Tolerance Design and Kinematic Calibration of a Four-Degrees-of-Freedom Pick-and-Place Parallel Robot

This paper presents a comprehensive methodology for ensuring the geometric pose accuracy of a 4DOF high-speed pick-and-place parallel robot having an articulated traveling plate. The process is implemented by four steps: (1) formulation of the error model containing all possible geometric source errors; (2) tolerance design of the source errors affecting the uncompensatable pose accuracy via sensitivity analysis; (3) identification of the source errors affecting the compensatable pose accuracy via a simplified model and distance measurements; and (4) development of a linearized error compensator for real-time implementation. Experimental results show that a tilt angular accuracy of 0.1/100 and a volumetric/rotational accuracy of 0.5 mm/+/- 0.8 deg of the end-effector can be achieved over the cylindrical task workspace.