Sensitivity evaluation method for control stability state parameters of chassis of electric vehicle

Abstract

The invention discloses an electric vehicle chassis control stability state parameter sensitivity evaluation method, which comprises the following steps: considering that the chassis control stability and trajectory tracking performance of an electric vehicle become relatively sensitive due to the redistribution of the whole electric vehicle equipment quality, the change of the geometric dimension and passenger or cargo loading; a nonlinear electric vehicle directional evaluation kinetic model is established, and a disturbance method and a central difference method are adopted to develop an electric vehicle chassis handling stability state parameter track sensitivity analysis method. According to a developed electric vehicle chassis control stability state parameter track sensitivity analysis method, electric vehicle chassis control stability state parameter sensitivity is quantitatively analyzed, and according to a sensitivity analysis result, an electric vehicle chassis control stability criterion is designed in combination with a specific vehicle type; and corresponding switching control is carried out according to the stability criterion, so that the chassis handling stability of the electric vehicle during running is ensured.

Description

Technical Field

[0001] This invention belongs to the field of vehicle active safety control, specifically relating to a method for sensitivity evaluation of the handling stability state parameters of an electric vehicle chassis. Background Technology

[0002] With economic development and rising living standards, the number of cars on the road has also increased. However, while traditional gasoline-powered vehicles bring convenience, they also pose increasingly serious energy and environmental problems. Driven by factors such as energy conservation, emission reduction, and climate change, new energy vehicles have gradually become a global trend, with pure electric vehicles being the main direction of development.

[0003] Electric vehicles eliminate the lengthy transmission links required by traditional internal combustion engine vehicles, such as gear shifting mechanisms, clutches, mechanical or hydraulic transmissions, drive shafts, drive axles, and mechanical differentials. This significantly shortens the mechanical transmission chain, eliminating the need for bulky engines, mechanical transmission devices, cooling systems, exhaust mufflers, fuel tanks, and many other mechanical auxiliary equipment and devices. This reduces the overall vehicle weight, lowers the vehicle's center of gravity, and increases the freedom in designing the vehicle's mass distribution. However, this change also makes the vehicle's driving safety more sensitive. The redistribution of mass, changes in geometry, and passenger or cargo loading make the chassis handling stability and trajectory tracking performance of electric vehicles relatively sensitive. However, current research on the sensitivity evaluation of the state parameters of electric vehicle chassis handling stability is relatively limited in the design and research of active safety control for electric vehicles. There is an urgent need to supplement relevant theories and technologies to support the design and development of active safety control systems for electric vehicles. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a sensitivity evaluation method for the handling stability state parameters of an electric vehicle chassis. To achieve the above objective, this invention provides the following solution:

[0005] A method for sensitivity evaluation of handling stability state parameters of an electric vehicle chassis includes the following steps:

[0006] S1. Establish a nonlinear electric vehicle orientation evaluation dynamic model and develop the trajectory sensitivity of the electric vehicle chassis handling stability state parameters:

[0007] Considering that the redistribution of the overall vehicle mass, changes in geometry, and the loading of passengers or cargo make the chassis handling stability and trajectory tracking performance of electric vehicles relatively sensitive, a nonlinear electric vehicle orientation evaluation dynamic model is established, and a trajectory sensitivity analysis method for the chassis handling stability state parameters of electric vehicles is developed using the perturbation method and the central difference method.

[0008] S2. Quantitative analysis of the sensitivity of the handling stability parameters of electric vehicle chassis:

[0009] Based on the nonlinear electric vehicle directional evaluation dynamic model, the key state parameters of electric vehicle chassis handling stability are quantitatively analyzed according to the developed electric vehicle chassis handling stability state parameter trajectory sensitivity analysis method.

[0010] S3. Design of handling stability criteria for electric vehicle chassis:

[0011] Based on the results of sensitivity quantitative analysis, and combined with the specific vehicle model, a chassis handling stability criterion is designed for electric vehicles. The chassis handling stability control of electric vehicles is then switched accordingly based on the stability criterion to ensure the chassis handling stability of the electric vehicle.

[0012] Optionally, in step S1, firstly, a nonlinear electric vehicle orientation evaluation dynamic model is established. This model includes longitudinal, lateral, yaw, and rolling motions. Based on d'Alembert's principle and the diagram, the derived vehicle dynamic equations are as follows:

[0013] Longitudinal movement:

[0014]

[0015] F f =μm n g

[0016] Lateral movement:

[0017]

[0018] Lateral and tilting motions:

[0019]

[0020] Where, m n Indicated as vehicle mass; F f For rolling resistance, V x V y Represented as longitudinal velocity and lateral velocity; r x r z Expressed as vehicle roll rate and yaw rate; F xij F yij This represents the longitudinal and lateral forces for each tire; F w This represents the resistance generated by tire rolling; C d It is expressed as the air drag coefficient; ρ represents the air density; A f The frontal area of ​​a vehicle when it is in motion; δ fl δ frIndicated as left front wheel steering angle, right front wheel steering angle; a x a y Represented as longitudinal acceleration and lateral acceleration; μ represents the road adhesion coefficient; β represents the centroid sideslip angle; I x I z I xz Expressed as the yaw moment of inertia about the x-axis, the yaw moment of inertia about the z-axis, and the product of the inertia of vehicle roll and yaw; l f0 l r0 b l0 b r0 This represents the distance from the front axle to the center of gravity, the distance from the rear axle to the center of gravity, the distance from the left wheel to the center of gravity, and the distance from the right wheel to the center of gravity; φ represents the vehicle roll angle; K φ Indicates the body roll stiffness; C φ h represents the vehicle roll damping coefficient. r This indicates the height of the roll axis from the ground when the vehicle is unloaded.

[0021] When the vehicle's mass changes, the inertial and geometric parameters of the electric vehicle also change. The coordinate vector of the centroid changes when an additional load is applied.

[0022]

[0023] The change in the coordinate vector of the centroid is:

[0024]

[0025] in,

[0026]

[0027] The change in vehicle mass due to increased load is as follows:

[0028] m n =m u +m p

[0029] The velocity change at the new center of mass after the change in the center of mass position and its differential form are:

[0030]

[0031] The equation for the vehicle body's rotational motion is obtained as follows:

[0032]

[0033] Among them, V, V p Represented as the velocity matrix of the vehicles before and after loading; r, Let M represent the vehicle's roll, pitch, and yaw angular velocity vectors and their antisymmetric matrices, and let M represent the matrix of external torques. During vehicle motion, the vehicle's moment of inertia and product of inertia are defined as follows:

[0034]

[0035] The change in the vehicle's yaw moment of inertia after loading is as follows:

[0036]

[0037] Assuming load m p Since it is a point load, the yaw moment of inertia is calculated as follows:

[0038]

[0039] Further results were obtained:

[0040]

[0041] Assuming the vehicle's center of gravity height remains constant, calculate the coordinates of the changed center of gravity position:

[0042]

[0043] Therefore, the yaw moment of inertia of an electric vehicle is calculated as follows:

[0044]

[0045] Meanwhile, the change in the center of mass caused by the variable load is considered; in the equation, the parameters of the tire model are calculated as follows:

[0046]

[0047] Among them, l f l r This is expressed as the distance between the front axle and the center of gravity, and the distance between the rear axle and the center of gravity after the vehicle is loaded; b f b r h represents the distance from the vehicle's center of gravity to the centers of the left and right wheels after loading. n Indicates the distance from the tilt axis to the ground after loading; x n y n z n This represents the coordinates of the vehicle's center of gravity after loading; L and B represent the vehicle's wheelbase and track width, respectively.

[0048] The nonlinear tire model uses the Pacejka tire model.

[0049]

[0050] Where Y represents the longitudinal tire force F xOr lateral tire-road force F y X represents the slip ratio s or the tire slip angle α; S h and S v This is represented by the horizontal and vertical drift of the curve; when longitudinal slip occurs, the stiffness parameters are calculated as follows:

[0051]

[0052] in,

[0053]

[0054] Under the condition of longitudinal slippage, the restoring torque is readily obtained as follows:

[0055] M z =M z0 (α,γ,F z )

[0056] M z0 =-t×F y0 +M zr

[0057] M zr =Dcos(Carctan(Bx))cosx

[0058] Among them, M zr This represents the residual self-aligning torque; γ represents the tire camber angle.

[0059] Secondly, the trajectory sensitivity of the electric vehicle chassis handling stability state parameter is developed and defined as follows:

[0060] The observation results of the vehicle chassis handling stability state parameter estimation based on the above model are described by the variable y, and the input state parameters in the vehicle are represented by the vector X:

[0061] X = [x1, x2, x3, ... x n ]

[0062] y i =f i (x)=f i (x1,x2,x3,...x n )

[0063] If the center value of the parameter is defined as x0, then the corresponding model output value is:

[0064] y i =f i (x)=f i (x 01 +Δx1,x 02 +Δx2,x 03 +Δx3,...x0n +Δx n )

[0065] =f i (x0+Δx)i=1,2,3...n

[0066] Therefore, the change in the output of the nonlinear electric vehicle orientation evaluation dynamic model caused by the change in the guiding parameters due to external disturbances is as follows:

[0067] Δy i =f i (x0+Δx)-f i (x0)i=1,2,3...n

[0068] For y i Find the k-th order partial derivative at the parameter center value x0:

[0069]

[0070] Further truncation and solution yields the k-th order sensitivity as:

[0071]

[0072] Further, the solution can be developed as follows:

[0073]

[0074] In x i The partial derivative reflects its sensitivity as follows:

[0075]

[0076] Among them, S i Represented as the vehicle chassis handling stability state parameter x i Sensitivity;

[0077] Considering the vehicle state parameter x i Since the units of measurement are inconsistent, they are standardized and introduced into a dimensionless variable as follows:

[0078]

[0079] Where σ represents the parameter x i The degree of disturbance change;

[0080] Considering the complexity of the dynamic model for directional evaluation of electric vehicles, a central difference is introduced to further simplify the sensitivity evaluation of the chassis handling stability state parameters of electric vehicles, as follows:

[0081]

[0082] Among them, X i+0.5 With Xi-0.5 The terms are differences, namely X. i+0.5 =(x1,x2,...,x i +0.5Δx i ,...,x n ) and X i -0.5 =(x1,x2,...,x i -0.5Δx i ,...,x n );

[0083] Defined at point X i+0.5 With X i-0.5 The central difference at step size Δx is as follows:

[0084]

[0085] Among them, X i+1 X i With X i-1 The terms are differences, namely X. i+1 =(x1,x2,...,x i +Δx i ,...,x n ), X i =(x1,x2,...,x i ,...,x n ) and X i-1 =(x1,x2,...,x i -Δx i ,...,x n );

[0086] To improve the accuracy of its vehicle state parameter sensitivity, a second-order central difference is further introduced:

[0087]

[0088] Meanwhile, the calculation result of the nth-order central difference is defined as follows:

[0089] Δ n y i =Δ n-1 y i+0.5 -Δ n-1 y i-0.5 .

[0090] Optionally, in step S2, the sensitivity of the electric vehicle chassis handling stability state parameters is evaluated according to the defined electric vehicle chassis handling stability state parameter trajectory sensitivity analysis method, and the state variables of the vehicle model are defined as follows:

[0091] x s(t)=[V x V y βr z r x φ]

[0092] The vehicle load parameters for disturbance analysis are defined as follows:

[0093] θ s (t)=[m p x p y p z p ]

[0094] Further derivation of its state parameter sensitivity reveals typical vehicle state parameter sensitivity;

[0095] Wherein, the longitudinal velocity V is defined x The sensitivity of the centroid sideslip angle β and sideslip angle φ is as follows;

[0096] Defined in m p V under disturbance x The trajectory sensitivity is:

[0097]

[0098] Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change;

[0099] The average value of its local sensitivity is defined as:

[0100]

[0101] Defined in x p V under disturbance x The trajectory sensitivity is:

[0102]

[0103] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as:

[0104]

[0105] Defined in y p V under disturbance x The trajectory sensitivity is:

[0106]

[0107] Where, y′ pRepresented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change;

[0108] The mean of its local sensitivity is defined as:

[0109]

[0110] Defined in z p V under disturbance x The trajectory sensitivity is:

[0111]

[0112] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean of the local sensitivity is defined as:

[0113]

[0114] Defined in m p The sensitivity of the β trajectory under disturbance is:

[0115]

[0116] Where, m′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its mean local sensitivity is defined as:

[0117]

[0118] Defined in x p The sensitivity of the β trajectory under disturbance is:

[0119]

[0120] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the local sensitivity is defined with the mean value as:

[0121]

[0122] Defined in y p The sensitivity of the β trajectory under disturbance is:

[0123]

[0124] Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean value of the local sensitivity is defined as:

[0125]

[0126] Defined in z p The sensitivity of the β trajectory under disturbance is:

[0127]

[0128] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after perturbation, its mean local sensitivity is defined as:

[0129]

[0130] Defined in m p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0131]

[0132] Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change;

[0133] The average value of its local sensitivity is defined as:

[0134]

[0135] Defined in x p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0136]

[0137] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as:

[0138]

[0139] Defined in y p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0140]

[0141] Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change;

[0142] The mean of its local sensitivity is defined as:

[0143]

[0144] Defined in z p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0145]

[0146] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the average value of the local sensitivity is defined as:

[0147]

[0148] Optionally, in step S3, the trajectory sensitivity definition and local sensitivity average value analysis method of the electric vehicle chassis handling stability state parameters are used for analysis, and a polynomial is used to fit them. During the analysis, the observation of the electric vehicle chassis handling stability state parameters is completed using volumetric Kalman Array (CKF). The sensitivity of each state parameter can be evaluated and compared through analysis and observation. Typical electric vehicle chassis handling stability state parameters are evaluated for the vehicle's center of gravity sideslip angle β and load mass m. p The load longitudinal position x is most sensitive to its estimation effect. p and the lateral position of the load y p It also has some impact, the vertical position of the load z p The impact is minimal, even negligible; for the vehicle's center of gravity roll angle φ, the longitudinal position of the load x p and load mass m p The mean sensitivity values ​​of and are not significantly different, and the tilt angle is relatively sensitive to them; the lateral position of the load y p and the load perpendicular position z p The impact is relatively small and much smaller than the former two. Furthermore, based on the sensitivity analysis results, and combined with the specific vehicle model, the phase plane method is used to design the electric vehicle chassis handling stability criterion. Then, the electric vehicle chassis handling stability control is based on the stability criterion to perform corresponding switching control to ensure the chassis handling stability of the electric vehicle.

[0149] The corresponding design criteria for the yaw stability of electric vehicle chassis are as follows:

[0150]

[0151] Here Ω βlimTo obtain the boundary threshold of yaw stability of electric vehicle chassis using the phase plane method based on the sensitivity results, c1, c2, and c3 are specific vehicle constants determined by combining the phase plane method with the sensitivity evaluation results and using polynomial fitting.

[0152] The corresponding design criteria for the roll stability of electric vehicle chassis are as follows:

[0153]

[0154] Among them, Ω φlim To obtain the boundary threshold for the roll stability of the electric vehicle chassis using the phase plane method based on sensitivity and specific vehicle models.

[0155] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant technological advancements:

[0156] 1. In the process of establishing a nonlinear electric vehicle directional evaluation dynamic model, this invention considers the influence of the redistribution of electric vehicle mass, changes in geometric dimensions, and passenger or cargo loading on the chassis handling stability of the electric vehicle, and develops and defines the trajectory sensitivity of the electric vehicle chassis handling stability state parameter.

[0157] 2. This invention performs quantitative sensitivity analysis of the state parameters of electric vehicle chassis handling stability. Based on the sensitivity analysis results and combined with the specific vehicle model, it designs the electric vehicle chassis handling stability criteria. Then, the electric vehicle chassis handling stability control performs corresponding switching control according to the stability criteria to ensure the chassis handling stability of the electric vehicle. Attached Figure Description

[0158] Figure 1 This is a flowchart of a method for evaluating the sensitivity of handling stability state parameters of an electric vehicle chassis according to an embodiment of the present invention;

[0159] Figure 2 This invention provides a directional evaluation dynamic model for electric vehicles under additional loads, considering changes in the vehicle's center of gravity.

[0160] Figure 3 These are the vehicle center of gravity roll angle sensitivity analysis results of the present invention, where (a) is m p A schematic diagram of the sensitivity results of the centroid tilt angle in the perturbation analysis, (b) is x p A schematic diagram of the sensitivity results for the centroid tilt angle in the perturbation analysis. Detailed Implementation

[0161] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0162] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0163] This invention proposes a sensitivity evaluation method for the handling stability state parameters of an electric vehicle chassis, such as... Figure 1 As shown, the specific steps include:

[0164] S1. Establish a nonlinear electric vehicle orientation evaluation dynamic model and develop the trajectory sensitivity of the electric vehicle chassis handling stability state parameters:

[0165] Considering that the redistribution of the overall vehicle mass, changes in geometry, and the loading of passengers or cargo make the chassis handling stability and trajectory tracking performance of electric vehicles relatively sensitive, a nonlinear electric vehicle orientation evaluation dynamic model is established, and a trajectory sensitivity analysis method for the chassis handling stability state parameters of electric vehicles is developed using the perturbation method and the central difference method.

[0166] S2. Quantitative analysis of the sensitivity of the handling stability parameters of electric vehicle chassis:

[0167] Based on the nonlinear electric vehicle directional evaluation dynamic model, the key state parameters of electric vehicle chassis handling stability are quantitatively analyzed according to the developed electric vehicle chassis handling stability state parameter trajectory sensitivity analysis method.

[0168] S3. Design of handling stability criteria for electric vehicle chassis:

[0169] Based on the results of sensitivity quantitative analysis, and combined with the specific vehicle model, a chassis handling stability criterion is designed for electric vehicles. The chassis handling stability control of electric vehicles is then switched accordingly based on the stability criterion to ensure the chassis handling stability of the electric vehicle.

[0170] Further, in step S1, firstly, as Figure 2 As shown, a nonlinear electric vehicle orientation evaluation dynamic model is established. This model includes longitudinal, lateral, yaw, and rolling motions. Based on d'Alembert's principle and the figure, the derived vehicle dynamic equations are as follows:

[0171] Longitudinal movement:

[0172]

[0173] F f =μm n g

[0174] Lateral movement:

[0175]

[0176] Lateral and tilting motions:

[0177]

[0178] Where, m n Indicated as vehicle mass; F f For rolling resistance, V x V y Represented as longitudinal velocity and lateral velocity; r x r z Expressed as vehicle roll rate and yaw rate; F xij F yij This represents the longitudinal and lateral forces for each tire; F w This represents the resistance generated by tire rolling; C d It is expressed as the air drag coefficient; ρ represents the air density; A f The frontal area of ​​a vehicle when it is in motion; δ fl δ fr Indicated as left front wheel steering angle, right front wheel steering angle; a x a y Represented as longitudinal acceleration and lateral acceleration; μ represents the road adhesion coefficient; β represents the centroid sideslip angle; I x I z I xz Expressed as the yaw moment of inertia about the x-axis, the yaw moment of inertia about the z-axis, and the product of the inertia of vehicle roll and yaw; l f0 l r0 b l0 b r0 This represents the distance from the front axle to the center of gravity, the distance from the rear axle to the center of gravity, the distance from the left wheel to the center of gravity, and the distance from the right wheel to the center of gravity; φ represents the vehicle roll angle; K φ Indicates the body roll stiffness; C φ h represents the vehicle roll damping coefficient. r This indicates the height of the roll axis from the ground when the vehicle is unloaded.

[0179] When the vehicle's mass changes, the inertial and geometric parameters of the electric vehicle also change. The coordinate vector of the centroid changes when an additional load is applied.

[0180]

[0181] The change in the coordinate vector of the centroid is:

[0182]

[0183] in,

[0184]

[0185] The change in vehicle mass due to increased load is as follows:

[0186] m n =m u +m p

[0187] The velocity change at the new center of mass after the change in the center of mass position and its differential form are:

[0188]

[0189] The equation for the vehicle body's rotational motion is obtained as follows:

[0190]

[0191] Among them, V, V p Represented as the velocity matrix of the vehicles before and after loading; r, Let M represent the vehicle's roll, pitch, and yaw angular velocity vectors and their antisymmetric matrices, and let M represent the matrix of external torques. During vehicle motion, the vehicle's moment of inertia and product of inertia are defined as follows:

[0192]

[0193] The change in the vehicle's yaw moment of inertia after loading is as follows:

[0194]

[0195] Assuming load m p Since it is a point load, the yaw moment of inertia is calculated as follows:

[0196]

[0197] Further results were obtained:

[0198]

[0199] Assuming the vehicle's center of gravity height remains constant, calculate the coordinates of the changed center of gravity position:

[0200]

[0201] Therefore, the yaw moment of inertia of an electric vehicle is calculated as follows:

[0202]

[0203] Meanwhile, the change in the center of mass caused by the variable load is considered; in the equation, the parameters of the tire model are calculated as follows:

[0204]

[0205] Among them, l f l r This is expressed as the distance between the front axle and the center of gravity, and the distance between the rear axle and the center of gravity after the vehicle is loaded; b f b r h represents the distance from the vehicle's center of gravity to the centers of the left and right wheels after loading. n Indicates the distance from the tilt axis to the ground after loading; x n y n z n This represents the coordinates of the vehicle's center of gravity after loading; L and B represent the vehicle's wheelbase and track width, respectively.

[0206] The nonlinear tire model uses the Pacejka tire model.

[0207]

[0208] Where Y represents the longitudinal tire force F x Or lateral tire-road force F y X represents the slip ratio s or the tire slip angle α; S h and S v This is represented by the horizontal and vertical drift of the curve; when longitudinal slip occurs, the stiffness parameters are calculated as follows:

[0209]

[0210] in,

[0211]

[0212] Under the condition of longitudinal slippage, the restoring torque is readily obtained as follows:

[0213] M z =M z0 (α,γ,F z )

[0214] M z0 =-t×F y0 +M zr

[0215] M zr =Dcos(Carctan(Bx))cosx

[0216] Among them, M zr This represents the residual self-aligning torque; γ represents the tire camber angle.

[0217] Secondly, the trajectory sensitivity of the electric vehicle chassis handling stability state parameter is developed and defined as follows:

[0218] The observation results of the vehicle chassis handling stability state parameter estimation based on the above model are described by the variable y, and the input state parameters in the vehicle are represented by the vector X:

[0219] X = [x1, x2, x3, ... x n ]

[0220] y i =f i (x)=f i (x1,x2,x3,...x n )

[0221] If the center value of the parameter is defined as x0, then the corresponding model output value is:

[0222] y i =f i (x)=f i (x 01 +Δx1,x 02 +Δx2,x 03 +Δx3,...x 0n +Δx n )

[0223] =f i (x0+Δx)i=1,2,3...n

[0224] Therefore, the change in the output of the nonlinear electric vehicle orientation evaluation dynamic model caused by the change in the guiding parameters due to external disturbances is as follows:

[0225] Δy i =f i (x0+Δx)-f i (x0)i=1,2,3...n

[0226] For y i Find the k-th order partial derivative at the parameter center value x0:

[0227]

[0228] Further truncation and solution yields the k-th order sensitivity as:

[0229]

[0230] Further, the solution can be developed as follows:

[0231]

[0232] In x i The partial derivative reflects its sensitivity as follows:

[0233]

[0234] Among them, S i Represented as the vehicle chassis handling stability state parameter x i Sensitivity;

[0235] Considering the vehicle state parameter x i Since the units of measurement are inconsistent, they are standardized and introduced into a dimensionless variable as follows:

[0236]

[0237] Where σ represents the parameter x i The degree of disturbance change;

[0238] Considering the complexity of the dynamic model for directional evaluation of electric vehicles, a central difference is introduced to further simplify the sensitivity evaluation of the chassis handling stability state parameters of electric vehicles, as follows:

[0239]

[0240] Among them, X i+0.5 With X i-0.5 The terms are differences, namely X. i+0.5 =(x1,x2,...,x i +0.5Δx i ,...,x n ) and X i -0.5 =(x1,x2,...,x i -0.5Δx i ,...,x n );

[0241] Defined at point X i+0.5 With X i-0.5 The central difference at step size Δx is as follows:

[0242]

[0243] Among them, X i+1 X i With X i-1 The terms are differences, namely X. i+1 =(x1,x2,...,x i +Δx i ,...,x n ), X i =(x1,x2,...,x i ,...,x n ) and X i-1 =(x1,x2,...,x i -Δxi ,...,x n );

[0244] To improve the accuracy of its vehicle state parameter sensitivity, a second-order central difference is further introduced:

[0245]

[0246] Meanwhile, the calculation result of the nth-order central difference is defined as follows:

[0247] Δ n y i =Δ n-1 y i+0.5 -Δ n-1 y i-0.5 .

[0248] Furthermore, in step S2, the sensitivity of the electric vehicle chassis handling stability state parameters is evaluated according to the defined electric vehicle chassis handling stability state parameter trajectory sensitivity analysis method, and the state variables of the vehicle model are defined as follows:

[0249] x s (t)=[V x V y βr z r x φ]

[0250] The vehicle load parameters for disturbance analysis are defined as follows:

[0251] θ s (t)=[m p x p y p z p ]

[0252] Further derivation of its state parameter sensitivity reveals typical vehicle state parameter sensitivity;

[0253] Wherein, the longitudinal velocity V is defined x The sensitivity of the centroid sideslip angle β and sideslip angle φ is as follows;

[0254] Defined in m p V under disturbance x The trajectory sensitivity is:

[0255]

[0256] Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change;

[0257] The average value of its local sensitivity is defined as:

[0258]

[0259] Defined in x p V under disturbance x The trajectory sensitivity is:

[0260]

[0261] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as:

[0262]

[0263] Defined in y p V under disturbance x The trajectory sensitivity is:

[0264]

[0265] Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change;

[0266] The mean of its local sensitivity is defined as:

[0267]

[0268] Defined in z p V under disturbance x The trajectory sensitivity is:

[0269]

[0270] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean of the local sensitivity is defined as:

[0271]

[0272] Defined in m p The sensitivity of the β trajectory under disturbance is:

[0273]

[0274] Where, m′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its mean local sensitivity is defined as:

[0275]

[0276] Defined in x p The sensitivity of the β trajectory under disturbance is:

[0277]

[0278] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the local sensitivity is defined with the mean value as:

[0279]

[0280] Defined in y p The sensitivity of the β trajectory under disturbance is:

[0281]

[0282] Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean value of the local sensitivity is defined as:

[0283]

[0284] Defined in z p The sensitivity of the β trajectory under disturbance is:

[0285]

[0286] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after perturbation, its mean local sensitivity is defined as:

[0287]

[0288] Defined in m p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0289]

[0290] Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change;

[0291] The average value of its local sensitivity is defined as:

[0292]

[0293] Defined in x p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0294]

[0295] Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as:

[0296]

[0297] Defined in y p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0298]

[0299] Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change;

[0300] The mean of its local sensitivity is defined as:

[0301]

[0302] Defined in z p The trajectory sensitivity of the roll angle φ under disturbance conditions is:

[0303]

[0304] Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the average value of the local sensitivity is defined as:

[0305]

[0306] Furthermore, in step S3, the trajectory sensitivity definition and local sensitivity average value analysis method of the electric vehicle chassis handling stability state parameters are used for analysis, and a polynomial is used to fit them. During the analysis, the observation of the electric vehicle chassis handling stability state parameters is completed using the volumetric Kalman Array (CKF). The sensitivity results of each state parameter can be evaluated and compared through analysis and observation. (See schematic diagram below.) Figure 3 As shown; typical electric vehicle chassis handling stability parameters were evaluated for the vehicle's center of gravity sideslip angle β and load mass m. p The load longitudinal position x is most sensitive to its estimation effect. p and the lateral position of the load y p It also has some impact, the vertical position of the load zp The impact is minimal, even negligible; for the vehicle's center of gravity roll angle φ, the longitudinal position of the load x p and load mass m p The mean sensitivity values ​​of and are not significantly different, and the tilt angle is relatively sensitive to them; the lateral position of the load y p and the load perpendicular position z p The impact is relatively small and much smaller than the former two. Furthermore, based on the sensitivity analysis results, and combined with the specific vehicle model, the phase plane method is used to design the electric vehicle chassis handling stability criterion. Then, the electric vehicle chassis handling stability control is based on the stability criterion to perform corresponding switching control to ensure the chassis handling stability of the electric vehicle.

[0307] The corresponding design criteria for the yaw stability of electric vehicle chassis are as follows:

[0308]

[0309] Here Ω βlim To obtain the boundary threshold of yaw stability of electric vehicle chassis using the phase plane method based on the sensitivity results, c1, c2, and c3 are specific vehicle constants determined by combining the phase plane method with the sensitivity evaluation results and using polynomial fitting.

[0310] The corresponding design criteria for the roll stability of electric vehicle chassis are as follows:

[0311]

[0312] Among them, Ω φlim To obtain the boundary threshold for the roll stability of the electric vehicle chassis using the phase plane method based on sensitivity and specific vehicle models.

[0313] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for sensitivity evaluation of handling stability state parameters of an electric vehicle chassis, characterized in that, Includes the following steps: S1. Establish a nonlinear electric vehicle orientation evaluation dynamic model and develop the trajectory sensitivity of the electric vehicle chassis handling stability state parameters: Considering that the redistribution of the overall vehicle mass, changes in geometry, and the loading of passengers or cargo make the chassis handling stability and trajectory tracking performance of electric vehicles relatively sensitive, a nonlinear electric vehicle orientation evaluation dynamic model is established, and a trajectory sensitivity analysis method for the chassis handling stability state parameters of electric vehicles is developed using the perturbation method and the central difference method. S2. Quantitative analysis of the sensitivity of the handling stability parameters of electric vehicle chassis: Based on the nonlinear electric vehicle directional evaluation dynamic model, the key state parameters of electric vehicle chassis handling stability are quantitatively analyzed according to the developed electric vehicle chassis handling stability state parameter trajectory sensitivity analysis method. S3. Design of handling stability criteria for electric vehicle chassis: Based on the results of sensitivity quantitative analysis, and combined with the specific vehicle model, a chassis handling stability criterion is designed for electric vehicles. The chassis handling stability control of electric vehicles is then switched accordingly based on the stability criterion to ensure the chassis handling stability of the electric vehicle.

2. The method for sensitivity evaluation of the handling stability state parameters of an electric vehicle chassis according to claim 1, characterized in that, In step S1, firstly, a nonlinear electric vehicle orientation evaluation dynamic model is established. This model includes longitudinal, lateral, yaw, and rolling motions. Based on d'Alembert's principle, the derived vehicle dynamic equations are as follows: Longitudinal movement: F f =μm n g Lateral movement: Lateral and tilting motions: Where, m n Indicated as vehicle mass; F f For rolling resistance, V x V y Represented as longitudinal velocity and lateral velocity; r x r z Expressed as vehicle roll rate and yaw rate; F xij F yij This represents the longitudinal and lateral forces for each tire; F w This represents the resistance generated by tire rolling; C d It is expressed as the air drag coefficient; ρ represents the air density; A f The frontal area of ​​a vehicle when it is in motion; δ fl δ fr Indicated as left front wheel steering angle, right front wheel steering angle; a x a y Represented as longitudinal acceleration and lateral acceleration; μ represents the road adhesion coefficient; β represents the centroid sideslip angle; I x I z I xz Expressed as the yaw moment of inertia about the x-axis, the yaw moment of inertia about the z-axis, and the product of the inertia of vehicle roll and yaw; l f0 l r0 b l0 b r0 This represents the distance from the front axle to the center of gravity, the distance from the rear axle to the center of gravity, the distance from the left wheel to the center of gravity, and the distance from the right wheel to the center of gravity; φ represents the vehicle roll angle; K φ Indicates the body roll stiffness; C φ h represents the vehicle roll damping coefficient. r This indicates the height of the roll axis from the ground when the vehicle is unloaded. When the vehicle's mass changes, the inertial and geometric parameters of the electric vehicle also change. The coordinate vector of the centroid changes when an additional load is applied. The change in the coordinate vector of the centroid is: in, The change in vehicle mass due to increased load is as follows: m n =m u +m p The velocity change at the new center of mass after the change in the center of mass position and its differential form are: The equation for the vehicle body's rotational motion is obtained as follows: Among them, V, V p Represented as the velocity matrix of the vehicles before and after loading; r, Let M represent the vehicle's roll, pitch, and yaw angular velocity vectors and their antisymmetric matrices, and let M represent the matrix of external torques. During vehicle motion, the vehicle's moment of inertia and product of inertia are defined as follows: The change in the vehicle's yaw moment of inertia after loading is as follows: Assuming load m p Since it is a point load, the yaw moment of inertia is calculated as follows: Further results were obtained: Assuming the vehicle's center of gravity height remains constant, calculate the coordinates of the changed center of gravity position: Therefore, the yaw moment of inertia of an electric vehicle is calculated as follows: Meanwhile, the change in the center of mass caused by the variable load is considered; in the equation, the parameters of the tire model are calculated as follows: Among them, l f l r This is expressed as the distance between the front axle and the center of gravity, and the distance between the rear axle and the center of gravity after the vehicle is loaded; b f b r h represents the distance from the vehicle's center of gravity to the centers of the left and right wheels after loading. n Indicates the distance from the tilt axis to the ground after loading; x n y n z n This represents the coordinates of the vehicle's center of gravity after loading; L and B represent the vehicle's wheelbase and track width, respectively. The nonlinear tire model uses the Pacejka tire model. Where Y represents the longitudinal tire force F x Or lateral tire-road force F y X represents the slip ratio s or the tire slip angle α; S h and S v This is represented by the horizontal and vertical drift of the curve; when longitudinal slip occurs, the stiffness parameters are calculated as follows: in, Under the condition of longitudinal slippage, the restoring torque is readily obtained as follows: M z =M z0 (a,c,F z ) M z0 =-t×F y0 +M zr M zr =Dcos(Carctan(Bx))cosx Among them, M zr This represents the residual self-aligning torque; γ represents the tire camber angle. Secondly, the trajectory sensitivity of the electric vehicle chassis handling stability state parameter is developed and defined as follows: The observation results of the vehicle chassis handling stability state parameter estimation based on the above model are described by the variable y, and the input state parameters in the vehicle are represented by the vector X: X=[x1,x2,x3,...x n ] y i =f i (x)=f i (x1,x2,x3,...x n ) If the center value of the parameter is defined as x0, then the corresponding model output value is: y i =f i (x)=f i (x 01 +Δx1,x 02 +Δx2,x 03 +Δx3,...x 0n +Δx n ) =f i (x0+Δx)i=1,2,3...n Therefore, the change in the output of the nonlinear electric vehicle orientation evaluation dynamic model caused by the change in the guiding parameters due to external disturbances is as follows: Δy i =f i (x0+Δx)-f i (x0)i=1,2,3...n For y i Find the k-th order partial derivative at the parameter center value x0: Further truncation and solution yields the k-th order sensitivity as: Further, the solution can be developed as follows: In x i The partial derivative reflects its sensitivity as follows: Among them, S i Represented as the vehicle chassis handling stability state parameter x i Sensitivity; Considering the vehicle state parameter x i Since the units of measurement are inconsistent, they are standardized and introduced into a dimensionless variable as follows: Where σ represents the parameter x i The degree of disturbance change; Considering the complexity of the dynamic model for directional evaluation of electric vehicles, a central difference is introduced to further simplify the sensitivity evaluation of the chassis handling stability state parameters of electric vehicles, as follows: Among them, X i+0.5 With X i-0.5 The terms are differences, namely X. i+0.5 =(x1,x2,...,x i +0.5Δx i ,...,x n ) and X i-0.5 =(x1,x2,...,x i -0.5Δx i ,...,x n ); Defined at point X i+0.5 With X i-0.5 The central difference at step size Δx is as follows: Among them, X i+1 X i With X i-1 The terms are differences, namely X. i+1 =(x1,x2,...,x i +Δx i ,...,x n ), X i =(x1,x2,...,x i ,...,x n ) and X i-1 =(x1,x2,...,x i -Δx i ,...,x n ); To improve the accuracy of its vehicle state parameter sensitivity, a second-order central difference is further introduced: Meanwhile, the calculation result of the nth-order central difference is defined as follows: D n y i =D n-1 y i+0.5 -D n-1 y i-0.5 。 3. The method for sensitivity evaluation of the handling stability state parameters of an electric vehicle chassis according to claim 1, characterized in that, In step S2, the sensitivity of the electric vehicle chassis handling stability state parameters is evaluated according to the defined trajectory sensitivity analysis method, and the state variables of the vehicle model are defined as follows: x s (t)=[V x V y βr z r x φ] The vehicle load parameters for disturbance analysis are defined as follows: θ s (t)=[m p x p y p z p ] Further derivation of its state parameter sensitivity reveals typical vehicle state parameter sensitivity; Wherein, the longitudinal velocity V is defined x The sensitivity of the centroid sideslip angle β and sideslip angle φ is as follows; Defined in m p V under disturbance x The trajectory sensitivity is: Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change; The average value of its local sensitivity is defined as: Defined in x p V under disturbance x The trajectory sensitivity is: Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as: Defined in y p V under disturbance x The trajectory sensitivity is: Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change; The mean of its local sensitivity is defined as: Defined in z p V under disturbance x The trajectory sensitivity is: Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean of the local sensitivity is defined as: Defined in m p The sensitivity of the β trajectory under disturbance is: Where, m′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its mean local sensitivity is defined as: Defined in x p The sensitivity of the β trajectory under disturbance is: Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the local sensitivity is defined with the mean value as: Defined in y p The sensitivity of the β trajectory under disturbance is: Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the mean value of the local sensitivity is defined as: Defined in z p The sensitivity of the β trajectory under disturbance is: Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after perturbation, its mean local sensitivity is defined as: Defined in m p The trajectory sensitivity of the roll angle φ under disturbance conditions is: Where, m′ represents p The values ​​are shown after the perturbation change. Expressed as the trajectory sensitivity after the disturbance change; The average value of its local sensitivity is defined as: Defined in x p The trajectory sensitivity of the roll angle φ under disturbance conditions is: Where, x′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, its average local sensitivity is defined as: Defined in y p The trajectory sensitivity of the roll angle φ under disturbance conditions is: Where, y′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change; The mean of its local sensitivity is defined as: Defined in z p The trajectory sensitivity of the roll angle φ under disturbance conditions is: Where, z′ p Represented as the value after perturbation. Expressed as the trajectory sensitivity after the disturbance change, the average value of the local sensitivity is defined as:

4. The method for sensitivity evaluation of handling stability state parameters of an electric vehicle chassis according to claim 1, characterized in that, In step S3, the trajectory sensitivity definition and local sensitivity average value analysis method of the electric vehicle chassis handling stability state parameters are used for analysis, and a polynomial is used to fit them. During the analysis, the observation of the electric vehicle chassis handling stability state parameters is completed using the volumetric Kalman Array (CKF). The sensitivity of each state parameter can be evaluated and compared through analysis and observation. Typical electric vehicle chassis handling stability state parameters are evaluated for the vehicle's center of gravity sideslip angle β and load mass m. p The load longitudinal position x is most sensitive to its estimation effect. p and the lateral position of the load y p It also has some impact, the vertical position of the load z p The impact is minimal, even negligible; for the vehicle's center of gravity roll angle φ, the longitudinal position of the load x p and load mass m p The mean sensitivity values ​​of and are not significantly different, and the tilt angle is relatively sensitive to them; the lateral position of the load y p and the load perpendicular position z p The impact is relatively small and much smaller than the former two. Furthermore, based on the sensitivity analysis results, and combined with the specific vehicle model, the phase plane method is used to design the electric vehicle chassis handling stability criterion. Then, the electric vehicle chassis handling stability control is based on the stability criterion to perform corresponding switching control to ensure the chassis handling stability of the electric vehicle. The corresponding design criteria for the yaw stability of electric vehicle chassis are as follows: Oh β ≤Ω βlim 0<μ≤0.4, 0.4<μ≤0.8, 0.8<μ≤1, Here Ω βlim To obtain the boundary threshold of yaw stability of electric vehicle chassis using the phase plane method based on the sensitivity results, c1, c2, and c3 are specific vehicle constants determined by combining the phase plane method with the sensitivity evaluation results and using polynomial fitting. The corresponding design criteria for the roll stability of electric vehicle chassis are as follows: Among them, Ω φlim To obtain the boundary threshold for the roll stability of the electric vehicle chassis using the phase plane method based on sensitivity and specific vehicle models.

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