Displacement and Force Analyses of an Upper Limb Driving a Rehabilitation Robot Using F_R-SUCr-U Model

The main purpose of this study is to develop a biomechanical model of the upper extremity for analyzing joint displacements and forces of the limb when it drives a rehabilitation robot. An S-SUCr-U chain is proposed as a new skeleton model (from the shoulder joint to the wrist joint) of the upper limb, which has better description of pronation/supination of forearm when the humerus is held fixed. Based on the chain, an F_R-SUCr-S spatial 4-bar mechanism is proposed for simulating the upper limb driving a rehabilitation robot. The displacement model of the 4-bar mechanism is then developed and two approaches, namely, three-actuator and multi-actuator approaches are adopted for the force analysis. For each approach, computer programs are developed and the results are compared with those of using the Adams software for validation. The results revealed that the multi-actuator approach yields more reasonable results than the three-actuator approach and the objective function of the optimization problem is feasible. The net joint torques and forces can be used in solving the load sharing of the muscles of the upper extremity in next stage of research.