Dynamic modeling and control of a parallel upper-limb rehabilitation robot

This paper aims at dynamic modeling and control of a new upper-limb rehabilitation robot which has a parallel structure. Dynamic modeling of parallel robot is a complicated problem, and the dynamics and voluntary force of the patient arm increase the difficulty of dynamic analysis and control in rehabilitation training. The novelties of this study are: (1) dynamics of the robot and the patient are considered together, and this human-robot interaction system is modeled as a redundantly actuated closed-chain system (2 DOFs, 4 active joints); (2) the system dynamics are derived in workspace using a new method based on the dynamics of its three serial open-chain branches, and both kinematic constrains and interaction forces are considered during the derivation. Compared with the other two previous methods reviewed in this paper, the proposed method is easier to derive, more computationally efficient, and it can be used in both redundant and non-redundant cases. Besides, a model based PD-computed torque controller is designed and the simulation of passive training task along a circular path is presented to prove the effectiveness of this method.