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In this article, a new methodology for type synthesis of uncoupled translational parallel manipulators with 3-degrees of freedom is proposed based on actuation wrench screw theory. Mapping matrix between outputs of the moving platform and the inputs of the actuators for uncoupled translational parallel manipulators is derived. The forms of both the actuated twist screws and the actuation wrench screws of the limbs are determined by means of the condition that the Jacobian is a diagonal matrix with full rank. The steps used to confirm the non-actuated screws of the limbs are also established. Then, procedures for structure synthesis of the limbs are set up and all possible basic structure limbs are enumerated. Some new uncoupled translational parallel manipulators are synthesized by selecting three limbs connecting the platform to the base and two examples are given. The approach proposed is applicable to the type synthesis of uncoupled parallel manipulators with rotational mobility as well.

Abstract:A novel uncoupled translational parallel mechanism (UTPM) with three degrees of freedom (3-DOFs) is presented, which is composed of a moving platform connected to a fixed base by three identical kinematic chains. Firstly, kinematic output property of the moving platform is analyzed. Then, both the forward and the inverse analytical solutions of the kinematic problems are discussed in detail. The velocity Jacobian is a 3 3  diagonal matrix, which implies that there exists a one-to-one corresponding relation between the inputs and the outputs of the parallel mechanism. Finally, the kinematic simulation is carried out by MATLAB and Pro/E software. Simulation results show that the theoretical analysis is correct and feasible.