A method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle

Abstract

The present application discloses a method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle. The method takes into account the vehicle's dynamic performance and prevents the vehicle from rolling over during the path tracking process. The method comprises: establishing a front section model and a rear section model of a multi-section vehicle to ensure effective tracking of the front section and accurate tracking of the rear section; determining the driving condition through an advanced driver assistance system module based on road information acquired by a visual sensor, and determining whether the vehicle has deviated; obtaining the actual vehicle body roll angle through an unscented Kalman filter estimation module; inputting the theoretical vehicle body roll angle into a rollover condition determination module, and outputting the wheel braking force to achieve the effect of differential braking; the present invention designs a rear section trajectory error model based on a front section preview error model, and designs a rollover warning system logic flow based on a dynamic model prediction, effectively improving the vehicle driving stability and safety during the path tracking process of the two-section vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-section vehicle driving safety, and in particular to a method for preventing a rear section from rolling over during a path tracking process of a double-section vehicle. Background Art

[0002] In recent years, with the large-scale construction of infrastructure in my country, the national highway network has been rapidly expanding. Furthermore, the rise of the internet and the logistics industry has led to new demands for road transportation in my country. Compared to conventional trucks, multi-section vehicles offer advantages such as large cargo capacity, high transport speeds, safety, and flexibility. They can also meet the specific requirements of materials that are difficult or impossible to meet with other modes of transportation. Therefore, multi-section vehicles have long become a mainstream mode of transportation for road transportation in developed countries. Furthermore, in addition to road transportation, multi-section vehicles can also be used to address urban transportation issues. Although my country's development of multi-section vehicles is later than that of developed countries, recent advances in the automotive industry have led to the development of intelligent, specialized, multi-axle, and multi-purpose vehicles in China.

[0003] Because the development of multi-section vehicles in my country began relatively late and is less advanced than in developed countries, several safety issues remain. Multi-section vehicles have a much higher mass and center of gravity, resulting in poor driving stability. Furthermore, the articulated connection between the front and rear sections results in poor maneuverability at low speeds and instability at high speeds. The front and rear sections also affect each other, making it difficult for the rear section to follow the path of the front section during steering. This makes dangerous accidents such as tailspin, sideslip, and jackknifing very likely to occur during driving. Summary of the Invention

[0004] Purpose of the invention: Based on the path tracking process of a two-section vehicle, the present invention provides a control method for the stable driving of a two-section vehicle to prevent the vehicle from rolling over due to excessive speed or excessive turning angle during turning.

[0005] Technical solution: A method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle, comprising:

[0006] Step 1: Establish a front section dynamics model of a multi-section vehicle. The front section dynamics model includes the following modules:

[0007] (1) Provide braking force to the vehicle and input the driver module of the front wheel angle of the front vehicle segment;

[0008] (2) a front segment module for outputting the longitudinal velocity and yaw angular velocity of the front segment;

[0009] (3) A front segment preview error module based on a visual sensor for outputting lateral position deviation and azimuth deviation;

[0010] Step 2: Dimensionally process the lateral position deviation and azimuth deviation, perform weighted combination, and obtain a comprehensive error; input the comprehensive error into the PID controller, and output the front wheel angle of the front vehicle segment;

[0011] Step 3: Establish a rear section dynamics model of a multi-section vehicle. The rear section dynamics model includes the following modules:

[0012] (1) A rear vehicle segment module that outputs the rear vehicle longitudinal velocity, rear vehicle yaw angular velocity, and articulation angular velocity;

[0013] (2) a trajectory error module that adjusts the front wheel angle input according to the position deviation and direction error between the front and rear vehicle segments;

[0014] (3) Based on the coupling mechanism of path tracking accuracy and operational stability, a lateral safety distance module is constructed to improve the vehicle's path tracking accuracy by establishing critical values ​​for collision, instability, and comfort.

[0015] (4) a rollover condition determination module for outputting a compensatory yaw moment;

[0016] Step 4: Establish the coupling relationship between the front and rear segments;

[0017] Step 5: The preceding vehicle preview module determines whether the driving route is straight or turning by setting the LDWS module; and sets the UFK estimation module to obtain the actual vehicle roll angle by collecting the articulation angular velocity and the longitudinal velocity;

[0018] LDWS (full name "Lane Departure Warning System") lane departure warning system is a system that assists the driver by issuing an alarm to reduce traffic accidents caused by lane departure.

[0019] UKF (full name "Unscented Kalman Filter") unscented Kalman filter estimation is a combination of lossless transformation (UT) and standard Kalman filter system. Through lossless transformation, nonlinear system equations are adapted to the standard Kalman filter system under the linear assumption.

[0020] Step 6: When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as criteria to determine whether the vehicle has deviated.

[0021] Step 7: When the LDWS module determines that the path is a turning driving condition, the UFK estimation module obtains the actual body roll angle by collecting the articulation angular velocity and longitudinal velocity, and estimates the body motion state in the future time period through the rear vehicle segment module;

[0022] Step 8: Obtain the theoretical body roll angle from the rear section module, input the theoretical body roll angle and the actual body roll angle into the rollover condition determination module to determine whether a rollover condition exists. If a rollover condition exists, calculate the required compensatory yaw moment.

[0023] Step 9: The rollover control module calculates the wheel braking force based on the compensated yaw moment and feeds it back to the driver module to perform differential braking on the vehicle until the driving ends.

[0024] Preferably, the front and rear vehicle modules are both three-degree-of-freedom dynamic models, including three directions of motion: lateral, yaw, and roll. Based on the three-degree-of-freedom dynamic model of the front and rear vehicle modules and the coupling relationship between the front and rear vehicle modules, a two-section vehicle dynamic model is established, and this is achieved by the following steps:

[0025] Step 1A-1: Based on the three-degree-of-freedom dynamic equations of the front vehicle segment's lateral, yaw, and roll motions and the wheel's rotational motion, establish a front vehicle segment dynamic model, such as Figure 1 As shown:

[0026] Depend on Figure 1 It can be seen that the dynamic equation of the front wheel segment is as follows:

[0027]

[0028]

[0029]

[0030] Where, is the yaw angle of the front wheel; δ is the front wheel turning angle of the front wheel; v x1 is the longitudinal velocity of the front vehicle; v y1 is the lateral speed of the front car segment; a1 is the distance from the center of mass of the front car segment to the front wheel of the front car segment; b1 is the distance from the center of mass of the front car segment to the rear wheel of the front car segment; c1 is the distance from the front car segment to the hinge point; I z1 is the yaw moment of inertia of the front vehicle segment; F xf 、F xr is the longitudinal force of the corresponding tire; F yf 、F yr are the cornering force; F px 、F py are the longitudinal force and lateral force acting on the hinge point P respectively;

[0031] Step 1A-2: Based on the three-degree-of-freedom dynamic equations of the rear section's lateral, yaw, and roll motions and the rotational motion of the wheels, establish a rear section dynamic model, such as Figure 1 As shown:

[0032] Depend on Figure 1 It can be seen that the dynamic equation of the rear section is as follows:

[0033]

[0034] Where, is the yaw angle of the rear section; λ is the articulation angle; v x2 is the longitudinal velocity of the rear section; v y2 is the lateral speed of the rear section; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z2 is the yaw moment of inertia of the rear section; F xt is the longitudinal force of the corresponding tire; F yt are the cornering force, F px 、F py are the longitudinal force and lateral force acting on the hinge point P respectively;

[0035] Step 1A-3: The coupling relationship between the front and rear segments is as follows:

[0036]

[0037] Where, are the yaw angles of the front and rear sections respectively; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral velocities of the front and rear segments, respectively; c1 is the distance from the front segment to the hinge point; a2 is the distance from the center of mass of the rear segment to the hinge point;

[0038] Step 1A-4: Combining the formulas of Step 1A-1, Step 1A-2, and Step 1A-3 above, the seven-degree-of-freedom dynamic equation can be obtained as follows:

[0039]

[0040] in, is the state quantity of the system, u1=[δT1T2T3] T is the system input, the matrix M1 and the function f1(ξ1,u1)d are expressed as follows:

[0041]

[0042] f1(ξ1,u1)=[f 11f 12 f 13 f 14 f 15 ]T

[0043] in,

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] Where, are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral speeds of the front and rear sections respectively; a1 is the distance from the center of mass of the front section to the front wheel of the front section; b1 is the distance from the center of mass of the front section to the rear wheel of the front section; c1 is the distance from the front section to the hinge point; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z1 I is the yaw moment of inertia of the front vehicle segment; z2 is the yaw moment of inertia of the rear section; F xf 、F xr 、F xt is the longitudinal force of the corresponding tire; F yf 、F yr 、F yt are the cornering forces, m1 is the mass of the front vehicle, and m2 is the mass of the rear vehicle.

[0050] Preferably, the yaw rate and longitudinal velocity output by the front vehicle segment module are input into the preview error module, and the road curvature and preview distance are input externally. Finally, the lateral displacement deviation and lateral orientation deviation are output, and the dimensionless comprehensive error is adjusted by the PID controller to output the new wheel angle, continuously adjusting the vehicle's driving direction for lateral control;

[0051] Step 1B-1: Based on the vehicle's motion state and road information fed back by the visual sensor, input the front wheel angle in real time to make the error approach 0; construct the preview error model formula:

[0052]

[0053]

[0054] Where y e is the lateral displacement deviation from the preview point to the tangent of the center line of the desired path; ε is the angle between the vehicle center axis and the tangent of the center line of the desired path; ω r is the yaw angular velocity; v x 、v y are the horizontal and vertical speeds respectively; L is the preview distance; ρ is the road curvature;

[0055] Step 1B-2: Use the threshold method to perform dimensionless processing on the lateral displacement deviation and the directional deviation, and combine the dimensionless lateral tracking error and the directional error according to a certain weight to form a comprehensive error;

[0056] Step 1B-3: Input the comprehensive error in step 1B-2 into the PID controller, and adjust the output wheel angle through the PID controller to control the front vehicle segment dynamic model and perform front vehicle segment path tracking.

[0057] Preferably, based on the planned path of the leading segment, a trajectory error model of the trailing segment is established to compensate for the heading angle error of the trailing segment. The trajectory error model of the trailing segment is implemented by the following steps:

[0058] Step 2A-1: First, define the rear vehicle segment trajectory tracking error vector: E = [e x1 ,e y1 ,ε1,ε2] T ,

[0059] Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively;

[0060] The error equation is:

[0061]

[0062]

[0063]

[0064]

[0065] in,

[0066] Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively; ω r1and ω2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; L1 and L2 are the distances from the center of the front axle of the tractor to the center of the rear axle and the distance from the hinge point to the rear axle of the trailer respectively; d is the distance from the center of the rear axle of the tractor to the hinge point, v x1 is the longitudinal speed of the leading vehicle.

[0067] Step 2A-2: To simplify the controller, set u = [v x1 ,ω r1 ] T As the control input, the state space equation is obtained:

[0068]

[0069] in,

[0070]

[0071] Where, v x1 is the longitudinal velocity of the front vehicle; ω r1 、ω r2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections, respectively; L1 and L2 are the distance from the center of the front axle of the tractor to the center of the rear axle, and the distance from the hinge point to the rear axle of the trailer, respectively; d is the distance from the center of the rear axle of the tractor to the hinge point;

[0072] Step 2A-3: Discretize the state space equation obtained in step 2A-2 to obtain:

[0073] E(k+1)=A k,t E(k)+B k,t u(k)+Γ(k)

[0074] Among them, A k,t =I+AT s , B k,t =I+BT s , Γ k,t =ΓT s , Ts is the sampling interval;

[0075] The discretization of the state space equation is to make it easier to solve the optimal problem, and the state space equation needs to be expanded. The new state quantity is given as ξ(k|t)=[E(k|t),u(k-1|t)] T , the expanded equation is:

[0076]

[0077]

[0078] In order to reduce the errors and reduce the complexity of the model, it is necessary to add penalty terms to the state and control variables of the model, and obtain:

[0079]

[0080] stΔU min ≤ΔU t ≤ΔU max

[0081] U min ≤AΔU t +U t ≤U max

[0082] Step 2A-4: Feedback the optimal solution from step 2A-3 to the vehicle dynamics model, transmit the optimal solution to the driver module, and adjust the driving trajectories of the front and rear segments according to the real-time motion state of the vehicle, thereby forming a closed-loop control in which both the front and rear segments move along the given desired route, thereby achieving vehicle path tracking.

[0083] Preferably, the position deviation and heading angle error generated by the front and rear vehicle segments during driving are simultaneously transmitted back to the driver module, and after system adjustment, the appropriate wheel steering angle is output to ensure that the vehicle's driving route coincides with the desired route;

[0084] To ensure the accuracy of vehicle path tracking, a lateral safety distance model is established based on the visual sensor to obtain the relative direction and position information of the vehicle's lane. The lateral distance between the left and right wheels of the vehicle and the left and right lane lines is calculated. By comparing the distance with the established safety distance, it is determined whether the vehicle has deviated. The specific steps are as follows:

[0085] In step 2B, the left and right wheels of the vehicle are at a certain distance from the left and right lane lines. The lateral distance expression is:

[0086]

[0087]

[0088] Where y0 represents the vertical distance between the center of mass of the vehicle and the center line of the lane, W represents the lane width, and Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; W c Indicates vehicle width, Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; when Δy l >0, and Δy r >0, indicating that the car is driving normally in the lane; when Δyl <0 or Δy r When the value is less than 0, the vehicle deviates and the system transmits a deviation signal to the driver to remind him to take measures to prevent the vehicle from deviating from the direction.

[0089] When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as the judgment criteria to determine whether the vehicle has deviated. When the distance is less than the set threshold, it indicates that the vehicle is currently driving normally. Otherwise, the vehicle has deviated laterally. At this time, an early warning is issued to remind the driver to take appropriate remedial measures to return the vehicle to the normal driving trajectory. At the same time, the warning conditions of the lane departure warning model are set as follows:

[0090] δ>3°

[0091] L′>50cm

[0092] Where δ represents the front wheel turning angle; L′ represents the lateral distance from the center of the vehicle to the center line of the lane.

[0093] When the LDWS module determines that the vehicle is in a turning driving condition, the UKF estimation module compensates for the vehicle body state to prevent dangerous conditions such as rollover during driving. The UKF estimation module is used to predict and estimate the vehicle state. The specific steps are as follows:

[0094] Step 5A-1: The UKF estimation module obtains the actual body roll angle from the articulation angular velocity and longitudinal velocity, and uses the rear vehicle dynamics module to estimate the body motion state in the future time period;

[0095] Step 5A-2: Use the UKF estimation module to estimate the real-time vehicle motion state parameters, use the unscented transform (UT) to handle the nonlinear transfer problem of mean and covariance, and obtain the actual vehicle roll angle;

[0096] In step 6A-1, the theoretical body roll angle output by the rear section module is combined with the actual roll angle obtained in step 5 and input into the rollover condition determination module to determine whether a rollover condition has occurred. The lateral load transfer rate (LTR) is selected as the rollover determination factor, and its calculation formula is:

[0097]

[0098] Where D LTR is the LTR calculation value; F zl 、F zr are the vertical loads on the left and right wheels of the vehicle respectively;

[0099] In step 6A-2, the threshold of the absolute value of the lateral load transfer rate is set to 0.85. When a rollover condition is identified, the compensatory yaw moment required for control is calculated in combination with the vehicle's real-time motion state parameters.

[0100] In step 6A-3, the rollover control module calculates the vehicle brake pressure based on the compensation yaw moment required in step 6A-2, adjusts it using a flexible PID control algorithm, and implements it through differential braking.

[0101] Preferably, the comprehensive error output from the above steps and the required compensatory braking force are input into the driver module to remind the driver to take measures to correct the steering wheel and adjust the front wheel angle; at the same time, a certain braking force is applied to compensate for the vehicle body state to prevent the vehicle body from rolling over and causing dangerous working conditions. The early warning system takes corresponding responses according to the driving conditions until the two-stage vehicle is safely driven.

[0102] Beneficial effects: Based on the path tracking technology of two-section vehicles, the present invention divides vehicle driving into straight-line and turning driving modes through road condition identification; during straight-line driving, it determines whether the vehicle deviates from the estimated route. If deviation occurs, the front wheel angle is adjusted by output to control the front vehicle to achieve stable driving in the straight-line mode; during turning driving, the UFK estimation module can estimate the future movement state of the vehicle body by collecting data, and through comparison, it can be determined whether the rear section of the two-section vehicle has a rollover condition, and the compensation yaw torque is calculated and fed back to the driver module to perform differential braking on the vehicle to achieve the purpose of controlling the vehicle to drive stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0104] Figure 1 It is a flow chart of a multi-section vehicle anti-rollover control method.

[0105] Figure 2 This is a diagram of a multi-section vehicle monorail model;

[0106] Figure 3 It is the preview error model diagram;

[0107] Figure 4 It is a vehicle location information map;

[0108] Figure 5 It is the reference model diagram of rollover condition;

[0109] Figure 6 This is the front wheel angle optimization effect diagram;

[0110] Figure 7 This is the effect diagram of horizontal position optimization;

[0111] Figure 8 This is the rollover control LTR effect diagram; DETAILED DESCRIPTION

[0112] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0113] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0114] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0115] A method for preventing the rear section from rolling over during a two-section vehicle path tracking process, comprising:

[0116] Step 1: Establish a front section dynamics model of a multi-section vehicle. The front section dynamics model includes the following modules:

[0117] (1) Provide braking force to the vehicle and input the driver module of the front wheel angle of the front vehicle segment;

[0118] (2) a front segment module for outputting the longitudinal velocity and yaw angular velocity of the front segment; the front segment module is a three-degree-of-freedom dynamic model, including three motion directions: lateral, yaw, and roll;

[0119] (3) A front segment preview error module based on a visual sensor for outputting lateral position deviation and azimuth deviation;

[0120] Based on the three-degree-of-freedom dynamic equations of the front vehicle segment's lateral, yaw, and roll motions and the wheel's rotational motion, a front vehicle segment dynamics model is established, such as Figure 1 As shown:

[0121] Depend on Figure 1 It can be seen that the dynamic equation of the front wheel segment is as follows:

[0122]

[0123] Where, is the yaw angle of the front wheel; δ is the front wheel turning angle of the front wheel; v x1 is the longitudinal velocity of the front vehicle; v y1 is the lateral speed of the front car segment; a1 is the distance from the center of mass of the front car segment to the front wheel of the front car segment; b1 is the distance from the center of mass of the front car segment to the rear wheel of the front car segment; c1 is the distance from the front car segment to the hinge point; I z1 is the yaw moment of inertia of the front vehicle segment; F xf 、F xr is the longitudinal force of the corresponding tire; F yf 、F yr are the cornering force; F px 、F py are the longitudinal force and lateral force acting on the hinge point P, respectively, and m1 is the mass of the preceding vehicle;

[0124] Step 2: Dimensionally process the lateral position deviation and azimuth deviation, perform weighted combination, and obtain a comprehensive error; input the comprehensive error into the PID controller, and output the front wheel angle of the front vehicle segment;

[0125] Step 3: Establish a rear section dynamics model of a multi-section vehicle. The rear section dynamics model includes the following modules:

[0126] (1) a rear vehicle segment module that outputs the rear vehicle longitudinal velocity, rear vehicle yaw angular velocity, and articulation angular velocity; the rear vehicle segment module is a three-degree-of-freedom dynamic model, including three motion directions: lateral, yaw, and roll;

[0127] (2) a trajectory error module that adjusts the front wheel angle input according to the position deviation and direction error between the front and rear vehicle segments;

[0128] (3) Based on the coupling mechanism of path tracking accuracy and operational stability, a lateral safety distance module is constructed to improve the vehicle's path tracking accuracy by establishing critical values ​​for collision, instability, and comfort.

[0129] (4) a rollover condition determination module for outputting a compensatory yaw moment;

[0130] Based on the three-degree-of-freedom dynamic equations of the rear section's lateral, yaw, and roll motions and the rotational motion of the wheels, a rear section dynamics model is established, such as Figure 1 As shown:

[0131] Depend on Figure 1 It can be seen that the dynamic equation of the rear section is as follows:

[0132]

[0133] Where, is the yaw angle of the rear section; λ is the articulation angle; v x2 is the longitudinal velocity of the rear section; v y2 is the lateral speed of the rear section; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z2 is the yaw moment of inertia of the rear section; F xt is the longitudinal force of the corresponding tire; F yt are the cornering force, F px 、F py are the longitudinal force and lateral force acting on the hinge point P, respectively, and m2 is the mass of the rear vehicle;

[0134] Step 4: Establish the coupling relationship between the front and rear segments;

[0135] The coupling relationship between the front and rear segments is as follows:

[0136]

[0137] Where, are the yaw angles of the front and rear sections respectively; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral velocities of the front and rear segments, respectively; c1 is the distance from the front segment to the hinge point; a2 is the distance from the center of mass of the rear segment to the hinge point;

[0138] Combining the above formulas, the seven-degree-of-freedom dynamic equation can be obtained as follows:

[0139]

[0140] in, is the state quantity of the system, u1=[δT1T2T3] T is the system input, the matrix M1 and the function f1(ξ1,u1)d are expressed as follows:

[0141]

[0142] f1(ξ1,u1)=[f 11 f 12 f 13 f 14 f 15 ]T

[0143] in,

[0144]

[0145]

[0146]

[0147]

[0148]

[0149] Where, are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral speeds of the front and rear sections respectively; a1 is the distance from the center of mass of the front section to the front wheel of the front section; b1 is the distance from the center of mass of the front section to the rear wheel of the front section; c1 is the distance from the front section to the hinge point; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z1 I is the yaw moment of inertia of the front vehicle segment; z2 is the yaw moment of inertia of the rear section; F xf 、F xr 、F xt is the longitudinal force of the corresponding tire; F yf 、F yr 、F yt are the cornering forces, m1 is the mass of the front vehicle, and m2 is the mass of the rear vehicle.

[0150] Step 5: The preceding vehicle preview module determines whether the driving route is straight or turning by setting the LDWS module; and sets the UKF estimation module to obtain the actual vehicle body roll angle by collecting the articulation angular velocity and the longitudinal velocity;

[0151] Step 6: When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as criteria to determine whether the vehicle has deviated.

[0152] When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as the judgment criteria to determine whether the vehicle has deviated. When the distance is less than the set threshold, it indicates that the vehicle is currently driving normally. Otherwise, the vehicle has deviated laterally. At this time, an early warning is issued to remind the driver to take appropriate remedial measures to return the vehicle to the normal driving trajectory. At the same time, the warning conditions of the lane departure warning model are set as follows:

[0153] δ>3°

[0154] L′>50cm

[0155] Where δ represents the front wheel turning angle; L′ represents the lateral distance from the center of the vehicle to the center line of the lane.

[0156] The yaw rate and longitudinal velocity output by the front vehicle segment module are input into the preview error module, and the road curvature and preview distance are input externally. Finally, the lateral displacement deviation and lateral orientation deviation are output. The dimensionless comprehensive error is adjusted by the PID controller and the new wheel angle is output. The driving direction of the vehicle is continuously adjusted to perform lateral control.

[0157] According to the vehicle's motion state and road information fed back by the visual sensor, the front wheel angle is input in real time to make the error approach 0; the preview error model formula is constructed:

[0158]

[0159]

[0160] Where y e is the lateral displacement deviation from the preview point to the tangent of the center line of the desired path; ε is the angle between the vehicle center axis and the tangent of the center line of the desired path; ω r is the yaw angular velocity; v x 、v y are the horizontal and vertical speeds respectively; L is the preview distance; ρ is the road curvature;

[0161] The threshold method is used to non-dimensionalize the lateral displacement deviation and directional deviation, and the non-dimensionalized lateral tracking error and directional error are combined into a comprehensive error according to a certain weight; the obtained comprehensive error is input into the PID controller, and the PID controller adjusts the output wheel angle to control the dynamic model of the front vehicle segment and perform front vehicle segment path tracking.

[0162] Step 7: When the LDWS module determines that the path is a turning driving condition, the UKF estimation module first generates a trajectory error model of the rear vehicle segment based on the planned road of the front vehicle segment for the path tracking of the rear vehicle segment.

[0163] Based on the planned path of the leading segment, a trajectory error model of the trailing segment is established to compensate for the heading angle error of the trailing segment. The trajectory error model of the trailing segment is implemented through the following steps:

[0164] First, define the rear vehicle segment trajectory tracking error vector: E = [e x1 ,e y1 ,ε1,ε2] T ,

[0165] Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively;

[0166] The error equation is:

[0167]

[0168]

[0169]

[0170]

[0171] in,

[0172] Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively; ω r1 、ω r2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; L1 and L2 are the distance from the center of the front axle of the tractor to the center of the rear axle and the distance from the hinge point to the rear axle of the trailer respectively; d is the distance from the center of the rear axle of the tractor to the hinge point, v x1 is the longitudinal speed of the leading vehicle.

[0173] Step 2A-2: To simplify the controller, set u = [v x1 ,ω r1 ] T As the control input, the state space equation is obtained:

[0174]

[0175] in,

[0176]

[0177] Where, vx1 is the longitudinal velocity of the front vehicle; ω r1 、ω r2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections respectively; L1 and L2 are the distance from the center of the front axle to the center of the rear axle of the tractor and the distance from the hinge point to the rear axle of the trailer respectively; d is the distance from the center of the rear axle of the tractor to the hinge point.

[0178] Step 2A-3: Discretize the state space equation obtained in step 2A-2 to obtain:

[0179] E(k+1)=A k,t E(k)+B k,t u(k)+Γ(k)

[0180] Among them, A k,t =I+AT s , B k,t =I+BT s , Γ k,t =ΓT s , Ts is the sampling interval;

[0181] The discretization of the state space equation is to make it easier to solve the optimal problem, and the state space equation needs to be expanded. The new state quantity is given as ξ(k|t)=[E(k|t),u(k-1|t)] T , the expanded equation is:

[0182]

[0183]

[0184] In order to reduce the errors and reduce the complexity of the model, it is necessary to add penalty terms to the state and control variables of the model, and obtain:

[0185]

[0186] stΔU min ≤ΔU t ≤ΔU max

[0187] U min ≤AΔU t +U t ≤U max

[0188] Step 2A-4: Feedback the optimal solution from step 2A-3 to the vehicle dynamics model, transmit the optimal solution to the driver module, and adjust the driving trajectories of the front and rear segments according to the real-time motion state of the vehicle, thereby forming a closed-loop control in which both the front and rear segments move along the given desired route, thereby achieving vehicle path tracking.

[0189] The position deviation and heading angle error generated by the front and rear vehicle segments during driving are simultaneously transmitted back to the driver module. After system adjustment, the appropriate wheel steering angle is output to ensure that the vehicle's driving route coincides with the desired route.

[0190] To ensure vehicle path tracking accuracy, a lateral safety distance model is established based on the visual sensor. This model obtains the relative direction and position of the vehicle's lane. It also calculates the lateral distance between the vehicle's left and right wheels and the left and right lane lines. By comparing this distance with the established safety distance, it determines whether the vehicle has deviated. The specific steps are as follows:

[0191] Depend on Figure 4 The position relationship of the left and right wheels of the vehicle relative to the left and right lane lines is obtained as follows:

[0192]

[0193] Where y0 represents the vertical distance between the center of mass of the vehicle and the center line of the lane, W represents the lane width, and Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; W c Indicates vehicle width, Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; when Δy l >0, and Δy r >0, indicating that the car is driving normally in the lane; when Δy l <0 or Δy r When the value is less than 0, the vehicle deviates and the system transmits a deviation signal to the driver to remind him to take measures to prevent the vehicle from deviating from the direction.

[0194] By collecting the articulation angular velocity and longitudinal velocity, the actual body roll angle is obtained, and the body motion state in the future time period is estimated through the rear vehicle segment module;

[0195] When the LDWS module determines that the vehicle is in a turning driving condition, the UKF estimation module compensates for the vehicle body state to prevent dangerous conditions such as rollover during driving. The UKF estimation module is used to predict and estimate the vehicle state. The specific steps are as follows:

[0196] The UKF estimation module obtains the actual body roll angle through the articulation angular velocity and longitudinal velocity, and estimates the body motion state in the future time period through the rear vehicle dynamics module;

[0197] The UKF estimation module is used to estimate the real-time vehicle motion state parameters, and the unscented transform (UT) is used to handle the nonlinear transfer problem of mean and covariance to obtain the actual vehicle body roll angle.

[0198] Step 8: Obtain the theoretical body roll angle from the rear section module, input the theoretical body roll angle and the actual body roll angle into the rollover condition determination module to determine whether a rollover condition exists. If a rollover condition exists, calculate the required compensatory yaw moment.

[0199] The theoretical body roll angle output by the rear section module, combined with the actual roll angle obtained in step 5, is input into the rollover condition determination module to determine whether a rollover condition has occurred. The lateral load transfer rate (LTR) is selected as the rollover determination factor, and its calculation formula is:

[0200]

[0201] Where D LTR is the LTR calculation value; F zl 、F zr are the vertical loads on the left and right wheels of the vehicle respectively;

[0202] The threshold for the absolute value of the lateral load transfer rate is selected as 0.85. When a rollover condition is identified, the compensatory yaw torque required for control is calculated in combination with the vehicle's real-time motion state parameters. The rollover control module calculates the vehicle's brake pressure based on the required compensatory yaw torque, adjusts it using a flexible PID control algorithm, and achieves the purpose of controlling vehicle stable driving through differential braking.

[0203] Step 9: The combined error output from the above steps and the required compensatory braking force are input into the driver module to remind the driver to take measures to correct the steering wheel and adjust the front wheel angle; at the same time, differential braking is performed on the vehicle to compensate for the body state and prevent the body from rolling over and causing dangerous conditions. The warning system takes appropriate responses based on the driving conditions until the two-stage vehicle is safely driven.

[0204] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0205] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle, characterized in that: include: Step 1: Establish a front section dynamics model of a multi-section vehicle. The front section dynamics model includes the following modules: (1) Provide braking force to the vehicle and input the driver module of the front wheel angle of the front vehicle segment; (2) a front segment module for outputting the longitudinal velocity and yaw angular velocity of the front segment; (3) A front segment preview error module based on a visual sensor for outputting lateral position deviation and azimuth deviation; Step 2: Dimensionally process the lateral position deviation and azimuth deviation, perform weighted combination, and obtain a comprehensive error; input the comprehensive error into the PID controller, and output the front wheel angle of the front vehicle segment; Step 3: Establish a rear section dynamics model of a multi-section vehicle. The rear section dynamics model includes the following modules: (1) A rear vehicle segment module that outputs the rear vehicle longitudinal velocity, rear vehicle yaw angular velocity, and articulation angular velocity; (2) a trajectory error module that adjusts the front wheel angle input according to the position deviation and direction error between the front and rear vehicle segments; (3) Based on the coupling mechanism of path tracking accuracy and operational stability, a lateral safety distance module is constructed to improve the vehicle's path tracking accuracy by establishing critical values ​​for collision, instability, and comfort. (4) a rollover condition determination module for outputting a compensatory yaw moment; Step 4: Establish the coupling relationship between the front and rear segments; Step 5: The preceding vehicle preview module determines whether the driving route is straight or turning by setting the LDWS module; and sets the UKF unscented Kalman filter estimation module to obtain the actual vehicle body roll angle by collecting the articulation angular velocity and longitudinal velocity; Step 6: When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as criteria to determine whether the vehicle has deviated. Step 7: When the LDWS module determines that the path is a turning driving condition, the UKF unscented Kalman filter estimation module obtains the actual body roll angle by collecting the articulation angular velocity and longitudinal velocity, and estimates the body motion state in the future time period through the rear vehicle segment module; Step 8: Obtain the theoretical body roll angle from the rear section module, input the theoretical body roll angle and the actual body roll angle into the rollover condition determination module to determine whether a rollover condition exists. If a rollover condition exists, calculate the required compensatory yaw moment. Step 9: The rollover control module calculates the wheel braking force based on the compensated yaw moment and feeds it back to the driver module to perform differential braking on the vehicle until the driving ends.

2. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, characterized in that: The front and rear vehicle modules are both three-degree-of-freedom dynamic models, including the three directions of motion: lateral, yaw, and roll. Based on the three-degree-of-freedom dynamic models of the front and rear vehicle modules and the coupling relationship between the front and rear vehicle modules, a two-section vehicle dynamic model is established and implemented through the following steps: Step 1A-1: Based on the three-degree-of-freedom dynamic equations for the front segment's lateral, yaw, and roll motions, as well as the rotational motion of the wheels, establish a front segment dynamic model. The front segment dynamic equations are as follows: Where, is the yaw angle of the front wheel; δ is the front wheel turning angle of the front wheel; v x1 is the longitudinal velocity of the front vehicle; v y1 is the lateral speed of the front car segment; a1 is the distance from the center of mass of the front car segment to the front wheel of the front car segment; b1 is the distance from the center of mass of the front car segment to the rear wheel of the front car segment; c1 is the distance from the front car segment to the hinge point; I z1 is the yaw moment of inertia of the front vehicle segment; F xf 、F xr is the longitudinal force of the corresponding tire; F yf 、F yr are the cornering force; F px 、F py are the longitudinal force and lateral force acting on the hinge point P, respectively, and m1 is the mass of the preceding vehicle; Step 1A-2: Based on the three-degree-of-freedom dynamic equations of the rear section's lateral, yaw, and roll motions and the rotational motion of the wheels, establish a rear section dynamic model. The rear section dynamic equations are as follows: Where, is the yaw angle of the rear section; λ is the articulation angle; v x2 is the longitudinal velocity of the rear section; v y2 is the lateral speed of the rear section; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z2 is the yaw moment of inertia of the rear section; F xt is the longitudinal force of the corresponding tire; F yt are the cornering force, F px 、F py are the longitudinal force and lateral force acting on the hinge point P, respectively, and m2 is the mass of the rear vehicle; Step 1A-3: The coupling relationship between the front and rear segments is as follows: Where, are the yaw angles of the front and rear sections respectively; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral velocities of the front and rear segments, respectively; c1 is the distance from the front segment to the hinge point; a2 is the distance from the center of mass of the rear segment to the hinge point; Step 1A-4: Combining the formulas of Step 1A-1, Step 1A-2, and Step 1A-3 above, the seven-degree-of-freedom dynamic equation can be obtained as follows: in, is the state quantity of the system, u1=[δT1T2T3] T is the system input, the matrix M1 and the function f1(ξ1,u1)d are expressed as follows: f1(ξ1,u1)=[f 11 f 12 f 13 f 14 f 15 ]T in, Where, are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; λ is the articulation angle; v x1 、v x2 are the longitudinal speeds of the front and rear segments respectively; v y1 、v y2 are the lateral speeds of the front and rear sections respectively; a1 is the distance from the center of mass of the front section to the front wheel of the front section; b1 is the distance from the center of mass of the front section to the rear wheel of the front section; c1 is the distance from the front section to the hinge point; a2 is the distance from the center of mass of the rear section to the hinge point; b2 is the distance from the center of mass of the rear section to the rear wheel of the rear section; I z1 I is the yaw moment of inertia of the front vehicle segment; z2 is the yaw moment of inertia of the rear section; F xf 、F xr 、F xt is the longitudinal force of the corresponding tire; F yf 、F yr 、F yt are the cornering forces, m1 is the mass of the front vehicle, and m2 is the mass of the rear vehicle.

3. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, characterized in that: The yaw rate and longitudinal velocity output by the front vehicle segment module are input into the preview error module, and the road curvature and preview distance are input externally. Finally, the lateral displacement deviation and lateral orientation deviation are output. The dimensionless comprehensive error is adjusted by the PID controller and the new wheel angle is output. The driving direction of the vehicle is continuously adjusted to perform lateral control. Step 1B-1: Based on the vehicle's motion state and road information fed back by the visual sensor, input the front wheel angle in real time to make the error approach 0; construct the preview error model formula: Where y e is the lateral displacement deviation from the preview point to the tangent of the center line of the desired path; ε is the angle between the vehicle center axis and the tangent of the center line of the desired path; ω r is the yaw angular velocity; v x 、v y are the horizontal and vertical speeds respectively; L is the preview distance; ρ is the road curvature; Step 1B-2: Use the threshold method to perform dimensionless processing on the lateral displacement deviation and the directional deviation, and combine the dimensionless lateral tracking error and the directional error according to a certain weight to form a comprehensive error; Step 1B-3: Input the comprehensive error in step 1B-2 into the PID controller, and adjust the output wheel angle through the PID controller to control the front vehicle segment dynamic model and perform front vehicle segment path tracking.

4. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, characterized in that: Based on the planned path of the leading segment, a trajectory error model of the trailing segment is established to compensate for the heading angle error of the trailing segment. The trajectory error model of the trailing segment is implemented through the following steps: Step 2A-1: First, define the rear vehicle segment trajectory tracking error vector: E = [e x1 ,e y1 ,ε1,ε2] T , Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively; The error equation is: in, Where, e x1 、e y1 They represent the longitudinal and lateral position deviations of the center of mass of the front segment respectively; ε1 and ε2 represent the heading angle errors of the front segment and the rear segment respectively; ω r1 、ω r2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections respectively; δ is the front wheel turning angle of the front section; L1 and L2 are the distances from the center of the front axle of the tractor to the center of the rear axle and the distance from the hinge point to the rear axle of the trailer respectively; d is the distance from the center of the rear axle of the tractor to the hinge point, v x1 is the longitudinal speed of the leading vehicle; Step 2A-2: To simplify the controller, set u = [v x1 ,ω r1 ] T As the control input, the state space equation is obtained: in, Where, v x1 is the longitudinal velocity of the front vehicle; ω r1 、ω r2 are the yaw angular velocities of the front and rear segments respectively; are the yaw angles of the front and rear sections, respectively; L1 and L2 are the distance from the center of the front axle of the tractor to the center of the rear axle, and the distance from the hinge point to the rear axle of the trailer, respectively; d is the distance from the center of the rear axle of the tractor to the hinge point; Step 2A-3: Discretize the state space equation obtained in step 2A-2 to obtain: E(k+1)=A k,t E(k)+B k,t u(k)+Γ(k) Among them, A k,t =I+AT s , B k,t =I+BT s , Γ k,t =ΓT s , Ts is the sampling interval; The discretization of the state space equation is to make it easier to solve the optimal problem, and the state space equation needs to be expanded. The new state quantity is given as ξ(k|t)=[E(k|t),u(k-1|t)] T , the expanded equation is: In order to reduce the errors and reduce the complexity of the model, it is necessary to add penalty terms to the state and control variables of the model, and obtain: stΔU min ≤ΔU t ≤ΔU max IN min ≤AΔU t +U t ≤U max Step 2A-4: Feedback the optimal solution from step 2A-3 to the vehicle dynamics model, transmit the optimal solution to the driver module, and adjust the driving trajectories of the front and rear segments according to the real-time motion state of the vehicle, thereby forming a closed-loop control in which both the front and rear segments move along the given desired route, thereby achieving vehicle path tracking.

5. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 4, characterized in that: The position deviation and heading angle error generated by the front and rear vehicle segments during driving are simultaneously transmitted back to the driver module. After system adjustment, the appropriate wheel steering angle is output to ensure that the vehicle's driving route coincides with the desired route. A lateral safety distance model is established based on the visual sensor to obtain the relative direction and position information of the vehicle's lane. The lateral distance between the left and right wheels of the vehicle and the left and right lane lines is calculated. By comparing this with the established safety distance, it is determined whether the vehicle has deviated. The specific steps are as follows: In step 2B, the left and right wheels of the vehicle are at a certain distance from the left and right lane lines. The lateral distance expression is: Where y0 represents the vertical distance between the center of mass of the vehicle and the center line of the lane, W represents the lane width, and Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; W c Indicates vehicle width, Δy l , Δy r are the distances between the left and right wheels and the left and right lane lines respectively; when Δy l >0, and Δy r >0, indicating that the car is driving normally in the lane; when Δy l <0 or Δy r When the value is less than 0, the vehicle deviates and the system transmits a deviation signal to the driver to remind him to take measures to prevent the vehicle from deviating from the direction.

6. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, characterized in that: When the LDWS module determines that the vehicle is in a straight-line driving condition, it calculates the lateral displacement deviation between the vehicle's articulation center point and the lane centerline, and uses the lateral displacement deviation and the front wheel angle as the judgment criteria to determine whether the vehicle has deviated. When the distance is less than the set threshold, it indicates that the vehicle is currently driving normally. Otherwise, the vehicle has deviated laterally. At this time, an early warning is issued to remind the driver to take appropriate remedial measures to return the vehicle to the normal driving trajectory. At the same time, the warning conditions of the lane departure warning model are set as follows: δ>3° L′>50cm Where δ represents the front wheel turning angle; L′ represents the lateral distance from the center of the vehicle to the center line of the lane.

7. The method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, characterized in that: When the LDWS module determines that the vehicle is in a turning driving condition, the UKF estimation module compensates for the vehicle body state to prevent the vehicle from rolling over during driving. The specific steps are as follows: Step 5A-1: The UKF estimation module obtains the actual body roll angle from the articulation angular velocity and longitudinal velocity, and uses the rear vehicle dynamics module to estimate the body motion state in the future time period; Step 5A-2: Use the UKF estimation module to estimate the real-time vehicle motion state parameters, use the unscented transform (UT) to handle the nonlinear transfer problem of mean and covariance, and obtain the actual vehicle roll angle; In step 6A-1, the theoretical body roll angle output by the rear section module is combined with the actual roll angle obtained in step 5 and input into the rollover condition determination module to determine whether a rollover condition has occurred. The lateral load transfer rate (LTR) is selected as the rollover determination factor, and its calculation formula is: Where D LTR is the LTR calculation value; F zl 、F zr are the vertical loads on the left and right wheels of the vehicle respectively; In step 6A-2, the threshold of the absolute value of the lateral load transfer rate is set to 0.

85. When a rollover condition is identified, the compensatory yaw moment required for control is calculated in combination with the vehicle's real-time motion state parameters. In step 6A-3, the rollover control module calculates the vehicle brake pressure based on the compensation yaw moment required in step 6A-2, adjusts it using a flexible PID control algorithm, and implements it through differential braking.

8. According to the method for preventing the rear section from rolling over during the path tracking process of a two-section vehicle according to claim 1, the comprehensive error output from step 2 and the required compensatory braking force are input into the driver module to remind the driver to take measures to correct the steering wheel and adjust the front wheel angle; at the same time, a certain braking force is applied to compensate for the vehicle body state to prevent the vehicle body from rolling over and causing dangerous conditions. The early warning system takes appropriate responses according to the driving conditions until the two-section vehicle is safely driven.

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