CN118897557A - A path following control method for a ground adaptive wheeled mobile robot - Google Patents

Abstract

The invention discloses a path following control method of a ground self-adaptive wheel type mobile robot, and relates to the technical field of path following. The ground self-adaptive wheel type mobile robot path following control method comprises the following steps: acquiring a centroid position; obtaining a shortest distance value; and obtaining a stability evaluation index. According to the method, the moving speed and the rotating speed of the rotating wheel of the mobile robot in the preset moving area in a preset time period are monitored in real time to obtain the centroid position, then the shortest distance value of the mobile robot in the moving process is obtained in real time, whether the mobile robot passes through the obstacle area is judged, and finally the maximum allowable speed of the mobile robot in the process of passing through the obstacle area is obtained to obtain the stability evaluation index, so that the effect of improving the timeliness of path following control of the mobile robot is achieved, and the problem that in the prior art, the receiving of obstacle information in the path following control of the mobile robot is not timely is solved.

Description

A path following control method for a ground adaptive wheeled mobile robot

Technical Field

The invention relates to the field of path following technology, and in particular to a path following control method for a ground adaptive wheeled mobile robot.

Background Art

As technology continues to mature, the intelligence level of mobile robots continues to improve, and their application scenarios are becoming more and more abundant. Path following technology is the core link for mobile robots to achieve autonomous navigation and intelligent decision-making. It determines how robots can complete given tasks safely and efficiently in complex environments. At present, path planning technology has made significant progress, including the combination of global path planning and local path planning. Secondly, with the development of technologies such as the Internet of Things and 5G, mobile robots will be able to obtain and process a large amount of environmental information in real time and realize dynamic path planning. However, the environment in the real world is often complex and dynamically changing. As the complexity of the environment increases, the computational complexity of the path following problem will also increase dramatically. Therefore, how to improve computational efficiency while ensuring the accuracy of path following is an important problem that needs to be solved.

The existing mobile robot path following control method places a landmark locator in the working area of the mobile robot and searches for the long-distance signals sent by the landmark locator in the preset area in sequence, then generates a virtual coordinate system with time as the horizontal coordinate and the long distance as the vertical coordinate, and finally controls the motion trajectory of the mobile robot and performs path tracking according to the curved trajectory on the virtual coordinate system, thereby achieving accurate tracking of the motion trajectory of the ground mobile robot.

For example, the invention patent with announcement number: CN115826590B announces a method and system for local path planning of a mobile robot with adaptive parameters, including: sampling in the speed space to obtain multiple groups of speed sets; predicting the trajectory of each group of speed sets to obtain a predicted trajectory; evaluating the predicted trajectory through a preset trajectory evaluation model, and planning the path by adjusting the parameters in the trajectory evaluation model to obtain the optimal path.

For example, the invention patent with announcement number: CN107703948B announces a method for local dynamic path planning of a mobile robot based on an adaptive dynamic window, including: calculating a dynamic range threshold to determine whether it has entered a dense obstacle area, and when it is determined to have entered a dense obstacle area, calculating the dynamic weight of the linear speed; calculating the distance between obstacles and determining whether it can pass through the dense obstacle area, and when it is determined to be able to pass through the dense obstacle area, searching the alternative speed space to obtain the allowable speed when no collision occurs; substituting the dynamic weight and the allowable speed into the objective function, and obtaining the optimal speed combination as the robot's running speed through the objective function; executing the optimal speed to determine whether the target point has been reached, and if it is determined to have been reached, stopping the robot from moving, and otherwise returning to the first step and restarting the subsequent steps.

However, in the process of implementing the technical solution of the invention in the embodiments of the present application, the present application found that the above technology has at least the following technical problems:

In the prior art, obstacles in the working area distort the long-distance signals sent by the landmark locator, resulting in inaccurate position information on the virtual coordinate system, thereby causing the risk of deviation from the predetermined path or collision. There is a problem of untimely receipt of obstacle information in the path following control of the mobile robot.

Summary of the invention

The embodiment of the present application solves the problem of untimely receipt of obstacle information in the path following control of the mobile robot in the prior art by providing a path following control method for a ground adaptive wheeled mobile robot, thereby improving the timeliness of the path following control of the mobile robot.

An embodiment of the present application provides a path following control method for a ground adaptive wheeled mobile robot, comprising the following steps: S1, real-time monitoring of the moving speed and rotation speed of the rotating wheels of the mobile robot in a preset moving area within a preset time period to obtain the center of mass position; S2, real-time acquisition of the shortest distance value between the mobile robot and obstacles in the obstacle area during the movement of the mobile robot, and at the same time, judging whether the mobile robot executes to cross the obstacle area according to the shortest distance value, and if not, adjusting the maximum rotational linear speed and maximum rotational angular speed of the rotating wheels until the obstacle area is crossed; S3, acquiring the maximum allowable speed of the mobile robot in the process of crossing the obstacle area, and at the same time, adjusting the rated rotational speed of the rotating wheels of the mobile robot in the process of moving according to the maximum allowable speed to obtain a stability evaluation index, wherein the stability evaluation index is used to quantify the stability of the mobile robot in the process of adjusting the speed.

Furthermore, the specific limiting expression of the center of mass position is:

;

Where t is the number of the preset time period, , T is the total number of preset time periods, represents the center of mass position of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the horizontal coordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the ordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation angle of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the distance between the moving center and the mass center of the mobile robot in the t-th preset time period, represents the rotational angular velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the moving speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the radius of the mobile robot's rotating wheels, It represents the distance between the left and right rotating wheels of the mobile robot; the moving center is the center position of the line connecting the center points of the left rotating wheel and the right rotating wheel of the mobile robot during movement; the moving speed command and the rotation speed command are control signals issued by the PID speed controller.

Furthermore, the acquisition of the center of mass position further includes: real-time monitoring of the change of the center of mass position of the mobile robot during movement and obtaining the center of mass position offset rate in combination with the reference center of mass position, and obtaining the path accuracy evaluation value in combination with the ground friction degree of the rotating wheel, wherein the center of mass position offset rate is the distance difference between the center of mass position on the mobile two-dimensional coordinate system and the reference center of mass position, and the path accuracy evaluation value is used to evaluate the accuracy of the moving path of the mobile robot after receiving the control signal; the path accuracy evaluation value is calculated by the following formula:

;

In the formula, e is a natural constant, represents the path accuracy evaluation value of the mobile robot during its movement in the tth preset time period, It represents the displacement rate of the center of mass position of the mobile robot during the movement in the tth preset time period. represents the ground friction degree of the preset moving area where the left turning wheel of the mobile robot is located in the t-th preset time period, represents the ground friction degree of the preset moving area where the right rotating wheel of the mobile robot is located in the t-th preset time period, represents the moving speed of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation speed of the mobile robot's wheels in the tth preset time period, Indicates the reference rotation angle.

Furthermore, the method of obtaining the path accuracy evaluation value also includes: step one, judging whether to adjust the control parameters of the PID speed controller according to the numerical change of the path accuracy evaluation value; if not, it indicates that the actual moving path of the mobile robot is in the same direction as the reference path, and the control parameters include the driving force of the rotating wheel, the control gain and the medium frequency of the filter; step two, after the control parameters of the PID speed controller are adjusted, re-monitoring the movement process of the mobile robot within a preset time period until the actual moving path of the mobile robot is in the same direction as the reference path.

Furthermore, the specific process of judging whether the mobile robot executes crossing the obstacle area according to the shortest distance value is as follows: when the shortest distance value is greater than the dynamic distance threshold, the obstacle area is crossed; when the shortest distance value is not greater than the dynamic distance threshold, the obstacle area is not crossed, and at the same time, the maximum rotation speed of the rotating wheel is adjusted according to the rated rotation speed of the rotating wheel until the corresponding shortest distance value is greater than the dynamic distance threshold; the specific restriction expression of the dynamic distance threshold is:

;

Where t is the number of the preset time period, , T is the total number of preset time periods, represents the dynamic distance threshold of the mobile robot in the tth preset time period, It represents the vertical distance between the mobile robot and the obstacle area in the tth preset time period. represents the maximum rotational linear velocity of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the maximum rotation speed of the rotating wheels of the mobile robot in the tth preset time period, Indicates the rotational angular acceleration of the rotating wheels of the mobile robot in the tth preset time period.

Furthermore, the stability evaluation index is obtained by the following method: obtaining the speed adjustment response time and the acceleration fluctuation amplitude and combining them with the corresponding reference value to obtain the stability evaluation index, the speed adjustment response time includes the linear speed adjustment response time and the angular speed adjustment response time, the linear speed adjustment response time is the time period required for the rated linear speed to be adjusted to the maximum allowable linear speed, the angular speed adjustment response time is the time period required for the rated angular speed to be adjusted to the maximum allowable angular speed, and the acceleration fluctuation amplitude is the difference between the maximum acceleration and the minimum acceleration measured in real time by the acceleration sensor within a preset time period.

Furthermore, the stability evaluation index is calculated by the following formula:

;

In the formula, e is a natural constant, t is the number of the preset time period, , T is the total number of preset time periods, It represents the stability evaluation index of the mobile robot during the speed adjustment process in the t-th preset time period, It represents the linear speed adjustment response time of the mobile robot during the speed adjustment process in the tth preset time period, Indicates the reference response time for line speed adjustment. represents the angular velocity adjustment response time of the mobile robot during the velocity adjustment process in the tth preset time period, Indicates the reference response time for angular velocity adjustment, It represents the acceleration fluctuation amplitude of the mobile robot during the speed adjustment process in the tth preset time period. Indicates the acceleration reference fluctuation amplitude.

Furthermore, the obtaining of the stability evaluation index further includes: real-time monitoring of the speed threshold of the mobile robot during the movement process, dividing the speed interval in combination with the stability evaluation index, and controlling the moving speed of the mobile robot within the speed interval in real time through a PID speed controller, wherein the speed threshold is the difference between the maximum moving speed and the minimum moving speed of the mobile robot during the movement process, and the real-time control is used to automatically adjust the moving speed of the mobile robot.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

1. The center of mass position is obtained by real-time monitoring of the moving speed and rotation speed of the rotating wheels of the mobile robot in a preset moving area within a preset time period, and then the shortest distance value of the mobile robot in the moving process is obtained in real time to determine whether the mobile robot executes to cross the obstacle area, and finally the maximum allowable speed of the mobile robot in the process of crossing the obstacle area is obtained to obtain the stability evaluation index, thereby achieving the improvement of the accuracy and efficiency of real-time monitoring of the center of mass position, and then achieving the improvement of the timeliness of the path following control of the mobile robot, and effectively solving the problem of untimely receipt of obstacle information in the path following control of the mobile robot in the prior art.

2. Determine whether to adjust the control parameters of the PID speed controller based on the numerical change of the path accuracy evaluation value. If not, it indicates that the actual moving path of the mobile robot is in the same direction as the reference path. At the same time, after the control parameters of the PID speed controller are adjusted, re-monitor the movement process of the mobile robot within a preset time period until the actual moving path of the mobile robot is in the same direction as the reference path, thereby improving the accuracy of obtaining the path accuracy evaluation value and achieving more precise adjustment of the actual moving path of the mobile robot.

3. By obtaining the braking parameters of the mobile robot during the movement and obtaining the maximum braking distance according to the obstacle position, the longest braking time is recorded in real time to obtain the minimum braking speed. Then, within the longest braking time range, the time when the mobile robot starts braking and the time after the braking ends when it contacts the obstacle area are monitored in real time to obtain the shortest braking distance and the shortest braking time. Finally, the maximum allowable speed is obtained in combination with the braking distance, thereby improving the accuracy of real-time monitoring of the braking process of the mobile robot, and further improving the accuracy and reliability of obtaining the maximum allowable speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a path following control method for a ground adaptive wheeled mobile robot provided in an embodiment of the present application;

FIG2 is a flowchart of obtaining the maximum allowed speed provided in an embodiment of the present application;

FIG3 is a flow chart of real-time control of the moving speed of a mobile robot provided in an embodiment of the present application.

DETAILED DESCRIPTION

The embodiment of the present application solves the problem of untimely receipt of obstacle information in the path following control of the mobile robot in the prior art by providing a path following control method for a ground adaptive wheeled mobile robot. The method monitors the moving speed and rotation speed of the rotating wheels of the mobile robot in the obstacle area and the non-obstacle area in real time within a preset time period to obtain the center of mass position, and then obtains in real time the shortest distance value between the mobile robot and the obstacles in the obstacle area during the movement. At the same time, it is judged whether the mobile robot executes to cross the obstacle area according to the shortest distance value. If not, the maximum rotational linear speed and maximum rotational angular speed of the rotating wheels are adjusted until the obstacle area is crossed. Finally, the maximum non-contact speed and maximum braking speed of the mobile robot in the process of crossing the obstacle area are obtained. At the same time, the rated rotational speed of the rotating wheels of the mobile robot during the movement is adjusted according to the maximum allowable speed to obtain the stability evaluation index, thereby improving the timeliness of the path following control of the mobile robot.

The technical solution in the embodiment of the present application is to solve the problem of untimely receiving obstacle information in the path following control of the mobile robot. The overall idea is as follows:

By real-time monitoring of the moving speed and rotation speed of the mobile robot's rotating wheels to obtain the center of mass position, and then obtaining the shortest distance value of the mobile robot during the movement process in real time and judging whether the mobile robot is crossing the obstacle area, and finally obtaining the maximum allowable speed of the mobile robot in the process of crossing the obstacle area to obtain the stability evaluation index, the effect of improving the timeliness of the mobile robot's path following control is achieved.

In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

As shown in FIG1 , a flow chart of a path following control method for a ground adaptive wheeled mobile robot provided in an embodiment of the present application is provided, and the method comprises the following steps: S1, real-time monitoring of the moving speed and rotation speed of the rotating wheels of the mobile robot in a preset moving area within a preset time period to obtain the center of mass position, the preset moving area comprises an obstacle area and a non-obstacle area, the mobile robot is in a two-dimensional moving coordinate system, the origin in the two-dimensional moving coordinate system is the center of mass of the mobile robot, the rotating wheels comprise a left rotating wheel and a right rotating wheel, the left rotating wheel and the right rotating wheel have the same moving speed and rotation speed, and the moving speed and rotation speed are controlled by a path following controller; S2, real-time acquisition of the shortest distance value between the mobile robot and the obstacles in the obstacle area during movement, and at the same time judging whether the mobile robot executes the obstacle crossing according to the shortest distance value. area, if not executed, the maximum rotational linear speed and the maximum rotational angular speed of the rotating wheel are adjusted until the obstacle area is crossed. The dynamic distance threshold is the judgment condition for the mobile robot to cross the obstacle area during its movement within a preset time period; S3, obtaining the maximum allowable speed of the mobile robot during the process of crossing the obstacle area, and adjusting the rated rotational speed of the rotating wheels of the mobile robot during the movement according to the maximum allowable speed to obtain a stability evaluation index, the maximum allowable speed includes the maximum non-contact speed and the maximum braking speed, the maximum non-contact speed is the speed of the trajectory without contacting the collision obstacle, the maximum braking speed is the speed at which the mobile robot can be braked to stop immediately when crossing the obstacle area, the rated rotational speed includes the rated linear speed and the rated angular speed, and the stability evaluation index is used to quantify the stability of the mobile robot during the speed adjustment process.

Among them, the specific restriction expression of the center of mass position is:

;

Where t is the number of the preset time period, , T is the total number of preset time periods, represents the center of mass position of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the horizontal coordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the ordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation angle of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the distance between the moving center and the mass center of the mobile robot in the t-th preset time period, represents the rotational angular velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the moving speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the radius of the mobile robot's rotating wheels, It indicates the distance between the left and right rotating wheels of the mobile robot. The moving center is the center position of the line connecting the center points of the left rotating wheel and the right rotating wheel of the mobile robot during movement. The moving speed command and the rotation speed command are the control signals issued by the PID speed controller.

In this embodiment, by real-time monitoring of the moving speed and the rotation speed, and combining this information to calculate the center of mass position of the mobile robot, the path following controller can accurately understand the current state of the robot, and improve the robot's perception of its own position and posture, wherein the path following controller is integrated in the control unit of the mobile robot, and the rotation angle is the angle relative to the x-axis on the two-dimensional moving coordinate system; by real-time acquisition of the shortest distance to the obstacle, and judging whether to perform the operation of crossing the obstacle area based on this distance, and by dynamically adjusting the distance threshold, the mobile robot can respond to the obstacle environment in real time and improve the efficiency and safety of path following; the rated linear speed is represented by the result of summing and averaging the historical maximum linear speeds of the rotating wheels in the preset database, and the rated angular speed is represented by the result of summing and averaging the historical maximum angular speeds of the rotating wheels in the preset database. When crossing the obstacle area, the rated linear speed and rated angular speed of the rotating wheel are adjusted in real time through the maximum non-contact speed and the maximum braking speed, which helps to maximize the movement efficiency while ensuring the stable movement of the robot, and realizes the improvement of the timeliness of the path following control of the mobile robot.

It should be understood that the linear speed of rotation is measured in real time by a speed sensor, the angular speed of rotation is measured in real time by an angular speed sensor, and the rotation angle is measured in real time by an angle sensor. The moving speed command and the rotation speed command are the moving set values assigned by the PID speed controller before the mobile robot moves within a preset time period. The moving speed command and the rotation speed command are used to change the motion trajectory of the center of mass position in real time to adapt to different paths and obstacle environments, thereby achieving improved accuracy and reliability in real-time monitoring of the center of mass position, and thereby achieving improved timeliness in the path following control of the mobile robot, effectively solving the problem of untimely receipt of obstacle information in the path following control of the mobile robot in the prior art.

Furthermore, the center of mass position is obtained, and then it also includes: real-time monitoring of the change of the center of mass position of the mobile robot during movement and obtaining the center of mass position offset rate in combination with the reference center of mass position, and obtaining the path accuracy evaluation value in combination with the ground friction degree of the rotating wheel. The center of mass position offset rate is the distance difference between the center of mass position on the mobile two-dimensional coordinate system and the reference center of mass position. The path accuracy evaluation value is used to evaluate the accuracy of the moving path of the mobile robot after receiving the control signal; the path accuracy evaluation value is calculated by the following formula:

;

In the formula, e is a natural constant, represents the path accuracy evaluation value of the mobile robot during its movement in the tth preset time period, It represents the displacement rate of the center of mass position of the mobile robot during the movement in the tth preset time period. represents the ground friction degree of the preset moving area where the left turning wheel of the mobile robot is located in the t-th preset time period, represents the ground friction degree of the preset moving area where the right rotating wheel of the mobile robot is located in the t-th preset time period, represents the moving speed of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation speed of the mobile robot's wheels in the tth preset time period, Indicates the reference rotation angle.

In this embodiment, the reference center of mass position is the moving center of the mobile robot during the movement process within a preset time period. The center of mass position deviation rate directly reflects the degree of deviation of the mobile robot from the reference path during the movement process. The smaller the center of mass position deviation rate, the smaller the deviation between the actual moving path of the corresponding mobile robot and the reference path. In a complex and changeable mobile environment, such as uneven ground and sudden appearance of obstacles, the center of mass position of the mobile robot may be significantly affected. This embodiment enables the mobile robot to quickly respond to environmental changes and dynamically adjust its motion state by real-time monitoring of the center of mass position changes, thereby improving the intelligence and adaptability of path control, thereby improving the stability and safety of the robot.

The reference rotation angle is represented by the sum and average of the historical rotation angles of the rotating wheels in the preset database; the moving speed and the rotation speed are measured in real time by the speed sensor on the rotating wheel of the mobile robot; it should be understood that the center of mass position deviation rate also indirectly affects the value of the moving speed of the mobile robot during the movement process. When the center of mass position deviation rate decreases, it means that the current moving path of the mobile robot is close to the reference path. At this time, the PID speed controller may allow the robot to move forward at a faster moving speed (i.e., increase the moving speed instruction) to improve the work efficiency. On the contrary, when the center of mass position deviation rate increases, the PID speed controller may reduce the moving speed (i.e., reduce the moving speed instruction) to adjust the position of the robot more accurately. Assuming that the mobile robot performs a navigation task in a complex indoor environment, its reference path is to move straight along the corridor. During the movement, if the center of mass position deviation rate increases due to uneven ground or obstacle interference, the PID speed controller will immediately detect this change, immediately reduce the moving speed, and adjust the rotation speed of the rotating wheel so that the robot can return to the reference path smoothly.

It should be noted that the ground friction between the contact surface between the rotating wheel and the preset moving area of the mobile robot is not zero during movement, so the influence of the reference value is not considered in the calculation of the path accuracy evaluation value; the torque force of the left rotating wheel in the preset moving area is measured in real time by the torque sensor, and the ground friction degree of the left rotating wheel is obtained by multiplying the torque force with the friction coefficient of the left rotating wheel itself; the torque force of the right rotating wheel in the preset moving area is measured in real time by the torque sensor, and the ground friction degree of the right rotating wheel is obtained by multiplying the torque force with the friction coefficient of the right rotating wheel itself, wherein the friction coefficient of the left rotating wheel itself and the friction coefficient of the right rotating wheel itself are set by the mobile robot manufacturer, for example, when the rotating wheel surface is made of rubber material, the corresponding friction coefficient is 0.6-0.8, and when the rotating wheel surface is made of polyurethane material, the corresponding friction coefficient is 0.7-0.9.

Specifically, to simplify the analysis, define , , , represents the moving speed coefficient of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation speed coefficient of the rotating wheel of the mobile robot in the tth preset time period, It represents the rotation angle coefficient of the rotating wheel of the mobile robot in the tth preset time period. The simplified calculation formula of the path accuracy evaluation value is: ,The statistical table of the change of the path accuracy evaluation value is shown in Table 1:

Table 1 Statistics of changes in path accuracy evaluation values

Left wheel ground friction degree M1 _t Right wheel ground friction degree M2 _t Movement speed coefficient U1 Rotation speed coefficient U2 Rotation angle coefficient U3 Path accuracy evaluation value WU _t 0.21 0.23 0.43 0.19 0.49 0.675 0.33 0.18 0.39 0.25 0.32 0.672 0.17 0.11 0.58 0.10 0.21 0.729 0.08 0.29 0.26 0.33 0.53 0.668 0.19 0.14 0.15 0.29 0.13 0.784 ...... ...... ...... ...... ...... ......

It should be understood that the path accuracy evaluation value decreases with the increase of the left wheel ground friction degree, the right wheel ground friction degree, the moving speed coefficient, the rotation speed coefficient and the rotation angle coefficient. , and , if the ground friction degree of the left wheel and the ground friction degree of the right wheel are smaller, the deviation between the actual moving path of the corresponding mobile robot after receiving the moving speed command and the rotation speed command and the reference path is the smallest, wherein the reference path is the path set by the preset personnel before the mobile robot moves. It should be noted that the ideal situation is not considered here (the ideal situation refers to the mobile robot's left wheel ground friction degree and the right wheel ground friction degree equal to 0).

Specifically, the degree of ground friction also indirectly affects the value of the rotation angle of the rotating wheel. A ground with a lower degree of friction may allow the rotating wheel to rotate at a faster speed. On the contrary, on a ground with a higher degree of friction, the rotating wheel requires a larger torque to overcome the friction, which may cause the rotation speed to slow down, but the accuracy of the rotation angle may be higher. By considering the impact of the degree of ground friction on the rotation angle of the rotating wheel, the mobile robot can better adapt to different ground environments. Whether it is a smooth tile floor or a rough gravel road, the robot can adjust the control parameters to maintain stable performance and accurate rotation angle. This enhanced environmental adaptability enables the robot to perform well in a wider range of application scenarios.

Although the rotation speed of the rotating wheels may be limited on a ground with a high degree of friction, this embodiment can ensure precise control of the rotation angle by optimizing the control algorithm and sensor feedback mechanism, which means that the robot can accurately turn and position according to a predetermined path and angle, thereby improving the timeliness of the mobile robot's path following control, and effectively solving the problem of untimely receipt of obstacle information in the mobile robot's path following control in the prior art.

Furthermore, a path accuracy evaluation value is obtained, and then the following includes: step one, judging whether to adjust the control parameters of the PID speed controller according to the numerical change of the path accuracy evaluation value; if not, it indicates that the actual moving path of the mobile robot is in the same direction as the reference path, and the control parameters include the driving force of the rotating wheel, the control gain and the medium frequency of the filter; step two, after the control parameters of the PID speed controller are adjusted, re-monitoring the moving process of the mobile robot within a preset time period until the actual moving path of the mobile robot is in the same direction as the reference path.

In this embodiment, the proportional gain Kp, the integral gain Ki and the differential gain Kd are three control gain parameters in the PID speed controller (Proportion Integration Differentiation Controller). The controller's immediate response speed to errors can be affected by adjusting the proportional gain. For example, when the moving speed is less than the moving speed command, Kp needs to be increased to increase the moving speed until the moving speed is equal to the moving speed command. The integral gain Ki is used to reduce the deviation between the moving speed and the moving speed command (such as the absolute value of the difference between the moving speed and the moving speed command). When the moving speed is less than the moving speed command, the differential gain Kd is increased to predict the changing trend of the deviation, thereby achieving more timely correction of the deviation. When the moving speed is less than the moving speed command, the driving force of the rotating wheel is increased to increase the moving speed of the robot until it is equal to the moving speed command, thereby affecting the accuracy of its tracking path and achieving more accurate positioning of the actual moving path of the mobile robot.

Furthermore, the specific process of judging whether the mobile robot executes crossing the obstacle area according to the shortest distance value is as follows: when the shortest distance value is greater than the dynamic distance threshold, the obstacle area is crossed; when the shortest distance value is not greater than the dynamic distance threshold, the obstacle area is not crossed; at the same time, the maximum rotation speed of the rotating wheel is adjusted according to the rated speed of the rotating wheel until the corresponding shortest distance value is greater than the dynamic distance threshold, and the maximum rotation speed includes the maximum rotation linear speed and the maximum rotation angular speed; the specific restriction expression of the dynamic distance threshold is:

;

Where t is the number of the preset time period, , T is the total number of preset time periods, represents the dynamic distance threshold of the mobile robot in the tth preset time period, It represents the vertical distance between the mobile robot and the obstacle area in the tth preset time period. represents the maximum rotational linear velocity of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the maximum rotational angular velocity of the rotating wheels of the mobile robot in the tth preset time period, Indicates the rotational angular velocity of the rotating wheels of the mobile robot in the tth preset time period.

In this embodiment, since the mobile robot avoids obstacles in the obstacle area during the movement, the vertical distance between the mobile robot and the obstacle area before the movement is not 0, wherein the vertical distance is the distance between the moving center of the mobile robot and the center point of the obstacle area, and the dynamic distance threshold increases with the increase of the vertical distance, the maximum rotational linear velocity and the maximum rotational angular velocity, wherein the maximum rotational linear velocity is the maximum rotational linear velocity of the rotating wheel during the movement, and the maximum rotational angular velocity is the maximum rotational angular velocity of the rotating wheel during the movement, and the rotational linear acceleration and the rotational angular acceleration are measured in real time by the acceleration sensor.

Specifically, the shortest distance value is calculated by the following formula:

;

Where t is the number of the preset time period, , T is the total number of preset time periods, m is the number of obstacles in the obstacle area, , M is the total number of obstacles in the obstacle area, represents the shortest distance between the mobile robot and the obstacles in the obstacle area during the tth preset time period, represents the distance between the mobile robot and the obstacle in the mth obstacle area during the tth preset time period, represents the distance between the mobile robot and the obstacle in the m+1th obstacle area during the tth preset time period, represents the azimuth angle between the preset azimuth angle measurement point of the mobile robot in the tth preset time period and the obstacle in the mth obstacle area, Represents the azimuth angle between the preset azimuth angle measurement point of the mobile robot in the tth preset time period and the obstacle in the m+1th obstacle area; the preset time period only includes one preset azimuth angle measurement point.

It should be understood that when the shortest distance value is not greater than the dynamic distance threshold, the maximum rotational linear speed and maximum rotational angular speed of the rotating wheel are adjusted until they are not greater than the rated linear speed and rated angular speed. At the same time, the preset azimuth measurement point of the mobile robot within the preset time period is adjusted and the azimuth between the preset azimuth measurement point and the obstacle is re-measured in real time through the angle sensor. Then, the adjusted maximum rotational linear speed, maximum rotational angular speed and the re-acquired azimuth are re-substituted into the calculation formula of the shortest distance value and the dynamic distance threshold and recalculated until the shortest distance value is greater than the dynamic distance threshold. This helps to improve the safety and tracking efficiency of the mobile robot moving in the obstacle area, realizes more accurate avoidance of obstacles by the mobile robot in the process of crossing the obstacle area, and thus realizes the improvement of the timeliness of the mobile robot path following control, and effectively solves the problem of untimely receiving obstacle information in the mobile robot path following control in the prior art.

Furthermore, as shown in FIG2 , a flowchart for obtaining the maximum allowable speed is provided in an embodiment of the present application. The specific steps for obtaining the maximum allowable speed of the mobile robot in the process of crossing an obstacle area are as follows: obtaining the braking parameters of the mobile robot during the movement and obtaining the maximum braking distance according to the position of the obstacle, and recording the longest braking time in real time to obtain the minimum braking speed. The braking parameters include braking distance and braking time. The maximum braking distance is the sum of the braking distance and the distance when the mobile robot reaches the obstacle but does not contact the obstacle. The longest braking time is the time when the mobile robot does not contact the obstacle. The minimum braking speed is the ratio of the maximum braking distance to the longest braking time. Within the range of the longest braking time, the time when the mobile robot starts braking when it contacts the obstacle area and the time after the braking ends are monitored in real time to obtain the shortest braking distance and the shortest braking time. At the same time, the maximum allowable speed is obtained in combination with the braking distance. The shortest braking distance is the straight-line distance between the mobile robot and the obstacle area. The shortest braking time is used to reflect the response time of the mobile robot to the obstacle area instruction. The maximum allowable speed is the ratio of the braking distance to the shortest braking time.

In this embodiment, in an automated warehouse, the mobile robot detects a worker suddenly appearing in the front passage through a sensor and calculates the current distance between the worker and the robot. At the same time, the robot predicts how long and how far it will take to stop safely when the worker is stationary (ideal situation) based on its own braking performance (known maximum braking distance and shortest braking time). When the robot confirms that it must brake to avoid a collision (i.e., the moment of "contacting the obstacle area"), it records the time at this time and the time after the braking is completed to obtain the shortest braking time (i.e., the difference between the time after the braking is completed and the time when the "contacting the obstacle area"); the shortest braking distance can be directly obtained by the straight-line distance difference between the robot and the worker measured by the laser radar before and after the braking begins. Through the above process, the mobile robot can dynamically calculate and adjust its braking parameters and maximum allowable speed, thereby improving the operating efficiency as much as possible while ensuring safety, and improving the safety and accuracy of the mobile robot's avoidance process when crossing the obstacle area.

Furthermore, the maximum permissible speed of the mobile robot in the process of crossing the obstacle area is obtained, and then it also includes: real-time acquisition of the safe crossing distance and safe crossing time of the mobile robot in the process of crossing the obstacle area, the safe crossing distance is the moving distance of the mobile robot when it does not contact the obstacle in the process of crossing the obstacle area, and the safe crossing time is the time corresponding to the safe crossing distance; the safe braking speed is obtained and used as the shortest response speed when the mobile robot collides with an obstacle, the safe braking speed is the ratio of the safe crossing distance to the safe crossing time, and the shortest response speed is used to reduce the degree of collision damage between the mobile robot and the obstacle in the process of crossing the obstacle area.

In this embodiment, the safe braking speed represents the minimum speed required for the mobile robot to quickly decelerate to zero when an obstacle is detected. By setting the safe braking speed as the robot's shortest response speed, it can be ensured that when the robot crosses an obstacle area, once a collision risk is detected, it can immediately decelerate to reduce the degree of collision damage with the obstacle. In practical applications, the mobile robot also needs to consider its own dynamic characteristics and the performance limitations of the braking system to ensure that the calculated safe braking speed and shortest response speed are feasible in practice, which helps to reduce the possibility of a collision between the mobile robot and an obstacle, and improves the accuracy and real-time performance of obstacle signal acquisition during path following.

Furthermore, the stability evaluation index is obtained by the following method: the speed adjustment response time and the acceleration fluctuation amplitude are obtained and combined with the corresponding reference value to obtain the stability evaluation index, the speed adjustment response time includes the linear speed adjustment response time and the angular speed adjustment response time, the linear speed adjustment response time is the time period required for the rated linear speed to be adjusted to the maximum allowable linear speed, the angular speed adjustment response time is the time period required for the rated angular speed to be adjusted to the maximum allowable angular speed, and the acceleration fluctuation amplitude is the difference between the maximum acceleration and the minimum acceleration measured in real time by the acceleration sensor within a preset time period.

Among them, the stability evaluation index is calculated by the following formula:

;

In the formula, e is a natural constant, t is the number of the preset time period, , T is the total number of preset time periods, It represents the stability evaluation index of the mobile robot during the speed adjustment process in the t-th preset time period, It represents the linear speed adjustment response time of the mobile robot during the speed adjustment process in the tth preset time period, Indicates the reference response time for line speed adjustment. represents the angular velocity adjustment response time of the mobile robot during the velocity adjustment process in the tth preset time period, Indicates the reference response time for angular velocity adjustment, It represents the acceleration fluctuation amplitude of the mobile robot during the speed adjustment process in the tth preset time period. Indicates the acceleration reference fluctuation amplitude.

In this embodiment, the linear speed adjustment response time is the difference between the time when the rated linear speed is adjusted to the maximum allowable angular speed and the time when the rated linear speed is just started to be adjusted, and the angular speed adjustment response time is the difference between the time when the rated angular speed is adjusted to the maximum allowable angular speed and the time when the rated angular speed is just started to be adjusted, wherein the maximum allowable linear speed is represented by the sum and average of the maximum values of the historical moving linear speeds within the historical time period in the preset database, and the maximum allowable angular speed is represented by the sum and average of the maximum values of the historical rotational angular speeds within the historical time period in the preset database; when the acceleration fluctuation amplitude decreases, it indicates that the movement process of the mobile robot within the preset time period is smoother, otherwise, it is unstable, but the acceleration fluctuation amplitude is not 0, because while ensuring the stable movement of the mobile robot, it is also necessary to ensure the response rate of the mobile robot to obstacle signals. Therefore, the mobile robot cannot move at a constant speed all the time within the preset time period, thereby improving the movement stability and response rate of the mobile robot in the obstacle area.

To simplify the analysis, we define , , , It represents the linear speed adjustment response coefficient of the mobile robot during the speed adjustment process in the t-th preset time period, It represents the angular velocity adjustment response coefficient of the mobile robot during the velocity adjustment process in the tth preset time period, It represents the acceleration fluctuation coefficient of the mobile robot during the speed adjustment process in the t-th preset time period. The simplified calculation formula of the stability evaluation index is: , the statistical table of changes in stability evaluation indicators is shown in Table 2:

Table 2 Statistics of changes in stability evaluation indicators

Line speed adjustment response coefficient H1 _t Angular velocity adjustment response coefficient H2 _t Acceleration fluctuation coefficient H3 _t Stability evaluation index SU _t 0.21 0.13 0.05 0.810 0.17 0.08 0.16 0.801 0.23 0.09 0.22 0.747 0.07 0.16 0.14 0.818 0.11 0.05 0.10 0.869 ...... ...... ...... ......

It should be understood that the reference response time for adjusting the linear velocity, the reference response time for adjusting the angular velocity, and the reference fluctuation amplitude of the acceleration are the minimum values in the historical velocity adjustment process in the preset database, that is, , and , the stability evaluation index decreases with the increase of linear speed adjustment response time, angular speed adjustment response time and acceleration fluctuation amplitude, and the stability evaluation index decreases with the increase of linear speed adjustment response coefficient, angular speed adjustment response coefficient and acceleration fluctuation coefficient. The reference response time of linear speed adjustment is represented by the result of summing and averaging the historical linear speed adjustment time in the historical time period in the preset database, the reference response time of angular speed adjustment is represented by the result of summing and averaging the historical angular speed adjustment time in the historical time period in the preset database, and the reference fluctuation amplitude of acceleration is represented by the difference between the historical maximum acceleration and the historical minimum acceleration in the historical time period in the preset database. Therefore, when the actual value of the mobile robot in the moving process is equal to the minimum value (i.e. , and ), the corresponding mobile robot has the best stability in the process of adjusting speed.

It should be noted that the response time of linear speed adjustment and angular speed adjustment also indirectly affects the value of the acceleration fluctuation amplitude. Suppose a mobile robot is driving in a straight line at a constant speed on a flat ground. Suddenly, it receives a signal that it needs to turn. At this time, if the response time of linear speed and angular speed is set to be longer (such as 1 second), the mobile robot will gradually decelerate and start turning. This smooth transition will reduce the sudden change of acceleration, thereby reducing the acceleration fluctuation amplitude and improving stability. If the response time is set to be very short (such as 0.2 seconds), the mobile robot may immediately start to decelerate and change direction quickly, resulting in an increase in the acceleration fluctuation amplitude, especially in the initial stage of turning, because the mobile robot needs to quickly overcome its inertia and change the direction of movement.

By adjusting the response time to control the smoothness of the mobile robot's deceleration and turning, the sudden change of acceleration is reduced, thereby reducing the amplitude of acceleration fluctuation. This smooth transition makes the stability evaluation index more accurate and reliable. Secondly, the fine adjustment of the response time enables the robot to travel more accurately along the reference path, especially in complex environments, and can reduce the deviation of the mobile robot from the path due to sudden changes in acceleration. Compared with the problem of untimely reception of obstacle information that may exist in the prior art, the embodiment of the present application dynamically adjusts the response time to adapt to different environments and task requirements. The robot can sense environmental changes faster and make corresponding adjustments while ensuring stability, thereby improving the obstacle avoidance capability and the reliability of the overall path following, and effectively solving the problem of untimely reception of obstacle information in the path following control of the mobile robot in the prior art.

Furthermore, as shown in Figure 3, a real-time control flow chart of the moving speed of a mobile robot provided in an embodiment of the present application obtains a stability evaluation index, and then also includes: real-time monitoring of the speed threshold of the mobile robot during the movement process, and dividing the speed interval in combination with the stability evaluation index, and controlling the moving speed of the mobile robot within the speed interval in real time through a PID speed controller. The speed threshold is the difference between the maximum moving speed and the minimum moving speed of the mobile robot during the movement process. The speed interval includes an acceleration interval and a deceleration interval. The real-time control is used to automatically adjust the moving speed of the mobile robot.

In this embodiment, the speed interval also includes a uniform speed interval, wherein the acceleration interval: starts from the current moving speed of the mobile robot to the upper limit speed of safe acceleration determined based on the stability evaluation index (i.e., the maximum moving speed at which the mobile robot does not collide with obstacles). This upper limit speed should ensure that the robot maintains sufficient stability during the acceleration process; the uniform speed interval: after reaching the upper limit of acceleration, the robot can maintain a stable speed range (i.e., a speed range that does not exceed the maximum allowable speed); the deceleration interval: starts from the upper limit of the uniform speed interval to the target speed at which the mobile robot needs to stop. A mobile robot speed control system based on the stability evaluation index is implemented, which can automatically adjust the moving speed of the robot to ensure that it can maintain a stable and efficient operating state during the path following process.

To summarize, the embodiment of the present application obtains the center of mass position by real-time monitoring the moving speed and rotation speed of the rotating wheels of the mobile robot in a preset moving area within a preset time period, and then obtains the shortest distance value of the mobile robot during the movement in real time and determines whether the mobile robot is executing the crossing of the obstacle area, and finally obtains the maximum allowable speed of the mobile robot in the process of crossing the obstacle area to obtain the stability evaluation index, thereby achieving the improvement of the accuracy and efficiency of the real-time monitoring of the center of mass position, and then achieving the improvement of the timeliness of the path following control of the mobile robot, which effectively solves the problem of untimely reception of obstacle information in the path following control of the mobile robot in the prior art.

It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

The present invention is described with reference to the flowcharts and/or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and/or box in the flowchart and/or block diagram, as well as the combination of the processes and/or boxes in the flowchart and/or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate a device for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (10)

1. A path following control method for a ground adaptive wheeled mobile robot, characterized in that it comprises the following steps: S1, real-time monitoring of the moving speed and rotation speed of the rotating wheels of the mobile robot in a preset moving area within a preset time period to obtain the center of mass position; S2, obtaining in real time the shortest distance between the mobile robot and the obstacles in the obstacle area during the movement process, and judging whether the mobile robot executes to cross the obstacle area according to the shortest distance value, and if not, adjusting the maximum rotation linear speed and the maximum rotation angular speed of the rotating wheel until the mobile robot executes to cross the obstacle area; S3, obtaining the maximum allowable speed of the mobile robot in the process of crossing the obstacle area, and adjusting the rated rotation speed of the rotating wheels of the mobile robot during the movement according to the maximum allowable speed to obtain a stability evaluation index, wherein the stability evaluation index is used to quantify the stability of the mobile robot in the process of adjusting the speed. 2. A path following control method for a ground adaptive wheeled mobile robot according to claim 1, characterized in that the specific limiting expression of the center of mass position is: ; ; Where t is the number of the preset time period, , T is the total number of preset time periods, represents the center of mass position of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the horizontal coordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the ordinate of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation angle of the mobile robot in the two-dimensional mobile coordinate system within the t-th preset time period, represents the distance between the moving center and the mass center of the mobile robot in the t-th preset time period, represents the rotational angular velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the moving speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the rotation speed instruction of the rotating wheel of the mobile robot in the tth preset time period, represents the radius of the mobile robot's rotating wheels, Indicates the distance between the left and right turning wheels of the mobile robot; The moving center is the center position of the line connecting the center point of the left rotating wheel and the center point of the right rotating wheel of the mobile robot during the movement; The moving speed instruction and the rotating speed instruction are control signals issued by a PID speed controller. 3. A path following control method for a ground adaptive wheeled mobile robot according to claim 2, characterized in that the step of obtaining the center of mass position further comprises: Monitor the change of the center of mass position of the mobile robot in real time during movement and obtain the center of mass position deviation rate in combination with the reference center of mass position, and obtain the path accuracy evaluation value in combination with the ground friction degree of the rotating wheels. The center of mass position deviation rate is the distance difference between the center of mass position on the mobile two-dimensional coordinate system and the reference center of mass position. The path accuracy evaluation value is used to evaluate the accuracy of the moving path of the mobile robot after receiving the control signal; The path accuracy evaluation value is calculated by the following formula: ; In the formula, e is a natural constant, represents the path accuracy evaluation value of the mobile robot during its movement in the tth preset time period, It represents the displacement rate of the center of mass position of the mobile robot during the movement in the tth preset time period. represents the ground friction degree of the preset moving area where the left turning wheel of the mobile robot is located in the t-th preset time period, represents the ground friction degree of the preset moving area where the right rotating wheel of the mobile robot is located in the t-th preset time period, represents the moving speed of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation speed of the mobile robot's wheels in the tth preset time period, Indicates the reference rotation angle. 4. A path following control method for a ground adaptive wheeled mobile robot according to claim 3, characterized in that the step of obtaining the path accuracy evaluation value further comprises: Step 1: judging whether to adjust the control parameters of the PID speed controller according to the numerical change of the path accuracy evaluation value; if not, it indicates that the actual moving path of the mobile robot is in the same direction as the reference path; Step 2: After the control parameters of the PID speed controller are adjusted, the movement process of the mobile robot within a preset time period is re-monitored until the actual movement path of the mobile robot is in the same direction as the reference path. 5. A path following control method for a ground adaptive wheeled mobile robot as claimed in claim 1, characterized in that the specific process of judging whether the mobile robot executes crossing the obstacle area according to the shortest distance value is: When the shortest distance value is greater than the dynamic distance threshold, the obstacle area is crossed, otherwise the obstacle area is not crossed, and the maximum rotation speed of the rotating wheel is adjusted according to the rated rotation speed of the rotating wheel until the corresponding shortest distance value is greater than the dynamic distance threshold; The specific limiting expression of the dynamic distance threshold is: ; Where t is the number of the preset time period, , T is the total number of preset time periods, represents the dynamic distance threshold of the mobile robot in the tth preset time period, It represents the vertical distance between the mobile robot and the obstacle area in the tth preset time period. represents the maximum rotational linear velocity of the rotating wheels of the mobile robot in the tth preset time period, represents the rotation linear velocity of the rotating wheel of the mobile robot in the tth preset time period, represents the maximum rotational angular velocity of the rotating wheels of the mobile robot in the tth preset time period, Indicates the rotational angular velocity of the rotating wheels of the mobile robot in the tth preset time period. 6. A path following control method for a ground adaptive wheeled mobile robot as claimed in claim 1, characterized in that the specific steps of obtaining the maximum allowable speed of the mobile robot in the process of crossing an obstacle area are: Obtain the braking parameters of the mobile robot during movement and obtain the maximum braking distance according to the obstacle position, and obtain the minimum braking speed in combination with the longest braking time recorded in real time; The time when the mobile robot starts braking and the time when the braking ends when it contacts the obstacle area are monitored in real time within the longest braking time range to obtain the shortest braking distance and the shortest braking time, and the maximum allowable speed is obtained in combination with the braking distance. 7. A path following control method for a ground adaptive wheeled mobile robot according to claim 1, characterized in that the step of obtaining the maximum allowable speed of the mobile robot in the process of crossing an obstacle area further comprises: Obtain the safe crossing distance and safe crossing time of the mobile robot in real time when it crosses the obstacle area; The safe braking speed is obtained and used as the shortest response speed when the mobile robot collides with an obstacle. The safe braking speed is the ratio of the safe crossing distance to the safe crossing time. The shortest response speed is used to reduce the degree of collision damage between the mobile robot and the obstacle when crossing the obstacle area. 8. A path following control method for a ground adaptive wheeled mobile robot according to claim 1, characterized in that the stability evaluation index is obtained by the following method: The speed adjustment response time and the acceleration fluctuation amplitude are obtained and combined with the corresponding reference value to obtain a stability evaluation index, wherein the speed adjustment response time includes the linear speed adjustment response time and the angular speed adjustment response time, wherein the linear speed adjustment response time is the time period required for adjusting the rated linear speed to the maximum allowable linear speed, and the angular speed adjustment response time is the time period required for adjusting the rated angular speed to the maximum allowable angular speed, and the acceleration fluctuation amplitude is the difference between the maximum acceleration and the minimum acceleration measured in real time by the acceleration sensor within a preset time period. 9. A path following control method for a ground adaptive wheeled mobile robot as claimed in claim 8, characterized in that the stability evaluation index is calculated by the following formula: ; In the formula, e is a natural constant, t is the number of the preset time period, , T is the total number of preset time periods, It represents the stability evaluation index of the mobile robot during the speed adjustment process in the t-th preset time period, It represents the linear speed adjustment response time of the mobile robot during the speed adjustment process in the tth preset time period, Indicates the reference response time for line speed adjustment. represents the angular velocity adjustment response time of the mobile robot during the velocity adjustment process in the tth preset time period, Indicates the reference response time for angular velocity adjustment, It represents the acceleration fluctuation amplitude of the mobile robot during the speed adjustment process in the tth preset time period. Indicates the acceleration reference fluctuation amplitude. 10. A path following control method for a ground adaptive wheeled mobile robot according to claim 1, characterized in that the step of obtaining a stability evaluation index further comprises: The speed threshold of the mobile robot during movement is monitored in real time, and the speed interval is divided in combination with the stability evaluation index. The moving speed of the mobile robot within the speed interval is controlled in real time by a PID speed controller. The speed threshold is the difference between the maximum moving speed and the minimum moving speed of the mobile robot during movement. The real-time control is used to automatically adjust the moving speed of the mobile robot.