JP3096875B2 - Robot arm length correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to measures the amount of change in the robot arm lengths generated from <br/> to such as ambient temperature changes in a non-contact sensor, the robot arm length for correcting complement <br/> Related to a corrector.

[0002]

Arm length of the robot is changed due to ambient temperature changes of the Prior Art The production line or the like using a robotic system, tool tip attached to the hand of the robot (to
ol center point) deviates from the initial reference position, but this phenomenon reduces the precision of work that is regarded as important when working with robots, and eventually results in deterioration of the quality of the target product Will be invited.

Therefore, when it is attempted to repeatedly perform an operation requiring precision using a robot system, it is necessary to measure and correct the amount of change in the length of the robot arm due to the above-mentioned temperature change. However, as a method for responding to such a temperature change, there are a method of installing a constant temperature chamber to maintain the temperature around the work constant, and a method of detecting a position error using a sensor or the like to correct a local (Local) correction. And the like.

[0004]

However, when the robot system is used for measuring three-dimensional absolute coordinate axes in space like a three-dimensional measuring device, it is not possible to install a constant temperature chamber or the like, and correction is not possible. to become possible, the problem or performed in any manner the correction for temperature changes of the robot arm length in such a case has not been solved is reality.

Therefore, the present invention has been made in view of the above circumstances, and in a conventional method of installing a constant temperature chamber or detecting a position error using a sensor or the like and performing local correction, the length of the robot arm is reduced. and to provide a complement <br/> positive apparatus for a robot arm length can fit into such a case the correction is not possible for the temperature changes.

[0006]

Therefore, a robot arm length correction apparatus according to the present invention includes a calibration jig (5) having a plurality of measurement points (5a) on its surface and having a low coefficient of thermal expansion, and a robot (5). 1) a position measuring means attached to the hand (2) to measure a relative position of the robot arm with respect to the measurement point (5a); and a change amount calculating means for calculating a change amount of the robot arm length. Robot arm length correction means for correcting the robot arm length based on the amount of change in the robot arm length, the robot arm length correction device comprising:
The calibration jig (5) has different sizes.
Blocks, such as pentahedron, hexahedron,
Of the polyhedrons such as heptahedra or cylinders, large
Multi-stage type in which small blocks are sequentially connected to the top surface of the rack
With multiple measurement points on its outer surface.
Display and change of robot arm length from various positions
Can be measured, and the position measuring means determines an initial state of the robot arm with respect to the measurement points in an initial state facing one or more measurement points, and determines the initial position measurement during the operation. After moving to the same path as the moving path at the time, measure the measurement position of the robot arm with respect to the same measurement point,
The error between the initial position coordinates and the measurement position coordinates (Δx, Δ
y, △ z), the robot arm length change (△
1) is calculated, and the correction means corrects the robot arm length based on the calculation result. Also before
The calibration jig (5) can be used to
Locks can also be used in combination with each other.

The position measuring means includes a camera used for obtaining a two-dimensional position with respect to a designated portion on a screen in combination with an image processing device or the like, and a distance to a measuring object by trigonometry. Laser Displacement Sensor (Laser Displacement Sensor)
ment Sensor, hereinafter abbreviated as “LDS”. ) Is preferable.

[0008] The calibration jig installed corresponding to the non-contact type sensor may take a form in which two large and small rectangular hexahedrons are stacked in two vertical stages.
It is preferable that a measurement point composed of a black circle that can be sensed by the camera is displayed at the center of each surface of the upper hexahedron and at the corner of each surface of the lower hexahedron. The measurement point does not need to be a black circle, but may be any as long as it can be sensed by a camera, and any centroid or the like can be obtained according to required accuracy. Absent.

[0009]

With this configuration, the center position of the measurement point displayed on the calibration jig is obtained based on information from the camera mounted on the robot hand, and the LDS is determined.
3D relative distance between the robot hand and the calibration jig is measured based on the information from and the three-dimensional error amount is detected by comparing the measured value with the initial value. A change amount of the robot arm length is calculated, and the changed robot arm length is corrected based on the change amount.

[0010]

The structure and method of measuring the compensation device in such a robotic arm length EXAMPLES The invention will be described in more detail by the accompanying drawings, as follows. Figure 1 shows the overall structure of a compensation apparatus for a robot arm length in accordance with the present invention, as illustrated, the arm of the robot (1) (1
A non-contact sensor (3) (see FIG. 2) including a camera (3a) and an LDS (3b) is attached to a hand (2) attached to the tip of (a).

[0011] Then, on the hand the installed base below the (2) (4), the calibration jig two different Tsunojika side body sizes were placed superimposed form (5) is the disposed I have. The complement hour robotic arm length, hand (2), teaches the operation to face perpendicularly to the calibration jig (5) faces each measurement point displayed on the (5a ') (Teach-in) Then, the hand (2) continuously moves and stops in accordance with the measurement points (5a '), and performs sensing in a state where the hand (2) stops at the measurement points (5a').

FIGS. 2 to 4 show such a sensing process.
This will be described with reference to FIG. Figure 2 shows the hand of the robot (1)
Fig. 3 shows the structure of the non-contact type sensor mounted on (2) and the sensing state. Fig. 3 shows the calibration jig (5), and Fig. 4 illustrates the measurement principle. is there. As shown in these drawings, the measurement using the non-contact sensor (3) in the present invention is performed by a camera.
(3a) and the LDS (3b) are performed in a non-contact manner. At this time, the camera (3a) is mounted on the plane of the calibration jig (5).
(5a) Measurement point consisting of black circle displayed on top (5a ')
The operation from the camera (3a) is sent to an image processing device (not shown) to measure a two-dimensional position. On the other hand, information from the LDS (3b) integrated with the camera (3a) is sent to the laser displacement meter,
The distance from the LDS (3b) to the object to be measured by triangulation, in other words, the calibration jig (5) from the hand (2)
Measure the relative distance to. Thus, the three-dimensional relative position of the hand (2) with respect to the measurement point (5a ') is detected.

That is, the center position of the measurement point (5a ') is measured based on the information from the camera (3a), and the LDS (3b)
The three-dimensional relative position can be obtained by measuring the distance from the robot hand (2) to the plane (5a) on which the measurement point (5a ') is displayed based on the information from the robot. More specifically, as shown in FIG. 4, two measurement points (5a ') displayed on each plane (5a) of the calibration jig (5) based on information from the camera (3a). The dimensional center position (X, Y) is obtained, and the relative distance Z from the tip of the LDS (3b) to the plane (5a) of the calibration jig (5) is measured based on the information from the LDS (3b). is there.

At this time, the position of the black circle constituting the measurement point (5a ') does not need to be accurately determined, and the size of the circle is basically not limited. Actually, the difference between the measured value measured at the time of temperature correction of the robot arm length and the initial value (initial measured value or initial input value) is displayed as a three-dimensional error in the X, Y, and Z directions. Represents the three-dimensional minute change of the tip of the robot hand (2) caused by the change in the length of the robot arm due to the change in ambient temperature.
From this error amount, the change amount of each arm length of the robot (1) is calculated in reverse.

As the robot arm length change amount calculating means 6 for calculating the arm length change amount from the measured error amount, for example, a microcomputer or the like is provided.
The algorithm (Algorithm) for calculating the amount of change in the arm length performed by such a microcomputer is as follows. Motion of robot (1) (Kinematic transform
ation) is displayed as in the following equation (1).

[0016] △ x = f (θ, l ) (1) wherein, x represents a Cartesian (Cartesian Cordination) value of the robot hand (2) tip, theta joints variation, l is the length of each arm Are shown. After a change in the arm length due to a change in the ambient temperature, a three-dimensional measurement value obtained by measuring one point at the measurement point (5a ') on the calibration jig (5) is subtracted from the initial value. If the dimensional error value is defined as Δl, a relational expression of two variables due to a minute change can be expressed by the following equation (2).

[0017] Δ x = ∂ / ∂ l · f (θ, l) · Δ l = J (θ) · Δ l (2) Here, J (θ) = ∂ / ∂ l · f (θ, l) is generally called Jacobian matrix (Jacobian matrix), which shows a linear relationship between the amount of change in length of the arm of the robot delta l and 3-dimensional error value delta x. From the above equation (2), the equation for the values at K different positions can be expressed as equation (3).

[0018] Δ x i = J (θ i ) · Δ l (3) i = 1,2,3, ····, K such the K equations representable by a single formula, such as: It is. Here Δ X = J · Δ l,

[0019]

(Equation 1)

[0020] To calculate the delta l is at least 3K
A number of measurements that satisfy ≧ n must be made.
From this, ‖Δ X by the least square method - it is possible to obtain the value of J delta · l ‖ value becomes minimum delta l. If the matrix J value is not singular, the next value Δ
1 can be obtained.

[0021] If ^{Δ l = (J TJ J)} -1 · J T · Δ X Again, the delta l is the change of the robot arm length generated by the temperature change. In this way, the robotic arm length variation delta l obtained, by adding the initial robotic arm length l, it is possible to correct the robot arm length due to changes in ambient temperature (l + Δ l) . Such correction is performed by a robot arm length correction means 7 composed of a microcomputer or the like.

[0022] Note that, after this, the control unit 8 of the robot system that controls the operation of the robot, the corrected robot arm length (l + delta l) is introduced to determine the operation of the robot (1) , by being converted into mechanisms of the new robot, it is possible to obtain the operation of the robot in consideration of the length change of the robot arm caused by such ambient temperature changes.

[0023]

As described above, according to the present invention,
In particular, even when the installation space such as a constant temperature room cannot be secured on a production line, the change amount of the robot arm length can be calculated, and the robot arm length is corrected based on the calculated amount. There is an effect that can be. As a result, it is possible to prevent a decrease in work precision due to a change in the length of the robot arm caused by a change in ambient temperature or the like .

[Brief description of the drawings]

Side view showing the entire structure of a compensation apparatus for a robot arm length in accordance with the invention, FIG

FIG. 2 is an enlarged view showing a sensor unit structure and a sensing state of FIG. 1;

Perspective view of a calibration jig compensation apparatus for a robot arm length in accordance with the present invention; FIG

Explanatory view showing the measurement principle of the compensation apparatus for a robot arm length in accordance with the present invention; FIG

[Explanation of symbols]

 Reference Signs List 1 robot 1a arm 2 hand 3 non-contact sensor 3a camera 3b laser displacement sensor 5 calibration jig 5a plane 5a 'measurement point 6,7 microcomputer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B25J 13/08 G05D 3/12 305 B25J 9/10

Claims (3)

(57) [Claims] 1. A calibration jig (5) having a plurality of measurement points (5a) on its surface and having a low coefficient of thermal expansion, mounted on a hand (2) of a robot (1), and provided with respect to said measurement points (5a). Position measuring means for measuring the relative position of the robot arm; change amount calculating means for calculating the change amount of the robot arm length; and correcting the robot arm length based on the calculated change amount of the robot arm length. Robot arm length correction means, comprising: a robot arm length correction means, wherein the calibration jig (5) has different sizes.
Above the larger block of multiple blocks
Constructed in a multi-stage configuration in which small blocks are sequentially connected to the surface
Multiple measurement points are displayed on its outer surface.
To measure the change in robot arm length from various positions.
In the initial state facing one or more measurement points, the position measuring means determines the initial state of the robot arm for those measurement points, and during the operation, the position of the robot arm during the initial position measurement is determined. After moving on the same route as the movement route, the measurement position of the robot arm with respect to the same measurement point is measured, and the change amount calculating means calculates an error (Δx, Δy, Δz) between the initial position coordinates and the measurement position coordinates. ), The robot arm length change (長 l) is calculated, and based on the result,
An apparatus for correcting the length of a robot arm, wherein the correction means corrects the length of the robot arm. 2. The camera according to claim 1, wherein said position measuring means includes a camera (3a) and a
Non-contact sensor (3) consisting of a user displacement sensor (LSD) (3b)
The camera (3a) is connected to the calibration jig.
(5) Position the center of the upper measurement point (5a ') with the laser
-Displacement sensor (3b) moves the measurement point (5
a ') and measure the distance to each plane.
Detect the 3D position of the robot hand with respect to the point
The length of the robot arm according to claim 1, wherein:
Correction device. The amount of change in the length of the robot arm is measured by a measurement point.
The initial position coordinates of the robot hand with respect to the point (5a ')
And the error between the measurement position coordinates at the time of measurement and
And calculating by a least squares method.
2. The robot arm length correction device according to 1.