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.