Using a Laser Tracker to Actively Coordinate the Motion of a 3m Industrial Robot to Within 50 Microns: An ongoing effort to accurately determine and correct positioning errors.
David R. Novotny, Joshua A. Gordon, Jason B. Coder, Jeffrey R. Guerrieri, Michael H. Francis
We are using industrial-grade robotics guided by a metrology-grade laser tracker to perform antenna calibrations at mmWave frequencies. We are using a 3 m-reach robot to spherically scan a milli-meter Wave (mmWave) probe around an antenna under test (AUT) to determine gain, polarization and radiation pattern. In order to operate in at 500 GHz, knowledge of the mmWave probe (probe) position is required to within 15-20 m. The orientation of the probe must be normal to the scan surface (typ. within ~0.05) to minimize pointing errors. Our ability to accurately position the probe and our knowledge of the actual position and orientation determine the upper frequency limit of our measurement capability and directly affect the uncertainty of our measurements. Our first hurdle was to coordinate the timing and data collection between the controlling computer, the laser tracker and the external measurement equipment. To track a moving target at 25 mm/sec to within 15 m, we need timing accuracies better than 150 s. Our first functional tests showed base robot accuracy of 350 m and repeatability of ~40 m as measured by the laser tracker. We performed a first order correction to the original robot trajectory using measured data, and corrected the trajectory errors to within 35m. At this level of corrected positioning, the 15 m uncertainty of the laser tracker, is on the order of the robot error. We have shown that we can position the robot at the point of the laser trackers retro reflector and coordinate the external measurement equipment. We need to translate the position information from the target to the probe tip (using a 6 Degree-of-Freedom (DoF) sensor and non-contact methods for determining mmWave probe-to- 6 DoF sensor (sensor) offset), correct pointing errors in the probe, and define the coordinate system in the robot and tracker without touching the AUT. These must be addressed before the facility can be fully functional.
, Gordon, J.
, Coder, J.
, Guerrieri, J.
and Francis, M.
Using a Laser Tracker to Actively Coordinate the Motion of a 3m Industrial Robot to Within 50 Microns: An ongoing effort to accurately determine and correct positioning errors., Coordinate Metrology Systems Conference, San Diego, CA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914231
(Accessed July 31, 2021)