A Delta robot position calibration system and method

Abstract

This invention discloses a Delta robot position calibration system and method. The system includes a control device, an elastic element, and a Delta robot, a laser rangefinder, and a pressure sensor electrically connected to the control device. The Delta robot includes a main body and an end effector column. The laser rangefinder is mounted on the side wall of the end effector column. One end of the elastic element is connected to the bottom of the end effector column, and the other end is connected to the pressure sensor. The control device is used to obtain the first calibration coordinates of the calibration point based on the laser rangefinder. The control device is also used to obtain the Delta robot deformation error based on the first calibration coordinates and the pressure sensor, and to correct the first calibration coordinates with the deformation error to obtain the final calibration coordinates of the calibration point. Therefore, this calibration system has high calibration efficiency, eliminates the deformation influence of the Delta robot during contact operations, and has high calibration accuracy.

Description

Technical Field

[0001] This invention relates to the field of surface calibration technology, and more particularly to a Delta robot position calibration system and method. Background Technology

[0002] With the continuous development of digital manufacturing technology, higher-precision 3D models are needed to support computer-aided design and manufacturing. Among these technologies, spatial positioning calibration can transform discrete point data of an object's surface into a continuous spatial positioning model, enabling accurate restoration and reconstruction of the object's shape and surface features, thus meeting the needs of digital manufacturing.

[0003] Currently, most existing spatial positioning calibration methods utilize computer vision technology. This involves processing images of an object's surface to extract its surface features and then using these features to build a calibration model. The most common method is based on visual feature point extraction, followed by camera calibration to calculate camera parameters and the object's surface's 3D coordinates, ultimately constructing a spatial model. In addition, there are methods using optical measurement techniques for spatial positioning calibration. These methods can perform high-precision 3D measurements of the object's surface, obtaining point cloud data, which is then used for surface reconstruction and calibration.

[0004] However, the problem is that the visual feature point-based method is easily affected by factors such as ambient lighting and occlusion, which can lead to inaccurate or missing feature points. For Delta robots, when performing contact operations, their accuracy is affected by the deformation caused by the contact between the machine and the workpiece, and it is difficult to obtain the contact deformation error of Delta robots using optical measurement methods. Summary of the Invention

[0005] This invention provides a Delta robot position calibration system and method to solve the problem in related technologies that it is difficult to obtain the contact deformation error of Delta robots using optical measurement methods.

[0006] To address the aforementioned problems, one embodiment of the present invention proposes a Delta robot position calibration system, comprising: a control device, an elastic element, and a Delta robot, a laser rangefinder, and a pressure sensor, all electrically connected to the control device.

[0007] The Delta robot includes a main body and an end effector column, and the laser rangefinder is mounted on the side wall of the end effector column; one end of the elastic element is connected to the bottom of the end effector column, and the other end is connected to the pressure sensor.

[0008] The control device is used to control the Delta robot to move to a calibration point above the workpiece to be calibrated, obtain the first current coordinates of the Delta robot, and control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector, so as to update the first current coordinates based on the first vertical distance as the first calibration coordinates of the calibration point.

[0009] The control device is also used to control the Delta robot to move to the calibration point according to the first calibration coordinate, and continue to control the Delta robot to move vertically. When the pressure data collected by the pressure sensor reaches the preset pressure data, the second current coordinate of the Delta robot is obtained.

[0010] The control device is further configured to obtain the theoretical second vertical distance of the Delta robot's movement based on the second current coordinates and the first calibration coordinates; and to obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element; to obtain the current deformation error of the Delta robot based on the theoretical second vertical distance and the actual second vertical distance; and to correct the first calibration coordinates with the current deformation error to obtain the final calibration coordinates of the calibration point.

[0011] Optionally, the control device is further configured to interpolate and calculate the final calibration coordinates of the remaining calibration points based on the final calibration coordinates of at least two of the obtained calibration points.

[0012] Optionally, the control device is further configured to simulate and calculate the final calibration coordinates of the non-calibration points of the workpiece to be calibrated based on the final calibration coordinates of all the obtained calibration points.

[0013] Optionally, the control device includes a first controller and a second controller; the Delta robot also includes a drive mechanism;

[0014] The first controller is electrically connected to the drive mechanism, the drive mechanism is electrically connected to the main body, the laser rangefinder is electrically connected to the first controller, the pressure sensor is electrically connected to the second controller, and the first controller and the second controller communicate via serial port.

[0015] The first controller is used to control the drive mechanism to output a first drive signal to drive the main body to move the end effector column; it is also used to control the laser rangefinder to measure the first vertical distance from the surface of the workpiece to be calibrated to the bottom of the end effector column;

[0016] The second controller is used to control the pressure sensor to collect pressure data, and when the pressure sensor has preset pressure data, it generates a stop command and sends it to the first controller;

[0017] The first controller controls the drive mechanism to output a second drive signal based on the stop command, so as to drive the main body to stop the movement of the end effector column.

[0018] To achieve the above objectives, another embodiment of the present invention proposes a Delta robot position calibration method, implemented based on the Delta robot position calibration system described in any embodiment of the present invention. The calibration method includes the following steps:

[0019] Step 1: Control the Delta robot to move above a calibration point of the workpiece to be calibrated, and obtain the first current coordinates of the Delta robot;

[0020] Step 2: Control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector column, and update the first current coordinates based on the first vertical distance as the first calibration coordinates of the calibration point;

[0021] Step 3: Control the Delta robot to move to one of the calibration points using the first calibration coordinates, and continue to control the Delta robot to move vertically;

[0022] Step 4: When the pressure data collected by the pressure sensor reaches the preset pressure data, obtain the second current coordinates of the Delta robot;

[0023] Step 5: Based on the second current coordinates and the first calibration coordinates, obtain the theoretical second vertical distance of the Delta robot's motion;

[0024] Step Six: Obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element;

[0025] Step 7: Based on the theoretical second vertical distance and the actual second vertical distance, obtain the current deformation error of the Delta robot, and correct the first calibration coordinates with the current deformation error to obtain the final calibration coordinates of the calibration point.

[0026] Optionally, after step two, the method further includes:

[0027] Repeat step one and step two to obtain the first calibration coordinates of all calibration points;

[0028] Following step seven, the following is also included:

[0029] Repeat steps three through seven to obtain the final calibration coordinates of at least two calibration points.

[0030] The final calibration coordinates of all calibration points are obtained based on the interpolation method and the final calibration coordinates of at least two calibration points.

[0031] Optionally, before repeatedly executing step one and step two, the method further includes:

[0032] The Delta robot is controlled to move in a first plane, which is parallel to a second plane that carries the workpiece to be calibrated, and the distance between the first plane and the second plane is greater than the height of the workpiece to be calibrated.

[0033] Optionally, after obtaining the final calibration coordinates of all calibration points, the following steps are also included:

[0034] Based on the final calibration coordinates of all calibration points obtained, the final calibration coordinates of the non-calibration points of the workpiece to be calibrated are simulated and calculated.

[0035] Optionally, based on the final calibration coordinates of all obtained calibration points, the simulation calculation of the final calibration coordinates of the non-calibration points of the workpiece to be calibrated includes:

[0036] The final calibration coordinates of the non-calibration points of the workpiece to be calibrated are obtained by training a neural network model using a machine learning algorithm.

[0037] Optionally, based on the final calibration coordinates of all the obtained calibration points, simulating the final calibration coordinates of the non-calibration points of the workpiece to be calibrated further includes:

[0038] Discretize all the calibration points to form a node mesh;

[0039] Construct a surface fitting function z = f(x, y), and establish a weighted sum of squares function J between the coordinates of the calibration point and the final calibration coordinates of the calibration point;

[0040] Calculate the coefficients of the weighted sum of squares function J when it reaches its minimum value, so as to obtain the coefficients of the surface fitting function z = f(x, y);

[0041] Based on the surface fitting function z = f(x, y), the final calibration coordinates of the uncalibrated points of the workpiece to be calibrated are calculated.

[0042] In summary, the Delta robot position calibration system and method proposed in the embodiments of the present invention include: a control device, an elastic element, and a Delta robot, a laser rangefinder, and a pressure sensor electrically connected to the control device; the Delta robot includes a main body and an end effector column, and the laser rangefinder is mounted on the side wall of the end effector column; one end of the elastic element is connected to the bottom of the end effector column, and the other end is connected to the pressure sensor; the control device is used to control the Delta robot to move to a calibration point above the workpiece to be calibrated, obtain the first current coordinates of the Delta robot, and control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector column, so as to update the first vertical distance based on the first vertical distance. The current coordinates serve as the first calibration coordinates of the calibration point. The control device is also used to control the Delta robot to move to the calibration point using the first calibration coordinates, and to continue controlling the Delta robot's vertical movement. When the pressure data collected by the pressure sensor reaches the preset pressure data, the second current coordinates of the Delta robot are obtained. The control device is also used to obtain the theoretical second vertical distance of the Delta robot's movement based on the second current coordinates and the first calibration coordinates; and to obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element; the current deformation error of the Delta robot is obtained based on the theoretical second vertical distance and the actual second vertical distance, and the first calibration coordinates are corrected using the current deformation error to obtain the final calibration coordinates of the calibration point. Thus, the first calibration coordinates can be quickly obtained through the initial calibration of the laser rangefinder, and the first calibration coordinates can be corrected by calibrating individual calibration points using the force sensor to obtain the final calibration coordinates. This calibration system has high calibration efficiency, eliminates the deformation influence of the Delta robot during contact operations, and has high calibration accuracy.

[0043] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a block diagram of the Delta robot position calibration system proposed in an embodiment of the present invention;

[0046] Figure 2This is a schematic diagram of the Delta robot position calibration system proposed in an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the Delta robot position calibration system proposed in one embodiment of the present invention;

[0048] Figure 4 This is a flowchart of the Delta robot position calibration method proposed in an embodiment of the present invention. Detailed Implementation

[0049] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0050] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0051] Figure 1 This is a block diagram of the Delta robot position calibration system proposed in an embodiment of the present invention. Figure 2 This is a schematic diagram of the Delta robot position calibration system proposed in an embodiment of the present invention. Figure 1 and Figure 2As shown, the calibration system includes: an elastic element, a control device 100, and a Delta robot 101, a laser rangefinder 102, and a pressure sensor 103, all electrically connected to the control device 100. The Delta robot 101 includes a main body 1011 and an end effector 1012. The laser rangefinder 102 is mounted on the side wall of the end effector 1012. One end of the elastic element is connected to the bottom of the end effector 1012, and the other end is connected to the pressure sensor 103. The control device 100 controls the Delta robot 101 to move to a calibration point above the workpiece 200 to be calibrated, obtains the first current coordinates of the Delta robot 101, and controls the laser rangefinder 102 to measure the first vertical distance from the calibration point to the bottom of the end effector 1012, so as to base the calibration on the first vertical distance. The control device 100 is further configured to update the first current coordinates as the first calibration coordinates of the calibration point; the control device 100 is also configured to control the Delta robot 101 to move to the calibration point using the first calibration coordinates, and continue to control the Delta robot 101 to move vertically. When the pressure data collected by the pressure sensor 103 reaches the preset pressure data, the control device 100 obtains the second current coordinates of the Delta robot; the control device 100 is also configured to obtain the theoretical second vertical distance of the Delta robot 101 based on the second current coordinates and the first calibration coordinates; and to obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element; the control device 100 is configured to obtain the current deformation error of the Delta robot based on the theoretical second vertical distance and the actual second vertical distance, and to correct the first calibration coordinates with the current deformation error to obtain the final calibration coordinates of the calibration point.

[0052] It should be noted that the control device 100 is used to control the Delta robot 101 to move above the calibration point of the workpiece 200 to be calibrated, where the calibration point is the position where the coordinates of the workpiece 200 to be calibrated need to be determined. Then, the control device 100 acquires the first current coordinates of the Delta robot 101. These first current coordinates can be obtained by inverse kinematics from the pulse data of the drive mechanism of the Delta robot 101. For example, the pulse data of the drive mechanism is (P... 1m ,P 2m ,P 3m The first current coordinate obtained by inverse solution is (x m ,y m ,z m Since the Delta robot 101 is currently above the calibration point of the workpiece 200 to be calibrated, the first vertical distance from the calibration point to the bottom of the end effector 1012 can be measured by the laser rangefinder 102. For example, this first vertical distance is h. m Then the first calibration coordinate of the calibration point is (x m ,y m ,z m -hm ), where m represents the current calibration point.

[0053] In other embodiments, the first current coordinate can also be obtained in the following way: since the control device 100 can control the Delta robot 101 to move above each calibration point of the workpiece 200 to be calibrated, the first current coordinate above the calibration point is the control command input by the user when control starts, and the first current coordinate can be obtained directly.

[0054] For ease of calculation, the first current coordinate (x) can be controlled. m ,y m ,z m ) of z m =h is a fixed value. This allows the Delta robot 101 to move within a horizontal plane with a vertical height of h, using the horizontal plane where the workpiece table is located as a reference. The value of h must be higher than the highest point of the workpiece 200 to be calibrated. Thus, the first vertical distance h is obtained. m Then, the first calibration coordinate of the calibration point is (x m ,y m hh m In this way, during the control of Delta robot 101's movement, only the horizontal parameters need to be adjusted, and the vertical parameters only need to be adjusted once, making the calculation simple and convenient.

[0055] In the above embodiment, the first calibration coordinate is a relative coordinate value relative to the Delta robot 101 coordinate system, that is, a relative coordinate value relative to the initial coordinates of the Delta robot 101. The Delta robot 101 coordinate system can be established with the plane supporting the workpiece 200 to be calibrated as the xy plane, and the direction perpendicular to the xy plane as the z-direction, i.e., the vertical direction. The initial coordinates of the Delta robot 101 can be (0, 0, 0).

[0056] Furthermore, the step length of the Delta robot 101 can be determined according to the actual situation. If the calibration points are dense, the step length is shorter; if the calibration points are sparse, the step length is longer. In addition, the step length can be determined according to the number of calibration points.

[0057] Therefore, the control device 100 can control the Delta robot 101 to move above each calibration point of the workpiece 200 to be calibrated, and obtain the first calibration coordinates of each calibration point in the manner described above. When the control device 100 controls the Delta robot 101 to move above each calibration point of the workpiece 200 to be calibrated, that is, when moving on the horizontal plane, it can follow a pre-planned path, such as a serpentine path or a zigzag path.

[0058] After obtaining the first calibration coordinates, since the Delta robot 101 will have deformation error when it contacts the surface of the workpiece 200 to be calibrated, in order to ensure the accuracy of the calibration and that the calibrated surface can be used for actual operation by the Delta robot 101, it is also necessary to calculate the deformation error that the Delta robot 101 will have when it contacts the surface of the workpiece 200 to be calibrated.

[0059] The process of obtaining deformation error is as follows: The control device 100 controls the Delta robot 101 to move to the first calibration coordinate (e.g., (x...)). m ,y m ,z m -h m Then, the Delta robot 101 continues to move vertically, and when the reading of the pressure sensor 103 reaches the preset pressure data, the Delta robot 101 stops moving. The preset pressure data can be 10N, 15N, etc., and the specific value depends on the force applied to the workpiece to be calibrated by the Delta robot 101 during actual operation.

[0060] At this time, the second current coordinate (x) of the Delta robot 101 is calculated by back-calculating the pulse data of the drive mechanism 1013 of the Delta robot 101, such as the motor. m ',y m ',z m Since the control device 100 directly controls the Delta robot 101 to move to the first calibration coordinate, x m '=x m ,y m '=y m Then, the robot 101 moves a second vertical distance H in the vertical direction. 理 For H 理 =z m -h m -z m The first calibration coordinate can be considered as the coordinate where the Delta robot 101 is in contact with the calibration point of the workpiece 200 to be calibrated, but the pressure data of the pressure sensor 103 is 0. The second vertical distance H... 理 This can be the theoretical second vertical distance. Since the system incorporates an elastic element, which can be a rigid spring with an elastic coefficient of k, the pressure can be determined based on preset pressure data F. th The ratio of the elastic coefficient k to the actual second vertical distance H is obtained. 实 The actual second vertical distance is

[0061] Therefore, the theoretical second vertical distance H can be used to... 理 The actual second vertical distance H实 The difference can be used to obtain the deformation error Δ of Delta robot 101. Finally, this deformation error is used to correct the first calibration coordinate (x...). m ,y m ,z m -h m This allows us to obtain the final calibration coordinates (x, y) corresponding to the calibration point. m ,y m ,z m -h m -Δ).

[0062] Therefore, by using the laser rangefinder 102 and the pressure sensor 103, the inaccuracy of feature point extraction based on visual feature points can be avoided, the influence of deformation error during calibration when the Delta robot 101 makes contact can be eliminated, and the calibration accuracy can be improved.

[0063] In one embodiment, the control device 100 is further configured to interpolate and calculate the final calibration coordinates of the remaining calibration points based on the final calibration coordinates of at least two calibration points.

[0064] Since the calibration of the pressure sensor 103 requires contact with the workpiece 200 to be calibrated, calibrating the deformation of each calibration point using the pressure sensor 103 would be inefficient. The laser rangefinder 102, however, does not require contact with the workpiece 200, resulting in higher calibration efficiency. Therefore, the control device 100 can obtain the first calibration coordinates of all calibration points through the calibration method of the laser rangefinder 102, and then obtain the deformation error of individual calibration points through the calibration method of the pressure sensor 103, ultimately obtaining the final calibration coordinates of these individual points. Interpolation calculations are then performed using these final calibration coordinates to obtain the final coordinates of the remaining calibration points. For example, if the workpiece 200 to be calibrated is rectangular, the final calibration coordinates of the rectangular marker points, such as the four corner points and the center point, can be obtained. Then, using the final calibration coordinates of these marker points, the deformation error of the remaining calibration points is interpolated, thus obtaining the final calibration coordinates of the remaining calibration points of the workpiece 200 to be calibrated.

[0065] In other words, for these marker points, a finite element interpolation function (including first-order, second-order, and even higher-order interpolation functions) can be established to create mesh cells (including planar and three-dimensional) in the robot's workspace. Based on the deformation error information of the aforementioned partial points, the deformation error values ​​of all calibration points in the entire field can be interpolated. Then, the spatial coordinate values ​​of the workpiece surface obtained by the laser rangefinder can be superimposed, thereby achieving accurate calibration of the actual spatial coordinates of all calibration points in the entire field during operation.

[0066] Therefore, by using the laser rangefinder 102 and the pressure sensor 103, the calibration efficiency is satisfied, the influence of deformation when the Delta robot 101 makes contact is eliminated, and the normal operation of the Delta robot 101 is guaranteed, thus improving the calibration accuracy.

[0067] In one embodiment, the control device 100 is further configured to simulate and calculate the final calibration coordinates of the non-calibrated points of the workpiece to be calibrated based on the final calibration coordinates of all the obtained calibration points.

[0068] It should be noted that if the machining surface of the workpiece 200 to be calibrated is a complex curved surface, the final calibration coordinates of the known calibration points mentioned above are used to train a neural network model using a machine learning algorithm. Finally, the trained model is used to predict the calibration and compensation results of the entire machining space.

[0069] If the surface morphology of the machined surface of the workpiece 200 to be calibrated is not very complex, in order to improve the calibration accuracy, the following surface fitting method will be used to calibrate and compensate the spatial points within the machining domain. In this surface fitting method, the machined surface region of the workpiece 200 to be calibrated is discretized into a 40×40 node mesh.

[0070] In the surface fitting region, the fitting function z = f(x,y) is constructed using the moving least squares method:

[0071]

[0072] In the formula, p(x, y) = [p1(x, y), p2(x, y), ..., p i [x,y)] is a basis function, which is a K-order complete polynomial; i is the number of terms in the basis function, m represents the uncalibrated point; x, y, and z are the x, y, and z coordinates of the uncalibrated point, respectively; a(x,y)=[a1(x,y),a2(x,y),...,a i [x,y)] represents the coefficients to be determined. For the problem in this invention, where p(x,y) = [1,x,y] T .

[0073] To establish the optimal model J, the coefficients a(x,y) to be determined need to be adjusted so that the weighted sum of squares between the values ​​of the calibration points near the nodes and the values ​​of the fitted function at the calibration points is minimized.

[0074]

[0075] In the formula, d represents the calibration point, node represents the mesh node, and x node Let x be the x-coordinate of the grid node, and y be the y-coordinate of the grid node. node Let x be the y-coordinate of the grid node, and x be the x-coordinate of the grid node. d ,yd ,z d Let x, y, and z be the coordinates of the calibration point, q be the number of all calibration points, and w(s) be the weighting function.

[0076] in,

[0077]

[0078] After obtaining the optimal model J with parameters a(x,y), to determine the coefficients of a(x,y), we need to take the partial derivative of a(x,y). When J is minimized, we can obtain the fitting function f(x,y) near the nodes. Substituting the partially derived a(x,y) into f(x,y), we obtain the fitting function for the moving surface:

[0079] f(x,y)=p T (x,y)A -1 (x,y)B(x,y)z;

[0080] in,

[0081] B(x)=[w(s1)p(x1,y1),w(s2)p(x2,y2),...,w(s n )p(x n ,y n )];

[0082] z = [z1, z2, ..., z n ];

[0083]

[0084] After obtaining the surface fitting function, use f(x,y)=p T (x,y)A -1 The height value of the mesh node (x,y)B(x,y)z can be obtained, which is the z-coordinate of the mesh node. Based on the formula, the relevant program can be written to fit the entire surface and obtain the point cloud spatial coordinates. Finally, the machining plane of the workpiece is reconstructed based on the point cloud coordinates and then processed.

[0085] In one embodiment, Figure 3 This is a block diagram of a Delta robot position calibration system proposed in another embodiment of the present invention. Figure 3 As shown, the control device 100 includes a first controller 1001 and a second controller 1002; the Delta robot 101 also includes a drive mechanism 1013.

[0086] The first controller 1001 is electrically connected to the drive mechanism 1013, the drive mechanism 1013 is electrically connected to the main body 1011, the laser rangefinder 102 is electrically connected to the first controller 1001, the pressure sensor 103 is electrically connected to the second controller 1002, and the first controller 1001 and the second controller 1002 communicate via serial port.

[0087] The first controller 1001 is used to control the drive mechanism 1013 to output a first drive signal to drive the main body 1011 to move the end effector 1012; it is also used to control the laser rangefinder 102 to measure the first vertical distance from the surface of the workpiece 200 to be calibrated to the bottom of the end effector 1012.

[0088] The second controller 1002 is used to control the pressure sensor 103 to collect pressure data, and when the pressure sensor 103 has preset pressure data, it generates a stop command and sends it to the first controller 1001;

[0089] The first controller 1001 controls the drive mechanism to output a second drive signal based on the stop command, so as to drive the main body 1011 to stop the end effector column 1012 from moving.

[0090] Among them, the drive mechanism 1013 can be three servo motors (such as...) Figure 2 (As shown). Both the first controller 1001 and the second controller 1002 can be STM32 microcontrollers. By separating the control device 100 into two microcontrollers, the computational load of a single controller can be reduced, computational efficiency can be improved, and control accuracy can be enhanced. The Delta robot 101 has three degrees of freedom of motion, and is driven by three servo motors, forming the drive mechanism 1013. The robot's end effector is equipped with a pressure sensor and a laser rangefinder. A spring is installed at the connection between the pressure sensor and the robot's end effector to prevent damage to the mechanism caused by hard contact between the mechanism and the workpiece surface.

[0091] In other embodiments, the first controller 1001 and the second controller 1002 may also communicate wirelessly. This invention does not impose specific limitations on this.

[0092] Figure 4 This is a flowchart of the Delta robot position calibration method proposed in an embodiment of the present invention. This calibration method is implemented based on the Delta robot position calibration system of any embodiment of the present invention, such as... Figure 4 As shown, the calibration method includes the following steps:

[0093] Step 1: Control the Delta robot to move above a calibration point of the workpiece to be calibrated, and obtain the first current coordinates of the Delta robot.

[0094] In this process, the control device 100 controls the Delta robot 101 to move above the calibration point of the workpiece 200 to be calibrated, where the calibration point is the position where the coordinates of the workpiece 200 need to be calibrated. Then, the control device 100 acquires the first current coordinates of the Delta robot 101. These first current coordinates can be obtained by inverse kinematics of the pulse data from the drive mechanism of the Delta robot 101. For example, the pulse data of the drive mechanism is (P... 1m ,P 2m ,P 3m The first current coordinate obtained by inverse solution is (x m ,y m ,z m ).

[0095] In other embodiments, the first current coordinate can also be obtained in the following way: since the control device 100 can control the Delta robot 101 to move above each calibration point of the workpiece 200 to be calibrated, the first current coordinate above the calibration point is the control command input by the user when control begins, and this first current coordinate (x) can be obtained directly. m ,y m ,z m ).

[0096] Optionally, before performing step one, the following may also be included:

[0097] The Delta robot is controlled to move in a first plane, which is parallel to a second plane that carries the workpiece to be calibrated. The distance between the first and second planes is greater than the height of the workpiece to be calibrated.

[0098] For ease of calculation, the first current coordinate (x) can be controlled. m ,y m ,z m ) of z m =h is a fixed value. This allows the Delta robot 101 to move within a horizontal plane with a vertical height of h, using the horizontal plane where the workpiece table is located as a reference. The value of h must be higher than the highest point of the workpiece 200 to be calibrated. Thus, the first vertical distance h is obtained. m Then, the first calibration coordinate of the calibration point is (x m ,y m hh m In this way, during the control of Delta robot 101's movement, only the horizontal parameters need to be adjusted, and the vertical parameters only need to be adjusted once, making the calculation simple and convenient.

[0099] In the above embodiment, the first calibration coordinate is a relative coordinate value relative to the Delta robot 101 coordinate system, that is, a relative coordinate value relative to the initial coordinates of the Delta robot 101. The Delta robot 101 coordinate system can be established with the plane supporting the workpiece 200 to be calibrated as the xy plane, and the direction perpendicular to the xy plane as the z-direction, i.e., the vertical direction. The initial coordinates of the Delta robot 101 can be (0, 0, 0).

[0100] Step 2: Control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector column, and update the first current coordinates based on the first vertical distance as the first calibration coordinates of the calibration point.

[0101] At this point, if the first vertical distance is h m Then the first calibration coordinate of the calibration point is (x m ,y m ,z m -h m ), where m represents the current calibration point.

[0102] Step 3: Control the Delta robot to move to one of the calibration points using the first calibration coordinates, and continue to control the Delta robot's vertical movement.

[0103] Step 4: When the pressure data collected by the pressure sensor reaches the preset pressure data, obtain the second current coordinate of the Delta robot.

[0104] Specifically, the second current coordinate (x) of the Delta robot 101 can be calculated from the pulse data of the drive mechanism 1013 of the Delta robot 101, such as the motor. m ',y m ',z m '),

[0105] Step 5: Obtain the theoretical second vertical distance of the Delta robot motion based on the second current coordinates and the first calibration coordinates.

[0106] Since the control device 100 directly controls the Delta robot 101 to move to the first calibrated coordinate (x) m ,y m ,z m -h m ), and then, x m '=x m ,y m '=y m Then, the robot 101 moves a second vertical distance H in the vertical direction. 理 For H 理 =z m -hm -z m The first calibration coordinate can be considered as the coordinate where the Delta robot 101 is in contact with the calibration point of the workpiece 200 to be calibrated, but the pressure data of the pressure sensor 103 is 0. The second vertical distance H... 理 This can be the theoretical second vertical distance.

[0107] Step 6: Obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element.

[0108] Since the system is equipped with an elastic element, which can be a rigid spring with an elastic coefficient of k, it can be based on preset pressure data F. th The ratio of the elastic coefficient k to the actual second vertical distance H is obtained. 实 The actual second vertical distance is

[0109] Step 7: Based on the theoretical second vertical distance and the actual second vertical distance, obtain the current deformation error of the Delta robot, correct the first calibration coordinates with the current deformation error, and obtain the final calibration coordinates of the calibration point.

[0110] Therefore, the theoretical second vertical distance H can be used to... 理 The actual second vertical distance H 实 The difference can be used to obtain the deformation error Δ of Delta robot 101. Finally, this deformation error is used to correct the first calibration coordinate (x...). m ,y m ,z m -h m This allows us to obtain the final calibration coordinates (x, y) corresponding to the calibration point. m ,y m ,z m -h m -Δ).

[0111] Furthermore, the above method can be used to calibrate each calibration point on the workpiece 200 one by one. By using the laser rangefinder 102 and pressure sensor 103, the inaccuracy of feature point extraction based on visual feature points can be avoided, the influence of deformation caused by the Delta robot 101 during calibration can be eliminated, and the calibration accuracy can be improved.

[0112] Optionally, in one embodiment, after step two, the method further includes:

[0113] Repeat steps one and two to obtain the first calibration coordinates of all calibration points;

[0114] Following step seven, the following is also included:

[0115] Repeat steps three through seven to obtain the final calibration coordinates of at least two calibration points;

[0116] The final calibration coordinates of all calibration points are obtained based on the interpolation method and the final calibration coordinates of at least two calibration points.

[0117] It should be noted that since the calibration of the pressure sensor 103 requires contact with the workpiece 200 to be calibrated, calibrating the deformation of each calibration point using the pressure sensor 103 would be inefficient. The laser rangefinder 102, however, does not require contact with the workpiece 200, resulting in higher calibration efficiency. Therefore, the control device 100 can obtain the first calibration coordinates of all calibration points through the calibration method of the laser rangefinder 102, and then obtain the deformation error of individual calibration points through the calibration method of the pressure sensor 103, ultimately obtaining the final calibration coordinates of these individual points. Interpolation calculations are then performed using these final calibration coordinates to obtain the final coordinates of the remaining calibration points. For example, if the workpiece 200 to be calibrated is rectangular, the final calibration coordinates of the rectangular marker points, such as the four corner points and the center point, can be obtained. Then, using the final calibration coordinates of these marker points, the deformation error of the remaining calibration points is interpolated, thus obtaining the final calibration coordinates of the remaining calibration points of the workpiece 200 to be calibrated.

[0118] Optionally, in this embodiment, before performing step one, the following steps are further included:

[0119] The Delta robot is controlled to move in a first plane, which is parallel to a second plane that carries the workpiece to be calibrated. The distance between the first and second planes is greater than the height of the workpiece to be calibrated.

[0120] For ease of calculation, the first current coordinate (x) can be controlled. m ,y m ,z m ) of z m =h is a fixed value. This allows the Delta robot 101 to move within a horizontal plane with a vertical height of h, using the horizontal plane where the workpiece table is located as a reference. The value of h must be higher than the highest point of the workpiece 200 to be calibrated. Thus, the first vertical distance h is obtained. m Then, the first calibration coordinate of the calibration point is (x m ,y m hh m In this way, during the control of Delta robot 101's movement, only the horizontal parameters need to be adjusted, and the vertical parameters only need to be adjusted once, making the calculation simple and convenient.

[0121] In the above embodiment, the first calibration coordinate is a relative coordinate value relative to the Delta robot 101 coordinate system, that is, a relative coordinate value relative to the initial coordinates of the Delta robot 101. The Delta robot 101 coordinate system can be established with the plane supporting the workpiece 200 to be calibrated as the xy plane, and the direction perpendicular to the xy plane as the z-direction, i.e., the vertical direction. The initial coordinates of the Delta robot 101 can be (0, 0, 0).

[0122] Optionally, after obtaining the final calibration coordinates of all calibration points, the following steps are also included:

[0123] Based on the final calibration coordinates of all calibration points obtained, the final calibration coordinates of the non-calibration points of the workpiece to be calibrated are simulated and calculated.

[0124] Optionally, based on the final calibration coordinates of all obtained calibration points, the simulation calculation of the final calibration coordinates of the non-calibration points of the workpiece to be calibrated includes:

[0125] By training a neural network model using machine learning algorithms, the final calibration coordinates of the non-calibration points of the workpiece to be calibrated are obtained.

[0126] If the machining surface of the workpiece 200 to be calibrated is a complex curved surface, the final calibration coordinates of the known calibration points are used to train a neural network model using a machine learning algorithm. Finally, the trained model is used to predict the calibration and compensation results of the entire machining space.

[0127] Optionally, based on the final calibration coordinates of all the obtained calibration points, the simulation calculation of the final calibration coordinates of the non-calibration points of the workpiece to be calibrated also includes:

[0128] Discretize all calibration points to form a node mesh;

[0129] Construct a surface fitting function z = f(x, y), and establish a weighted sum of squares function J between the coordinates of the surface fitting function z = f(x, y) at the calibration point and the final calibration coordinates of the calibration point;

[0130] Calculate the coefficients of the weighted sum of squares function J when it reaches its minimum value, in order to obtain the coefficients of the surface fitting function z = f(x, y);

[0131] Based on the surface fitting function z=f(x,y), the final calibration coordinates of the non-calibration points of the workpiece to be calibrated are calculated.

[0132] If the surface morphology of the machined surface of the workpiece 200 to be calibrated is not very complex, in order to improve the calibration accuracy, the following surface fitting method will be used to calibrate and compensate the spatial points within the machining domain. In this surface fitting method, the machined surface region of the workpiece 200 to be calibrated is discretized into a 40×40 node mesh.

[0133] In the surface fitting region, the fitting function z = f(x,y) is constructed using the moving least squares method:

[0134]

[0135] In the formula, p(x, y) = [p1(x, y), p2(x, y), ..., p i [x,y)] is a basis function, which is a K-order complete polynomial; i is the number of terms in the basis function, m represents the uncalibrated point; x, y, and z are the x, y, and z coordinates of the uncalibrated point, respectively; a(x,y)=[a1(x,y),a2(x,y),...,a i [x,y)] represents the coefficients to be determined. For the problem in this invention, where p(x,y) = [1,x,y] T .

[0136] To establish the optimal model J, the coefficients a(x,y) to be determined need to be adjusted so that the weighted sum of squares between the values ​​of the calibration points near the nodes and the values ​​of the fitted function at the calibration points is minimized.

[0137]

[0138] In the formula, d represents the calibration point, node represents the mesh node, and x node Let x be the x-coordinate of the grid node, and y be the y-coordinate of the grid node. node Let x be the y-coordinate of the grid node, and x be the x-coordinate of the grid node. d ,y d ,z d Let x, y, and z be the coordinates of the calibration point, q be the number of all calibration points, and w(s) be the weighting function.

[0139] in,

[0140] After obtaining the optimal model J with parameters a(x,y), to determine the coefficients of a(x,y), we need to take the partial derivative of a(x,y). When J is minimized, we can obtain the fitting function f(x,y) near the nodes. Substituting the partially derived a(x,y) into f(x,y), we obtain the fitting function for the moving surface:

[0141] f(x,y)=p T (x,y)A -1 (x,y)B(x,y)z;

[0142] in,

[0143] B(x)=[w(s1)p(x1,y1),w(s2)p(x2,y2),...,w(s n)p(x n ,y n )];

[0144] z = [z1, z2, ..., z n ];

[0145]

[0146] After obtaining the surface fitting function, use f(x,y)=p T (x,y)A -1 The height value of the mesh node (x,y)B(x,y)z can be obtained, which is the z-coordinate of the mesh node. Based on the formula, the relevant program can be written to fit the entire surface and obtain the point cloud spatial coordinates. Finally, the machining plane of the workpiece is reconstructed based on the point cloud coordinates and then processed.

[0147] Therefore, by combining a laser rangefinder and a pressure sensor to calibrate and reconstruct the workpiece model, the positioning accuracy and calibration efficiency of the robot can be significantly improved. This calibration method addresses the deformation error of the Delta robot when it comes into contact with the workpiece during operation, thereby improving its machining accuracy on the workpiece surface. Furthermore, this technology only requires contact calibration at a few key points, thus overcoming the problem of low efficiency associated with calibration relying solely on contact sensors.

[0148] In summary, the Delta robot position calibration system and method proposed in the embodiments of the present invention include: a control device, an elastic element, and a Delta robot, a laser rangefinder, and a pressure sensor electrically connected to the control device; the Delta robot includes a main body and an end effector column, and the laser rangefinder is mounted on the side wall of the end effector column; one end of the elastic element is connected to the bottom of the end effector column, and the other end is connected to the pressure sensor; the control device is used to control the Delta robot to move to a calibration point above the workpiece to be calibrated, obtain the first current coordinates of the Delta robot, and control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector column, so as to update the first vertical distance based on the first vertical distance. The current coordinates serve as the first calibration coordinates of the calibration point. The control device is also used to control the Delta robot to move to the calibration point using the first calibration coordinates, and to continue controlling the Delta robot's vertical movement. When the pressure data collected by the pressure sensor reaches the preset pressure data, the second current coordinates of the Delta robot are obtained. The control device is also used to obtain the theoretical second vertical distance of the Delta robot's movement based on the second current coordinates and the first calibration coordinates; and to obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element; the current deformation error of the Delta robot is obtained based on the theoretical second vertical distance and the actual second vertical distance, and the first calibration coordinates are corrected using the current deformation error to obtain the final calibration coordinates of the calibration point. Thus, the first calibration coordinates can be quickly obtained through the initial calibration of the laser rangefinder, and the first calibration coordinates can be corrected by calibrating individual calibration points using the force sensor to obtain the final calibration position. This calibration system has high calibration efficiency, eliminates the deformation influence of the Delta robot during contact operations, and has high calibration accuracy.

[0149] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0150] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A Delta robot position calibration system, characterized in that, include: Control device, elastic element, and Delta robot, laser rangefinder, and pressure sensor electrically connected to the control device respectively; The Delta robot includes a main body and an end effector column, and the laser rangefinder is mounted on the side wall of the end effector column; one end of the elastic element is connected to the bottom of the end effector column, and the other end is connected to the pressure sensor. The control device is used to control the Delta robot to move above a calibration point of the workpiece to be calibrated, and to obtain the first current coordinate (x) of the Delta robot. m ,y m ,z m The system controls the laser rangefinder to measure the first vertical distance h from the calibration point to the bottom of the end effector column. m Based on the first vertical distance h m Update the first current coordinate (x) m ,y m ,z m ) as the first calibration coordinate (x) of the calibration point m ,y m ,z m -h m ); The control device is also used to position the first calibration coordinates (x) m ,y m ,z m -h m The Delta robot is controlled to move to the calibration point, and its vertical movement is further controlled. When the pressure data collected by the pressure sensor reaches the preset pressure data, the second current coordinate (x, y) of the Delta robot is obtained. m ',y m ',z m '); The control device is also configured to base on the second current coordinate (x) m ',y m ',z m ') and the first calibration coordinate (x) m ,y m ,z m -h m Obtain the theoretical second vertical distance H of the Delta robot motion. 理 ; and is used to obtain the actual second vertical distance H based on the preset pressure data and the elastic coefficient of the elastic element. 实 Based on the aforementioned theory, the second vertical distance H 理 and the actual second vertical distance H 实 The current deformation error Δ of the Delta robot is obtained, and the first calibration coordinate (x) is corrected using the current deformation error Δ. m ,y m ,z m -h m ), thus obtaining the final calibration coordinates (x, y) of the calibration point. m ,y m ,z m -h m -Δ).

2. The Delta robot position calibration system according to claim 1, characterized in that, The control device is also used to interpolate and calculate the final calibration coordinates of the remaining calibration points based on the final calibration coordinates of at least two of the calibration points.

3. The Delta robot position calibration system according to claim 1, characterized in that, The control device is also used to simulate and calculate the final calibration coordinates of the non-calibration points of the workpiece to be calibrated based on the final calibration coordinates of all the calibration points obtained.

4. The Delta robot position calibration system according to claim 1, characterized in that, The control device includes a first controller and a second controller; the Delta robot also includes a drive mechanism. The first controller is electrically connected to the drive mechanism, the drive mechanism is electrically connected to the main body, the laser rangefinder is electrically connected to the first controller, the pressure sensor is electrically connected to the second controller, and the first controller and the second controller communicate via serial port. The first controller is used to control the drive mechanism to output a first drive signal to drive the main body to move the end effector column; it is also used to control the laser rangefinder to measure the first vertical distance from the surface of the workpiece to be calibrated to the bottom of the end effector column; The second controller is used to control the pressure sensor to collect pressure data, and when the pressure sensor has preset pressure data, it generates a stop command and sends it to the first controller; The first controller controls the drive mechanism to output a second drive signal based on the stop command, so as to drive the main body to stop the movement of the end effector column.

5. A Delta robot position calibration method, characterized in that, Based on the Delta robot position calibration system as described in any one of claims 1-4, the calibration method includes the following steps: Step 1: Control the Delta robot to move above a calibration point of the workpiece to be calibrated, and obtain the first current coordinates of the Delta robot; Step 2: Control the laser rangefinder to measure the first vertical distance from the calibration point to the bottom of the end effector column, and update the first current coordinates based on the first vertical distance as the first calibration coordinates of the calibration point; Step 3: Control the Delta robot to move to one of the calibration points using the first calibration coordinates, and continue to control the Delta robot to move vertically; Step 4: When the pressure data collected by the pressure sensor reaches the preset pressure data, obtain the second current coordinates of the Delta robot; Step 5: Based on the second current coordinates and the first calibration coordinates, obtain the theoretical second vertical distance of the Delta robot's motion; Step Six: Obtain the actual second vertical distance based on the preset pressure data and the elastic coefficient of the elastic element; Step 7: Based on the theoretical second vertical distance and the actual second vertical distance, obtain the current deformation error of the Delta robot, and correct the first calibration coordinates with the current deformation error to obtain the final calibration coordinates of the calibration point.

6. The Delta robot position calibration method according to claim 5, characterized in that, Following step two, the following is also included: Repeat step one and step two to obtain the first calibration coordinates of all calibration points; Following step seven, the following is also included: Repeat steps three through seven to obtain the final calibration coordinates of at least two calibration points. The final calibration coordinates of all calibration points are obtained based on the interpolation method and the final calibration coordinates of at least two calibration points.

7. The Delta robot position calibration method according to claim 5, characterized in that, Before performing step one, the procedure also includes: The Delta robot is controlled to move in a first plane, which is parallel to a second plane that carries the workpiece to be calibrated, and the distance between the first plane and the second plane is greater than the height of the workpiece to be calibrated.

8. The Delta robot position calibration method according to claim 5, characterized in that, After obtaining the final calibration coordinates of all calibration points, the following is also included: Based on the final calibration coordinates of all calibration points obtained, the final calibration coordinates of the non-calibration points of the workpiece to be calibrated are simulated and calculated.

9. The Delta robot position calibration method according to claim 8, characterized in that, Based on the final calibration coordinates of all calibration points obtained, the simulation calculation of the final calibration coordinates of the non-calibration points of the workpiece to be calibrated includes: The final calibration coordinates of the non-calibration points of the workpiece to be calibrated are obtained by training a neural network model using a machine learning algorithm.

10. The Delta robot position calibration method according to claim 8, characterized in that, Based on the final calibration coordinates of all the obtained calibration points, the simulation calculation of the final calibration coordinates of the non-calibration points of the workpiece to be calibrated also includes: Discretize all the calibration points to form a node mesh; Construct a surface fitting function z = f(x, y), and establish a weighted sum of squares function J between the coordinates of the calibration point and the final calibration coordinates of the calibration point; Calculate the coefficients of the weighted sum of squares function J when it reaches its minimum value, so as to obtain the coefficients of the surface fitting function z = f(x, y); Based on the surface fitting function z = f(x, y), the final calibration coordinates of the uncalibrated points of the workpiece to be calibrated are calculated.

Images