Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1998-03-13
2001-06-05
Cuchlinski, Jr., William A (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S064000, C700S086000, C700S166000, C700S186000, C700S253000, C700S255000, C700S259000, C700S262000, C318S568110, C356S370000, C356S370000, C219S124340
Reexamination Certificate
active
06243621
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to a system for determining the position of an object relative to a robot. More particularly, this invention relates to a device and method for determining the location, orientation and configuration of an object relative to a robot.
Robots have many industrial uses. One challenge associated with all robot operations is ensuring that the robot performs the desired operation accurately. A typical operation requires accurately locating a workpiece relative to the robot so that the robot moves into appropriate positions to perform the desired operations. A variety of methods have been suggested for locating a workpiece relative to a robot.
One method of locating a work piece relative to a robot includes “touching off” on various selected points of the workpiece. Typically, a touch-sensitive device is supported on the robot arm and robot position information is recorded when the sensing device contacts the workpiece. The robot information is then used to determine the location of the workpiece relative to the robot. An example of this method is disclosed in U.S. Pat. No. 4,590,578.
While the conventional touch sensing operation is useful, it is not without drawbacks and is not adequate for all situations. Typical touch sensing operations require that the workpiece be placed in a fixed position relative to the robot throughout the locating procedure. This is required because the reference frame of the robot relative to the workpiece becomes meaningless if the workpiece moves relative to the robot between touches during the location procedure. In many instances, the size of the workpiece or the workpiece configuration does not permit the robot to accurately determine all of the needed position or configuration information while using the conventional technique. It often is necessary or desirable to move the workpiece into various positions and/or orientations relative to the robot during the location procedure. With conventional techniques, this cannot be accomplished.
This invention addresses the need for determining the position, orientation and/or configuration of a workpiece while allowing the workpiece to be reoriented relative to a robot during a touch sensing procedure. With this invention it becomes possible to move a workpiece relative to the robot throughout the locating procedure, which represents a substantial advantage compared to the conventional technique.
SUMMARY OF THE INVENTION
In general terms, this invention is a method of determining a position of a workpiece relative to a robot that has a robot arm supported by a base and a sensor supported on the robot arm. The workpiece is supported on a positioner that is moveable relative to the robot. The method includes several basic steps. The positioner is oriented in a known orientation relative to the robot. The workpiece is then supported on the positioner such that the workpiece remains fixed relative to the positioner. The robot arm is then moved until the sensor contacts a first target point on the workpiece to locate the first target point relative to the robot. Then the positioner is moved into a second orientation to reorient the workpiece relative to the robot. Then the robot arm moves until the sensor contacts a second target point on the workpiece to locate the second target point relative to the robot. Depending on the requirements of a particular situation, the number of target points and workpiece orientations is varied. Finally, the position of the workpiece relative to the robot is determined using the locations of the first and second points that have been previously determined.
In the preferred implementation of this invention, the method includes defining a coordinated reference frame relative to the positioner. Each target point that is located relative to the robot is converted to be defined relative to the coordinated reference frame during the workpiece location procedure. This enables the workpiece to be moved into various orientations relative to the robot without negating the target point locations obtained prior to moving the workpiece.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as followed.
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Bolhouse Robert A.
Tao Jianming
Tsai Jason
Cuchlinski, Jr. William A
Fanuc Robotics North America Inc.
Howard & Howard
Marc McDieunel
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