Zhu Yanhe,Zhao Jie,Cai Hegao
（Robot Research Institute, Harbin Institute of Technology,Harbin 150001,China）
Abstract:A closed loop self-calibration method for Delta mechanism without requirement of external position and orientation measurement equipment was presented. This approach blocks successively one of the gimbals of the mechanism using a simple lockup device and reforms the Delta mechanism to be a 2-degree of freedom one. The parameter errors of the mechanism are identified according to the differences between the sensor output of the redundant chain and nominal model output. Both the condition number and singular value of the error propagation Jacobean are synthesized as a selection principle of calibration set such that the calibrating process is insensitive to the noise and the calibration precision is increased efficiently. Experiments show that the ratio of maximal error before and after calibrating is 9.6, namely,the setting accuracy of the mechanism is increased about 10 times and the error of reposition is less than 0.07mm.
Keywords:delta mechanism;closed-loop;self-calibration;error observation index