# US 4,970,370 A · Track control method for a robot

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- Number: US 4,970,370 A
- Document ID: US4970370A
- Status: Granted
- Kind: A
- Application number: 07/315,684
- Filed: 1989-02-14
- Granted: 1990-11-13
- Earliest claimed: 1987-08-04
- Assignees: Fanuc Corporation
- Inventors: Ryuichi Hara
- Web page: https://patentgrep.com/patent/US4970370A

## CPC

- G05B 19/42: Recording and playback systems, i.e. in which the program is recorded from a cycle of operations, e.g. the cycle of operations being manually controlled, after which this record is played back on the same machine
- G05B 19/425: Teaching successive positions by numerical control, i.e. commands being entered to control the positioning servo of the tool head or end effector
- G05B 2219/36446: Keep tool stationary, move workpiece
- G05B 2219/36458: Teach only some points, for playback interpolation between points
- G05B 2219/45104: Lasrobot, welding robot
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

There is provided a track control method for a robot, in which a welding operation can be executed by moving a workpiece along a predetermined track, with respect to a fixed welding torch. The welding torch (1) is disposed fixedly, while the workpiece (W) is held by means of a robot hand. Before starting the welding operation, the workpiece is located at each target point (a1, a2), and a workpiece coordinate position (T1, T2) corresponding to a hand operating position, at each target point, is taught. During the welding operation, a playback function of the robot is utilized for driving various robot operating sections, including robot arms and a robot hand, so that positions to which the workpiece is moved are coincident with a series of calculated workpiece coordinate positions. Thereupon, the welding is performed along the predetermined track on the workpiece as the workpiece moves, despite the change of the position of the workpiece relative to the distal end of an arm (4).

## Claims

### Claim 1

A track control method for a robot for manipulating a workpiece, comprising steps of:
(a) fixing a point of operation in a reference coordinate system;
(b) positioning the workpiece so that each target point on a predetermined workpiece track is coincident with the point of operation;
(c) teaching an operating position of an end effector, relative to an end effector mounting portion, each time said positioning step (b) is completed; and
(d) driving the robot in accordance with the thus taught respective end effector operating positions.

### Claim 2

A track control method for a robot having a hand for manipulating a workpiece with respect to a fixed operating position, comprising the steps of:
(a) positioning the workpiece so that a target point on a predetermined workpiece track is coincident with the fixed operating position;
(b) teaching a hand position of the hand holding the workpiece after said positioning step (b) is completed;
(c) repeating said steps (a) and (b) until the workpiece has been positioned at each target point on the predetermined workpiece path; and
(d) operating the robot in accordance with the taught hand positions.

### Claim 3 (depends on 2)

A track control method as set forth in claim 2, wherein said step (d) comprises performing a welding operation while the robot hand moves the workpiece along the predetermined workpiece track.