IN-SITU CALIBRATION OF A REDUNDANT MEASUREMENT SYSTEM FOR MANIPULATOR POSITIONING

摘要

Achieving high positioning accuracy in a precision manipulator usually relies on calibration of its metrology system, i.e. the determination of reproducible geometry errors as represented by parameters in a metrology model, which is then used for position control. The issue of metrology calibration in the presence of external sensors, which can provide reliable information on the true spatial position of the manipulator's end-effector, is well understood. A problem arises, however, in the absence of such external sensors, when the manipulator's internal sensors, all of them encumbered with unknown geometry errors, provide the entire position information. Many high-performance manipulators feature a redundant metrology system. In such a system more spatial measurements are available than the number of degrees of freedom. This paper shows how that redundancy can be utilised to calibrate the manipulator in situ, i.e. without the use of external measurement systems.