CA1181837A

CA1181837A - Industrial robot

Info

Publication number: CA1181837A
Application number: CA000415857A
Authority: CA
Inventors: Yutaka Kitano; Yoshimasa Itoh
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1981-11-20
Filing date: 1982-11-18
Publication date: 1985-01-29
Also published as: GB2110427A; GB2110427B; DE3243341A1; JPS5887603A; DE3243341C2

Abstract

TITLE OF THE INVENTION:

INDUSTRIAL ROBOT

ABSTRACT OF THE DISCLOSURE:

A teaching-playback type industrial robot comprises a memory for storing a working program, a manipulator having a sealing nozzle at the top end thereof and positioning the nozzle relative to a work piece based on the working program, a television camera for receiving an image projected on the surface of the work piece, a motor for positioning the top end of the nozzle in accordance with the image signal from the television camera upon playback operation, and conveyor for moving the manipulator to set the top end of the nozzle to the reference position of the work piece.

Description

~ t7 This invention concerns an industrial robot.
In a case where sealing, coatiny, welding or like other working is applied to a work piece using a so-called teaching-playback type robot, those portions of the work piece to be applied with the working have to be situated accurately ¦ upon a playback operation where a teachi.ng operation was executed.
However, in the case where each of work pieces is ' transported successively by a belt conveyor and applied with 10 1, sealing, coating, welding or like other working during the transportation, the operation for situating all of the work ! pieces, relative to the robot manipulator, accurately where the teaching operation was executed is time consuming and difficult. ¦
In addition, even if each of the work pieces can be situated accurately relative to the robot manipulator at the position where the teaching operation was executed, it still leaves some undissolved problem, since the portions to be worked of each of the work pieces, that is, the positions of the portions l to which working is to be applied actually are somewhat varied 20 11 even for the work pieces of an identical formO This problem I¦ itself can substantially be solved in a robot having a detection I device provided to the manipulator for detecting the portions i to be worked and adapted to perform playback operation while .~ applying positional correction which is performed by rotating or swinging a sealing nozzle, spray nozzle or welding torch based on a detection signal from the detection device to bring .

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the top end thereof to the portions to be worked. However, if the position control for the top end of the nozzle or torch to the portions to be worked i5 effected by a large amount of operation for the positional correction, it may some time fail to obtain satisfactory sealing, coating or welding with respect to the resolution and the response of the detection device.
An object of this invention is to provide an industrial robot capable of performing satisfactory working even when the positions where the work pieces are situated upon play-back operation and/or positions of the portions of the workpieces to be worked differ from each other.
According to the present invention, there is provided an industrial robot comprising a memory means for storing a working program, a manipulator means provided with a tool means at the top end thereof, said manipulator means being adapted to position said tool means relative to a work piece in accordance with the working program stored in said memory means, a detection means provided on said manipulator means for detecting the portion of a work piece to be worked, a correcting means for correcting the position of said tool means relative to said portion to be worked based on detection signals from said detection means and a conveying means for conveying said manipulator means based on the detection signals of said detection means concerning a reference position of said work piece so as to set said tool means to the reference position.
Certain preferred embodiments of the invention are illustrated by the attached drawings in which:
Fig. 1 is a side view for a preferred embodiment of this invention, ,3~3t~

Fig. 2 is a plan view for the embodiment shown in Fig. l;
Fig. 3 and Figc 4 are perspective views for the detaîls of a wrist and its relevant portions, Fig. 5 and Fig~ 6 are explanatory views for the images of slit received by a television camera, and Fig. 7 is a block dia~ram for explaining the operation of the embodiment shown in Fig. lo 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 to the platform 2 in the direction of an arrow A, a support post 5 pivotal to the table 4 in the direction of an arrow B, an arm 6 pivotal to the support post 5 in the direction of an arrow C and a freely bendable wrist 7 of a so-called flexible type. The manipula~or 1 of such a constitution has been described specifically in U.S. Patent No.
4,420,812 and No. 4,385,358 and the details of the wrist 7 are described in DE-OS 3,202,076.
A bracket 9 is secured to a cylindrical top end of the wrist 7 and another bracket 12 is provided by way of a connecting member 10 to the bracket 9 pivotally around an axial line 11. To the bracket 12, are secured a slit light source 16 for project-ing a slit image 15 to 2 surface 14 of a work piece .~

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1 ' 13 to be worked, a television camera 17 using semi-conductor image sensors or the like for receiving the slit image 15 on ij 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 ¦j on side projections 20 and 21 of the bracket 9. A sec-tor 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 10 1 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 o~ 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 1¦ in perpendicular to ~he rotational axial line 11. An optical axis 27 of the slit light source 26 intersects obliquely the op-tical 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 2~ of the wor~
piece 13 to be sealed, a nozzle holder 32 which resiliently 'i .
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,~ supports the nozzle 31 displacea~ly in the direction along i ¦¦ the sealing direction shown ~y an arrow D and in the direction crossing this direction and a member 33 for securing tne nozzle 'l 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 a.nd 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 jl carried on a conveying device 34 comprising an endless chain conveyor and the manipulator 1 is conveyed by the running of the i 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 di.rection 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 I¦ 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 ll l i1 ''.
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accordance with the control program and operates the arm 3 of the manipulator 1 based on the ~eaching data ~hus 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 U.S.
Patent Nos. 4,420,812 and 4,385,358 referred to above.
The image processing device 40 compares the images re-ceived 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 GB 2,088,095A.
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 pre-determined p~sition 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 c ~37 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 axe 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 ' i ~

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jl operated under the control of the control device 37 in such a way that the manipulator 1 is moved in the same direction as 1~ the moving direction of the work piece 13 in the direction E in ¦l a synchronized manner. That is, the manipulator 1 and the work ¦I 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 Il of the slit 15 received by the television camera 17. If the 10 I light source 16, the television camera 17, the tool 18 and the sealed portion 29 of the work piece 13 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 Il 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 lmages 55 of the images 54 ~ corresponding to the slit 15, the distance 58 in the direction il F between the position 56 for the bent portion resulted at the step of the sealed portion 29 and the central position 57 for ~I the image 54 represents the deviation in the direction F
il between the top end 28 and the portion 29 to be sealed. In 'I a case where the images 53 are obtained in the television !!
!I camera 17, the control device 37 of the robot 50 directly l! actuates the arm 3 to move the top end 28 in the direction D
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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 5~ 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 manupulator 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 2~ 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 displace- !
ment 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 ., .

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1, I I , 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 .

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li 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 por~ion. In this case, a detection device capable of detecting such curved portion is mounted at ~he top end of the wrist 7 and both of the conveying de~ices 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 de~ice. ~urthermore, 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 13. 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 de~ices 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 compensat~
¦ ed, the displacement of the portion to be worked itself can not be compensated with ease. ~ccordingly, it is preferred to i l ll I , 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~
Thus, it will be seen that the robot of this invention is capable of decreasing the amount for the positional correction during playback operation and thereby enabling the use of a correction device with a narrower operation range. It is also capable of performing the correcting operation rapidly and applying working accurately to the portions being worked.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

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

2. The industrial robot of claim 1 in which the convey-ing means is adapted to set the manipulator means at a beginning of a playback-operation to the same relative position between the manipulator means and the work piece as that in the case where said tool means is set to the reference position on the teaching-operation.

3. The industrial robot of claim 1, in which the detec-tion means comprises a television camera for receiving an image projected on the work piece.

4. The industrial robot of claim. 2, in which the detec-tion means comprises a television camera for receiving an image projected on the work piece.

5. The industrial robot of claim 3 or claim 4 in which the detection means is adapted to compare the image received by the television camera with reference image previously stored.

6. The industrial robot of claim 1 or 2, in which the manipulator means comprises an arm and a platform for rotatably supporting said arm, and said platform is provided on the conveying means.

7. The industrial robot of claim 1 or 2, which further comprises a conveying means for conveying the work piece, and a conveying means for conveying the manipulator means in the same direction as the conveying direction of the work piece conveyed by said conveying means for conveying the work piece.

8. The industrial robot of claim 1 or 2, in which the reference position is set to the portion to be worked of the work piece.