Mechanical impedance tunnel of affordable desktop robotic arm for upper extremity rehabilitation

This paper introduces the concept of a mechanical impedance tunnel that can be implemented in cost-effective arm rehabilitation robots to facilitate path following while allowing for a certain degree of freedom. The desktop robotic arm discussed in this study has two degrees of freedom and is designed in a four-bar linkage shape. The output links are independent. The dynamic model of the robot considers the weight of the hand and resistance encountered during arm movement while assuming the links are massless. The control system employed is the endpoint impedance control, which is centred around the reference position in a moving tilt frame. The results of this study demonstrate that the control system enables cost-effective robotic systems equipped with brushless motors and integrated controllers to generate forces at the end effector. This facilitates path-following rehabilitation within the tunnel. Even when the end effector is displaced, the system can return the handle to the track. The findings of this work can be applied to other reference trajectories that have proven efficient for rehabilitation. Future studies will investigate the optimal impedance parameter that provides the best rehabilitation outcomes in patients.