Kinematics and performance analysis of a parallel 4-UPS/RRR trunk rehabilitation robot

Aiming at the problems that the rotation center of the existing trunk rehabilitation robot does not coincide with the movement rotation center of the human spine and the human-machine compatibility is poor, a more convenient, simple, and practical 3-degree-of-freedom 4-UPS/RRR trunk rehabilitation parallel mechanism with adjustable with fixed center of rotation is designed. The kinematics of the mechanism are analyzed by the closed-loop vector method, and the velocity Jacobian matrix is established. Based on the transmission performance analysis of the drive pivot chain and then combined with MATLAB simulation to complete the optimization of the mechanism layout, the optimized mechanism’s workspace, condition number, and stiffness properties are also analyzed. The simulation results show that in the working space of the mechanism, the motion performance of the trunk rehabilitation mechanism proposed is good, and it can provide more scientific and standardized rehabilitation training for the human trunk.