A semi-trailer vehicle automatic parking control method combining feedforward and feedback

Abstract

The application discloses a semi-trailer vehicle automatic parking control method combining feedforward and feedback, establishes a semi-trailer vehicle kinematic model, calculates feedforward front wheel steering angle by using track point curvature information and actual trailer turning angle; based on pure tracking control thought, combines track point information, trailer heading angle and rear axle center coordinate information, carries out parking motion planning, and then obtains target trailer turning angle; by Taylor series expansion on the nonlinear kinematic model, an approximate linear model describing trailer turning angle change is obtained, and then a feedback controller is designed; based on the tracking effect of semi-trailer vehicle parking control, the feedback front wheel steering angle and the feedforward front wheel steering angle are dynamically weighted to obtain the total front wheel steering angle; finally, the mapping relationship between the front wheel steering angle and the steering wheel steering angle is used to obtain the actual steering wheel steering angle required by parking control; the parking control method has clear structure, is convenient to debug, has strong universality, and can meet the actual engineering application requirements of the semi-trailer vehicle.

Description

Technical Field

[0001] This invention belongs to the field of autonomous driving technology, and relates to autonomous driving parking control, specifically to an automatic parking control method for semi-trailer vehicles that combines feedforward and feedback. Background Technology

[0002] The industrial application of autonomous driving technology in commercial vehicles can help companies improve operational efficiency, reduce production costs, and minimize safety accidents. Compared to single-unit vehicles, semi-trailers have a greater carrying capacity and can generate greater economic benefits in transportation. Therefore, the commercial value of autonomous semi-trailers in scenarios such as port and factory transshipment and long-haul logistics is gradually being explored.

[0003] To ensure timely operation, semi-trailer trucks need to be able to park stably and accurately in the target storage location when loading and unloading at the station. Because the parking control of semi-trailer trucks is subject to nonholonomic constraints and has complex nonlinear characteristics, it presents a greater challenge than driving control. Clearly, conventional state feedback control methods based on position and heading errors are insufficient for parking control of semi-trailer trucks. Summary of the Invention

[0004] To address the aforementioned problems, the main objective of this invention is to design an automatic parking control method for semi-trailer vehicles that combines feedforward and feedback, thereby improving the accuracy and stability of parking control for autonomous semi-trailer vehicles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An automatic parking control method for semi-trailer vehicles that combines feedforward and feedback, the method includes two parts of calculation: the calculation of the feedforward front wheel angle and the calculation of the feedback front wheel angle.

[0007] The calculation of the feedforward front wheel angle involves receiving the trajectory information and vehicle position information of the autonomous semi-trailer, constructing a kinematic model of the semi-trailer, and calculating the feedforward front wheel angle.

[0008] The calculation of the feedback front wheel angle involves receiving trajectory and vehicle position information from the autonomous semi-trailer, performing parking control motion planning, and calculating the target trailer angle for tracking the target trajectory based on the parking motion planning. A feedback controller for tracking the target trailer angle is then designed, and the feedback front wheel angle is calculated. The feedforward front wheel angle and the feedback front wheel angle are dynamically weighted to obtain the total front wheel angle, which is then converted into the steering wheel angle required for parking control, thus realizing the parking control of the semi-trailer.

[0009] As a further description of the present invention, realizing parking control of a semi-trailer vehicle includes the following steps:

[0010] Step 1: Planning and location information reception;

[0011] It receives trajectory information from the autonomous semi-trailer planning module and vehicle location information from the positioning module, and uses them as input information.

[0012] Step 2: Calculate the feedforward control quantity;

[0013] A kinematic model of a semi-trailer vehicle is established. The kinematic model of the semi-trailer vehicle is a nonlinear model. The feedforward front wheel angle is calculated using the trajectory information and vehicle position information input in step 1.

[0014] Step 3: Parking control motion planning;

[0015] Based on the pure tracking control algorithm, combined with the trajectory information and vehicle position information input in step 1, parking motion planning is carried out based on the pre-aiming distance parameter design.

[0016] Step 4: Calculate the target trailer's turning angle;

[0017] Combining the trailer rear axle center motion radius calculated from parking motion planning and vehicle model parameters, the target trailer turning angle for tracking the target trajectory is calculated based on steady-state motion geometry.

[0018] Step 5: Calculate the feedback control quantity;

[0019] By performing Taylor series expansion on the nonlinear kinematic model of the semi-trailer, an approximate linear model describing the change in trailer angle is obtained. A feedback controller for tracking the target trailer angle is designed, and the feedback front wheel angle is calculated.

[0020] Step 6: Dynamic weighting of feedforward and feedback;

[0021] Based on the parking control tracking effect, the feedback front wheel angle and the feedforward front wheel angle calculated by the feedback controller are dynamically weighted to obtain the total front wheel angle;

[0022] By utilizing the mapping relationship between the front wheel steering angle and the steering wheel angle of the semi-trailer, the actual steering wheel angle required for parking control is obtained, and the actual required steering wheel angle is transmitted to the steering system of the semi-trailer.

[0023] As a further description of the present invention, in step 1, the trajectory information includes the coordinates of the trajectory point, the curvature information of the trajectory point, and the target heading, and the vehicle position information includes the coordinates of the rear axle center of the trailer, the actual trailer turning angle, and the trailer attitude angle.

[0024] As a further description of the present invention, in step 2, the input for the calculation of the feedforward control quantity is the curvature information of the trajectory points issued by the planning module and the actual trailer turning angle issued by the positioning module, and the output is the feedforward front wheel turning angle.

[0025] As a further description of the present invention, in step 2, the kinematic model of the semi-trailer vehicle includes two parts: the tractor and the trailer, and is a nonlinear kinematic model with four degrees of freedom: longitudinal motion of the trailer rear axle, lateral motion of the trailer rear axle, trailer rotation, and rotation of the tractor relative to the trailer.

[0026] As a further description of the present invention, in step 3, the inputs to the parking control motion planning are the coordinates of the trajectory points issued by the planning module, the target heading, the trailer attitude angle issued by the positioning module, and the coordinates of the trailer rear axle center. The output is the motion planning radius of the trailer rear axle center used to track the target trajectory points.

[0027] As a further description of the present invention, in step 4, the input for calculating the target trailer turning angle is the motion planning radius of the trailer rear axle center and the kinematic model parameters of the semi-trailer obtained in step 3, and the output is the target trailer turning angle used for the design of the feedback controller.

[0028] As a further description of the present invention, in step 5, the input for the calculation of the feedback control quantity is the target trailer turning angle obtained in step 4 and the actual trailer turning angle issued by the positioning module, and the output is the feedback front wheel turning angle.

[0029] As a further description of the present invention, in step 6, the input of the feedforward and feedback dynamic weighted system is the feedforward front wheel angle obtained in step 2 and the feedback front wheel angle and trailer angle error obtained in step 5, and the output is the steering wheel angle required for the automatic parking control of the semi-trailer vehicle.

[0030] Compared with the prior art, the technical advantages of the present invention are as follows:

[0031] This invention provides an automatic parking control method for semi-trailer vehicles that combines feedforward and feedback. By receiving planning and positioning information, calculating feedforward control quantities, planning parking control motion, calculating the target trailer turning angle, calculating feedback control quantities, and coordinating dynamic weighting of feedforward and feedback, it not only considers following the curvature of the reference trajectory, but also eliminates position and heading errors by tracking the target trailer turning angle. In addition, based on the pure tracking control concept, the tracking of position and heading errors is transformed into tracking of the target trailer turning angle, ensuring the stability of the parking motion. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall process of the automatic parking control method of the present invention;

[0033] Figure 2 This is a schematic diagram of the kinematic model of the semi-trailer vehicle in this invention;

[0034] Figure 3 This is a schematic diagram of the parking control and tracking model for semi-trailer vehicles according to the present invention. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings:

[0036] In one embodiment of the present invention, an automatic parking control method for semi-trailers combining feedforward and feedback is disclosed. This method considers both following the curvature of the reference trajectory and eliminating position and heading errors by tracking the turning angle of the target trailer. This embodiment transforms the tracking of position and heading errors into tracking the turning angle of the target trailer based on a pure tracking control concept, thus ensuring the stability of the parking motion.

[0037] Specifically, in this embodiment, refer to Figure 1-3 As shown, the method includes two calculations: the calculation of the feedforward front wheel angle and the calculation of the feedback front wheel angle. The feedforward front wheel angle calculation involves receiving trajectory and position information from the autonomous semi-trailer vehicle, constructing a kinematic model of the semi-trailer vehicle, and calculating the feedforward front wheel angle. The feedback front wheel angle calculation involves receiving trajectory and position information from the autonomous semi-trailer vehicle, performing parking control motion planning, calculating the target trailer angle for tracking the target trajectory based on the parking motion planning, designing a feedback controller for tracking the target trailer angle, and calculating the feedback front wheel angle. The feedforward and feedback front wheel angles are dynamically weighted to obtain the total front wheel angle, which is then converted into the steering wheel angle required for parking control, thus achieving parking control of the semi-trailer vehicle.

[0038] More specifically, this embodiment mainly includes: receiving planning and positioning information, calculating feedforward control quantities, planning parking control motion, calculating the target trailer turning angle, calculating feedback control quantities, and dynamically weighting feedforward and feedback; the specific steps are disclosed as follows:

[0039] Step 1: Planning and location information reception;

[0040] It receives trajectory information from the autonomous semi-trailer planning module and vehicle location information from the positioning module, and uses them as input information.

[0041] Step 2: Calculate the feedforward control quantity;

[0042] A kinematic model of a semi-trailer vehicle is established. The kinematic model of the semi-trailer vehicle is a nonlinear model. The feedforward front wheel angle is calculated using the trajectory information and vehicle position information input in step 1.

[0043] Step 3: Parking control motion planning;

[0044] Based on the pure tracking control algorithm, combined with the trajectory information and vehicle position information input in step 1, parking motion planning is carried out based on the pre-aiming distance parameter design.

[0045] Step 4: Calculate the target trailer's turning angle;

[0046] Combining the trailer rear axle center motion radius calculated by parking motion planning and the kinematic model parameters of the semi-trailer, the target trailer turning angle for tracking the target trajectory is calculated based on the steady-state motion geometric relationship.

[0047] Step 5: Calculate the feedback control quantity;

[0048] By performing Taylor series expansion on the nonlinear kinematic model of the semi-trailer, an approximate linear model describing the change in trailer angle is obtained. A feedback controller for tracking the target trailer angle is designed, and the feedback front wheel angle is calculated.

[0049] Step 6: Dynamic weighting of feedforward and feedback;

[0050] Based on the parking control tracking effect, the feedback front wheel angle and feedforward front wheel angle calculated by the feedback controller are dynamically weighted to obtain the total front wheel angle; using the mapping relationship between the front wheel angle and the steering wheel angle of the semi-trailer, the steering wheel angle actually required for parking control is obtained, and the actual required steering wheel angle is transmitted to the steering system of the semi-trailer.

[0051] The aforementioned disclosed automatic parking control method for semi-trailer vehicles uses the information received from planning and positioning as input. Specifically, in step 1, the trajectory information includes the coordinates of the trajectory points, the curvature information of the trajectory points, and the target heading; the vehicle position information includes the coordinates of the rear axle center of the trailer, the actual trailer turning angle, and the trailer attitude angle.

[0052] The aforementioned calculations of feedforward control quantities, parking control motion planning, target trailer turning angle calculation, feedback control quantities, and dynamic weighting of feedforward and feedback are the main steps that contribute to the outstanding technical effects of this embodiment. Specifically, this embodiment, taking an autonomous semi-trailer vehicle as an example, details the specific implementation process of the overall architecture of this embodiment as follows:

[0053] In step 2, the feedforward control quantity is calculated as follows: Based on the established kinematic model of the semi-trailer, the feedforward front wheel angle is calculated using the trajectory point curvature information issued by the planning module and the actual trailer turning angle. Specifically, the inputs to the feedforward control quantity calculation are the trajectory point curvature information issued by the planning module and the actual trailer turning angle issued by the positioning module, and the output is the feedforward front wheel angle. The kinematic model of the semi-trailer used for the feedforward control quantity calculation includes two parts: the tractor and the trailer. It is a nonlinear kinematic model that considers four degrees of freedom: longitudinal motion of the trailer rear axle, lateral motion of the trailer rear axle, trailer rotation (heading angle), and tractor rotation relative to the trailer (trailer turning angle).

[0054] Specifically, in this embodiment, the kinematic model of the semi-trailer vehicle is as follows: Figure 2 As shown, (X,Y) is a Cartesian coordinate system representing the vehicle's position. O1 is the center of the tractor's rear axle, O2 is the center of the trailer's rear axle, and v is the velocity of the tractor at point O1. θ1 is the angle between the tractor and the X-axis, called the tractor's attitude angle. θ2 is the angle between the trailer and the X-axis, called the trailer's attitude angle. This is the angle between the tractor and the trailer, i.e., the trailer turning angle, with counterclockwise being positive. δ f L1 is the front wheel turning angle of the tractor, L2 is the front and rear wheelbase of the tractor, H is the articulation point between the tractor and the trailer, and M1 is the distance from the articulation point to the rear axle of the tractor.

[0055] In this embodiment, when the semi-trailer is operating under relatively ideal conditions, the kinematic differential equations are derived:

[0056]

[0057]

[0058]

[0059] It should be noted that for the above-mentioned semi-trailer to operate under ideal conditions, the following conditions must be met: ① The semi-trailer is always operating on a flat road surface; ② The tractor providing traction moves at a constant speed, the speed is slow enough, and the drive wheels do not slip.

[0060] refer to Figure 2 Combining equations (1) and (2), the motion of hinge point H in the X and Y directions can be obtained as follows:

[0061]

[0062]

[0063] Combining equations (4) and (5), the motion of the trailer (aligned with the articulation point) along the O2H direction can be obtained as follows:

[0064]

[0065] According to equation (6), the motion of the trailer in the X and Y directions can be obtained as follows:

[0066]

[0067]

[0068] refer to Figure 2 Combining equations (4) and (5), the motion of hinge point H along the direction perpendicular to O2H can be obtained as follows:

[0069]

[0070] According to equation (9), the rotational motion of the trailer can be obtained as follows:

[0071]

[0072] Combining equations (3) and (10), the rotational motion of the tractor relative to the trailer can be obtained as follows:

[0073]

[0074] Based on the publicly available information, the kinematic equations of a semi-trailer vehicle are expressed as follows:

[0075]

[0076] Combining equations (6) and (10), the curvature of the trailer's trajectory can be obtained as:

[0077]

[0078] Therefore, when the curvature of the desired trailer trajectory is known to be κ2, the desired feedforward front wheel steering angle can be obtained as:

[0079]

[0080] Based on the established kinematic model of the semi-trailer, the curvature of the actual motion trajectory of the trailer's rear axle under a specific front wheel steering angle input was calculated. Therefore, assuming that the curvature of the trailer's target trajectory point is known, the feedforward front wheel steering angle used to track that trajectory can be derived in reverse.

[0081] In step 3, parking control motion planning: Based on the pure tracking control concept, and combining trajectory point information, trailer attitude angle, and rear axle center coordinate information, parking motion planning is performed based on the aiming distance parameters. Specifically, the inputs to the parking control motion planning are the coordinates of the trajectory points issued by the planning module, the target heading, and the trailer attitude angle and rear axle center coordinates issued by the positioning module. The output is the motion planning radius of the trailer rear axle center used to track the target trajectory points.

[0082] Specifically, in this embodiment, Figure 3 This is a schematic diagram of a parking control tracking model for a semi-trailer vehicle. In the diagram, R1 is the radius of motion of the tractor, R2 is the radius of motion of the trailer, and O... 12 O'2 is the steady-state rotation center of the semi-trailer, and L is the pre-aiming point of the rear axle center of the trailer. r Let Δψ be the pre-aiming distance for the movement of the trailer's rear axle, and Δψ be the angle between the trailer's rear axle and the pre-aiming point, i.e., the pre-aiming angle. Let H be the semi-trailer folding angle formed by the trailer's rear axle according to the motion plan, i.e., the target trailer turning angle. Define the articulation point as H, the intersection of the trailer and tractor's motion radii as D, and the distance from D to the tractor's rear axle O1 as L. d Among them, the pre-aiming distance L of the trailer rear axle movement. r For design parameters. The aiming distance parameter L r The larger the value, the slower the convergence of the trailer rear axle center O2 towards the reference trajectory; the aforementioned aiming distance parameter L r The smaller the value, the faster the rear axle center converges to the reference trajectory.

[0083] During steady-state steering, the radius of motion R1 of the tractor and the radius of motion R2 of the trailer are constant values. Therefore, the following relationship holds:

[0084]

[0085]

[0086] The core of the parking control motion planning adopts a pure tracking control concept, mainly through the design of the preview distance parameter L. r The actual position O2 of the rear axle center of the planned trailer is to move in an arc to the target trajectory point O'2 with a radius R2. The pre-aiming distance parameter L... r The distance between the actual position O2 of the trailer's rear axle center and the target trajectory point O'2 is the chord length of the circular motion. The aiming angle Δψ is used to calculate the motion planning radius using trigonometric functions.

[0087] In step 4, the target trailer turning angle is calculated: combining the trailer rear axle center motion radius calculated from the parking motion planning and the kinematic model parameters of the semi-trailer, the target trailer turning angle for tracking the target trajectory is calculated based on the steady-state motion geometry. Specifically, the input to the target trailer turning angle calculation is the trailer rear axle center motion planning radius and the semi-trailer kinematic model parameters obtained in step 3, and the output is the target trailer turning angle used for feedback controller design. The core of the target trailer turning angle calculation is to utilize the geometric relationship between the trailer motion and the tractor motion under the steady-state motion assumption.

[0088] Based on the above assumptions, triangle O1HD and triangle O2O 12 From D, we can obtain the following relationship:

[0089]

[0090]

[0091] Expanding equations (17) and (18), we get:

[0092]

[0093]

[0094] Adding the left and right sides of equations (19) and (20) together, we get:

[0095]

[0096] according to Figure 3 From the geometric relationships in the diagram, we can see that:

[0097]

[0098] Therefore, we can conclude that:

[0099]

[0100] Substituting equation (23) into equation (21) and rearranging, we get:

[0101]

[0102] Therefore, the distance L from point D to point O1 of the tractor's rear axle can be obtained. d The expression is:

[0103]

[0104] refer to Figure 3 Triangle O1HO 12 And triangle O2HO 12 We can obtain the following relationship:

[0105]

[0106] Therefore, the following relationship can be obtained:

[0107]

[0108] Substituting equation (27) into equation (25), we get:

[0109]

[0110] Combining equations (22) and (26) with the definition of trailer turning direction, the target trailer turning angle can be obtained as:

[0111]

[0112] For a given aiming distance L r Motion relationship analysis:

[0113] (1) If the X coordinates of the rear axle center O2 of the trailer and the target point O'2 are the same, the aiming angle Δψ is only related to the attitude angle of the trailer and the tracking target trailer turning angle. Used to eliminate heading angle error;

[0114] (2) If both the trailer and the target are parallel to the Y-axis, and the X-coordinates of the trailer's rear axle center O2 and the target point O'2 are different, the aiming angle Δψ is related to the X-coordinates of the trailer's rear axle center O2 and the target point O'2, and the target trailer's turning angle is tracked. Used to eliminate positional errors.

[0115] In step 5, the feedback control quantity is calculated: by performing a Taylor series expansion on the nonlinear kinematic model of the semi-trailer, an approximately linear model that can describe the change in trailer angle is obtained, and a feedback controller for tracking the target trailer angle is designed. Specifically, the inputs to the feedback control quantity calculation are the target trailer angle obtained in step 4 and the actual trailer angle issued by the positioning module, and the output is the feedback front wheel angle.

[0116] Specifically, in this embodiment, the calculation of the feedback control quantity includes performing a Taylor series expansion on the nonlinear kinematic model of the semi-trailer to obtain an approximately linear model that can describe the change in the trailer's turning angle. To consider system stability, a feedback controller for tracking the target trailer's turning angle is designed, and the feedback front wheel turning angle is calculated based on the feedback control gain and the trailer's turning angle error. The specific implementation is as follows:

[0117] Expanding equation (11) by a second-order Taylor series, we get:

[0118]

[0119] In actual control, the front wheel steering angle of a semi-trailer vehicle typically satisfies -45°≤δ f ≤45°, trailer turning angles should also be distributed in From equation (30), it can be seen that the value of the nonlinear term is much smaller than that of the linear term under normal operating conditions. Therefore, the change in trailer rotation angle can be approximated by a linear model:

[0120]

[0121] According to equation (30), we can obtain:

[0122]

[0123]

[0124] In the formula, a is the state transition matrix of the linear model, and b is the control matrix of the linear model.

[0125] Design a feedback controller to track the turning angle of the target trailer:

[0126]

[0127] In the formula, δ fbThe front wheel steering angle is controlled by feedback, and k is the feedback control gain.

[0128] It should also be noted that, in this embodiment, the method for solving the feedback control gain includes, but is not limited to, pole placement, optimal control, variable gain proportional control, and sliding mode control. Optionally, when According to equation (31), the closed-loop control system can be obtained as follows:

[0129]

[0130] Considering system stability, the feedback control gain is determined by configuring the pole p:

[0131]

[0132] In step 6, dynamic weighting of feedforward and feedback is performed: based on the parking control tracking effect, the feedback front wheel angle and the feedforward front wheel angle calculated by the feedback controller are dynamically weighted to obtain the total front wheel angle. Specifically, the inputs to the dynamic weighting of feedforward and feedback are the feedforward front wheel angle obtained in step 2, the feedback front wheel angle obtained in step 5, and the trailer angle error. The output is the steering wheel angle required for the automatic parking control of the semi-trailer vehicle.

[0133] Specifically, in this embodiment, by combining reference trajectory curvature tracking and target trailer turning angle tracking, a feedforward + feedback control that comprehensively considers the overall tracking requirements can be obtained as follows:

[0134] δ f =w f δ ff +w b δ fb (37)

[0135] In the formula, w f w is the weight of the feedforward front wheel steering angle. b The weight of the front wheel steering angle is used to provide feedback.

[0136] To avoid excessive interference between feedforward and feedback control, if the feedforward and feedback front wheel angles have the same sign, their weights are both 1. If the feedforward and feedback front wheel angles have opposite signs, different cases are handled. If the aiming angle is greater than a certain threshold, and the trailer angle error is greater than a certain threshold, the weight w of the feedforward front wheel angle is reduced according to the increase in the trailer angle error. f Otherwise, both have a weight of 1.

[0137] Specifically, when the aiming angle is greater than a certain threshold and the trailer turning angle error is greater than a certain threshold, the feedforward front wheel turning angle weight w is defined. f The adaptive rule is:

[0138]

[0139] In the formula, For the aiming angle threshold, w is the threshold for trailer turning angle error. f_min This represents the minimum value of the feedforward front wheel steering angle weight.

[0140] In this embodiment, the actual required front wheel angle of the tractor for parking control of the semi-trailer is the sum of the dynamically weighted values ​​of the feedforward front wheel angle and the feedback front wheel angle. Finally, using the mapping relationship between the front wheel angle and the steering wheel angle, the actual required steering wheel angle for parking control is obtained and transmitted to the steering system.

[0141] Through the detailed explanation of the above steps, this invention achieves both following the curvature of the reference trajectory and eliminating position and heading errors by tracking the turning angle of the target trailer. In addition, based on the pure tracking control concept, the tracking of position and heading errors is transformed into tracking the turning angle of the target trailer, ensuring the stability of the parking movement.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for automatic parking control of semi-trailer vehicles combining feedforward and feedback, characterized in that: The method includes two parts of calculation: the calculation of the feedforward front wheel steering angle and the calculation of the feedback front wheel steering angle. The calculation of the feedforward front wheel angle involves receiving the trajectory information and vehicle position information of the autonomous semi-trailer, constructing a kinematic model of the semi-trailer, and calculating the feedforward front wheel angle. The calculation of the feedback front wheel angle involves receiving the trajectory information and vehicle position information of the autonomous semi-trailer, performing parking control motion planning, calculating the target trailer angle for tracking the target trajectory based on the parking motion planning, designing a feedback controller for tracking the target trailer angle, and calculating the feedback front wheel angle. The feedforward front wheel angle and the feedback front wheel angle are dynamically weighted to obtain the total front wheel angle, and the total front wheel angle is converted into the steering wheel angle required for parking control, thus realizing the parking control of the semi-trailer vehicle. Implementing parking control for semi-trailer vehicles involves the following steps: Step 1: Receive trajectory information from the autonomous semi-trailer planning module and vehicle location information from the positioning module as input information; Step 2: Establish a nonlinear kinematic model of the semi-trailer vehicle, and use the trajectory information and vehicle position information input in Step 1 to obtain the feedforward front wheel steering angle; Step 3: Based on the pure tracking control algorithm, combined with the trajectory information and vehicle position information input in Step 1, parking motion planning is designed based on the pre-aiming distance parameter; Step 4: Combining the trailer rear axle center motion radius calculated by parking motion planning and the kinematic model of the semi-trailer, the target trailer turning angle for tracking the target trajectory is obtained based on the steady-state motion geometry relationship; Step 5: Perform Taylor series expansion on the kinematic model of the semi-trailer to obtain an approximate linear model of the trailer's turning angle change. Design a feedback controller to track the target trailer's turning angle and calculate the feedback front wheel turning angle. Step 6: Based on the parking control tracking effect, dynamically weight the feedback front wheel angle and the feedforward front wheel angle calculated by the feedback controller to obtain the total front wheel angle; By mapping the front wheel angle to the steering wheel angle of the semi-trailer, the actual steering wheel angle required for parking control is obtained, and the actual required steering wheel angle is transmitted to the steering system of the semi-trailer.

2. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 1, characterized in that: In step 1, the trajectory information includes the coordinates of the trajectory points, the curvature information of the trajectory points, and the target heading; the vehicle position information includes the coordinates of the rear axle center of the trailer, the actual trailer turning angle, and the trailer attitude angle.

3. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 2, characterized in that: In step 2, the inputs for the feedforward control calculation are the curvature information of the trajectory points issued by the planning module and the actual trailer turning angle issued by the positioning module, and the output is the feedforward front wheel turning angle.

4. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 1, characterized in that: In step 2, the kinematic model of the semi-trailer vehicle includes two parts: the tractor and the trailer. It is a nonlinear kinematic model with four degrees of freedom: longitudinal motion of the trailer rear axle, lateral motion of the trailer rear axle, trailer rotation, and rotation of the tractor relative to the trailer.

5. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 2, characterized in that: In step 3, the inputs to the parking control motion planning are the coordinates of the trajectory points issued by the planning module, the target heading, the trailer attitude angle issued by the positioning module, and the coordinates of the trailer rear axle center. The output is the motion planning radius of the trailer rear axle center used to track the target trajectory points.

6. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 5, characterized in that: In step 4, the input for calculating the target trailer turning angle is the motion planning radius of the trailer rear axle center and the kinematic model parameters of the semi-trailer obtained in step 3, and the output is the target trailer turning angle used for the design of the feedback controller.

7. The method for automatic parking control of semi-trailer vehicles combining feedforward and feedback as described in claim 1, characterized in that: In step 5, the input for the feedback control quantity calculation is the target trailer turning angle obtained in step 4 and the actual trailer turning angle issued by the positioning module, and the output is the feedback front wheel turning angle.

8. The automatic parking control method for semi-trailer vehicles combining feedforward and feedback as described in claim 1, characterized in that: In step 6, the inputs for the feedforward and feedback dynamic weighted system are the feedforward front wheel angle obtained in step 2 and the feedback front wheel angle and trailer angle error obtained in step 5. The output is the steering wheel angle required for the automatic parking control of the semi-trailer vehicle.

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