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Browse Prior Art Database

Data Driven Precise Placement Algorithm

IP.com Disclosure Number: IPCOM000107530D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Colson, JC: AUTHOR [+2]

Abstract

Disclosed is a method for achieving highly accurate placement of objects on planar objects, based on CAD data and calibration data only. Also, disclosed is a method for computing and utilizing arbitrarily positioned fiducials for determining linear distortions and computing relative transformations. Also, by means available to one skilled in the art, a method is presented for improving the accuracy of the aforementioned placement method by viewing a fiducial during the inspection of the object to determine the actual error of the robot due to repeatability. Finally, by means available to one skilled in the art, a method is presented for an extension of the algorithm to handle placement of objects on target objects in three dimensions by utilizing three-dimensional transformations and sensing devices.

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Data Driven Precise Placement Algorithm

       Disclosed is a method for achieving highly accurate
placement of objects on planar objects, based on CAD data and
calibration data only.  Also, disclosed is a method for computing and
utilizing arbitrarily positioned fiducials for determining linear
distortions and computing relative transformations.  Also, by means
available to one skilled in the art, a method is presented for
improving the accuracy of the aforementioned placement method by
viewing a fiducial during the inspection of the object to determine
the actual error of the robot due to repeatability.  Finally, by
means available to one skilled in the art, a method is presented for
an extension of the algorithm to handle placement of objects on
target objects in three dimensions by utilizing three-dimensional
transformations and sensing devices.

      The invention is a method for calibrating a placement system,
and utilizing the calibration data along with Computer Automated
Design (CAD) system data to perform the placement task.  The only
assumptions for this method are 1) that the repeatability of the
transfer device at the inspection device is smaller than the required
accuracy of the placement, and 2) that the object to be placed is
held relative to the transfer device in a constant position and
orientation between inspection and placement points.  The algorithm
works by performing two-dimensional transformations on collected data
to determine accurately the locations of both the inspected object
and the target object.

      This method is currently implemented in AML/2*, utilizing an
IBM SCARA robot, model 7575, as the transfer device.  The fine
positioning is achieved using an XY table, and sensing is done with
vision systems.

      During calibration, two-dimensional transformations relative to
the XY table are obtained for a first camera at the place location
and at the inspect location, and for a second camera (which is fixed
at the inspect location).  The data f...