Study Of End-effector Motion And Wafer Contact Status Detecting System For Wafer Transfer Robot

Integrated circuit (IC) industry is the core power in promoting economicdevelopment in which wafer transfer robot is the key manufacturing equipment.It’s rapidity and stability directly determines the efficiency of IC industry. Due to thecommon characteristics of serial non-direct drive robot, position feedback of thejoint motor can’t truly reflect the motion of robot ends. In addition, there existsstick-slip between end-effector and wafer due to acceleration and deceleration. Bothof them affect the stability, reliability, and efficiency of wafer transmission.According to the problems above, a sensing system to detect is needed.Supported by the national973sub-project “Principle and realization oftransferring large scale and super thin wafer with high efficiency and stabilizationunder complex environment”(granted No.2009CB724206), the topic carries out thestudy on a sensing system for the motion of wafer transfer robot ends and the wafercontact state. The solution for detecting the position, speed and wafer stick-slip isput forward. The sensing principles of each part are analyzed in detail. Eachdetection module is designed and produced and the principle of each module isexperimentally verified.Firstly, wafer transfer robot model is established and the transfer trajectoryplanning and kinematics simulation on the typical operation positions is carried out.The whole scheme of the detection system is proposed. The preliminary analysis onthe basic principle of each sensing modules is accomplished, including wafercontact state detection based on stick-slip sensor, end position detection based onthe two-dimensional PSD and end velocity estimation based on multiple-sensorfusion and kinematics Kalman filtering algorithm.Secondly, a stick-slip sensing scheme using magnet coil sensor is proposed.The prototype for stick-slip sensing is designed and developed. The prototype istested and calibration experiment is carried out which verifies the feasibility of thestick-slip sensing.The sensing principle of the two-dimensional PSD is analyzed, and theprototype for a two-dimensional PSD camera position sensor is designed anddeveloped. The prototype is experimentally tested for the step response andrepeatability. The two-dimensional PSD camera is calibrated using a precisionstepper motor platform. The analysis of errors and error correction method is carriedout. The multi-sensor fusion method is developed by using inertial sensormeasurements as the system input and PSD camera as an external observer.According to kinematic equations of the end-effector, Kalman filteralgorithm derivations are done and the velocity estimation of the wafer transferrobot ends is achieved in theory.Finally, an experimental system is established to detect the stick-slip during theactual wafer transmission and to achieve the position and velocity data ofcircular interpolation trajectory. The end motion performance of the wafer transferrobot is assessed.