An integrated system of detecting end-effector motion states and wafer stick-slip on a wafer transfer robot

The online detection of end-effector motion states and wafer stick-slip on a wafer transfer robot is crucial in accessing the quality of trajectory planning and improving the performance of robotic control system. This paper presents a new integrated system for detecting end-effector motion states (position and velocity) and wafer stick-slip on a wafer transfer robot. The system mainly contains a custom-built position-sensing-detector (PSD) camera, an inertial module and a tactile sensor. The end-effector position measurement is achieved by the PSD camera, and the end-effector velocity is estimated by using a kinematic Kalman filter (KKF). The KKF fuses the outputs from the PSD camera and the inertial sensor with a tri-axis accelerator and a tri-axis gyroscope. The wafer stick-slip detection is built on the measurements of the electromagnetic-based tactile sensor. The experimental results show that the integrated system is capable of measuring the position with a repeatability of ± 0.023mm along the X-axis and ± 0.017mm along the F-axis, remarkably improving the accuracy of velocity measurement, and online detecting wafer stick-slip on the wafer transfer robot.