Novel Design of Wrist With Gripper: Type Synthesis of a 2R1T Parallel Mechanism Possessing One Actuation Degree-of-Freedom

Abstract The parallel mechanism (PM) with a configurable movable platform (CMP) holds the potential for achieving a high-response speed and high-stiffness integrated design of a gripper-wrist system. The motion of two rotations and one translation (2R1T), closely resembling the movement of a human wrist joint, is highly complex. Therefore, research on 2R1T PM with CMP remains unexplored. Additionally, a systematic method for constructing PM with CMP is also lacking. This paper proposes fundamental design principles for PM with CMP. The topological arrangements of 2R1T PM with CMP are classified according to the number of limbs, their types, and the CMP structure. The basic constraint conditions and the redundant constraint conditions of 2R1T PM are analyzed. By establishing the relationship between finite motions, joint geometric parameters, and constraint screws, a series of limb structures that provide specific constraints in finite motions are constructed. Several configuration examples of gripper-wrist mechanism are provided, which can serve as a guide for subsequent researches. The design approach of CMP is discussed. The performance advantages of such mechanisms are validated through simulation-based comparisons.