Design and analysis of a novel 3T1R four-degree-of-freedom parallel mechanism with infinite rotation capability

A 4-degree-of-freedom (DOF) parallel mechanism with 3 translations and 1 rotation (3T1R) has wide application potential in the industry. However, most of the existing 3T1R parallel mechanisms have limited rotation capacity of the moving platform, which is usually less than ±90°. In this paper, a new type of 3T1R parallel mechanism is designed by configuration deduction method based on the 3T1R parallel mechanism studied at present. The structure of the parallel mechanism is simple and symmetrical, and the motion pairs are all rotating pairs, which have Selective Compliance Assembly Robot Arm motion and complete rotation capability. Firstly, the branch motion spiral system is established by using the screw theory, and then the constraint spiral of each branch to the motion platform is solved, and the constraint spiral system is analyzed, so as to determine the number of DOFs and properties of the mechanism. Secondly, the position, velocity, and singularity of the mechanism are analyzed, and the workspace of the mechanism is analyzed by the positive position solution. Then, the trajectory planning of operation space is completed, and a mathematical model of portal grasping trajectory is established. Thirdly, the kinematic simulation analysis of the mechanism is carried out. Finally, an equal scale physical model was made by 3D printing technology to verify the rationality of the design and the correctness of the theoretical analysis.