementation, the selecting the sliding mode surface of the sliding mode control based on the slip rate deviation and the yaw rate deviation includes: performing a weighted combination of the slip rate deviation and the yaw rate deviation to obtain the sliding mode surface of the sliding mode control. Specifically, the slip rate deviation and the yaw rate deviation may be linearly weighted combined to obtain the sliding mode surface of the sliding mode control, or the slip rate deviation and the yaw rate deviation may be weighted combined in an exponential form, or the slip rate deviation and the yaw rate deviation may be weighted combined in an integral form, so as to meet the desired angular velocity and the desired slip rate, thereby stabilizing the system and reducing system jitter.

[0082] In an optional implementation manner, performing weighted combination of the slip rate 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 based on the following formula:

[0083]

[0084] Where Δλ=λ-λ * ; Δλ is the slip rate deviation; λ is the vehicle slip rate, U is the vehicle speed; U w is the wheel speed of the vehicle; where λ * is the expected slip ratio; is the yaw rate deviation; is the vehicle yaw angular velocity; is the desired yaw rate; S is the switching function of the sliding surface; ξ is the weight coefficient, 0<ξ<1. The sliding surface in the above formula (3) is established by linearly weighting the slip rate deviation and the yaw rate deviation. The sliding 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 surface through the slip rate deviation and the yaw angular velocity deviation to calculate the control function, the vehicle's motion state can reach the desired goal, the vehicle's slip rate control can be more stable, and the adaptability to the environment can be stronger. The sliding surface is obtained by performing a linear weighted combination of the slip rate deviation and the yaw angular velocity, which can simplify the calculation and improve the response speed.

[0086] Figure 4 is a flow chart of a control function for determining a sliding mode control based on a sliding surface, a reaching law function and a two-degree-of-freedom model provided by an embodiment of the present application. Figure 2 Based on the process shown, Figure 4 As shown, the method comprises the following steps:

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

[0088] In an optional implementation, determining the dynamic equation of the sliding mode control based on the sliding surface includes: obtaining the dynamic equation of the sliding mode control by taking a first-order derivative of the sliding surface. Specifically, when the state reaches the sliding surface, the sliding mode is entered, and the dynamic equation of the sliding mode control can be obtained by taking a first-order derivative of the sliding surface.

[0089] Step 402: Determine 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 velocity of the vehicle.

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

[0091] In an optional implementation, determining the 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 velocity of the vehicle includes: determining the longitudinal acceleration of the vehicle based on the following formula:

[0092]

[0093] Among them, the dynamic equation of sliding mode control is: in, is the first-order derivative of the vehicle slip rate; U is the speed of the vehicle, where U = U x ; U w is the wheel speed of the vehicle; is the first-order derivative of the expected slip rate; is the first-order derivative of the vehicle’s yaw rate; is the first-order derivative of the desired yaw rate;

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

[0095] The integral function of the vehicle longitudinal velocity is: Among them, U x is the longitudinal velocity of the vehicle, U x0 is the initial longitudinal velocity of the vehicle; a x is the longitudinal acceleration of the vehicle; the longitudinal acceleration of the vehicle can be obtained by the above formula (4).

[0096] Step 403: Determine a control function of 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 and the two-degree-of-freedom model are combined to obtain the control function of the sliding mode control. When the current driving condition is a uniform straight-line mode, the acceleration resistance in the two-degree-of-freedom model is 0; when the current driving condition is an extreme speed mode, the acceleration resistance in the two-degree-of-freedom model is not 0.

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

[0099]

[0100] Among them, F f =Wf; where W = mg; where 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] When the current driving condition is a straight-ahead driving condition at a constant speed, F i =0; F j =0; When the current driving condition is extreme speed mode, F i =0,

[0102] Among them, C D is the drag coefficient of the car, A f is the frontal area of ​​the car; ρ a is the air density.

[0103] Therefore, by calculating the longitudinal acceleration of the vehicle and determining the control function of the sliding mode control through the longitudinal acceleration of the vehicle 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 structural block diagram of a distributed straight driving control device provided in an embodiment of the present application, such as Figure 5 As shown, it includes: an expected slip ratio determination module 510, a two-degree-of-freedom model establishment module 520, a sliding surface selection module 530, a reaching law function determination module 540 and a control function determination module 550.

[0105] The expected slip ratio determination module 510 is used to determine the expected slip ratio corresponding to the current driving condition of the vehicle;

[0106] A two-degree-of-freedom model building module 520, for building a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle;

[0107] A sliding surface selection module 530, configured to select a sliding surface of sliding mode control based on the vehicle slip rate, the desired slip rate, the vehicle yaw rate and the desired yaw rate;

[0108] A reaching law function determination module 540, used to determine a reaching law function of sliding mode control;

[0109] The control function determination module 550 is used to 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, and control the vehicle based on the control function.

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

[0111] determining a slip ratio deviation based on the vehicle slip ratio and the desired slip ratio;

[0112] determining a yaw rate deviation based on the vehicle yaw rate and the desired yaw rate;

[0113] A sliding mode surface of the sliding mode control is selected based on the slip ratio deviation and the yaw rate deviation.

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

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

[0116]

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

[0118] in, is the yaw rate deviation; is the vehicle yaw angular velocity; is the desired yaw angular velocity; S is the switching function of the sliding surface.

[0119] In a possible embodiment, the control function determination module 550 is used to:

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

[0121] determining the 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 velocity of the vehicle;

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

[0123] In a possible embodiment, it further includes a working condition determination module, which is used to:

[0124] When the vehicle is traveling straight, 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.

[0125] In a possible embodiment, the determining the 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 velocity of the vehicle includes:

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

[0127]

[0128] in, is the dynamic equation of the sliding mode control; where, is the first-order derivative of the vehicle slip rate; U is the speed of the vehicle; where U = U x ; U w is the wheel speed of the vehicle; is the first-order derivative of the desired slip rate; is the first-order derivative of the vehicle yaw rate; is the first-order derivative of the desired yaw rate;

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

[0130] in, is the integral function of the longitudinal velocity of the vehicle; where U x is the longitudinal velocity of the vehicle, U x0 is the initial longitudinal velocity of the vehicle; a x is the longitudinal acceleration of the vehicle.

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

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

[0133]

[0134] Among them, F x1 、F x2 、F x3 and F x4 are the driving forces of the four wheels; F y1 、F y2 、F y3 and F y4 are the lateral forces of the four wheels; F f is the friction resistance, F w is the air resistance, F i is the ramp resistance, F j is the acceleration resistance; a x is 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 turning angle, and 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 rate;

[0135] Among them, F f=Wf; W = mg; where m is the mass of the vehicle; g is the acceleration of gravity; f is the rolling friction coefficient;

[0136] When the current driving condition is a straight-ahead driving condition at a constant speed, F i =0, F j =0; When the current driving condition is extreme speed mode, F i =0, Among them, C D is the drag coefficient of the car, A f is the frontal area of ​​the car; ρ a is the air density.

[0137] In this embodiment, the sliding surface of the sliding mode control is selected through the vehicle slip rate, the expected slip rate, the vehicle yaw angular velocity and the expected yaw angular velocity, the control function of the sliding mode control is determined through the sliding surface, the reaching law function and the two-degree-of-freedom model, and the vehicle is controlled based on the control function to make the vehicle slip rate approach the expected slip rate, which can effectively avoid the vehicle slipping, and can make the vehicle yaw angular velocity approach the expected angular velocity, which can effectively avoid the occurrence of yaw, thereby effectively avoiding the problem of vehicle slipping and causing instability, thereby improving the safety of the vehicle.

[0138] like Figure 6 As shown, an embodiment of the present application provides a structural schematic diagram of an electronic device, including 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 communicate with each other through the communication bus 114.

[0139] Memory 113, used for storing computer programs;

[0140] In one embodiment of the present application, the processor 111 is used to execute the program stored in the memory 113 to implement the distributed straight driving control method provided by any of the above method embodiments, including:

[0141] Determine the expected slip ratio of the vehicle corresponding to the current driving condition;

[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 sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw rate, and a desired yaw rate;

[0144] Determine the reaching law function of sliding mode control;

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

[0146] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the distributed straight-line drive control method provided in any of the aforementioned method embodiments are implemented.

[0147] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0148] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology 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 ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0149] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0150] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A distributed straight drive control method, characterized in that: include: Determine the expected slip ratio of the vehicle corresponding to the current driving condition; Establishing a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle; selecting a sliding mode surface of sliding mode control based on a vehicle slip ratio, the desired slip ratio, a vehicle yaw rate, and a desired yaw rate; Determine the reaching law function of sliding mode control; A control function of sliding mode control is determined based on the sliding mode surface, the reaching law function and the two-degree-of-freedom model, and the vehicle is controlled based on the control function.

2. The method according to claim 1, characterized in that The selecting a sliding mode surface of the sliding mode control based on the vehicle slip rate, the desired slip rate, the vehicle yaw rate and the desired yaw rate comprises: determining a slip ratio deviation based on the vehicle slip ratio and the desired slip ratio; determining a yaw rate deviation based on the vehicle yaw rate and the desired yaw rate; A sliding mode surface of the sliding mode control is selected based on the slip ratio deviation and the yaw rate deviation.

3. The method according to claim 2, characterized in that The selecting the sliding mode surface of the sliding mode control based on the slip rate deviation and the yaw rate deviation comprises: The sliding surface of the sliding mode is determined based on the following formula: Where Δλ=λ-λ * ; Δλ is the slip rate deviation; λ is the vehicle slip rate, U is the vehicle speed; U w is the wheel speed of the vehicle; * is the expected slip rate; ξ is the weight coefficient, 0<ξ<1; in, is the yaw angular velocity deviation; is the vehicle yaw angular velocity; is the desired yaw angular velocity; S is the switching function of the sliding surface.

4. The method according to claim 1, characterized in that: 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 comprises: Determining a dynamic equation of the sliding mode control based on the sliding mode surface; determining the 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 velocity of the vehicle; A control function of sliding mode control is determined based on the longitudinal acceleration of the vehicle, the two-degree-of-freedom model, and the current driving condition.

5. The method according to claim 4, characterized in that Also includes: When the vehicle is traveling straight, 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.

6. The method according to claim 4, characterized in that The determining of the 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 velocity of the vehicle comprises: The longitudinal acceleration of the vehicle is determined based on the following formula: in, is the dynamic equation of the sliding mode control; where, is the first-order derivative of the vehicle slip rate; U is the speed of the vehicle, where U = U x ; U w is the wheel speed of the vehicle; is the first-order derivative of the desired slip rate; is the first-order derivative of the vehicle yaw rate; is the first-order derivative of the desired yaw rate; Among them, the reaching law function is a constant speed reaching law function, which is k>0; k is the design parameter of sliding mode control; in, is the integral function of the longitudinal velocity of the vehicle; where U x is the longitudinal velocity of the vehicle, U x0 is the initial longitudinal velocity of the vehicle; a x is the longitudinal acceleration of the vehicle.

7. The method according to claim 6, characterized in that 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, including: The control function of sliding mode control is determined based on the following formula: Among them, F x1 、F x2 、F x3 and F x4 The driving force of the four wheels respectively; F y1 、F y2 、F y3 and F y4 are the lateral forces of the four wheels; F f is the frictional resistance, F w is the air resistance, F i is the ramp resistance, F j is the acceleration resistance; a x is 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 turning angle, and 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 rate; F x is the control function; Among them, F f =Wf; W = mg; where m is the mass of the vehicle; g is the acceleration of gravity; f is the rolling friction coefficient; When the current driving condition is a straight-ahead driving condition at a constant speed, F j =0, F i =0, When the current driving condition is extreme speed mode, F i =0; where C D is the drag coefficient of the car, A f is the frontal area of ​​the car; ρ a is the air density.

8. A distributed straight drive control device, characterized in that: include: An expected slip ratio determination module, used to determine an expected slip ratio corresponding to the current driving condition of the vehicle; A two-degree-of-freedom model building module, used to build a two-degree-of-freedom model of the vehicle based on the longitudinal motion dimension and the yaw motion dimension of the vehicle; A sliding surface selection module, configured to select a sliding surface of sliding mode control based on a vehicle slip rate, the desired slip rate, a vehicle yaw rate, and the desired yaw rate; A reaching law function determination module, used for determining a reaching law function of sliding mode control; A control function determination module is used to determine a control function of 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.

9. An electronic device, characterized in that: include: Memory for storing computer programs; A processor, configured to execute a computer program stored in the memory, and when the computer program is executed, implement the method described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method described in any one of claims 1 to 7 is implemented.

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