Position Analysis of a Novel Family of Three-Legged 6-DOF Parallel Manipulators of Type 3-XXRRU

This paper presents a novel family of parallel manipulators (PMs) with three legs of type XXRRU and 6-degrees-of-freedom (DOF). Each leg is of type XXRRU where XX refers to an actuation mechanism, with actuated joints on the frame (base), that controls the pose of the axis of the first R-pair of the remaining RRU kinematic chain. The studied 3-XXRRU PMs have the orientation of this R-pair axis as controlled pose parameter in each leg. Accordingly, 6 input variables (two from each of the three legs) control the six DOF of the platform. In this paper, their position analysis is solved in closed form. The proposed PM architecture reduces the occurrence of leg interferences during motion since they have only three legs, which yields a much wider orientation workspace.