An Actuation Acceleration based Kinematic Modeling and Parameter Identification Approach for a six-DOF 6-PSU Parallel Robot with Joint Clearances

The 6-prismatic-spherical-universal (6-PSU) parallel robot is useful for high-accuracy positioning, where the motors are installed on the robot base and the moving parts of the robot have low inertia. A highly accurate kinematic model of the robot is fundamental for the control. The joint clearances of all limbs often exist and have a significant influence on kinematic model accuracy. In this study, an actuation acceleration information based kinematic modeling and identification method for a 6-PSU parallel robot with joint clearances is proposed. The direction of the joint clearance is related to the direction of the force acted on the joint, which is determined by the acceleration of the prismatic actuator. The existence of joint clearances is equivalent to the link length change. The joint clearances are identified from the experiments and compensated. Simulations and experiments show that the proposed method is effective and improves the accuracy of the kinematic model.