Abstract: A 3-DOF hybrid parallel-serial robotic manipulator which is constructed by combining a parallel mechanism and a pantograph is introduced to increase high stiffness as well as workspace, based on the fact that parallel mechanism has higher stiffness but smaller workspace. Dynamics equation is established by applying Lagrange’s method and its feature is discussed. Then a robust control scheme for the robot is developed. The proposed controller which is designed in Cartesian coordinates consists of two parts. The first part is the model-based computed torque controller which is used to stabilize the nominal robot system. The second part is a robust compensating controller which is designed to handle the uncertainty in the system. The theory analysis and simulation results show that using this controller, the robot tracking performance can be improved effectively.

Key words: Lyapunov method, Hybrid parallel-serial robot, Robust control, Importance measure, Moment-independent, Point-estimate, Uncertainty