Browse Prior Art Database

Aligning an Optical Sensor Automatically for any Teach Applications

IP.com Disclosure Number: IPCOM000113419D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Ellis, JF: AUTHOR [+5]

Abstract

In any teach application using an optical sensor (automated tape library in this case), the exact beam location to guide a robot arm to a correct physical location is unknown. The beam can deviate from its nominal location by a significant amount. This is a major teach problem, since the teach will not be reliable enough to run the machine with no errors. This article will describe a method to solve this problem in situations when the tool on the robot arm (a gripper in this case) is capable of physically sensing an edge.

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Aligning an Optical Sensor Automatically for any Teach Applications

      In any teach application using an optical sensor (automated
tape library in this case),  the exact beam location to guide a robot
arm to a correct physical location is unknown.  The beam can deviate
from its nominal location by a significant amount.  This is a major
teach problem, since the teach will not be reliable enough to run the
machine with no errors.  This article will describe a method to solve
this problem in situations when the tool on the robot arm (a gripper
in this case) is capable of physically sensing an edge.

      An automated way to align the sensor was developed to solve the
teach problem.  The solution is to calculate the distance between the
optical sensor beam and the center of the gripper, and then use that
calculated distance as an offset between the beam and the center of
the gripper.  Now every time the sensor is used to teach a position
(target) it is known exactly where the center of the gripper is.

      To do this a hardware fixture was designed with precisely
located horizontal and vertical edges.  The following steps are
followed to calculate the offsets between the sensor beam and the
gripper:

o   The sensor is used to find the top edge of the target on the
    fixture.

o   The sensor is used to find the left edge of the target on the
    fixture

o   The two values are stored.

o   Using "dog bone" on the gripper, the right edge of th...