Design and analysis of a partially decoupled generalized parallel mechanism for 3T1R motion

Compared with conventional parallel manipulators with serial kinematic chains supporting a nonflexible platform, generalized parallel mechanisms may be further constrained by interconnected coupling sub-chains or configurable platforms. The additional coupling sub-chains and configurable platforms have the potential advantages of improving overall characteristics and executing specific output motions. Based on the applications, this paper proposes a symmetric generalized parallel mechanism with so-called Schönflies motion. This mechanism can generate three independent translations in conjunction with a partially decoupled rotation which refers to a given direction. To improve the dynamic performance, all the actuators are installed on the fixed platform. The paper starts with the number synthesis of independent loops that can derive all possible non-isomorphic contracted graphs of the 3T1R generalized parallel mechanism. The threefold-symmetric Bricard linkage is introduced into the generalized parallel mechanism. Besides, several novel generalized parallel mechanisms with various motion patterns are provided. The kinematic analysis of the proposed architecture is established. The evaluation of the workspace is conducted. Finally, the study of the overall Jacobian matrix is performed and the singularity including kinematic singularity and constraint singularity is analyzed.