Tractor-trailer trajectory tracking method and device
By converting the state variables of the tractor-trailer to a flat output space and controlling it using an LQR controller in this space, the problem of insufficient tractor-trailer tracking accuracy in the prior art is solved, and a higher precision trajectory tracking effect is achieved.
Patent Information
- Application Number
- CN202510471790.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-06-17
AI Technical Summary
The prior art is difficult to achieve high-precision trajectory tracking in the tractor-trailer system, mainly because the PID controller cannot effectively deal with the problems of nonlinear dynamics and high-dimensional state space.
By converting the state variables of the tractor-trailer from the original state space to the flat output space, the LQR controller performs optimal feedback control in the flat output space, and converts the control input back to the original state space for control.
The accuracy and effect of tractor-trailer tracking is improved, and compared with the optimal feedback control directly in the original state space, the accuracy is higher and the effect is better.
Smart Images
Figure CN120156524A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of trajectory tracking, and more particularly to a trajectory tracking method and device for a tractor-trailer. Background Art
[0002] Different from standard vehicles, a tractor-trailer cannot move freely in all directions, which makes its trajectory tracking more complex. In the prior art, the system is usually locally linearized, and then a linear controller, such as a PID (Proportional-Integral-Derivative) controller, is used to control the locally linearized system to achieve trajectory tracking.
[0003] However, the PID controller can only achieve precise control of the linearized system, while the tractor-trailer system has characteristics such as non-holonomic constraints, strong non-linear dynamics, and a high-dimensional state space. Moreover, the local linearization method is difficult to fully describe the complete characteristics of the highly non-linear system. Therefore, the PID controller is difficult to meet the high-precision control requirements, resulting in poor trajectory tracking accuracy of the tractor-trailer. Summary of the Invention
[0004] The purpose of the present invention is to provide a trajectory tracking method and device for a tractor-trailer to improve the trajectory tracking accuracy of the tractor-trailer.
[0005] Based on the above purpose, on the one hand, the present invention provides a trajectory tracking method for a tractor-trailer, including:
[0006] Obtaining a current state variable in the original state space of the tractor-trailer;
[0007] Converting the current state variable from the original state space to a flat output space to obtain a current flat output variable in the flat output space;
[0008] Obtaining a target state variable in the original state space of the tractor-trailer according to a reference trajectory;
[0009] Converting the target state variable from the original state space to the flat output space to obtain a target flat output variable in the flat output space;
[0010] Calculating an error between the current flat output variable and the target flat output variable;
[0011] Inputting the error between the current flat output variable and the target flat output variable into a preset controller to enable the controller to output a current control input in the flat output space;
[0012] Convert the current control input in the flat output space to the original state space to obtain the current control input in the original state space;
[0013] Control the tractor-trailer according to the current control input in the original state space and update the state of the tractor-trailer.
[0014] Further, the state variables in the original state space include the x coordinate and y coordinate of the center of the rear axle of the tractor, the first-order derivatives of the x coordinate and y coordinate of the center of the rear axle of the tractor, the yaw angle of the tractor, the yaw angle of the trailer, the speed of the tractor, and the speed of the trailer; the flat output variables in the flat output space include the x coordinate and y coordinate of the center of the rear axle of the trailer, the first-order derivatives of the x coordinate and y coordinate of the center of the rear axle of the trailer, and the second-order derivatives of the x coordinate and y coordinate of the center of the rear axle of the trailer.
[0015] Further, converting the current state variables from the original state space to the flat output space to obtain the current flat output variables in the flat output space specifically includes:
[0016] Map the current state variables to the current flat output variables according to a pre-determined first mapping relationship; wherein, the first mapping relationship is the relationship between the state variables in the original state space and the flat output variables in the flat output space;
[0017] Converting the target state variables from the original state space to the flat output space to obtain the target flat output variables in the flat output space specifically includes:
[0018] Map the target state variables to the target flat output variables according to the first mapping relationship.
[0019] Further, converting the current control input in the flat output space to the original state space to obtain the current control input in the original state space specifically includes:
[0020] Map the current control input in the flat output space to the current control input in the original state space according to a pre-determined second mapping relationship; wherein the second mapping relationship is the mapping relationship between the control input in the flat output space and the control input in the original state space.
[0021] Further, the current control input in the flat output space includes the third-order derivatives of the x coordinate and y coordinate of the center of the rear axle of the trailer.
[0022] Further, the controller is an LQR controller.
[0023] On the other hand, the present invention provides a trajectory tracking device for a tractor-trailer, comprising:
[0024] A first acquisition module, configured to acquire the current state variables in the original state space of the tractor-trailer;
[0025] A first conversion module, configured to convert the current state variables from the original state space to a flat output space, so as to obtain the current flat output variables in the flat output space;
[0026] A second acquisition module, configured to acquire the target state variables in the original state space of the tractor-trailer according to a reference trajectory;
[0027] A second conversion module, configured to convert the target state variables from the original state space to the flat output space, so as to obtain the target flat output variables in the flat output space;
[0028] A calculation module, configured to calculate the error between the current flat output variables and the target flat output variables;
[0029] A feedforward module, configured to input the error between the current flat output variables and the target flat output variables into a preset controller, so that the controller outputs the current control input in the flat output space;
[0030] A third conversion module, configured to convert the current control input in the flat output space to the original state space, so as to obtain the current control input in the original state space;
[0031] A control module, configured to control the tractor-trailer according to the current control input in the original state space, and update the state of the tractor-trailer.
[0032] Further, the state variables in the original state space include the x coordinate and y coordinate of the rear axle center of the tractor, the first-order derivatives of the x coordinate and y coordinate of the rear axle center of the tractor, the yaw angle of the tractor, the yaw angle of the trailer, the speed of the tractor, and the speed of the trailer; the flat output variables in the flat output space include the x coordinate and y coordinate of the rear axle center of the trailer, the first-order derivatives of the x coordinate and y coordinate of the rear axle center of the trailer, and the second-order derivatives of the x coordinate and y coordinate of the rear axle center of the trailer.
[0033] Further, converting the current state variables from the original state space to the flat output space to obtain the current flat output variables in the flat output space specifically includes:
[0034] Map the current state variable to the current flat output variable according to a pre-determined first mapping relationship; wherein, the first mapping relationship is the relationship between the state variable in the original state space and the flat output variable in the flat output space;
[0035] Convert the target state variable from the original state space to the flat output space to obtain the target flat output variable in the flat output space, specifically including:
[0036] Map the target state variable to the target flat output variable according to the first mapping relationship.
[0037] Further, convert the current control input in the flat output space to the original state space to obtain the current control input in the original state space, specifically including:
[0038] Map the current control input in the flat output space to the current control input in the original state space according to a pre-determined second mapping relationship; wherein the second mapping relationship is the mapping relationship between the control input in the flat output space and the control input in the original state space.
[0039] Further, the current control input in the flat output space includes the third derivatives of the x coordinate and the y coordinate of the center of the rear axle of the trailer.
[0040] Further, the controller is an LQR controller. Description of the Drawings
[0041] Figure 1 It is a flowchart of the trajectory tracking method for a tractor-trailer according to an embodiment of the present invention;
[0042] Figure 2 It is a schematic diagram of the kinematic model of a tractor-trailer according to an embodiment of the present invention;
[0043] Figure 3A And Figure 3B They are respectively schematic diagrams of the effects obtained after performing reverse trajectory tracking on a tractor-trailer by using the method of the embodiment of the present invention and by using the existing method;
[0044] Figure 4 It is a structural block diagram of the trajectory tracking device for a tractor-trailer according to an embodiment of the present invention. Detailed Embodiment
[0045] The following combines the drawings to give the preferred embodiments of the present invention and describes them in detail.
[0046] As Figure 1As shown in the figure, an embodiment of the present invention provides a trajectory tracking method for a tractor-trailer, which includes the following steps S100 - S800:
[0047] S100: Obtain the current state variables in the original state space of the tractor-trailer.
[0048] As Figure 2 shown, based on the kinematic characteristics of the tractor-trailer, establish the following kinematic model:
[0049]
[0050]
[0051]
[0052]
[0053]
[0054] Among them, x0 is the x coordinate of the center of the rear axle of the tractor, y0 is the y coordinate of the center of the rear axle of the tractor, x1 is the x coordinate of the center of the rear axle of the trailer, y1 is the y coordinate of the center of the rear axle of the trailer, is the yaw angle of the tractor, is the yaw angle of the trailer, d0 is the wheelbase of the tractor, d1 is the length of the connecting rod between the tractor and the trailer, v0 is the speed of the tractor, v1 is the speed of the trailer, δ is the steering angle of the front wheels of the tractor, and a is the acceleration of the tractor.
[0055] As can be seen from the above formula, the kinematic model of the tractor-trailer has strong nonlinearity. By deriving it, we can obtain:
[0056]
[0057]
[0058]
[0059]
[0060]
[0061]
[0062]
[0063]
[0064]
[0065]
[0066]
[0067]
[0068]
[0069]
[0070] Among them, a1 is the acceleration of the trailer. It can be seen from this that x1 and y1 and their higher-order derivatives can represent all other variables and can also be represented by all other variables. Therefore, the tractor-trailer system has differential flatness, and x1 and y1 can be selected as the flat outputs to convert the state variables of the tractor-trailer between the original state space and the flat output space.
[0071] In the present invention, unless otherwise specified, the derivative of a certain variable refers to the derivative of the variable with respect to time.
[0072] In some embodiments, the current state variables include x0, y0, v0, v1. Among them, x0 and y0 can be obtained by a position sensor, while v0 and v1 can be obtained by existing methods. For example, they can be predicted based on historical data using existing prediction algorithms.
[0073] S200: Convert the current state variables from the original state space to the flat output space to obtain the current flat output variables in the flat output space.
[0074] In some embodiments, the flat output variables may include x1, y1, and If the flat output variables are represented by X, then X satisfies the following relational expressions:
[0075]
[0076] Converting the current state variables from the original state space to the flat output space means calculating the current flat output variables according to a pre-determined first mapping relationship. The first mapping relationship is the relationship between the state variables in the original state space and the flat output variables in the flat output space. In this embodiment, it is the above formulas (14)-(19). Substituting the current state variables into the above formulas (14)-(19) can obtain the current flat output variables.
[0077] S300: Obtain the target state variables in the original state space of the tractor-trailer according to the reference trajectory.
[0078] The reference trajectory refers to the driving trajectory that the vehicle is expected to follow, which includes a series of reference trajectory points discretized over time. Each reference trajectory point includes information such as position, speed, yaw angle, etc. The reference trajectory can be obtained in advance before trajectory tracking. After obtaining the current state variables of the tractor-trailer, the target trajectory point can be obtained on the reference trajectory, and the x0, y0, v0, v1 of the target trajectory point are used as the target state variables. The method for obtaining the target trajectory point can adopt the methods in the prior art. For example, according to the current position and speed of the tractor, and the preset forward viewing distance (usually related to the vehicle speed, the higher the vehicle speed, the greater the forward viewing distance), a forward viewing point can be found on the reference trajectory, and this forward viewing point is the target trajectory point.
[0079] S400: Convert the target state variables from the original state space to the flat output space to obtain the target flat output variables in the flat output space.
[0080] Similar to step S200, the target state variables can be mapped to the flat output through the first mapping relationship to obtain the target flat output variables.
[0081] S500: Calculate the error between the current flat output variables and the target flat output variables.
[0082] Subtract the target flat output variables from the current flat output variables, which is the error between the two.
[0083] S600: Input the error between the current flat output variables and the target flat output variables into a preset controller so that the controller outputs the current control input in the flat output space.
[0084] In some embodiments, the preset controller can be any suitable controller, including but not limited to an LQR controller (linear quadratic regulator), a PID (proportional-integral-derivative) controller, etc.
[0085] Taking the LQR controller as an example, its design method is as follows:
[0086] In the flat coordinate system, the flat output variables and the control input satisfy the following relational expression:
[0087]
[0088] where X is the flat output variable, is the derivative of the flat output variable with respect to time, A and B are both system matrices, and U is the control input.
[0089] where,
[0090] The objective function J of the LQR controller is as follows:
[0091]
[0092] where Q and R are the state weight matrix and the input weight matrix respectively. By designing Q and R and solving the Riccati equation, the optimal feedback gain K=(B T PB + R) -1 B T PA.
[0093] Assume that ΔX is the error between the current flat output variable and the target flat output variable. Then the current control input is: U = -KΔX.
[0094] S700: Convert the current control input in the flat output space to the original state space to obtain the current control input in the original state space.
[0095] In some embodiments, the current control input in the original state space includes the acceleration a of the tractor and the front wheel steering angle δ of the tractor. After obtaining the current control input in the flat output space and the current control input in the original state space can be obtained according to the pre-determined second mapping relationship. The second mapping relationship refers to formulas (5) and (12). Since the obtained current control input is and in order to obtain a and δ based on them, the parameters in formulas (5) and (12) need to be converted into relationships with and . Specifically as follows:
[0096]
[0097]
[0098]
[0099]
[0100] where is the third derivative of x1, is the third derivative of y1. Substitute and into the above formulas, and can be obtained, and then Then substitute them into formulas (12) and (13) to obtain the front wheel steering angle δ and the acceleration a of the tractor.
[0101] S800: Control the tractor-trailer according to the current control input in the original state space, and update the state of the tractor-trailer.
[0102] After obtaining the acceleration a and front wheel angle δ of the tractor, the acceleration and front wheel angle of the tractor can be adjusted to the calculated values. Then, the tractor-trailer will travel with the new acceleration and front wheel angle and update its state. Then, the state variables of the tractor-trailer in the original state space can be obtained at the next moment and used as the current state variables again. Then, repeat steps S100 - S800, continuously adjusting the acceleration and front wheel angle of the tractor-trailer to make the driving trajectory of the tractor-trailer approach the reference trajectory and achieve trajectory tracking.
[0103] To evaluate the performance of the trajectory tracking method of the embodiments of the present invention, the trajectory tracking method of the embodiments of the present invention and the existing method of directly using an LQR controller for trajectory tracking are respectively used to perform reverse trajectory tracking on the tractor-trailer, and the obtained trajectory tracking effects are respectively as Figure 3A and 3B shown, where the red line represents the reference trajectory, the yellow line represents the reverse trajectory of the center of the rear axle of the tractor, and the green line is the reverse trajectory of the center of the rear axle of the trailer. It can be seen from the figure that the reverse trajectory line obtained by using the method of the embodiments of the present invention is closer to the reference trajectory, indicating that the method of the embodiments of the present invention has higher tracking accuracy and better effect.
[0104] The trajectory tracking method of the tractor-trailer in the embodiments of the present invention first converts the strongly non-linear kinematic model of the tractor-trailer to a linear flat output space, and uses a linear controller to output a control input in the flat output space, and then converts the control input in the flat output space back to the original state space, so as to realize the control of the tractor-trailer; since the LQR controller performs optimal feedback control on the flat output space, compared with the existing method of directly performing optimal feedback control on the non-linear system in the original state space, it has higher accuracy and better effect.
[0105] As Figure 4As shown in the figure, an embodiment of the present invention further provides a trajectory tracking device for a tractor-trailer, which includes a first acquisition module 10, a first conversion module 20, a second acquisition module 30, a second conversion module 40, a calculation module 50, a feedforward module 60, a third conversion module 70, and a control module 80. The first acquisition module 10 is configured to acquire the current state variables of the tractor-trailer in the original state space. The first conversion module 20 is configured to convert the current state variables from the original state space to the flat output space to obtain the current flat output variables in the flat output space. The second acquisition module 30 is configured to acquire the target state variables of the tractor-trailer in the original state space according to the reference trajectory. The second conversion module 40 is configured to convert the target state variables from the original state space to the flat output space to obtain the target flat output variables in the flat output space. The calculation module 50 is configured to calculate the error between the current flat output variables and the target flat output variables. The feedforward module 60 is configured to input the error between the current flat output variables and the target flat output variables into a preset controller so that the controller outputs the current control input in the flat output space. The third conversion module 70 is configured to convert the current control input in the flat output space to the original state space to obtain the current control input in the original state space. The control module 80 is configured to control the tractor-trailer according to the current control input in the original state space and update the state of the tractor-trailer.
[0106] For the specific implementation manners of the first acquisition module 10, the first conversion module 20, the second acquisition module 30, the second conversion module 40, the calculation module 50, the feedforward module 60, the third conversion module 70, and the control module 80, reference may be made to the method embodiments, which will not be elaborated herein.
[0107] The trajectory tracking device for the tractor-trailer according to the embodiment of the present invention first converts the strongly nonlinear kinematic model of the tractor-trailer to the linear flat output space, and uses the linear controller to output the control input in the flat output space, and then converts the control input in the flat output space back to the original state space, so as to realize the control of the tractor-trailer. Since the LQR controller performs optimal feedback control on the flat output space, compared with the existing method of directly performing optimal feedback control on the nonlinear system in the original state space, the accuracy is higher and the effect is better.
[0108] Another embodiment of the present invention provides a readable storage medium, on which a computer program is stored. When the computer program is executed on a computer, the computer is made to execute the steps of the trajectory tracking method for the tractor-trailer in the above embodiment of the present invention.
[0109] Another embodiment of the present invention provides an electronic device, which includes a memory and a processor. An executable code is stored in the memory. When the processor executes the executable code, it performs the steps of the tractor-trailer trajectory tracking method in the above embodiments of the present invention.
[0110] The systems, devices, modules or units illustrated in the above embodiments can be specifically implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.
[0111] For convenience of description, when describing the above devices, they are described separately as various units according to functions. Of course, when implementing the present invention, the functions of each unit can be implemented in one or more software and / or hardware.
[0112] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.
[0113] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.
[0114] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device realizes the functions in Figure 1 one process or multiple processes and / or blocks Figure 1The functions specified in one or more boxes.
[0115] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide for implementing the steps of the functions specified in one Figure 1 one process or more processes and / or boxes Figure 1 or more boxes.
[0116] In a typical configuration, an electronic device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.
[0117] The memory may include non-permanent memory in the computer-readable medium, in the form of random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.
[0118] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can store information by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by an electronic device. As defined herein, computer-readable media does not include transitory media, such as modulated data signals and carrier waves.
[0119] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the element.
[0120] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.
[0121] The present invention can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present invention can also be practiced in a distributed computing environment where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.
[0122] The embodiments of the present invention are described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiments.
[0123] The above describes specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the figures do not necessarily require the specific order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.
[0124] The above are only the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The above embodiments of the present invention can also be subject to various changes. That is, all simple, equivalent changes and modifications made in accordance with the claims and the content of the specification of the present invention application fall within the scope of the protection of the claims of the present invention patent. What the present invention does not describe in detail is all conventional technical content.
Claims
1. A tractor-trailer trajectory tracking method, characterized in that: include: Obtain the current state variables in the original state space of the tractor-trailer; Converting the current state variable from the original state space to a flat output space to obtain a current flat output variable in the flat output space; Obtaining target state variables in the original state space of the tractor-trailer according to the reference trajectory; Converting the target state variable from the original state space to the flat output space to obtain a target flat output variable in the flat output space; calculating an error between the current flat output variable and the target flat output variable; Inputting the error between the current flat output variable and the target flat output variable into a preset controller so that the controller outputs the current control input in the flat output space; Converting the current control input in the flat output space to the original state space to obtain the current control input in the original state space; The tractor-trailer is controlled according to the current control input in the original state space, and the state of the tractor-trailer is updated.
2. The tractor-trailer trajectory tracking method according to claim 1, characterized in that: The state variables in the original state space include the x-coordinate and y-coordinate of the rear axle center of the tractor, the first-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the tractor, the yaw angle of the tractor, the yaw angle of the trailer, the speed of the tractor and the speed of the trailer; the flat output variables in the flat output space include the x-coordinate and y-coordinate of the rear axle center of the trailer, the first-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the trailer, and the second-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the trailer.
3. The tractor-trailer trajectory tracking method according to claim 1, characterized in that: Converting the current state variable from the original state space to the flat output space to obtain the current flat output variable in the flat output space specifically includes: According to a predetermined first mapping relationship, the current state variable is mapped to the current flat output variable; wherein the first mapping relationship is the relationship between the state variable in the original state space and the flat output variable in the flat output space; Converting the target state variable from the original state space to the flat output space to obtain the target flat output variable in the flat output space specifically includes: According to the first mapping relationship, the target state variable is mapped to the target flat output variable.
4. The tractor-trailer trajectory tracking method according to claim 1, characterized in that: Converting the current control input in the flat output space to the original state space to obtain the current control input in the original state space specifically includes: According to a predetermined second mapping relationship, the current control input in the flat output space is mapped to the current control input in the original state space; wherein the second mapping relationship is a mapping relationship between the control input in the flat output space and the control input in the original state space.
5. The tractor-trailer trajectory tracking method according to claim 1, characterized in that: The current control input in the flat output space includes the third-order derivatives of the x-coordinate and y-coordinate of the center of the rear axle of the trailer; and the controller is an LQR controller.
6. A tractor-trailer trajectory tracking device, characterized in that: include: A first acquisition module is used to acquire the current state variables in the original state space of the tractor-trailer; A first conversion module, used for converting the current state variable from the original state space to a flat output space to obtain a current flat output variable in the flat output space; A second acquisition module is used to acquire the target state variable in the original state space of the tractor-trailer according to the reference trajectory; A second conversion module, used for converting the target state variable from the original state space to the flat output space to obtain a target flat output variable in the flat output space; A calculation module, configured to calculate an error between the current flat output variable and the target flat output variable; A feedforward module, used for inputting the error between the current flat output variable and the target flat output variable into a preset controller, so that the controller outputs the current control input in the flat output space; A third conversion module, used for converting the current control input in the flat output space to the original state space to obtain the current control input in the original state space; A control module is used to control the tractor-trailer according to the current control input in the original state space and update the state of the tractor-trailer.
7. The tractor-trailer trajectory tracking device according to claim 6, characterized in that: The state variables in the original state space include the x-coordinate and y-coordinate of the rear axle center of the tractor, the first-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the tractor, the yaw angle of the tractor, the yaw angle of the trailer, the speed of the tractor and the speed of the trailer; the flat output variables in the flat output space include the x-coordinate and y-coordinate of the rear axle center of the trailer, the first-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the trailer, and the second-order derivatives of the x-coordinate and y-coordinate of the rear axle center of the trailer.
8. The tractor-trailer trajectory tracking device according to claim 6, characterized in that: Converting the current state variable from the original state space to the flat output space to obtain the current flat output variable in the flat output space specifically includes: According to a predetermined first mapping relationship, the current state variable is mapped to the current flat output variable; wherein the first mapping relationship is the relationship between the state variable in the original state space and the flat output variable in the flat output space; Converting the target state variable from the original state space to the flat output space to obtain the target flat output variable in the flat output space specifically includes: According to the first mapping relationship, the target state variable is mapped to the target flat output variable.
9. The tractor-trailer trajectory tracking device according to claim 6, characterized in that: Converting the current control input in the flat output space to the original state space to obtain the current control input in the original state space specifically includes: According to a predetermined second mapping relationship, the current control input in the flat output space is mapped to the current control input in the original state space; wherein the second mapping relationship is a mapping relationship between the control input in the flat output space and the control input in the original state space.
10. The tractor-trailer trajectory tracking device according to claim 6, characterized in that: The current control input in the flat output space includes the third-order derivatives of the x-coordinate and y-coordinate of the center of the rear axle of the trailer; and the controller is an LQR controller.