Industrial robot and experimental device and evaluation method for joint play

Abstract

The application discloses an industrial robot and an experimental device and an evaluation method for joint clearance, and the method comprises the following steps: acquiring an end position time sequence of the industrial robot through the experimental device for joint clearance of the industrial robot; obtaining running tracks of multiple joint clearances of the industrial robot by adjusting the size of the joint clearance, and obtaining a corresponding relationship of the joint clearance; monitoring the running track of the industrial robot in an online processing working state, comparing the fluctuation degree of the nonlinearity value of the dynamic behavior of the industrial robot, and evaluating the size of the joint clearance of the industrial robot. Through the use of the application, the problems that it is difficult to measure the joint clearance of the industrial robot and it is difficult to measure the end position of the industrial robot in a large range can be overcome. The application can be widely applied to the technical field of industrial robots as an experimental device and an evaluation method for joint clearance of an industrial robot.

Description

Technical Field

[0001] This invention relates to the field of industrial robot technology, and in particular to an experimental apparatus and evaluation method for an industrial robot and its joint clearances. Background Technology

[0002] SCARA robotic arms are a special type of industrial robot with cylindrical coordinates. Due to their excellent rigidity in the vertical plane and good compliance in the horizontal plane, they are widely used in microelectronics manufacturing, automotive industries, and other fields. Traditional SCARA robotic arms suffer from drawbacks such as weak load capacity, small working range, and low operating speed. Furthermore, as open-loop mechanisms, SCARA robotic arms are susceptible to various uncertainties such as machining errors, assembly errors, joint clearances, friction, and elasticity, leading to end-effector position errors and reduced positioning accuracy. Joint clearance is a crucial factor affecting positioning accuracy, making its evaluation significant for research and practical application. However, direct measurement of joint clearance is difficult, and installing sensors within the joints to measure clearance can increase the added mass of the robotic arm and even alter its structural characteristics. Therefore, a method for indirectly evaluating joint clearance is needed. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide an experimental apparatus and evaluation method for industrial robots and joint clearances. This method not only overcomes the shortcomings of existing SCARA robots, such as weak load capacity, small working range, and low operating speed, but also overcomes the difficulties in measuring joint clearances and measuring the end effector position of industrial robots over a wide range.

[0004] The first technical solution adopted in this invention is: an industrial robot, including a base, a main arm on the base, the base being movably connected to the main arm via a shoulder joint; a forearm on the main arm, the main arm being movably connected to the forearm via an elbow joint; an end effector on the forearm, the forearm being movably connected to the end effector via a wrist joint; control units are provided on the shoulder joint, the elbow joint, and the wrist joint, the control units being used to control the rotation of the shoulder joint, the elbow joint, and the wrist joint; the control units are electrically connected to an electric slip ring via a cable, the electric slip ring being used to prevent the cable from tangling.

[0005] Furthermore, it also includes a support base, which is disposed on the forearm, and the surface of the support base is provided with reflective dots.

[0006] The second technical solution adopted in this invention is: an experimental device for measuring the joint clearance of an industrial robot, comprising a vibration isolation platform, a support, and a camera. The industrial robot is placed on the vibration isolation platform, the support is placed directly above the robot, and the camera and the slip ring are mounted on the support. The lens of the camera is arranged opposite to the base.

[0007] Furthermore, it also includes a computer, which is electrically connected to the camera.

[0008] The third technical solution adopted in this invention is: a method for evaluating the joint clearance of an industrial robot, comprising the following steps: The end-effector trajectory of the industrial robot is set and discretized to obtain the position time series, velocity time series and acceleration time series of the preset trajectory; Based on the inverse kinematics equations of a two-degree-of-freedom robotic arm, the position time series, velocity time series, and acceleration time series of a preset trajectory are used to calculate the angle time series, angular velocity time series, and angular acceleration time series of each joint of the industrial robot. Acquire an image of the actual trajectory of the industrial robot running from the initial position of the preset trajectory, and extract the position of the reflective point from the image; The positional increment of the industrial robot's end effector is calculated based on the position of the reflective point; The actual end-effector pose time series of the industrial robot is obtained by calculating the initial position of the trajectory and the end-effector pose increment of the industrial robot. The nonlinearity value of the industrial robot's dynamic behavior is obtained by processing the actual end-effector pose time series. The joint clearances of the industrial robot were reset and cyclic tests were performed to obtain multiple sets of end-effector pose time series. The relationship between joint gap and the degree of fluctuation of nonlinearity value was constructed based on multiple sets of end-position time series. The size of the joint clearance of the industrial robot to be evaluated is determined by assessing the relationship between the joint clearance and the degree of fluctuation in nonlinearity.

[0009] Furthermore, the calculation formula for the inverse kinematics equation of the two-degree-of-freedom manipulator is as follows: ; In the above formula, Indicates the end effector position of the industrial robot. Indicates the angle of the shoulder joint. Indicates the elbow joint angle. This indicates the distance between the axes of the shoulder and elbow joints. It indicates the distance between the axes of the elbow and wrist joints.

[0010] Furthermore, the calculation formula for the end-effector pose increment of the industrial robot is as follows: ; ; ; ; In the above formula, This indicates the location of the first reflective point in the previous image. This indicates the location of the second reflective point in the previous image. This indicates the position of the first reflective point in the current image. This indicates the position of the second reflective point in the current image. This represents the increment of the end effector position of the industrial robot in the x-axis direction. This represents the increment of the end effector position of the industrial robot in the y-axis direction. This represents the increment of the end effector angle of an industrial robot. Indicates the angle of the first reflective point. This indicates the angle of the second reflective point.

[0011] Furthermore, the step of processing the actual end-effector pose time series of the industrial robot to obtain the nonlinearity value of the industrial robot's dynamic behavior specifically includes: The position error time series is calculated by comparing the actual position time series of the end effector of the industrial robot with the position time series of the preset trajectory. ARIMA linear fitting is performed on the position error time series to obtain the fitted position error time series; After calculating the difference between the position error time series and the position error fitted time series The norm is used to obtain the nonlinearity value of the dynamic behavior of industrial robots.

[0012] Furthermore, the step of constructing the relationship between joint gap and the degree of fluctuation of nonlinearity value based on multiple sets of end-effector pose time series... Specifically, this includes obtaining discrete data of nonlinearity values ​​based on multiple sets of end-effector pose time series; The discrete data is fitted with a function, and the distance from the discrete data to the function is calculated to obtain a distance sequence. Calculate the maximum and minimum points of the distance sequence to obtain the upper and lower envelopes; The distance obtained by subtracting the upper and lower envelopes is used to construct the relationship between the joint gap and the degree of fluctuation of the nonlinearity value.

[0013] Furthermore, the step of assessing the size of the joint clearance of the industrial robot to be evaluated based on the relationship between the joint clearance and the degree of fluctuation of the nonlinearity value specifically includes: Obtain multiple sets of end-effector pose time series as the end-effector of the industrial robot to be evaluated moves along a preset trajectory; Calculate the nonlinearity value based on multiple sets of end-effector pose time series; Find the minimum and maximum values ​​of the nonlinearity and take the difference to obtain the maximum difference in the nonlinearity values; The size of the joint clearance of the industrial robot to be evaluated is determined by using the relationship between joint clearance and the degree of fluctuation of nonlinearity value, based on the maximum difference of nonlinearity value.

[0014] The beneficial effects of the method and apparatus of this invention are as follows: First, this invention discloses an industrial robot that uses an electric slip ring as an intermediate device for signal transmission between each joint and the servo driver, enabling arbitrary rotation of each joint without being constrained by cables, thus achieving the goal of arbitrary rotation of the industrial robot joints. Second, it discloses an experimental device for measuring the joint clearance of an industrial robot. By acquiring the end-effector position of the industrial robot through a camera, the end-effector position of the industrial robot is indirectly measured and the size of the joint clearance is evaluated. This is a non-contact measurement, which has the advantages of not adding additional mass to the structure and not changing the structural characteristics. Finally, this invention method acquires an image of the end-effector position of the industrial robot through a camera, extracts the position of the reflective points in the image, obtains the actual position time series of the industrial robot's preset running trajectory, and uses the end-effector position time series to evaluate the joint clearance of the robotic arm. It has a wide range of applicability and strong practicality. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of an experimental device for an industrial robot and its joint gap according to the present invention; Figure 2 This is a flowchart illustrating a method for evaluating joint clearance in an industrial robot according to the present invention. Figure 3 This is a schematic diagram illustrating the relationship between joint clearance and nonlinearity value in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of the difference between the joint space and the envelope of the nonlinearity value in a specific embodiment of the present invention; Figure 5 This is a schematic diagram of the evaluation gap in a specific embodiment of the present invention; Figure 6 This is a flowchart illustrating the method for comparing the maximum nonlinear difference with the degree of fluctuation in a specific embodiment of the present invention. Figure 7 This is a schematic diagram of adjusting the joint gap in a specific embodiment of the present invention.

[0016] The attached figures are labeled as follows: 1. Base, 2. Upper arm, 3. Shoulder joint, 4. Forearm, 5. Elbow joint, 6. End effector, 7. Wrist joint, 8. Control unit, 9. Electric slip ring, 10. Support base, 11. First reflector, 12. Second reflector, 13. Vibration isolation platform, 14. Bracket, 15. Camera, 16. Cable, 17. Expansion sleeve bolt, 18. Expansion sleeve. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0018] Reference Figure 1 This invention provides an industrial robot, including a base 1, a main arm 2 mounted on the base 1, and the base 1 being movably connected to the main arm 2 via a shoulder joint 3; a forearm 4 mounted on the main arm 2, and the main arm 2 being movably connected to the forearm 4 via an elbow joint 5; an end effector 6 mounted on the forearm 4, and the forearm 4 being movably connected to the end effector 6 via a wrist joint 7; control units 8 are provided on the shoulder joint 3, elbow joint 5, and wrist joint 7, and the control units 8 are used to control the rotation of the shoulder joint 3, elbow joint 5, and wrist joint 7; the control units 8 are electrically connected to an electric slip ring 9 via a cable 16, and the electric slip ring 9 is used to prevent the cable 16 from getting tangled; a support base 10 is also provided on the forearm 4, and the surface of the support base 10 is provided with a first reflective point 11 and a second reflective point 12.

[0019] Specifically, the base 1 is made of 45# steel, the upper arm 2 is made of 45# steel, and the distance between the shoulder joint 3 and elbow joint 5 in the upper arm 2 is 0.3m. The forearm 4 is made of 7076 aluminum alloy, and the distance between the elbow joint 5 and wrist joint 7 in the forearm 4 is 0.3m. The end effector 6 is a platform with a diameter of 180mm. As a preferred embodiment of this solution, both the shoulder joint 3 and the elbow joint 5 are composed of a flange and a bearing seat, thereby enabling the base 1 to be movably connected to the upper arm 2 through the shoulder joint 3, and the upper arm 2 to be movably connected to the forearm 4 through the elbow joint 5. As a preferred embodiment of this solution, the control unit 8 on the shoulder joint 3 consists of a first servo motor, a first reducer, and a first servo driver. The first servo motor is connected to the first reducer, and the first servo motor is electrically connected to the first servo driver through an electric slip ring 9, thereby realizing arbitrary rotation of the shoulder joint 3. Similarly, the control unit 8 on the elbow joint 5 consists of a second servo motor, a second reducer, and a second servo driver; the control unit 8 on the wrist joint 7 consists of a third servo motor, a third reducer, and a third servo driver.

[0020] Specifically, the first servo motor is a Yaskawa SGM7A-10AFA61, and the first servo driver is a Yaskawa SGD7S-120A00B202; the second servo motor is a Yaskawa SGM7A-08AFA61, and the second servo driver is a Yaskawa SGD7S-5R5A00B202; the third servo motor is a Yaskawa SGM7S-R90A00A002, and the third servo driver is a Yaskawa SGD7S-120A00B202.

[0021] It should be noted that the first servo motor, the second servo motor, and the third servo motor are all servo motors; the first reducer, the second reducer, and the third reducer are all reducers; and the first servo driver, the second servo driver, and the third servo driver are all servo drivers.

[0022] like Figure 1 As shown, the present invention provides an experimental device for measuring the joint clearance of an industrial robot, including a vibration isolation platform 13, a support 14, and a camera 15. The industrial robot is placed on the vibration isolation platform 13, and the support 14 is placed directly above the robot. The support 14 is equipped with a camera 15 and an electric slip ring 9. The lens of the camera 15 is arranged opposite to the base 1, and the camera 15 is electrically connected to a computer.

[0023] Before conducting the experiment, the base 1 of the industrial robot was first installed on the vibration isolation platform 13. Then, the bracket 14 was erected directly above the industrial robot. The slip ring 9 was fixed to the top of the bracket 14. The cable 16 at the rotating end of the slip ring 9 was connected to the servo motor cables 16 of the wrist joint 7 and elbow joint 5. The cable 16 at the fixed end of the slip ring 9 was connected to the servo driver. The servo motor and reducer of the shoulder joint 3 were installed inside the base 1. Its encoder line and power line were directly connected to the servo driver. Then, the camera 15 was also set on the top of the bracket 14. The camera 15 was connected to the computer through a USB 3.0 serial port. The lens of the camera 15 was facing the base 1, so that the center point of the lens coincided with the axis of the shoulder joint 3. Finally, two reflecting points 11 and 12 with two focusing lights were installed on the support base 10 as feature objects for visual detection by the camera 15.

[0024] The bracket 14 is composed of multiple aluminum profiles. The camera 15 is a Mercury II PRO series camera of the Daheng Imaging brand, model ME2P-2621-15U3M, with a resolution of 5120×5120, a frame rate of 15.1fps, and a transmission protocol of USB3.0. The lens of the camera 15 is a fixed-focus lens of the same brand, model HN-0826-20M-C1. The selected computer CPU is an i7 9700, with 8GB of memory.

[0025] To make the reflective points in the images captured by camera 15 more obvious, a light source can also be provided to camera 15.

[0026] like Figure 2 , Figure 5 and Figure 6 As shown, the present invention provides a method for evaluating the joint clearance of an industrial robot, comprising the following steps: S1. Set the end-effector trajectory of the industrial robot and discretize it to obtain the position time series, velocity time series and acceleration time series of the preset trajectory; S2. Based on the inverse kinematics equations of the two-degree-of-freedom robotic arm, the angle time series, angular velocity time series, and angular acceleration time series of each joint of the industrial robot are obtained by calculating the position time series, velocity time series, and acceleration time series of the preset trajectory according to the position time series, velocity time series, and acceleration time series of the preset trajectory. Specifically, the formula for calculating the inverse kinematics equations of a two-degree-of-freedom robotic arm is as follows: ; In the above formula, Indicates the end effector position of the industrial robot. Indicates the angle of the shoulder joint. Indicates the elbow joint angle. This indicates the distance between the axes of the shoulder and elbow joints. It indicates the distance between the axes of the elbow and wrist joints.

[0027] By substituting the position time series, velocity time series, and acceleration time series of the preset trajectory into the above formula, the angle time series, angular velocity time series, and angular acceleration time series of each joint can be obtained.

[0028] S3. Obtain an image of the actual trajectory of the industrial robot running from the initial position of the preset trajectory, and extract the position of the reflective point from the image; Specifically, the time series of angles, angular velocities, and angular accelerations of the corresponding joints of the robotic arm are converted and transmitted through a motion control card, servo driver, and slip ring. The time series are converted into current inputs to the servo motor, which generates torque to drive the robotic arm to run from the initial position of the trajectory. The camera takes pictures at fixed intervals, and the images are transmitted to the computer through a USB 3.0 interface. The computer processes the images according to a preset program and extracts the coordinate positions of the first and second reflective points from the images.

[0029] Among them, the motion control card is a computer-based upper-level control unit used in various motion control applications (including displacement, speed, acceleration, etc.).

[0030] S4. Calculate the end-effector pose increment of the industrial robot based on the position of the reflective point; Specifically, pose represents position and orientation. The formula for calculating the pose increment of the end effector of an industrial robot is as follows: ; ; ; ; ; In the above formula, This indicates the location of the first reflective point in the previous image. This indicates the location of the second reflective point in the previous image. This indicates the position of the first reflective point in the current image. This indicates the position of the second reflective point in the current image. Indicates in The increment of the end-effector position in the axial direction of the industrial robot. Indicates in The increment of the end-effector position in the axial direction of the industrial robot. This represents the increment of the end effector angle of an industrial robot. Indicates the angle of the first reflective point. This indicates the angle of the second reflective point.

[0031] Assumption If the value is greater than zero, then the end effector of the industrial robot will move towards... If the axis moves in the positive direction, then If the value is less than zero, then the end effector of the industrial robot will... Movement in the negative direction of the axis; Directional increment and angle increment Similarly.

[0032] S5. Calculate the actual end-effector pose time series of the industrial robot based on the initial trajectory position and the end-effector pose increment of the industrial robot. S6. Process the actual end-effector pose time series of the industrial robot to obtain the nonlinearity value of the industrial robot's dynamic behavior. S6.1. Calculate the position error time series based on the actual position time series of the end effector of the industrial robot and the position time series of the preset trajectory. Specifically, assuming the camera measures the actual position time series of the industrial robot's end effector and the position time series of the preset trajectory, respectively... and A position error time series is obtained by taking the points at the same instant of the actual position time series and the position time series of the preset trajectory as the distance. The calculation formula is as follows: .

[0033] S6.2, Perform position error time series analysis Linear fitting yields the fitted time series of the position error; Specifically, The model is a differential autoregressive moving average model obtained by combining the autoregressive (AR) model, the moving average (MA) model, and the differencing method. ,in It is the order in which the data needs to be differencing.

[0034] in, The model is as follows: ; In the above formula, , , This represents a white noise sequence with a mean of zero.

[0035] First, the ARMA model requires that the time series be stationary, so the time series is first tested for stationarity using the ADF test and KPSS test. If the data fails the test, the time series is differencing and then tested for stationarity again, until the time series passes the stationarity test. The difference order I is the degree of differencing. Secondly, the sequences that pass the stationarity test are fitted with different AR and MA orders. The fitted models are estimated using the AIC and BIC criteria to determine the optimal one among all orders, which is taken as the AR and MA orders of the model. Finally, the position error time series Using difference order I, AR order, and MA order fitting, the fitted sequence is the time series. The ARIMA linear fitting sequence, that is, the time series of position error fitting. .

[0036] S6.3, Calculate the difference between the position error time series and the position error fitted time series. The norm is used to obtain the nonlinearity value of the dynamic behavior of industrial robots.

[0037] Specifically, industrial robot dynamics studies the relationship between joint forces, torques, and joint motions. The main purpose is to calculate the torque that each joint actuator should provide when the joints of an industrial robot perform a target motion through a dynamic model, and then use this torque value for robot control. An industrial robot is a complex dynamic system with severe nonlinearity. The relationship between joint forces, torques, and joint motion parameters is mostly trigonometric function. There are also severe coupling relationships, with the motions of each joint coupled with each other, and the forces and torques also coupled with each other. Therefore, to analyze the dynamic characteristics of an industrial robot, a very systematic analysis method must be adopted.

[0038] Nonlinearity refers to nonlinear error, which is relative to linear error. Using the input and output (measurement, result) of measuring tools as the horizontal and vertical axes of a Cartesian coordinate system, and selecting suitable axes, we can obtain an ideal input-output relationship curve by plotting the ideal input and output points on the coordinates. Similarly, plotting the actual input and output points on the coordinates yields an actual input-output relationship curve. Ideally, these two curves should coincide, but this is practically impossible; the distance between the two curves is the error. If the two curves are identical in shape but do not coincide—meaning one curve represents the displacement of the other—then the error is linear; otherwise, the error is nonlinear.

[0039] The formula for calculating the nonlinearity value is as follows: .

[0040] In the above formula, express Norm, which is the square root of the sum of the squares of the elements of a vector.

[0041] S7. Reset the joint clearances of the industrial robot and perform a cyclic test to obtain multiple sets of end-effector pose time series. Specifically, such as Figure 7 As shown, the expansion sleeve bolts 17 and expansion sleeves 18 at each joint of the industrial robot are tightened so that the end effector of the industrial robot can run along a preset trajectory. Then, the joint clearance is increased by loosening the expansion sleeve bolts 17 and expansion sleeves 18. The actual position time series of the end effector of the industrial robot running the preset trajectory at different joint clearances is measured by a camera to obtain multiple sets of end effector pose time series.

[0042] S8. Construct the relationship between joint gap and nonlinearity fluctuation based on multiple sets of end pose time series; Specifically, firstly, discrete data of nonlinearity values ​​are obtained based on multiple sets of end-effector pose time series. ; Then, as Figure 3 As shown, a function is applied to discrete data. Fitting to find discrete points arrive The distance is calculated, and all maxima in the distance sequence are identified as first-order feature points. Then, using the first-order feature points as new discrete data, all maximum points are found from the first-order envelope feature points as second-order feature points. And so on, when When the number of second-order feature points is less than 4, use n-order feature points. corresponding discrete points Construct a function Fitting, function Let the upper envelope be denoted as ; similarly, the lower envelope can be obtained, and its fitting function is . ; Finally, as Figure 4 As shown, the upper and lower envelopes of the discrete nonlinearity values ​​are plotted. The distance obtained by subtracting the points on the upper and lower envelopes with the same gap is the degree of nonlinearity fluctuation in the robot arm's dynamic behavior. Therefore, the relationship between the joint space and the degree of fluctuation of the nonlinearity value can be deduced as follows: .

[0043] S9. Evaluate the size of the joint clearance of the industrial robot to be evaluated based on the relationship between the joint clearance and the degree of fluctuation of the nonlinearity value.

[0044] Specifically, the industrial robot to be evaluated is made to run a preset trajectory, and multiple sets of end-effector pose time series of the industrial robot to be evaluated are measured and calculated using a camera. The maximum difference in nonlinearity values ​​is then determined. Assuming the gap size is The degree of nonlinearity fluctuation in the dynamic behavior of industrial robots is ,like The joint clearance range of the industrial robot to be evaluated is... ,in This is an empirical constant.

[0045] The beneficial effects of this invention specifically include: 1) This method overcomes the difficulties in measuring joint clearances and end-effector positions of industrial robots over a wide range. By using a large-area camera to measure the end-effector position, the actual position time series of the industrial robot's preset trajectory is obtained. This time series is then processed to assess the size of the joint clearances of the industrial robot. This method is an indirect method for measuring end-effector position and assessing the size of joint clearances of the robotic arm. It is a non-contact measurement method with the advantages of not adding additional mass to the structure and not changing the structural characteristics. It has a wide range of applicability and is highly practical.

[0046] 2) To overcome the shortcomings of existing SCARA robots, such as weak load capacity, small working range and low running speed, an electric slip ring is used as an intermediate device for signal transmission between the servo motor and the servo driver, so as to realize the arbitrary rotation of the servo motor without being constrained by the cable, and achieve the purpose of arbitrary rotation of the robot joint.

[0047] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method of evaluating a joint gap of an industrial robot, characterized by, The industrial robot includes a base, on which a large arm is mounted, the base being movably connected to the large arm via a shoulder joint; a forearm is mounted on the large arm, the large arm being movably connected to the forearm via an elbow joint; an end effector is mounted on the forearm, the forearm being movably connected to the end effector via a wrist joint; control units are mounted on the shoulder joint, the elbow joint, and the wrist joint, the control units being used to control the rotation of the shoulder joint, the elbow joint, and the wrist joint; the control units are electrically connected to an electric slip ring via a cable, the electric slip ring being used to prevent the cable from tangling; it also includes a support base, the support base being mounted on the forearm, the surface of the support base having reflective dots; it also includes a vibration isolation platform, a bracket, and a camera, the industrial robot being mounted on the vibration isolation platform, the bracket being positioned directly above the industrial robot, the bracket being mounted on the camera and the electric slip ring, the camera lens being arranged opposite to the base; it also includes a computer, the computer being electrically connected to the camera; The evaluation method includes the following steps: The end-effector trajectory of the industrial robot is set and discretized to obtain the position time series, velocity time series and acceleration time series of the preset trajectory; Based on the inverse kinematics equations of a two-degree-of-freedom robotic arm, the position time series, velocity time series, and acceleration time series of a preset trajectory are used to calculate the angle time series, angular velocity time series, and angular acceleration time series of each joint of the industrial robot. Acquire an image of the actual trajectory of the industrial robot running from the initial position of the preset trajectory, and extract the position of the reflective point from the image; The positional increment of the industrial robot's end effector is calculated based on the position of the reflective point; The actual end-effector pose time series of the industrial robot is obtained by calculating the initial position of the trajectory and the end-effector pose increment of the industrial robot. The nonlinearity value of the industrial robot's dynamic behavior is obtained by processing the actual end-effector pose time series. The joint clearances of the industrial robot were reset and cyclic tests were performed to obtain multiple sets of end-effector pose time series. The relationship between joint gap and the degree of fluctuation of nonlinearity value was constructed based on multiple sets of end-position time series. The size of the joint clearance of the industrial robot to be evaluated is determined by the relationship between the joint clearance and the degree of fluctuation of the nonlinearity value. The step of processing the actual end-effector pose time series of the industrial robot to obtain the nonlinearity value of the industrial robot's dynamic behavior specifically includes: The position error time series is calculated by comparing the actual position time series of the end effector of the industrial robot with the position time series of the preset trajectory. ARIMA linear fitting is performed on the position error time series to obtain the fitted position error time series; After calculating the difference between the position error time series and the position error fitted time series The norm is used to obtain the nonlinearity value of the dynamic behavior of the industrial robot; The step of constructing the relationship between joint gap and the degree of nonlinearity fluctuation based on multiple sets of end-effector pose time series specifically includes: Based on multiple sets of end-effector pose time series, discrete data of nonlinearity values ​​are obtained; The discrete data is fitted with a function, and the distance from the discrete data to the function is calculated to obtain a distance sequence. Calculate the maximum and minimum points of the distance sequence to obtain the upper and lower envelopes; The distance obtained by subtracting the upper and lower envelopes is used to construct the relationship between the joint space and the degree of fluctuation of the nonlinearity value; The step of assessing the size of the joint clearance of the industrial robot to be evaluated based on the relationship between the joint clearance and the degree of fluctuation of the nonlinearity value specifically includes: Obtain multiple sets of end-effector pose time series as the end-effector of the industrial robot to be evaluated moves along a preset trajectory; Calculate the nonlinearity value based on multiple sets of end-effector pose time series; Find the minimum and maximum values ​​of the nonlinearity and take the difference to obtain the maximum difference in the nonlinearity values; The size of the joint clearance of the industrial robot to be evaluated is determined by using the relationship between joint clearance and the degree of fluctuation of nonlinearity value, based on the maximum difference of nonlinearity value.

2. The method for evaluating the joint clearance of an industrial robot according to claim 1, characterized in that, The calculation formula for the inverse kinematics equation of the two-degree-of-freedom robotic arm is as follows: ； In the above formula, Indicates the end effector position of the industrial robot. Indicates the angle of the shoulder joint. Indicates the elbow joint angle. This indicates the distance between the axes of the shoulder and elbow joints. It indicates the distance between the axes of the elbow and wrist joints.

3. The method for evaluating the joint clearance of an industrial robot according to claim 2, characterized in that, The formula for calculating the end-effector pose increment of the industrial robot is as follows: ； ； ； ； ； In the above formula, This indicates the location of the first reflective point in the previous image. This indicates the location of the second reflective point in the previous image. This indicates the position of the first reflective point in the current image. This indicates the position of the second reflective point in the current image. This represents the increment of the end effector position of the industrial robot in the x-axis direction. This represents the increment of the end effector position of the industrial robot in the y-axis direction. This represents the increment of the end effector angle of an industrial robot. Indicates the angle of the first reflective point. This indicates the angle of the second reflective point.

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