An auxiliary calibration device for a grinding wheel tool coordinate system and a method thereof

Abstract

The application belongs to the technical field of robot calibration, and discloses an auxiliary calibration device for a grinding wheel tool coordinate system and a method thereof. The auxiliary calibration device comprises a posture measuring device and a position calibration device. The posture measuring device comprises a motor-driven screw rod lifting platform arranged on a base through two guide rails, a laser imager and a first convex lens are installed side by side on the lifting platform, and a display and two laser ranging sensors are installed on the base. In addition, the position calibration device comprises mechanical clamps installed on both sides of a bottom plate through two connecting rods, a point light source, an electronic level, a limiting frame and a second convex lens are installed on the bottom plate through a support frame. The application adopts an optical-electric calibration method to avoid contact between a robot tool and a calibration cone, which can not only reduce damage to the tool, but also improve the calibration accuracy, and effectively solves the calibration problem of the grinding wheel tool for the tool coordinate system of the industrial robot.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of robot calibration, and particularly relates to an auxiliary calibration device for a grinding wheel tool coordinate system and a method thereof, which mainly solves the calibration problem of the grinding wheel tool for the tool coordinate system of an industrial robot. BACKGROUND

[0002] In the application of industrial robots, we usually install different tools at the end of the robot to meet the actual production needs. Therefore, in order to accurately control the position and attitude of the tool, it is necessary to calibrate the coordinate system in which the tool is located. At present, robot tool calibration mainly adopts the following two ways: (1) robot teaching calibration method, which mainly controls the robot to touch the coordinate system origin of the tool with the fixed point in space at different attitudes, so as to calculate the value of the tool coordinate system origin. This calibration method is simple and easy to operate, but the actual operation is relatively difficult, the calibration result has human error and is not accurate, so it is only suitable for tools with obvious feature points. (2) external position measurement device calibration, that is, using industrial cameras, laser trackers, three-coordinate measuring instruments and other devices for calibration. Although this kind of calibration method has high precision, the cost is very high, the operation is complex, and professional technical personnel are needed.

[0003] In view of the problems existing in the prior art, in the robot teaching calibration method, Chinese patent CN201810562692.7 discloses an industrial robot tool coordinate system calibration device. The calibration device is fixed with a scale composed of X-axis calibration ruler, Y-axis calibration ruler and Z-axis calibration ruler sliding on the calibration flange. During calibration, the operator manually records the current X, Y and Z axis scale values, and compares them with the teaching result to assist calibration. In the external position measurement device calibration, Chinese patent CN202211638776.7 discloses a mechanical arm tool coordinate system calibration method and device. In this scheme, the position calibration is realized by the coincidence of the positions of the first four calibration points, and the attitude calibration is realized by the special orientation relationship between the last three points, so that the attitude of the mechanical arm tool coordinate system can be calculated. In addition, Chinese patent CN202111209743.6 discloses a robot tool coordinate system calibration device and method. In this scheme, two light beam sensors are arranged on the workbench. The two light beams emitted by the light beam sensors are parallel to the workbench and intersect each other. In the case that the end of the tool is not equal in thickness, the deviation of the calculated Z-axis direction of the tool can be reduced or avoided, so as to improve the accuracy of tool calibration.

[0004] In the bar grinding process, the surface of special steel bar products often has various defects such as cracks and scratches, which need to be eliminated by grinding to meet the subsequent production requirements. We install a grinding head on the flange at the end of the industrial robot, and control the robot to complete the grinding according to the diameter of the bar, the position and type of the defect, but before carrying out all the processes, the calibration of the grinding wheel tool coordinate system must be completed first, and the purpose of calibration is to find the homogeneous transformation matrix of the robot tool coordinate system relative to the robot end flange coordinate system, so as to ensure the accuracy of the actual trajectory of the grinding wheel tool. As shown in the accompanying drawings, Figure 6 The calibration of the grinding wheel tool coordinate system mainly includes the calibration of the position of the tool coordinate system origin and the calibration of the attitude of the tool coordinate system. When the grinding wheel tool is installed on the end flange of the robot, the pose of the tool coordinate system relative to the robot end flange coordinate system is basically determined, the goal of position calibration is to find the coordinates of the tool coordinate system origin (TCP) in the robot end flange coordinate system, and the goal of attitude calibration is to find the rotation matrix of the tool coordinate system relative to the end flange coordinate system. The calibration of the grinding wheel tool coordinate system in the above three schemes still has the following technical problems: (1) schemes one and two can theoretically obtain the coordinates of the tool coordinate system origin in the robot end flange coordinate system, but the attitude of the grinding wheel tool coordinate system cannot be calibrated, and in addition, due to the influence of the grinding tool structure, it cannot be applied in actual calibration; (2) scheme three can be applied to the calibration of the grinding wheel tool coordinate system, but in actual calibration, the operator determines that the tool end is located at the intersection center of the laser beam through visual observation, and the accuracy cannot be guaranteed; at the same time, when the operator controls the tool end to coincide with the intersection center of the laser beam, not only a long time is spent, but also the accuracy of tool calibration is affected. Therefore, the above-mentioned schemes cannot be applied to the calibration of the grinding wheel tool coordinate system. Therefore, it is urgent to design an auxiliary device and a new calibration method for calibrating the attitude and position of the grinding wheel tool coordinate system. SUMMARY

[0005] Based on the deficiencies of the above-mentioned schemes, the calibration of the grinding wheel tool coordinate system is divided into two parts, namely the calibration of the position of the tool coordinate system origin and the calibration of the attitude of the tool coordinate system. The goal of position calibration is to find the coordinates of the tool coordinate system origin (TCP) in the robot end flange coordinate system; the goal of attitude calibration is to find the rotation matrix of the tool coordinate system relative to the end flange coordinate system.

[0006] Therefore, two prerequisites for the pose calibration are: (1) the XOY plane of the robot base coordinate system {B} is horizontal, and the Z axis is vertical; (2) when the grinding wheel is grinding the bar, the grinding wheel axis should be kept horizontal and perpendicular to the bar axis, and the direction of the bar axis is parallel to the moving direction of the robot base coordinate system. According to the above, the pose of the tool coordinate system is defined as follows: a. the X axis (or the Y axis) of the tool coordinate system is consistent with the direction of the grinding wheel axis, b. when the side plane of the grinding wheel is vertical, the Z axis of the tool coordinate system passes through the grinding wheel axis and is vertical upward (it should be noted that the coordinate axes of the tool coordinate system are fixed on the tool, and when the pose of the tool changes, the pose of the coordinate axes also changes) c. the Y axis (or the X axis) is perpendicular to the plane in which the two axes lie. When the robot tool coordinate system and the base coordinate system have the same pose, the rotation matrix of the robot base coordinate system relative to the end coordinate system is the same as the rotation matrix of the grinding wheel tool coordinate system relative to the end coordinate system. In the above assumptions for the pose calibration, the definition of the pose of the tool coordinate system and the pose required in the grinding wheel space during calibration have been clarified. In terms of specific operation, that is:

[0007] a. the direction of the grinding wheel axis is parallel to the XOY plane of the robot base coordinate system.

[0008] b. ensure that the direction of the grinding wheel axis is perpendicular to the moving direction of the robot base.

[0009] c. In addition, in order to make the obtained pose of the grinding wheel coordinate system as close as possible to the pose of the robot end flange coordinate system, the Z axis of the robot flange end coordinate system is first adjusted to be vertical before calibration.

[0010] According to the above object, it is difficult to directly determine the pose of the grinding wheel axis in space, so an indirect method can be used to achieve the above object, that is, by determining the spatial pose of the grinding wheel plane to ensure the spatial pose of the grinding wheel axis. Specifically, when the side plane of the grinding wheel is vertical in space and parallel to the moving direction of the robot base coordinate system, the grinding wheel axis satisfies the above objects a and b.

[0011] The prerequisite for position calibration is that when the robot is grinding the bar, the surface of the grinding wheel is always in contact with the surface of the bar. Although the grinding wheel is always rotating, the position of the contact point relative to the coordinate system of the end flange is constant in a short time, so the contact point is defined as the origin of the grinding wheel coordinate system. Specifically, the point is located at the center of the lowermost end of the grinding wheel, and the coordinates of the contact point relative to the end flange coordinate system are calculated to obtain the translation operator of the grinding wheel tool coordinate system relative to the flange coordinate system.

[0012] Based on this, the application provides an auxiliary calibration device and method for the grinding wheel tool coordinate system.

[0013] In order to achieve the above object, the following technical scheme is adopted: An auxiliary calibration device for a grinding wheel tool coordinate system comprises a posture measuring device and a position calibration device, the posture measuring device comprises a base, transverse support blocks and vertical support blocks are respectively arranged at two ends of the base, leveling knobs are arranged at bottoms of two ends of the transverse support blocks and a center bottom of the vertical support block to form a tripod support mechanism, two guide rails are respectively arranged on the base through sleeve seats, top ends of the two guide rails are connected through a cross beam plate, a display and two laser ranging sensors are symmetrically arranged on the base, signal output ends of the two laser ranging sensors are connected with the display, the display is also used to display whether the posture measuring device is in a horizontal state under cooperation of the three leveling knobs, a lead screw is rotatably arranged on the base through a ball bearing, a top end of the lead screw is rotatably connected with the cross beam plate, and a bottom end of the lead screw is connected with an output end of a motor, the motor is arranged on the base, a lifting platform is slidably arranged on the two guide rails, the lifting platform is connected with the lead screw through a screw hole connector, a laser imager is arranged on the lifting platform, two half-width supports are arranged on the frame of the laser imager through four bolts, two first convex lenses are arranged between the two half-width supports; the position calibration device comprises a base plate, two connecting rods are respectively arranged on two sides of the base plate, mechanical clamps are respectively arranged at two ends of the two connecting rods, a point light source and a second convex lens are respectively arranged on one side of the center of the base plate through a support frame, a limiting frame is arranged on the other side of the center of the base plate, and an electronic level is arranged on the base plate.

[0014] As a further supplementary explanation of the above technical scheme, the laser imager is connected with a connecting support through an extension arm, and the connecting support is arranged on the lifting platform.

[0015] As a further supplementary explanation of the above technical scheme, a plug-in connector is arranged on the laser imager, a plug-in connector head corresponding to the plug-in connector is arranged on one end of the extension arm, at least two plug-in shafts are fixedly connected to the other end of the extension arm, and plug-in holes corresponding to the plug-in shafts are arranged on the connecting support.

[0016] As a further supplementary explanation of the above technical scheme, a first pinch groove hole is arranged on the vertical support block, and a second pinch groove hole is arranged on the extension arm, so that the posture measuring device is moved by an operator.

[0017] As a further supplementary explanation of the above technical scheme, at least two pairs of slide hole connectors are arranged on the lifting platform, and the two guide rails are respectively arranged on the lifting platform through the slide hole connectors.

[0018] As a further supplementary description of the above technical scheme, the mechanical gripper comprises two support plates, and the two support plates are connected by a pipe; mechanical arms are rotatably connected to the two ends of the two support plates by pin shafts; plug-in rods are rotatably connected to the bottom ends of the two mechanical arms; U-shaped grippers are plugged into the plug-in rods; the top ends of the two mechanical arms are rotatably connected to one end of a hinged connecting rod by a pin shaft; a screw hole is provided in the center of the pipe; a hand wheel screw is arranged in the screw hole of the pipe; a connecting block is arranged on the hand wheel screw; the other end of the hinged connecting rod is hingedly connected to the connecting block; and mounting holes corresponding to the two connecting rods are concentrically arranged at the two ends of the two support plates.

[0019] A calibration method for a grinding wheel tool coordinate system auxiliary calibration device according to one of the above schemes, comprising posture calibration of the grinding wheel tool coordinate system by a posture measurement device and origin position calibration of the grinding wheel tool coordinate system by a position calibration device, which comprises the following steps:

[0020] S1, the posture measurement device is placed on one side of the end face of the grinding wheel; three leveling knobs are first adjusted; and the posture measurement device is observed to be in a horizontal state through a display;

[0021] S2, after the operation of S1 is completed, the laser ranging sensor is turned on; the posture measurement device is moved; the display is observed to detect the readings of the two laser ranging sensors on the moving track; and the posture measurement device is no longer moved until the readings of the two laser ranging sensors are equal;

[0022] S3, after the operations of S1 and S2 are completed, the position of the posture measurement device is locked; a laser emitter is installed on the end face of the grinding wheel; the motor drive screw is started to move the lifting platform up and down until the center of the first convex lens is aligned with the axis of the grinding wheel;

[0023] S2, the laser emitter is turned on and the grinding wheel is continuously rotated; the laser emitter continuously emits laser to the first convex lens; the position of the observation aperture of the robot is adjusted; the laser can form an aperture on the laser imager through the first convex lens; if the side plane of the grinding wheel is parallel to the vertical plane of the laser imager, the shape of the aperture is a standard circle, otherwise the shape of the aperture is an ellipse; when the shape of the aperture is a standard circle, it indicates that the vertical plane of the laser imager is parallel to the moving direction of the robot base coordinate system, and the side plane of the grinding wheel reaches the same posture as the laser imager;

[0024] S5, after the operations of S1 to 4 are completed, the posture of the end coordinate system of the robot in this posture is read on the teach pendant; the rotation matrix of the base coordinate system relative to the end coordinate system is calculated, which is the rotation matrix of the grinding wheel coordinate system relative to the end coordinate system; and the calibration of the tool coordinate system posture is completed;

[0025] S6, after the posture calibration of the grinding wheel tool coordinate system is completed, the two mechanical clamps are used to jointly clamp the end face of the grinding wheel, and the limiting frame is in abutment with the edge of the grinding wheel, so that the three-point fixing is formed, and the position calibration device is fixed on the grinding wheel;

[0026] S7, the grinding wheel is started to rotate, and the rotation of the grinding wheel is controlled by the signal feedback of the electronic level, that is, when the electronic level shows the horizontal, the grinding wheel is locked to prevent it from rotating;

[0027] S8, a light screen is fixed on the ground and located directly below the grinding wheel;

[0028] S9, the point light source is turned on, and the robot is operated so that the light emitted by the robot converges on the ground light screen to form point A after passing through the second convex lens. The focal length of the second convex lens is s, that is, the distance from point A to the center of the second convex lens is also s. Since the tool coordinate system origin, the center of the second convex lens and point A are located on the Z axis of the tool coordinate system, the distance from the tool coordinate system origin to the center of the second convex lens is recorded as h, and the distance from the tool coordinate system origin to point A is recorded as d, that is, d = s + h;

[0029] S10, a point is set on the light screen and recorded as point B. The robot is operated so that point A reaches point B. Then, the posture of the robot is changed four times while keeping the position of point A unchanged, and the rotation angles of the six-axis joints of the robot and the position of the origin of the end flange coordinate system of the robot in the base coordinate system under the four postures are recorded in sequence;

[0030] S11, the least square method is used to establish a calibration equation, the position information recorded each time is substituted into the calibration equation, the coordinates of point A in the end flange coordinate system of the robot are calculated, and the position of the tool coordinate system origin is calculated through the fixed distance between point A and the tool coordinate system origin, so as to complete the calibration of the position of the tool coordinate system origin of the robot.

[0031] As a further explanation of the above technical solution, in S10, point A reaches point B in four different postures, and the rotation angles of the six-axis joints of the teach pendant and the position M i and the rotation matrix are recorded in sequence. i and the rotation matrix information are listed as follows:

[0032]

[0033] In the formula: is the rotation matrix of the flange coordinate system to the base coordinate system, is the coordinates of point A in the flange coordinate system, is the coordinates of the origin of the flange coordinate system in the flange coordinate system, since point A is always located at the same position, Therefore, the above four equations are subtracted in turn to obtain a calibration equation:

[0034]

[0035] The least square method or singular value decomposition method is used to solve the above linear equations, and the coordinates of point A in the robot flange coordinate system are obtained

[0036] Compared with the prior art, the present application has the following advantages:

[0037] 1. The present application is based on the basic principles of traditional methods and optics to design a non-contact auxiliary calibration device applied to the calibration of the grinding wheel tool coordinate system, that is, the position calibration device is used to find the coordinates of the tool coordinate system origin (TCP) in the robot end flange coordinate system; the posture measurement device is used to find the rotation matrix of the tool coordinate system relative to the end flange coordinate system. Compared with the traditional calibration method, the robot tool is avoided from contacting the calibration cone, which not only reduces the damage to the tool, but also further improves the accuracy of the calibration.

[0038] 2. In the posture calibration of the grinding wheel tool coordinate system, the present application first adjusts three leveling knobs, and observes through the display to make the posture measurement device in a horizontal state, then turns on the laser ranging sensor, moves the posture measurement device, and observes through the display to detect the readings of the two laser ranging sensors on the moving track, until the readings of the two laser ranging sensors are equal, then the position of the posture measurement device is locked, then the laser emitter is installed on the end face of the grinding wheel, the motor drive screw is started to move the lifting platform up and down until the center of the first convex lens is aligned with the axis of the grinding wheel, the laser emitter is turned on and the grinding wheel is started to rotate, the laser emitter continuously emits laser to the first convex lens, the position of the robot observation aperture is adjusted, and the laser can form a circle on the laser imager through the first convex lens, when the shape of the circle is a standard circle, it means that the vertical plane where the laser imager is located is parallel to the moving direction of the robot base coordinate system, and the side plane of the grinding wheel reaches the same posture as the laser imager. When the tool coordinate system of the robot is consistent with the base coordinate system, the rotation matrix of the robot base coordinate system relative to the end coordinate system is the same as the rotation matrix of the grinding wheel tool coordinate system relative to the end flange coordinate system, so the definition and calibration of the tool coordinate system posture is the same as the posture required in the grinding wheel space.

[0039] 3、The present application in the origin position calibration of grinding wheel tool coordinate system, control robot with four different postures to make the point light source projection on the screen A point is located in the same position, and record the robot in four postures six-axis joint rotation angle and the position of the robot end flange coordinate system origin under the base coordinate system in turn, using the least square method to establish calibration equation, put the recorded position information into calibration equation, calculate the coordinates of A point in the robot end flange coordinate system, through the fixed distance between A point and the origin of tool coordinate system, the position of the origin of tool coordinate system is calculated, the calibration of the origin position of robot tool coordinate system is completed.

[0040] 4、The present application realizes clamping through the rotation of mechanical clamping jaw hand wheel screw, wherein the screw drive can ensure the self-locking of clamping, the synchronous movement of the two U-shaped clamping jaws of the mechanical clamping jaw can maintain the axial symmetry of clamping to ensure the circumferential symmetry of clamping. At the same time, the limiting frame and the edge of the grinding wheel abut to assist the two mechanical clamping jaws to be uniformly clamped at both ends of the grinding wheel, to complete the formation of three-point fixing, and firmly fix the position calibration device on the grinding wheel.

[0041] 5、The present application can display the posture information of the position calibration device through the electronic level to quickly find the point where the lowermost end of the grinding wheel contacts the bar. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a structural schematic view of the posture measuring device in the present application;

[0043] Figure 2 It is an exploded schematic view of the posture measuring device in the present application;

[0044] Figure 3 It is a structural schematic view of the position calibration device in the present application;

[0045] Figure 4 It is an exploded schematic view of the position calibration device in the present application;

[0046] Figure 5 It is Figure 4 It is an exploded schematic view of the mechanical clamping jaw in the present application;

[0047] Figure 6 It is a schematic view of the robot driving grinding wheel tool to grind pipe bar in the present application;

[0048] Figure 7 It is a working principle diagram of the posture calibration of grinding wheel tool coordinate system by using the posture measuring device in the present application;

[0049] Figure 8 It is a working principle diagram of the origin position calibration of grinding wheel tool coordinate system by using the position calibration device in the present application.

[0050] In the figure: the base is 1, the display is 2, the laser ranging sensor is 3, the sleeve seat is 4, the guide rail is 5, the cross beam plate is 6, the ball bearing is 7, the screw is 8, the motor is 9, the lifting platform is 10, the laser imager is 11, the sleeve is 12, the half-width support is 13, the first convex lens is 14, the connecting support is 15, the extension arm is 16, the insertion hole is 17, the insertion shaft is 18, the insertion connecting seat is 19, the insertion connecting head is 20, the sliding hole connecting seat is 21, the screw hole connecting piece is 22, the transverse support block is 23, the vertical support block is 24, the leveling knob is 25, the first pinch slot hole is 26, the second pinch slot hole is 27, the bottom plate is 28, the connecting rod is 29, the mechanical clamp jaw is 30, the support frame is 31, the point light source is 32, the second convex lens is 33, the limiting frame is 34, the electronic level is 35, the grinding wheel is 36, the end flange is 37, the laser emitter is 38, the moving track is 39, and the light screen is 40.

[0051] The attitude measuring device is 100, and the position calibration device is 200.

[0052] Among them, the mechanical clamp jaw includes a support plate 3001, a mechanical arm 3002, an insertion rod 3003, a U-shaped clamp jaw 3004, a pipe 3005, a screw hole 3006, a handwheel screw 3007, a connecting block 3008, a hinged connecting rod 3009, and a mounting hole 3010. DETAILED DESCRIPTION

[0053] In order to further illustrate the technical solutions of the present application, the following will combine the drawings of the present application with the specific embodiments of the present application to further illustrate the technical solutions of the present application. Figures 1 to 8 We further illustrate the present application through the optimal embodiment.

[0054] An auxiliary calibration device for a grinding wheel tool coordinate system includes an attitude measuring device and a position calibration device.

[0055] As shown in the accompanying drawings Figure 1 And 2As shown, the attitude measuring device 100 includes a base 1, transverse support blocks 23 and vertical support blocks 24 are mounted at both ends of the base 1, leveling knobs 25 are arranged at the bottom of both ends of the transverse support blocks 23 and the center bottom of the vertical support blocks 24 to form a tripod support mechanism, two guide rails 5 are installed on the base 1 through sleeve seats 4, the top ends of the two guide rails 5 are connected through a cross beam plate 6, a display 2 and two laser ranging sensors 3 symmetrically installed are installed on the base 1, the signal output ends of the two laser ranging sensors 3 are connected with the display 2, the display 2 is also used to display whether the attitude measuring device 100 is in a horizontal state under the cooperation of the three leveling knobs 25, a lead screw 8 is rotatably installed on the base 1 through a ball bearing 7, the top end of the lead screw 8 is rotatably connected with the cross beam plate 6, and the bottom end thereof is connected with the output end of a motor 9, the motor 9 is installed on the base 1, at least two pairs of slide hole connecting seats 21 are arranged on the lifting platform 10, the two guide rails 5 pass through the slide hole connecting seats 21 to slideably arrange the lifting platform 10 on the two guide rails 5, the lifting platform 10 is connected with the lead screw 8 through a screw hole connecting piece 22, a laser imager 11 is connected with a connecting support 15 through an extension arm 16, the connecting support 15 is installed on the lifting platform 10, two half brackets 13 are installed on the frame of the laser imager 11 through four sleeves 12 connected by bolts at four corners thereof, and a first convex lens 14 is embedded between the two half brackets 13.

[0056] The specific connection mode is that a plug-in connecting seat 19 is installed on the laser imager 11, a plug-in connecting head 20 corresponding to the plug-in connecting seat 19 is installed on one end of the extension arm 16, at least two plug-in shafts 18 are fixedly connected on the other end of the extension arm 16, and plug-in holes 17 corresponding to the plug-in shafts 18 are arranged on the connecting support 15.

[0057] As a further preferred embodiment of the present embodiment, a first pinch slot hole 26 is arranged on the vertical support block 24, and a second pinch slot hole 27 is arranged on the extension arm 16, so that the attitude measuring device 100 is moved by the operator.

[0058] (II) as shown in the accompanying Figures 3 to 4 As shown, the position calibration device 200 includes a base plate 28, two connecting rods 29 are respectively installed on both sides of the base plate 28, mechanical clamps 30 are respectively installed at both ends of the two connecting rods 29, a point light source 32 and a second convex lens 33 are respectively installed on one side of the center of the base plate 28 through a support frame 31, a limiting frame 34 is installed on the other side of the center of the base plate 28, and an electronic level 35 is installed on the base plate 28.

[0059] As shown in the accompanying drawings Figure 5 Further preferably, the mechanical gripper 30 comprises two support plates 3001 connected by a pipe 3005, and a mechanical arm 3002 is rotatably connected to each end of the two support plates 3001 by a pin shaft, a plug-in rod 3003 is rotatably connected to the bottom end of each mechanical arm 3002, a U-shaped gripper 3004 is plugged into each plug-in rod 3003, a hinge connecting rod 3009 is rotatably connected to the top end of each mechanical arm 3002 by a pin shaft, a screw hole 3006 is provided in the center of the pipe 3005, a handwheel screw 3007 is provided in the screw hole 3006 of the pipe 3005, a connecting block 3008 is provided on the handwheel screw 3007, the other ends of the two hinge connecting rods 3009 are hingedly connected to the connecting block 3008, and mounting holes 3010 corresponding to the two connecting rods 29 are concentrically provided at both ends of the two support plates 3001.

[0060] As shown in the accompanying drawings 7 and 8, a calibration method using the auxiliary calibration device for the grinding wheel tool coordinate system in the above embodiment includes using the attitude measuring device 100 to calibrate the attitude of the grinding wheel 36 tool coordinate system and using the position calibration device 200 to calibrate the origin position of the grinding wheel 36 tool coordinate system, which includes the following steps:

[0061] S1, place the attitude measuring device 100 on one side of the end face of the grinding wheel 36, first adjust the three leveling knobs 25, and observe the attitude measuring device 100 to be in a horizontal state through the display 2;

[0062] S2, after completing the operation of S1, turn on the laser ranging sensor 3, move the attitude measuring device 100, and observe the readings of the two laser ranging sensors 3 detecting the moving track 39 through the display 2, until the readings of the two laser ranging sensors 3 are equal, then stop moving;

[0063] S3, after completing the operations of S1 and S2, lock the position of the attitude measuring device 100, install the laser emitter 38 on the end face of the grinding wheel 36, start the motor 9 to drive the screw 8 to move the lifting platform 10 up and down until the center of the first convex lens 14 is aligned with the axis of the grinding wheel 36;

[0064] S2, open the laser emitter 38 and start the grinding wheel 36 to rotate continuously, make the laser emitter 38 emit laser light to the first convex lens 14 continuously, adjust the position of the robot observation aperture, so that the laser light can form a circle on the laser imager 11 through the first convex lens 14, if the side plane of the grinding wheel 36 is parallel to the vertical plane of the laser imager 11, the shape of the circle is a standard circle, otherwise the shape of the circle is an ellipse, when the shape of the circle is a standard circle, it means that the vertical plane of the laser imager 11 is parallel to the moving direction of the robot base coordinate system, and the side plane of the grinding wheel reaches the same posture as the laser imager 11;

[0065] S5, after the operations of S1 to S4 are completed, the posture of the robot end coordinate system in this posture is read on the teach pendant, and the rotation matrix of the base coordinate system relative to the end coordinate system is calculated, that is, the rotation matrix of the grinding wheel coordinate system relative to the end coordinate system, and the calibration of the tool coordinate system posture is completed;

[0066] S6, after the posture calibration of the tool coordinate system of the grinding wheel 36 is completed, the two mechanical clamps 30 are used to clamp the end face of the grinding wheel 36 together, and the position limiting frame 34 is in contact with the edge of the grinding wheel 36, so that a three-point fixing is formed to fix the position calibration device 200 on the grinding wheel 36;

[0067] S7, start the grinding wheel 36 to rotate, and use the signal feedback of the electronic level 35 to control the rotation of the grinding wheel 36, that is, when the electronic level 35 shows level, the grinding wheel 36 is locked to prevent it from rotating;

[0068] S8, fix a light screen 40 on the ground, and make it located directly below the grinding wheel 36;

[0069] S9, open the point light source 32, operate the robot, so that the light emitted by the robot will converge to the ground light screen 40 to form point A after passing through the second convex lens 33, and the focal length of the second convex lens 33 is s, that is, the distance from point A to the center of the second convex lens 33 is also s, since the tool coordinate system origin, the center of the second convex lens 33 and point A are located on the Z axis of the tool coordinate system, the distance from the tool coordinate system origin to the center of the second convex lens 33 is recorded as h, and the distance from the tool coordinate system origin to point A is recorded as d, that is, d=s+h;

[0070] S10, set a point on the light screen 40 and mark it as point B, operate the robot to make point A reach point B, then change the posture of the robot four times while keeping the position of point A unchanged, and record the six-axis joint rotation angles of the robot and the position of the robot end flange 37 coordinate system origin in the base coordinate system under the four postures;

[0071] S11, the least square method is used to establish a calibration equation, the position information recorded each time is substituted into the calibration equation, the coordinates of point A in the robot end flange coordinate system are solved, the position of the tool coordinate system origin is calculated through the fixed distance between point A and the tool coordinate system origin, and the calibration of the position of the robot tool coordinate system origin is completed.

[0072] In S10, point A reaches point B in four different postures, and the rotation angles of the six-axis joints on the teach pendant and the position M of the end flange 37 coordinate system origin in the base coordinate system are recorded in sequence i and the rotation matrix, the following equation group is listed according to the position M i

[0073]

[0074] In the formula: is the rotation matrix of the flange coordinate system to the base coordinate system, is the coordinates of point A in the flange coordinate system, is the coordinates of the flange coordinate system origin in the flange coordinate system, since point A is always located at the same position, so Therefore, the calibration equation can be obtained by subtracting the above four equations in sequence:

[0075]

[0076] The least square method or singular value decomposition method is used to solve the above linear equation group, and the coordinates of point A in the robot flange coordinate system are obtained

[0077] The traditional calibration method generally makes the robot contact the tool coordinate system origin with a fixed position in space in four different postures and records the posture information of the robot, then constructs a calibration equation through the posture information of the robot, and finally solves the position of the tool coordinate system origin by the least square method. Therefore, the traditional calibration method needs the robot tool to contact the calibration cone, which not only easily causes damage to the tool, but also leads to the decline of the calibration precision. In contrast, the present application designs a non-contact position calibration device and its specific use method based on the basic principles of the traditional method and optics, avoids the contact between the robot tool and the calibration cone, can not only reduce the damage to the tool, but also can improve the calibration precision. It is especially suitable for the calibration operation of the grinding wheel tool coordinate system.

[0078] ​The foregoing merely illustrates the principles of the application. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the application and are thus within its spirit and scope. Furthermore, it will be appreciated that the various embodiments of the application described herein are not necessarily mutually exclusive. That is, some embodiments can include a combination of features from two or more of the embodiments described herein. It will also be appreciated that the embodiments described herein are not limited to the specific arrangements described, but that the application can be practiced with other arrangements without departing from the spirit or scope of the application. Thus, it will be appreciated that the embodiments described herein are illustrative of the principles of the application and are not meant to limit or restrict the scope of the application as encompassed by the appended claims. The scope of the application is thus not intended to be limited to the specific embodiments described herein, but rather encompasses numerous implementations consistent with the principles of the application.

[0079] Furthermore, it should be understood that although the description herein is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description herein is only for the sake of clarity. Those skilled in the art should consider the description as a whole, and the technical solutions in each embodiment can be combined appropriately to form other embodiments that those skilled in the art can understand.

Claims

1. An auxiliary calibration device for a grinding wheel tool coordinate system, characterized by: The utility model relates to a position calibration device and pose measuring device, including two parts of pose measuring device (100) and position calibration device (200), the pose measuring device (100) includes base (1), the transverse support block (23) is installed respectively in both ends of base (1), vertical support block (24) is installed respectively in both ends of base (1), the center bottom of vertical support block (24) is provided with leveling knob (25) respectively and forms tripod support mechanism, two guide rails (5) are installed on base (1) through sleeve seat (4), the top of two guide rails (5) is connected through crossbeam plate member (6), display (2) is installed on base (1), and two laser ranging sensors (3) are symmetrically installed, the signal output end of two laser ranging sensors (3) is connected with display (2) respectively, display (2) is also used to show whether the pose measuring device (100) is in horizontal state under the cooperation of three leveling knobs (25), screw rod (8) is rotatably installed on base (1) through ball bearing (7), the top of screw rod (8) is rotatably connected in crossbeam plate member (6), and its bottom end is connected with the output end of motor (9), motor (9) is installed on base (1), lifting platform (10) is slidably arranged on two guide rails (5), lifting platform (10) is connected with screw rod (8) through screw hole connecting piece (22), laser imager (11) is installed on lifting platform (10), two half-width supports (13) are installed with four sleeves (12) through bolt connection four corners of the frame of laser imager (11) respectively, first convex lens (14) is embedded between two half-width supports (13);The position calibration device (200) includes bottom plate (28), two connecting rods (29) are installed on both sides of bottom plate (28) respectively, mechanical clamp jaw (30) is installed on both ends of two connecting rods (29) respectively, point light source (32) is installed on one side of the center of bottom plate (28) respectively, and second convex lens (33) is installed through support frame (31), limit frame (34) is installed on the other side of the center of bottom plate (28), and electronic level (35) is installed on bottom plate (28).

2. The apparatus for assisting in the calibration of a grinding wheel tool coordinate system according to claim 1, wherein: The laser imager (11) is connected with the connecting support (15) through the extension arm (16), and the connecting support (15) is installed on the lifting platform (10).

3. The apparatus for assisting in the calibration of a grinding wheel tool coordinate system according to claim 2, wherein: A plug-in connector (20) corresponding to the plug-in connector (19) is installed on one end of the extension arm (16), and at least two plug-in shafts (18) are fixedly connected to the other end of the extension arm (16), and the connecting support (15) is provided with a plug-in hole (17) corresponding to the plug-in shaft (18).

4. The auxiliary calibration device for the grinding wheel tool coordinate system according to claim 2 or 3, characterized in that: First pinch slot holes (26) are arranged on the vertical support block (24), and second pinch slot holes (27) are arranged on the extension arm (16), so that the operator can move the posture measuring device (100).

5. The apparatus for assisting in the calibration of a grinding wheel tool coordinate system according to claim 4, wherein: At least two pairs of slide hole connecting seats (21) are arranged on the lifting platform (10), and the two guide rails (5) pass through the slide hole connecting seats (21) to slide the lifting platform (10) thereon.

6. The auxiliary calibration device for grinding wheel tool coordinate system according to any one of claims 1 to 3 or 5, characterized in that: The mechanical clamping jaw (30) comprises two support plates (3001) connected by a pipe (3005), a mechanical arm (3002) rotatably connected to each end of the two support plates (3001) through a pin shaft, a plug-in rod (3003) rotatably connected to the bottom end of each mechanical arm (3002), a U-shaped clamping jaw (3004) inserted on each plug-in rod (3003), a hinge connecting rod (3009) rotatably connected to the top end of each mechanical arm (3002) through a pin shaft, a screw hole (3006) arranged in the center of the pipe (3005), a hand wheel screw (3007) arranged in the screw hole (3006) of the pipe (3005), a connecting block (3008) arranged on the hand wheel screw (3007), the other ends of the two hinge connecting rods (3009) being hingedly connected to the connecting block (3008), and mounting holes (3010) corresponding to the two connecting rods (29) being arranged at the two ends of the two support plates (3001) concentrically.

7. A method for calibrating a grinding wheel tool coordinate system using the auxiliary calibration device of claim 6, characterized in that: The posture measurement device (100) is used to calibrate the posture of the grinding wheel (36) tool coordinate system, and the position calibration device (200) is used to calibrate the origin position of the grinding wheel (36) tool coordinate system, which comprises the following steps: S1, the posture measurement device (100) is placed on one side of the end face of the grinding wheel (36), three leveling knobs (25) are adjusted, and the posture measurement device (100) is observed to be in a horizontal state through the display (2); S2, after the operation of S1 is completed, the laser ranging sensor (3) is turned on, the posture measurement device (100) is moved, the display (2) is observed to detect the readings of the two laser ranging sensors (3) on the moving track (39), and the movement is stopped when the readings of the two laser ranging sensors (3) are equal; S3, after the operations of S1 and S2 are completed, the position of the posture measurement device (100) is locked, the laser emitter (38) is installed on the end face of the grinding wheel (36), the motor (9) is started to drive the lead screw (8) to move the lifting platform (10) up and down until the center of the first convex lens (14) is aligned with the axis of the grinding wheel (36); S2, open the laser emitter (38) and start the grinding wheel (36) to rotate continuously, make the laser emitter (38) emit laser to the first convex lens (14) continuously, adjust the position of the robot observation diaphragm, make the laser pass through the first convex lens (14) and form a diaphragm on the laser imager (11), if the side plane of the grinding wheel (36) is parallel to the vertical plane of the laser imager (11), the shape of the diaphragm is a standard circle, otherwise the shape of the diaphragm is an ellipse, when the shape of the diaphragm is a standard circle, it means that the vertical plane of the laser imager (11) is parallel to the moving direction of the robot base coordinate system, the side plane of the grinding wheel reaches the same posture as the laser imager (11); S5, complete the operations of S1 to S4, read the posture of the robot end coordinate system in the posture on the teach pendant, calculate the rotation matrix of the base coordinate system relative to the end coordinate system, that is, the rotation matrix of the grinding wheel coordinate system relative to the end coordinate system, complete the calibration of the tool coordinate system posture; S6, after completing the posture calibration of the grinding wheel (36) tool coordinate system, use two mechanical clamps (30) to clamp on the end face of the grinding wheel (36) together, at the same time, the limiting frame (34) is in contact with the edge of the grinding wheel (36), complete the formation of three-point fixation, and fix the position calibration device (200) on the grinding wheel (36); S7, start the grinding wheel (36) to rotate, and use the signal feedback of the electronic level (35) to control the rotation of the grinding wheel (36), that is, when the electronic level (35) shows level, lock the grinding wheel (36) to prevent it from rotating; S8, fix a light screen (40) on the ground, and make it located directly below the grinding wheel (36); S9, open the point light source (32), operate the robot, and make the light emitted by the robot converge to the ground light screen (40) to form point A after passing through the second convex lens (33), the focal length of the second convex lens (33) is s, that is, the distance from point A to the center of the second convex lens (33) is also s, since the tool coordinate system origin, the center of the second convex lens (33) and point A are located on the Z axis of the tool coordinate system, the distance from the tool coordinate system origin to the center of the second convex lens (33) is recorded as h, and the distance from the tool coordinate system origin to point A is recorded as d, that is, d=s+h; S10, set a point on the light screen (40) and record it as point B, operate the robot to make point A reach point B, then change the posture of the robot four times while keeping the position of point A unchanged, and record the six-axis joint rotation angle of the robot and the position of the robot end flange (37) coordinate system origin in the base coordinate system under the four postures; S11, use the least square method to establish a calibration equation, substitute the recorded position information each time into the calibration equation, calculate the coordinates of point A in the robot end flange coordinate system, calculate the position of the tool coordinate system origin through the fixed distance between point A and the tool coordinate system origin, and complete the calibration of the position of the robot tool coordinate system origin.

8. The method of claim 7, wherein: In S10, A point is made to reach point B in four different postures, and the rotation angles of the six-axis joints on the teach pendant and the position M of the origin of the coordinate system of the end flange (37) under the base coordinate system are recorded in sequence i and the rotation matrix, the following equation group is listed according to the position M i and the rotation matrix information In the formula: is the rotation matrix of the flange coordinate system to the base coordinate system, is the coordinate of point A in the flange coordinate system, is the coordinate of the origin of the flange coordinate system in the flange coordinate system, since point A is always located at the same position, so Therefore, the above four equations can be obtained by subtracting in turn: Solving the above linear equations by least square method or singular value decomposition method, the coordinates of point A in the coordinate system of the robot flange can be obtained

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