Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
1998-08-21
2001-01-16
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C073S001790
Reexamination Certificate
active
06175413
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the field of robotics systems, and in particular, to the calibration of a robotics system by projecting a laser through the holes of a plate onto a laser detection surface from a plurality of calibration positions.
2. Statement of the Problem
Robotics systems are required to position objects relative to one another with extreme precision. In the field of complex circuitry testing, robotics systems must be able to position test probes within 0.001 of an inch of a point on a printed circuit board. Robotics systems are comprised of mechanical components, electrical components, and software components. These components each operate within individual tolerances that result in errors. The errors combine to degrade overall system performance when positioning objects. The robotics system can be designed so the combination of errors does not exceed the overall system tolerance, but this design technique is a complex undertaking. The resulting robotics system generally operates somewhere under the tolerance, but the actual accuracy of the robotics system is not measured and remains unknown.
An operational robotics system is difficult to calibrate when the robotics system fails to meet the overall system tolerance. System failure often results from a complex combination of non-linear errors. For example, software components round numerical values. Servo control electronics have imperfect response characteristics at various frequencies. Mechanical components lose performance when extended to more distant operating areas. Together, the combination of these errors is difficult to analyze and control when attempting to bring an entire robotics system within an overall system tolerance.
Prior techniques for calibrating a robotics system fail to measure the precision performance of the robotics system when it actually positions objects in an operational area. These systems also fail to generate corrective factors to correct repeated positioning errors. The systems also fail to incorporate the correction factors into the robotics system to improve precision performance in the field.
SUMMARY OF THE SOLUTION
The invention overcomes the problems discussed above by providing a system and method for calibrating a robotics system. The invention measures the actual performance of the robotics system when positioning objects at several calibration positions within an operational area. The invention then determines corrective factors based on the performance measurements. The robotics system uses the corrective factors to overcome positioning errors and operate in the filed with the extreme precision.
The calibration system comprises a control system, a laser projection device, a plate, and a laser detection device. The robotics system initially positions the laser projection device to project a laser beam through a hole in the plate and onto a laser detection area on the laser detection device. The control system then directs the robotics system to move the laser projection device to a plurality of calibration positions. At a first group of the calibration positions, the laser projection device projects the laser beam through the hole and onto the laser detection surface. At a second group of calibration positions, the laser projection device projects the laser beam onto the plate and not through the hole. The laser detection device detects the laser beam on the laser detection surface when the laser beam is projected through the hole, and detects that the laser beam is not on the laser detection surface when the laser beam is projected onto the plate. The laser detection device provides information indicating the presence or absence of the laser beam to the control system. The control system determines a corrective factor for the robotics system based on the calibration positions and the information provided from the laser detection device.
The calibration technique can be repeated for a grid of holes and at a variety of distances above the holes. As a result, the invention generates corrective factors for the robotics system over a large operational area. The corrective factors can be incorporated into the robotics system to provide precision positioning performance in the field.
REFERENCES:
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patent: 5198876 (1993-03-01), Takashi
patent: 5353111 (1994-10-01), Freese
patent: 0 304 307 A2 (1989-02-01), None
patent: 0 747 719 A1 (1996-12-01), None
patent: 2 601 443-A1 (1988-01-01), None
patent: 2 669 257-A1 (1992-05-01), None
patent: WO96/30171 (1996-10-01), None
Duft, Graziano & Forest, P.C.
Proteus Corporation
Rosenberger Richard A.
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