Design And Study Of Ankle Rehabilitation Robot Based On 3-RRS Spherical Parallel Mechanism

Spherical parallel mechanism(SPM for short) as a special type of parallel mechanism, has the characteristics of large workspace, not easy to occur interference between parts. Now, SPM has been widely used in the robot’s shoulder, wrist, waist, hip and ultra precision machining, aerospace, surveying and mapping, etc. field. Ralative to 3-RRR SPM, 3-RRS SPM is not overconstrained, has better kinematics performance, and also can realize the rotations around three directions.Based on screw theory, this paper analyzed and calculated the DOF of 3-RRS SPM. By using the Newton iteration method, the forward kinematics of the mechanism is solved. The inverse kinematics model of the 3-RRS SPM is established by using the closed-loop vector method. The corresponding inverse kinematics of mechanism was solved. Eight groups of inverse kinematics of 3-RRS SPM is obtained. A example of 3-RRS SPM is given to verify the validity of the kinematics analysis.On the basis of kinematics analysis 3-RRS SPM, by using the method of derivation, the velocity, Jacobian matrix and the acceleration of 3-RRS SPM are derived. Based on Jacobian matrix, the singularity of 3-RRS SPM is discussed. The reachable workspace of 3-RRS SPM is solved with the help of numerical search method. By using the MATLAB programming, the reachable workspace figures of 3-RRS SPM with diffierent structure parameters are drawn.The statics balance equations of diffierent parts of 3-RRS SPM are establishedby using the disassembled method. The statics of 3-RRS SPM is analyzed.The structure, motion law and recovery princeple of ankle are analyzed. Combining the characterastics of 3-RRS SPM with the requirements of ankle rehabilitation needed for robot, the concrete structure and stucture parameters of 3-RRS spherical ankle rehabilitation robot is designed.Then, by using SolidWorks and ANSYS workbench software, the static finite element of 3-RRS spherical ankle rehabilitation robot is analyzed. The weak places in the design process of overall structure of 3-RRS spherical ankle rehabilitation robot is found.Finally, by using the SolidWorks and ADAMS software, 3-RRS spherical ankle rehabilitation robot is simulated. The displacement curve, velocity curve and acceleration curve of reference point on the foot shelf of 3-RRS spherical ankle rehabilitation robot are obtained. Through forward kinematics simulation and inverse kinematics simulation are consistent, and uniform changed according to the law of sine/cosine curve with respect to time. There are no velocity and acceleration mutation. Thus, in the process of actual use, it will not cause ankle secondary injury. The robot can move along a complex spherical spiral trajectory, carry ankle realise the motions of the Dorsal flexion and plantar flexion, inversion and eversion, adduction and abduction at the same time, which proved that the ankle rehabilitation robot can be used for ankle rehabilitation training.