JPS59178310A - Position aligning apparatus for calibrating coordinates system of multi-joint robot - Google Patents

Abstract

PURPOSE:To simply and certainly obtain data required in a coordinates system calibrating method, by constituting a leaf spring assembly for detecting the displacement of a contact element in X, Y and Z directions respectively crossing at right angles from parallel leaf springs for detecting the displacement in the X-direction, parallel leaf springs for detecting the displacement in the Y-direction and a cross spring for detecting the displacement in the Z-direction. CONSTITUTION:A leaf spring assembly 8 is constituted of a pair of parallel leaf springs 10 for detecting displacement in an X-direction which have flat surface parts arranged vertically to the X-direction and is displaceable to said X-direction, a pair of parallel leaf spring 11 for detecting displacement in a Y-direction which have flat surface parts arranged vertically to the Y-direction and is displaceable to the Y-direction and a cross spring 9 for detecting displacement in a Z-direction which has a flat surface part arranged vertically to the Z-direction and is displaceable to the Z-direction. A spherical contact element 12 is fixed to the central part of the cross spring 9 through a rigid support rod 8 and inserted into the conical hole 17 of a reference plate 7 when data is measured. By moving the conical hole 17 so as to always bring the contact element 12 with the conical hole 17 even if the position and the angle of the reference plate 17 are changed in order to bring the contact element 12 made spherical into engagement with the conical hole, the detection of a central position is enabled. In addition, a strain gauge is adhered to each leaf spring.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an articulated robot, and particularly to an alignment device for calibrating a coordinate system of a robot arm.

(2) Background of the technology Industrial robots have been used in a wide range of tasks such as welding, painting, and assembly, and recently, particularly high precision has been required for their operations. The precision required of a robot is the repeatability of a previously taught position (return accuracy: the position and orientation of the robot tip is taught by actually moving it using manual control, and the positioning at that position is attempted a total number of times. This increases the positioning accuracy (absolute accuracy: the difference between the commanded position and orientation of the robot tip and the position and orientation actually reached by the robot) in the absolutely fixed coordinate system defined for the robot. In a teaching/reproducing type robot, a high degree of repetition accuracy is required because the robot is moved to a predetermined position and the position is taught, but absolute accuracy is not required. but,
When you want a robot to perform tasks that are programmed using the Rosetsu language or created using a robot simulator,
Alternatively, absolute precision is required in addition to repeated farts in cases where the object is handled by mouth based on position data of an object detected by a visual recognition device using a TV right camera.

An articulated robot is composed of a plurality of joint units capable of rotating and bending movements. When controlling an articulated robot on a total absolute coordinate system as in the above-described work, calculations are performed to convert the position and orientation of the tip into desired joint angles. This conversion formula includes the length of each arm and the rotation angle of each joint from the joint origin as a cerameter. here,
During the machining of component parts during robot manufacturing, the length of the arm has a deviation from the design value. Also, when assembling one bit, errors occur in the installation of each joint. Therefore, even if the robot is fully controlled using the joint origin and arm length at the time of design, the desired movement cannot be achieved with respect to the command value. As a way to improve all the drawbacks, it is possible to manufacture the arm accurately by increasing the processing precision, and sometimes to adjust the attachment of each joint accurately, but this would inevitably increase the cost.

In view of these shortcomings, the applicant proposed a method for calibrating the rosette arm coordinate system that determines the arm length deviation and the installation of each joint after robot assembly is completed, and determines the arm's English dimensions and the actual origin of each joint. It has been proposed (patent application 1982)
-43778 and Japanese Patent Application No. 57-43779).

In the coordinate system calibration method shown in Japanese Patent Application No. 57-43778, the posture of the arm is changed with the arm tip positioned at one point, and the rotation angle of each joint unit in each posture is calculated when the arm is positioned in multiple postures. Data on position or bending angle position is required.

The coordinate system calibration method shown in Japanese Patent Application No. 57-43778 requires data on the rotation angle position or bending angle position of each joint unit at each position and posture when the arm tip is positioned at multiple points. .

(3) Object of the Invention The object of the present invention is to provide an alignment device for coordinate system calibration that can easily and reliably obtain the data necessary for the above-mentioned method of calibrating the coordinate system of an articulated robot.

(4) Achievements 1 and 3 of the invention In order to achieve all of the above objects, in the case of an IJ that does not fire, there is a contact element that contacts the needle at the reference position of the tip of the rosette arm to be calibrated, and a The plate spring assembly has a parallel plate spring for displacing in the X direction arranged perpendicularly to the plane part < Position for coordinate system calibration of an articulated robot configured with a parallel plate spring for Y-direction displacement detection and a cross spring for two-direction degree detection, which is arranged perpendicular to the X direction on the entire plane part and has the above-mentioned contact fully fixed in the center. Provide a matching device.

(5) Embodiment of the Invention The multi-jointed robot (30) has a first joint unit (1) capable of rotational movement in the direction of arrow A, and a second joint unit) capable of bending movement in the direction of arrow B.
A joint unit 2, a third joint unit 3 capable of bending movement in the direction of arrow C, a fourth joint unit 4 capable of rotational movement in the direction of arrow A, and a fifth joint unit 5 capable of bending movement in the direction of arrow E. , and a sixth joint unit 6 which is rotatably movable in the direction of arrow Y, and at the tip of the sixth joint unit 6 is a reference plate 7 for obtaining coordinate system calibration data according to the present invention. It is mounted rotatably in the direction of arrow Y.

A conical hole 17 is formed in the center of the reference plate 7. A positioning device for detecting the entire displacement of the center position of the conical hole 17 of the reference plate 7 and acquiring calibration data is constituted by the temporary spring assembly 8. This leaf spring assembly 8 has a flat σfj portion (i
= A pair of facing parallel plate springs 10 for displacing in the X direction and capable of displacing i+J in the X direction, and a flat part i
A pair of facing parallel plate springs 11 for detecting Y-direction displacement arranged perpendicularly to the Y direction and movable in the Y direction, and a two-direction degree 2λ output whose flat parts are arranged perpendicular to two directions and movable in two directions. It is constituted by a cross spring 9 for use. A spherical contact 12 is fixed to the center of the cross spring 9 via a rigid support shaft 8. When measuring data, this contactor 12 is inserted into the reference plate 170 and the conical hole 17 as shown in FIG. In this way, since the contact 12 is made spherical and is engaged in the conical hole, the conical hole 17 is fixed so that the contact 12 is always brought into contact with the conical hole 17 even if the position and angle of the reference plate 17 change. By moving it, the center position can be detected. A strain r-no 13 is attached to each leaf spring of the leaf spring assembly 8 to detect strain corresponding to the displacement of the leaf spring. Since the leaf spring assembly is displaced independently in the x, y, and z directions, and strains in each direction do not affect each other, accurate displacement positions in each direction can be detected. For example, as shown in FIG. 3, the strain gauge is attached to one of the parallel springs 10 so that the strain on the (+) side and the strain on the (-) side of each leaf spring can be detected simultaneously. 2 on the outer surface
Two strain gauges 13c, 13d' (z
Similarly, strain gauges are attached to both outer surfaces of the parallel spring 11, and two strain gauges 1 are attached to the upper surface of the cross spring 9.
9a and 19c are attached, and two strain gauges 19 are attached to the bottom surface.
b, Paste all 19d. At this time, it is desirable to provide each strain gauge at a position where the amount of strain is maximum, that is, near the center of the cross spring 9 and at the upper or lower edge of the parallel spring. Distortion r-) The number of sheets to be pasted may be further increased to improve measurement accuracy. Further, a strain cage may also be attached to the inner surface of each parallel leaf spring. Strain gauge 1 for parallel spring 10: 3a, 1'
3b.

13c and 7.3d constitute a bridge circuit shown in FIG. 4, so that an input voltage is applied from the terminal 21 and an output voltage corresponding to the displacement in the X direction is obtained from the terminal 20.

The output voltage corresponding to the displacement in the Y direction is also obtained in the same manner.

Distortion rr19a of cross spring 9.

19b, 19c, and 19d form the Blitzo circuit shown in FIG. 5, so that an input voltage is applied from the terminal 21 and an output Bt and pressure corresponding to the displacement in the 6z direction are obtained from the terminal 20. Each strain gauge is connected to a strain detection circuit 14 (FIG. 1) consisting of such a bridge circuit, and connected to an oscilloscope 16 via an amplifier 15, so that the output is displayed.

Calibration data measurement is performed as follows. First, the positions of the contacts 12 are determined in advance @fX, Y.

The robot arm is fully driven by specifying the two coordinate systems, and the conical hole 17 is aligned with the position of the contact 12 so that the contact 12 enters the conical hole 17 of the reference plate 7 at the tip of the arm. In this state, deviations in the arm length, errors in the joint origin, etc.
The leaf spring assembly 8 is distorted because it is not completely aligned at the position of the ri contact. Next, while observing the output of the strain gauge attached to the leaf spring assembly 8 with an Onroscog, the opening is adjusted to the at arm 21 so that the output of the strain gauge in each of the x, y, and z displacement directions becomes zero.
M moves. The robot arm is fully grooved when the displacement in the X, Y, and Z directions is zero. Second. Third. 4th゜5th
．． The rotation angle positions and bending angle positions of the sixth joint units 1, 2, 3, 4, 5.6 are detected from rotary encoders (not shown) provided at each joint, and calibration data is obtained. Next, the υ robot arm is fully driven using a command value that changes only the posture of the arm without changing the position of the conical hole in the reference plate at the tip of the arm.

If the posture is sloppy, the conical hole will be displaced again due to a deviation in the arm length, an error in the joint origin, etc., and the leaf spring assembly 8 will be distorted. I'll have to observe it with this distorted sound oscilloscope.

The robot arm is fully driven so that the displacement in the Y and Z directions becomes zero, and the above calibration data is obtained in a state where the displacement becomes zero. Is this the fi 611 position with the mouth open? Repeat this several times to obtain the required number of coordinate system calibration data.

The data when using the calibration data obtained with the entire tip of the arm moved by a predetermined distance in the seat head system calibration method is shown in the sixth column.
obtained by the alignment device shown in the figure. This alignment device comprises an 2-stage 25' with 20? : Equipped. The other configurations are the same as those of the previous embodiment. To obtain chord data, use X-stage 2
3. Move the Y-stage 24 and the 2-stage 25 by a predetermined distance NJ'c, and Interlocks to move the cut arm a predetermined distance.

At this time, the base plate spring assembly is displaced due to positional deviation due to manufacturing errors of the robot arm. As in the previous example, the arm is fully driven to make this displacement completely zero, and the calibration data is measured in a state where the displacement is zero.

Move the contact position several times to obtain the necessary calibration data.

(6) As described in detail, the present invention has a simple structure,
Since displacements in the X, Y, and Z directions can be detected independently, highly reliable calibration data can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the alignment device according to the present invention, FIG. 2 is a side view of the alignment device of FIG. 1 in use, and FIG. 3 shows a part of the leaf spring assembly according to the present invention. A perspective view, FIG. 4, and FIG. 5 are bridge circuit diagrams for detecting displacement in the X direction and two directions, respectively, of the positioning device according to the present invention, and FIG. 6 is a perspective view of another example of the positioning device according to the present invention. It is a diagram. 7... Reference plate, 8... Leaf spring assembly, 9... Cross spring, 10, 11-... Parallel spring, 13 + 13 a
, 13b. 13c, 13d, 19a, 19b, 19c, 19d...
・Strain gauge, 12...contact. Group 4/U Figure 5

Claims (1)

[Claims] 1. A contact element that constantly contacts a reference position at the tip of a robot arm to be calibrated, and a plate spring assembly for detecting displacement in X, Y, and Z directions orthogonal to each of the contact elements, the plate spring assembly: A parallel plate spring for detecting displacement in the X direction, which is arranged perpendicularly to the X direction of the entire plane part, a parallel plate spring for detecting displacement in the Y direction, which is arranged perpendicularly to the Y direction of the plane part, and a plane part arranged perpendicularly to the Z direction, A positioning device for calibrating a coordinate system of an articulated robot, which includes a cross spring for detecting the degree in two directions, with the above-mentioned contactor fixed in the center.