A path tracking control method for a central hinge type scraper

Abstract

The present invention proposes a path tracking control method for a center-articulated scraper, which relates to the field of vehicle control technology. By introducing a nonlinear adjustment mechanism, the inherent strong nonlinearity and large time delay problems of the hydraulic steering system are effectively solved. The method can adaptively adjust the preview distance according to the real-time state of the center-articulated scraper, compensate for the nonlinearity and hysteresis effects brought by the hydraulic system, thereby significantly improving the path tracking accuracy and the robustness of the overall system. By adopting an adaptive preview distance, the present invention can calculate the feedback error in real time, and process it by a nonlinear feedback error controller to generate the actual control input. Compared with traditional feedback error-based control methods, the present invention performs more stably under dynamically changing working conditions and has higher control accuracy, ensuring the path tracking accuracy of the scraper under complex working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control, in particular to a path tracking control method for a center-hinged scraper. Background Art

[0002] With the continuous development of trackless mining technology, hydraulic center-articulated scrapers (SLDs) play a vital role as core equipment for underground operations. Compared to traditional fixed-frame center-articulated scrapers, their center-articulated structure offers greater maneuverability and flexibility, enabling efficient operation in the narrow and complex environments of underground mining. With the advancement of technologies such as sensors and intelligent control, underground scrapers are gradually becoming intelligent, but their autonomous driving technology still faces significant challenges. The performance of hydraulic systems is limited by factors such as the inertia of the hydraulic oil flow, the mechanical inertia of the hydraulic cylinder and motor, the compressibility of the hydraulic fluid, and transmission delays within the pipeline.

[0003] These factors make it difficult to accurately model the hydraulic system, which in turn affects its adaptability to external disturbances and, in turn, negatively impacts path-tracking accuracy. Consequently, existing model-based automatic control methods exhibit significant limitations in practical applications. The confined working environment of underground mines places higher demands on the accuracy and stability of path-tracking control. Complex road conditions and fluctuating loads further exacerbate control challenges, becoming a major obstacle to achieving autonomous and intelligent development of scrapers in real-world scenarios.

[0004] Control methods based on center-articulated scraper models and feedback errors have been widely used to solve the nonlinear path tracking control problem of hydraulically driven center-articulated scrapers. However, the effectiveness of these research results in practical applications is still significantly limited. In particular, the hysteresis effect and large inertia of the hydraulic system make the practical application of these methods very challenging. Existing control methods based on center-articulated scraper models are mostly concentrated in simulation environments or scaled-down demonstration center-articulated scrapers, but their control effects have not been fully verified in the actual scraper working environment. Traditional feedback error-based methods cannot provide sufficient accuracy and adaptability when faced with dynamically changing loads, speeds, and working conditions, limiting their application in the control of complex center-articulated scrapers such as hydraulically driven center-articulated scrapers. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a path tracking control method for a center-hinged scraper, comprising:

[0006] Step 1: Using the onboard sensors configured on the center-articulated scraper, status information of the center-articulated scraper is collected, wherein the status information includes speed, front wheel center position, and rear wheel center position. The onboard sensors transmit the status information to the main controller;

[0007] Step 2: In the main controller, determine the current state of the center-articulated scraper, which is expressed as:

[0008] ;

[0009] in, x Reference state position G The horizontal axis, y Reference state position G The vertical coordinate, is the orientation angle, is the hinge angle;

[0010] Step 3: Get the reference path RP , the reference path RP It is composed of multiple discrete points. The points on the reference path are represented as:

[0011] ;

[0012] in, represents a point in the reference path, u is the reference path parameter, for The horizontal axis, for The vertical coordinate, U is the domain of the path parameter;

[0013] Step 4: In the reference path RP On the reference state position G Corresponding reference path points ,in, Reference path point The horizontal axis, Reference path point The vertical coordinate, Reference path point Path parameters;

[0014] Step 5: Calculate the reference state position G and reference waypoints The Euclidean distance between the reference state positions G and reference waypoints The Euclidean distance between , which is specifically achieved through the following formula:

[0015] ;

[0016] Step 6: Speed Based v and lateral error , dynamically adjust the preview distance, and then determine the preview point L , the preview point L is the position of the reference state at all points in the reference path G The distance is the preview distance point, reference state position G Point to preview point L The direction is the preview direction;

[0017] Step 7: Get the desired state of the center hinge scraper , the desired state Expressed as:

[0018] ;

[0019] in, represents an expected articulation angle, which is the articulation angle corresponding to the instantaneous expected path of the center-articulated scraper passing through the preview point;

[0020] Step 8: Calculate the angle between the center-hinged scraper's current direction of motion and its preview direction , and then calculate the desired state articulation angle Quantity ;

[0021] Step 9: Calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , and then calculate the feedback error ;

[0022] Step 10: Based on the feedback error , calculate the proportional term of the controller , integral item and nonlinear differential terms , and then calculate the output signal of the controller , the output signal of the controller Used to adjust the opening of the steering valve in the hydraulic system.

[0023] Optionally, step 2 specifically includes:

[0024] In the main controller, according to the traveling state of the center-articulated scraper, one of the front wheel center posture and the rear wheel center posture is selected as the target center posture, and the target center posture determines the reference state position and orientation angle. , according to the center position of the front wheel and the center position of the rear wheel, determine the articulation angle , the articulation angle is the relative rotation angle between the front and rear bodies of the center-hinged scraper, with reference to the state position and orientation angle and articulation angle Make up the current state.

[0025] Optionally, step 4 specifically includes:

[0026] Reference waypoints As unknown parameters, calculate the reference path points The tangent vector of , The components are expressed as:

[0027] ;

[0028] ;

[0029] in, express The first derivative of express The first derivative of ;

[0030] Based on the reference state position G and the tangent vector , construct the tangent equation, which is expressed as:

[0031] ;

[0032] in, Reference path point The tangent vector at ;

[0033] Solve the tangent equation and get the solution set , in the solution set In the case of G The nearest point is used as a reference path point , in the solution set In the case of Upper selection and reference state position G The nearest point is used as a reference path point .

[0034] Optionally, in step 6, based on speed v and lateral error , the dynamic adjustment of preview distance is realized by the following formula:

[0035] ;

[0036] in, Indicates preview distance. Used to adjust the sensitivity of preview distance changes. express The degree of influence on the preview distance, Represents the hinge angle The degree of impact on preview distance.

[0037] Optionally, step 8 specifically includes:

[0038] Calculate the angle between the vehicle's current direction of movement and the preview direction , which is specifically achieved through the following formula:

[0039] ;

[0040] in, Reference state position G The y component of the coordinate, Reference state position G Coordinates x The weight, Reference state position G The orientation angle The weight;

[0041] Since the instantaneous turning radius is the turning radius of the preceding vehicle, a geometric equation is constructed based on the geometric relationship. The geometric equation is expressed as follows:

[0042] ;

[0043] in, is the length of the front body of the center-hinged scraper, is the length of the rear body of the center-hinged scraper, is the desired state articulation angle The weight;

[0044] The desired state articulation angle is calculated from the geometric equation Quantity .

[0045] Optionally, step 9 specifically includes:

[0046] Calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , which is specifically achieved through the following formula:

[0047] ;

[0048] in, is the length from the hinge point to the first connection point, where the first connection point is the connection point between the hydraulic cylinder and the front vehicle body, is the length from the hinge point to the second connection point, where the second connection point is the connection point between the hydraulic cylinder and the rear body. is the initial length of the hydraulic cylinder;

[0049] Based on the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , calculate the feedback error , specifically expressed by the following formula:

[0050] ;

[0051] in, is the physical limit of the hinge angle.

[0052] Optionally, step 10 specifically includes:

[0053] Step 10.1: Based on the feedback error , calculate the proportional term of the controller , which is specifically achieved through the following formula:

[0054] ;

[0055] in, is the proportional gain coefficient, is the saturation value of the proportional term, is a symbolic function;

[0056] Step 10.2: Based on the feedback error , the integral term of the controller in the calculation , which is specifically achieved through the following formula:

[0057] ;

[0058] in, is the integral gain coefficient, The saturation value of the integral term;

[0059] Step 10.3: Based on the feedback error The differential of the controller is used to calculate the nonlinear differential term , which is specifically achieved through the following formula:

[0060] ;

[0061] in, is the differential gain coefficient, is the magnification, Feedback error The differential of

[0062] Step 10.4: Based on the proportional term , integral item and nonlinear differential terms , calculate the output signal of the controller , which is specifically achieved through the following formula:

[0063] ;

[0064] in, is the load The gain factor.

[0065] The beneficial effects of adopting the above technical solution are:

[0066] The present invention proposes a path tracking control method for a center-articulated scraper. By introducing a nonlinear adjustment mechanism, it effectively solves the strong nonlinearity and large time delay problems inherent in the hydraulic steering system. The method can adaptively adjust the preview distance according to the real-time center-articulated scraper state, compensate for the nonlinearity and hysteresis effects brought by the hydraulic system, thereby significantly improving the path tracking accuracy and the robustness of the overall system. By adopting an adaptive preview distance, the present invention can calculate the feedback error in real time, and process it by a nonlinear feedback error controller to generate the actual control input. Compared with traditional feedback error-based control methods, the present invention performs more stably under dynamically changing working conditions and has higher control accuracy, ensuring the path tracking accuracy of the scraper under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 1. A schematic flow chart of a path tracking control method for a center-hinged scraper according to an embodiment of the present invention;

[0068] Figure 2 is a schematic diagram of a center-hinged scraper in a forward motion according to an embodiment of the present invention;

[0069] Figure 3 Schematic diagram of dynamically adjusting the preview distance when the center-hinged scraper is moving forward in an embodiment of the present invention;

[0070] Figure 4 is a schematic diagram of a desired state of a center-hinged scraper in an embodiment of the present invention;

[0071] Figure 5 Schematic diagram of the extension and retraction of the hydraulic cylinder of a center-hinged scraper during steering in an embodiment of the present invention. DETAILED DESCRIPTION

[0072] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0073] The purpose of this invention is to provide a path-following control method for hydraulic center-articulated scrapers (LHDs) in complex underground mining environments. This method aims to overcome the limited applicability of existing path-following control technologies to dynamic characteristics such as hydraulic system nonlinearity and vehicle state changes. In particular, it aims to achieve high-precision path-following control even when effective vehicle modeling is unavailable.

[0074] Specifically, the present invention provides a path tracking control method for a center hinged scraper. Figure 1 , which may include the following steps:

[0075] Step 1: Using onboard sensors configured on the center-articulated scraper, including but not limited to a three-dimensional laser radar and an inertial measurement unit, to collect status information of the center-articulated scraper, the status information including speed, front wheel center position, and rear wheel center position. The onboard sensors transmit the status information to the main controller. Specifically, the onboard sensors periodically transmit the status information to the main controller via a network interface.

[0076] Step 2: In the main controller, determine the current state of the center-hinged scraper, i.e. Figure 1 In the sensor information acquisition and processing part, the current state is expressed as:

[0077] ;

[0078] in, x Reference state position G The horizontal axis, y Reference state position G The vertical coordinate, is the orientation angle, is the hinge angle;

[0079] Specifically, in the main controller, according to the traveling state of the center-articulated scraper, one of the front wheel center posture and the rear wheel center posture is selected as the target center posture, and the target center posture determines the reference state position and orientation angle. ,

[0080] Specifically, when the center-hinged scraper is moving forward, the target center position is the front wheel center position, and the reference state position is G Front wheel center , the heading angle is the yaw angle of the front vehicle body in the world coordinate system. When the center-hinged scraper is running backward, the target center position is the center position of the rear wheel. The reference state position G Rear wheel center , the heading angle is the yaw angle of the rear vehicle body in the world coordinate system.

[0081] Determine the articulation angle based on the front wheel center posture and the rear wheel center posture , the articulation angle is the relative rotation angle between the front and rear bodies of the center-hinged scraper, with reference to the state position and orientation angle and articulation angle Make up the current state.

[0082] Figure 2 FIG. 1 is a schematic diagram of a center-hinged scraper in an embodiment of the present invention in a forward motion state, wherein: is a Cartesian coordinate system, P and Q represent the center of the rear wheel and the center of the front wheel of the center hinged scraper respectively, It is the hinge point between the front and rear bodies of the center hinged scraper. is the instantaneous center of rotation of the center-hinged scraper, is the articulation angle of the center-hinged scraper, and They are respectively represented as the orientation angles of the front and rear vehicles in the world coordinate system, and Represented as the front and rear vehicle lengths, and Respectively represents the front and rear vehicle turning radius. Figure 2 , it can be clearly seen that the parameters of the current state are represented when the center hinged scraper is in forward motion.

[0083] Step 3: Get the reference path RP , the reference path RP It is composed of multiple discrete points. The points on the reference path are represented as:

[0084] ;

[0085] in, represents a point in the reference path, u is the reference path parameter, for The horizontal axis, for The vertical coordinate, U is the domain of the path parameter;

[0086] Step 4: In the reference path RP On the reference state position G Corresponding reference path points ,in, Reference path point The horizontal axis, Reference path point The vertical coordinate, Reference path point Path parameters;

[0087] Specifically, the reference path point As unknown parameters, calculate the reference path points The tangent vector of , The components are expressed as:

[0088] ;

[0089] ;

[0090] in, express The first derivative of express The first derivative of ;

[0091] Based on the reference state position G and the tangent vector , construct the tangent equation, which is expressed as:

[0092] ;

[0093] in, Reference path point The tangent vector at

[0094] Solve the tangent equation and get the solution set , in the solution set In the case of G The nearest point is used as a reference path point , reference path point Path parameters The following relations are satisfied:

[0095] ;

[0096] In the solution set In the case of Upper selection and reference state position G The nearest point is used as a reference path point , reference path point Path parameters The following relations are satisfied:

[0097] ;

[0098] Step 5: Calculate the reference state position G and reference waypoints The Euclidean distance between the reference state positions Gand reference waypoints The Euclidean distance between , which is specifically achieved through the following formula:

[0099] ;

[0100] Furthermore, the present invention proposes a method for dynamically adjusting the preview distance based on real-time status, which takes into account the vehicle's speed in the embodiment of the present invention. v , lateral error deviation between the reference state position and the reference path , articulation angle .

[0101] Furthermore, in order to avoid instability in the control system, a smoothing processing mechanism is introduced into the adjustment process of the preview distance. By constraining the change range of the preview distance, the adjustment process is ensured to be smooth, avoiding the impact of excessive oscillation or response delay on control accuracy and system stability.

[0102] Step 6: Speed Based v and lateral error , dynamically adjust the preview distance, that is Figure 1 Adaptive preview distance adjustment to determine the preview point L , the preview point L is the position of the reference state at all points in the reference path G The distance is the preview distance point, reference state position G Point to preview point L The direction is the preview direction;

[0103] Among them, if the reference trajectory If there is no completely matching point on the image, linear interpolation is used to calculate between adjacent points to obtain a point that meets the preview distance requirement and is determined as the preview point. location.

[0104] Among them, based on speed v and lateral error , the dynamic adjustment of preview distance is realized by the following formula:

[0105] ;

[0106] in, Indicates preview distance. Used to adjust the sensitivity of preview distance changes. express The degree of influence on the preview distance, Represents the hinge angle The degree of impact on preview distance.

[0107] Figure 3 Schematic diagram of the dynamic adjustment of the preview distance when the center hinged scraper is moving forward, where: Q represents the reference state position, is the reference path point, (a) indicates high lateral error , small articulation angle and low speed Schematic diagram, this case will result in preview distance Small, (b) indicates high lateral error , small articulation angle and high speed Schematic diagram, this case will result in preview distance Smaller, (c) indicates low lateral error , small articulation angle and low speed Schematic diagram, this case will result in preview distance Smaller, (d) indicates low lateral error , small articulation angle and high speed Schematic diagram, this case will result in preview distance Larger, (e) indicates low lateral error , large articulation angle and low speed Schematic diagram, this case will result in preview distance Smaller; combined Figure 3 , when the center hinged scraper slips or has a large initial error, Play a leading role, different right The impact is small; when the center-hinged scraper enters a steady state ( smaller), Play a leading role, allowing the system to ,Low ,Small In the case of increase , increasing the stability of path tracking; when the center-hinged scraper is on a curve ( Larger), The path of the center-hinged scraper is greatly reduced, which helps the center-hinged scraper to recover its path in complex working conditions while maintaining precise control when the curvature changes.

[0108] Step 7: Get the desired state of the center hinge scraper , the desired state Expressed as:

[0109] ;

[0110] in, represents an expected articulation angle, which is the articulation angle corresponding to the instantaneous expected path of the center-articulated scraper passing through the preview point;

[0111] Step 8: Calculate the angle between the center-hinged scraper's current direction of motion and its preview direction , and then calculate the desired state articulation angle Quantity ;

[0112] Figure 4 Schematic diagram of the desired state of the center hinged scraper in an embodiment of the present invention, wherein: Indicates the point of articulation between the front and rear sections of a center-hinged scraper. is the center of the circle, passing through the point and point The arc represents the instantaneous desired path of the center-articulated scraper, passing through the preview point The dotted and solid lines represent the reference path of the center-hinged scraper in the embodiment of the present invention. Indicates the desired position of the rear wheel center of a center-hinged scraper. represents the instantaneous center of rotation of the center-hinged scraper in the desired state, represents the instantaneous turning radius of the center-hinged scraper, represents the desired articulation angle for a center-hinged scraper, Indicates the real-time preview point of the center-hinged scraper. Indicates the orientation of the rear vehicle at the desired articulation angle.

[0113] Specifically, calculate the angle between the vehicle's current direction of movement and the preview direction , which is specifically achieved through the following formula:

[0114] ;

[0115] in, Reference state position G Coordinates y The weight, Reference state position G Coordinates x The weight, Reference state position G The orientation angle The weight;

[0116] Since the value of the instantaneous turning radius is the turning radius of the preceding vehicle, that is, , construct a geometric equation based on the geometric relationship, and the geometric equation is expressed as:

[0117] ;

[0118] in, is the length of the front body of the center-hinged scraper, is the length of the rear body of the center-hinged scraper, is the desired state articulation angle The weight;

[0119] The desired state articulation angle is calculated from the geometric equation Quantity .

[0120] Furthermore, the present invention also calculates the articulation angle error , which is specifically achieved through the following formula:

[0121] ;

[0122] in, Reference state position G Articulation angle Quantity;

[0123] Figure 5 The diagram below shows the extension and retraction of the hydraulic cylinder during the steering process of a center hinged scraper. Indicates the point of articulation between the front and rear sections of a center-hinged scraper. and Respectively represent the connection points between the hydraulic cylinder and the front and rear parts of the center-hinged scraper, and At the joint angle When respectively represent the corresponding connection points, is the articulation angle of the vehicle body in the initial state, and They represent the length from the hinge point to the front and rear connection points of a center-hinged scraper.

[0124] Step 9: Combine Figure 5 , calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , and then calculate the feedback error ;

[0125] Calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , which is specifically achieved through the following formula:

[0126] ;

[0127] in, is the length from the hinge point to the first connection point, where the first connection point is the connection point between the hydraulic cylinder and the front vehicle body, is the length from the hinge point to the second connection point, where the second connection point is the connection point between the hydraulic cylinder and the rear body. is the initial length of the hydraulic cylinder;

[0128] Based on the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , calculate the feedback error , specifically expressed by the following formula:

[0129] ;

[0130] in, is the physical limit of the hinge angle.

[0131] Furthermore, the present invention calculates the feedback error in real time, combined with nonlinear proportional, integral and differential controllers, to dynamically generate a steering valve opening instruction.

[0132] Step 10: Based on the feedback error , calculate the proportional term of the controller , integral item and nonlinear differential terms , and then calculate the output signal of the controller, the output signal of the controller Used to adjust the opening of the steering valve in the hydraulic system.

[0133] Step 10.1: Based on the feedback error , calculate the proportional term of the controller , which is specifically achieved through the following formula:

[0134] ;

[0135] in, is the proportional gain coefficient, is the saturation value of the proportional term, is a symbolic function;

[0136] The exponential decay term makes When the error is large (such as the initial error of the center-articulated scraper is large and it experiences external disturbances), it can saturate quickly, which helps the center-articulated scraper to quickly return to a steady state.

[0137] Step 10.2: Based on the feedback error , the integral term of the controller in the calculation , which is specifically achieved through the following formula:

[0138] ;

[0139] in, is the integral gain coefficient, The saturation value of the integral term;

[0140] Compared to The saturation characteristics of the hyperbolic tangent function are more gentle, which can suppress the control force during normal driving. Over-control when the error accumulation is too large (such as a center-hinged scraper driving on a path with large curvature) avoids oscillation caused by integral saturation and reduces overshoot.

[0141] Step 10.3: Based on the feedback error The differential of the controller is used to calculate the nonlinear differential term , which is specifically achieved through the following formula:

[0142] ;

[0143] in, is the differential gain coefficient, is the magnification, Feedback error The differential of

[0144] It has low sensitivity to noise and No saturation value is set, which allows for rapid increase in control effort when the error rate of change is large.

[0145] Step 10.4: Based on the proportional term , integral item and nonlinear differential terms , calculate the output signal of the controller , which is specifically achieved through the following formula:

[0146] ;

[0147] in, is the load The gain factor.

[0148] The key technical points of the present invention are:

[0149] 1. High-precision path tracking: Through precise lateral error calculation and adaptive preview distance adjustment, the center-articulated scraper can ensure that it can accurately follow the planned path.

[0150] 2. Strong real-time performance: The control method has low computational complexity, is suitable for rapid implementation in real-time control systems, and can adapt to rapidly changing working conditions.

[0151] 3. High robustness: The nonlinear control strategy effectively suppresses system oscillations. At the same time, the introduction of load gain coefficient and adaptive adjustment mechanism enhances the stability of the system under different load conditions and changing path environments.

[0152] The above description is merely an illustration of the preferred embodiments of the present disclosure and the technical principles employed. Those skilled in the art should understand that the scope of the invention encompassed by the embodiments of the present disclosure is not limited to technical solutions formed by specific combinations of the aforementioned technical features. It also encompasses other technical solutions formed by any combination of the aforementioned technical features or their equivalents, without departing from the aforementioned inventive concept. For example, a technical solution formed by replacing the aforementioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

Claims

1. A path tracking control method for a center-hinged scraper, characterized in that: include: Step 1: Using the onboard sensors configured on the center-articulated scraper, status information of the center-articulated scraper is collected, wherein the status information includes speed, front wheel center position, and rear wheel center position. The onboard sensors transmit the status information to the main controller; Step 2: In the main controller, determine the current state of the center-articulated scraper, which is expressed as: ； in, x Reference state position G The horizontal axis, y Reference state position G The vertical coordinate, is the orientation angle, is the hinge angle; Step 3: Get the reference path RP , the reference path RP It is composed of multiple discrete points. The points on the reference path are represented as: ； in, represents a point in the reference path, u is the reference path parameter, for The horizontal axis, for The vertical coordinate, U is the domain of the path parameter; Step 4: In the reference path RP On the reference state position G Corresponding reference path points ,in, Reference path point The horizontal axis, Reference path point The vertical coordinate, Reference path point Path parameters; Step 5: Calculate the reference state position G and reference waypoints The Euclidean distance between the reference state positions G and reference waypoints The Euclidean distance between , which is specifically achieved through the following formula: ； Step 6: Speed Based v and lateral error , dynamically adjust the preview distance, and then determine the preview point L , the preview point L is the position of the reference state at all points in the reference path G The distance is the preview distance point, reference state position G Point to preview point L The direction is the preview direction; Step 7: Get the desired state of the center hinge scraper , the desired state Expressed as: ； in, represents an expected articulation angle, which is the articulation angle corresponding to the instantaneous expected path of the center-articulated scraper passing through the preview point; Step 8: Calculate the angle between the center-hinged scraper's current direction of motion and its preview direction , and then calculate the desired state articulation angle Quantity ; Step 9: Calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , and then calculate the feedback error ; Step 10: Based on the feedback error , calculate the proportional term of the controller , integral item and nonlinear differential terms , and then calculate the output signal of the controller , the output signal of the controller Used to adjust the opening of the steering valve in the hydraulic system.

2. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: Step 2 specifically includes: In the main controller, according to the traveling state of the center-articulated scraper, one of the front wheel center posture and the rear wheel center posture is selected as the target center posture, and the target center posture determines the reference state position and orientation angle. , according to the center position of the front wheel and the center position of the rear wheel, determine the articulation angle , the articulation angle is the relative rotation angle between the front and rear bodies of the center-hinged scraper, with reference to the state position and orientation angle and articulation angle Make up the current state.

3. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: Step 4 specifically includes: Reference waypoints As unknown parameters, calculate the reference path points The tangent vector of , The components are expressed as: ； ； in, express The first derivative of express The first derivative of ; Based on the reference state position G and the tangent vector , construct the tangent equation, which is expressed as: ； in, Reference path point The tangent vector at ; Solve the tangent equation and get the solution set , in the solution set In the case of G The nearest point is used as a reference path point , in the solution set In the case of Upper selection and reference state position G The nearest point is used as a reference path point .

4. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: In step 6, based on speed v and lateral error , the dynamic adjustment of preview distance is realized by the following formula: ； in, Indicates preview distance. Used to adjust the sensitivity of preview distance changes. express The degree of influence on the preview distance, Represents the hinge angle The degree of impact on preview distance.

5. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: Step 8 specifically includes: Calculate the angle between the vehicle's current direction of movement and the preview direction , which is specifically achieved through the following formula: ； in, Reference state position G The y component of the coordinate, Reference state position G Coordinates x The weight, Reference state position G The orientation angle The weight; Since the instantaneous turning radius is the turning radius of the preceding vehicle, a geometric equation is constructed based on the geometric relationship. The geometric equation is expressed as follows: ； in, is the length of the front body of the center-hinged scraper, is the length of the rear body of the center-hinged scraper, is the desired state articulation angle The weight; The desired state articulation angle is calculated from the geometric equation Quantity .

6. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: Step 9 specifically includes: Calculate the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , which is specifically achieved through the following formula: ； in, is the length from the hinge point to the first connection point, where the first connection point is the connection point between the hydraulic cylinder and the front vehicle body, is the length from the hinge point to the second connection point, where the second connection point is the connection point between the hydraulic cylinder and the rear body. is the initial length of the hydraulic cylinder; Based on the relationship between the articulation angle and the extension and contraction of the hydraulic cylinder , calculate the feedback error , specifically expressed by the following formula: ； in, is the physical limit of the hinge angle.

7. The path tracking control method for a center-hinged scraper according to claim 1, characterized in that: Step 10 specifically includes: Step 10.1: Based on the feedback error , calculate the proportional term of the controller , which is specifically achieved through the following formula: ； in, is the proportional gain coefficient, is the saturation value of the proportional term, is a symbolic function; Step 10.2: Based on the feedback error , the integral term of the controller in the calculation , which is specifically achieved through the following formula: ； in, is the integral gain coefficient, The saturation value of the integral term; Step 10.3: Based on the feedback error The differential of the controller is used to calculate the nonlinear differential term , which is specifically achieved through the following formula: ； in, is the differential gain coefficient, is the magnification, Feedback error The differential of Step 10.4: Based on the proportional term , integral item and nonlinear differential terms , calculate the output signal of the controller , which is specifically achieved through the following formula: ； in, is the load The gain factor.

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