JPH0775986A - Articulated robot - Google Patents

Abstract

PURPOSE:To determine an objective position of a chuck means easily by detecting slippage between the position of a chuck at the time of chucking a workpiece in the floating state and the position of the chuck at the time of chucking the workpiece in an objective moving position to obtain real position of the chuck. CONSTITUTION:A chuck 4 is fitted to a vertically moving shaft 8 at the tip of an arm through a floating means 10 formed by supporting a floating body 12 in the horizontally movable state by numerous balls 13, and a chuck position detecting means 20 formed of two position sensors 21, 22 provided in two orthogonal positions is provided to detect the position of the chuck 4 to the arm. A teaching means 30 obtains slippage DELTAX between the position of the chuck 4 at the time of chucking a workpiece 2 in the floating state and the position of the chuck 4 at the time of chucking the workpiece 2 in the objective moving position, and adds the jogging movement quantity of the arm to obtain the real chuck position on a robot coordinate system and to teach a robot control part 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an articulated robot. More specifically, the present invention relates to improvement of a teaching mechanism for teaching a robot a moving target position for work in an articulated robot.

[0002]

2. Description of the Related Art Conventionally, so-called teaching for setting a moving target position of an object to be moved to a robot is repeated jog movement of a chuck to gradually approach a target position, and position correction is repeated many times to select an accurate position. It is carried out. For example, teaching in the case of fitting work is generally done by moving the robot arm etc. to the target position (jog movement) by the worker and then lowering it with the robot chuck open to chuck the workpiece and apply external force. It is designed to store the position when chucked in the absence. Teaching is repeatedly performed while correcting the position until the work can be chucked without applying an external force, and an accurate target movement position is taught.
A visual sensor or the like may be conventionally used as an auxiliary device for facilitating position correction in teaching.

[0003]

However, the conventional teaching with a robot has a drawback that it requires a long time because the jog movement and the correction of the target position data have to be repeatedly executed many times. For example, in the case of a stocker robot (a robot that inserts articles into shelves), even an expert requires one and a half days to teach 100 shelves.

An auxiliary device such as a visual sensor for assisting the teaching work is expensive because it requires advanced and high performance image processing. In addition, the adjustment of the illumination is delicate for the convenience of handling the image, and there is a drawback that it is vulnerable to image disturbance.

An object of the present invention is to provide an articulated robot capable of executing highly accurate teaching of a target position in a short time by using an inexpensive auxiliary device.

[0006]

In order to achieve the above object, the present invention provides a work which has a chuck and which can be swiveled in a horizontal plane, and which swivels the arm between a plurality of positions and is gripped by the chuck. In an articulated robot that moves to a target position, floating means interposed between the arm and the chuck so that the chuck can freely move in a horizontal plane when teaching the arm, and a chuck position that detects the position of the chuck with respect to the arm. Find the deviation between the detection means and the chuck position when the workpiece is chucked in the floating state with no load, and the chuck position when the workpiece installed at the movement target position is chucked and add the jog movement amount of the arm to this. Teaching to find the true chuck position on the robot coordinate system and teach it to the robot controller It is composed stage and a bite, et al.

[0007]

Therefore, during teaching, the chuck is in a floating state in which it can move freely in the horizontal plane. Therefore, at the same time when the chuck grips the workpiece installed at the target movement position, the chuck itself moves to the center position of the workpiece. To the state where the workpiece is chucked without load, for example, in the case of fitting work, the workpiece gripped by the chuck is fitted to the inserted workpiece without external force due to twisting etc. To produce. The amount of movement of the chuck at this time, that is, the chuck position when gripping the work set at the target movement position from the chuck position when the work is chucked and simply suspended (hereinafter referred to as the reference position) The difference (deviation) can be obtained by the chuck position detecting means. Therefore, the true chuck position on the robot coordinate system can be obtained only by adding the amount of movement / deviation of the chuck required to match the center of the chuck with the center of the workpiece to the jog movement amount.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

First, FIGS. 1 to 6 show an embodiment of an articulated robot of the present invention.

FIG. 4 shows an example of an articulated robot to which the present invention is applied. This robot 1 has a chuck 4 and has arms 5 and 6 which can rotate in a horizontal plane.
It is an articulated robot that swivels to move the workpiece 2 gripped by the chuck 4 to a target position. This robot 1
In the case of, an arm 5 that revolves around the column 7 and an arm 6 that revolves around the tip of this arm 5 are provided.
The chuck 4 is provided via a floating means 10 on a shaft 8 that moves up and down at the tip of the arm 6. The column 7 portion is usually equipped with a controller for controlling the movement of the robot. Then, the data of the teaching means 30 that teaches the destination of the movement of the chuck 4 at the tip of the arm is input and stored in this controller.

FIG. 1 shows an example of the structure of the floating means 10. The floating means 10 is attached to the shaft 8 at the tip of the arm of the robot 1 shown in FIG. 4 so that the floating direction is horizontal. When the mounting state of the floating means 10 is horizontal, with respect to the force applied to the chuck 4, it moves only with respect to the force in the horizontal direction and does not move with respect to the force in the vertical direction.

The floating means 10 includes a fixed body 11 fixed to the movable side of the robot 1, for example, an arm 6, a floating body 12 that holds the chuck 4 and moves its position, and a floating body 12 that smoothly moves. , 13, and the floating body 12 for
, 15 for making the movable part movable and stopping it at a fixed position.

The fixed body 11 is a frame body for holding the floating body 12 in a movable state via a plurality of balls 13, 13 and for attaching the floating means 10 to the tip of the arm 6 of the robot 1. The ceiling and floor surfaces of the inner surface of the fixed body 11 are processed into flat surfaces so that the balls 13 can easily roll. Further, an opening 14 having a size that defines a movement range is provided at the center of the floor so that the floating body 12 can move within a predetermined range.

The floating body 12 is composed of an upper surface plate 12a housed inside the fixed body 11, a lower surface plate 12b outside the fixed body 11 to which the chuck 4 is attached, and a column 12c connecting these. The top plate 12a is
Is held by a plurality of balls 13, ...
Although it can move freely in the horizontal direction, the movement is restricted in the vertical direction. Also, the top plate 12a
4 corners of the fixed body 11 and the coil spring 15,
, 15 are connected. The floating body 12 stands still at a place where the tension balance of the four coil springs 15, ..., 15 is maintained. In addition, as shown in FIG.
A fixing metal fitting 1 such as a connecting pin between the fixing member 2 and the fixing member 11.
By inserting 6, 16 it is fixed and loses its floating function.

Further, the fixed body 11 is provided with a chuck position detecting means 20 for detecting the position of the chuck 4 by measuring the position of the floating body 12.
The chuck position detecting means 20 is used for the floating body 1.
The two position sensors 21 and 22 measure the distance to the side end surface of the upper surface plate 12a of the floating body 12 in two axis (X, Y) directions orthogonal to each other in two horizontal planes. That is, the positional relationship among the upper plate 12a, the lower plate 12b, and the chuck 4 is mechanically determined, and the upper plate 12a
By measuring the position of a, the position of the chuck 4, that is, the relative position of the work 2 when the work 2 is gripped can be known. These position sensors 21 and 22 have
For example, a non-contact type laser distance sensor or the like is used.

The outputs of the position sensors 21, 22 are input to the teaching means 30. The teaching means 30 chucks the work set at the reference position S and the movement target position when the work 2 is chucked and simply hung, that is, the work 2 inserted into the inserted work 3 at the time of fitting work. Chuck position (actual work center position) T
The amount of deviation (Δx, Δy) from
The amount of jog movement is added to obtain the true chuck position on the robot coordinate system and the robot controller 33 is taught. In the case of the present embodiment, it is configured by a computer (CPU) and the programs shown in FIGS. The teaching means 30 includes an arithmetic unit 31 including a computer (CPU),
A signal for controlling the movement of the chuck 4 (data indicating the true chuck position), which includes a storage unit 32 that stores the measured values of the position sensors 21 and 22 and the calculation results.
Is output to the robot controller 33. The robot controller 33 drives the robot 1 based on the drive signal from the calculation unit 31, grips the work 2 by the chuck 4, moves to the target position, and inserts the inserted body 3
Work 2 is loaded.

The teaching procedure of the target position data of the work 2 by the robot of this embodiment will be described with reference to the flowcharts of FIGS. 5 and 6.

First, when starting the teaching of the robot 1, it is judged whether or not the chuck 4 is used in a floating state at the time of the work actually performed by the robot 1, for example, the fitting work (step 1). Then, when the floating state is not set, the floating body 12 is fixed to the fixed body 11 using the floating stopper fixing metal fitting 16 (step 2), and the position is set to the reference position (dx, dy).
Is stored in the storage unit 32 (step 3). After the storage of the reference position (dx, dy) is completed, the floating stopper fixture 16 is removed to free the floating body 12 and put the chuck 4 in a floating state (step 4).

On the other hand, when the chuck 4 is used in the floating state, the workpiece 2 is chucked in the unloaded state while the floating body 12 is in the free state (step 5). Then, the position at that time is set to the reference position (dx, d
y) is stored in the storage unit 32 (step 6). The reason why the work 2 is chucked in the unloaded state is that the position when the work 2 is actually chucked is slightly changed if the work shape or the like is different. After storing the reference position (dx, dy), it is judged whether or not the work 3 to be inserted moves due to the reaction force of the chuck operation (step 7), and if it does move, it is impossible to teach an accurate position. , Workpiece 3 to be inserted
Is fixed (step 8).

Then, the chuck 4 is moved to a position where the workpiece 2 can be gripped (JOG) (step 9).
Here, the jog movement of the chuck 4 is sufficient to move to a rough position where the workpiece 2 already fitted to the inserted workpiece 3 can be gripped within the movement range of the floating body 12, It is not necessary to determine the position of the work 2 in. After roughly aligning the positions of the chuck 4 and the work 2, the work 2 is gripped by the chuck 4 (step 1
0). When the center position of the chuck 4 is deviated from the center position of the work 2 due to the chuck of the work 2, the floating body 12 moves and the center positions of the two are aligned. The position (dx ', dy') of the chuck 4 at this time is detected by the distance sensors 21 and 22 and is taken into the teaching means 30 (step 11). The present position data (dx ', dy') of the chuck 4 and the reference position (dx, d)
y) and the amount of jog movement in the robot coordinate system (Jx, J
y) is used to calculate the true chuck position (X, Y) by the arithmetic unit 31 of the teaching means 30 based on the mathematical formula 1 (step 11).

[0021]

## EQU00001 ## X = Jx + (dx-dx ') Y = Jy + (dy-dy') That is, the jog, which is the amount of movement of the arms 5 and 6 supporting the chuck 4 via the floating body 12, on the robot coordinate system. The sum of the displacement (Δx, Δy) between the chuck position when the work 2 is chucked and the center position of the work 2 when the work 2 is actually fitted to the inserted work 3 is added to the movement amount. It becomes the true chuck position (X, Y). Therefore, this true chuck position (X, Y) is used as the teaching point.

Then, it is judged whether or not the teaching point is confirmed (step 13), and if necessary, the chuck 4 is actually moved to the chuck position (X, Y) (step 15). Then, the workpiece 2 inserted into the inserted workpiece 3 is chucked (step 16). Then, it is determined whether or not the chuck position is acceptable, that is, whether or not the teaching point is acceptable (step 1
7). This judgment is made by, for example, visual inspection of the operator or when the work 2 is chucked by the distance sensors 21 and 22.
It can be determined whether or not the measured distance value of No. 1 matches the position data (dx ', dy') at the time of chucking obtained in step S11.

When the position data (X, Y) is determined to be defective (step 17), the process jumps to step 11 before. Then, the chuck position (dx ', dy') at the time of chucking the work is again taken in (step 11), and a new true chuck position (X, Y) is calculated again (step 12). Then, it is judged whether or not the chuck position (X, Y) is to be confirmed (step 13), and if the confirmation is necessary, the above operation is repeated again.

The true chuck position (X, Y) is stored in the storage unit 32 as a teaching point (step 1
After 4), it is determined whether or not the teaching work is completed (step 18). If not completed, the process returns to step 9 and the second position setting operation is performed. When it is necessary to teach the robot another position, the robot jumps to the step 9 and repeats the teaching work from the step 9 to the step 18. For example, the above description is for work 2.
Although the teaching of the position where the work 3 to be inserted is fitted is performed, the position where the work 2 is received may be taught. When finishing the teaching work,
At the time of work, it is judged whether or not the chuck 4 is to be floated (step 19). If the chuck 4 is not to be floated, the floating body 12 is fixed by the fixing fittings 16 and 16 (step 20), and then the teaching work is ended.

In the above description, the rotation of the floating body 12 in the horizontal plane is not considered. However, when the floating body 12 moves freely, rotation may occur. This rotation occurs when a rotational force is generated in the floating body 12 due to, for example, the gripping force of the chuck 4 with respect to the workpiece 2 and the tension difference between the springs 15 ,. The rotation of the top plate 12a is determined by the position (dx, d
In relation to y), an error occurs between the measured distance of the position sensors 21 and 22 and the actual position. However, this measurement error is actually a small value, and the effect can be practically ignored. Further, when high accuracy is required, this can be almost prevented by paying attention to the presence or absence of rotation during the teaching work, and correcting the rotation and correcting the position measurement value (steps 11 to 16).

If higher accuracy is required, the following means will be taken. (1) A tachometer is provided on the floating body 12. For the tachometer, for example, an encoder, a rotational displacement meter using a spring and a strain gauge, or the like is used. Then, the position is corrected according to the rotation angle. (2) The distance sensors 21 and 22 in the X and Y directions are two in number, that is, four in total. The two sensors are provided with a predetermined interval, and the rotation angle is detected and the position data is corrected by the difference in the measured distance between the two sensors in the X and Y directions. (3) Rotation of the floating body 12 is prevented by a mechanical structure such as a linear guide.

As described above, the chuck 4 is provided with play during teaching, and the amount of work is greatly increased by correcting the amount of change between the reference value (dx, dy) and the actual chuck position (dx ', dy'). Can be relaxed.

The above-described embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, although the teaching means 30 is configured separately from the robot controller 33 in the present embodiment, the outputs of the sensors 21 and 22 of the chuck position detecting means 20 are directly input to the robot controller 33 via the interface to make the robot controller 33. It may be processed by the arithmetic unit and the storage unit configured inside. That is, the CPU in the robot controller 33 is controlled by the teaching processing program shown in the flowcharts of FIGS.
The or memory is caused to function as the arithmetic unit 31 or the storage unit 32 described above. Further, the floating mechanism of the floating means 10 is not particularly limited to the support by the balls 13 described above, and other methods such as fluid support can be used. Further, the detection of the chuck position is not limited to the case of measuring the position of the floating body 12, and the end surface of the chuck 4 may be directly measured.

[0029]

As is clear from the above description, the articulated robot of the present invention is a floating means interposed between the arm and the chuck so that the chuck can freely move in the horizontal plane when teaching the arm to the arm. And a chuck position detection means for detecting the position of the chuck with respect to the arm, and a deviation between the chuck position when the workpiece is chucked in the floating state and no load and the chuck position when the workpiece installed at the movement target position is chucked. The teaching means is used to teach the robot control section by finding the true chuck position on the robot coordinate system by adding the arm jog movement amount to this and teaching target in the teaching work. Even if you do not align the position precisely, you can get an accurate target position just by roughly adjusting it. Constant is possible. Therefore, the teaching work becomes easy and the required time can be greatly reduced.
For example, the teaching work, which conventionally takes 1.5 days or more even by a skilled person, can be completed by an unskilled person in 2 to 3 hours.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing a floating means, a chuck position detecting means and a teaching means, which are essential parts of an articulated robot of the present invention.

FIG. 2 is a transverse sectional view conceptually showing the structure of a floating means portion in FIG.

FIG. 3 is a vertical cross-sectional view conceptually showing an example of a fixture.

FIG. 4 is a perspective view showing an example of the overall appearance of an articulated robot of the present invention.

FIG. 5 is a part of a flowchart for explaining a teaching work.

FIG. 6 is the rest of the flowchart for explaining the teaching work.

[Explanation of symbols]

 1 Articulated Robot 2 Work 3 Inserted Work 4 Chuck 5, 5 Arm 10 Floating Means 11 Fixed Body 12 Floating Body 16 Fixing Metal 20 Chuck Position Detecting Means 21, 22 Distance Sensor 30 Teaching Means

Claims (1)

[Claims] 1. A multi-joint robot having a chuck and having an arm capable of rotating in a horizontal plane, and rotating the arm between a plurality of positions to move a work held by the chuck to a target position. Between the chuck and the chuck to allow the chuck to freely move in a horizontal plane when teaching the arm with respect to the arm, chuck position detecting means for detecting the position of the chuck with respect to the arm, and a floating state. The robot coordinate system is obtained by obtaining the deviation between the chuck position when the workpiece is chucked in the unloaded state and the chuck position when the workpiece installed at the movement target position is chucked, and adding the jog movement amount of the arm to this. Teaching means to find the true chuck position above and teach it to the robot controller An articulated robot characterized by consisting of: