JP2538287B2 - Origin adjustment method for horizontal joint robot - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to origin adjustment, that is, calibration, of a horizontal joint type robot in which two arms move horizontally.

2. Description of the Related Art In horizontal articulated robots, as a method of adjusting the origin of the mounting base coordinate system of the robot mechanism and the coordinate system of the robot control, that is, a method of calibration, Japanese Patent Laid-Open No. 62-63
In 091 publication, a method for reducing the error in calibration is proposed.

The calibration method described in Japanese Patent Laid-Open No. 62-63091 includes a work of matching a reference point of a wrist provided at the tip of an arm with a known reference point on the base coordinates.
By performing the rotation, the rotation position of the arm with respect to the reference point on the base coordinates, that is, the first and second second moving in the horizontal direction.
The rotation angle of one arm was calculated and the origin adjustment (calibration) in the horizontal direction was completed. Then, based on the rotation angle of each arm and the lengths (design values) of the first and second arms obtained by this calibration, the motion target position by the motion program of the robot given in the orthogonal coordinate system of the base coordinate system. On the other hand, the rotation angle of each arm is obtained by inverse conversion.

Problems to be Solved by the Invention In the above-described calibration method, the reference point of the base coordinate system and the reference point of the wrist are matched once,
Calibration is completed by obtaining the angle of the arm at this time, and the arbitrary position (x, y) in the base coordinate system
To find the position of control system coordinates (rotation angle of arm) with respect to, set the length of each of the first and second arms as the design value,
This value and the angle of the arm obtained by the above calibration are calculated and obtained. But,
When an error occurs in the length of each arm due to machining, there is a drawback that an error occurs in the arm angle due to calibration, and further, a large error occurs in the operation position of the wrist due to the arm length and this angle error.

For example, if the start and end points of a straight line are taught and the path of the straight line is controlled, the length and angle of each arm differ between the calculated value and the actual value, so what should be a straight line between the start point and the end point. Even when a curved line is formed, or when three points of a starting point, an ending point, and a passing point of a circular arc are taught to control the path of the circular arc, a phenomenon that an accurate circular arc cannot be drawn occurs.

In addition, when the robot motion program is created offline in the base Cartesian coordinate system, the offline program is inversely transformed to determine the angle of each arm, and when the robot is operated, the motion target position depends on the arm length and angle. The phenomenon that is different occurs.

Further, in the case where the robot operation program is stored in the orthogonal coordinate system of the base coordinate system, even if the robot is replaced, there is a drawback that an accurate operation position cannot be obtained due to a difference in arm length and angle. is there.

Therefore, an object of the present invention is to improve the accuracy of the path control by the calculation of straight lines, arcs, etc. in the horizontal joint type robot, the accuracy of the operation position of offline programming, and the compatibility of the programs when the robot is replaced with high accuracy. It is to provide an origin adjustment (calibration) method.

Means for Solving Problems According to the present invention, absolute position detectors for detecting the rotational positions of the first arm and the second arm are respectively provided, and the known base reference points on the mounting base coordinates of the robot mechanism unit are provided. The work of matching the reference point of the wrist at the tip of the robot arm was performed twice by changing the posture of each arm, and the angle of each arm at the reference point matching position of each time was obtained from the absolute position detector. The origin of a horizontal joint robot in which two arms move horizontally is obtained by determining the length of each arm and the angle of the reference position of the first and second arms with respect to the base reference point from each arm angle and the base reference point position. The above problems were solved.

Operation FIG. 1 is an explanatory view for explaining the working principle of the origin adjustment method of the horizontal joint type robot of the present invention, where A is the first arm 3,
A rotation center point 3 ', B is a base reference point, which is a known position on the base coordinate system, and is a point to be matched with a wrist reference point (a target point operated by the robot). 3, 3'is the first arm that moves horizontally about the center of rotation A,
Reference numeral 5'denotes a second arm that moves in the horizontal direction at the tip of the first arm 3, 3 ', and is the first time when the wrist reference position provided at the tip of the second arm 5 matches the base reference position B. The positions of the first and second arms at this time are represented as 3 and 5, respectively, and the positions of the first and second arms when the wrist reference position is matched with the second base reference position B are 3 ′, It is expressed as 5 '.

Further, d1 indicates the reference position of the absolute position detector that detects the rotational position of the first arm, and may be any position. Also,
d2 indicates the reference position of the absolute position detector that detects the position of the second arm with respect to the first arm, and this position may be any position.

Further, x1 is the distance from the rotation center A of the first arm 3 to the base reference point B, L1 and L2 are the lengths of the first and second arms,
θ5 is the angle of the base reference point B with respect to the base coordinates XY, θ6 is the angle of the reference position d1 of the absolute position detector of the first arm 3 with respect to the base reference point B, and θ7 is the absolute value of the second arm with respect to the first arm. The angle is the reference position d2 of the position detector.

Therefore, first, the first arm and the second arm are rotated to match the wrist reference point with the base reference point B, and the first arm 3 and the second arm 5 are moved to the base reference point in FIG. In the first matching work located on the left side of B, the absolute position detector for detecting the rotational position of the first arm has values of θ1,
The value of the absolute position detector that detects the rotational position of the arm is θ
Suppose it was 3.

Next, when the joint portions of the first and second arms are moved to the right side of the base reference point B in FIG. 1 and the wrist reference point is matched with the base reference point B (the first and second arms are 3 ', 5'), the value of the absolute position detector for detecting the rotational position of the first arm 3 is θ2, and the value of the absolute position detector for detecting the rotational position of the second arm 5 is θ4. Then, the rotation angles θ1 to θ4 of the first and second arms obtained by the first and second matching operations between the base reference point and the wrist reference point and the known base reference point B From the position of the base reference point B to the length x1, L2 of the first and second arms 3 and 5 and the absolute position detector of the first arm relative to the base reference point B. The angle θ6 of the reference position and the angle θ7 of the reference position of the absolute position detector of the second arm with respect to the first arm are obtained. You.

 This is obtained as follows.

The first when the base reference point B and the wrist reference point are matched
Considering a triangle formed by a line connecting the second arms 3 and 5, the rotation center A, and the base reference point B, each triangle formed by the matching of the first reference point and the second reference point is 3 It is congruent because the sides are the same triangle, and the angle between the lines A and B connecting the center of rotation A and the base reference point B and the second arms 5 and 5'is α, and the first arms 3 and 3 ' Let β be the angle and γ be the angle between the first and second arms, β = (θ1-θ2) / 2 (1) Also, θ7 + θ4 + γ = 180 ° (2) -θ3-θ7 + γ = 180 ° (3) Note that the rotation direction of θ3 is opposite to that of θ4, and the output of the absolute position detector that detects the rotation position of the second arm has a negative value. Then, it is set to −θ3.

From the above equations (2) and (3), γ = 180 ° − (θ4−θ3) / 2 (4) α = 180 ° − (γ + β) = (θ2 + θ4−θ1−θ3) / 2 (5) Also, from the triangular sine law Therefore, θ6 = θ2 + β = (θ1 + θ2) / 2 (9) θ7 = 180−θ4-γ = − (θ3 + θ4) / 2 (10) As shown by the above formulas (7) to (10), Changing the arm to match the wrist reference point with the base reference point 2
This operation is performed each time, and the rotation angles θ1 to θ4 of the first and second arms and the rotation of the first arm obtained from the absolute position detector of the first arm and the absolute position detector of the second arm in each operation. From the distance x1 from the center A to the base reference point B, the lengths L1 and L2 of each arm and the reference position angle θ6 of the absolute position detector of the first arm with respect to the base reference point B, the second position with respect to the first arm. Angle θ of the reference position of the absolute position detector of the arm
When 7 is obtained, the origin adjustment (calibration) is completed, and the obtained angles θ6 and θ7 of the reference position, the lengths L1 and L2 of each arm, and the position of the base reference point, that is, the rotation center A and Distance between base reference points B x1, base coordinate X-
Based on the angle θ5 of the base reference point with respect to Y, the operation target position of the program instructed in the base coordinate system XY is inversely converted, and the angle of each arm can be obtained to accurately operate the robot.

Embodiment FIG. 2 is a perspective view showing an example of a horizontal joint robot for carrying out an embodiment of the origin adjusting method of the present invention. In the figure, 1 is placed on the base 2 and within a predetermined rotation range (θ)
Although not shown in the figure, a rotation mechanism for rotating the post 1 is provided inside the base 2.

Reference numeral 3 denotes a first arm that is horizontally directed by a support shaft 4 that is inserted into the post 1. A tip end of the first arm 3 has a second arm 5 that is rotationally controlled in the horizontal direction. Further, a wrist 51 is provided at the tip of the second arm 5. Although not shown in the figure, inside the post 1, the support shaft 4 is moved up and down within a predetermined range (Z) to make the first
A drive mechanism for controlling the height of the arm 3 is provided, and the spindle 4 is driven up and down to control the height of the first arm (operating arm). Although not shown in FIG. 2, an absolute position detector for detecting the rotational position of the first arm 3 and an absolute position detection for detecting the rotational position of the second arm 5 with respect to the first arm 3. A vessel is provided for each.

When the robot is installed on the floor, the basic coordinate directions of the robot mechanism unit are exactly aligned with the X, Y, and Z axis directions.

Reference numeral 6 is a zero degree adjusting jig for matching the coordinate system of the robot mechanism unit with the coordinate system of the robot control unit. The zero degree adjusting jig 6 has columns 61, 61 whose lower part is fixed to a pedestal 21 provided on the base 2 aligned with the reference coordinate axis, and has a cross section of “L” shape at the tip thereof. The reference plate 62 having the above-mentioned shape is fixed, and as shown clearly in FIG. 3, two reference holes 63 and 64 are formed in the plane portion on a line parallel to the X axis. Standard board 6
A dial gauge mounting body 65 having an "L" -shaped cross section is fixed to the end portion of 2. In addition, in the flat part of the reference board 62,
The dial gauge 7 is fixed to the robot in the height direction, that is, the Z-axis direction, and the dial gauge 8 for fixing the wrist 51 is fixed to the dial gauge mounting body 65.

The wrist 51 has a wrist jig 9 as shown in FIG.
Is installed. The wrist jig 9 includes a flat surface portion 91, a YZ surface 92, an XZ surface 93, and a YZ surface 92 which are attached to the lower surface of the wrist.
It has a wrist adjustment piece 94 parallel to it. In addition, in the flat portion 91,
Four attachment holes 95 for the wrist 51 and a through hole 96 for inserting into a reference hole provided on the wrist 51 are provided. The dial gauge 10 which gives a reference in the X-axis direction is fixed to the YZ surface 92, and the dial gauge 10 which gives a reference in the Y direction is provided in the XZ surface 93.
11 is stuck. Note that FIG. 5 is a bottom view of the wrist 51 as viewed from the bottom surface direction.

With such a configuration, the origin adjustment method in this embodiment will be described below.

First, as shown in FIG. 3, a jig having a circular table shape is prepared, and the boss 121 on the lower surface of the jig 12 is attached to the reference hole 64.
And the jig is fixed to the reference board 62. Then, the probe 7a of the dial gauge 7 is brought into contact with the lower surface of the jig 12, and the scale of the dial gauge 7 at that time is recorded. In addition,
The lower surface position of the jig 12 is stored in the robot controller as a reference plane in the Z-axis direction of the robot mechanism section. Further, the probe 8a of the dial gauge 8 is brought into contact with the other side surface of the jig 12, and the scale of the dial gauge 8 at that time is recorded. Then, the jig 12 is removed from the reference board 62. The side surface position of the jig 12 is stored in the robot controller as a reference surface of the wrist of the robot mechanism section.

Then, as shown in FIG. 4, dial gauges 10, 11
The wrist jig 9 to which is attached is fixed to the wrist 51 by screwing. At this time, the through hole 96 provided in the wrist jig 9 is aligned with the reference hole of the wrist 51.

A cylindrical jig 14 as shown in FIG. 6 is prepared separately.
This cylindrical jig 14 is provided with a fixing boss 141 at the bottom. Then, the boss 141 is inserted through the through hole 96 provided in the wrist jig 9, and is attached to the wrist jig 9. In FIG. 5, the portion indicated by the dotted line indicates a cylindrical jig. After that, the probe 10a of the dial gauge 10 is brought into contact with the side surface of the cylindrical jig 14, and the dial gauge at that time is contacted.
Record 10 scales. Further, the probe 11a of the dial gauge 11 is brought into contact with the side surface of the cylindrical jig 14, and the scale of the dial gauge 11 at that time is recorded. This movement defines the center of movement of the wrist.

Next, the cylindrical jig 14 is removed from the wrist jig 9,
As shown in the figure, attach the boss 141 to the reference hole 63 of the reference plate 62.
And the cylindrical jig 14 is attached to the reference board 62. The side surface position of the jig 14 is stored in the robot controller as a reference plane in the X-axis direction and the Y-axis direction of the robot mechanism section.

From this state, the robot is set to the teaching mode using the operation panel of the horizontal joint type robot, and the wrist 51 is moved in the direction of the reference panel 62 using the jog feed button. Then, the wrist jig 9 is brought close to the cylindrical jig 14 attached to the reference board 62, and the probes 10a and 11a of the dial gauges 10 and 11 are respectively touched on the side surfaces of the cylindrical jig 14. While reading the scales of these dial gauges, the jog feed operation is further repeated to bring these values to the values recorded as described above. With this, the center of movement of the wrist, that is, the reference point reaches the base reference point, and the first matching operation between the wrist reference point and the base reference point in the X-axis direction and the Y-axis direction ends, and the first arm 3 at this time Value θ1 of the absolute position detector that detects the rotational position of the
Value of the absolute position detector that detects the rotational position of the arm 5
3 is stored in the controller of the robot.

Then, the joint portions of the first arm 3 and the second arm 5 are moved to the opposite side from the base reference point, and the first and second arms are moved.
By changing the postures of 3 and 5 and performing the same processing as described above, the wrist reference point is made to coincide with the base reference point, and the absolute position detector value θ2 for detecting the rotational position of the first arm 3 at this time, Second
The value θ4 of the absolute position detector that detects the rotational position of the arm 5 with respect to the first arm 3 is stored in the robot controller.

After that, the wrist 51 is further rotated by using the jog feed button, and the wrist adjustment piece 94 is brought into contact with the probe 8a of the dial gauge 8 as shown in FIG. 4, and the value of the dial gauge 8 is recorded to the front. This operation is repeated until the specified value is reached so that the wrist control reference matches the reference of the mechanical section.

Finally, lower the spindle 4 using the jog feed button,
The variable 94a of the wrist adjustment piece 94 is connected to the probe 7 of the dial gauge 7.
This operation is repeated until the value of the dial gauge 7 reaches the value recorded previously, and the control reference in the Z-axis direction matches the reference of the mechanical section. This completes the calibration in the Z-axis direction and the wrist rotation direction. Here, when the calibration set button on the operation panel is pressed, the robot controller causes the stored absolute position detector values θ1 to θ4 and the initially set rotation center of the robot first arm 3 to rotate. Based on the distance x1 between the base point and The angle θ6 of the reference position of the absolute position detector with respect to the point and the angle θ7 of the reference position of the absolute position detector of the second arm with respect to the first arm are obtained and stored, and the X, Y, Z axes of the robot and the wrist The initial data of the rotation axis is stored in the robot controller, and the coordinate system of the robot mechanism unit and the coordinate system of the robot controller are calibrated.

After completing such calibration operation,
The zero degree adjusting jig 6 and the wrist jig 9 are removed from the base 2 and the wrist 51, respectively, and a predetermined tool is attached to the wrist, and normal robot operation is performed.

EFFECTS OF THE INVENTION As described above, in the present invention, the length of the arm is accurately obtained, and the relative position (θ6, θ7) of the control coordinate system with respect to the base coordinate system of the robot is obtained. When improving the operation accuracy and teaching the start point and the end point of the straight line to perform the route control of the straight line, and when teaching the three points of the start point, the end point and the passing point of the arc to perform the route control of the arc, The robot controller converts each point from the robot arm angle, arm length, and relative position (angle) to the base coordinate to the base Cartesian coordinate system, calculates the route in the Cartesian coordinate system, and inversely transforms each arm angle. When the robot is moved to the above condition, since the arm length is accurately detected, the robot can be operated along the accurate path.

Even when the robot operation target position is given in the base orthogonal coordinate system by the off-line program, accurate operation can be obtained by performing the origin adjustment (calibration) as in the present invention.

Further, if the operation program of the robot is stored in the orthogonal coordinate system with respect to the base coordinates, the compatibility of the programs can be maintained by performing the origin adjustment of the present invention even when the robot is exchanged.

Since the length of the arm is obtained by adjusting the origin (calibration), it is not necessary to make the tolerance of the length of the robot arm extremely small, and it is not necessary to consider variations in machining, errors due to assembly, etc. Accurate operation can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining the operation principle of the present invention, FIG. 2 is a perspective view showing an example of a horizontal joint type robot for carrying out an embodiment of the present invention, and FIG. 3 is a front view of a reference board, FIG. Fig. 4 is a perspective view of a wrist jig, Fig. 5 is a bottom view of the wrist seen from below the wrist, Fig. 6 is a perspective view of a cylindrical jig, and Fig. 7 is a cylindrical jig mounted on a reference plate. It is a perspective view showing a state. 1 ... Post, 2 ... Base, 3 ... First arm, 4 ...
… Spindle, 5 …… Second arm, 51 …… Wrist, 6 …… Zero adjustment jig, 62 …… Reference board, 63,64 …… Reference hole, 7,8,10,
11 …… Dial gauge, 9 …… Wrist jig, 12 …… Jig,
14 …… Cylindrical jig.

Claims (1)

(57) [Claims] 1. In the origin adjustment of a horizontal joint robot of a type in which two arms move horizontally, absolute position detectors for detecting rotational positions of a first arm and a second arm are respectively provided, and a robot mechanism is provided. The work of matching the reference point of the wrist part at the tip of the robot arm with the known base reference point on the mounting base coordinates of each part is performed twice by changing the posture of each arm, and each time the reference point of the arm at the reference point matching position is adjusted. The angle is obtained from the absolute position detector, the length of each arm and the angle of the reference position of the first and second arms with respect to the base reference point are obtained from the obtained arm angle and the base reference point position, and the origin is adjusted. Origin adjustment method for horizontal joint robots.