Autonomous Kinematic Self-Calibration of a Novel Haptic Device

A closed loop self-calibration method for Delta mechanism and 3-RRR mechanism used in a double parallel haptic device was presented. This approach blocks successively one joint of each parallel mechanism using a simple lockup device and reforms the 3-DOF mechanism to be a 2-DOF one. The parameter errors of the mechanism are identified according to the differences between the sensor output of the redundant chain and nominal model output. Both the condition number and singular value of the error propagation Jacobian are synthesized as a new selection principle of calibration set such that the calibrating process is insensitive to the noise and the calibration precision is increased efficiently. Experiments show that the ratio of maximal error before and after calibrating is 9.6, namely, the setting accuracy of the two mechanisms are increased about 10 times and the error of re-position is less than 0.1 mm and 0.1deg