This paper presents a new class of parallel mechanism which is constructed with a 5-limb RSP architecture. To provide insight into the geometry and the position analysis of this mechanism, the paper presents closed-form solutions to the inverse and forward kinematic problems. Then the Kutzbach mobility criterion is used to show that the platform of the 5-RSP mechanism has a single degree of freedom. A mobility analysis based on the reciprocal constraint and motion sets of screws shows that the platform exhibits a screw motion, that is, a translation along and a rotation about the screw axis. The ratio of the translation to the rotation (referred to as the instantaneous pitch of the screw) is shown to be a function of the platform position. The screw axis is perpendicular to the base of the mechanism for all positions of the platform and passes through the centroids of the base and the platform. The attractive features of centralization are the simple design, and the wide range of possibilities for the pitch of the screw motion of the platform. Finally, the paper presents geometrical conditions that result in the pure translation of the platform; i.e., the rotational degree-of-freedom is eliminated.

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