Parameter Estimation and Calibration of Parallel Mechanism Based Robots

This paper deals with the calibration of a Hybrid Robot which is a combination of serial and parallel mechanisms having five degrees of freedom. In this paper, a new methodology has been introduced to determine the kinematics of such robots to ease the complexities. A reference frame has been defined on the moving platform which helps to bifurcate the hybrid mechanism for analysis. Calibration of the PKM is complex compared to serial robots because of the passive joints present in the PKM. The calibration of the parallel mechanism part of the hybrid robot has been presented here. Sensitivity analysis of the kinematic parameters of the PKM has been performed to identify the most significant parameters to influence change in the joint variable. Generalized calibration algorithm has been developed using the least square approximation method which requires less number of poses (only 8 poses). The calibration procedure presents an approach which does not involve any external measurement or calibrating devices. The experimental results are validated through a simulation model and hence can be effectively used to calibrate the hybrid robot.