Modified Robust Dynamic Control for a Diamond Parallel Robot

In this paper, a modified robust dynamic control (MRDC) method is proposed for a 2-DOF Diamond parallel robot to realize high-precision and high-speed cooperating motion. Diamond robot is a double-input and double-output system with both coupled dynamics and uncertain dynamics. Based on the dynamic equation in joint coordinates, an MRDC that can drive the two active arms of Diamond robot to stay in two decoupled terminal sliding modes with continuous control signals is designed. The control law of MRDC is specially constructed to be insensitive to the noise in speed signal, which can help improve error convergence speed without causing undesirable system chattering. With suitable control parameters, the proposed MRDC can assure the stability of Diamond robot even in the presence of disturbance, parameter variation, etc., which is verified in sense of the Lyapunov function. MRDC is then successfully implemented on a Diamond robot prototype controlled by a commercial PMAC motion control card. Experimental results show that the proposed MRDC can achieve both good trajectory tracking performance and good robustness against disturbance. Compared with the robust dynamic control and potential difference control, MRDC can avoid undesirable system chattering and assure better trajectory-tracking accuracy, respectively.