Kinematic calibration of parallel manipulators

Identification objective functions considering end effector pose errors and loop closure (branch end distance) errors for the calibration of parallel manipulators are discussed. Based on the elimination of the need for fixturing devices, loop closure error based objectives are demonstrated preferred. Kinematic calibration models for the RSI 6 degree of freedom hand controller including device geometric parameters are introduced. Calibrations considering more complete models are demonstrated to yield improved calibrations in comparison to models considering only original length, angle, and potentiometer parameters. To achieve higher precision, it is concluded that noise-free joint displacement sensing, and accurate passive spherical branch end joints are required