Approximation of the center and radius of C-arm images for automatic on-line camera calibration

Abstract

This paper presents a new robot autonomous calibration method using a trigger probe. The robot grips a simple probe (which was manufactured as a standard end-effector tool) automatically to touch constraint planes in a workspace (the locations of the constraint planes are not necessarily known exactly). The robot internal sensor measurements are recorded for kinematic calibration while the tip-point of the probe is in contact with the constraint plane. The kinematic constraint conditions are obtained from the known shape of the constraint surface, rather than from the measured reference locations in a workspace. The new method eliminates any use of external measuring devices for robot end-effector location measurements for robot calibration; thus it is suitable for a periodic robot re-calibration in a shop-floor environment. Both simulation and experimental results for a six degree-of-freedom (DOF) PUMA robot are given in this paper. The evaluation results using an external precision measuring device — Coordinate Measuring Machine(CMM) — are also presented.