GB2110427A

GB2110427A - Industrial robot

Info

Publication number: GB2110427A
Application number: GB08233052A
Authority: GB
Inventors: Yutaka Kitano; Yoshimasa Itoh
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1981-11-20
Filing date: 1982-11-19
Publication date: 1983-06-15
Also published as: GB2110427B; DE3243341A1; CA1181837A; DE3243341C2; JPS5887603A

Abstract

An industrial robot has a memory for storing a working program, a manipulator 3 with a tool 28 at its free end thereof for positioning said tool relative to a work piece in accordance with a working program stored in said memory, and a detector on the manipulator for detecting the portion of a work piece 13 to be worked. A correcting means corrects the position of a said tool, in use, relative to said portion to be worked based on detection signals from said detection means, and conveying means moves the manipulator in dependence on detection signals from said detector concerning a reference position of the work piece, so as to set the tool to the reference position. <IMAGE>

Description

SPECIFICATION Industrial robot This invention relates to an industrial robot.

In a case where a sealing, coating, welding or similar operation is to be performed on a work piece using a so-called teaching-playback type robot, those portions of the work piece to be worked on have to be situated accurately, upon a playback operation, where a teaching operation was performed.

However, in cases where the work pieces are transported successively by a belt conveyor and worked on during the transportation or between steps thereof, the operation of situating the work pieces accurately relative to the robot manipulator is time consuming and difficult. In addition, even if each of the work pieces could be situated accurately relative to the robot manipulator at the position where the teaching operation was executed, there would remain the problem that the portions to be worked on are in practice somewhat varied in position within the work piece even for work pieces of a nominally identical form.This problem itself can generally be solved in a robot having a detection device provided on the manipulator for detecting the portions to be worked on, and adapted to perform playback operation while applying a positional correction which is performed by rotating or swinging a sealing nozzle, spray nozzle or welding torch and so forth. The correction is based on a detection signal from the detection device to bring the top end thereof to the portions to be worked. However, if the position control for the top end of the work tool requires a large amount of positional correction, it may sometimes be that the tool fails to perform properly in terms of the resolution and the response of the detection device.

An aim of this invention is to provide an industrial robot capable of performing satisfactory working despite variations in the positions where the work pieces are situated upon playback operations and/or the positions of the portions of the work pieces to be worked.

According to the present invention there is provided an industrial robot including a memory for storing a working program, a manipulator arranged to have a tool at a free end thereof for positioning said tool relative to a work piece in accordance with a working program stored in said memory, a detection means provided on said manipulator for detecting the portion of a work piece to be worked, a correcting means for correcting the position of a said tool, in use, relative to said portion to be worked based on detection signals from said detection means, and conveying means for moving said manipulator based on detection signals from said detection means concerning a reference position of work piece, so as to set the tool to the reference position.

The invention provides an industrial robot capable of decreasing the amount of the positional correction needed during the playback operation and thereby enabling the use of a correction device with a narrower operation range. The robot of the invention can also perform the correcting operation rapidly and apply work accurately to the portions to be worked.

In order that the invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a side view of a preferred embodiment of this invention; Fig. 2 is a plan view of the embodiment shown in Fig. 1; Fig. 3 and Fig. 4 are perspective views showing details of the wrist of the illustrated embodiment and parts thereof; Fig. 5 and Fig. 6 are explanatory views of the images of a slit as received by a television camera; and Fig. 7 is a block diagram for explaining the operation of the embodiment shown in Fig. 1.

In the drawings, a multi-joint type robot main body or manipulator 1 comprises a platform 2 and a movable arm 3. The movable arm 3 comprises a turn table 4 pivotal relative to the platform 2 in the direction of an arrow A, a support post 5 pivotal relative to the table 4 in the direction of an arrow B, an arm 6 pivotal relative to the support post 5 in the direction of an arrow C and a freely bendable wrist 7 of the so-called flexible type. The manipulator 1 of such a constitution has been described in Patent Application No. 81.35006 and the details of the wrist 7 are described in Patent Application No. 81.35007.

A bracket 9 is secured to a cylindrical top end 8 of the wrist 7 and another bracket 12 is provided by way of a connecting member 10 to the bracket 9 to be pivotal around an axial line 11 (Fig. 3). To the bracket 12. are secured a slit light source 16 for projecting a slit image 15 to a surface 14 of a work piece 13 to be worked, a television camera 17 using semi-conductor image sensors or the likes for receiving the slit image 15 on the surface 14 and a tool 18. A rotatable shaft 19 positioned on the axial line 11 for supporting the bracket 12 pivotally to the bracket 9 is secured at its middle portion to the television camera 17 and pivotally supported at its both ends on side projections 20 and 21 of the brackets 9.A sector gear 22 is secured to one end of the rotatable shaft 19 and the gear 22 meshes with a gear 23, which is secured to an output shaft of a reduction gear 24.

The gear 24 is connected to a motor 25 of a good responsivity, such as a coreless motor, secured to the bracket 9. In response to the operation of the motor 25 as a correcting device, the slit light source 16, the television camera 17 and the tool 18 are integrally displaced rotationally around the axial line 11 in the direction of an arrow H.

A light-receiving optical axis 26 of the television camera 17 as the detection device is aligned with the axial center line for the cylindrical top end 8 of the wrist 7 and in perpendicular to the rotational axial line 11. An optical axis 27 of the slit light source 26 intersects obliquely the optical axis 26 and the rotational axial line 11.

The tool 18 comprises a sealing nozzle 31 which is in slight contact at its top end 28 with the surface 14 and supplies sealer material 30 from the top end 28 to a portion 29 of the work piece 13 to be sealed, a nozzle holder 32 which resiliently supports the nozzle 31 displaceably in the direction along the sealing direction shown by an arrow D and in the direction crossing this direction and a member 33 for securing the nozzle holder 32 to the bracket 12. The nozzle holder 32 can absorb the vertical error at the top end 28 upon playback operation. The nozzle 31 is in a plane including the axial lines 26 and 27, and the top end 28 of the nozzle 31 situates at the crossing point between the axial lines 26 and 27.

The platform 2 is carried on a conveying device 34 comprising an endless chain conveyor and the manipulator 1 is conveyed by the running of the chain of the conveying device 34 in the direction of an arrow F perpendicular to the direction of an arrow E in which the work piece 13 is conveyed by a conveying device 35. The conveying device 34 is carried on a conveying device 36 also comprising an endless chain conveyor and the conveying device 34, thus, the manipulator 1 is conveyed by the running of the chain of the conveying device 36 in the direction shown by an arrow G in parallel with the direction E. The conveying device 35 comprises, for example, an endless belt conveyor and conveys the works pieces 13 successively in the direction E.

As described later, a control device 37 comprising a microcomputer or the like stores the positional information for the arm 3 of the manipulator 1 into a memory unit 38 as the teaching data in accordance with a control program previously stored in the memory unit 38 upon teaching operation and reads out the teaching data stored in the memory unit 38 also in accordance with the control program and operates the arm 3 of the manipulator 1 based on the teaching data thus read out upon playback operation. The control device 37 also controls the operations of the conveying devices 34 and 36 and the conveying device 35 based on the signal from a detector 39 that optically or magnetically detects the approach of the work pieces 13, the signal from an image processing device 40 and the control program stored in the memory device 38.Details for the teaching and playback operations on the manipulator 1 are described in Patent Applications referred to above. The image processing device 40 compares the images received by the television camera 17 with reference images previously stored in a memory unit 41 and outputs a control signal based on the result of the comparison to the control device 37 and to the motor 25. Details for the image processing device 40 are disclosed in U.S. Patent Application Ser. No. 322375.

The operation of a multi-joint type robot 50 having thus been constituted is to be explained next. Upon teaching operation, running of the conveying device 35 is stopped and the work piece 13 is situated at a predetermined position on the belt of the conveying device 35. Then, the manipulator 1 is manually moved to the work piece 13 thus set stationary while bringing the top end 28 to the start point 51 for the sealing, setting the axial line 11 in parallel with the sealed line 29 as the portion to be worked, crossing the axial line 26 in perpendicular to the worked surface 14 and positioning the crossing point between the axial lines 26 and 27 to the start point 51. Thereafter, the top end 28 is displaced along the sealed line 29 to the end point 52 for the sealing while maintaining the positional relations as stated above.Each of the positions for the arm 3 while the top end 28 is being displaced from the start point 51 to the end point 52 are successively stored as the teaching data, that is, a working program into the memory unit 38 under the control of the control device 37. Each of the positions for the arm 3 can be detected, for example, by a potentiometer provided to each of the joints of the arm 3. Upon playback operation, the conveying device 37 is moved by the conveying device 36 in the direction opposite to the direction E and set to the initial position at the rightmost end in Fig. 2 under the control of the control device 37. Then, when the conveying device 35 is run by the operation start signal from the control device 37, the work pieces 13 are successively conveyed in the direction E.When the positional relation between the initial work piece 13 being conveyed and the conveying device 34 attains the same positional relation which has been set upon teaching operation, the teaching data stored in the memory device 38 are read out based on the signal from the detector 39 that detects the above situation optically or magnetically under the control of the control device 37, whereby the manipulator 1 is operated so that the top end 28 is set to the start point 51 by the teaching data and, while on the other hand, the conveying device 36 is operated under the control of the control device 37 in such a way that the manipulator 1 is moved in the same direction as the moving direction of the work piece 1 3 in the direction E in a synchronized manner. That is, the manipulator 1 and the work pieces 13 are moved in the direction E at the same speed. Then, when the top end 28 is situated to the start point 51, the image processing device 40 of the robot 50 inspects the images of the slit 15 received by the television camera 17. If the light source 1 6, the television camera 17, the tool 18 and the sealed portion 29 of the work piece 1 3 are in the same positional relation as that for the teaching operation, the camera 17 receives slit images 53 as a detection signal. While on the other hand, if the light source 16, the camera 17, the tool 18 and the sealed portion 29 of the work piece 13 are in the different positional relation from that for the teaching operation, the camera 17 receives, for example, slit images 54 as the detection signal.In the images 55 of the images 54 corresponding to the slit 15, the distance 58 in the direction F between the position 56 for the bent portion resulted at the step of the sealed portion 29 and the central position 57 for the image 54 represents the deviation in the direction F between the top end 28 and the portion 29 to be sealed. In a case where the images 53 are obtained in the television camera 17, the control device 37 of the robot 50 directly actuates the arm 3 to move the top end 28 in the direction D based on the indication signal from the image processing device 40 in such a way that the sealing working may be performed on the sealed portion 29 from the start point 51 to the end point 52 based on the teaching data.In a case if the images 54 are obtained in the television camera 17, the image processing device 40 outputs an indication signal based on the distance 58 to the control device 37 of the robot 50 and the control device 37 actuates the conveying device 34 to move the manipulator 1 in the direction F based on the indication signal from the image processing device 40 until the images 53 are obtained. When the images 53 are obtained as the result of the movement of the manipulator 1 in the direction F, the robot 50 starts the sealing for the sealed portion 29 in the same manner as described above. During sealing for the sealed portion 29 from the start point 51 to the end point 52 in accordance with the teaching data, the image processing device 40 monitors the slit images obtained from the television camera 17.If the slit images 54 are received in the course of the sealing due to the displacement of the sealed portion 29, the device 40 actuates the reversible motor 25 to rotate the light source 16, the camera 17 and the tool 18 around the axial line 11 in the direction H so that the slit image 53 can be obtained and positions the top end 28 to the sealed position 29. The distance 58 can be detected by comparing the received images 54 with the image 53 which are previously stored as reference images in the form of digital signals in the memory unit 41.When the sealing for the sealed portion 29 has been completed based on the teaching data, the control device 37 causes the conveying device 36 to stop the movement of the manipulator 1 in the direction E and, in turn, moves the manipulator 1 in the direction opposite to the direction E by the conveying device 36 to set the manipulator 1 to the initial position. When the manipulator 1 is set to the initial position, the robot 50 repeats the sealing in the same way to the next work piece 13 to be conveyed.

In this embodiment, explanations have been made for the displacement, in the direction F, of the portion to be worked such as the sealed portion 29 which extends in the same direction as the conveying direction E. In another case where the sealed portion 29 extends, for example, in the direction F, the optical source 16 is disposed so that the slit images 15 are formed on the surface 14 in perpendicular to the direction F and the moving speed of the manipulator 1 in the direction E may be adjusted properly by the conveying device 36 based on the slit images, whereby the top end 28 can accurately be set to the start point for the working with respect to the displacement of the sealed portion 29 either in the direction E or in the opposite direction.In the latter case, by mounting the bracket 9 to the wrist 7 so that the axial line 11 is in parallel with the sealed portion 29, the top end 28 can accurately track the portion from the start point to the end point to be sealed in the same manner as in the previous embodiment even if the portion to be sealed deviates in the direction E or in the opposite direction. The portion to be worked is not necessarily restricted only to the linear portion as described above but it may be a curved portion.

In this case, a detection device capable of detecting such curved portion is mounted at the top end of the wrist 7 and both of the conveying devices 34 and 36 are operated based on the detection signal from the detection device. At first, the top end 28 is set to the reference position for the portion to be worked and, during the working for the portion to be worked according to the teaching data, the top end 28 may be followed after the displacement of the portion to be worked by the actuation of the conveying devices 34 and 36 based on the detection signal from the detection device.

Furthermore, although the reference position is set to the working start point for the work piece, the reference position may alternatively be set to a corner 59 of the work piece 1 3. In this case, the images for the corner 59 are stored in the memory device 41 upon teaching operation. Upon playback operation, the top end 28 is situated at first to the corner 59 to obtain the images thereof and the images thus obtained are compared with the stored images to detect the displacement of the work piece 13, and the conveying devices 34 and 36 may be actuated so as to compensate the displacement on the manipulator 1. In this case, while the displacements for each of the work pieces 13 on the conveying device 35 can desirably be compensated, the displacement of the portion to be worked itself can not be compensated with ease. Accordingly, it is preferred to set the reference position at the portion to be worked in the case where the portions to be worked are somewhat different for each of the work pieces 13. Furthermore, this invention can be applied not only to the robot for sealing working but also to those robots for welding or coating working in which suitable tool can be selected depending on the types of the working, that is, a welding torch for the welding and a paint spray nozzle for the coating respectively.

Claims

1. An industrial robot including a memory for storing a working program, a manipulator arranged to have a tool at a free end thereof for positioning said tool relative to a work piece in accordance with a working program stored in said memory, a detection means provided on said manipulator for detecting the portion of work piece to be worked, a correcting means for correcting the position of a said tool, in use, relative to said portion to be worked based on detection signals from said detection means, and conveying means for moving said manipulator based on detection signals from said detection means concerning a reference position of work piece, so as to set the tool to the reference position.

2. An industrial robot according to claim 1, in which the detection means includes a television camera for viewing an image projected on the work piece.

3. An industrial robot according to claim 2, in which the detection means is adapted to compare the image as viewed by the television camera with a reference image previously stored.

4. An industrial robot according to claim 1,2 or 3, in which the manipulator includes an arm and a platform rotatably supporting said arm, said platform being provided on the conveying means.

5. An industrial robot according to any preceding claim, including a further conveying means for conveying the work piece effective in the same direction as the conveyor for the manipulator.

6. An industrial robot according to any preceding claim, in which in use the reference position is set to the portion to be worked of the work piece.

7. An industrial robot constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.