Research on type synthesis of a new class of 2T1R uncoupled parallel mechanism with a suitable constraint branch

Type synthesis is an essential building block for addressing the original innovation problems of mechanisms. The current paper presents a new class of 2T1R (two-translational and one-rotational) uncoupled parallel mechanisms (UPMs) with a suitable constraint branch by use of the actuation wrench screw theory. The composition principles of the motions, constraints, and driving forces for UPMs with a suitable constraint branch are described. Decoupling analysis between the actuation wrench screws and the output motions of the 2T1R UPMs is investigated. The input-output mathematical model of the UPMs is established. Then structural synthesis of the suitable constraint branch and the actuated branches is completed by utilizing the screw theory. Finally, a number of novel 2T1R UPMs with a suitable constraint branch are synthesized, following the given assembly rules. Kinematics analysis of the 2PRRRR-PRRR/PPR mechanism is derived as an illustration to demonstrate the correctness and the feasibility of the proposed type synthesis method.