Through-beam auto teaching

Patent metadata

Field	Value
Publication number	US-11673275-B2
Application number	US-202016784193-A
Country	US
Kind code	B2
Filing date	Feb 6, 2020
Priority date	Feb 8, 2019
Publication date	Jun 13, 2023
Grant date	Jun 13, 2023

Abstract

A method of teaching a robot including providing a pin at a location within a work station, and the robot in an area adjacent to the station. The robot having an arm and an end effector that pivots. The end effector has a through-beam sensor including a light emitter and a light receiver to sense when an object is present therebetween. The robot is moved to perform sensing operations in which the sensor senses the pin, such operations are performed while a position and/or an orientation of the end effector are varied to gather sensed position and orientation data. The sensing operations are performed such that the pin is located at different distances between the emitter and the receiver as the robot moves the sensor across the pin. Calculations are performed on the data to determine the location of the pin with respect to a coordinate system of the robot.

First claim

What is claimed is:

1. A method of teaching an articulated robot, the method comprising:
providing a first pin at a first location within a work station;
providing the articulated robot in an area adjacent to the work station, the articulated robot having a coordinate system, the articulated robot having an arm and an end effector that is configured to pivot with respect to the arm, the end effector having a workpiece receiver with a first protruding member and a second protruding member, the end effector having a through-beam sensor including a light emitter provided on one of the first protruding member and the second protruding member, the through-beam sensor further including a light receiver provided on an other of the first protruding member and the second protruding member, the through-beam sensor being configured to sense when an object is present between the light emitter and the light receiver;
moving the articulated robot to perform sensing operations in which the through-beam sensor senses the first pin, the sensing operations being performed while a position and/or an orientation of the end effector are varied for each sensing of the first pin to gather sensed position and orientation data, the sensing operations are performed such that the first pin is located at different distances between the light emitter and the light receiver as the articulated robot moves the through-beam sensor across the first pin for a plurality of parallel movements of the end effector; and
performing calculations on the sensed position and orientation data to determine the first location of the first pin with respect to the coordinate system of the articulated robot,
wherein the plurality of parallel movements includes:
a first movement in which the articulated robot moves the through-beam sensor in a first direction along a first path entirely across the first pin, the first pin being at a first distance between the light emitter and the light receiver when the through-beam sensor is moved along the first path across the first pin;
a second movement in which the articulated robot moves the through-beam sensor in a second direction along the first path entirely across the first pin, the second direction being opposite to the first direction such that the second movement is a reverse movement to the first movement; and
a third movement in which the articulated robot moves the through-beam sensor in a third direction along a second path entirely across the first pin, the second path being parallel to the first path, the first pin being at a second distance between the light emitter and the light receiver when the through-beam sensor is moved along the second path across the first pin, the second distance being different from the first distance.

2. The method according to claim 1 ,
wherein the end effector is configured to pivot with respect to the arm about a pivot axis, and
wherein the method further comprises performing calculations on the sensed position and orientation data to determine a distance extending in a direction normal to a light beam of the light emitter to the pivot axis, and an angle of the direction normal to the light beam with respect to the coordinate system of the articulated robot including an angular error of the end effector.

3. The method according to claim 1 , further comprising:
providing an optical target on a pivot axis of the end effector that is configured to pivot with respect to the arm;
providing a scanning device at a fixed position with respect to the coordinate system of the articulated robot;
using the scanning device to measure positional data of the optical target as the articulated robot is moved through a range of motion; and
performing a regression analysis on the positional data to determine link lengths of links of the robot arm.

4. The method according to claim 3 , further comprising:
storing the link lengths on respective encoders of motors for rotating the links of the robot arm.

5. The method according to claim 1 ,
wherein the work station has a work location at a predetermined position and orientation with respect to the first location of the first pin, and
wherein the method further comprises using the first location of the first pin to determine the work location with respect to the coordinate system of the articulated robot.

6. The method according to claim 5 ,
wherein the work location overlaps the first location of the first pin in a horizontal plane.

7. The method according to claim 1 ,
wherein the articulated robot includes:
a base mounted in the area adjacent to the work station;
the arm includes:
a first arm member pivotally mounted to the base about a first pivot axis;
a second arm member pivotally mounted to the first arm member about a second pivot axis; and
a third arm member pivotally mounted to the second arm member about a third pivot axis; and

the end effector is pivotally mounted to the third arm member about a fourth pivot axis.

8. The method according to claim 1 ,
wherein sensing operations include:
a first sensing operation in which the articulated robot moves the through-beam sensor in a first linear motion across the first pin with the end effector in a first orientation; and
a second sensing operation in which the articulated robot moves the through-beam sensor in a second linear motion across the first pin with the end effector in the first orientation, and

wherein the first linear motion and the second linear motion constitute the plurality of parallel movements of the end effector.

9. The method according to claim 8 ,
wherein, in the first sensing operation, the first pin is a first distance between the light emitter and the light receiver when the through-beam sensor is moved across the first pin, and
wherein, in the second sensing operation, the first pin is a second distance between the light emitter and the light receiver when the through-beam sensor is moved across the first pin, the second distance being different from the first distance.

10. The method according to claim 8 ,
wherein sensing operations include:
a third sensing operation in which the articulated robot moves the through-beam sensor in a third linear motion across the first pin with the end effector in a second orientation, the second orientation being different than the first orientation; and
a fourth sensing operation in which the articulated robot moves the through-beam sensor in a fourth linear motion across the first pin with the end effector in the second orientation,

wherein the third linear motion and the fourth linear motion are parallel linear movements of the end effector, and
wherein the third linear motion and the fourth linear motion are non-parallel to the first linear motion and the second linear motion.

11. The method according to claim 1 ,
wherein the moving of the articulated robot to perform the sensing operations includes:
initially moving the end effector to a predetermined approximate location of the first pin; and
moving the end effector in an area around the predetermined approximate location of the first pin until the through-beam sensor senses the first pin.

12. The method according to claim 1 , the method further comprising:
providing a second pin at a second location within a work station;
moving the articulated robot to perform further sensing operations in which the through-beam sensor senses the second pin, the further sensing operations being performed while the position and/or the orientation of the end effector are varied for each sensing of the second pin to gather further sensed position and orientation data, the further sensing operations

Assignees

• Yaskawa America Inc
• Yaskawa Electric Corp

Inventors

• Rogers John Charles

Classifications

• B25J9/1692

  Calibration of manipulator · CPC title

• B25J19/021

  Optical sensing devices · CPC title

• G05B19/18

  Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form (G05B19/418 takes precedence) · CPC title

• B25J9/046

  Revolute coordinate type · CPC title

• B25J13/088

  with position, velocity or acceleration sensors · CPC title