Stay wire measuring device, stay wire outlet point position determination method and robot distance error calibration method

Abstract

The invention discloses a stay wire measuring device, a stay wire outlet point position determination method and a robot distance error calibration method, and belongs to the technical field of robot calibration. The stay wire measuring device can convert a stay wire from a horizontal state to a vertically downward state, and enables the stay wire to bypass a pulley installed on the base through a rotatable lead stepped shaft connected with the base, thereby achieving the precise measurement of any point position in a three-dimensional space, and remarkably improving the flexibility and precision of the measurement. Furthermore, through the method for determining the position of the wire outlet point of the stay wire and the method for calibrating the distance error of the robot, the position of the wire outlet point can be accurately measured, the difference between an actual wire outlet path and an ideal path is compensated by accurately measuring the position of the wire outlet point, and the measurement accuracy of the stay wire measurement device is further improved.

Description

Technical Field

[0001] The invention relates to a wire drawing measuring device, a method for determining the position of a wire drawing outlet point and a robot distance error calibration method, and belongs to the technical field of robot calibration. Background Art

[0002] With the continuous advancement of automation technology, especially the rapid expansion of the robotics field, the manufacturing industry is gradually changing from a production method that relies on manual assistance to fully automated unmanned production. The acceleration of this technological change has promoted the widespread application of new robotics technology in the fields of industry and scientific research. In this process, robot calibration technology, as a key step to ensure the accuracy of robot operation, has received great attention from scientific research institutions.

[0003] In order to solve the problems of high cost and complex operation of measuring equipment in existing calibration technology, wire-drawing sensors are widely used as an effective optimization solution. However, the current wire-drawing sensor technology has limitations, mainly in that it can only measure along a single fixed axis, which limits its ability to perform accurate measurements in three-dimensional space. At the same time, existing wire-drawing measurement devices usually use the horizontal tangent point of the guide pulley as the measurement reference, ignoring the position offset of the wire-out point when the robot's measurement position changes. This offset causes the actual measurement path to be not a completely straight line, but a combination of arcs and straight lines, thereby introducing measurement errors. Summary of the invention

[0004] The present invention provides a wire-pulling measuring device, which can transform the wire from a horizontal state to a vertical downward state, and through a rotatable wire ladder shaft connected to a base, the wire is passed around a pulley installed on the base, thereby realizing accurate measurement of any point in three-dimensional space, significantly improving the flexibility and accuracy of measurement. Furthermore, a method for determining the position of a wire outlet point and a robot distance error calibration method are provided, which compensates for the difference between the actual wire-pulling path and the ideal path by accurately measuring the position of the outlet point, further improving the measurement accuracy of the wire-pulling measuring device.

[0005] The technical solution of the present invention is:

[0006] According to a first aspect of the present invention, a wire pulling measurement device is provided, comprising a wire pulling sensor 1, a wire pulling guide mechanism 3, and a multi-axis force sensor 4; the wire pulling guide mechanism 3 is connected to the wire pulling sensor 1, and the multi-axis force sensor 4 is connected to the wire pulling guide mechanism 3.

[0007] Furthermore, the wire pulling guide mechanism 3 includes an online guiding mechanism, a wire guiding mechanism, and an offline guiding mechanism; the online guiding mechanism is connected to the offline guiding mechanism through the wire guiding mechanism; the online guiding mechanism is used to lead the wire on the wire pulling sensor 1 to the wire guiding mechanism, and the wire guiding mechanism is used to guide the wire led out by the online guiding mechanism to the offline guiding mechanism, and the offline guiding mechanism is used to lead out the wire guided by the wire guiding mechanism.

[0008] Furthermore, the online guiding mechanism includes a first upper base 11, a second upper base 12, a first pulley 8-1, and a first shaft 10-1; the second upper base 12 and the first upper base 11 are respectively fixed inside the wire sensor 1, and the two ends of the first shaft 10-1 are respectively interference fit with the mounting holes on the second upper base 12 and the first upper base 11, and the first pulley 8-1 is installed on the first shaft 10-1. The wire on the wire sensor 1 is guided to the first entry point of the first pulley 8-1 through the guide column, and then led out to the wire guiding mechanism through the first exit point of the first pulley 8-1.

[0009] Furthermore, the wire guiding mechanism includes a wire stepped shaft 13, a self-aligning ball bearing 15, and a thrust ring 14. The wire stepped shaft 13 is interference fit with the inner ring of the self-aligning ball bearing 15. The thrust ring 14 is arranged above the self-aligning ball bearing 15. The self-aligning ball bearing 15 is clamped by the thrust ring 14 and the shoulder of the wire stepped shaft 13. The outer ring of the self-aligning ball bearing 15 is interference fit with the lower shell 6. The wire guiding mechanism guides the pull wire led out from the first outlet point of the first pulley 8-1 in the upper warp guide mechanism to the second entry point of the second pulley 8-2 in the offline guide mechanism.

[0010] Furthermore, the offline guiding mechanism includes a first lower base 16, a second lower base 17, a second pulley 8-2, and a second shaft 10-2; the first lower base 16 is connected to the second lower base 17 and clamps the wire stepped shaft 13 in the wire guiding mechanism, one end of the second shaft 10-2 is interference fit with the mounting hole on the first lower base 16, the other end of the second shaft 10-2 is clearance fit with the mounting hole on the second lower base 17 and the other end extends from the hole to cooperate with the multi-axis force sensor 4, the second shaft 10-2 is fixedly installed on the first lower base 16 and the second lower base 17, and the second pulley 8-2 is installed on the second shaft 10-2; the wire guide mechanism is guided to the second wire entry point of the second pulley 8-2 by the offline guiding mechanism, and the wire is led out from the reference point / second wire exit point of the second pulley 8-2.

[0011] According to a second aspect of the present invention, a method for determining the position of a wire outlet point in a wire measuring device is provided, comprising the following steps:

[0012] Step 1: Place the wire-pulling measuring device and the target object to be calibrated on the same workbench plane, and pull the wire in the wire-pulling measuring device from the reference point of the wire-pulling measuring device to a predetermined length L1 in a direction parallel to the workbench plane; then subtract the length L2 measured by the wire-pulling sensor 1 from the length L1, and use the value obtained after the subtraction as the distance from the reference point of the wire-pulling measuring device to the initial position of the wire-pulling sensor 1, which is called the reference distance; establish a measurement coordinate system on the reference point of the wire-pulling measuring device, record the force direction of the multi-axis force sensor 4 corresponding to the length L1 when the wire in the wire-pulling measuring device is pulled out, and determine the contact point between the wire pulled from the first pulley 8-1 and the second pulley 8-2 according to the reference point of the wire-pulling measuring device and the force direction of the multi-axis force sensor 4, and the contact point is referred to as the second entry point;

[0013] Step 2: Connect the end of the wire of the wire measuring device to the end of the target object to be calibrated;

[0014] Step 3: Control the target object to be calibrated to move to multiple teaching points in sequence, obtain the positions of multiple teaching points and joint parameter information of the target object to be calibrated, obtain the rope length between the reference point of the wire measurement device and the multiple teaching points, and the force direction corresponding to the multi-axis force sensor 4;

[0015] Step 4: Determine multiple second line-out point positions according to the multiple force directions obtained in step S3 and the second line-in point positions determined in step 1.

[0016] According to a third aspect of the present invention, a robot distance error calibration method is provided, where the object to be calibrated is a robot, and the specific steps of the method are as follows:

[0017] Step 1: When the object to be calibrated is a robot, a plurality of second wire-out point positions corresponding to when the robot to be calibrated moves to a plurality of teaching points in sequence are determined according to a method for determining the wire-out point positions in a wire-drawing measuring device;

[0018] Step 2: According to the multiple teaching point positions, multiple rope lengths and multiple second line-out point positions of the robot to be calibrated, the distance from the multiple teaching point positions of the robot to the reference point is determined, referred to as the actual distance;

[0019] Step 3: According to the joint parameter information displayed by the teaching pendant of the robot to be calibrated, the homogeneous transformation matrix equation from the robot end coordinate system to the robot base coordinate system is established, and the nominal position from the robot end coordinate system to the robot base coordinate system is calculated, referred to as the nominal position;

[0020] Step 4: Calculate the nominal position of the reference point in the robot base coordinate system according to the nominal position and the actual distance, referred to as the nominal reference point position;

[0021] Step 5: Calculate the distance from the nominal position of the robot end to the nominal reference point position according to the nominal reference point position and the nominal position, referred to as the nominal distance;

[0022] Step 6: Subtract the nominal distance from the actual distance to obtain the distance error of the robot end relative to the reference point, referred to as the distance error;

[0023] Step 7: According to the nominal distance, nominal position and the robot joint parameter information to be calibrated, the relationship between the distance error and the robot parameter error is established, which is referred to as the distance error model; the distance error is brought into the distance error model, and the error of the robot joint parameters can be obtained through the least squares method.

[0024] The beneficial effects of the present invention are:

[0025] (1) With regard to the problem of accurately measuring any point in three-dimensional space, existing wire-drawing sensor technologies have obvious limitations, mainly manifested in that they can only measure along a single fixed axis, which limits their ability to accurately measure any position in three-dimensional space. The present invention adopts a solution that effectively overcomes this problem by introducing a wire-drawing guide mechanism. The mechanism first transforms the wire from a horizontal posture to a vertical downward posture, and then passes the wire around a pulley mounted on the lower base through a rotatable wire step shaft connected to the lower base. This design enables the present invention to achieve accurate measurement of any point in three-dimensional space, greatly improving the flexibility and accuracy of measurement.

[0026] (2) The online guide mechanism is installed inside the wire-pulling measuring device, which improves the compactness of the entire measuring mechanism. When carrying or using, since the online guide mechanism is inside the wire-pulling measuring device, damage to the device caused by accidental touch can be well avoided. The entire calibration tooling has a simple structure, is portable and practical, easy to operate, low cost, and strong versatility. It is suitable for robot calibration in different occasions and has high market application value.

[0027] (3) The rotation of the wire-drawing measuring device converts sliding into rolling through the bearing, thereby improving the accuracy of the wire-drawing measuring device in measuring any point in space.

[0028] (4) In order to solve the problem of measuring the wire exit point of the pulley, the existing wire pulling measurement device usually uses the horizontal tangent point of the guide pulley as the reference, ignoring the position offset of the wire exit point caused by the change of the robot's measurement position, resulting in the actual path not being a completely straight line, but a combination of arcs and straight lines, which leads to the problem of insufficient accuracy, especially in long-distance measurement. The present invention provides a robot calibration method, which accurately measures the distance between the end of the robot and the reference point by introducing a wire pulling sensor and a multi-axis force sensor, thereby improving the calibration accuracy. Compared with the prior art, the calibration method of the present invention reduces measurement errors, improves the operating accuracy of the robot, and makes the operation process simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the wire drawing measuring device of the present invention;

[0030] Figure 2 It is an exploded schematic diagram of the wire-drawing measuring device of the present invention;

[0031] Figure 3 This is a schematic diagram of the upper housing of the wire drawing measuring device of the present invention;

[0032] Figure 4 This is a schematic diagram of the lower housing of the wire-drawing measuring device of the present invention;

[0033] Figure 5 It is a schematic diagram of the wire guide of the wire measuring device of the present invention;

[0034] Figure 6 This is a schematic diagram of the component numbers of the guide mechanism of the wire drawing measuring device of the present invention;

[0035] Figure 7 A schematic flow chart of the calibration method of the present invention;

[0036] Figure 8 Determine the schematic diagram of the geometric relationship between the reference point and the entry point;

[0037] Fig. 9 Determine the geometric relationship diagram of the outlet points;

[0038] The numbers in the figure are: wire pull sensor 1, wire pull housing 2, wire pull guide mechanism 3, multi-axis force sensor 4, upper housing 5, lower housing 6, first deep groove ball bearing 7-1, first pulley 8-1, first bushing 9-1, first shaft 10-1, second deep groove ball bearing 7-2, second pulley 8-2, second bushing 9-2, second shaft 10-2, first upper base 11, second upper base 12, wire stepped shaft 13, thrust ring 14, self-aligning ball bearing 15, first lower base 16, second lower base 17. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0040] Example 1: Figure 1-6 As shown, according to the first aspect of an embodiment of the present invention, a wire pulling measurement device is provided, including a wire pulling sensor 1, a wire pulling guide mechanism 3, and a multi-axis force sensor 4; the wire pulling guide mechanism 3 is connected to the wire pulling sensor 1, and the multi-axis force sensor 4 is connected to the wire pulling guide mechanism 3.

[0041] Furthermore, if Figure 1 , 2 As shown, the wire-drawing measuring device further comprises a wire-drawing housing 2, and the wire-drawing housing 2 comprises an upper housing 5 and a lower housing 6. The upper housing 5 is used to open / close on the lower housing 6, and the two are connected in a detachable manner such as by bolts.

[0042] Furthermore, the wire pulling guide mechanism 3 includes an online guiding mechanism, a wire guiding mechanism, and an offline guiding mechanism, and the online guiding mechanism is connected to the offline guiding mechanism through the wire guiding mechanism; the online guiding mechanism is used to lead the wire on the wire pulling sensor 1 to the wire guiding mechanism, and the wire guiding mechanism is used to guide the wire led out by the online guiding mechanism to the offline guiding mechanism, and the offline guiding mechanism is used to lead out the wire guided by the wire guiding mechanism.

[0043] Furthermore, if Figure 6 As shown, the online guiding mechanism includes a first upper base 11, a second upper base 12, a first pulley 8-1, a first deep groove ball bearing 7-1, a first shaft 10-1, and a first sleeve 9-1; the second upper base 12 and the first upper base 11 are respectively connected to the inside of the wire sensor 1 by two screws, and the two ends of the first shaft 10-1 are respectively interference fit with the mounting holes on the second upper base 12 and the first upper base 11, the inner ring of the first deep groove ball bearing 7-1 is interference fit with the first shaft 10-1, and the outer ring of the first deep groove ball bearing 7-1 is interference fit with the first pulley 8-1, and the first sleeve 9-1 with a clearance fit installed on the first shaft 10-1 is used to axially limit the first deep groove ball bearing 7-1 installed between the two first sleeves; the wire on the wire sensor 1 is guided to the first entry point of the first pulley 8-1 through the guide column, and then led out to the wire guiding mechanism through the first exit point of the first pulley 8-1.

[0044] Furthermore, if Figure 6As shown, the wire guiding mechanism includes a wire stepped shaft 13, a self-aligning ball bearing 15, and a thrust ring 14. The wire stepped shaft 13 is interference fit with the inner ring of the self-aligning ball bearing 15. The thrust ring 14 is arranged above the self-aligning ball bearing 15. The self-aligning ball bearing 15 is clamped by the thrust ring 14 and the shoulder of the wire stepped shaft 13. The outer ring of the self-aligning ball bearing 15 is interference fit with the lower housing 6. The wire guiding mechanism guides the wire drawn out from the first outlet point of the first pulley 8-1 to the second inlet point of the second pulley 8-2 in the offline guiding mechanism.

[0045] Furthermore, if Figure 6 As shown, the offline guiding mechanism includes a first lower base 16, a second lower base 17, a second pulley 8-2, a second deep groove ball bearing 7-2, a second shaft 10-2, and a second sleeve 9-2. The first lower base 16 and the second lower base 17 are connected by 3 bolts and the wire step shaft 13 in the wire guiding mechanism is clamped by 8 clamping screws. One end of the second shaft 10-2 is interference fit with the mounting hole on the first lower base 16, and the other end of the second shaft 10-2 is clearance fit with the mounting hole on the second lower base 17 and the other end extends from the hole to cooperate with the multi-axis force sensor 4 (that is, the multi-axis force sensor can be clamped by 4 screws). The nail is installed on one side of the second lower base 17), the second shaft 10-2 is fixedly installed on the first lower base 16 and the second lower base 17, the inner ring of the second deep groove ball bearing 7-2 is interference fit with the second shaft 10-2, the outer ring of the second deep groove ball bearing 7-2 is interference fit with the second pulley 8-2, and the second shaft 10-2 is installed with a clearance fit. The second sleeve 9-2 is used to axially limit the second deep groove ball bearing 7-2 installed between the two second sleeves; the wire guide mechanism guides the wire to the second entry point of the second pulley 8-2 through the offline guide mechanism, and the wire is led out from the reference point / second exit point of the second pulley 8-2.

[0046] like Figure 1-9 As shown, according to a second aspect of an embodiment of the present invention, a method for determining a position of a wire outlet point in a wire measuring device is provided, comprising the following steps:

[0047] Step 1: Place the wire-pulling measuring device and the target object to be calibrated on the same workbench plane, and pull the wire in the wire-pulling measuring device from the reference point of the wire-pulling measuring device in a direction parallel to the workbench plane to a predetermined length L1, for example, to pull out a length of 500 mm; then subtract the length L2 measured by the wire-pulling sensor 1 from the length L1, and use the value obtained after the subtraction as the distance from the reference point of the wire-pulling measuring device to the initial position of the wire-pulling sensor 1, which is called the reference distance; establish a measurement coordinate system on the reference point of the wire-pulling measuring device, record the force direction of the multi-axis force sensor 4 corresponding to the length L1 when the wire in the wire-pulling measuring device is pulled out, and determine the contact point between the wire pulled from the first pulley 8-1 and the second pulley 8-2 according to the reference point of the wire-pulling measuring device and the force direction of the multi-axis force sensor 4, and the contact point is referred to as the second entry point;

[0048] The equation for determining the second line-in point in step 1 is specifically:

[0049]

[0050] Among them, P is the second entry point, D is the force direction when a predetermined length of wire is pulled out in a plane parallel direction on the wire pulling measuring device, passing through the intersection of the center of the second pulley and the second pulley, and G is the reference point.

[0051] Its geometric relationship is as follows Figure 8 As shown, through Figure 8 It can be known that the reference point is G, F is the force direction of the multi-axis force sensor 4, the intersection of the force direction and the cable is D, and the distances between DG and PD are equal, thereby determining the position of P, which is the second entry point; it should be noted that the reference point is the point where the end of the cable in the cable measuring device contacts the second pulley 8-2 in the initial state;

[0052] Step 2: Connect the end of the wire of the wire measuring device to the end of the target object to be calibrated;

[0053] Step 3: Control the target object to be calibrated to move to multiple teaching points in sequence, obtain the positions of multiple teaching points and joint parameter information of the target object to be calibrated, obtain the rope length between the reference point of the wire measurement device and the multiple teaching points, and the force direction corresponding to the multi-axis force sensor 4;

[0054] Step 4: Determine multiple second line-out point positions according to the multiple force directions obtained in step S3 and the second line-in point positions determined in step 1.

[0055] The equation for determining the position of the second outlet point in step 4 is specifically:

[0056]

[0057] Among them, P is the second entry point, D′ is the intersection of the force direction of the second pulley 8-2 passing through the center of the second pulley and the second pulley when the wire-pulling measuring device moves to the teaching point, and G′ is the second exit point.

[0058] Its geometric relationship is as follows Fig. 9 As shown, taking the teaching point at N as an example, through Fig. 9 It can be seen that the position of the second entry point is P, F is the force direction of the multi-axis force sensor 4, that is, the force direction of the second pulley 8-2, the intersection of the force direction and the pull line is D', and the distances between PD' and D'G' are equal. Therefore, it is determined that the position of the second exit point corresponding to the teaching point N is G'.

[0059] like Figure 1-9 As shown, according to a third aspect of an embodiment of the present invention, a robot distance error calibration method is provided, where the object to be calibrated is a robot, and the specific steps of the method are as follows:

[0060] Step 1: When the object to be calibrated is a robot, a plurality of second wire-out point positions corresponding to when the robot to be calibrated moves to a plurality of teaching points in sequence are determined according to a method for determining the wire-out point positions in a wire-drawing measuring device;

[0061] Step 2: According to the multiple teaching point positions, multiple rope lengths and multiple second line-out point positions of the robot to be calibrated, the distance from the multiple teaching point positions of the robot to the reference point is determined, referred to as the actual distance;

[0062] The equation for determining the actual distance in Step 2 is specifically:

[0063]

[0064] Among them, S is the rope length from the reference point to the teaching point, is the arc length from the reference point to the second outlet point, R is the radius of the second pulley 8-2, and β is the arc segment The arc, l m is the actual distance;

[0065] Depend on and the radius R of the second pulley 8-2, we get The radian α is given by and the radius R of the second pulley 8-2, we get The radian is α′, so, The radian β is: β=α′-α.

[0066] The rope length from the reference point to the teaching point is specifically obtained by subtracting the reading of the wire sensor 1 when the wire is pulled to the teaching point by the wire measuring device from the reference distance.

[0067] Step 3: According to the joint parameter information displayed by the teaching pendant of the robot to be calibrated, the homogeneous transformation matrix equation from the robot end coordinate system to the robot base coordinate system is established, and the nominal position from the robot end coordinate system to the robot base coordinate system is calculated, referred to as the nominal position;

[0068] Taking a six-degree-of-freedom robot as an example, the homogeneous change matrix in step 6 is specifically:

[0069]

[0070] in, Represents the coordinate transformation matrix from the i-1th joint to the i-th joint; Specifically:

[0071]

[0072] Where Sθ i = sinθ i , Cθ i = cosθ i , Sα i-1 = sinα i-1 , Cα i-1 =cosα i-1 , (i=1, 2, ..., N) is the joint number, a i-1 is the length of the i-1th joint link, α i-1 is the torsion angle of the i-1th joint link, d i is the offset of the i-1th joint link, θ i is the i-1th joint rotation.

[0073] Step 4: Calculate the nominal position of the reference point in the robot base coordinate system according to the nominal position and the actual distance, referred to as the nominal reference point position; It should be noted that the nominal position of the reference point in the robot base coordinate system is calculated according to the nominal position and the actual distance, referred to as the nominal reference point position, specifically: obtain the A matrix according to the nominal position, and obtain the b matrix according to the nominal position and the actual distance; obtain the nominal position of the reference point in the robot base coordinate system by the least squares method according to the A matrix and the b matrix;

[0074] Step 5: According to the nominal reference point position and the nominal position, the distance from the nominal position of the robot end to the nominal reference point position is calculated, referred to as the nominal distance; specifically: according to the nominal reference point position and the nominal position, the nominal distance is obtained by calculating the Euclidean distance;

[0075] Step 6: Subtract the nominal distance from the actual distance to obtain the distance error of the robot end relative to the reference point, referred to as the distance error;

[0076] Step 7: According to the nominal distance, nominal position and the robot joint parameter information to be calibrated, the relationship between the distance error and the robot parameter error is established, which is referred to as the distance error model; the distance error is brought into the distance error model, and the error of the robot joint parameters can be obtained through the least squares method.

[0077] The distance error model in Step 7 is specifically:

[0078]

[0079] Where Δl is the distance error, P t is the nominal position, P base is the nominal reference point position, l t is the nominal distance, ΔX is the robot joint parameter error, j represents the jth teaching point; J is the Jacobian matrix, and its specific expression is:

[0080]

[0081] Among them, a i-1 is the length of the i-1th joint link, α i-1 is the torsion angle of the i-1th joint link, d i is the offset of the i-1th joint link, θ i is the i-1th joint rotation angle, (i=1,2,…,N) is the joint number.

[0082] Example 2: Taking the robot to be calibrated as an EFORT industrial robot as an example, the following is a description of the optional specific implementation methods of the present invention in combination with specific simulations:

[0083] Step 1: Place the wire-pulling measuring device designed in the present invention and the robot to be calibrated on the same workbench plane, and pull the wire in the wire-pulling measuring device from the reference point of the wire-pulling measuring device to a length of 500mm in a direction parallel to the workbench plane; when the wire of the wire-pulling measuring device is pulled out by 500mm, subtract the length L2 measured by the wire sensor 1 from 500mm, and use the value obtained after the subtraction as the distance from the reference point of the wire-pulling measuring device to the initial position of the wire sensor 1, which is called the reference distance; establish a measurement coordinate system on the reference point of the wire-pulling measuring device, record the force direction of the multi-axis force sensor 4 corresponding to the wire pulling length of 500mm in the wire-pulling measuring device, and determine the contact point between the wire pulled from the first pulley 8-1 and the second pulley 8-2 according to the reference point of the wire-pulling measuring device and the force direction of the multi-axis force sensor 4, and the contact point is referred to as the second entry point for short; its geometric relationship is as follows: Figure 4 As shown;

[0084] Step 2: Connect the end of the wire of the wire measuring device to the end of the robot to be calibrated;

[0085] Step 3: Control the robot to be calibrated to move to 50 teaching points in sequence through the teaching pendant, obtain the positions and joint parameter information of the 50 end teaching points of the robot to be calibrated, obtain the rope length between the reference point of the wire measurement device and the 50 teaching points, and the force direction corresponding to the multi-axis force sensor 4;

[0086] Step 4: According to the multiple force directions obtained in step S3 and the second line entry point positions determined in step 1, determine the positions of 50 second line exit points; their geometric relationship is as follows: Fig. 9 As shown;

[0087] Step 5: According to the 50 end teaching point positions, 50 rope lengths and 50 second line-out point positions of the robot to be calibrated, the distance from the 50 end positions of the robot to the reference point is determined, referred to as the actual distance;

[0088] Step 6: According to the joint parameter information displayed by the teaching pendant of the robot to be calibrated, the homogeneous transformation matrix equation from the robot end coordinate system to the robot base coordinate system is established, and the nominal position from the robot end coordinate system to the robot base coordinate system is calculated, referred to as the nominal position; a total of 50 nominal positions are obtained;

[0089] The kinematic parameters of the industrial robot are shown in Table 1.

[0090] Table 1 Kinematic parameters of industrial robots

[0091]

[0092] In Table 1, lx, ly, and lz represent the length information of the wire adapter in three coordinate directions.

[0093] Step 7: Calculate the nominal position of the reference point in the robot base coordinate system according to the nominal position and the actual distance, referred to as the nominal reference point position;

[0094] Step 8: Calculate the distance from the nominal position of the robot end to the nominal reference point position according to the nominal reference point position and the nominal position, referred to as the nominal distance;

[0095] Step 9: Subtract the nominal distance from the actual distance to obtain a distance error of the robot end relative to the reference point, referred to as distance error;

[0096] Step 10: According to the nominal distance, nominal position and the robot joint parameter information to be calibrated, establish the relationship between the distance error and the robot parameter error, referred to as the distance error model; bring the distance error into the distance error model, and obtain the robot joint parameter error through the least squares method. Compensate the robot joint parameter error to the robot joint parameter, and then control the robot to be calibrated to move to multiple teaching points in sequence through the teach pendant according to the compensated robot joint parameters, and finally obtain the distance error for verification. The verification results are shown in Table 2.

[0097] Table 2 Comparison results of distance errors after calibration by the traditional calibration method and the method of the present invention

[0098] Maximum value (mm) Average value(mm) Standard deviation (mm) Traditional calibration method 0.76461 0.13188 0.17486 Method of the present invention 0.35468 0.08245 0.10283

[0099] By applying the above technical solution, it can be seen that the method of the present invention can reduce the measurement error by determining the second outlet point and participating in the compensation. The simulation results of robot calibration by the method of the present invention and the traditional calibration method are shown in Table 2. It can be seen from Table 2 that compared with the results of the traditional calibration method using a wire-drawing measurement device (i.e., not considering the second outlet point), the maximum value accuracy of the method of the present invention is improved by 53.61%, the average value accuracy is improved by 37.48%, and the standard deviation accuracy is improved by 41.19%.

[0100] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A wire drawing measuring device, characterized in that: It comprises a wire pulling sensor (1), a wire pulling guide mechanism (3), and a multi-axis force sensor (4); the wire pulling guide mechanism (3) is connected to the wire pulling sensor (1), and the multi-axis force sensor (4) is connected to the wire pulling guide mechanism (3).

2. The wire drawing measuring device according to claim 1, characterized in that: The wire pulling guide mechanism (3) comprises an online guide mechanism, a wire guiding mechanism, and an offline guide mechanism; the online guide mechanism is connected to the offline guide mechanism via the wire guiding mechanism; the online guide mechanism is used to lead the wire on the wire pulling sensor (1) to the wire guiding mechanism, the wire guiding mechanism is used to guide the wire led out by the online guide mechanism to the offline guide mechanism, and the offline guide mechanism is used to lead out the wire guided by the wire guiding mechanism.

3. The wire drawing measuring device according to claim 2, characterized in that: The online guiding mechanism comprises a first upper base (11), a second upper base (12), a first pulley (8-1), and a first shaft (10-1); the second upper base (12) and the first upper base (11) are respectively fixed inside the wire pulling sensor (1), the two ends of the first shaft (10-1) are respectively interference fit with the mounting holes on the second upper base (12) and the first upper base (11), the first pulley (8-1) is mounted on the first shaft (10-1), the wire pulling on the wire pulling sensor (1) is guided to a first wire entry point of the first pulley (8-1) via a guide column, and then led out to the wire guiding mechanism via a first wire exit point of the first pulley (8-1).

4. The wire drawing measuring device according to claim 2, characterized in that: The wire guiding mechanism comprises a wire step shaft (13), a self-aligning ball bearing (15), and a thrust ring (14); the wire step shaft (13) and the inner ring of the self-aligning ball bearing (15) are interference fit; the thrust ring (14) is arranged above the self-aligning ball bearing (15); the self-aligning ball bearing (15) is clamped by the thrust ring (14) and the shoulder of the wire step shaft (13); the outer ring of the self-aligning ball bearing (15) and the lower housing (6) are interference fit; the wire drawn out from the first wire outlet point of the first pulley (8-1) in the warp guide mechanism is guided to the second wire entry point of the second pulley (8-2) in the offline guide mechanism through the wire guiding mechanism.

5. The wire drawing measuring device according to claim 2, characterized in that: The offline guiding mechanism comprises a first lower base (16), a second lower base (17), a second pulley (8-2), and a second shaft (10-2); the first lower base (16) is connected to the second lower base (17) and clamps the conductor stepped shaft (13) in the wire guiding mechanism; one end of the second shaft (10-2) is interference-fitted with the mounting hole on the first lower base (16); the other end of the second shaft (10-2) is clearance-fitted with the mounting hole on the second lower base (17) and the other end extends out of the hole to cooperate with the multi-axis force sensor (4); the second shaft (10-2) is fixedly mounted on the first lower base (16) and the second lower base (17), and the second pulley (8-2) is mounted on the second shaft (10-2); the wire guide mechanism is guided to the second wire entry point of the second pulley (8-2) by the offline guiding mechanism, and the wire is led out from the reference point / second wire exit point of the second pulley (8-2).

6. A method for determining the position of a wire outlet point in a wire measuring device, characterized in that: The following steps are involved: Step 1: Place a wire-pulling measuring device and a target object to be calibrated on the same workbench plane, and pull the wire in the wire-pulling measuring device from a reference point of the wire-pulling measuring device in a direction parallel to the workbench plane to a predetermined length L1; then subtract the length L2 measured by the wire-pulling sensor (1) from the length L1, and use the value obtained after the subtraction as the distance from the reference point of the wire-pulling measuring device to the initial position of the wire-pulling sensor (1), referred to as the reference distance; establish a measurement coordinate system on the reference point of the wire-pulling measuring device, record the force direction of the multi-axis force sensor (4) corresponding to the wire-pulling measuring device when the wire is pulled out to a length L1, and determine the contact point between the wire pulled from the first pulley (8-1) and the second pulley (8-2) based on the reference point of the wire-pulling measuring device and the force direction of the multi-axis force sensor (4), the contact point being referred to as the second wire entry point; Step 2: Connect the end of the wire of the wire measuring device to the end of the target object to be calibrated; Step 3: Control the target object to be calibrated to move to multiple teaching points in sequence, obtain the positions of the multiple teaching points and joint parameter information of the target object to be calibrated, obtain the rope length between the reference point of the wire pulling measurement device and the multiple teaching points, and the force direction corresponding to the multi-axis force sensor (4); Step 4: Determine multiple second line-out point positions according to the multiple force directions obtained in step S3 and the second line-in point positions determined in step 1.

7. A robot distance error calibration method, characterized in that: When the object to be calibrated is a robot, the specific steps of the method are as follows: Step 1: When the object to be calibrated is a robot, a plurality of second wire-out point positions corresponding to when the robot to be calibrated moves to a plurality of teaching points in sequence are determined according to a method for determining the wire-out point positions in a wire-drawing measuring device; Step 2: According to the multiple teaching point positions, multiple rope lengths and multiple second line-out point positions of the robot to be calibrated, the distance from the multiple teaching point positions of the robot to the reference point is determined, referred to as the actual distance; Step 3: According to the joint parameter information displayed by the teaching pendant of the robot to be calibrated, the homogeneous transformation matrix equation from the robot end coordinate system to the robot base coordinate system is established, and the nominal position from the robot end coordinate system to the robot base coordinate system is calculated, referred to as the nominal position; Step 4: Calculate the nominal position of the reference point in the robot base coordinate system according to the nominal position and the actual distance, referred to as the nominal reference point position; Step 5: Calculate the distance from the nominal position of the robot end to the nominal reference point position according to the nominal reference point position and the nominal position, referred to as the nominal distance; Step 6: Subtract the nominal distance from the actual distance to obtain the distance error of the robot end relative to the reference point, referred to as the distance error; Step 7: According to the nominal distance, nominal position and the robot joint parameter information to be calibrated, the relationship between the distance error and the robot parameter error is established, which is referred to as the distance error model; the distance error is brought into the distance error model, and the error of the robot joint parameters can be obtained through the least squares method.

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