Inverse Dynamics of 3-UPU Parallel Mechanism with Pure Rotation Based on D´Alembert Principle

Based on D´Alembert principle, inverse dynamics of rotational 3-UPU parallel mechanism (PM) is analyzed in this paper. Through kinematic analysis of 3-UPU PM, motion parameters of links can be formulated with the ones of platform. A closed-form inverse dynamics of the rotational 3-UPU is put forward by applying D´Alembert principle to this PM. In dynamic analysis, mass of the link is decomposed to three parts including piston, cylinder and oil in actuated cylinder, by which the inverse dynamics of PM can be more accurate, especially for light-weight PM. It is thought that parallel computation can be easily realized with the method to solve inverse dynamics of rotational 3-UPU PM presented in this paper. Finally an example is simulated, in which rotational 3-UPU PM is used to compensate pitch and roll of mining ship in deep-ocean mining system.