PID (Proportion Integration Differentiation) control method and system for realizing non-contact centering of vehicle

Abstract

A PID (Proportion Integration Differentiation) control method and system for realizing non-contact centering of a vehicle relates to the field of combined control of vehicle subsystems, and the method comprises the following steps: acquiring a real-time image of a current position of a target vehicle through an image acquisition device, and preprocessing the real-time image to obtain a vehicle contour feature map; vehicle feature point coordinates are extracted according to the vehicle contour feature map, a first coordinate deviation value between the vehicle feature point coordinates and preset target position coordinates is calculated, a vehicle correction instruction is obtained through calculation by adopting a PID controller according to the deviation value, and the PID controller comprises a proportionality coefficient, an integral coefficient and a differential coefficient; the vehicle correction instruction comprises a transverse displacement correction value and an angle correction value; the vehicle correction instruction is sent to an execution mechanism, and a second coordinate deviation value is obtained; and when the second coordinate deviation value is smaller than a preset coordinate threshold value, it is determined that vehicle centering operation is completed. By implementing the method, the mechanical wear during centering of the four-wheel positioning station of the automobile production line can be reduced.

Description

Technical Field

[0001] This application relates to the field of joint control of vehicle subsystems, and particularly to a PID control method and system for achieving non-contact vehicle centering. Background Art

[0002] With the continuous development of automobile manufacturing technology, the requirements for vehicle performance calibration before leaving the factory are increasing day by day. During the calibration processes such as advanced driver assistance systems and four-wheel alignment, it is necessary to accurately position the vehicle at the center position of the calibration equipment platform to ensure the accuracy of the calibration data. Therefore, as a key link in the calibration process, vehicle centering technology directly affects the reliability of the calibration results.

[0003] Currently, contact centering devices mainly driven by cylinders are commonly used in industrial sites. This device mainly consists of a cylinder and a push rod. The telescopic movement of the cylinder is controlled by a PLC controller, driving the push rod to contact the wheel and push the vehicle towards the center of the platform. In practical applications, this device adjusts the vehicle position through the mechanical movement of the cylinder and the push rod.

[0004] However, this contact centering method has problems of equipment wear during use. Since the push rod needs to directly contact the wheel, long-term use will cause wear on the surfaces of the push rod and the wheel, not only increasing the equipment maintenance cost but also possibly affecting the appearance quality of the vehicle. Summary of the Invention

[0005] This application provides a PID control method and system for achieving non-contact vehicle centering, which is used to reduce mechanical wear during centering at the four-wheel alignment station of the automobile production line.

[0006] In a first aspect, this application provides a PID control method for achieving non-contact vehicle centering, which is applied to a PID control system. The method includes: obtaining a real-time image of the current position of the target vehicle through an image acquisition device, and preprocessing the real-time image to obtain a vehicle contour feature map; extracting the coordinates of vehicle feature points according to the vehicle contour feature map, and calculating a first coordinate deviation value between the coordinates of the vehicle feature points and the preset target position coordinates, where the coordinate deviation value includes a lateral deviation and an angular deviation; calculating a vehicle correction instruction using a PID controller according to the deviation value, the PID controller includes a proportional coefficient, an integral coefficient, and a differential coefficient, and the vehicle correction instruction includes a lateral displacement correction amount and an angular correction amount; sending the vehicle correction instruction to an actuator, and obtaining a second coordinate deviation value; when the second coordinate deviation value is less than a preset coordinate threshold, it is determined that the vehicle centering operation is completed.

[0007] In the above embodiments, the vehicle real-time position information is obtained by using an image acquisition device, and the feature point coordinates are extracted. The lateral deviation and the angular deviation are input into a PID controller for calculation. The PID controller generates accurate correction instructions based on these deviation values and controls the actuator for non-contact adjustment. Throughout the process, new deviation values are continuously obtained and corrected through closed-loop control until a preset threshold is reached, achieving high-precision vehicle centering positioning and avoiding wear problems caused by mechanical contact.

[0008] Combined with some embodiments of the first aspect, in some embodiments, the step of calculating the vehicle correction instruction by using a PID controller according to the deviation value specifically includes: taking the lateral deviation value as the input of the lateral PID controller and adjusting the parameters of the lateral PID controller according to the absolute value of the lateral deviation value; taking the angular deviation value as the input of the angular PID controller and adjusting the parameters of the angular PID controller according to the absolute value of the angular deviation value; calculating the PID control output value according to the lateral deviation value and the angular deviation value, and performing amplitude limiting processing on the PID control output value to obtain the vehicle correction instruction.

[0009] In the above embodiments, the lateral deviation and the angular deviation are respectively input into the corresponding PID controllers, and the control parameters are dynamically adjusted according to the magnitudes of the deviation values. The lateral PID controller and the angular PID controller work together to output the correction instruction after amplitude limiting processing. This separate control strategy enables the system to handle position and direction deviations simultaneously, improving the stability and accuracy of the centering process and reducing mutual interference.

[0010] Combined with some embodiments of the first aspect, in some embodiments, the step of taking the lateral deviation value as the input of the lateral PID controller and adjusting the parameters of the lateral PID controller according to the absolute value of the lateral deviation value specifically includes: when the absolute value of the lateral deviation value is greater than a preset first threshold, using the first PID parameter for control; when the absolute value of the lateral deviation value is not greater than the preset first threshold and not less than a preset second threshold, using the second PID parameter for control; when the absolute value of the lateral deviation value is less than the preset second threshold, using the third PID parameter for control. The proportional coefficient of the first PID parameter is greater than the proportional coefficient of the second PID parameter, the proportional coefficient of the second PID parameter is greater than the proportional coefficient of the third PID parameter, the integral coefficient of the third PID parameter is greater than the integral coefficient of the second PID parameter, the integral coefficient of the second PID parameter is greater than the integral coefficient of the first PID parameter, and the differential coefficients of the first PID parameter and the third PID parameter are greater than the differential coefficient of the second PID parameter.

[0011] In the above embodiments, the lateral PID controller automatically switches three different parameter combinations according to the magnitude of the deviation value. When the deviation is large, a larger proportional coefficient is adopted for rapid response; when the deviation is moderate, a balanced parameter combination is adopted; when the deviation is small, the integral coefficient is increased to improve the accuracy. This phased parameter adjustment mechanism achieves a balance between rapid approach and precise positioning, improving the centering efficiency while ensuring the control accuracy.

[0012] In combination with some embodiments of the first aspect, in some embodiments, the step of using the angle deviation value as the input of the angle PID controller and adjusting the parameters of the angle PID controller according to the absolute value of the angle deviation value specifically includes: when the absolute value of the angle deviation value is greater than a preset third threshold, the fourth PID parameter is used for control; when the absolute value of the angle deviation value is not greater than the preset third threshold and not less than a preset fourth threshold, the fifth PID parameter is used for control; when the absolute value of the angle deviation value is less than the preset fourth threshold, the sixth PID parameter is used for control; wherein, the proportional coefficient of the fourth PID parameter is greater than the proportional coefficient of the fifth PID parameter, the proportional coefficient of the fifth PID parameter is greater than the proportional coefficient of the sixth PID parameter; the integral coefficient of the sixth PID parameter is greater than the integral coefficient of the fifth PID parameter, the integral coefficient of the fifth PID parameter is greater than the integral coefficient of the fourth PID parameter; the differential coefficient of the fourth PID parameter is greater than the differential coefficient of the fifth PID parameter, and the differential coefficient of the fourth PID parameter is greater than the differential coefficient of the sixth PID parameter.

[0013] In the above embodiments, the angle PID controller automatically switches between three control stages according to the magnitude of the angle deviation. In the large deviation stage, large proportional and differential coefficients are adopted to ensure the rapid angle adjustment ability; in the medium deviation stage, a balanced parameter configuration is adopted; in the small deviation stage, the integral coefficient is increased and the proportional coefficient is decreased to achieve precise angle positioning. This segmented parameter adjustment strategy makes the angle control both rapid and accurate, improving the dynamic performance of the system.

[0014] In combination with some embodiments of the first aspect, in some embodiments, after the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than the preset coordinate threshold, the method further includes: according to the difference in the front and rear weight distributions of the vehicle, applying the lateral deviation value and the angle deviation value to the front wheel control and the rear wheel control respectively, the proportional coefficient and the integral coefficient of the front wheel PID controller are greater than the proportional coefficient and the integral coefficient of the rear wheel PID controller, the differential coefficient of the rear wheel PID controller is greater than the differential coefficient of the front wheel PID controller, and the parameters of the front wheel PID controller and the rear wheel PID controller are obtained through the self-tuning function of the PLC.

[0015] In the above embodiments, different PID control strategies are applied to the front wheels and the rear wheels respectively according to the weight distribution characteristics of the vehicle front and rear. The front wheel controller adopts larger proportional and integral coefficients to ensure fast response and stability; the rear wheel controller adopts a larger differential coefficient to enhance the damping characteristics of the system. The optimal parameters are obtained through PLC self-tuning, realizing the coordinated control of the front and rear wheels and improving the smoothness and accuracy of the vehicle centering.

[0016] Combined with some embodiments of the first aspect, in some embodiments, after the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than the preset coordinate threshold, the method further includes: based on the condition that the left front camera and the right front camera are respectively set at equal distances x1 and x2 from the central axis, the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera are collected in real time; calculate the distance s1 from the left front wheel to the central axis as s1 = x1 - y1, and calculate the distance s2 from the right front wheel to the central axis as s2 = x2 - y2; calculate the deviation value Δs = s1 - s2. When y1 = y2, that is, Δs = 0, it means that the wheels are in the central position of the floating plate.

[0017] In the above embodiments, based on the characteristic that the left and right front cameras are arranged at equal distances, the deviation value of the wheels from the central axis is calculated by measuring the distance from the wheels to the cameras in real time. When the distances from the left and right wheels to the central axis are equal, it can be accurately determined that the vehicle is in the central position. This two-way distance measurement method establishes an accurate mathematical relationship of the wheel positions, provides a reliable criterion for judging the completion of centering, and enhances the accuracy of positioning.

[0018] Combined with some embodiments of the first aspect, in some embodiments, after the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than the preset coordinate threshold, the method further includes: when the floating plate and the moving platform are perpendicular, calibrate the zero point of the absolute encoder of the servo motor, divide the displacement of the motion module into positive and negative parts, and when y1 = y2, the position of the servo motor is 0; in the state where the vehicle is in neutral gear, control the speeds of all the rollers on the floating plate to be consistent, so that when the left front motion module moves to the left, the front wheels move to the left synchronously, and when the left rear motion module moves to the right, the rear wheels move to the right synchronously.

[0019] In the above embodiments, a zero point reference of the servo motor encoder is established at the vertical position of the floating plate and the moving platform, and the motion stroke is divided into positive and negative intervals. The system controls the motion module according to the distance values from the left and right wheels to the cameras, realizing the differential motion of the front wheels moving to the left and the rear wheels moving to the right. This differential control mechanism based on zero point calibration ensures the synchronous and coordinated motion of the front and rear wheels, avoids wheel slippage, makes the centering process more stable and controllable, and improves the accuracy and stability of adjustment.

[0020] Second aspect, embodiments of the present application provide a PID control system, which includes: one or more processors and a memory; the memory is coupled to the one or more processors, and the memory is used to store computer program code, and the computer program code includes computer instructions. The one or more processors call the computer instructions to cause the PID control system to execute the methods described in the first aspect and any possible implementation manner in the first aspect.

[0021] Third aspect, embodiments of the present application provide a computer program product containing instructions. When the computer program product runs on a PID control system, it causes the PID control system to execute the methods described in the first aspect and any possible implementation manner in the first aspect.

[0022] Fourth aspect, embodiments of the present application provide a computer-readable storage medium, including instructions. When the instructions run on a PID control system, it causes the PID control system to execute the methods described in the first aspect and any possible implementation manner in the first aspect.

[0023] It can be understood that the PID control system provided in the second aspect, the computer program product provided in the third aspect, and the computer storage medium provided in the fourth aspect are all used to execute the methods provided in the embodiments of the present application. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding methods, and will not be elaborated here.

[0024] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: 1. In the present application, the vehicle real-time position information is obtained by using an image acquisition device and the feature point coordinates are extracted, and the lateral deviation and the angular deviation are input into the PID controller for calculation. The PID controller generates accurate correction instructions based on these deviation values and controls the actuator for non-contact adjustment. Throughout the process, new deviation values are continuously obtained and corrected through closed-loop control until a preset threshold is reached, achieving high-precision vehicle centering positioning and avoiding wear problems caused by mechanical contact.

[0025] 2. In the present application, the lateral deviation and the angular deviation are respectively input into the corresponding PID controllers, and the control parameters are dynamically adjusted according to the magnitudes of the deviation values. The lateral PID controller and the angular PID controller work together to output correction instructions after amplitude limiting processing. This separate control strategy enables the system to handle position and direction deviations simultaneously, improving the stability and accuracy of the centering process and reducing mutual interference.

[0026] 3. In this application, the lateral deviation and the angular deviation are respectively input into the corresponding PID controllers, and the control parameters are dynamically adjusted according to the magnitude of the deviation values. The lateral PID controller and the angular PID controller work together to output a corrected command after amplitude limiting processing. This separate control strategy enables the system to handle the deviations in both position and direction simultaneously, improving the stability and accuracy of the centering process and reducing mutual interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic flowchart of a PID control method for realizing non-contact centering of a vehicle in an embodiment of this application; Figure 2 is a schematic diagram of the hardware structure of a PID control method for realizing non-contact centering of a vehicle in an embodiment of this application; Figure 3 is another schematic flowchart of a PID control method for realizing non-contact centering of a vehicle in an embodiment of this application; Figure 4 is a schematic diagram of the structure of an entity device of a PID control system in an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The terms used in the following embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification of this application, the singular forms "a", "one kind", "the above", "the" and "this" are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term " / and" used in this application refers to any or all possible combinations including one or more of the listed items.

[0029] Hereinafter, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as implying or suggesting relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of this application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0030] For ease of understanding, the method provided in this embodiment is described in terms of a process below. Please refer to Figure 1 , which is a schematic flowchart of a PID control method for realizing non-contact centering of a vehicle in an embodiment of this application.

[0031] S101. Obtain a real-time image of the current position of the target vehicle through an image acquisition device, and preprocess the real-time image to obtain a vehicle contour feature map.

[0032] Among them, the image acquisition device refers to an industrial camera device for acquiring images, including a left front camera, a right front camera, a left rear camera, and a right rear camera, which are fixedly installed on the centering platform and are symmetrically distributed at equal distances from the platform central axis; the real-time image refers to the vehicle image data captured by the industrial camera in real time; the vehicle contour feature map refers to a binary image containing the vehicle external contour obtained after image preprocessing.

[0033] This step starts to execute after the vehicle completely enters the centering platform and stops moving. Specifically, the four industrial cameras synchronously align with the vehicle for real-time shooting to collect the original images containing vehicle position information. The collected original images are preprocessed, including image enhancement to improve image quality, noise elimination to remove interference information, edge detection to highlight the vehicle contour, etc., and finally a clear vehicle contour feature map is obtained to prepare for subsequent feature point extraction.

[0034] In some embodiments, image acquisition and preprocessing can be achieved in the following ways: Optionally, first detect the camera working state and configure parameters, including setting the exposure time, gain value, etc.; then synchronously trigger the four cameras for image acquisition; perform grayscale processing on the original images to convert them into 8-bit grayscale images; use Gaussian filtering for noise elimination; finally use the Canny operator for edge detection to obtain the contour feature map. Optionally, first calibrate the camera to eliminate distortion; collect multiple images with different exposures in HDR mode and synthesize them; perform adaptive histogram equalization enhancement on the images; use morphological operations for image denoising; use the Sobel operator to extract edges to obtain the contour feature map. It can be understood that other image acquisition and preprocessing methods can also be used to obtain the vehicle contour feature map, which is not limited here.

[0035] In this vehicle non-contact centering system, the image acquisition device is equivalent to the sensor in the PID control system. The vehicle position information collected by it (presented in the form of images) will be subsequently converted into data related to the vehicle position, used to calculate the deviation value, and further provide the input basis for PID control.

[0036] S102. Extract the vehicle feature point coordinates according to the vehicle contour feature map, and calculate the first coordinate deviation value between the vehicle feature point coordinates and the preset target position coordinates. This coordinate deviation value includes the lateral deviation and the angular deviation.

[0037] Among them, the vehicle feature point coordinates refer to the spatial coordinates of the key points that can represent the vehicle position, mainly including the coordinates of the wheel center points; the preset target position coordinates refer to the standard coordinates of the ideal parking position of the vehicle on the centering platform; the coordinate deviation value refers to the difference between the actual position and the target position, including two components: the vehicle lateral displacement deviation and the vehicle body angular deviation.

[0038] This step is executed after obtaining the vehicle contour feature map. Specifically, the contour feature map is analyzed and processed to extract the coordinate values of the feature points that can characterize the vehicle position, mainly the coordinate values of the center points of the four wheels. The extracted coordinate values of the feature points are compared and calculated with the pre-calibrated target position coordinate values to obtain the deviation values in the horizontal and angular directions. Among them, the horizontal deviation is calculated through the difference in the coordinate values of the feature points at the left and right symmetric positions, and the angular deviation is calculated through the included angle between the line connecting the front and rear feature points and the central axis.

[0039] In some embodiments, the feature point extraction and deviation calculation can be achieved in the following ways: Optionally, first perform connected component analysis on the contour feature map to identify the wheel areas; then calculate the centroid of each connected component to obtain the coordinate values of the wheel center points; calculate the horizontal deviation s = |x1 - x2| based on the coordinate values obtained from the left and right symmetric cameras; calculate the angular deviation θ = arctan((y2 - y1) / (x2 - x1)) based on the coordinate values obtained from the front and rear cameras. Optionally, use the template matching method to locate the wheel positions; use the Hough circle transform to extract the coordinates of the wheel centers; fit the vehicle central axis by the least squares method; calculate the translation amount between the central axis and the standard position to obtain the horizontal deviation; calculate the included angle between the central axis and the standard position to obtain the angular deviation. It can be understood that other feature extraction and coordinate calculation methods can also be used to obtain the vehicle position deviation value, which is not limited here.

[0040] Let the distance from the left front camera to the central axis be x 前左定 , and the value of the distance to the left front wheel collected in real time be y 前左实 , the distance from the right front camera to the central axis be x 前右定 , and the value of the distance to the right front wheel collected in real time be y 前右实 (similarly for the rear cameras).

[0041] When calculating the horizontal deviation, taking the left and right front wheels as an example, if only considering the horizontal position relationship, its horizontal deviation e 横前 (here e 横前 is a quantity related to the deviation in PID control) can be expressed as: e 横前 = (x 前左定 - y 前左实 ) - (x 前右定 - y 前右实 ), when x 前左定 = x 前右定 , e 横前 = y 前右实 - y 前左实 . This horizontal deviation e 横前 (and the e 横后 calculated similarly for the rear side) will be used as part of the input deviation of the PID controller for calculating the vehicle's horizontal correction command later.

[0042] S103. Calculate the vehicle correction command using a PID controller based on the deviation value. The PID controller includes a proportional coefficient, an integral coefficient, and a derivative coefficient. The vehicle correction command includes a lateral displacement correction amount and an angle correction amount.

[0043] Among them, the PID controller refers to an automatic controller that includes three control actions: proportional, integral, and derivative. The proportional coefficient is a parameter used to adjust the response speed of the controller to the deviation. The integral coefficient is a parameter used to eliminate the steady-state error. The derivative coefficient is a parameter used to improve the dynamic performance of the system. The lateral displacement correction amount is the displacement amount output by the controller for correcting the vehicle's lateral deviation. The angle correction amount is the rotation amount output by the controller for correcting the vehicle's angle deviation.

[0044] This step is executed after obtaining the vehicle position deviation value. Specifically, the system controls the front wheels and rear wheels using PID controllers with different parameters according to the difference in the front and rear weight distributions of the vehicle. For the front-wheel PID controller, since the front part of the vehicle is heavier, its proportional coefficient and integral coefficient need to be greater than the corresponding parameters of the rear-wheel PID controller. The derivative coefficient of the rear-wheel PID controller is greater than that of the front-wheel PID controller to ensure the smoothness of the control process. The controller outputs the corresponding correction command through PID operation based on the input lateral deviation and angle deviation.

[0045] In some embodiments, the calculation of the correction command of the PID controller can be implemented in various ways: Optionally, first input the lateral deviation to the lateral PID controller, select different PID parameter combinations according to the deviation magnitude, use a larger proportional coefficient and a smaller integral coefficient when the deviation is large, and use a smaller proportional coefficient and a larger integral coefficient when the deviation is small; then input the angle deviation to the angle PID controller for similar processing; finally, perform a weighted combination of the outputs of the two controllers to obtain the final correction command. Optionally, use the PID self-tuning function of the PLC, obtain the optimal PID parameters through multiple tests; input the lateral deviation and angle deviation to the corresponding PID modules respectively; perform a limit processing on the PID output to ensure safety; finally, convert the processed output into specific displacement and angle correction amounts. It can be understood that other control algorithms can also be used to implement the correction calculation of the vehicle position, which is not limited here.

[0046] In a digital PID control system, a discretized PID control algorithm is usually adopted. The formula of the position-type PID control algorithm is: U(k)=K_P*e(k)+K_I*∑(i = 0 to k)e(i)+K_D*[e(k)-e(k - 1)], where U(k) is the output of the PID controller at the k-th sampling moment; e(k) is the deviation value at the k-th sampling moment; e(k - 1) is the deviation value at the (k - 1)-th sampling moment. The formula of the incremental PID control algorithm is: ΔU(k)=K_P*[e(k)-e(k - 1)]+K_I*e(k)+K_D*[e(k)-2*e(k - 1)+e(k - 2)], where ΔU(k) is the output increment at the k-th sampling moment.

[0047] In this system, the lateral deviation e 横(k) and the angular deviation e 角(k) are respectively input into the corresponding PID controllers for calculation. For the lateral PID controller, the position-type PID algorithm is used to calculate the lateral displacement correction amount U 横 (k): U 横 (k)=K P横 *e 横 (k)+K I横 *∑(i = 0 to k)e 横 (i)+K D横 *[e 横 (k)-e 横 (k - 1)], for the angular PID controller, the position-type PID algorithm is used to calculate the angular correction amount U 角 (k): U 角 (k)=K P角 *e 角 (k)+K I角 *∑(i = 0 to k)e 角 (i)+K D角 *[e 角 (k)-e 角 (k - 1)].

[0048] S104. Send the vehicle correction instruction to the actuator and obtain the second coordinate deviation value.

[0049] Among them, the actuator refers to the servo motor and its related mechanical components used to execute the correction instruction; the second coordinate deviation value refers to the vehicle position deviation value re-measured after the correction action is executed.

[0050] This step is executed after the correction instruction is calculated. Specifically, the lateral displacement correction amount and the angle correction amount are converted into motion control instructions for the servo motor and sent to the corresponding actuator through the communication interface. The left front motion module controls the front wheels to move left, and the left rear motion module controls the rear wheels to move right, and the position adjustment is synchronously performed when the vehicle is in neutral gear. After the adjustment is completed, the system re-obtains the vehicle position information through the image acquisition device and calculates a new coordinate deviation value.

[0051] In some embodiments, the execution of the correction instruction and the acquisition of the deviation can be achieved in various ways: Optionally, first convert the correction instruction into a position control instruction for the servo motor; control the servo motor to run to the specified position according to the set acceleration and speed; trigger the camera to perform image acquisition after the movement is completed; calculate the updated deviation value based on the newly acquired image. Optionally, convert the correction amount into a displacement instruction for the motion module through the PLC; monitor the operating state of the servo motor to ensure safety; acquire new position information after the movement is completed and the system is stable; calculate the updated lateral deviation and angle deviation values. It can be understood that other methods can also be used to implement the execution of the correction instruction and the update of the deviation value, which are not limited herein.

[0052] When sending the vehicle correction instruction to the actuator, clearly use the previously calculated lateral displacement correction amount U 横 (k) and the angle correction amount U 角 (k). After the adjustment is completed, the system re-obtains the vehicle position information through the image acquisition device and calculates a new coordinate deviation value according to the method in S102, that is, the second coordinate deviation value. The new lateral deviation is denoted as e 横新 (k + 1) and the angle deviation is denoted as e 角新 (k + 1). These two new deviation values will be used as the input for the next PID control calculation to continue adjusting the vehicle position until the centering condition is met.

[0053] S105. When the second coordinate deviation value is less than the preset coordinate threshold, it is determined that the vehicle centering operation is completed.

[0054] Among them, the preset coordinate threshold refers to the maximum position deviation value allowed by the system, which is used to determine whether the vehicle has completed the centering operation; the second coordinate deviation value refers to the vehicle position deviation value measured after the correction action is performed, including the new lateral deviation and angle deviation; the vehicle centering operation refers to the process of making the vehicle stop at the center position of the centering platform through the control system.

[0055] This step is executed after obtaining the second coordinate deviation value. Specifically, the system records the equal distances from the left front camera and the right front camera to the central axis as x1 and x2 respectively, and real-time collects the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera. Calculate the distance s1 from the left front wheel to the central axis as s1 = x1 - y1, calculate the distance s2 from the right front wheel to the central axis as s2 = x2 - y2, and obtain the deviation value Δs = s1 - s2. When y1 = y2, that is, Δs = 0, it means that the wheel is at the center position of the floating tray, and the system determines that the centering operation is completed.

[0056] In some embodiments, the judgment of centering completion can be achieved in various ways: Optionally, first substitute the obtained y1 and y2 values into the formula to calculate s1 and s2; then calculate the difference Δs and compare it with a preset threshold; if Δs is less than the threshold, send a centering completion signal to the PLC; at the same time, compare the servo motor position value with the zero point for confirmation; finally, output the centering completion status and stop the operation of relevant devices. Optionally, calculate the absolute values of the lateral deviation and the angular deviation respectively; compare the two deviation values with their respective preset thresholds; when both deviation values are less than the threshold, it is determined that centering is completed; the system records the final position parameters and locks the position; the controller switches to the waiting state to prepare for the next centering. It can be understood that other ways can also be used to achieve the judgment of centering completion status, which is not limited here.

[0057] Combined with the relevant content of PID control, when judging centering completion, not only the currently measured coordinate deviation needs to be considered, but also the stability of PID control needs to be combined. After the vehicle reaches a position deviation less than the preset threshold, it is necessary to continuously monitor for a certain period of time (such as several sampling periods) to ensure that the deviation remains within the threshold range during this period and prevent misjudgment caused by system fluctuations. For example, for n consecutive sampling periods (n can be set according to the actual system stability, generally taking values of 3 - 5), the lateral deviation e 横新 (k + j) (j = 1, 2,..., n) and the angular deviation e 角新 (k + j) are both less than their respective preset thresholds e lateral threshold and e angular threshold, and then it is finally determined that the centering operation is completed. In actual calculation, in addition to using the camera to measure the distance to calculate the deviation, the position information fed back by the servo motor encoder can also be combined for further confirmation. Assume that the theoretical position of the movement module driven by the servo motor is P theory, and the actual feedback position is P actual. When judging centering, it is necessary to ensure that |P theory - P actual| is less than the error range P error allowed by the motor position accuracy, and at the same time meet the condition that the coordinate deviation is less than the threshold, so as to enhance the accuracy of centering judgment.

[0058] The following further analyzes the hardware structure and components of the method provided in this embodiment. Please refer to Figure 2 , which is the hardware structure diagram for implementing the PID control method for non-contact centering of vehicles in the embodiments of this application.

[0059] In Figure 2 it, part (a) is the overall architecture of the centering platform for realizing non-contact vehicle centering. There are 4 single-wheel centering components in the centering platform. The 4 single-wheel centering components are symmetrically distributed at equal distances from the center line of the centering platform. Among them, the two floating disks in the lower left part respectively carry the left front wheel and the left rear wheel, and the two floating disks in the upper right part respectively carry the right front wheel and the right rear wheel.

[0060] Part (b) is the single-wheel centering component. ① are red cameras, two pairs in total, fixed symmetrically at equal distances from the center line of the centering platform, used to measure the distance from the camera to the wheel. ② are floating turntables, 4 in total, symmetrically distributed at equal distances from the platform center line, carrying the wheels and their steering. The two floating disks in the lower left part carry the left front and rear wheels, including parts ④ and ⑤; the two floating disks in the upper right part carry the right front and rear wheels, only ④, which is the driven floating disk of the left wheel floating disk. ③ is a swing mechanism, composed of ⑥, ⑦, and ⑧, driving the wheels on the floating disk to move left and right. The two floating disks in the upper right part do not have this structure. ④ are rollers, two for each floating disk, with the wheel located between them, assisting the wheel to move left and right. ⑤ is the end of the floating disk, connecting the swing mechanism. ⑥ is a motion module, connecting ⑤, locking the floating disk and driving it to move left and right. ⑦ is the motion platform of ⑥. When ② is perpendicular to ③, its length is evenly divided. ⑧ is a servo motor, providing power and position control capabilities for the centering function, with an absolute encoder.

[0061] Next, a further and more specific process description of the method provided in this embodiment will be given. Please refer to Figure 3 which is another process schematic diagram of the PID control method for realizing non-contact vehicle centering in the embodiment of the present application.

[0062] S301. Obtain a real-time image of the current position of the target vehicle through an image acquisition device, and preprocess the real-time image to obtain a vehicle contour feature map.

[0063] The image acquisition device refers to four industrial cameras fixedly installed on the centering platform, including the left front camera, the right front camera, the left rear camera, and the right rear camera; the real-time image refers to the vehicle image data captured by the industrial camera in real time; the vehicle contour feature map refers to a binary image containing the outer contour of the vehicle obtained after image preprocessing. After the vehicle completely enters the centering platform, the four industrial cameras synchronously align with the vehicle and perform real-time shooting to collect the original image. The collected original image is preprocessed, including image enhancement to improve the image quality, noise elimination to remove interference information, edge detection to highlight the vehicle contour, etc. The image is converted into an 8-bit grayscale image through grayscale processing, Gaussian filtering is used for noise elimination, and the Canny operator is used for edge detection, and finally a clear vehicle contour feature map is obtained, preparing for subsequent feature point extraction.

[0064] S302. Extract the vehicle feature point coordinates from the vehicle contour feature map, and calculate the first coordinate deviation value between the vehicle feature point coordinates and the preset target position coordinates. This coordinate deviation value includes the lateral deviation and the angular deviation.

[0065] The vehicle feature point coordinates represent the spatial position information of the wheel center point; the preset target position coordinates refer to the ideal parking position of the vehicle on the centering platform; the coordinate deviation value represents the difference between the actual position and the target position. After obtaining the vehicle contour feature map, perform connected component analysis on the image to identify the wheel area, and calculate the centroid of each connected component to obtain the wheel center point coordinates. Calculate the lateral deviation based on the coordinate values obtained by the left and right symmetric cameras. Specifically, calculate the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera, and obtain s1 = x1 - y1 and s2 = x2 - y2, where x1 and x2 are the distances from the cameras to the central axis. The lateral deviation is Δs = s1 - s2. The angular deviation is obtained by calculating the angle θ = arctan((y2 - y1) / (x2 - x1)) between the line connecting the front and rear wheels and the central axis.

[0066] S303. When the absolute value of the lateral deviation value is greater than the preset first threshold, control is performed using the first PID parameters.

[0067] The lateral deviation value represents the distance difference between the actual lateral position of the vehicle and the target position; the preset first threshold is the standard value for judging the magnitude of the lateral deviation; the first PID parameters are the control parameter group for large deviation correction. When the absolute value of the calculated lateral deviation value is greater than the preset first threshold, it indicates that the vehicle position deviates far from the target, and a larger control force is required for correction. At this time, the first PID parameter group is selected for control. The characteristics of this parameter group are that the proportional coefficient is relatively large to provide a strong correction force, the integral coefficient is relatively small to avoid large cumulative errors, and the differential coefficient is relatively large to provide sufficient dynamic response ability. Through the cooperation of this group of parameters, it is ensured that the vehicle can be quickly adjusted to near the target position under large deviation conditions.

[0068] S304. When the absolute value of the lateral deviation value is not greater than the preset first threshold and not less than the preset second threshold, control is performed using the second PID parameters.

[0069] The lateral deviation value represents the distance difference between the actual lateral position of the vehicle and the target position; the preset first threshold and the preset second threshold are respectively the upper limit and the lower limit for judging that the lateral deviation is in the medium range; the second PID parameter refers to the control parameter group for medium deviation correction. When the absolute value of the calculated lateral deviation value is between the first threshold and the second threshold, it indicates that the vehicle position is in the transition region and a moderate control force is required for correction. At this time, the second PID parameter group is selected for control. The characteristics of this parameter group are that the proportional coefficient is moderate to provide an appropriate correction force, the integral coefficient is moderate to gradually eliminate the steady-state error, and the differential coefficient is small to ensure the stability of the system. Through the cooperation of this group of parameters, the vehicle approaches the target position smoothly.

[0070] S305. When the absolute value of the lateral deviation value is less than the preset second threshold, the third PID parameter is used for control. The proportional coefficient of the first PID parameter is greater than that of the second PID parameter, the proportional coefficient of the second PID parameter is greater than that of the third PID parameter, the integral coefficient of the third PID parameter is greater than that of the second PID parameter, the integral coefficient of the second PID parameter is greater than that of the first PID parameter, and the differential coefficients of the first PID parameter and the third PID parameter are greater than that of the second PID parameter.

[0071] The preset second threshold refers to the standard value for judging that the lateral deviation is small; the third PID parameter refers to the control parameter group for precise correction of small deviations. To achieve the optimal control effect under different deviation ranges, the magnitude relationships of the three groups of PID parameters are clearly defined: the proportional coefficient decreases in the order of the first group > the second group > the third group, the integral coefficient decreases in the order of the third group > the second group > the first group, and the differential coefficients of the first group and the third group are greater than that of the second group. When the absolute value of the lateral deviation value is less than the second threshold, it indicates that the vehicle has approached the target position. At this time, the third PID parameter group is used for precise control. The characteristics of the third group of parameters are that the proportional coefficient is the smallest to avoid overcorrection, the integral coefficient is the largest to eliminate small steady-state errors, and the relatively large differential coefficient is used to provide sufficient dynamic response to ensure that the vehicle can accurately stop at the target position.

[0072] S306. When the absolute value of the angle deviation value is greater than the preset third threshold, the fourth PID parameter is used for control.

[0073] The angular deviation value represents the angle between the vehicle axis and the axis of the standard position; the preset third threshold is the standard value for judging a large angular deviation; the fourth PID parameter is a control parameter group for large angular deviation correction. When the absolute value of the calculated angular deviation value is greater than the preset third threshold, it indicates that there is a large angular deviation between the vehicle and the standard position, and a large-amplitude angular correction is required. At this time, the fourth PID parameter group is selected for control. The characteristics of this parameter group are that the proportional coefficient is the largest to provide a strong correction force, the integral coefficient is the smallest to avoid large cumulative errors, and the differential coefficient is the largest to provide fast dynamic response capabilities. Through the cooperation of this group of parameters, it is ensured that the vehicle can be quickly adjusted to a near-standard angle under large angular deviation conditions.

[0074] S307. When the absolute value of the angular deviation value is not greater than the preset third threshold and not less than the preset fourth threshold, the fifth PID parameter is used for control.

[0075] The angular deviation value represents the angle between the vehicle axis and the axis of the standard position; the preset third threshold and the preset fourth threshold are respectively the upper and lower limits for judging that the angular deviation is in the medium range; the fifth PID parameter is a control parameter group for medium angular deviation correction. When the absolute value of the calculated angular deviation value is between the third threshold and the fourth threshold, it indicates that the vehicle angle is in the transition region and a moderate control force is required for correction. At this time, the fifth PID parameter group is selected for control. The characteristics of this parameter group are that the proportional coefficient is moderate to provide an appropriate correction force, the integral coefficient is moderate to gradually eliminate the steady-state error, and the differential coefficient is small to ensure the stability of the system. Through the cooperation of this group of parameters, the vehicle angle is adjusted smoothly towards the standard angle.

[0076] S308. When the absolute value of the angular deviation value is less than the preset fourth threshold, the sixth PID parameter is used for control. The proportional coefficient of the fourth PID parameter is greater than that of the fifth PID parameter, and the proportional coefficient of the fifth PID parameter is greater than that of the sixth PID parameter; the integral coefficient of the sixth PID parameter is greater than that of the fifth PID parameter, and the integral coefficient of the fifth PID parameter is greater than that of the fourth PID parameter; the differential coefficient of the fourth PID parameter is greater than that of the fifth PID parameter, and the differential coefficient of the fourth PID parameter is greater than that of the sixth PID parameter.

[0077] The preset fourth threshold refers to the standard value for judging a small angle deviation; the sixth PID parameter refers to the control parameter group for precise correction of small angle deviations. When the absolute value of the angle deviation value is less than the fourth threshold, it indicates that the vehicle angle has approached the standard position. At this time, the sixth PID parameter group is used for precise control. The characteristics of the sixth group of parameters are that the proportional coefficient is the smallest to avoid overcorrection, the integral coefficient is the largest to eliminate small steady-state errors, and the smaller differential coefficient is used to provide a smooth dynamic response to ensure that the vehicle can accurately align with the standard angle. At this stage, the system mainly focuses on the precise adjustment of the angle to avoid the back-and-forth swing caused by overcorrection.

[0078] The fourth, fifth, and sixth PID parameter groups respectively correspond to the control parameters for large, medium, and small angle deviation ranges. The size relationship settings of these three groups of parameters follow the following rules: the proportional coefficient decreases in the order of the fourth group > the fifth group > the sixth group, so as to provide a strong correction force when the angle deviation is large and gradually reduce the correction force as the deviation decreases; the integral coefficient decreases in the order of the sixth group > the fifth group > the fourth group, so as to provide a strong steady-state error elimination ability when approaching the target angle; the differential coefficient of the fourth group is the largest and is greater than the fifth group and the sixth group, so as to provide a fast dynamic response when the angle deviation is large and reduce the response speed when the deviation is medium and small to ensure stability. Through this parameter configuration, the optimal control effect in different angle deviation ranges is achieved.

[0079] S309. Calculate the PID control output value according to the lateral deviation value and the angle deviation value, and perform a limiting process on the PID control output value to obtain a vehicle correction instruction. This PID controller includes a proportional coefficient, an integral coefficient, and a differential coefficient. This vehicle correction instruction includes a lateral displacement correction amount and an angle correction amount.

[0080] The PID control output value represents the original control amount calculated by the controller according to the deviation; the limiting process refers to the process of limiting the control amount exceeding the safe range within the allowable range; the vehicle correction instruction refers to the instruction signal that can be directly used to control the actuator after being processed. The lateral PID controller calculates the lateral deviation using the selected parameter group, where the proportional term output is Kpe(t), the integral term output is Ki∫e(t)dt, and the derivative term output is Kd*de(t) / dt, and e(t) is the lateral deviation value. The angle PID controller performs a similar calculation on the angle deviation. Compare the output values of the two controllers with the preset limit values respectively. When the output exceeds the limit value, limit it within the safe range. The finally obtained lateral displacement correction amount and angle correction amount constitute a complete vehicle correction instruction.

[0081] S310. Send the vehicle correction instruction to the actuator and obtain the second coordinate deviation value.

[0082] The actuator refers to the servo motor and its related mechanical components used to achieve vehicle position adjustment; the second coordinate deviation value refers to the vehicle position deviation value re-measured after performing the correction action. The system converts the lateral displacement correction amount and the angle correction amount into motion control commands for the servo motor and sends them to the actuator through the communication interface. After receiving the commands, the left front motion module controls the front wheels to move to the left, and the left rear motion module controls the rear wheels to move to the right, and the position adjustment is synchronously performed when the vehicle is in neutral gear. After the adjustment is completed, the system re-obtains the vehicle position information through the image acquisition device, calculates the new lateral deviation and angle deviation values, and obtains the second coordinate deviation value.

[0083] S311. When the second coordinate deviation value is less than the preset coordinate threshold, it is determined that the vehicle centering operation is completed.

[0084] The preset coordinate threshold represents the maximum position deviation value allowed by the system; the second coordinate deviation value includes the new lateral deviation and angle deviation; the vehicle centering operation refers to the process of making the vehicle park at the center position of the centering platform through the control system. The system respectively records the equal distances from the left front camera and the right front camera to the central axis as x1 and x2, and real-time collects the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera. Calculate the distance s1 from the left front wheel to the central axis as s1 = x1 - y1, calculate the distance s2 from the right front wheel to the central axis as s2 = x2 - y2, and obtain the deviation value Δs = s1 - s2. When the newly calculated lateral deviation and angle deviation are both less than their respective preset thresholds, it indicates that the vehicle has accurately parked at the target position, and the system determines that the centering operation is completed.

[0085] S312. According to the difference in the front and rear weight distribution of the vehicle, the lateral deviation value and the angle deviation value are respectively applied to the front wheel control and the rear wheel control. The proportional coefficient and integral coefficient of the front wheel PID controller are greater than those of the rear wheel PID controller, the differential coefficient of the rear wheel PID controller is greater than that of the front wheel PID controller, and the parameters of the front wheel PID controller and the rear wheel PID controller are obtained through the self-tuning function of the PLC.

[0086] The front-wheel PID controller and the rear-wheel PID controller respectively represent independent controllers for controlling the front wheels and rear wheels of a vehicle; the proportional coefficient represents the response speed of the controller to the deviation; the integral coefficient represents the ability to eliminate the steady-state error; the derivative coefficient represents the degree of improvement of the system's dynamic characteristics; the PLC self-tuning function refers to the function of the programmable controller to obtain the optimal PID parameters through automatic testing. Since the front part of the vehicle is heavier, its inertia and friction are greater than those of the rear part, so the front-wheel controller uses larger proportional and integral coefficients to provide a stronger control effect, while the rear-wheel controller uses a larger derivative coefficient to improve the dynamic response ability. Through the PLC self-tuning function, the system automatically adjusts the parameter values during multiple tests and finally determines the optimal parameter combination for the front and rear-wheel controllers.

[0087] S313. Under the condition that the distances from the left front camera and the right front camera to the central axis are respectively set as equal distances x1 and x2, the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera are collected in real time.

[0088] The left front camera and the right front camera respectively represent industrial cameras installed on the left and right sides of the centering platform; the central axis represents the central reference line of the centering platform; the distances x1 and x2 represent the fixed distances from the two cameras to the central axis; the distances y1 and y2 represent the real-time distances from the two front wheels to the corresponding cameras. During the centering operation, the system synchronously collects images through the left front camera and the right front camera, and extracts the position information of the left front wheel and the right front wheel after image processing. Since the installation positions of the two cameras are symmetric with respect to the central axis, that is, x1 = x2, this provides a basis for calculating the wheel position deviation in the subsequent process. The system measures the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera in real time, and these two distance values are updated in real time as the vehicle position changes.

[0089] S314. Calculate the distance s1 from the left front wheel to the central axis as s1 = x1 - y1, and calculate the distance s2 from the right front wheel to the central axis as s2 = x2 - y2.

[0090] s1 and s2 respectively represent the actual distances from the left front wheel and the right front wheel to the central axis. After obtaining the fixed distances x1, x2 from the cameras to the central axis and the real-time distances y1, y2 from the wheels to the cameras, the system calculates the actual distances from the wheels to the central axis through a simple subtraction operation. The specific calculation method is: the distance s1 from the left front wheel to the central axis is equal to the distance x1 from the left front camera to the central axis minus the distance y1 from the left front wheel to the left front camera, that is, s1 = x1 - y1; similarly, the distance s2 from the right front wheel to the central axis is equal to the distance x2 from the right front camera to the central axis minus the distance y2 from the right front wheel to the right front camera, that is, s2 = x2 - y2. This calculation method is simple and intuitive, facilitating real-time processing.

[0091] S315. Calculate the deviation value Δs = s1 - s2. When y1 = y2, that is, Δs = 0, it indicates that the wheel is at the center position of the floating plate.

[0092] The deviation value Δs represents the difference in the distances from the left front wheel and the right front wheel to the central axis; y1 and y2 respectively represent the distances from the left front wheel to the left front camera and from the right front wheel to the right front camera; the floating plate is a movable platform for supporting and moving the wheels. The system subtracts the calculated s1 and s2 to obtain the deviation value Δs = s1 - s2. When the distance y1 from the left front wheel to the left front camera is equal to the distance y2 from the right front wheel to the right front camera, according to the previous calculations, s1 = x1 - y1 and s2 = x2 - y2. Since x1 = x2, at this time s1 = s2, so Δs = 0. In this case, the left front wheel and the right front wheel are symmetrically distributed on both sides of the central axis, indicating that the vehicle has been accurately positioned at the center position of the floating plate. This symmetric positioning ensures that the vehicle is evenly stressed during the subsequent lifting process, preventing the vehicle from tilting or displacing during the lifting process, and ensuring the safety and accuracy of the maintenance operation.

[0093] S316. When the floating plate and the motion platform are perpendicular, calibrate the zero point of the absolute encoder of the servo motor, divide the displacement of the motion module into positive and negative parts, and when y1 = y2, the position of this servo motor is 0.

[0094] The floating plate and the motion platform refer to the mechanical components for supporting and moving the wheels; the absolute encoder of the servo motor is a sensor for accurately recording the position of the motor; the motion module is the overall mechanism including the servo motor and the transmission mechanism. During the system installation and commissioning stage, first ensure that the floating plate and the motion platform are perpendicular, which is the reference condition for calibration. Set the zero point of the encoder at the center position of the floating plate, that is, the position when y1 = y2. Then divide the total stroke range of the motion module into a positive displacement and a negative displacement with the zero point as the center, so that the motion module can move symmetrically on both sides of the zero point. Through this calibration method, the system establishes an accurate position reference, which not only facilitates the control system to monitor and adjust the vehicle position in real time, but also ensures that the vehicle always remains within a safe motion range during the centering process, avoiding faults such as mechanical interference or overtravel.

[0095] S317. When the vehicle is in neutral gear, control the speeds of all the rollers on the floating plate to be the same, so that when the left front motion module moves to the left, the front wheels move to the left synchronously, and when the left rear motion module moves to the right, the rear wheels move to the right synchronously.

[0096] The left front motion module and the left rear motion module respectively represent the actuators that control the movement of the front wheels and the rear wheels; the vehicle in neutral state means that the vehicle transmission is in the neutral position so that the wheels can rotate freely. When performing the centering adjustment, first confirm that the vehicle is in neutral to ensure that the wheels can move freely. The system controls the speeds of all the rollers on the floating plate to be the same. When the left front motion module moves to the left, the front wheels move to the left synchronously. When the left rear motion module moves to the right, the rear wheels move to the right synchronously. This opposite-direction movement mode can not only achieve the lateral displacement and angle adjustment of the vehicle, but also, due to synchronous control, ensure that the moving speeds of the front and rear wheels are coordinated, avoiding position deviation caused by asynchronous movement. At the same time, this movement mode can also minimize the stress on the vehicle chassis, prevent any damage to the vehicle during the adjustment process, and improve the safety and reliability of the centering system.

[0097] In some embodiments, the following steps may further be included: Before the start of the centering process, obtain the initial tire pressure value P0 and the ambient temperature T0 detected by the TPMS system, and use this pressure value as the reference value; collect the TPMS sensor data in real time through the CAN bus to obtain the real-time pressure value P1 and temperature value T1 during the centering process; use the difference ΔP between the real-time pressure value P1 and the reference value P0 as the judgment basis, where ΔP = P1 - P0; When it is detected that the pressure change rate dp / dt exceeds the preset threshold K1, that is, dp / dt > K1, it is determined that the wheel is about to slip, where dp / dt = ΔP / Δt, and Δt is the sampling time interval; at this time, the controller executes the anti-slip measures: first reduce the output torque to 65% of the current value, and at the same time reduce the torque rising rate to 50% of the standard value until the pressure change rate falls back to the normal range; When it is detected that the fluctuation amplitude ΔP of the pressure value within the period T is greater than the preset threshold K2 and the number of fluctuations n is greater than the preset value N, it is determined that the wheel is in a blocked state; at this time, the controller switches to the pulse torque output mode, where the pulse period is synchronized with the detected pressure fluctuation period T, and the pulse torque amplitude gradually increases until it is detected that the wheel successfully crosses the blocked point; The system further includes a temperature compensation mechanism: based on the temperature change ΔT = T1 - T0 detected by the temperature sensor, calculate the pressure change amount ΔPt caused by temperature, and subtract ΔPt from the actual pressure change amount ΔP to obtain the corrected pressure change amount ΔP', improving the accuracy of abnormal judgment; The controller also establishes a pressure data feature library: record the pressure change curve features and the corresponding road surface conditions during each centering process, and obtain the typical pressure change patterns under different working conditions through cluster analysis; when a new centering task is started, match the most similar historical pattern according to the initial pressure change trend, and adjust the centering parameters in advance to achieve active prevention.

[0098] In some embodiments, the following steps may also be included: Before the alignment begins, the motor is controlled to output a set of increasing torque pulse sequences, with the pulse amplitude gradually increasing from 20% to 80% of the initial torque value, and each pulse lasting for 100ms. The displacement sensor data corresponding to each pulse is collected to obtain the displacement response curve. The safety torque threshold is determined by calculating the slope change of the displacement response curve. The system performs wave-type centering control: the output torque fluctuates within the safety threshold range according to the preset waveform, and the fluctuation amplitude is initially set to ±15% of the safety torque; when the displacement sensor detects an abnormal response, the controller returns the torque to the last stable point and records the torque and displacement values ​​when the abnormality is triggered; Establish a centering parameter database: record the trial results of each centering process, including the safe torque threshold, optimal fluctuation amplitude and displacement response characteristics; for the centering tasks of the same type of vehicles under similar working conditions, the system calls the historical parameters as the initial values ​​and verifies the validity of the parameters through short-term trials; When a wheel abnormality is detected, the controller calculates the optimal escape parameters based on historical trial data; the control motor is controlled to output according to the calculated optimal torque and timing until the abnormality is handled; if the first escape is unsuccessful, the system automatically adjusts the escape parameters and re-executes it, and records the final successful parameter combination.

[0099] The following describes the PID control system in the embodiment of the present invention from the perspective of hardware processing. Figure 4 , which is a schematic diagram of the structure of a physical device of the PID control system in an embodiment of the present application.

[0100] It should be noted that Figure 4 The structure of the PID control system shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present invention.

[0101] like Figure 4As shown, the PID control system includes a Central Processing Unit (CPU) 401, which can perform various appropriate actions and processes according to the program stored in the Read-Only Memory (ROM) 402 or the program loaded from the storage section 408 into the Random Access Memory (RAM) 403, such as executing the methods described in the above embodiments. In the RAM 403, various programs and data required for system operation are also stored. The CPU 401, ROM 402, and RAM 403 are connected to each other via a bus 404. An Input / Output (I / O) interface 405 is also connected to the bus 404.

[0102] The following components are connected to the I / O interface 405: an input section 406 including an audio input device, a button switch, etc.; an output section 407 including a Liquid Crystal Display (LCD), an audio output device, an indicator light, etc.; a storage section 408 including a hard disk, etc.; and a communication section 409 including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication section 409 performs communication processing via a network such as the Internet. A drive 410 is also connected to the I / O interface 405 as needed. A removable medium 411, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 410 as needed so that a computer program read from it can be installed into the storage section 408 as needed.

[0103] Specifically, according to an embodiment of the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program contains a computer program for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network via the communication section 409, and / or installed from the removable medium 411. When the computer program is executed by the Central Processing Unit (CPU) 401, various functions defined in the present invention are executed.

[0104] It should be noted that specific examples of computer-readable storage media may include, but are not limited to: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, optical fibers, portable compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above. In the present invention, a computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0105] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. Among them, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the above-mentioned module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings.

[0106] Specifically, the PID control system of this embodiment includes a processor and a memory, and a computer program is stored on the memory. When the computer program is executed by the processor, it implements the PID control method for realizing non-contact centering of a vehicle provided in the above-mentioned embodiment.

[0107] On the other hand, the present invention also provides a computer-readable storage medium, which may be included in the PID control system described in the above-mentioned embodiment; or it may exist alone without being assembled into the PID control system. The above-mentioned storage medium carries one or more computer programs. When the above-mentioned one or more computer programs are executed by a processor of the PID control system, the PID control system is enabled to implement the PID control method for realizing non-contact centering of a vehicle provided in the above-mentioned embodiment.

[0108] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present application.

[0109] As used in the foregoing embodiments, depending on the context, the term "when" may be construed to mean "if", "after", "in response to determining", or "in response to detecting". Similarly, depending on the context, the phrase "upon determining" or "if (the stated condition or event) is detected" may be construed to mean "if determined", "in response to determining", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0110] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the foregoing embodiments can be implemented by a computer program instructing relevant hardware. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the foregoing method embodiments. The foregoing storage medium includes various media that can store program codes, such as ROM, random access memory (RAM), magnetic disks, or optical discs.

Claims

1. A PID control method for realizing non-contact centering of a vehicle, characterized in that: Applied to a PID control system, the method comprises: Acquire a real-time image of the current position of the target vehicle through an image acquisition device, and pre-process the real-time image to obtain a vehicle profile feature map; Extracting the coordinates of the vehicle feature points according to the vehicle profile feature map, and calculating a first coordinate deviation value between the vehicle feature point coordinates and the preset target position coordinates, wherein the coordinate deviation value includes a lateral deviation and an angular deviation; A vehicle correction instruction is calculated using a PID controller according to the deviation value, wherein the PID controller includes a proportional coefficient, an integral coefficient and a differential coefficient, and the vehicle correction instruction includes a lateral displacement correction amount and an angle correction amount; Sending the vehicle correction instruction to the actuator and obtaining a second coordinate deviation value; When the second coordinate deviation value is less than a preset coordinate threshold, it is determined that the vehicle centering operation is completed.

2. The method according to claim 1, characterized in that The step of calculating the vehicle correction instruction using the PID controller according to the deviation value specifically includes: Using the lateral deviation value as an input of a lateral PID controller, and adjusting the parameters of the lateral PID controller according to the absolute value of the lateral deviation value; Using the angle deviation value as an input of an angle PID controller, and adjusting the parameters of the angle PID controller according to the absolute value of the angle deviation value; A PID control output value is calculated according to the lateral deviation value and the angular deviation value, and a limiting process is performed on the PID control output value to obtain the vehicle correction instruction.

3. The method according to claim 2, characterized in that The step of using the lateral deviation value as an input of a lateral PID controller and adjusting the parameters of the lateral PID controller according to the absolute value of the lateral deviation value specifically includes: When the absolute value of the lateral deviation is greater than a preset first threshold, a first PID parameter is used for control; When the absolute value of the lateral deviation value is not greater than the preset first threshold value and not less than the preset second threshold value, the second PID parameter is used for control; When the absolute value of the lateral deviation value is less than the preset second threshold value, the third PID parameter is used for control, the proportional coefficient of the first PID parameter is greater than the proportional coefficient of the second PID parameter, the proportional coefficient of the second PID parameter is greater than the proportional coefficient of the third PID parameter, the integral coefficient of the third PID parameter is greater than the integral coefficient of the second PID parameter, the integral coefficient of the second PID parameter is greater than the integral coefficient of the first PID parameter, and the differential coefficients of the first PID parameter and the third PID parameter are greater than the differential coefficient of the second PID parameter.

4. The method according to claim 2, characterized in that: The step of using the angle deviation value as an input of an angle PID controller and adjusting the parameters of the angle PID controller according to the absolute value of the angle deviation value specifically includes: When the absolute value of the angle deviation is greater than a preset third threshold, a fourth PID parameter is used for control; When the absolute value of the angle deviation value is not greater than the preset third threshold value and not less than the preset fourth threshold value, the fifth PID parameter is used for control; When the absolute value of the angle deviation value is less than the preset fourth threshold value, a sixth PID parameter is used for control; Among them, the proportional coefficient of the fourth PID parameter is greater than the proportional coefficient of the fifth PID parameter, and the proportional coefficient of the fifth PID parameter is greater than the proportional coefficient of the sixth PID parameter; the integral coefficient of the sixth PID parameter is greater than the integral coefficient of the fifth PID parameter, and the integral coefficient of the fifth PID parameter is greater than the integral coefficient of the fourth PID parameter; the differential coefficient of the fourth PID parameter is greater than the differential coefficient of the fifth PID parameter, and the differential coefficient of the fourth PID parameter is greater than the differential coefficient of the sixth PID parameter.

5. The method according to claim 4, characterized in that After the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than a preset coordinate threshold, the method further includes: According to the difference in front and rear weight distribution of the vehicle, the lateral deviation value and the angular deviation value are respectively applied to the front wheel control and the rear wheel control, the proportional coefficient and the integral coefficient of the front wheel PID controller are greater than the proportional coefficient and the integral coefficient of the rear wheel PID controller, the differential coefficient of the rear wheel PID controller is greater than the differential coefficient of the front wheel PID controller, and the parameters of the front wheel PID controller and the rear wheel PID controller are obtained through the self-tuning function of the PLC.

6. The method according to claim 1, characterized in that After the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than a preset coordinate threshold, the method further includes: Under the condition that the left front camera and the right front camera are set at equal distances x1 and x2 from the central axis respectively, the distance y1 from the left front wheel to the left front camera and the distance y2 from the right front wheel to the right front camera are collected in real time; Calculate the distance s1=x1-y1 from the left front wheel to the central axis, and calculate the distance s2=x2-y2 from the right front wheel to the central axis; The deviation value Δs=s1-s2 is calculated. When y1=y2, that is, Δs=0, it means that the wheel is at the center of the floating plate.

7. The method according to claim 6, characterized in that After the step of determining that the vehicle centering operation is completed when the second coordinate deviation value is less than a preset coordinate threshold, the method further includes: When the floating plate and the motion platform are vertical, calibrate the zero point of the servo motor absolute encoder, divide the displacement of the motion module into positive and negative parts, and when y1=y2, the position of the servo motor is 0; When the vehicle is in neutral gear, the speeds of all rollers on the floating plate are controlled to be consistent, so that when the left front motion module moves to the left, the front wheels move synchronously to the left, and when the left rear motion module moves to the right, the rear wheels move synchronously to the right.

8. A PID control system, characterized in that: The PID control system includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code includes computer instructions, and the one or more processors call the computer instructions to enable the PID control system to execute the method described in any one of claims 1-7.

9. A computer-readable storage medium comprising instructions, characterized in that: When the instruction is executed on a PID control system, the PID control system is caused to execute the method according to any one of claims 1 to 7.

10. A computer program product, characterized in that When the computer program product runs on a PID control system, the PID control system is caused to execute the method according to any one of claims 1 to 7.

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