Performance Analysis of 4-RPUR Parallel Mechanism for Ankle Rehabilitation

Four-degrees-of-freedom (4-DoFs) ankle fracture surgery assistant and rehabilitation robot based on 4-RPUR was developed to help the patients recover movement ability of the ankle. Furthermore, to evaluate the performance of the robot, we use a spatial search method to calculate and depict the workspace images, and analyze the sensitivity of the workspace to different parameters; based on screw theory, a singularity evaluation indicator is proposed, and singularity images are drawn; the robot is subjected to stiffness modeling, constructing a stiffness matrix for the mechanism and establishing stiffness evaluation indicators, and creating performance spectra, with further analysis and discussion on the physical variation rules and physical meanings of the spectra.