Abstract
The triple arm mechanism is simple and basic spatial parallel mechanism with three degree of freedom which consists of a base link, coupler link and three two-link-chains having the actuated prismatic joint. In previous paper, we analyzed the sensitivites with respect to the kinematic constants which indicate the orientation of the rotational axes of the revolute pairs to consider the clearance of the revolute pair. And measuring the fluctuation of output angle caused by external force experimentally, we found the practical workspace of the movable platform is different with the one obtained from the analysis. In this paper, we report the method for the static analysis of this this type of parallel mechanism using massless free-body diagram. We show that the kinematic constants are changed by the weight of movable platform experimentally. And we confirm this phenomenon with results of the static analysis. Then, we estimate the cause of that difference between practical workspace and analytical one.
