Vehicle stability quantitative evaluation method based on three-dimensional phase space

Abstract

The invention belongs to the technical field of autonomous vehicles, and particularly relates to a vehicle stability quantitative evaluation method based on a three-dimensional phase space. The method comprises the following steps: firstly, establishing a lateral vehicle speed-yaw velocity-roll angle three-dimensional phase space according to a vehicle dynamics model; secondly, designing a lateral and roll stability boundary state point screening method, forming an envelope stability region by applying a three-dimensional convex hull, and mapping lateral and roll stability limiting conditions into a comprehensive stability region in a phase space; thirdly, according to the minimum distance between the state point and the determined stable area and the relative positions of the state point and the determined stable area, a geometric distance quantization function is designed to obtain a stability index, and the stability state of the vehicle can be quantitatively evaluated. According to the method, a standardized stability quantitative evaluation index can be established according to different driving states of the vehicle, accurate and comprehensive analysis of complex vehicle dynamics performance is facilitated, and reliable guidance and basis can be provided for design of intelligent vehicle chassis stability control in the future.

Description

Technical Field

[0001] This invention belongs to the field of autonomous vehicle technology, specifically a method for quantitative evaluation of vehicle stability based on three-dimensional phase space. Background Technology

[0002] Vehicle stability assessment is a prerequisite for chassis stability control strategy design. The design of quantitative evaluation indicators for vehicle stability is beneficial for accurately and efficiently assessing complex dynamic performance, and provides guidance for better exploring the potential of controllers. Therefore, quantitative stability assessment methods have gradually become a focus of research and discussion.

[0003] Currently, various simple phase planes, such as those based on the center of gravity sideslip angle-center of gravity sideslip angular velocity, the center of gravity sideslip angle-yaw rate, and the front wheel sideslip angle-rear wheel sideslip angle, have been applied in vehicle stability assessment. The phase plane method, given the initial motion conditions of the vehicle's nonlinear dynamics model, allows observation of the phase trajectory and the changing trend of the equilibrium saddle point on the phase plane to determine the vehicle's stability state. However, these two-dimensional phase planes only reflect the vehicle's lateral and yaw motions, neglecting the influence of roll variables on the vehicle's stability state. Therefore, constructing a three-dimensional phase space of "lateral velocity-yaw rate-roll angle" can effectively compensate for the shortcomings of traditional two-dimensional phase planes, intuitively characterizing and analyzing the vehicle's lateral and roll stability states. However, this method can only qualitatively analyze the vehicle's stable, critically unstable, and unstable operating states, making it difficult to accurately quantify the dynamic motion requirements of the vehicle in different stability states regarding stability, comfort, and handling. This, to some extent, limits the applicability of stability phase space assessment. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a vehicle stability quantification assessment method based on three-dimensional phase space. This method can establish a standardized stability quantification assessment index according to different vehicle driving states, which is beneficial for accurately and comprehensively analyzing complex vehicle dynamics performance and can provide reliable guidance and basis for the design of future intelligent vehicle chassis stability control.

[0005] The technical solution of this invention is described below in conjunction with the accompanying drawings:

[0006] This invention provides a method for quantitatively evaluating vehicle stability based on three-dimensional phase space, comprising the following steps:

[0007] Step 1: Establish a three-dimensional phase space based on the vehicle dynamics model, consisting of lateral speed, yaw rate, and roll angle.

[0008] Step 2: Design a method for selecting the boundary state points of lateral and roll stability, and apply a three-dimensional convex hull to form an envelope stability domain, mapping the lateral and roll stability constraints to a comprehensive stability region in phase space;

[0009] Step 3: Based on the minimum distance and relative position between the state point and the determined stable region, design a geometric distance quantification function to obtain a stability index, which is used to quantitatively evaluate the stability state of the vehicle.

[0010] Furthermore, the specific method for step one is as follows:

[0011] 11) The lateral, yaw, and roll motions of a vehicle are represented as follows:

[0012]

[0013] In the formula, m is the total vehicle mass; F y The lateral force of the tires is represented by the subscripts ij∈{fl,fr,rl,rr}, which represent the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; δ f Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively. φ is the lateral acceleration; h is the distance from the center of gravity of the sprung mass to the center of tilt; g is the acceleration due to gravity; φ is the lateral acceleration. r Let be the disturbance vector given by the road surface inclination angle; r is the yaw rate. φ is the yaw acceleration; φ is the roll angle. This refers to the roll angular velocity; The roll acceleration; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; I z I is the moment of inertia about the z-axis; x k is the moment of inertia about the x-axis. φ For roll stiffness; C φ For roll damping;

[0014] 12) Side slip angle α of the four wheels ij Described as:

[0015]

[0016] In the formula, α ij Let δ be the tire slip angle, with subscripts ij∈{fl,fr,rl,rr} representing the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; f Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively; B t The wheelbase is r; the yaw rate is l.f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively.

[0017] 13) Vertical load F of the four tires zij Described as:

[0018]

[0019] In the formula, F zij The vertical load on the tires is represented by subscripts ij∈{fl,fr,rl,rr}, which represent the distribution of the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; m is the total mass of the vehicle; g is the acceleration due to gravity; B t The wheelbase; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; L d The distance from the front axle to the rear axle; a y h is the lateral acceleration. m The distance from the center of gravity of the sprung mass to the ground; m s φ is the sprung mass; h is the distance from the center of gravity of the sprung mass to the roll center; φ is the roll angle.

[0020] Furthermore, the specific method for step two is as follows:

[0021] 21) Based on the established vehicle dynamics model, different road surface adhesion coefficients μ and front wheel steering angles δ are used to determine the optimal vehicle dynamics model. f Longitudinal vehicle speed v x roll acceleration Under the given conditions, construct a three-dimensional phase space of lateral vehicle speed - yaw rate - roll angle, i.e., -r - φ;

[0022] 22) By setting dynamic threshold boundaries for the centroid sideslip angle β and the lateral load transfer rate, lateral and roll stability constraints are established; the lateral stability constraints are expressed as:

[0023]

[0024] In the formula, β is the centroid sideslip angle; α rmax v is the rear wheel slip angle corresponding to the peak lateral force in the Magic Tire model. x r is the longitudinal speed; r is the yaw rate; l r This is the distance from the vehicle's center of gravity to the rear axle.

[0025] The constraints for establishing vehicle roll stability using lateral load transfer rate are as follows:

[0026]

[0027] In the formula, LTR is the lateral load transfer rate; Fz Let be the vertical load on the tire, and let ij∈{fl,fr,rl,rr} be the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively.

[0028] 23) Based on the stability constraints of the design, the stability boundary point selection conditions are customized to obtain the lateral and tilt stability boundary points. Then, the three-dimensional convex hull method is used to form the minimum envelope polyhedron corresponding to the boundary point.

[0029] 24) Select the stability boundary points in the overlapping part of the lateral and roll stability regions, and continue to use the three-dimensional convex hull method to construct the vehicle's comprehensive stability region.

[0030] Furthermore, the specific method for customizing the screening conditions for stable boundary state points in step 23) is as follows:

[0031] By analyzing the phase trajectory change trend in phase space, and selecting the state points that critically satisfy the lateral and tilt stability constraints during the state change process, these points are used as the boundary state points for lateral and tilt stability.

[0032] Furthermore, the specific method for step three is as follows:

[0033] 31) Design the geometric distance function as follows:

[0034]

[0035] In the formula, SI is the stability index; κ is the sign variable of the stability index. If the state point is located inside the stable region, then κ = 1; otherwise, κ = -1; if the state point is located exactly on the boundary of the stable region, then κ = 0. The current state point (v) y0 The minimum distance between (r0, φ0) and the envelope of the integrated stable region; This is the minimum distance between the origin and the envelope of the overall stable region;

[0036] 32) The stability of a vehicle is determined by the Stability Index (SI), as follows:

[0037] When SI > 1, the vehicle's driving state is stable.

[0038] When -1 < SI ≤ 1, the vehicle's driving state is in a critical stable state.

[0039] When SI ≤ -1, the vehicle's driving state is unstable.

[0040] The beneficial effects of this invention are as follows:

[0041] 1) This invention is based on a vehicle dynamics model and different road surface adhesion coefficients μ and front wheel steering angles δ. fLongitudinal vehicle speed v x roll acceleration Conditions, construct lateral vehicle speed - yaw rate - roll angle (v) y The three-dimensional phase space (r-φ) can intuitively characterize the lateral and roll stability of a vehicle.

[0042] 2) Based on the three-dimensional phase space, this invention designs a method for screening the boundary state points of lateral and tilt stability, and applies a three-dimensional convex hull to form an envelope stability domain, mapping the lateral and tilt stability constraints to a comprehensive stability region in the phase space;

[0043] 3) Based on the minimum distance between the state point and the determined stable region and their relative positions, this invention designs a geometric distance quantification function to obtain the stability index. The stability quantification evaluation index can be updated in real time with the change of vehicle driving state, which can provide a basis for the design of vehicle chassis stability control. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of a vehicle stability quantification evaluation architecture based on three-dimensional phase space.

[0046] Figure 2a A schematic diagram of a three-degree-of-freedom vehicle dynamics model from one angle;

[0047] Figure 2b This is a schematic diagram of a three-degree-of-freedom vehicle dynamics model from another angle.

[0048] Figure 3 This is a schematic diagram of phase trajectory stability analysis in phase space;

[0049] Figure 4 A schematic diagram illustrating the selection criteria for stable boundary state points;

[0050] Figure 5 This is a schematic diagram illustrating the division of lateral and tilt stability regions based on phase space.

[0051] Figure 6 This is a schematic diagram of the comprehensive stable region division based on phase space;

[0052] Figure 7 This is a schematic diagram of the stability quantification evaluation index analysis based on phase space;

[0053] Figure 8 This is a schematic diagram of the reference trajectory for the double-track shifting operation.

[0054] Figure 9a This is a schematic diagram illustrating the changing trend of the vehicle's center of gravity sideslip angle under double lane change conditions.

[0055] Figure 9b This is a schematic diagram illustrating the variation trend of yaw rate under double lane change conditions.

[0056] Figure 9c This is a schematic diagram illustrating the trend of roll angle variation under double lane change conditions.

[0057] Figure 9d This is a schematic diagram illustrating the variation trend of roll angular velocity under double lane change conditions.

[0058] Figure 10a This is a diagram illustrating the changes in the front wheel steering angle;

[0059] Figure 10b This is a schematic diagram showing the changes in the stability index SI. Detailed Implementation

[0060] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0061] Example 1

[0062] See Figure 1 This embodiment provides a method for quantitative evaluation of vehicle stability based on three-dimensional phase space, including the following steps:

[0063] Step 1: Establish a three-dimensional phase space based on the vehicle dynamics model, consisting of lateral speed, yaw rate, and roll angle. The specific method is as follows:

[0064] 11) This step evaluates the vehicle's lateral, yaw, and roll motions. Assuming the longitudinal speed remains constant and ignoring the influence of four-wheel torque on chassis motion, a three-degree-of-freedom vehicle dynamics model is constructed as shown in Figure 2. The lateral, yaw, and roll motions can be expressed as:

[0065]

[0066]

[0067] In the formula, m is the total vehicle mass; F y The lateral force of the tires is represented by the subscripts ij∈{fl,fr,rl,rr}, which represent the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; δf Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively. φ is the lateral acceleration; h is the distance from the center of gravity of the sprung mass to the center of tilt; g is the acceleration due to gravity; φ is the lateral acceleration. r Let be the disturbance vector given by the road surface inclination angle; r is the yaw rate. φ is the yaw acceleration; φ is the roll angle. This refers to the roll angular velocity; The roll acceleration; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; I z I is the moment of inertia about the z-axis; x k is the moment of inertia about the x-axis. φ For roll stiffness; C φ For roll damping;

[0068] 12) Side slip angle α of the four wheels ij Described as:

[0069]

[0070] In the formula, α ij Let δ be the tire slip angle, with subscripts ij∈{fl,fr,rl,rr} representing the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; f Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively; B t The wheelbase is r; the yaw rate is l. f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively.

[0071] 13) When the vehicle turns, there is a certain axle load transfer, and the vertical load F of the four tires... zij Described as:

[0072]

[0073] In the formula, F zij The vertical load on the tires is represented by subscripts ij∈{fl,fr,rl,rr}, which represent the distribution of the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; m is the total mass of the vehicle; g is the acceleration due to gravity; B t The wheelbase; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; L d The distance from the front axle to the rear axle; a y h is the lateral acceleration. mThe distance from the center of gravity of the sprung mass to the ground; m s φ is the sprung mass; h is the distance from the center of gravity of the sprung mass to the roll center; φ is the roll angle.

[0074] Step 2: Design a method for selecting the boundary state points between lateral and roll stability, and apply a three-dimensional convex hull to form an envelope stability domain, mapping the lateral and roll stability constraints to a comprehensive stability region in phase space. The specific method is as follows:

[0075] 21) To intuitively characterize the lateral and roll stability of the vehicle, this step, based on the established vehicle dynamics model, uses different road adhesion coefficients μ and front wheel steering angles δ. f Longitudinal vehicle speed v x roll acceleration Conditions, constructing such Figure 3 The lateral speed - yaw rate - roll angle shown is v y -r-φ three-dimensional phase space;

[0076] exist Figure 3 In the above, the corresponding driving condition parameters are μ=0.85, δ f =0deg,v x =90km / h, Gray dots represent different initial states of the vehicle; red lines represent unstable phase trajectories that gradually diverge out of phase space, indicating that the vehicle gradually becomes unstable; green lines represent stable phase trajectories with a convergent trend, indicating that the vehicle has a certain degree of stability self-control capability under this operating condition.

[0077] 22) Although observing the changing trend of phase trajectories in phase space can intuitively determine the lateral and roll stability of a vehicle under different motion conditions, this method cannot quantitatively characterize the vehicle's motion state and is difficult to provide guidance for the design of chassis stability control strategies. This invention establishes lateral and roll stability constraints by setting dynamic threshold boundaries for the centroid sideslip angle β and the lateral load transfer rate; the lateral stability constraints are expressed as:

[0078]

[0079] In the formula, β is the centroid sideslip angle; α rmax v is the rear wheel slip angle corresponding to the peak lateral force in the Magic Tire model. x r is the longitudinal speed; r is the yaw rate; l r This is the distance from the vehicle's center of gravity to the rear axle.

[0080] The constraints for establishing vehicle roll stability using lateral load transfer rate are as follows:

[0081]

[0082] In the formula, LTR is the lateral load transfer rate; F z Let be the vertical load on the tire, and let ij∈{fl,fr,rl,rr} be the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively.

[0083] 23) Based on the stability constraints of the design, customize as follows: Figure 4 The stability boundary state point selection criteria are shown. Specifically, by analyzing the phase trajectory change trend in phase space, state points that critically satisfy the lateral and roll stability constraints during state change are selected as the thresholds. Figure 5 The boundary point between lateral and tilt stability in the middle. Figure 5 In the above, the corresponding driving condition parameters are the road adhesion coefficient μ = 0.85 and the front wheel steering angle δ. f =5deg, longitudinal vehicle speed v x =90km / h, roll angle acceleration Based on this, a three-dimensional convex hull method is used to form the minimum envelope polyhedrons corresponding to these boundary state points. The yellow polyhedron represents the lateral stability region of the vehicle, and the blue polyhedron represents the roll stability region of the vehicle.

[0084] 24) Select the stable boundary points in the overlapping parts of the lateral and tilt stable regions, and continue to use the three-dimensional convex hull method to construct, as shown in the figure. Figure 6 The diagram shows the vehicle's overall stability region. Accurately defined stability regions facilitate real-time and reliable assessment of driving conditions, thus providing a foundation for the design of quantitative stability evaluation indices.

[0085] Step 3: Based on the minimum distance and relative position between the state point and the determined stable region, design a geometric distance quantization function to obtain a stability index, which is used to quantitatively evaluate the vehicle's stability state. The specific method is as follows:

[0086] 31) To quantitatively characterize the stability state of a vehicle, such as Figure 7 As shown, an analysis of the stability index is performed. Figure 7 In the above, the corresponding driving condition parameters are the road adhesion coefficient μ = 0.85 and the front wheel steering angle δ. f =5deg, longitudinal vehicle speed v x =90km / h, roll angle acceleration Set the current state point (v) y0 The minimum distance between (r0, φ0) and the envelope of the comprehensive stable region is defined as The minimum distance between the origin and the envelope of the integrated stable region is defined as Design the following geometric distance function to accurately assess vehicle stability:

[0087]

[0088] In the formula, SI is the stability index, and κ is the sign variable of the stability index. If the state point is located inside the stable region, then κ = 1; otherwise, κ = -1. If the state point is located exactly on the boundary of the stable region, then κ = 0.

[0089] 32) Vehicle driving states can be classified into three types: stable, critically stable, and unstable. The stability of a vehicle is determined by the Stability Index (SI), as follows:

[0090] When SI > 1, the vehicle's driving state is stable.

[0091] When -1 < SI ≤ 1, the vehicle's driving state is in a critical stable state.

[0092] When SI ≤ -1, the vehicle's driving state is unstable.

[0093] Example 2

[0094] This embodiment uses a co-simulation platform built with MATLAB / Simulink and the vehicle dynamics software CarSim to test the vehicle stability evaluation method designed in this patent. A double lane change scenario is selected to evaluate the vehicle's handling stability. The road adhesion coefficient is set to 0.85, the target vehicle speed is 90 km / h, and the reference trajectory is as follows. Figure 8 As shown.

[0095] Simulation results under the double line-shifting condition are as follows Figures 9a-9d As shown. From Figures 9a-9d The changes in the vehicle's center of gravity sideslip angle, yaw rate, roll angle, and roll rate can be observed. Figure 10a and Figure 10b The changes in front wheel steering angle and the stability index SI are displayed. The stability index SI can be used to analyze the vehicle's driving stability. The decrease in the stability index SI during periods such as 2.2-3.1s, 4.4-4.5s, and 5.9-6.1s indicates that the vehicle is gradually becoming unstable. At these times, the stability weights corresponding to the sideslip angle and roll angle in the controller can be increased accordingly, while the weights corresponding to yaw rate and roll rate in the controller can be decreased for yaw handling and roll comfort. From the above results, it can be concluded that the vehicle stability quantification assessment method based on three-dimensional phase space can obtain the stability quantification assessment index SI in real time based on the changing vehicle driving state. This is beneficial for adjusting the corresponding weight values ​​in the control strategy according to the stability index SI when designing chassis stability controllers, providing a reliable basis for the design of vehicle chassis stability control.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for quantitatively evaluating vehicle stability based on three-dimensional phase space, characterized in that, Includes the following steps: Step 1: Establish a three-dimensional phase space based on the vehicle dynamics model, consisting of lateral speed, yaw rate, and roll angle. Step 2: Design a method for selecting the boundary state points of lateral and roll stability, and apply a three-dimensional convex hull to form an envelope stability domain, mapping the lateral and roll stability constraints to a comprehensive stability region in phase space; Step 3: Based on the minimum distance and relative position between the state point and the determined stable region, design a geometric distance quantification function to obtain a stability index, which is used to quantitatively evaluate the stability state of the vehicle.

2. The vehicle stability quantitative evaluation method based on three-dimensional phase space according to claim 1, characterized in that, The specific method for step one is as follows: 11) The lateral, yaw, and roll motions of a vehicle are represented as follows: In the formula, m is the total vehicle mass; F y The lateral force of the tires is represented by the subscripts ij∈{fl,fr,rl,rr}, which represent the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; δ f Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively. φ is the lateral acceleration; h is the distance from the center of gravity of the sprung mass to the center of tilt; g is the acceleration due to gravity; φ is the lateral acceleration. r Let be the disturbance vector given by the road surface inclination angle; r is the yaw rate. φ is the yaw acceleration; φ is the roll angle. This refers to the roll angular velocity; The roll acceleration; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; I z I is the moment of inertia about the z-axis; x k is the moment of inertia about the x-axis. φ For roll stiffness; C φ For roll damping; 12) Side slip angle α of the four wheels ij Described as: In the formula, α ij Let δ be the tire slip angle, with subscripts ij∈{fl,fr,rl,rr} representing the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; f Input the front wheel steering angle; v y and v x These are the lateral and longitudinal vehicle speeds, respectively; B t The wheelbase is r; the yaw rate is l. f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively. 13) Vertical load F of the four tires zij Described as: In the formula, F zij The vertical load on the tires is represented by subscripts ij∈{fl,fr,rl,rr}, which represent the distribution of the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively; m is the total mass of the vehicle; g is the acceleration due to gravity; B t The wheelbase; l f and l r These are the distances from the vehicle's center of gravity to the front and rear axles, respectively; L d The distance from the front axle to the rear axle; a y h is the lateral acceleration. m The distance from the center of gravity of the sprung mass to the ground; m s φ is the sprung mass; h is the distance from the center of gravity of the sprung mass to the roll center; φ is the roll angle.

3. The vehicle stability quantitative evaluation method based on three-dimensional phase space according to claim 1, characterized in that, The specific method for step two is as follows: 21) Based on the established vehicle dynamics model, different road surface adhesion coefficients μ and front wheel steering angles δ are used to determine the optimal vehicle dynamics model. f Longitudinal vehicle speed v x roll acceleration Under the given conditions, construct a three-dimensional phase space of lateral vehicle speed - yaw rate - roll angle, i.e., -r - φ; 22) By setting dynamic threshold boundaries for the centroid sideslip angle β and the lateral load transfer rate, lateral and roll stability constraints are established; the lateral stability constraints are expressed as: In the formula, β is the centroid sideslip angle; α rmax v is the rear wheel slip angle corresponding to the peak lateral force in the Magic Tire model. x r is the longitudinal speed; r is the yaw rate; l r This is the distance from the vehicle's center of gravity to the rear axle. The constraints for establishing vehicle roll stability using lateral load transfer rate are as follows: In the formula, LTR is the lateral load transfer rate; F z Let be the vertical load on the tire, and let ij∈{fl,fr,rl,rr} be the left front wheel, left rear wheel, right front wheel, and right rear wheel, respectively. 23) Based on the stability constraints of the design, the stability boundary point selection conditions are customized to obtain the lateral and tilt stability boundary points. Then, the three-dimensional convex hull method is used to form the minimum envelope polyhedron corresponding to the boundary point. 24) Select the stability boundary points in the overlapping part of the lateral and roll stability regions, and continue to use the three-dimensional convex hull method to construct the vehicle's comprehensive stability region.

4. The vehicle stability quantitative evaluation method based on three-dimensional phase space according to claim 3, characterized in that, The specific method for customizing the stable boundary state point screening conditions in step 23) is as follows: By analyzing the phase trajectory change trend in phase space, and selecting the state points that critically satisfy the lateral and tilt stability constraints during the state change process, these points are used as the boundary state points for lateral and tilt stability.

5. The vehicle stability quantitative evaluation method based on three-dimensional phase space according to claim 1, characterized in that, The specific method for step three is as follows: 31) Design the geometric distance function as follows: In the formula, SI is the stability index; κ is the sign variable of the stability index. If the state point is located inside the stable region, then κ = 1; otherwise, κ = -1; if the state point is located exactly on the boundary of the stable region, then κ = 0. The current state point (v) y0 The minimum distance between (r0, φ0) and the envelope of the integrated stable region; This is the minimum distance between the origin and the envelope of the overall stable region; 32) The stability of a vehicle is determined by the Stability Index (SI), as follows: When SI > 1, the vehicle is in a stable state; When -1 < SI ≤ 1, the vehicle is in a critical stable state; When SI ≤ -1, the vehicle is in an unstable state.

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