Abstract: The 2-DOF parallel platform can greatly enhance the traditional platform pointing capability under heavy load, high velocity, high acceleration and large workspace conditions, and expand the application of parallel platforms in a wide field because of the particularity of movement pattern. Obviously, the precise dynamic model is the prerequisite for the achievement of its high velocity, high precision motion control. Omni-wrist III is a quasi-sphere motion 2-DOF parallel platform has symmetric structure and large workspace. The geometric constraint equations of this mechanism are established based on the particularity of the geometric structure, the detailed compact kinematic model of moving platform and four legs are derived. The dynamic model is established based on the Lagrange method and the effective inertia variety with the change of mechanism is discussed. The simulation of mechanism dynamics is implemented by using Adams software. The derived model will be useful to improve the design of the mechanical components, the control algorithm of this manipulator and the selection of motor.

Key words: Dynamics, Kinematics, Lagrange method, Parallel mechanism