Industrial robot calibration device and method based on laser interferometer

Abstract

The present invention provides a laser interferometer-based industrial robot calibration device and method, belonging to the technical field of industrial robot calibration. The device comprises a two-degree-of-freedom rotating bracket assembly, a laser interferometer adjustment assembly, an interferometer mirror adjustment assembly, and a reflector motion adjustment assembly, which are sequentially mounted on the two-degree-of-freedom rotating bracket assembly, and together achieve precise position adjustment of the laser interferometer and its mirror assembly. The present invention uses a laser interferometer to measure the radial length of a tool coordinate system relative to a measurement reference coordinate system, and two angle encoders to measure the azimuth and polar angle of the tool coordinate system. Based on these measured values, the position of the measurement point can be expressed in a spherical coordinate system. An industrial robot error solution model is established, and calibration system errors are identified step by step using a weighted fitness function and a particle swarm algorithm. The present invention has the advantages of a large measurement range, high measurement accuracy, and the ability to calibrate industrial robots using complex trajectories such as circular trajectories.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial robot calibration, and in particular relates to an industrial robot calibration device and method based on a laser interferometer. Background Art

[0002] Industrial robots are multi-joint manipulators or multi-degree-of-freedom machine devices widely used in the industrial field. They have a certain degree of automation and can rely on their own power and control capabilities to achieve various industrial processing and manufacturing functions.

[0003] Industrial robots play a vital role in modern manufacturing and are widely used in automated production lines, intelligent manufacturing, and other fields. Industrial robot calibration applies advanced measurement techniques to measure the position error of the industrial robot's tool coordinate system, identify the errors in the industrial robot's kinematic parameters, and improve the absolute position accuracy of the industrial robot through error compensation technology. This is crucial for achieving high-precision industrial robot operation and precision machining. Industrial robot calibration typically involves four basic steps: modeling, measurement, identification, and compensation.

[0004] Currently, commonly used industrial robot calibration devices include laser trackers, ballbars, and wire encoders. However, each of these calibration methods has its own drawbacks, primarily high cost, limited measurement range, and susceptibility to environmental influences.

[0005] For example, (1) Laser tracker: The equipment is expensive. (2) Ballbar: When the error value exceeds the allowable value, the measurement result is inaccurate. The measurement range of the ballbar is limited by the length of the ballbar. The range of the Renishaw QC20-W dual ballbar is only ±1mm, which is difficult to use for industrial robots with poor measurement accuracy. Invention patent CN106225724B is a method for calibrating the spatial error of a six-axis joint industrial robot based on a ballbar. It proposes an error calibration method that uses high-precision ballbars and circular gratings to measure the error in the robot's spatial motion and compensate the error in the robot's kinematic model. This method only measures the elevation angle between the ballbar rod and the horizontal plane, and does not measure the azimuth angle of the ballbar in the horizontal plane. It is impossible to perform position calculation and obtain accurate position data, which has certain limitations. (3) Wire encoder: The measurement error of the wire encoder will accumulate as the wire is extended and bent, which will be more obvious in long-distance measurement, affecting the measurement accuracy. Limited sensitivity: Wire draw encoders are sensitive to small wire movements or vibrations, which may lead to fluctuations and instability in measurement results.

[0006] Existing laser interferometers are usually used for position accuracy detection of equipment such as machine tools and three-dimensional coordinate measuring machines. Although they can perform high-precision position measurement, they cannot use circular trajectories to calibrate industrial robots. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide an industrial robot calibration device and method based on a laser interferometer, which has a large measurement range, high measurement accuracy, and can calibrate the industrial robot using complex trajectories such as circular trajectories.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: an industrial robot calibration device based on a laser interferometer, including a two-degree-of-freedom rotating bracket assembly, a laser interferometer adjustment assembly, an interferometer adjustment assembly, and a reflector motion adjustment assembly. The laser interferometer adjustment assembly, the interferometer adjustment assembly and the reflector motion adjustment assembly are installed in sequence on the two-degree-of-freedom rotating bracket assembly, and together realize the precise position adjustment of the laser interferometer and its mirror group.

[0009] The two-degree-of-freedom rotating bracket assembly includes a base plate, a support plate, and a slewing frame. The support plate is symmetrically fixed to the base plate, the top of the support plate is fixed to the cylindrical shaft, and the slewing frame is arranged outside the support plate and the base plate. The slewing frame is connected to the cylindrical shaft through a cylindrical roller bearing. A Y-axis angle encoder is installed on the outer side of the end of the cylindrical shaft. The cylindrical shaft is provided with a circular hole. The Y-axis angle encoder can record the rotation angle of the support plate on the Y axis; thereby realizing the free rotation of the base plate around the Y axis and the Z axis, and can record the rotation angle of the two axes in space. A bearing seat is installed at the bottom of the slewing frame. The bearing seat is fixed to the base. A tapered roller bearing and a Z-axis angle encoder are installed on the bearing seat in sequence. The rotation of the tapered roller bearing drives the rotation of the entire slewing frame around the Z axis, and the Z-axis angle encoder records the angle of rotation of the slewing frame. A front end support seat is provided at the front end position of the bottom of the base plate, and the front end support seat serves as a support and limiter. The Y-axis angle encoder and the Z-axis angle encoder are used to measure the rotation angles of the two-degree-of-freedom rotating bracket assembly in the Y-axis direction and the Z-axis direction.

[0010] It can be seen that the two-degree-of-freedom rotating bracket assembly realizes the rotation of the base plate around the Y-axis and the Z-axis, and can measure the rotation angles of the two axes.

[0011] The laser interferometer adjustment component includes a laser interferometer and a pan-tilt platform. The laser interferometer is installed on the pan-tilt platform, and the Y and Z axis positions and Y and Z axis angles of the laser interferometer are adjusted through the pan-tilt platform. The pan-tilt platform is installed on the lower base plate I, and the lower base plate I is fixed to the base plate, thereby fixing the entire laser interferometer adjustment component to the base plate.

[0012] It can be seen that the laser interferometer adjustment component can be adjusted in the Y-axis and Z-axis directions and the angle adjustment in the Z-axis and Y-axis directions.

[0013] The interferometer adjustment assembly includes an interferometer mounted on a support cylinder. The support cylinder, fixed disk I, rack-and-pinion guide pair I, and interferometer screw pair are sequentially mounted on lower base plate II from top to bottom, and lower base plate II is fixed to the base plate. The interferometer is mounted perpendicularly to rack-and-pinion guide pair I via the support cylinder and fixed disk I. The interferometer screw pair adjusts the interferometer's Z-axis position, and the rack-and-pinion guide pair I adjusts the interferometer's Y-axis position.

[0014] Among them, the interferometer performs a spectroscopic operation on the light emitted by the laser interferometer, the supporting cylinder fixes the interferometer, and the interferometer can rotate around the supporting cylinder. The supporting cylinder is tightly connected to the gear rack guide pair I through the fixed disk I. The gear rack guide pair I can realize the movement of the interferometer on the Y axis, and the interferometer can be raised and lowered through the interferometer spiral pair. The interferometer spiral pair is fixed on the lower base plate II31, and the interferometer can be raised and lowered along the Z axis and moved in the -Y axis direction.

[0015] It can be seen that the interferometer adjustment assembly can adjust the Y-axis position and Z-axis position of the interferometer;

[0016] The reflector motion adjustment assembly includes a guide rail bottom plate, a guide rail, a slider, and a guide rail top plate. The guide rail bottom plate is fixed to the bottom plate, and a guide rail is provided on the guide rail bottom plate. The guide rail top plate is mounted on the guide rail via a slider, and the movement of the guide rail top plate is achieved by the linear sliding of the slider on the guide rail. Two guide rail screw pairs are mounted on the guide rail top plate, and both guide rail screw pairs are oriented in the direction of guide rail movement. Each guide rail screw pair is mounted on a gear rack guide pair II. A reflector support cylinder is mounted on the gear rack guide pair II on the side close to the interferometer adjustment assembly. The reflector support cylinder is connected to the gear rack guide pair II via a fixed disk II. A reflector is mounted on the reflector support cylinder. The reflector is fixed by the reflector support cylinder and can rotate around the reflector support cylinder axis within a certain range. A bearing fixing seat is mounted on the gear rack guide pair II on the side away from the interferometer adjustment assembly, and a ball joint bearing is mounted on the bearing fixing seat.

[0017] The ball joint bearing is connected to the rack and pinion guide pair II via a bearing mount, enabling the reflector and ball joint bearing to move along the rack and pinion guide pair II in the Y-axis direction. The rack and pinion guide pair II is fixed to the guide screw pair, enabling it to be raised and lowered along the Z-axis.

[0018] In this way, the reflector and the ball-joint bearing can achieve translational movement in the Y-axis direction and lifting and lowering in the Z-axis. Furthermore, by cooperating with the guide rail screw pair and the guide rail top plate, the reflector and the ball-joint bearing can slide on the guide rail top plate along the guide rail direction, and the reflector and the ball-joint bearing can achieve translational movement in the X-axis direction. Because the guide rail screw pairs of the reflector and the ball-joint bearing are fixed to the guide rail top plate, the center point of the reflector's mirror surface and the center point of the spherical surface of the ball-joint bearing are in a straight line and the distance between them remains constant. Therefore, the movement distance of the ball-joint bearing can be regarded as the movement distance of the reflector relative to the interferometer.

[0019] The centerline of the circular hole passes through the intersection of the two axes of the two-degree-of-freedom rotating bracket assembly. It is a fixed point during the measurement process and serves as the origin of the measurement reference coordinate system. It is the reference point for radial length measurement. The direction of the centerline is parallel to the guide rail, providing a reference for optical path adjustment.

[0020] It can be seen that the reflector motion adjustment assembly can adjust the Y-axis position and Z-axis position of the reflector and the ball joint bearing, and realize the movement of the reflector and the ball joint bearing in the X-axis direction.

[0021] The present invention also provides an industrial robot calibration method based on a laser interferometer, comprising the following steps:

[0022] S1. Establish the basic coordinate system and flange coordinate system of the industrial robot, establish the tool coordinate system at the center of the ball joint bearing, and establish the measurement reference coordinate system on the calibration device.

[0023] Define the calibration system error vectors, such as the posture error vector of the base coordinate system relative to the measurement reference coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, and the position error vector of the tool coordinate system relative to the flange coordinate system. Establish an error solution model and establish the mapping relationship between the calibration system error and the position error of the robot tool coordinate system relative to the measurement reference coordinate system under the condition of known industrial robot joint angle.

[0024] Furthermore, in step S1, the pose transformation parameters of the base coordinate system relative to the measurement reference coordinate system are defined as , and define its error vector as , the homogeneous transformation matrix of the base coordinate system relative to the measurement reference coordinate system is:

[0025] in, is the homogeneous transformation matrix of the robot base coordinate system relative to the measurement reference coordinate system; The position of the base coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the z-axis direction; is the angle of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; is the angle of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; is the angle of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system; is the error vector of the base coordinate system relative to the measurement reference coordinate system; The position error of the basic coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the z-axis direction; The angular error of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; The angular error of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; It is the angular error of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system.

[0026] According to the MD-H parameter method, the industrial robot joint coordinate system is established, and the transformation relationship between two adjacent joint coordinate systems is determined by the joint length , joint angle , rod length , member torsion angle , the angle of rotation of two adjacent joint axes around the y-axis Five parameter description. Considering the kinematic parameter error of industrial robots, is the joint length error, is the joint angle error; is the length error of the rod; is the torsion angle error of the member; is the angular error of the rotation of two adjacent joint axes around the y-axis. When the two adjacent joint axes are not parallel, Define the kinematic parameter error vector of the joint i-1 reference coordinate system relative to the joint i reference coordinate system, , the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system is defined as .

[0027] The homogeneous transformation matrix of the joint i reference coordinate system with parameter error relative to the joint i-1 reference coordinate system is:

[0028]

[0029] The homogeneous transformation matrix of the flange coordinate system of the n-degree-of-freedom industrial robot relative to the base coordinate system is:

[0030]

[0031] The above formula is the kinematic model of an n-degree-of-freedom industrial robot including kinematic parameter errors.

[0032] in, is the homogeneous transformation matrix of the flange coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the first joint coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the robot flange coordinate system relative to the n-1th joint.

[0033] Considering the installation error of the measuring tool, the position coordinates of the tool coordinate system relative to the flange coordinate system are defined as , and define its error vector as , the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system is:

[0034]

[0035] in, is the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system; is the position error of the tool coordinate system relative to the flange coordinate system in the x, y, and z axis directions;

[0036] The homogeneous transformation matrix of the tool coordinate system relative to the measurement reference coordinate system is:

[0037]

[0038] The above formula is the error solution model of the n-DOF industrial robot, and the definition is To solve the position.

[0039] S2. Design a set of circular trajectories in the robot's workspace , the center of the circle is , with a radius of R. These circular trajectories have a certain angle with the horizontal plane, so that each joint will move, and then all kinematic parameter errors will be reflected in the measured position data. N measurement points are evenly divided on the circular trajectory, and the coordinate values ​​of the N measurement points are input into the industrial robot. With the basic coordinate system as a reference, the calibration device is installed so that the origin of the measurement reference coordinate system is located at the center of the circle. , adjust the light path.

[0040] The industrial robot moves along a circular trajectory, stops at each measurement point and records data. The laser interferometer measures the radial length of the tool coordinate system relative to the measurement reference coordinate system, and the two angle encoders measure the azimuth and polar angle of the tool coordinate system, that is, the i-th measurement point Spherical coordinates in the measurement reference coordinate system , the position measured by this calibration device Defined as the measurement position of the i-th measurement point.

[0041] In order to facilitate the optimization and solution of the identification and calibration system error in the next step, transform it into rectangular coordinates and set the point The rectangular coordinates are , can be obtained by the following formula:

[0042]

[0043] in, is the position coordinate of the i-th measurement point in the measurement reference coordinate system; is the radial length of the i-th measurement point measured by this calibration device; is the azimuth of the i-th measurement point measured by this calibration device; is the polar angle of the i-th measurement point measured by this calibration device.

[0044] Furthermore, in step S2, a laser interferometer, its lens assembly, and an industrial robot are prepared, the laser interferometer is mounted on a pan-tilt platform, the interferometer is mounted on an interferometer adjustment assembly, and the reflector is mounted on a reflector motion adjustment assembly. Using the guide rail as a reference, the position and direction of the laser interferometer, as well as the Z-axis and Y-axis positions of the interferometer, reflector, and ball joint bearing are adjusted to ensure normal measurement.

[0045] Furthermore, the optical path adjustment method is as follows;

[0046] Using the circular hole on the cylindrical shaft as a reference, adjust the Y and Z axis positions of the laser interferometer via the pan / tilt system so that the light it emits passes through the circular hole on the cylindrical shaft and exits. Adjust the Z and Y axis positions of the spherical joint bearing so that the light hits the marked point on the spherical joint bearing, indicating that the light can pass through the center of the spherical joint bearing (the origin of the measurement reference coordinate system). Adjust the Y and Z axis angles of the laser interferometer so that the light direction is parallel to the movement direction of the spherical joint bearing; adjust the Z and Y axis positions of the interferometer and reflector so that the light passes through the interferometer and reflector and returns to the laser interferometer receiving hole; fine-tune the Z and Y axis positions of the reflector and interferometer so that the two light rays overlap and enter the optical gate receiving hole, causing interference. All the laser interferometer indicators turn green.

[0047] The gripper of the industrial robot is controlled to grab the end of the ball joint bearing and move along a circular trajectory. It stops at each measurement point and records data. The radial length of the robot tool coordinate system relative to the measurement reference coordinate system is measured by a laser interferometer. The two angle encoders measure the azimuth and polar angle of the robot tool coordinate system, i.e., the i-th measurement point. Spherical coordinates in the measurement reference coordinate system , which is defined as the measurement position of the i-th measurement point.

[0048] S3. Particle swarm optimization has the advantages of simple principle, easy implementation, high precision and fast convergence. Therefore, the particle swarm optimization is used to optimize the calibration system error.

[0049] Substituting the joint angle corresponding to the i-th measurement point and the set calibration system error into the error solution model, the solution position of the i-th measurement point can be calculated , define the radial length difference between the i-th measurement point and the i+1-th measurement point as :

[0050]

[0051] in, is the radial length difference between the i-th measurement point and the i+1-th measurement point obtained using the industrial robot error solution model; The industrial robot error solution model calculates the position coordinates of the i-th measurement point; The industrial robot error solution model calculates the position coordinates of the i+1th measurement point;

[0052] The difference in radial length between the i-th measuring point and the i+1-th measuring point is defined as :

[0053]

[0054] in, The radial length of the i+1th measurement point measured by this calibration device;

[0055] Set up a weighted fitness function based on position and radial length:

[0056] in, ,

[0057] The fitness function is a weighted sum of the root mean square of the deviations between the calculated and measured positions of all measurement points and the root mean square of the deviations between the calculated and measured radial length differences of all adjacent measurement points. The radial length can mitigate the effects of angle encoder errors on the measured values, while the difference method can mitigate the effects of initial laser interferometer value settings on the measurement results.

[0058] The boundary conditions for calibrating the system error vector are set based on the accuracy level of the angle encoder and the machining accuracy level of the rod. The algorithm parameters are set, the particle swarm algorithm is initialized, and the appropriate algorithm parameters are found using the simulated position data. The measured position data is used for a step-by-step optimization solution. The algorithm terminates if the maximum number of iterations is reached or the fitness value meets the set value.

[0059] Furthermore, in step 3, the closer the systematic error set in the optimization solution is to the true value, the smaller the value of the fitness function is.

[0060] The optimization process is divided into three steps:

[0061] S31. Simulation verification: use simulation data to find appropriate algorithm parameters, set a set of calibration system errors, use the error solution model to calculate the solution positions of N measurement points as the simulation data of their measurement positions, set k1=1, k2=0, set the boundary conditions of the calibration system errors according to the accuracy level of the angle encoder and the processing accuracy level of the rod, set the algorithm parameters, initialize the particle swarm algorithm, use the simulation data of the measurement positions of N measurement points to iteratively solve, and judge whether the maximum number of iterations is reached or the fitness value meets the set value. If the optimal value is consistent with or close to the set calibration system error value, it means that the measurement point data can meet the solution requirements and the parameter settings are reasonable. If the requirements are not met, adjust the parameters or increase the number of measurement points until the termination conditions are met, so as to find the appropriate number of particles, number of variables, individual acceleration constant, social acceleration constant, inertia weight, maximum speed, number of iterations and other algorithm parameters;

[0062] S32, using the algorithm parameters obtained in step S31 to initialize the particle swarm algorithm, set k1=1, k2=0, use the measurement position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position;

[0063] S33, with the global optimal value of the particle swarm output in step S32 and its corresponding position as a reference, modify the boundary conditions, reduce the search range, adjust the weighting coefficient, use the measurement position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position.

[0064] S4. Correct the nominal parameters of the industrial robot according to the kinematic parameter errors of the robot flange coordinate system relative to the base coordinate system in the identification result of step S3 to achieve compensation, thereby improving the absolute position accuracy of the industrial robot.

[0065] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0066] The present invention designs a device for calibrating industrial robots using a laser interferometer and a length mirror group. The device has an optical path adjustment function and can use complex trajectories such as circular trajectories to calibrate industrial robots. It has the advantages of a large measurement range and high measurement accuracy, and at the same time expands the use of laser interferometers.

[0067] At the same time, the present invention proposes a method for identifying calibration system errors in steps based on a weighted fitness function based on position and radial length and using a particle swarm algorithm. The weighting coefficient can be dynamically adjusted during the optimization solution process to reduce the influence of the angle error and the error in the initial value setting of the laser interferometer on the measurement results, adjust the value range of the calibration system error to be identified, and improve the accuracy of identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The present invention will be described in detail below with reference to the accompanying drawings and in combination with examples, and the advantages and implementation modes of the present invention will become more apparent. The contents shown in the accompanying drawings are only used to illustrate the present invention and do not constitute any limitation to the present invention. In the accompanying drawings:

[0069] Figure 1 It is a structural schematic diagram of the present invention.

[0070] Figure 2 It is a structural schematic diagram of the two-degree-of-freedom rotating bracket assembly of the present invention.

[0071] Figure 3 It is a structural schematic diagram of the rotary frame of the present invention.

[0072] Figure 4 It is a structural schematic diagram of the laser interferometer adjustment component of the present invention.

[0073] Figure 5 It is a structural schematic diagram of the interferometer adjustment assembly of the present invention.

[0074] Figure 6 It is a structural schematic diagram of the reflector motion adjustment assembly of the present invention.

[0075] Figure 7 It is a structural schematic diagram of the guide rail of the present invention.

[0076] Figure 8 It is a schematic diagram of the coordinate system of the present invention.

[0077] Figure 9 It is a schematic diagram of the optical path adjustment principle of the present invention.

[0078] Figure 10 It is a principle diagram of the fitness function of the present invention.

[0079] Figure 11 4 is a flow chart of the calibration method of the present invention.

[0080] In the picture:

[0081] 1. Two-degree-of-freedom rotation bracket assembly; 2. Laser interferometer adjustment assembly; 3. Interferometer adjustment assembly; 4. Reflector motion adjustment assembly;

[0082] 11. Bearing seat; 12. Tapered roller bearing; 13. Z-axis angle encoder; 14. Rotating frame; 15. Support plate; 16. Cylindrical roller bearing; 17. Y-axis angle encoder; 18. Cylindrical shaft; 19. Base plate; 110. Front support seat;

[0083] 21. Lower base plate I; 22. Laser interferometer; 23. PTZ; 24. Optical shutter receiving hole;

[0084] 31. Lower base plate II; 32. Interferometer screw pair; 33. Fixed disk I; 34. Interferometer; 35. Support cylinder; 36. Gear rack guide pair I;

[0085] 41. Guide rail bottom plate; 42. Guide rail; 43. Slider; 44. Guide rail top plate; 45. Fixed disc II; 46. Reflector support cylinder; 47. Reflector; 48. Ball joint bearing; 49. Bearing fixing seat; 410. Gear rack guide pair II; 411. Guide rail screw pair. DETAILED DESCRIPTION

[0086] like Figures 1 to 7 As shown, the present invention is an industrial robot calibration device based on a laser interferometer, which includes a two-degree-of-freedom rotating bracket assembly 1, a laser interferometer adjustment assembly 2, an interferometer adjustment assembly 3, and a reflector motion adjustment assembly 4. The laser interferometer adjustment assembly 2, the interferometer adjustment assembly 3, and the reflector motion adjustment assembly 4 are sequentially installed on the two-degree-of-freedom rotating bracket assembly 1, and together realize the precise position adjustment of the laser interferometer and its mirror group.

[0087] like Figure 2 and Figure 3As shown, the two-degree-of-freedom rotating bracket assembly 1 includes a base plate 19, a support plate 15 and a rotating frame 14. The support plate 15 is symmetrically fixed on the base plate 19. The top of the support plate 15 is fixed to the cylindrical shaft 18. The rotating frame 14 is arranged on the outside of the support plate 15 and the base plate 19. The rotating frame 14 is connected to the cylindrical shaft 18 through a cylindrical roller bearing 16. A Y-axis angle encoder 17 is installed on the outside of the end of the cylindrical shaft 18. A circular hole is provided on the cylindrical shaft 18. The Y-axis angle encoder 17 can record the rotation angle of the support plate 15 on the Y-axis; a bearing seat 11 is installed at the bottom of the rotating frame 14, and the bearing seat 11 is fixed to the base. A tapered roller bearing 12 and a Z-axis angle encoder 13 are sequentially installed on the bearing seat 11. The rotation of the tapered roller bearing 12 drives the entire rotating frame 14 to rotate around the Z-axis, and the Z-axis angle encoder 13 records the angle of rotation of the rotating frame 14. A front support seat 110 is provided at the front end of the bottom of the base plate 19, and the front support seat 110 plays a supporting and limiting role. The Y-axis angle encoder 17 and the Z-axis angle encoder 13 are used to measure the rotation angle of the two-degree-of-freedom rotating bracket assembly 1 in the Y-axis direction and the Z-axis direction.

[0088] It can be seen that the two-degree-of-freedom rotating bracket assembly 1 realizes the rotation of the base plate 19 around the Y axis and the Z axis, and can measure the rotation angles of the two axes.

[0089] Among them, the tapered roller bearing 12 model is GB 297-2015 30205, with an inner diameter of 25mm and an outer diameter of 52mm; the cylindrical roller bearing 16 model is GB 283-2021 N202E, with an inner diameter of 15mm and an outer diameter of 35mm.

[0090] like Figure 4 As shown, the laser interferometer adjustment component 2 includes a laser interferometer 22 and a pan-tilt platform 23. The laser interferometer 22 is installed on the pan-tilt platform 23. The Y and Z axis positions and Y and Z axis angles of the laser interferometer 22 are adjusted through the pan-tilt platform 23. The pan-tilt platform 23 is installed on the lower base plate I21, and the lower base plate I21 is fixed on the base plate 19, thereby fixing the entire laser interferometer adjustment component 2 on the base plate 19.

[0091] It can be seen that the laser interferometer adjustment component 2 can perform adjustments in the Y-axis and Z-axis directions and angle adjustments in the Z-axis and Y-axis directions.

[0092] like Figure 5As shown, the interferometer adjustment assembly 3 includes an interferometer 34, which is mounted on a support cylinder 35. The support cylinder 35, fixed disk I 33, rack and pinion guide pair I 36 (a precision rack and pinion guide pair is used in this embodiment), and interferometer screw pair 32 are mounted on the lower base plate II 31 in order from top to bottom. The lower base plate II 31 is fixed to the base plate 19. The interferometer 34 is mounted perpendicularly to the rack and pinion guide pair I 36 through the support cylinder 35 and fixed disk I 33. The interferometer screw pair 32 can adjust the Z-axis position of the interferometer 34, and the rack and pinion guide pair I 36 can adjust the Y-axis position of the interferometer 34.

[0093] Among them, the interferometer 34 performs a spectroscopic operation on the light emitted by the laser interferometer 22, and the support cylinder 35 fixes the interferometer 34. The interferometer 34 can rotate around the support cylinder 35. The support cylinder 35 is tightly connected to the gear rack guide pair Ⅰ36 through the fixed disk Ⅰ33. The gear rack guide pair Ⅰ36 can realize the movement of the interferometer on the Y axis, and the interferometer 34 can be raised and lowered through the interferometer spiral pair 32. The interferometer spiral pair 32 is fixed on the lower base plate Ⅱ31, and the interferometer 34 can be raised and lowered along the Z axis and moved in the Y axis direction.

[0094] It can be seen that the interferometer adjustment assembly 3 can adjust the Y-axis position and the Z-axis position of the interferometer 34;

[0095] like Figure 6 and Figure 7 As shown, the reflector motion adjustment assembly 4 includes a guide rail lower base plate 41, a guide rail 42, a slider 43 and a guide rail top plate 44. The guide rail lower base plate 41 is fixed on the base plate 19, and the guide rail 42 is provided on the guide rail lower base plate 41. The guide rail top plate 44 is installed on the guide rail 42 through the slider 43, and the movement of the guide rail top plate 44 is realized by the linear sliding of the slider 43 on the guide rail 42. Two guide rail spiral pairs 411 are installed on the guide rail top plate 44, and each guide rail spiral pair 411 is installed with a gear rack guide pair II 410 (this embodiment uses a precision gear rack guide pair), and a reflector support cylinder 46 is installed on the gear rack guide pair II 410 close to the side of the interferometer adjustment component 3. The reflector support cylinder 46 is connected to the gear rack guide pair II 410 through a fixed disk II 45. A reflector 47 is installed on the reflector support cylinder 46, and the reflector 47 is fixed by the reflector support cylinder 46 and can rotate within a certain range around the axis of the reflector support cylinder 46; a bearing fixing seat 49 is installed on the gear rack guide pair II 410 away from the side of the interferometer adjustment component 3, and a ball joint bearing 48 is installed on the bearing fixing seat 49.

[0096] The ball joint bearing 48 is connected to the gear rack guide pair II 410 through the bearing fixing seat 49, which enables the reflector 47 and the ball joint bearing 48 to move along the gear rack guide pair II 410 in the Y-axis direction. The gear rack guide pair II 410 is fixed on the guide screw pair 411 to achieve the function of lifting and lowering along the Z-axis direction. The ball joint bearing 48 model is SRJ016C, with an outer diameter of 56mm and a swing accuracy of .

[0097] In this way, the reflector 47 and the ball-joint bearing 48 can achieve translation in the Y-axis direction and lifting and lowering in the Z-axis. Then, through the cooperation of the guide rail screw pair 411 and the guide rail top plate 44, the reflector 47 and the ball-joint bearing 48 can slide on the guide rail top plate 44 along the guide rail 42, and the reflector 47 and the ball-joint bearing 48 can achieve translation in the X-axis direction. Because the guide rail screw pairs 411 of the reflector 47 and the ball-joint bearing 48 are fixed to the guide rail top plate 44, the center point of the mirror surface of the reflector 47 and the center point of the spherical surface of the ball-joint bearing 48 are in a straight line and the distance between them is constant. Therefore, the movement distance of the ball-joint bearing 48 can be regarded as the movement distance of the reflector 47 relative to the interferometer 34.

[0098] The centerline of the circular hole passes through the intersection of the two axes of the two-degree-of-freedom rotating bracket assembly 1. It is a fixed point during the measurement process and serves as the origin of the measurement reference coordinate system. It is the reference point for radial length measurement. The direction of the centerline is parallel to the guide rail 42, providing a reference for optical path adjustment.

[0099] It can be seen that the reflector motion adjustment assembly 4 can adjust the Y-axis position and the Z-axis position of the reflector 47 and the ball joint bearing 48, and realize the movement of the reflector 47 and the ball joint bearing 48 in the X-axis direction.

[0100] The present invention also provides an industrial robot calibration method based on a laser interferometer, comprising the following steps:

[0101] S1, such as Figures 8 to 11 As shown, the basic coordinate system and flange coordinate system of the industrial robot are established, the tool coordinate system is established at the center of the ball joint bearing 48, and the measurement reference coordinate system is established on the calibration device.

[0102] Define the calibration system error vectors such as the posture error vector of the base coordinate system relative to the measurement reference coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, and the position error vector of the tool coordinate system relative to the flange coordinate system, and establish an error solution model.

[0103] Considering the error of the base coordinate system relative to the measurement reference coordinate system, the pose transformation parameters of the base coordinate system relative to the measurement reference coordinate system are defined as , and define its error vector as , the homogeneous transformation matrix of the base coordinate system relative to the measurement reference coordinate system is:

[0104] in, is the homogeneous transformation matrix of the robot base coordinate system relative to the measurement reference coordinate system; The position of the base coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the z-axis direction; is the angle of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; is the angle of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; is the angle of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system; is the error vector of the base coordinate system relative to the measurement reference coordinate system; The position error of the basic coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the z-axis direction; The angular error of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; The angular error of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; It is the angular error of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system.

[0105] In this embodiment, the parameters of the robot are shown in Table 1.

[0106] Table 1 ABBIRB120 robot DH parameters

[0107]

[0108] According to the MD-H parameter method, the industrial robot joint coordinate system is established, and the transformation relationship between two adjacent joint coordinate systems is determined by the joint length , joint angle , rod length , member torsion angle , the angle of rotation of two adjacent joint axes around the y-axis Five parameter description. Considering the kinematic parameter error of industrial robots, is the joint length error, is the joint angle error; is the length error of the rod; is the torsion angle error of the member; is the angular error of the rotation of two adjacent joint axes around the y-axis. When the two adjacent joint axes are not parallel, Define the kinematic parameter error vector of the joint i-1 reference coordinate system relative to the joint i reference coordinate system, , the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system is defined as .

[0109] The homogeneous transformation matrix of the joint i reference coordinate system with parameter error relative to the joint i-1 reference coordinate system is:

[0110]

[0111] The homogeneous transformation matrix of the flange coordinate system of the n-degree-of-freedom industrial robot relative to the base coordinate system is:

[0112]

[0113] The above formula is the kinematic model of an n-degree-of-freedom industrial robot including kinematic parameter errors.

[0114] in, is the homogeneous transformation matrix of the flange coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the first joint coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the robot flange coordinate system relative to the n-1th joint.

[0115] Considering the installation error of the measuring tool, the position coordinates of the tool coordinate system relative to the flange coordinate system are defined as , and define its error vector as , the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system is:

[0116]

[0117] in, is the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system; is the position error of the tool coordinate system relative to the flange coordinate system in the x, y, and z axis directions;

[0118] The homogeneous transformation matrix of the tool coordinate system relative to the measurement reference coordinate system is:

[0119]

[0120] The above formula is the error solution model of the n-DOF industrial robot, and the definition is To solve the position; is the posture matrix of the measurement tool coordinate system relative to the measurement reference coordinate system; is the position vector of the measurement tool coordinate system relative to the measurement reference coordinate system.

[0121] S2. Determine a set of circular trajectories in the robot workspace , the center of the circle is , with a radius of R. These circular trajectories have a certain angle with the horizontal plane, so that each joint will move, and then all kinematic parameter errors will be reflected in the measured position data. N measurement points are evenly divided on the circular trajectory, and the coordinate values ​​of the N measurement points are input into the industrial robot. The installation position of this calibration device is determined with reference to the basic coordinate system, and the device is fixed so that the origin of the measurement reference coordinate system is at the center of the circle. , adjust the light path.

[0122] Prepare the laser interferometer and its mirror assembly and industrial robot, install the laser interferometer on the pan-tilt head, install the interferometer on the interferometer adjustment assembly, install the reflector on the reflector motion adjustment assembly, and use guide rail 42 as a reference to adjust the position and direction of the laser interferometer, as well as the Z-axis and Y-axis positions of the interferometer, reflector, and ball joint bearing to ensure normal measurement.

[0123] Optical path adjustment method Figure 9 As shown, with the circular hole on the cylindrical shaft 18 as a reference, the Y and Z axis positions of the laser interferometer 22 are adjusted through the pan-tilt platform 23 so that the light emitted by it passes through the circular hole on the cylindrical shaft 18 and is emitted. The Z axis position and Y axis position of the ball joint bearing 48 are adjusted through the gear rack guide pair II 410 and the guide screw pair 411 so that the light is projected onto the marked point of the ball joint bearing 48, indicating that the light can pass through the center of the ball joint bearing 48. The Y and Z axis direction angles of the laser interferometer 22 are adjusted so that the direction of the light is parallel to the moving direction of the ball joint bearing.

[0124] Adjust the Z-axis position and Y-axis position of the interferometer 34 through the gear rack guide pair I 36 and the interferometer screw pair 32, so that the light passes through the interferometer 34 and returns to the receiving hole of the laser interferometer 22; adjust the Z-axis position and Y-axis position of the reflector 47 through the gear rack guide pair II 410 and the guide screw pair 411, so that the light returns to the laser interferometer light gate receiving hole 24 after reaching the interferometer, fine-tune the Z-axis position and Y-axis position of the reflector and interferometer, so that the two light rays overlap and enter the light gate receiving hole 24 to generate interference, and all the indicator lights of the laser interferometer 22 turn green.

[0125] The gripper of the industrial robot is controlled to grasp the end of the ball joint bearing 48 and move along a circular trajectory. It stops at each measurement point and records data. The radial length of the robot tool coordinate system relative to the measurement reference coordinate system is measured by the laser interferometer 22. The two angle encoders measure the azimuth and polar angle of the robot tool coordinate system, i.e., the i-th measurement point. Spherical coordinates in the measurement reference coordinate system , which is defined as the measurement position of the i-th measurement point.

[0126] Set up a point The rectangular coordinates are , can be obtained by the following formula:

[0127]

[0128] in, is the position coordinate of the i-th measurement point in the measurement reference coordinate system (the position coordinate of the robot tool coordinate system relative to the measurement reference coordinate system in the rectangular coordinate system measured by the laser interferometer); is the radial length of the i-th measurement point measured by this calibration device; is the azimuth of the i-th measurement point measured by this calibration device; is the polar angle of the i-th measurement point measured by this calibration device.

[0129] S3, such as Figure 10 As shown, is the actual robot base coordinate system, is the actual flange coordinate system, is the nominal tool coordinate system origin, is the nominal laser interferometer system measurement reference coordinate system, The actual laser interferometer system measures the reference coordinate system, is the actual origin of the tool coordinate system, is the basic coordinate system for the solution, To solve the flange coordinate system, is the origin of the tool coordinate system to be solved, is the actual tool coordinate system.

[0130] Without considering the measurement error, the error of the transformation parameter of the solved basic coordinate system relative to the measurement reference coordinate system approaches the actual value, that is, , the kinematic parameter error of the flange coordinate system relative to the base coordinate system approaches the actual value, that is, , the position error of the tool coordinate system relative to the flange coordinate system is close to the actual value, that is, , then:

[0131]

[0132] Therefore, there exists a set of error parameters such that .

[0133] The particle swarm algorithm has the advantages of simple principle, easy implementation, high precision and fast convergence. Therefore, the particle swarm algorithm is used to optimize and solve the calibration system error. The radial length can avoid the interference of the angle encoder error on the measurement value, and the difference method can avoid the influence of the initial value setting error of the laser interferometer on the measurement result.

[0134] Substituting the joint angle corresponding to the i-th measurement point and the set calibration system error into the error solution model, the solution position of the i-th measurement point can be calculated , define the radial length difference between the i-th measurement point and the i+1-th measurement point as :

[0135]

[0136] in, is the radial length difference between the i-th measurement point and the i+1-th measurement point obtained using the industrial robot error solution model; The industrial robot error solution model calculates the position coordinates of the i-th measurement point; The industrial robot error solution model calculates the position coordinates of the i+1th measurement point;

[0137] The difference in radial length between the i-th measuring point and the i+1-th measuring point is defined as :

[0138]

[0139] in, The radial length of the i+1th measurement point measured by this calibration device;

[0140] Set up a weighted fitness function based on position and radial length:

[0141] Where f is the fitness function, which is the weighted sum of the root mean square of the deviation between the position measured by all measurement points and the position calculated by the error solution model and the root mean square of the deviation between the radial length difference calculated by all adjacent measurement points and the measured radial length difference; k1 and k2 are weighting coefficients, .

[0142] The fitness function is a weighted sum of the root mean square of the deviation between the calculated and measured positions of all measurement points and the root mean square of the deviation between the calculated and measured radial length differences of all adjacent measurement points. The radial length can prevent the interference of angle encoder errors on the measured values, and the difference method can prevent the influence of the initial value setting error of the laser interferometer on the measurement results. The closer the calibration system error solved by optimization is to the true value, the smaller the value of the fitness function. The optimization process is divided into three steps:

[0143] S31. Simulation verification: use simulation data to find appropriate algorithm parameters, use random numbers to set a set of error values, use the error solution model to calculate the solution positions of N measurement points, and use them as simulation data of the measurement positions of the N measurement points. Let k1=1, k2=0, set the boundary conditions of the calibration system error according to the accuracy level of the angle encoder and the processing accuracy level of the rod, set the algorithm parameters, initialize the particle swarm algorithm, and use the simulation data of the measurement positions of the N measurement points to iteratively solve the problem, and judge whether the maximum number of iterations is reached or the fitness value meets the set value. If the optimal value is consistent with or close to the set calibration system error value, it means that the measurement point data can meet the solution requirements and the parameter settings are reasonable. If the requirements are not met, adjust the parameters or increase the number of measurement points until the termination conditions are met, so as to find the appropriate number of particles, number of variables, individual acceleration constant, social acceleration constant, inertia weight, maximum speed, number of iterations and other algorithm parameters.

[0144] S32, using the algorithm parameters obtained in step S31 to initialize the particle swarm algorithm, set k1=1, k2=0, use the measurement position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position;

[0145] S33, with the global optimal value of the particle swarm output in step S32 and its corresponding position as a reference, modify the boundary conditions, reduce the search range, adjust the weighting coefficient, use the measurement position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position.

[0146] S4. Correcting the nominal parameters of the industrial robot according to the kinematic parameter errors of the robot flange coordinate system relative to the base coordinate system in the identification result of step S3, thereby improving the absolute position accuracy of the industrial robot.

[0147] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.

Claims

1. An industrial robot calibration device based on a laser interferometer, characterized by: It includes a two-degree-of-freedom rotating bracket assembly, a laser interferometer adjustment assembly, an interferometer adjustment assembly, and a reflector motion adjustment assembly. The laser interferometer adjustment assembly, the interferometer adjustment assembly, and the reflector motion adjustment assembly are sequentially installed on the two-degree-of-freedom rotating bracket assembly. The two-degree-of-freedom rotating bracket assembly includes a base plate, a support plate and a rotating frame, the support plate is symmetrically fixed on the base plate, the top of the support plate is fixed to the cylindrical shaft, the rotating frame is connected to the cylindrical shaft, a Y-axis angle encoder is installed on the outer side of the end of the cylindrical shaft, and a circular hole is provided on the cylindrical shaft; a bearing seat is installed at the bottom of the rotating frame, a Z-axis angle encoder is installed on the bearing seat, the rotating frame rotates around the Z-axis of the bearing seat, and the Y-axis angle encoder and the Z-axis angle encoder are used to record the rotation angles of the two-degree-of-freedom rotating bracket assembly in the Y-axis direction and the Z-axis direction; The laser interferometer adjustment assembly includes a laser interferometer and a pan-tilt platform. The laser interferometer is mounted on the pan-tilt platform, and the Y and Z axis positions and Y and Z axis angles of the laser interferometer are adjusted by the pan-tilt platform. The interferometer adjustment assembly includes an interferometer, which is vertically mounted on a rack and pinion guide pair I through a supporting cylinder and a fixed disk I. The rack and pinion guide pair I is mounted on an interferometer screw pair, and the interferometer screw pair adjusts the Z-axis position of the interferometer; the rack and pinion guide pair I adjusts the Y-axis position of the interferometer; The reflector motion adjustment assembly includes a guide rail, a slider and a guide rail top plate, the guide rail top plate is installed on the guide rail through the slider, two guide rail screw pairs are installed on the guide rail top plate, each guide rail screw pair is installed with a gear rack guide pair II, so that the reflector can be lifted and lowered along the Z-axis direction, and the gear rack guide pair II close to the side of the interferometer adjustment assembly is installed with a reflector support cylinder, the reflector support cylinder is connected to the gear rack guide pair II through a fixed disk II, and the reflector support cylinder is installed with a reflector; the gear rack guide pair II away from the side of the interferometer adjustment assembly is installed with a bearing fixing seat, and the ball hinge bearing is installed on the bearing fixing seat, so that the reflector and the ball hinge bearing can be moved along the gear rack guide pair II in the Y-axis direction; the center line of the circular hole passes through the intersection of the two axes of the two-degree-of-freedom rotating bracket assembly, is a fixed point during the measurement process, serves as the origin of the measurement reference coordinate system, and is the reference point for radial length measurement, and the direction of the center line is parallel to the guide rail.

2. The industrial robot calibration device based on laser interferometer according to claim 1, characterized in that: A front end support seat is provided at the front end of the bottom of the base plate.

3. A laser interferometer-based industrial robot calibration method, implemented based on the laser interferometer-based industrial robot calibration device according to claim 1 or 2, characterized in that: The following steps are involved: S1. Establish a base coordinate system and flange coordinate system for the industrial robot, establish a tool coordinate system at the center of the ball joint bearing, establish a measurement reference coordinate system on the calibration device, define the pose error vector of the base coordinate system relative to the measurement reference coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system, and the position error vector of the tool coordinate system relative to the flange coordinate system as the calibration system error vector, establish an error solution model, and establish a mapping relationship between the calibration system error under the condition of known industrial robot joint angles and the position error of the robot tool coordinate system relative to the measurement reference coordinate system; S2. Design a circular trajectory in the robot's workspace , the center of the circle is , the radius is R, the circular trajectory has a certain angle with the horizontal plane, so that each joint produces movement, and all kinematic parameter errors are reflected in the measured position data. N measurement points are evenly divided on the circular trajectory, and the coordinate values ​​of the N measurement points are input into the industrial robot. With the basic coordinate system as a reference, the calibration device is installed so that the origin of the measurement reference coordinate system is located at the center of the circle. , adjust the light path; S3, using particle swarm optimization to optimize and solve the calibration system error; S4. Correct the nominal parameters of the industrial robot according to the kinematic parameter errors of the robot flange coordinate system relative to the base coordinate system in the result of step S3 to achieve compensation.

4. The industrial robot calibration method based on laser interferometer according to claim 3, characterized in that: In step S1, the pose transformation parameters of the base coordinate system relative to the measurement reference coordinate system are defined as , and define its error vector as , the homogeneous transformation matrix of the base coordinate system relative to the measurement reference coordinate system is: in, is the homogeneous transformation matrix of the robot base coordinate system relative to the measurement reference coordinate system; The position of the base coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position of the base coordinate system relative to the measurement reference coordinate system in the z-axis direction; is the angle of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; is the angle of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; is the angle of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system; is the error vector of the base coordinate system relative to the measurement reference coordinate system; The position error of the basic coordinate system relative to the measurement reference coordinate system in the x-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the y-axis direction; The position error of the basic coordinate system relative to the measurement reference coordinate system in the z-axis direction; The angular error of the x-axis of the base coordinate system relative to the x-axis of the measurement reference coordinate system; The angular error of the y-axis of the base coordinate system relative to the y-axis of the measurement reference coordinate system; The angular error of the z-axis of the base coordinate system relative to the z-axis of the measurement reference coordinate system; According to the MD-H parameter method, the industrial robot joint coordinate system is established, and the transformation relationship between two adjacent joint coordinate systems is determined by the joint length , joint angle , rod length , member torsion angle , the angle of rotation of two adjacent joint axes around the y-axis Five parameter descriptions, considering the kinematic parameter errors of industrial robots, is the joint length error, is the joint angle error; is the length error of the rod; is the torsion angle error of the member; is the angular error of the rotation of two adjacent joint axes around the y-axis. When the two adjacent joint axes are not parallel, , defines the kinematic parameter error vector of the joint i-1 reference coordinate system relative to the joint i reference coordinate system, , the kinematic parameter error vector of the flange coordinate system relative to the base coordinate system is defined as , The homogeneous transformation matrix of the joint i reference coordinate system with parameter error relative to the joint i-1 reference coordinate system is: The homogeneous transformation matrix of the flange coordinate system of the n-degree-of-freedom industrial robot relative to the base coordinate system is: The above formula is the kinematic model of an n-DOF industrial robot with kinematic parameter errors. in, is the homogeneous transformation matrix of the flange coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the first joint coordinate system relative to the base coordinate system; is the homogeneous transformation matrix of the robot flange coordinate system relative to the n-1th joint, Define the position coordinates of the tool coordinate system relative to the flange coordinate system as , and define its error vector as , the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system is: in, is the homogeneous transformation matrix of the tool coordinate system relative to the flange coordinate system; is the position error of the tool coordinate system relative to the flange coordinate system in the x, y, and z axis directions; The homogeneous transformation matrix of the tool coordinate system relative to the measurement reference coordinate system is: The above formula is n The error solution model of the DOF industrial robot, where To solve for the position, is the posture matrix of the measurement tool coordinate system relative to the measurement reference coordinate system; is the position vector of the measurement tool coordinate system relative to the measurement reference coordinate system.

5. The industrial robot calibration method based on laser interferometer according to claim 4, characterized in that: In step S2, the industrial robot moves along a circular trajectory, stops at each measurement point and records data. The laser interferometer measures the radial length of the tool coordinate system relative to the measurement reference coordinate system, and the two angle encoders measure the azimuth and polar angle of the tool coordinate system. The i-th measurement point Spherical coordinates in the measurement reference coordinate system , the position measured by this calibration device is defined as the measurement position of the i-th measurement point, In order to facilitate the optimization and solution of the identification and calibration system error in the next step, transform it into rectangular coordinates and set the point The rectangular coordinates are , obtained by the following formula: in, is the position coordinate of the i-th measurement point in the measurement reference coordinate system; is the radial length of the i-th measurement point measured by this calibration device; is the azimuth of the i-th measurement point measured by this calibration device; is the polar angle of the i-th measurement point measured by this calibration device.

6. The industrial robot calibration method based on laser interferometer according to claim 5, characterized in that: In step S2, prepare the laser interferometer and its mirror group and the industrial robot, install the laser interferometer on the pan-tilt head, install the interferometer on the interferometer adjustment assembly, install the reflector on the reflector motion adjustment assembly, and adjust the position and direction of the laser interferometer, as well as the Z-axis and Y-axis positions of the interferometer, reflector, and ball joint bearing based on the guide rail.

7. The industrial robot calibration method based on laser interferometer according to claim 6, characterized in that: In step S2, the method of adjusting the light path is as follows: With the circular hole on the cylindrical shaft as a reference, adjust the Y and Z axis positions of the laser interferometer through the pan-tilt table so that the light it emits passes through the circular hole on the cylindrical shaft and emits, and adjust the Y and Z axis direction angles of the laser interferometer so that the direction of the light is parallel to the moving direction of the reflector; adjust the Z and Y axis positions of the interferometer so that the light passes through the interferometer and returns to the optical gate receiving hole of the laser interferometer; fine-tune the Z and Y axis positions of the reflector and interferometer so that the two light rays overlap and enter the optical gate receiving hole to generate interference, and all the indicator lights of the laser interferometer turn green; adjust the Z and Y axis positions of the ball joint bearing so that the light rays hit the marked point of the ball joint bearing, indicating that the light rays pass through the center of the ball joint bearing. Control the gripper of the industrial robot to grab the end of the ball joint bearing and move it along a circular trajectory. Stop at each measurement point and record data. The laser interferometer measures the radial length of the robot tool coordinate system relative to the measurement reference coordinate system. The two angle encoders measure the azimuth and polar angle of the robot tool coordinate system. The i-th measurement point Spherical coordinates in the measurement reference coordinate system , which is defined as the measurement position of the i-th measurement point.

8. The industrial robot calibration method based on laser interferometer according to claim 7, characterized in that: In step S3, the joint angle corresponding to the i-th measurement point and the set calibration system error are substituted into the error solution model to calculate the solution position of the i-th measurement point , define i The measurement points and i The radial length difference of +1 measurement point is : in, The first one is obtained by using the industrial robot error solution model i The measurement points and i+1 The radial length difference of the measuring points; The error solving model of industrial robots is used to find the first i The position coordinates of the measurement points; The error solving model of industrial robots is used to find the first i+1 The position coordinates of the measurement points; Definition i The measurement points and i+ The radial length difference of one measuring point is : in, The radial length of the i+1th measurement point measured by this calibration device; Set up a weighted fitness function based on position and radial length: in, , The fitness function is a weighted sum of the root mean square of the deviations between the solved positions of all measurement points and the measured positions and the root mean square of the deviations between the solved radial length differences of all adjacent measurement points and the measured radial length differences; According to the accuracy level of the angle encoder and the machining accuracy of the rod, the boundary conditions of the calibration system error vector are set, the algorithm parameters are set, the particle swarm algorithm is initialized, the simulation position data is used to find the appropriate algorithm parameters, and the measured position data is used for step-by-step optimization and solution. It is judged whether the maximum number of iterations is reached or the fitness value meets the set value. If so, the algorithm is terminated and the optimal position is output.

9. The industrial robot calibration method based on laser interferometer according to claim 8, characterized in that: The step S3 comprises: S31, simulation verification, use simulation data to find appropriate algorithm parameters, set a set of calibration system errors, use the error solution model to calculate the solution position of N measurement points as the simulation data of its measurement position, let k 1=1, k 2=0, set the boundary conditions of the calibration system error according to the accuracy level of the angle encoder and the machining accuracy level of the rod, set the algorithm parameters, initialize the particle swarm algorithm, use the simulation data of the measurement position of N measurement points to iteratively solve, and judge whether the maximum number of iterations is reached or the fitness value meets the set value. If the optimal value is consistent with or close to the set calibration system error value, it means that the measurement point data meets the solution requirements and the parameter settings are reasonable; if it does not meet the requirements, adjust the parameters or increase the number of measurement points until the termination conditions are met, so as to find the appropriate number of particles, number of variables, individual acceleration constant, social acceleration constant, inertia weight, maximum speed, and number of iterations. Algorithm parameters; S32, using the algorithm parameters obtained in step S31 to initialize the particle swarm algorithm, k 1=1, k 2=0, use the measured position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position; S33, with the global optimal value of the particle swarm output in step S32 and its corresponding position as a reference, modify the boundary conditions, reduce the search range, adjust the weighting coefficient, use the measurement position data of N measurement points to perform iterative solution, determine whether the maximum number of iterations is reached or the fitness value meets the set value, and output the optimal value of the particle swarm and its corresponding position.

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