Application of Preshaping Control to a Semiconductor Wafer Transfer Robot and Experimental Verification

Abstract

In automated production of industrial products such as semiconductor wafers and liquid crystal panels, transfer robots are widely used for conveyance. Although high speed motion provides shorten cycle time residual vibration generally occurs. Thus, vibration control is needed to suppress the residual vibration. This paper presents an identification technique based on FFT and least-square approach and proposes to employ a preshaping approach to reduce the residual vibration. Firstly, we achieve good vibration suppression by applying this approach to angular velocity commands for the robot. However, using a preshaping approach in that way causes a change in the end-effector trajectory, which may result in collision of the semiconductor wafer with the processing equipment. For this reason, we apply the preshaping approach to end-effector velocity instead of joint angular velocity to maintain the original end effector trajectory, and then derive the angular velocity by using inverse kinematics. Hence, we can achieve cycle time reduction by vibration suppression under the exact tracking to the original trajectory.