An adaptive lateral-longitudinal coupling vehicle dynamics model construction method

Abstract

The present application relates to a kind of self-adapting lateral-longitudinal coupling vehicle dynamics model construction method, including constructing tire dynamics model and constructing vehicle dynamics model based on tire dynamics model, self-adapting lateral-longitudinal coupling vehicle dynamics model is constructed in combination with tire dynamics model and vehicle dynamics model;The tire dynamics model of the construction includes step one: constructing linear saturated tire model;The vehicle dynamics model of the construction includes step one: when the front wheel angle of vehicle is small, construct small front wheel angle three-degree-of-freedom vehicle dynamics model;Step two: when the front wheel angle of vehicle is large, construct large front wheel angle three-degree-of-freedom vehicle dynamics model;Self-adapting lateral-longitudinal coupling vehicle dynamics model.By considering the influence of front wheel angle on vehicle dynamics coupling characteristics, self-adapting lateral-longitudinal coupling vehicle dynamics model is constructed, linear saturated tire model is combined, and accurate, complete vehicle dynamics model under different driving conditions is constructed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle dynamics model, in particular to a kind of self-adapting lateral and longitudinal coupling vehicle dynamics model construction method. BACKGROUND

[0002] Vehicle model can be used to analyze the dynamics characteristics of vehicle in different driving states, and construct the mapping relationship between vehicle input and key state. On the one hand, it can be applied to model-based control algorithm, such as MPC, LQR, etc., to design trajectory tracking, obstacle avoidance control, stability coordination and other algorithm development. On the other hand, it can also be used as a simplified model of the vehicle under test to assist in rapid iteration and optimization of the algorithm.

[0003] Under different driving conditions, the vehicle dynamics characteristics show different lateral and longitudinal coupling characteristics and nonlinear characteristics. Therefore, constructing an accurate vehicle dynamics model is the premise and basis for studying vehicle dynamics characteristics, stability control and obstacle avoidance algorithm development.

[0004] Current main vehicle models, such as three-degree-of-freedom single-track vehicle dynamics model and seven-degree-of-freedom vehicle dynamics model, often assume that the vehicle is in a linear range, the front wheel angle of the vehicle is small, and a linear tire model is used. Although this reduces the complexity of the model to some extent, the overly simplified modeling assumptions result in a narrow range of vehicle operating conditions and an inability to accurately describe changes in vehicle state. While complex vehicle models can describe vehicle nonlinear characteristics and consider the influence of multiple actuators such as drive-by-wire, they have poor real-time performance and are difficult to apply in practice. Therefore, current vehicle models always face the problem of balancing model fidelity and real-time performance. Existing vehicle dynamics models do not fully consider the operating characteristics of the vehicle under different driving conditions, resulting in insufficient simulation accuracy or excessive simulation time.

[0005] Therefore, the present application provides a self-adapting lateral and longitudinal coupling vehicle dynamics model construction method, which can obtain accurate vehicle dynamics simulation results under any operating condition with a small running time cost. SUMMARY

[0006] To solve the above technical problems, the present application provides a self-adapting lateral and longitudinal coupling vehicle dynamics model construction method, which constructs a tire dynamics model and a vehicle body dynamics model based on the tire dynamics model, and constructs a self-adapting lateral and longitudinal coupling vehicle dynamics model by combining the tire dynamics model and the vehicle body dynamics model.

[0007] The tire dynamics model construction includes the following steps: Step 1: Construct a linear saturated tire model F y = min{K x a, F ypeak}, where K, a, F ypeakare respectively the approximate fitting results of tire cornering stiffness, tire cornering angle and tire lateral force saturation value, and the F y comprises F yfl , F yfr , F yrl , F yrr , F yfl , F yfr , F yrl , F yrr are respectively the left front wheel lateral force, the right front wheel lateral force, the left rear wheel lateral force and the right rear wheel lateral force;

[0008] The constructing vehicle body dynamics model comprises the following steps: step one: taking ξ=[v x ,v y ,Ψ,w,X,Y] as state variables, taking u=[δ f ,F xfl ,F xfr ,F xrl ,F xrr ] as control variables, based on a linear saturated tire model, simplifying the lateral-longitudinal coupling characteristics when the front wheel steering angle of the vehicle is small, and constructing a small front wheel steering angle three-degree-of-freedom vehicle body dynamics model f dyn1 (ξ,u), wherein v x is a longitudinal velocity, v y is a lateral velocity, ψ is a vehicle yaw angle, w is a yaw angular velocity, X is a vehicle longitudinal displacement in an inertial coordinate system, Y is a vehicle lateral displacement in the inertial coordinate system, δ f is a front wheel steering angle, and F xfl ,F xfr ,F xrl ,F xrr are respectively a left front wheel longitudinal force, a right front wheel longitudinal force, a left rear wheel longitudinal force and a right rear wheel longitudinal force;

[0009] Step two: taking ξ=[v x ,v y ,Ψ,w,X,Y] as state variables, taking u=[δ f ,F xfl ,F xfr ,F xrl ,F xrr ] as control variables, based on a linear saturated tire model, considering the lateral-longitudinal coupling characteristics when the front wheel steering angle of the vehicle is large, and constructing a large front wheel steering angle three-degree-of-freedom vehicle body dynamics model f dyn2 (ξ,u);

[0010] The constructing adaptive lateral-longitudinal coupling vehicle dynamics model comprises the following steps: step one: constructing a front wheel steering angle adjustment factor according to the vehicle dynamics characteristics when the front wheel steering angle is small and the vehicle dynamics characteristics when the front wheel steering angle is large;

[0011] Step two: the adaptive lateral and longitudinal coupling vehicle dynamics model f is constructed by linearly weighting combination of the small front wheel steering angle three degree of freedom vehicle dynamics model and the large front wheel steering angle three degree of freedom vehicle dynamics model dyn (ξ, u); the f dyn (ξ, u) = λ1 x f dyn2 (ξ, u) + (1-λ1) x f dyn1 (ξ, u).

[0012] Compared with the prior art, the present application has the following beneficial effects: by considering the influence of the front wheel steering angle on the vehicle dynamics coupling characteristics, an adaptive lateral and longitudinal coupling vehicle dynamics model is constructed, and by combining a linear saturated tire model, an accurate and complete vehicle dynamics model under different driving conditions is constructed, which can be applied to vehicle dynamics characteristic analysis, model-based control algorithm development and auxiliary algorithm rapid verification, etc.

[0013] According to the change of the vehicle lateral and longitudinal coupling characteristics under the small front wheel steering angle and the large front wheel steering angle, the adaptive lateral and longitudinal coupling vehicle dynamics model is constructed by realizing the linear weighting combination of the small front wheel steering angle three degree of freedom vehicle dynamics model and the large front wheel steering angle three degree of freedom vehicle dynamics model through the front wheel steering angle adjustment factor, which can realize the smooth transition of the vehicle model under different conditions, accurately track in any steering angle range, provide more accurate vehicle state prediction values under a wider range of driving conditions, obtain accurate vehicle dynamics characteristic simulation results under any condition with small running time cost, and further simplify the tire model, improve the operation real-time performance of the model in the actual prediction process.

[0014] Further, the small front wheel steering angle three degree of freedom vehicle dynamics model f dyn1 (ξ, u) is

[0015]

[0016] The beneficial effects of the above step are that the vehicle body dynamics model can effectively fit the changes of the vehicle state quantities such as the vehicle longitudinal speed, lateral speed, yaw angle, yaw angular velocity, longitudinal displacement and lateral displacement under the corresponding front wheel steering angle, left front wheel longitudinal force, right front wheel longitudinal force, left rear wheel longitudinal force and right rear wheel longitudinal force inputs.

[0017] Further, the large front wheel steering angle three degree of freedom vehicle dynamics model f dyn2 (ξ, u) is

[0018]

[0019] The beneficial effect of the above step is that when the large front wheel steering angle acts, the mapping relationship between the control input quantities such as the front wheel steering angle and the four wheel longitudinal forces and the vehicle state quantity changes such as the longitudinal velocity, the lateral velocity, the yaw angle, the yaw angular velocity, the longitudinal displacement and the lateral displacement is fitted by further considering the lateral-longitudinal coupling effect, so that the vehicle state quantity change prediction can be realized.

[0020] Further, the front wheel steering angle adjustment factor λ1 is formulaed as:

[0021]

[0022] The δ flim1 and the δ flim2 are the front wheel steering angle transition thresholds, according to the cosine function and the sine function change rate difference, the δ flim1 takes the value of 0.05 rad, and the δ flim2 takes the value of 0.32 rad.

[0023] The beneficial effect of the above step is that with the change of the front wheel steering angle, the vehicle dynamics model is smoothly transitioned, when the current front wheel steering angle is less than the δ flim1 , λ1 is equal to 0, the small front wheel steering angle three-degree-of-freedom vehicle body dynamics model is adopted, that is, f dyn (ξ, u) = f dyn1 (ξ, u); when the current front wheel steering angle is greater than the δ flim2 , λ1 is equal to 1, the large front wheel steering angle three-degree-of-freedom vehicle body dynamics model is adopted, that is, f dyn (ξ, u) = f dyn2 (ξ, u); when the current front wheel steering angle is between the δ flim1 and the δ flim2 , λ1 takes the value in the interval [0, 1], and the vehicle dynamics model is composed of the small front wheel steering angle three-degree-of-freedom vehicle body dynamics model and the large front wheel steering angle three-degree-of-freedom vehicle body dynamics model, that is, f dyn (ξ, u) = λ1 × f dyn2 (ξ, u) + (1-λ1) × f dyn1 (ξ, u)

[0024] Further, the linear saturated tire model F y = min{K × α, F ypeak}

[0025]

[0026] The μ0, F z0 , K0, F ypeak0 are respectively the road adhesion coefficient, the vertical load, the cornering stiffness and the lateral force peak value corresponding to the reference value, and the μ, F z , F xrespectively, are the actual road adhesion coefficient, the actual vertical load, the actual input longitudinal force, the C1, C2 are the approximate fitting coefficients, the K, F ypeak respectively, are the approximate fitting results of the tire cornering stiffness and the tire lateral force saturation value, and the a is the tire cornering angle.

[0027] The beneficial effect of the above step is that the tire cornering characteristics under different road adhesion conditions and vertical load changes can be effectively described, the tire linear characteristics and saturation characteristics are considered, the mapping relationship between the tire cornering angle and the tire lateral force is simplified, and the model operation real-time performance is improved under the premise of ensuring the accuracy of the tire model.

[0028] Further, the vertical load includes F zfl , F zfr , F zrl , F zrr , F zfl , F zfr , F zrl , F zrr respectively, are the left front wheel vertical load, the right front wheel vertical load, the left rear wheel vertical load, and the right rear wheel vertical load.

[0029] Further, the four wheel vertical load formulas are:

[0030]

[0031] The L is the wheelbase, h is the center of mass height, a x is the longitudinal acceleration, and a y is the lateral acceleration.

[0032] The beneficial effect of the above step is that the four vehicle vertical load changes can be effectively calculated based on the acceleration information input, and the accuracy of the tire lateral force estimation is improved.

[0033] Further, the tire cornering angle includes a yfl , a yfr , a yrl , a yrr , a yfl , a yfr , a yrl , a yrr respectively, are the left front wheel cornering angle, the right front wheel cornering angle, the left rear wheel cornering angle, and the right rear wheel cornering angle.

[0034] Further, the four vehicle tire cornering angle formulas are:

[0035]

[0036] The beneficial effects of the previous step are: the double-track vehicle dynamics model is adopted, and the tire side slip angles corresponding to the four wheels are calculated respectively, which helps to improve the accuracy of the four-wheel lateral force prediction. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The flowchart of the vehicle dynamics model and the tire dynamics model;

[0038] Figure 2 The fitting effect diagram of the linear saturated tire model - tire lateral fitting effect under different vertical loads;

[0039] Figure 3 The fitting effect diagram of the linear saturated tire model - tire lateral fitting effect under different road adhesion coefficients;

[0040] Figure 4 The model fidelity evaluation under the sinusoidal steering test - comparison chart of yaw rate of different vehicle models under simulation condition 1;

[0041] Figure 5 The model fidelity evaluation under the sinusoidal steering test - comparison chart of yaw rate of different vehicle models under simulation condition 2;

[0042] Figure 6 The model fidelity evaluation under the sinusoidal steering test - comparison chart of yaw rate of different vehicle models under simulation condition 3;

[0043] Figure 7 The model fidelity evaluation under the sinusoidal steering test - comparison chart of yaw rate of different vehicle models under simulation condition 4;

[0044] Figure 8 The model fidelity evaluation under the sinusoidal steering test - comparison chart of maximum yaw rate deviation index of different vehicle models under different conditions;

[0045] Figure 9 The model fidelity evaluation under the sinusoidal steering test - comparison chart of average yaw rate deviation index of different vehicle models under different conditions;

[0046] Figure 10 The model fidelity evaluation under the double lane change test - expected obstacle avoidance trajectory diagram;

[0047] Figure 11 The model fidelity evaluation under the double lane change test - comparison chart of yaw rate of different vehicle models under simulation condition 1;

[0048] Figure 12 The model fidelity evaluation under the double lane change test - comparison chart of yaw rate of different vehicle models under simulation condition 2;

[0049] Figure 13 For model fidelity evaluation under double lane change test - comparison chart of maximum yaw rate deviation index of different vehicle models under different working conditions;

[0050] Figure 14 For model fidelity evaluation under double lane change test - comparison chart of average yaw rate deviation index of different vehicle models under different working conditions. DETAILED DESCRIPTION

[0051] In order to better understand the technical solutions of the present application, the present application will be further described below in conjunction with specific embodiments and the accompanying drawings.

[0052] Example 1:

[0053] Please refer to Figures 1-14 , according to the present embodiment provides a kind of adaptive lateral and longitudinal coupling vehicle dynamics model construction method, constructs tire dynamics model and constructs vehicle dynamics model based on tire dynamics model, tire dynamics model and vehicle dynamics model are combined to construct adaptive lateral and longitudinal coupling vehicle dynamics model;The tire dynamics model of the described construction includes step one: constructing linear saturated tire model F y = min{K × α, F ypeak}, the K, α, F ypeak Approximate fitting result of tire cornering stiffness, tire side slip angle and tire lateral force saturation value respectively, F y Including F yfl , F yfr , F yrl , F yrr , F yfl , F yfr , F yrl , F yrr Respectively left front wheel lateral force, right front wheel lateral force, left rear wheel lateral force, right rear wheel lateral force;The vehicle dynamics model of the described construction includes step one: with ξ = [v x , v y , ψ, w, X, Y] as state variable, with u = [δ f , F xfl , F xfr , F xrl , F xrr ] as control variable, based on linear saturated tire model, when vehicle front wheel steering angle is small, simplify lateral and longitudinal coupling characteristics, construct small front wheel steering angle three degrees of freedom vehicle dynamics model f dyn1 (ξ, u), the v x For longitudinal velocity, v y For lateral velocity, ψ is vehicle yaw angle, w is yaw rate, X is vehicle longitudinal displacement in inertial coordinate system, Y is vehicle lateral displacement in inertial coordinate system, the δf for front wheel angle, the F xfl for front wheel angle, the F xfr for front wheel angle, the F xrl for front wheel angle, the F xrr respectively, left front wheel longitudinal force, right front wheel longitudinal force, left rear wheel longitudinal force, right rear wheel longitudinal force; step two: taking ξ = [v x , v y , Ψ, w, X, Y] as state variables, taking u = [δ f , F xfl , F xfr , F xrl , F xrr ] as control variables, based on a linear saturated tire model, considering the lateral-longitudinal coupling characteristics when the large front wheel angle is large, a large front wheel angle three-degree-of-freedom vehicle body dynamics model f dyn2 (ξ, u) is constructed; step three: according to the vehicle dynamics characteristics when the small front wheel angle and the vehicle dynamics characteristics when the large front wheel angle, a front wheel angle adjustment factor is constructed, and an adaptive lateral-longitudinal coupling vehicle dynamics model f dyn (ξ, u) is constructed by linearly weighting combination of the small front wheel angle vehicle body dynamics model and the large front wheel angle vehicle body dynamics model; the front wheel angle adjustment factor is λ1.

[0054] f dyn (ξ, u) = λ1*f dyn2 (ξ, u) + (1-λ1)*f dyn1 (ξ, u), and the λ1 is a front wheel angle adjustment factor. By considering the influence of the front wheel angle on the vehicle dynamics coupling characteristics, an adaptive lateral-longitudinal coupling vehicle body dynamics model is constructed, and an accurate and complete vehicle dynamics model under different driving conditions is constructed by combining a linear saturated tire model, which can be applied to vehicle dynamics characteristic analysis, model-based control algorithm development, and rapid verification of auxiliary algorithms; according to the change of the vehicle lateral-longitudinal coupling characteristics under the small front wheel angle and the large front wheel angle, the adaptive lateral-longitudinal coupling vehicle dynamics model is constructed by linearly weighting combination of the small front wheel angle vehicle body dynamics model and the large front wheel angle vehicle body dynamics model through the front wheel angle adjustment factor, which can realize smooth transition of the vehicle model under different conditions and accurate tracking in any angle range, and can provide more accurate vehicle state prediction values under a wider range of driving conditions, so as to obtain accurate vehicle dynamics characteristic simulation results under any conditions with small running time cost; by constructing a linear saturated tire model, the complexity of the vehicle dynamics model is reduced under the premise of accurately fitting the nonlinear saturation characteristics of the tire under different loads and different adhesion conditions, the tire model is further simplified, and the operation real-time performance of the model in the actual prediction process is improved.

[0055] Based on the current actual state quantity and control variable input, combined with the linear saturated tire model, the lateral force corresponding to the four wheels can be effectively estimated, and the fitting effect is as shown in Figure 2 and Figure 3 Further substituted into the vehicle dynamics model, auxiliary determination of vehicle state quantity change;

[0056] To verify the fidelity of the adaptive longitudinal and lateral coupling vehicle dynamics model (ACDD) model proposed in this patent, the Carsim and Simulink joint simulation platform (Carsim) is selected as the comparison benchmark, and the kinematics model (KIM), the longitudinal and lateral decoupling single-track three-degree-of-freedom vehicle dynamics model (Decouple), and the longitudinal and lateral coupling double-track seven-degree-of-freedom vehicle dynamics model (7DOF) are selected as the control group.

[0057] The comparison evaluation index is the yaw rate response under different working conditions, as well as the maximum yaw rate deviation and the average yaw rate deviation.

[0058] The comparison test mainly includes sinusoidal steering test and double lane change test, wherein the sinusoidal test mainly includes four groups of test conditions such as vehicle speed 121km / h, steering wheel steering amplitude 15deg (condition 1), vehicle speed 65km / h, steering wheel steering amplitude 60deg (condition 2), vehicle speed 18km / h, steering wheel steering amplitude 300deg (condition 3), and vehicle speed 8km / h, steering wheel steering amplitude 540deg (condition 4), and the road adhesion coefficient is 0.85; The double lane change test includes two groups of test conditions such as vehicle speed 100km / h (condition 1) and vehicle speed 60km / h (condition 2), and the road adhesion coefficient is 0.5.

[0059] Figures 4-7 and Figures 11-12 The yaw rate response under different test conditions is shown in FIGS. 1-4, wherein the adaptive longitudinal and lateral coupling vehicle dynamics model proposed in this patent can accurately fit the yaw rate change under different working conditions, and is close to the benchmark value.

[0060] Figures 8-9 and Figures 13-14 The maximum yaw rate deviation and the average yaw rate deviation under different test conditions are shown in FIGS. 5-8, wherein the maximum yaw rate deviation and the average yaw rate deviation of the adaptive longitudinal and lateral coupling vehicle dynamics model proposed in this patent are generally lower than those of the control group under different working conditions, proving the fitting accuracy of the adaptive longitudinal and lateral coupling vehicle dynamics model;

[0061] Figure 10 The vehicle driving trajectory under double lane change test is shown in FIG. 9, wherein the double lane change test can effectively stimulate the vehicle stability control system under low adhesion conditions, so as to determine the yaw rate response of the vehicle under stability control;

[0062] The small front wheel steering angle three-degree-of-freedom vehicle body dynamics model f dyn1 (ξ, u) is

[0063]

[0064] The vehicle body dynamics model can effectively fit the changes of vehicle state quantities such as longitudinal velocity, lateral velocity, yaw angle, yaw angular velocity, longitudinal displacement, lateral displacement under corresponding front wheel steering angle, left front wheel longitudinal force, right front wheel longitudinal force, left rear wheel longitudinal force, right rear wheel longitudinal force input.

[0065] The large front wheel steering angle three-degree-of-freedom vehicle body dynamics model f dyn2 (ξ, u) is

[0066]

[0067] When the large front wheel steering angle acts, the mapping relationship between the changes of vehicle state quantities such as longitudinal velocity, lateral velocity, yaw angle, yaw angular velocity, longitudinal displacement, lateral displacement and control input quantities such as front wheel steering angle and four wheel longitudinal forces is fitted by further considering the lateral-longitudinal coupling effect, so that the vehicle state quantity change prediction can be realized.

[0068] The front wheel steering angle adjustment factor λ1 formula is: The δ flim1 and the δ flim2 are front wheel steering angle transition thresholds, according to the difference in change rate of cosine function and sine function, the δ flim1 takes a value of 0.05 rad, and the δ flim2 takes a value of 0.32 rad. With the change of the front wheel steering angle, the smooth transition of the vehicle dynamics model is realized, when the front wheel steering angle is less than the δ flim1 , λ1 is equal to 0, the small front wheel steering angle three-degree-of-freedom vehicle body dynamics model, that is, f dyn (ξ, u) = f dyn1 (ξ, u) is adopted; when the front wheel steering angle value is greater than the δ flim2 , λ1 is equal to 1, the large front wheel steering angle three-degree-of-freedom vehicle body dynamics model, that is, f dyn (ξ, u) = f dyn2 (ξ, u) is adopted; when the front wheel steering angle is between the δ flim1 and the δ flim2 , λ1 takes a value in the interval [0, 1], and the vehicle dynamics model is composed of the small front wheel steering angle three-degree-of-freedom vehicle body dynamics model and the large front wheel steering angle three-degree-of-freedom vehicle body dynamics model, that is, f dyn (ξ, u) = λ1 × f dyn2 (ξ, u) + (1-λ1) × f dyn1 (ξ, u)

[0069] The linear saturated tire model Fy = min{K x a, F ypeak}

[0070]

[0071] The μ0,F z0 , K0,F ypeak0 are the road adhesion coefficient, the vertical load, the cornering stiffness, and the peak lateral force corresponding reference value respectively, and the μ,F z , F x are the actual road adhesion coefficient, the actual vertical load, and the actual input longitudinal force respectively, and the C1,C2 are the approximate fitting coefficients, and the K,F ypeak are the approximate fitting results of the tire cornering stiffness and the tire lateral force saturation value respectively, and the a is the tire cornering angle. The tire cornering characteristics under different road adhesion conditions and vertical load changes can be effectively described, the linear characteristics and saturation characteristics of the tire are considered, the mapping relationship between the tire cornering angle and the tire lateral force is simplified, the model operation real-time performance is improved under the premise of ensuring the accuracy of the tire model.

[0072] The vertical loads include F zfl , F zfr , F zrl , F zrr , and the F zfl , F zfr , F zrl , F zrr are the left front wheel vertical load, the right front wheel vertical load, the left rear wheel vertical load, and the right rear wheel vertical load respectively.

[0073] The four wheel vertical load formulas are:

[0074]

[0075] The L is the wheelbase, the h is the center of mass height, the a x is the longitudinal acceleration, and the a y is the lateral acceleration. The four vehicle vertical load changes can be effectively calculated based on the acceleration information input, and the accuracy of the tire lateral force estimation is improved.

[0076] The tire cornering angles include a yfl , a yfr , a yrl , a yrr , and the a yfl , a yfr , a yrl , a yrr are the left front wheel cornering angle, the right front wheel cornering angle, the left rear wheel cornering angle, and the right rear wheel cornering angle respectively.

[0077] The four vehicle tire side slip angle formulas are:

[0078]

[0079] Adopting a double-track vehicle dynamics model, the tire side slip angles corresponding to the four wheels are calculated, which is helpful to improve the prediction accuracy of the four-wheel lateral force.

[0080] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; based on the examples of the present application, all other examples obtained by those skilled in the art without creative work belong to the protection scope of the present application. Although the present application is described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the examples of the present application.

Claims

1. A self-adaptive lateral and longitudinal coupled vehicle dynamics model construction method, characterized in that, The method comprises the following steps: constructing a tire dynamics model, constructing a vehicle body dynamics model based on the tire dynamics model, and constructing an adaptive lateral-longitudinal coupling vehicle dynamics model by combining the tire dynamics model and the vehicle body dynamics model. The constructing tire dynamics model comprises a step one: constructing a linear saturated tire model , the Approximate fitting results of tire cornering stiffness, tire cornering angle and tire lateral force saturation value respectively, the Comprise , the Left front wheel lateral force, right front wheel lateral force, left rear wheel lateral force, right rear wheel lateral force respectively The constructing vehicle body dynamics model comprises the following steps: Taking as state variables and taking as control variables, a small front wheel steering angle three-degree-of-freedom vehicle body dynamics model is constructed based on a linear saturated tire model, and the lateral-longitudinal coupling characteristics are simplified when the front wheel steering angle of the vehicle is small is a longitudinal velocity, is a lateral velocity, is a vehicle yaw angle, is a yaw angular velocity, is a vehicle longitudinal displacement in an inertial coordinate system, is a vehicle lateral displacement in the inertial coordinate system, is a front wheel steering angle, and are respectively a left front wheel longitudinal force, a right front wheel longitudinal force, a left rear wheel longitudinal force and a right rear wheel longitudinal force; Step two: take as state variable, take as control variable, based on linear saturation tire model, considering the lateral and longitudinal coupling characteristics, build a three-degree-of-freedom vehicle body dynamics model with large front wheel steering angle ; The constructing the adaptive lateral-longitudinal coupling vehicle dynamics model comprises the following steps: step one, constructing a front wheel steering angle adjustment factor according to vehicle dynamics characteristics when the front wheel steering angle is small and vehicle dynamics characteristics when the front wheel steering angle is large ; Step three: constructing the adaptive lateral-longitudinal coupling vehicle dynamics model by linearly weighting combining the small front wheel steering angle three-degree-of-freedom vehicle body dynamics model and the large front wheel steering angle three-degree-of-freedom vehicle body dynamics model ; the ; The small front wheel steering angle three-degree-of-freedom vehicle body dynamics model For The , are the longitudinal distances from the center of mass to the front and rear axles, respectively, the is the moment of inertia of the vehicle about the z-axis, the is the wheel track, the is the longitudinal resistance, which includes rolling resistance, air resistance, the is the total vehicle mass, and the is the front wheel steering angle. The large front wheel turning angle three-degree-of-freedom vehicle body dynamics model For 。 2. The self-adaptive lateral and longitudinal coupled vehicle dynamics model construction method according to claim 1, characterized in that, The front wheel steering angle adjusting factor The formula is: The And is a front wheel steering angle transition threshold value, according to the cosine function and the difference in the rate of change of the sine function, the The value is 0.05 rad, and the The value is 0.32 rad.

3. The method of claim 1, wherein The linear saturated tire model The are respectively a road adhesion coefficient, a vertical load, a cornering stiffness, a lateral force peak value corresponding reference value, the are respectively an actual road adhesion coefficient, an actual vertical load, an actual input longitudinal force, the is an approximate fitting coefficient, the are respectively a tire cornering stiffness and a tire lateral force saturation value approximate fitting result, is a tire cornering angle.

4. The self-adaptive lateral and longitudinal coupled vehicle dynamics model construction method of claim 3, wherein, The vertical load includes , the respectively left front wheel vertical load, right front wheel vertical load, left rear wheel vertical load, right rear wheel vertical load.

5. The self-adaptive lateral and longitudinal coupled vehicle dynamics model construction method of claim 4, wherein, The four-wheel vertical load calculation formula is: The is the wheelbase, is the height of the center of mass, is the longitudinal acceleration, is the lateral acceleration.

6. The self-adaptive lateral and longitudinal coupled vehicle dynamics model construction method of claim 3, wherein, The tire side slip angle includes , the are left front wheel side slip angle, right front wheel side slip angle, left rear wheel side slip angle, right rear wheel side slip angle, respectively.

7. The method according to claim 6, wherein The four-wheel tire side slip angle calculation formula is: 。

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