Wu Jun

Observability index of identified parameter for kinematic calibration of parallel mechanism

This paper presents a new observability index of identified parameter to quantify the selection of best configuration set in kinematic calibration of parallel mechanisms. This proposed observability index has the following advantages: (1) it is a detailed index for each identified parameters, that is, one index corresponds to one identified parameter; (2) it has a real significance: the variations of estimated value of the identified parameter; (3) it includes the information of both identification Jacobian and measurement noise. Simulation results of a three degrees-of-freedom (DOF) parallel mechanism are given to illustrate the validity and effectiveness of the proposed index.

Analysis and control of a 4-DOF manipulator to operate inside narrow and long pipes

To manipulate inside a narrow and long pipes, a 4-DOF manipulator which possesses a PRRR mechanism is designed. Geometrical method is employed to deduce the kinematic equations of the mechanism, then the condition number is obtained and a group of optimal link magnitudes is determined. Then the Newton-Euler method is used to derive the dynamic model and the drive torques of all joints are calculated. According to the dynamic model, a robust control method is proposed on the basis of linear feedback theory of non-linear systems. In contrast with traditional PID control the control method presented in this paper can better reduce the tracking error of the joints, moreover the convergence of error is faster