Design and fabrication of an assistive device for arm rehabilitation using twisted string system

In this research the twisting cable mechanism was employed to design and develop a light elbow assistive robot. A particular type of fishing line was experimentally tested for use as the strand material, and the behavior was compared to the proposed model. A correction parameter called effective diameter was derived to adapt the model to the experimental data. To ensure the consistency of the model, hysteresis of two-strand cables was tested. A curve was fitted to the experimental data and the most linear range was selected to be used in the mechanism. Moreover, a single degree of freedom elbow mechanism for flexion and extension was designed and constructed. Ultimately, to ensure the applicability of the mechanism, an ordinary Activity of Daily Living (ADL) was used and the angle of the twisted strand actuator motor as a function of the motor rotation was computed.