CN113858266B - Method and system for detecting pose errors of mechanical arm - Google Patents

Method and system for detecting pose errors of mechanical arm Download PDF

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Publication number
CN113858266B
CN113858266B CN202010622650.5A CN202010622650A CN113858266B CN 113858266 B CN113858266 B CN 113858266B CN 202010622650 A CN202010622650 A CN 202010622650A CN 113858266 B CN113858266 B CN 113858266B
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Prior art keywords
axis
mechanical arm
pose
camera
error
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CN113858266A (en
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徐洪亮
吕文尔
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Shanghai Minimally Invasive Digital Micro Medical Technology Co ltd
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Shanghai Minimally Invasive Digital Micro Medical Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
    • B25J19/0095—Means or methods for testing manipulators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/022—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by means of tv-camera scanning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/22—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring angles or tapers; for testing the alignment of axes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C1/00—Measuring angles

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Manipulator (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention provides a method and a system for detecting pose errors of a mechanical arm, wherein a calibration plate is arranged at the tail end of an actuator of the mechanical arm, a camera is arranged at the moving end of a test platform, and the mechanical arm and the camera are subjected to hand-eye calibration to obtain a pose conversion relation between the tail end of the actuator of the mechanical arm and the camera; the mechanical arm and the test platform are all moved to corresponding positions under the control of the information of the test positions; the camera shoots an original image of the calibration plate, and the pose error of the mechanical arm is obtained according to the size and the position of the image characteristic corresponding to the calibration plate in the original image. The invention replaces the manual change of the pose reached by the mechanical arm by using the test platform, so that a continuous and massive point location can be detected theoretically, the full-automatic measurement of the pose error of the whole measurement space point can be completed, and the synchronous detection of the position and the pose of the mechanical arm can be realized.

Description

Method and system for detecting pose errors of mechanical arm
Technical Field
The invention relates to the technical field of robots, in particular to a method and a system for detecting pose errors of a mechanical arm.
Background
With the rapid development of automation technology, the mechanical automation technology is gradually applied to various links of industrial production, and a mechanical arm, which is one of marks of mechanical automation, is one of main equipment for replacing manual work to transport, process and operate workpieces. In the application scenario, the positioning accuracy control of the mechanical arm motion is always a problem to be solved in an important way.
Because the number of the points which can be reached by the mechanical arm in the movement space is infinite in theory, the existing positioning precision detection device can only detect special points or limited points, and when a large number of points need to be detected, the workload is huge; in addition, because the point positions reached by the mechanical arm are manually changed, continuous and large-scale point position precision detection cannot be realized; moreover, the existing pose error detection device can only detect the position error of the mechanical arm and cannot detect the pose error of the mechanical arm.
Disclosure of Invention
The invention aims to provide a method and a system for detecting pose errors of a mechanical arm, which can automatically detect the pose errors of the mechanical arm and reduce the workload of testers.
In order to achieve the above object, the present invention provides a method for detecting a pose error of a mechanical arm, the method using a test platform, the test platform having a fixed end and a movable end, the movable end being movable relative to the fixed end, the method comprising:
The calibration plate is arranged at the tail end of an actuator of the mechanical arm, the camera is arranged at the moving end of the test platform, and the mechanical arm and the camera are subjected to hand-eye calibration to obtain a pose conversion relation between the tail end of the actuator of the mechanical arm and the camera;
the mechanical arm moves the calibration plate to a position indicated by a test position, and the test platform converts the test position information according to the position conversion relation so as to move the camera to the position indicated by the converted test position information; the method comprises the steps of,
the camera shoots an original image of the calibration plate, and the pose error of the mechanical arm is obtained according to the size and the position of the image characteristic corresponding to the calibration plate in the original image.
Optionally, the calibration board is provided with an alignment mark.
Optionally, a RST coordinate system is established with the center of the calibration plate as an origin, wherein the R axis and the S axis are in a plane where the calibration plate is located and are respectively along the transverse direction and the longitudinal direction of the calibration plate, the T axis is perpendicular to the plane where the calibration plate is located, and the pose error of the mechanical arm includes a position error translated along the R axis, the S axis and the T axis and a pose error rotated around the R axis, the S axis and the T axis.
Optionally, the step of obtaining the pose error of the mechanical arm according to the size and the position of the image feature includes:
acquiring the offset distances between the center of the image feature and the center of the original image along the R axis and the S axis, and acquiring the translational position errors of the mechanical arm along the R axis and the S axis according to the offset distances along the R axis and the S axis respectively;
constructing a right triangle by taking a diagonal line of the image feature as a hypotenuse, and acquiring the length L1 of the diagonal line of the right triangle, the lengths L2 and L3 of two right-angle sides, the distance M1 from the center of the image feature to the right-angle vertex of the right triangle and the distance M2 from the center of the image feature to the rest vertex of the right triangle, wherein the two right-angle sides with the lengths L2 and L3 are respectively parallel to an R axis and an S axis;
and according to L1, L2, L3, M1 and M2, obtaining the attitude errors of the mechanical arm rotating around the R axis, the S axis and the T axis.
Optionally, the distances between the center of the image feature and the center of the original image along the R axis and the S axis are positional errors of translation of the mechanical arm along the R axis and along the S axis, respectively.
Optionally, calculating the attitude error θ of the mechanical arm rotating around the R axis, the S axis, and the T axis according to the following formula 1 、θ 2 And theta 3 Wherein:
θ 3 ＝90°-θ 1 ；
l4 is the length of the diagonal line of the calibration plate, f is the focal length of the camera, and L5, L6, L7, L8 and omega are intermediate variables.
Optionally, the position error of the translation of the mechanical arm along the T axis is obtained according to the ratio of L4 to L1.
Optionally, the camera is a binocular camera, and the distance between the binocular camera and the calibration plate is obtained through the binocular camera, so that the position error of the mechanical arm translating along the T axis is obtained.
Optionally, the end of the actuator is further provided with a test tool, the test tool has a test tip located between the camera and the calibration plate, and the test tip is aligned with the center of the calibration plate.
The invention also provides a system for detecting the pose error of the mechanical arm, which comprises the following steps:
the tail end of the actuator of the mechanical arm is provided with a calibration plate;
the test platform is provided with a fixed end and a movable end, the movable end can move relative to the fixed end, a camera is arranged on the movable end, and a pose conversion relation between the end of an actuator of the mechanical arm and the camera is stored in the test platform; the method comprises the steps of,
the upper computer is in signal connection with the mechanical arm and the testing platform, and comprises a signal sending module and a pose error calculating module, wherein the signal sending module is used for sending testing pose information to the mechanical arm and the testing platform so that the mechanical arm and the camera can move to corresponding pose positions, and the pose error calculating module is used for obtaining an original image shot by the camera and obtaining pose errors of the mechanical arm according to the size and the position of the image characteristics of the corresponding calibration plate in the original image.
According to the method and the system for detecting the pose error of the mechanical arm, the test platform is utilized for detection, the calibration plate is arranged at the tail end of the actuator of the mechanical arm, the camera is arranged at the moving end of the test platform, and the mechanical arm and the camera are subjected to hand-eye calibration, so that the pose conversion relation between the tail end of the actuator of the mechanical arm and the camera is obtained; the mechanical arm and the test platform are all moved to corresponding positions under the control of the information of the test positions; the camera shoots the calibration plate to obtain an original image, and image characteristics corresponding to the calibration plate in the original image are extracted; and obtaining the pose error of the mechanical arm according to the size and the position of the image characteristic. According to the invention, the position and the posture of the mechanical arm are changed by using the test platform instead of manual work, so that a continuous and large number of point positions can be detected theoretically, full-automatic measurement of the position and the posture errors of the whole measurement space point can be completed, and the position and the posture of the mechanical arm can be synchronously detected.
Drawings
Fig. 1 is a schematic structural diagram of a device for detecting pose errors of a mechanical arm according to an embodiment of the present invention;
Fig. 2 is a schematic structural diagram of an attitude adjustment module according to an embodiment of the present invention;
fig. 3 is a flowchart of a method for detecting pose errors of a mechanical arm according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a system for detecting pose errors of a mechanical arm according to an embodiment of the present invention;
fig. 5 is another flowchart of a method for detecting a pose error of a mechanical arm according to an embodiment of the present invention;
fig. 6a to 6f are schematic diagrams of original images and image features of a mechanical arm captured under different pose errors according to an embodiment of the present invention;
FIG. 7 is a flowchart illustrating steps for obtaining a pose error of the mechanical arm according to the size and position of the image feature according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of calculating an attitude error of the mechanical arm rotating around an R axis, an S axis and a T axis according to an embodiment of the present invention;
wherein, the reference numerals are as follows:
100-chassis;
200-a pose adjusting mechanism; 210-a position adjustment module; 211-a first position adjustment unit; 212-a second position adjustment unit; 213-a third position adjustment unit; 220-an attitude adjustment module; 221-a first posture adjustment unit; 222-a second attitude adjustment unit; 223-a third posture adjustment unit;
300-camera;
400. 500-controllers;
600-upper computer;
700-mechanical arm; 701—an actuator end;
800-calibration plate;
001a, 001b, 001c, 001d, 001f, 001g, 001 h-original image; 002a, 002b, 002c, 002d, 002e, 002f, 002g, 002 h-image features;
a01, a02, b01, b02—side length of image feature 002 a; a11, a12, b11, b12—side length of image feature 002 b; a21, a22, b21, b22—side lengths of image features 002c and 002 d; a31, a32, b31, b32—side length of image feature 002 e; a41, a42, b41, b42—side length of image feature 002 f; a51, a52, b51, b52—side length of image feature 002 g; a61, a62, b61, b 62-side length of image feature 002 h; o (O) 1 -a center of the image feature; h-offset distance; α1, α2-included angle.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
Fig. 1 is a schematic structural diagram of a detection device for pose errors of a mechanical arm according to the present embodiment, fig. 2 is a schematic structural diagram of a pose adjustment module 220 according to the present embodiment, and, with reference to fig. 1 and fig. 2, the detection device for pose errors of a mechanical arm according to the present embodiment includes a chassis 100, a pose adjustment mechanism 200, a pose detection mechanism, a camera 300, and a controller 400.
With continued reference to fig. 1 and 2, in the present embodiment, the plane of the chassis 100 is taken as a reference system, the X-axis and the Y-axis are perpendicular to each other in the plane, and the Z-axis is perpendicular to the planes of the X-axis and the Y-axis. The camera 300 is disposed on the pose adjusting mechanism 200, and the pose adjusting mechanism 200 may drive the camera 300 to move in a plane formed by two directions of X direction, Y direction and Z direction and rotate around the X direction, Y direction and Z direction. In this embodiment, the pose adjustment mechanism 200 includes a position adjustment module 210 and a pose adjustment module 220, where the pose adjustment module 220 is disposed on the position adjustment module 210, and the pose adjustment module 220 can drive the camera 300 to move in planes formed by two directions of X, Y and Z directions, so as to implement translational degrees of freedom in three directions of X, Y and Z directions; the camera 300 is disposed on the gesture adjusting module 220, and the gesture adjusting module 220 may drive the camera 300 to rotate around the X direction, the Y direction and the Z direction, so as to realize rotational degrees of freedom around the X direction, the Y direction and the Z direction. That is, the position adjustment module 210 and the posture adjustment module 220 are respectively responsible for three degrees of freedom of movement, that is, the position adjustment module 210 is used to adjust the position of the camera 300 in space, and the posture adjustment module 220 is used to adjust the posture of the camera 300 in space, where the space refers to a space coordinate system established in the direction X, Y, Z in the present embodiment.
That is, the camera 300 moves in the spatial coordinate system formed by XYZ under the driving of the position adjustment module 210 and the posture adjustment module 220.
Specifically, the position adjustment module 210 includes a first position adjustment unit 211, a second position adjustment unit 212, and a third position adjustment unit 213. In this embodiment, the first position adjusting unit 211 is disposed on the chassis 100 and is rotatable on the chassis 100 around the Z direction. The second position adjusting unit 212 and the third position adjusting unit 213 each include a linear guide and a slider. The linear guide rail of the second position adjusting unit 212 is vertically disposed on the first position adjusting unit 211 along the Z direction and can synchronously rotate around the Z direction along with the rotation of the first position adjusting unit 211, and the slider of the second position adjusting unit 212 can move along the linear guide rail along the Z direction; the linear guide rail of the third position adjusting unit 213 is perpendicular to the linear guide rail of the second position adjusting unit 212, and the third position adjusting unit 213 may move along with the slider of the second position adjusting unit 212 along the Z direction, and the slider of the third position adjusting unit 213 may move along the X direction along the linear guide rail of the third position adjusting unit 213, and when the first position adjusting unit 211 drives the second position adjusting unit 212 to rotate synchronously, the slider of the third position adjusting unit 213 may move in the spatial coordinate system formed by XYZ. In this way, the first position adjusting unit 211 rotates around the Z direction, which is equivalent to driving the gesture adjusting module 220 to translate in the Y direction, the second position adjusting unit 212 and the third position adjusting unit 213 respectively drive the gesture adjusting module to translate in the Z direction and translate in the X direction, and the position adjusting module 210 can drive the gesture adjusting module 220 to translate in the X direction, the Y direction and the Z direction.
Further, as shown in fig. 2, the posture adjustment module 220 includes a first posture adjustment unit 221, a second posture adjustment unit 222, and a third posture adjustment unit 223. In this embodiment, the first posture adjustment unit 221 is disposed on the slider of the third position adjustment unit 213 and is movable along with the linear rail of the third position adjustment unit 213 (refer to fig. 1), and the first posture adjustment unit 221 is also rotatable about the Z-direction. The second posture adjustment unit 222 is provided on the first posture adjustment unit 221 and is rotatable around the Z-direction in synchronization with the rotation of the first posture adjustment unit 221, and the second posture adjustment unit 222 is also rotatable perpendicular to the Z-direction. The third posture adjustment unit 223 is provided on the second posture adjustment unit 222 and is rotatable around the Z-direction or around a direction perpendicular to the Z-direction in synchronization with the movement of the second posture adjustment unit 222, and the third posture adjustment unit 223 is also rotatable around the X-direction. The camera 300 is disposed on the third posture adjustment unit 223, so that the posture adjustment module 220 can drive the camera 300 to rotate around the X direction, the Y direction, and the Z direction.
As described above, the position adjustment module 210 and the posture adjustment module 220 may move synchronously, so as to adjust the posture of the camera 300, and may achieve uniform and continuous movement in the directions of the degrees of freedom of the X-direction, the Y-direction, the Z-direction translation and the rotation around the X-direction, the Y-direction, and the Z-direction, and the camera 300 may theoretically reach any point in the movement range of the posture adjustment mechanism 200 in any posture.
In the present embodiment, the first position adjusting unit 211 and the first posture adjusting unit 221 have the same structure and the same direction, for example, the first position adjusting unit 211 and the first posture adjusting unit 221 may be a rotating table, but the present invention is not limited thereto, and the structures of the first position adjusting unit 211 and the first posture adjusting unit 221 may be different, as long as the rotation about the Z direction can be achieved.
It should be understood that the second posture adjustment unit 222 and the third posture adjustment unit 223 may also be rotating tables, and are different from the first position adjustment unit 211 and the first posture adjustment unit 221 in the manner in which the second posture adjustment unit 222 and the third posture adjustment unit 223 are disposed, so that the second posture adjustment unit 222 and the third posture adjustment unit 223 have different rotation directions from the first position adjustment unit 211 and the first posture adjustment unit 221.
In this embodiment, the second position adjusting unit 212 and the third position adjusting unit 213 are lead screw slider rails, and the lead screw and the track in the lead screw slider rails can be small lead compact lead screw and high precision track respectively, so as to improve the moving precision.
In this embodiment, the first position adjusting unit 211, the second position adjusting unit 212, the third position adjusting unit 213, the first posture adjusting unit 221, the second posture adjusting unit 222, and the third posture adjusting unit 223 each include independent driving motors, and the controller 400 may control the position of the camera 300 in any degree of freedom by controlling each driving motor, so as to adjust the posture of the camera 300. That is, the motion in each degree of freedom is independently driven, thereby facilitating position detection and motion control in each degree of freedom.
Of course, the setting directions of the driving motors of the first position adjusting unit 211, the second position adjusting unit 212, the third position adjusting unit 213, the first posture adjusting unit 221, the second posture adjusting unit 222 and the third posture adjusting unit 223 may be designed according to actual requirements, and are not illustrated herein.
Further, the driving motors of the first position adjusting unit 211, the second position adjusting unit 212, the third position adjusting unit 213, the first posture adjusting unit 221, the second posture adjusting unit 222 and the third posture adjusting unit 223 are all gear motors, for example, a gear motor with a large reduction ratio can be adopted, so that the moving precision is further improved. Of course, the driving motor in the present invention is not limited to a gear motor, but may be other servo motors, and will not be illustrated here.
With continued reference to fig. 1 and 2, the pose detection mechanism includes two displacement detection units and four angle detection units, and the pose detection mechanism obtains the pose of the camera 300 by detecting the position of the pose adjustment mechanism 200 in each degree of freedom.
Specifically, the two displacement detection units are respectively disposed on the second position adjustment unit 212 and the third position adjustment unit 213, so as to measure the translation distance of the second position adjustment unit 212 and the third position adjustment unit 213; the four angle detection units are correspondingly arranged on the driving motors of the first position adjustment unit 211, the first posture adjustment unit 221, the second posture adjustment unit 222 and the third posture adjustment unit 223, so as to measure the rotation angles of the first position adjustment unit 211, the first posture adjustment unit 221, the second posture adjustment unit 222 and the third posture adjustment unit 223. In this way, the position of the camera 300 may be obtained according to the rotation angle of the first position adjusting unit 211 and the translation distance of the second position adjusting unit 212 and the third position adjusting unit 213, the pose of the camera 300 may be obtained according to the rotation angle of the first pose adjusting unit 221, the second pose adjusting unit 222 and the third pose adjusting unit 223, and the pose of the camera 300 may be obtained according to the detection information of the six sensors, so that the pose of the camera 300 obtained in real time may have extremely high precision.
In this embodiment, the displacement detection unit is a grating scale, the scale grating of the grating scale may be disposed on the tracks of the second position adjustment unit 212 and the third position adjustment unit 213, and the grating readhead of the grating scale may be disposed on the sliders of the second position adjustment unit 212 and the third position adjustment unit 213.
In this embodiment, the angle detecting unit is an encoder, and the encoder may be an encoder provided in the driving motor, or may be an independent encoder provided on an output shaft of the driving motor; the encoder may be an absolute encoder or a relative encoder, and should not be limited thereto.
It can be understood that the accuracy of pose detection can be improved by adopting a grating ruler and an encoder to detect the distance and the angle.
It should be understood that the displacement detecting unit and the angle detecting unit in the present invention are not limited to two or four, and other numbers can be designed according to the needs; the displacement detection unit and the angle detection unit are not limited to a grating ruler or an encoder, and can be other sensors capable of detecting distance and angle; the pose detection mechanism is not limited to the use of a displacement detection unit or an angle detection unit, as long as a sensor or a sensor combination that acquires a position in each degree of freedom can be realized.
Further, the pose detection mechanism feeds back the detection result to the controller 400, and the controller 400 controls the output of each driving motor according to the detection result by the pose detection mechanism until the camera 300 moves to the set pose. In this way, the present invention performs closed-loop control on the movement amount of the pose adjustment mechanism 200 by using the detection result of the pose detection mechanism, so that the movement accuracy of the pose adjustment mechanism 200 can be greatly improved, and the detection accuracy is further improved. Through experiments, the movement precision of the pose adjusting mechanism 200 in each degree of freedom can reach 0.01mm.
With continued reference to fig. 1 and fig. 2, in this embodiment, the apparatus for detecting a pose error of the mechanical arm further includes an upper computer, where the upper computer is in signal connection with the controller 400, so as to send a control signal to the controller 400, where the control signal includes pose information for indicating the set pose.After receiving the control signal, the controller 400 controls the output of each driving motor to move the camera 300 to the set pose. For example, the control signal is, for example, a coordinate signal (X 1 、Y 1 、Z 1 、RX 1 、RY 1 、RZ 1 ) After receiving the control signals, the controller 400 calculates the output quantity of each driving motor according to the control signals and controls the output of each driving motor, each driving motor starts to drive the pose adjusting mechanism 200 to move, and the camera 300 also starts to move synchronously. During the movement of the pose adjustment mechanism 200, the pose detection mechanism detects the pose of the camera 300 in real time, and when the pose of the camera 300 detected by the pose detection mechanism is (X 2 、Y 2 、Z 2 、RX 2 、RY 2 、RZ 2 ) When the camera 300 has not reached the set pose, the controller 400 determines whether the camera 300 is in the set pose (X 2 、Y 2 、Z 2 、RX 2 、RY 2 、RZ 2 ) The output of each driving motor is controlled until the pose detection mechanism detects that the pose of the camera 300 is (X) 1 、Y 1 、Z 1 、RX 1 、RY 1 、RZ 1 ) The camera 300 reaches the set pose.
Fig. 3 is a flowchart of a method for detecting a pose error of a mechanical arm according to the present embodiment. As shown in fig. 3, the method for detecting the pose error of the mechanical arm in this embodiment uses a test platform, where the test platform has a fixed end and a moving end, and the moving end can move relative to the fixed end, and the method for detecting the pose error of the mechanical arm includes:
Step S1: the calibration plate is arranged at the tail end of an actuator of the mechanical arm, the camera is arranged at the moving end of the test platform, and the mechanical arm and the camera are subjected to hand-eye calibration to obtain a pose conversion relation between the tail end of the actuator of the mechanical arm and the camera;
step S2: the mechanical arm moves the calibration plate to a position indicated by a test position, and the test platform converts the test position information according to the position conversion relation so as to move the camera to the position indicated by the converted test position information;
step S3: the camera shoots an original image of the calibration plate, and the pose error of the mechanical arm is obtained according to the size and the position of the image characteristic corresponding to the calibration plate in the original image.
The test platform in this embodiment may be the device for detecting the pose error of the mechanical arm shown in fig. 1 and 2, or may be another movable mechanism with the same degree of freedom as the mechanical arm, which is not limited by the present invention. Fig. 4 is a schematic diagram of the detection of the pose error of the mechanical arm by using the detection device of the pose error of the mechanical arm shown in fig. 1 and 2, and next, a method for detecting the pose error of the mechanical arm will be described in detail by taking the detection device of the pose error of the mechanical arm shown in fig. 1 and 2 as an example.
Fig. 5 is another flowchart of a method for detecting a pose error of a manipulator according to the present embodiment, and referring to fig. 4 and 5, a manipulator 700 is a manipulator to be detected for a pose error, and has an articulated arm and an actuator located at the end of the articulated arm, where the actuator includes an actuator end 701, the actuator end 701 may be a claw for fixing a tool, and the articulated arm of the manipulator 700 has 6 degrees of freedom in space. The detection device for the pose error of the mechanical arm is used as a test platform, the base of the detection device for the pose error of the mechanical arm is used as a fixed end of the test platform, the end part of the pose adjusting mechanism 200 is used as a moving end of the test platform, and the pose adjusting mechanism 200 is provided with a camera 300.
Further, the mechanical arm 700 and the device for detecting the pose error of the mechanical arm are respectively provided with controllers 500 and 400, and the controllers 500 and 400 are respectively used for controlling the movement of the joint arm of the mechanical arm 700 and the pose adjusting mechanism 200. The controllers 500, 400 are in signal connection with a host computer 600, so as to receive control signals from the host computer 600.
First, step S1 is performed, the calibration plate 800 is disposed on the actuator end 701 of the mechanical arm 700, and the actuator end 701 may drive the calibration plate 800 to move to the testing position. In this embodiment, the calibration plate 800 is a checkerboard calibration plate, and in other embodiments, the calibration plate 800 may be a solid circular array calibration plate.
In this embodiment, the calibration plate 800 has alignment marks, that is, two opposite angles of the calibration plate 800 have different patterns, so as to mark the direction of the calibration plate 800, thereby facilitating the subsequent determination of the direction of the pose error of the mechanical arm 700.
Further, the camera 300 on the pose adjusting mechanism 200 is used as a camera for hand-eye calibration and pose error detection.
Next, the manipulator 700 and the camera 300 are calibrated by hand and eye, so as to obtain a pose conversion relationship between the actuator end 701 of the manipulator 700 and the camera 300. Referring to fig. 4, for convenience of description, a RST coordinate system is established with the center of the calibration plate 800 as an origin, wherein R and S axes are in a plane in which the calibration plate 800 is located and are respectively along the transverse and longitudinal directions of the calibration plate 800 (i.e., the transverse and longitudinal directions of a checkerboard in the calibration plate 800), and a UVW coordinate system is established with the optical center of the camera 300 as an origin, wherein a W axis is along the optical axis direction of the camera 300, and U and V axes are in a plane perpendicular to the optical axis direction of the camera, and the optical center of the camera is also in the plane, i.e., the W axis is perpendicular to the UV plane. It will be appreciated that the RST coordinate system in this embodiment corresponds to the tool coordinate system (Tool Coordinate System, TCS), the UVW coordinate system corresponds to the workpiece coordinate system (Piece Coordinate System, PCS), and as shown in fig. 4, when the calibration plate 800 is aligned with the camera 300, the T axis and the W axis coincide, the R axis and the U axis are parallel, and the S axis and the V axis are parallel, and when the calibration plate 800 is moved with the camera 300, the positions of the origins and the directions of the coordinate axes of the RST coordinate system and the UVW coordinate system are continuously changed.
It will be appreciated that the RST coordinate system is obtained by a rotation and displacement change of the base coordinate system of the base of the mechanical arm 700, the UVW coordinate system is obtained by a rotation and displacement change of the base coordinate system of the base of the pose error detection device of the mechanical arm, and the relative pose between the base of the mechanical arm 700 and the base of the pose error detection device of the mechanical arm is fixed, so that the pose conversion relationship obtained by hand-eye calibration is a conversion relationship from the coordinate system (RST coordinate system) of the actuator end 701 of the mechanical arm 700 to the coordinate system (UVW coordinate system) of the camera 300, and this conversion relationship remains unchanged during the movement of the mechanical arm 700 and the camera 300.
In this embodiment, the hand-eye calibration of the mechanical arm 700 and the camera 300 is a typical "out-of-hand" calibration model, and the hand-eye calibration method is not described herein.
Next, step S2 is performed, where the actuator end 701 of the mechanical arm 700 and the pose adjustment mechanism 200 are moved to initial positions, where the initial position of the actuator end 701 of the mechanical arm 700 may be a specific point of the mechanical arm 700, and the initial position of the pose adjustment mechanism 200 is a position corresponding to the initial position of the actuator end 701 of the mechanical arm 700, and may be obtained by the hand-eye calibration.
Next, the upper computer 600 inputs a test pose information into the controllers 500, 400. In this embodiment, the test pose information is coordinate information of a test point of the mechanical arm 700, for example, the test pose information is used to indicate a pose (R 1 、S 1 、T 1 、RR 1 、RS 1 、RT 1 ). The controller 500 controls the articulated arm of the mechanical arm 700 to drive the calibration plate 800 to move to the pose (R 1 、S 1 、T 1 、RR 1 、RS 1 、RT 1 ) A place; the controller 400 converts the test pose information, and the converted test pose information indicates a pose (U 1 、V 1 、W 1 、RU 1 、RV 1 、RW 1 ) Then, the pose adjustment mechanism 200 is controlled to drive the camera 300 to move to the pose (U) 1 、V 1 、W 1 、RU 1 、RV 1 、RW 1 ) Where it is located. Ideally, when the calibration plate 800 moves to the pose indicated by the test pose information, the virtual connection line formed by the optical center of the camera 300 and the center of the calibration plate 800 is perpendicular to the plane where the calibration plate 800 is located when the camera 300 moves to the pose indicated by the converted test pose information.
In this embodiment, when the controller 400 controls the pose adjustment mechanism 200 to drive the camera 300 to move to the pose (U) 1 、V 1 、W 1 、RU 1 、RV 1 、RW 1 ) In the process, the controller 400 may also read the information detected by the pose detection mechanism of the pose error detection device of the mechanical arm in real time, so as to perform feedback adjustment on the motion of the camera 300 until the pose adjustment mechanism 200 reaches the corresponding pose. As can be seen, the controller 400 can accurately move the camera 300 to a pose (U) by closed-loop control 1 、V 1 、W 1 、RU 1 、RV 1 、RW 1 ) At this point, the accuracy of the movement of the posture adjustment mechanism 200 is improved.
Step S3 is performed, when the calibration plate 800 is moved to the position (R 1 、S 1 、T 1 、RR 1 、RS 1 、RT 1 ) At this point, and the camera 300 moves to a pose (U) 1 、V 1 、W 1 、RU 1 、RV 1 、RW 1 ) When the position is reached, the camera 300 shoots an original image of the calibration plate 800, and obtains the pose error of the mechanical arm 700 according to the size and the position of the image feature corresponding to the calibration plate in the original image.
Specifically, fig. 6a to 6f are schematic diagrams of the original image and the image features obtained by the camera 300 capturing the calibration plate 800, and then the pose error analysis of the mechanical arm 700 will be performed with reference to fig. 4 and fig. 6a to 6 f. For ease of comparison, an ideal calibration plate image and ideal image features are introduced herein to compare with the original image and the image features.
Fig. 6a is a schematic diagram of an original image 001a and an image feature 002a of the mechanical arm 700, which are taken under ideal conditions, as shown in fig. 6a, in which, ideally, the mechanical arm 700 has no pose error, when the camera 300 takes the calibration plate 800, the calibration plate 800 is opposite to the camera 300, and a virtual connection line between the center of the calibration plate 800 and the optical center of the camera 300 is perpendicular to a plane where the calibration plate 800 is located. As such, the image feature 002a of the original image 001a corresponding to the calibration plate 800 should be located at the exact center of the original image 001a (the center O of the image feature 002 a) 1 Coinciding with the center of the original image 001 a). At this time, the frame of the image feature 002a and the frame of the original image 001a form a zigzag shape, the corresponding directions of the grid lines of the image feature 002a in the lateral direction and the longitudinal direction of the original image 001a are parallel, the original image 001a is the ideal calibration plate image, the image feature 002a is the ideal image feature, and the four sides of the image feature 002a are a01, a02, a03 and a04.
It should be understood that the image feature 002a is an ideal checkerboard image corresponding to the pose conversion relationship. Specifically, the four side lengths a01, a02, a03, a04 of the image feature 002a are obtained by scaling the four side lengths of the calibration plate 800 in equal proportion, and in the hand-eye calibration stage, the pose conversion relationship is obtained, and then equal-proportion scaling multiple corresponding to the pose conversion relationship can be obtained. In this way, the image feature 002a may not be obtained through actual shooting, the chess board image may be scaled to obtain the image feature 002a, and the four side lengths a01, a02, a03, a04 of the image feature 002a may also be accurately obtained.
Further, when the robot arm 700 has a pose error, there are several cases as follows:
1) FIG. 6b shows the original image 001b captured by the manipulator 700 with a position error translated forward along the R-axisSchematic representation of image feature 002 b. As shown in fig. 6b, when the mechanical arm 700 has a position error of forward translation along the R axis, the center O of the image feature 002b is based on the image feature 002a in fig. 6a 1 Not coincident with the center of the original image 001b, but having an offset distance H along the negative R-axis with respect to the center of the original image 001 b. At this time, the lateral direction and the longitudinal direction of the original image 001b are parallel to the corresponding directions of the grid lines of the image feature 002b, the side lengths a11, a12, b11, b12 of the image feature 002b are equal to the side lengths a01, a02, b01, b02 of the image feature 002a, and the offset distance H is a position error of the mechanical arm 700 translating forward along the R axis. Positional errors of translation along the S-axis and positional errors of negative translation along the R-axis are similarly available.
2) Fig. 6c is a schematic diagram of the original images 001c and 001d and the image features 002c and 002d captured when the mechanical arm 700 has an attitude error of rotating counterclockwise around the T axis and an attitude error of rotating clockwise around the T axis. As shown in fig. 6c, when the robot arm 700 has an attitude error of rotating counterclockwise around the T axis or an attitude error of rotating clockwise around the T axis, on the basis of the image feature 002a in fig. 6a, the image features 002c, 002d are centered around the center O thereof on the plane of the original images 001c, 001d 1 Rotated by an angle alpha 1, alpha 2 clockwise and counter clockwise, respectively. At this time, centers O of the image features 002c, 002d 1 And the grid lines of the image features 002c and 002d are respectively overlapped with the centers of the original images 001c and 001d, are respectively not parallel to the transverse direction and the longitudinal direction of the original images 001c and 001d, and the side lengths a21, a22, b21 and b22 of the image features 002c and 002d are equal to the side lengths a01, a02, b01 and b02 of the image features 002 a. An included angle between the lateral direction of the original image 001c and the lateral direction of the grid line of the image feature 002c is α1, an included angle between the lateral direction of the original image 001d and the lateral direction of the grid line of the image feature 002d is α2, and the included angles α1 and α2 are respectively an attitude error of the mechanical arm 700 along a counterclockwise rotation around the T axis and an attitude error along a clockwise rotation around the T axis. The posture error of clockwise rotation around the T axis and the posture error of anticlockwise rotation around the T axis are obtained in the same way。
3) Fig. 6d is a schematic diagram of the original images 001e and 001f and the image features 002e and 002f captured when the mechanical arm 700 has an attitude error of rotating counterclockwise around the R axis (seen from the direction along the S axis) and an attitude error of rotating clockwise around the S axis (seen from the direction along the R axis). As shown in fig. 6d, when the robot arm 700 has an attitude error of rotating around the R axis or the S axis, the image features 002e, 002f are distorted into a trapezoid on the basis of the image feature 002a in fig. 6 a. At this time, centers O of the image features 002e and 002f 1 Coinciding with the centers of the original images 001e and 001f, the side lengths b31 and b32 of the image feature 002e are equal to the side lengths b01 and b02 of the image feature 002a, the side lengths a31 and a32 of the image feature 002e are unequal to the side lengths a01 and a02 of the image feature 002a, the side lengths b41 and b42 of the image feature 002f are unequal to the side lengths b01 and b02 of the image feature 002a, the side lengths a41 and a42 of the image feature 002e are equal to the side lengths a01 and a02 of the image feature 002a, the transverse direction or longitudinal direction of the original image 001e is not parallel to the corresponding directions of the grid lines of the image feature 001e, and the transverse direction or longitudinal direction of the original image 001f is not parallel to the corresponding directions of the grid lines of the image feature 002 f. Since the board-fixing board 800 is rectangular, the image feature 002a should be rectangular, but when the robot arm 700 has an attitude error of rotating around the R-axis or the S-axis, the distance between the opposite side of the board-fixing board 800 and the camera 300 is changed, resulting in that the image feature of the photographed board 800 is distorted, and the side of the board-fixing board 800 close to the camera 300 is embodied as an increased side length in the image feature, and the side of the board-fixing board 800 far from the camera 300 is embodied as a decreased side length in the image feature, whereby the attitude error of rotating the robot arm 700 counterclockwise around the R-axis and the attitude error of rotating clockwise around the S-axis can be obtained by the ratio of the two opposite sides of the image features 002e, 002 f. The same applies to the attitude error of clockwise rotation around the R axis or the attitude error of counterclockwise rotation around the S axis.
4) FIG. 6e shows the manipulator 700 with an attitude error (seen in the direction along the S-axis) of counter-clockwise rotation about the R-axis and with a clockwise rotation about the S-axisSchematic diagram of the original image 001g and image feature 002g taken when the needle rotates in the posture error (seen from the direction along the R axis). As shown in fig. 6e, when the robot arm 700 has an attitude error of rotating around the R axis and around the S axis at the same time, the image feature 002g is distorted into a trapezoid (the sides of the four sides of the image feature 002g are not equal) on the basis of the image feature 002a in fig. 6 a. Center O of the image feature 002g 1 The side lengths a51, a52, b51, b52 of the image feature 002g are not equal to the side lengths a01, a02, b01, b02 of the image feature 002a, and the lateral direction or the longitudinal direction of the original image 001g is not parallel to the corresponding direction of the grid line of the image feature 002g, and at this time, the attitude error of the mechanical arm 700 rotating anticlockwise around the R axis and the attitude error of the mechanical arm 700 rotating clockwise around the S axis can be obtained through the ratio of the two opposite side lengths of the image feature 001 g. The same applies to the attitude error of clockwise rotation around the R axis and the attitude error of counterclockwise rotation around the S axis.
5) Fig. 6f is a schematic diagram of the original image 001h and the image feature 002h captured when the mechanical arm 700 has a position error translating in the negative direction of the T-axis. As shown in fig. 6f, when there is a positional error in the negative translation of the manipulator 700 along the T-axis, the image feature 002h is scaled down equally on the basis of the image feature 002a in fig. 6 a. At this time, the center O of the image feature 002h 1 Coinciding with the center of the original image 001h, the side lengths a61, a62, b61, b62 of the image feature 002h are not equal to the side lengths a01, a02, b01, b02 of the image feature 002g, but the side lengths a61, a62, b61, b62 of the image feature 002h can be obtained by scaling the side lengths a01, a02, b01, b02 of the image feature 002g in equal proportion, the transverse direction and the longitudinal direction of the original image 001h are parallel to the corresponding directions of the grid lines of the image feature 002h, and the position error of the robotic arm 700 in negative translation along the T axis can be obtained by comparing the side lengths a61, a62, b61, b62 of the image feature 002h with the side lengths a01, a02, b01, b02 of the image feature 002 g. The positional error of the forward translation along the T-axis is similarly available.
6) Combinations of at least two of the above pose errors, for example, a pose error of rotation around the T-axis and a position error of translation along the R-axis or along the S-axis, or a position error of translation along the T-axis and a position error of translation along the R-axis or along the S-axis, or a pose error of rotation around the R-axis or S-axis and a position error of translation along the R-axis or along the S-axis, etc., are not illustrated herein.
Based on this, please continue to refer to fig. 4, the mechanical arm 700 may cause the image features in the original image to change corresponding to the above 6 cases when the pose error is generated.
It should be appreciated that, since the calibration plate 800 is provided with alignment marks, the alignment marks may indicate the directions of the image features, so that the directions of the attitude errors may be accurately obtained. In this embodiment, the calibration plate 800 is square (with equal sides), and in other embodiments, the calibration plate 800 may be rectangular (with equal sides).
As an alternative embodiment, a test tool may be further disposed on the actuator end 701 of the robot arm 700, the test tool having a test tip located between the camera 300 and the calibration plate 800, and the test tip being aligned with the center of the calibration plate 800. In this way, when the camera 300 shoots the calibration plate 800, the test tip of the test tool is shot, the original image and the image feature have features corresponding to the test tip, and after the test tip is aligned to the center of the calibration plate 800 and the original image is shot, the test tip on the image feature is also aligned to the center of the calibration plate, so that the center of the image feature is more obvious, and it is convenient to determine whether the center of the image feature coincides with the center of the original image.
Fig. 7 is a flowchart of the steps for obtaining the pose error of the mechanical arm according to the size and the position of the image feature provided in the present embodiment, and how to obtain the pose error of the mechanical arm 700 according to the image feature will be described in detail with reference to fig. 4 and fig. 7.
Step S31 is executed, wherein the offset distance of the center of the image feature relative to the center of the original image along the R axis and the S axis is obtained, and if the center of the image feature coincides with the center of the original image (the offset distances along the R axis and the S axis are 0), the image feature has no position error translating along the R axis and along the S axis; if the image feature translates a certain distance along the R axis and/or along the S axis, the offset distance of the image feature along the R axis and the S axis is a positional error of the translation of the mechanical arm 700 along the R axis and the S axis. Further, the direction of the positional error of the mechanical arm 700 along the R-axis and the S-axis translation can be obtained according to the direction of the image feature along the R-axis and the S-axis translation.
Next, the error of the rotation of the robot 700 along the R, S, and T axes needs to be obtained. Fig. 8 is a schematic diagram of acquiring errors of rotation of the mechanical arm 700 along the R-axis, the S-axis, and the T-axis according to the present embodiment. Referring to fig. 4 and fig. 8, Q is the optical center point of the camera 300, AB is the diagonal line of the calibration board in an ideal case, BC is the diagonal line of the calibration board 800 obtained by rotating the mechanical arm 700 along the R-axis, the S-axis and the T-axis by a certain angle, a ' B ' and B ' C ' are the images obtained by projecting AB and BC onto the image plane of the camera 300, respectively (a ' B ' and B ' C ' are the diagonal line of the ideal calibration board image and the diagonal line of the actual image feature, respectively), and Q ' is the projection point of Q onto the image plane (i.e. the center in the original image). Making auxiliary lines B 'D', D 'F', A 'D', C 'F', D 'F', Q 'F', A 'Q' according to A 'B' and B 'C' on an image plane, wherein B 'D' and D 'F' are collinear and parallel to an S axis, A 'D' and C 'F' are parallel to an R axis, and < QQ 'F' and < QF 'C' are right angles; an auxiliary line BD, AD, DE, EC, BF, CF is made at the object plane according to AB and BC, where BD and DE are collinear and both parallel to the S axis, < DEC is a right angle.
It can be understood that the errors of the rotation of the mechanical arm 700 along the R axis, the S axis and the T axis are the attitude errors of AB and BC, as can be obtained according to fig. 8, the attitude error of the mechanical arm 700 along the R axis is γ, the attitude error along the S axis is the complementary angle of β, and the attitude error along the T axis is the complementary angle of γ, so that the errors of the rotation of the mechanical arm 700 along the R axis, the S axis and the T axis can be obtained only by obtaining β and γ.
Next, in ΔQQ 'F',in ΔQQ' C, -A-> In ΔQQ 'B', ∈>Since Δqb ' C ' is similar to Δqbc, QB '/qb=b ' C '/BC, and since Δqb ' F ' is similar to Δqbe, be= (bc·b ' F ')/B ' C ' can BE derived from B ' F '; since Δqc 'F' is similar to Δ QCF, cf= (bc·c 'F')/B 'C' can be obtained from C 'F'.
According to the rule in the deltabec,<the BEC is a right angle at which,
according to QF ', QC' and C 'F', the delta QF 'C' can be obtained through cosine theorem<QF 'C', i.e. QFSince Δqf 'C' is similar to Δqfc,<QF’C’＝<EFC. According to the sine theorem, EC/sin<EFC＝CF/sin<CEF, available->γ＝180°-<EFC-<CEF。
Based on this, step S32 is executed, where the diagonal line of the image feature is a hypotenuse to construct a right triangle, and the length L1 of the diagonal line of the right triangle, the lengths L2 and L3 of the two right-angle sides, the distance M1 from the center of the image feature to the right-angle vertex of the right triangle, and the distance M2 from the center of the image feature to the remaining vertex of the right triangle are obtained, where the two right-angle sides with lengths L2 and L3 are parallel to the R axis and the S axis, respectively. It can be understood that the right triangle is Δb ' F ' C ', and the pose error of the mechanical arm 700 rotating around the R axis, the S axis and the T axis can be obtained according to L1, L2, L3, M1, M2.
Step S33 is performed, l2=c 'F', l3=b 'F', l4=ab=bc, l5=be, l6=cf, l7=qf ', l8=qc', ω=<EFC, M1=Q ' F ', M2=Q ' C ', QQ ' is the focal length F of the camera, and the pose error theta of the mechanical arm rotating around the R axis, the S axis and the T axis can be calculated according to the following formula 1 、θ 2 And theta 3 Wherein, the method comprises the steps of, wherein,
θ 3 ＝90°-θ 1 ；
in the above formula, L5, L6, L7, L8, ω are all intermediate variables, and may not represent actual meanings, and then step S34 is performed to obtain the positional error of the translation of the manipulator 700 along the T-axis according to the ratio of L4 to L1.
It will be appreciated that, ideally, the ratio of L4 to L1 is a set point, and when the manipulator 700 has a positional error of translation along the T-axis, the ratio of L4 to L1 is changed, so that the positional error of translation of the manipulator 700 along the T-axis can be calculated from the ratio of L4 to L1.
Further, when the camera 300 is a binocular camera, the binocular camera may directly measure the distance from the calibration plate 800. Since the distance between the camera 300 and the calibration plate 800 is already obtained in the hand-eye calibration stage, the position error of the translation of the mechanical arm 700 along the T-axis can be directly obtained through the detection result of the binocular camera. Of course, when the camera 300 is a binocular camera, the pose of any line in the image feature may be measured by using the binocular camera, so as to obtain the difference between the position and the pose of the line and the corresponding line on the calibration board 800, which is the pose error of the mechanical arm 700.
In this way, the positional errors of the translation of the mechanical arm 700 along the R axis, the S axis, and the T axis and the attitude errors of the rotation around the R axis, the S axis, and the T axis can be obtained by executing steps S31 to S34. And repeating the steps until all the points to be tested of the mechanical arm 700 are tested, obtaining the pose error of the mechanical arm 700 on each point, storing the error to an upper computer after the test is completed, calculating Gaussian distribution and spectrum analysis of the pose error of the mechanical arm 700, and outputting an error analysis report so as to be convenient for operators to check. Further, a pose error database of the mechanical arm 700 may also be generated, so as to facilitate subsequent queries.
Based on this, as shown in fig. 4, the present embodiment further provides a system for detecting a pose error of a mechanical arm, including:
a robot arm 700, the actuator end 701 of which is provided with a calibration plate 800;
the test platform is provided with a fixed end and a movable end, the movable end can move relative to the fixed end, the movable end is provided with a camera 300, and the pose conversion relation between the end 701 of the actuator of the mechanical arm 700 and the camera 300 is stored in the test platform;
The upper computer 600 is in signal connection with the mechanical arm 700 and the test platform, and comprises a signal sending module and a pose error calculating module, wherein the signal sending module is used for sending test pose information to the mechanical arm 700 and the test platform so that the mechanical arm 700 and the camera 300 can move to corresponding poses, and the pose error calculating module is used for obtaining an original image shot by the camera 300 and obtaining the pose error of the mechanical arm 700 according to the size and the position of the image feature corresponding to the calibration plate 800 in the original image.
In this embodiment, the test platform may be a device for detecting pose errors of the mechanical arm as shown in fig. 1-2, or may be other movable detection mechanisms, which is not limited by the present invention.
In summary, the method and the system for detecting the pose error of the mechanical arm utilize a test platform to detect, firstly, a calibration plate is arranged at the tail end of an actuator of the mechanical arm, a camera is arranged at the moving end of the test platform, and the mechanical arm and the camera are subjected to hand-eye calibration, so that the pose conversion relation between the tail end of the actuator of the mechanical arm and the camera is obtained; the mechanical arm and the test platform are all moved to corresponding positions under the control of the information of the test positions; the camera shoots an original image of the calibration plate, and the pose error of the mechanical arm is obtained according to the size and the position of the image characteristic corresponding to the calibration plate in the original image. The invention replaces the manual change of the pose reached by the mechanical arm by using the test platform, so that a continuous and massive point location can be detected theoretically, the full-automatic measurement of the pose error of the whole measurement space point can be completed, and the synchronous detection of the position and the pose of the mechanical arm can be realized.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art will make any equivalent substitution or modification to the technical solution and technical content disclosed in the invention without departing from the scope of the technical solution of the invention, and the technical solution of the invention is not departing from the scope of the invention.

Claims (10)

1. The utility model provides a detection method of gesture error of arm, utilizes a test platform to detect, test platform has stiff end and removal end, the removal end can be relative the stiff end is removed, characterized in that includes:
the calibration plate is arranged at the tail end of an actuator of the mechanical arm, the camera is arranged at the moving end of the test platform, and the mechanical arm and the camera are subjected to hand-eye calibration to obtain a pose conversion relation between the tail end of the actuator of the mechanical arm and the camera;
the mechanical arm moves the calibration plate to a position indicated by a test position, and the test platform converts the test position information according to the position conversion relation so as to move the camera to the position indicated by the converted test position information; the method comprises the steps of,
The camera shoots an original image of the calibration plate, and the pose error of the mechanical arm is obtained according to the size and the position of the image characteristic corresponding to the calibration plate in the original image.
2. The method for detecting the pose error of the mechanical arm according to claim 1, wherein the calibration plate is provided with an alignment mark.
3. The method for detecting the pose error of the mechanical arm according to claim 2, wherein a RST coordinate system is established by taking the center of the calibration plate as an origin, wherein an R axis and an S axis are in a plane where the calibration plate is located and are respectively along the transverse direction and the longitudinal direction of the calibration plate, and a T axis is perpendicular to the plane where the calibration plate is located, and the pose error of the mechanical arm comprises a position error translated along the R axis, the S axis and the T axis and a pose error rotated around the R axis, the S axis and the T axis.
4. The method for detecting the pose error of the mechanical arm according to claim 3, wherein the step of obtaining the pose error of the mechanical arm according to the size and the position of the image feature comprises:
acquiring the offset distances between the center of the image feature and the center of the original image along the R axis and the S axis, and acquiring the translational position errors of the mechanical arm along the R axis and the S axis according to the offset distances along the R axis and the S axis respectively;
Constructing a right triangle by taking a diagonal line of the image feature as a hypotenuse, and acquiring the length L1 of the diagonal line of the right triangle, the lengths L2 and L3 of two right-angle sides, the distance M1 from the center of the image feature to the right-angle vertex of the right triangle and the distance M2 from the center of the image feature to the rest vertex of the right triangle, wherein the two right-angle sides with the lengths L2 and L3 are respectively parallel to an R axis and an S axis;
and obtaining the pose errors of the mechanical arm rotating around the R axis, the S axis and the T axis according to the L1, the L2, the L3, the M1 and the M2.
5. The method for detecting the pose error of the mechanical arm according to claim 4, wherein the distances between the center of the image feature and the center of the original image along the R axis and the S axis are the positional errors of the mechanical arm translating along the R axis and along the S axis, respectively.
6. The method for detecting a pose error of a robot arm according to claim 4, wherein a pose error θ of the robot arm rotating around an R-axis, an S-axis, and a T-axis is calculated according to the following formula 1 、θ 2 And theta 3 Wherein:
θ 3 ＝90°-θ 1 ；
l4 is the length of the diagonal line of the calibration plate, f is the focal length of the camera, and L5, L6, L7, L8 and omega are intermediate variables.
7. The method for detecting the pose error of the mechanical arm according to claim 6, wherein the position error of the mechanical arm translating along the T-axis is obtained according to a ratio of L4 to L1.
8. The method for detecting the pose error of the mechanical arm according to claim 3, wherein the camera is a binocular camera, and the distance between the binocular camera and the calibration plate is obtained through the binocular camera, so that the position error of the mechanical arm translating along the T axis is obtained.
9. The method of claim 1, wherein the actuator tip is further provided with a test tool having a test tip positioned between the camera and the calibration plate, and wherein the test tip is aligned with the center of the calibration plate.
10. The utility model provides a detection system of position appearance error of arm which characterized in that includes:
the tail end of the actuator of the mechanical arm is provided with a calibration plate;
the test platform is provided with a fixed end and a movable end, the movable end can move relative to the fixed end, a camera is arranged on the movable end, and a pose conversion relation between the end of an actuator of the mechanical arm and the camera is stored in the test platform; the method comprises the steps of,
The upper computer is in signal connection with the mechanical arm and the testing platform, and comprises a signal sending module and a pose error calculating module, wherein the signal sending module is used for sending testing pose information to the mechanical arm and the testing platform so that the mechanical arm and the camera can move to corresponding pose positions, and the pose error calculating module is used for obtaining an original image shot by the camera and obtaining pose errors of the mechanical arm according to the size and the position of the image characteristics of the corresponding calibration plate in the original image.
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