Dynamic Analysis of a 3DoF Motion Platform

In the present paper the dynamics of a 3DoF motion platform is studied that introduces a novel design of this mechanism. In this design, a balancer module which provides a non rotating vertical movement for the platform is utilized. It consists of three pairs of scissors which are synchronized by a gear set and a vertically mounted pneumatic actuator which balances the static weight of the platform. The specification of this mechanism compared to the previous designs is that provides a nearly constant upward force that remains in the direction of the weight in entire the workspace. Additionally it leads to a linear damping force in heave motion which provides a better control task. In this paper the complete dynamics of the system is modeled where factors like actuator frictions and non uniform distribution of load and the mass and inertia of legs are also considered and the velocity analysis is performed. The accuracy of the obtained dynamics model is verified by comparing the result of simulation with that of an equivalent model built in SimMechanics.