JPH04294986A - Measuring method for length of robot arm and coordinate value compensation method for horizontal articulated robot using thereof - Google Patents

Abstract

PURPOSE:To measure a robot arm length without using a length measuring device and to compensate a robot coordinate at its position based on the measured value. CONSTITUTION:The hand center of a 2nd arm is respectively positioned with 1st and 2nd arms 4 being reversed from the right hand system to the left hand system or from the left hand system to the right hand system, in a teaching mode, to the reference point apart by the specified distance from the revolving center of the 1st arm of a horizontal articulated robot. And, each revolving angle is calculated with the moving pulse number spent by each arm in the reverse revolving being counted by a counter 8, and the lengths of the 1st and 2nd arms are calculated by this each revolving angle and the above specified distance. Moreover, the command coordinate value of the hand center of the 2nd arm is compensated based on the error in the calculated 1st and 2nd arms length dimension and respective reference length dimension.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the arm length of a horizontal articulated robot and a method for correcting coordinate values.

0002

[Prior Art] Conventionally, in order to ensure the positioning accuracy of horizontal articulated robots, each assembled arm is inspected using a length measuring device, etc. to see if its length is within specified dimensional tolerances, and if it is outside the tolerances, it is checked. If so, I would have readjusted the assembly. Furthermore, in Japanese Patent Laid-Open No. 58-114887, the robot itself is used as a measuring device to recognize the relative position between a visual coordinate system fixed to its own visual input device and a coordinate system of the robot itself. Then, the deviation between the visual coordinate system and the robot's own coordinate system, which occurs due to assembly errors unique to the robot, is calculated and corrected so that the coordinate values of the robot itself match the coordinate values of the visual coordinate system.

0003

[Problems to be Solved by the Invention] However, in order to measure the length of each assembled arm, a large length measuring device is required, and there are cases where accurate measurement cannot be performed in the assembled state. Furthermore, the method of correcting errors by providing a visual device requires an expensive visual input device or visual recognition device.

0004

[Means for Solving the Problems] The present invention provides a method for measuring a reference point at a predetermined distance from the center of rotation of the first arm of a horizontal articulated robot without using any special length measuring device or visual device.
In the teaching mode, flip the first and second arms from right-handed to left-handed or from left-handed to right-handed,
Position the centers of the hands of the second arm. Then, each rotation angle is calculated by counting the number of movement pulses required for each arm to rotate in reverse, and the lengths of the first and second arms are calculated based on each rotation angle and the predetermined distance. Furthermore, the command coordinate value of the hand center of the second arm is corrected based on the error between the calculated length dimensions of the first and second arms and the respective reference length dimensions.

[0005]

[Function] The length of each arm of a horizontal articulated robot can be calculated without using a special length measuring device, and even if there is dimensional variation in the length of each arm, the robot hand can be accurately positioned at the command coordinate value. .

[0006]

[Embodiment] An embodiment of the present invention will be explained based on the drawings.

FIG. 1 is a plan view showing a robot which is to carry out the method for measuring the length of a robot arm and the method for correcting coordinate values of a horizontal articulated robot using the same according to the present invention, and FIG. 2 is a side view thereof.

Reference numeral 1 denotes a horizontal articulated robot, which fixes its base 2 at a predetermined position on a surface plate 10. 31 is a first joint whose axis of rotation is vertical, to which one end of the first arm 3 is attached. Reference numeral 41 indicates a second joint connecting the other end of the first arm 3 and one end of the second arm 4, and its rotation axis is perpendicular to the horizontal plane. Further, the rotation angles θ1 and θ2 of the joints 31 and 41 are adjusted by motors (not shown), and the first arm 3 and the second arm 4 are rotated left and right, respectively. 5 is the second arm 4
A hand portion attached to the other end has a Z axis that moves the finger 6 up and down by a motor (not shown). Reference numeral 7 denotes a control panel that drives each motor (not shown) to numerically control the first and second joints and the hand section, and controls the gripping operation of the fingers 6. Reference numeral 8 denotes a counter that counts the number of movement pulses required for each of the joints 31 and 41 to rotate, that is, counts the output pulses of a rotary encoder (not shown) built in each joint. 11
is a reference pole with known dimensions provided on the surface plate 10, and the first pole is determined by positioning and fixing the base 2 on the surface plate.
It stands at a distance measured in advance from the axis of rotation of the joint.

The arm length measuring method according to this embodiment having such a configuration will be explained based on FIG. 3.

In FIG. 3, the rotational axis position of the first joint on the surface plate 10 is set as point A, and the center of the reference pole 11 is set as point C.
Point. First, set the arm in the free state in teaching mode as a right-handed system (the rotation axis position of the second joint is on the right side when viewed from the robot body with respect to the straight line connecting the rotation axis position of the first joint and the hand part). from the hand section 5.
Bring the Z-axis almost directly above the pole 11, gradually lower the Z-axis by jogging, and grip the pole with fingers 6.
Align the center point C of the pole with the Z-axis position of the hand. At this time, in accordance with the rotation of the joints 31 and 41, the counts of the counters that were counting the number of movement pulses are reset,
The X-Y coordinate values of point C are stored in the control panel 7. The rotation axis position of the second joint on the surface plate 10 in this state is defined as point B. Then, release the finger 6 and move the hand part 5 to Z.
Raise the axis, keep the X coordinate value almost constant, and temporarily change the Y coordinate to A.
Move the arms 3 and 4 away from the point so that they are left-handed (the position of the rotation axis of the second joint is on the left side when viewed from the robot body side with respect to the straight line connecting the rotation axis position of the first joint and the hand part). The operator moves the hand unit closer to the pole 11 again, lowers the Z-axis of the hand unit 5 at the X-Y coordinate position of point C stored in the right-handed system, and grips the pole with the fingers 6. At this time, the counter 8 counts the number of movement pulses corresponding to the movement of the joints 31 and 41, and multiplies each count value by each rotation angle per movement pulse determined by the built-in rotary encoder. 31 and 41 are calculated. The turning angle for the joint 31 to move from the right-handed system to the left-hand system is θ1, and the turning angle for the joint 41 to move from the right-handed system to the left-hand system is θ2. Let the rotational axis position of the joint be point B'.

As shown in FIG. 3, the length of the first arm 3, that is, the length of line segment AB or AB', is L1, and the length of the second arm 4, that is, line segment BC or line segment B'C. If the length of is L2, and the distance from the rotation axis of the first joint to the center point of the reference pole, that is, the length of the line segment AC, is S,
Triangle ABC and triangle AB'C are congruent. Therefore,
The angle α between line segments AB and AC is

0012

[Math 1]

The angle β between line segments AC and BC is calculated by
teeth,

[0014]

[Math 2]

It is calculated as follows. Once the length of one side of the triangle and the angles at both ends are determined, L1 and L2 are determined by the law of sine and cosine of trigonometric functions.

[0016]

[Math 3]

[0017]

[Math 4]

The arm lengths L1 and L2 are calculated by substituting S, α, and β into these.

Furthermore, the amount of error between the calculated arm length dimensions of the first arm 3 and second arm 4 and the reference length dimension of each arm is stored in the control panel 7, and when the robot is numerically controlled. In this step, the position of the commanded coordinates of the Z-axis of the hand section 5 is corrected based on the error amount, and the Z-axis is brought to the position according to the commanded coordinates.

[0020]

As described above, by using the method for measuring the length of a robot arm of the present invention and the method for correcting the coordinate values of a horizontal articulated robot using the method, each arm length can be accurately measured without using a special length measuring device. It can be calculated well, and even if there are dimensional variations in the length of each arm, the robot hand can be accurately positioned at the command coordinate values, so there is no need to equip an expensive length measuring device as a shipping inspection facility for the robot. The position of the robot can be corrected at low cost without using a complicated visual recognition device or the like.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a robot that is to carry out a method for measuring the length of a robot arm and a method for correcting coordinate values of a horizontal articulated robot using the same according to the present invention.

FIG. 2 is a side view showing a robot that is to carry out a method for measuring the length of a robot arm and a method for correcting coordinate values of a horizontal articulated robot using the same according to the present invention.

FIG. 3 is a plan view showing the relationship between points related to the arm length measurement method in the embodiment.

[Explanation of symbols]

1 Horizontal articulated robot 2 Base 3, 4 Arm 31, 41 joint 5 Hand part 6 Finger 7 Control panel 8 Counter 10 Surface plate 11 Standard pole

Claims (2)

[Claims] Claim 1: When measuring the arm length of a horizontal articulated robot, the first and second arms are moved from a right-handed system to a left-handed system in a teaching mode at a reference point spaced a predetermined distance from the rotation center of the first arm. Alternatively, by reversing from the left-handed system to the right-handed system, position the hand center of the second arm, calculate each rotation angle by counting the number of movement pulses required for each arm to reverse rotation, and calculate each rotation angle and A method for measuring the length of a robot arm, characterized in that the lengths of the first and second arms are calculated based on the predetermined distance. 2. Correcting the command coordinate value of the hand center of the second arm based on the error between the length dimension of the first and second arms calculated by the measuring method of claim 1 and each reference length dimension. A coordinate value correction method for a horizontal articulated robot.