NTUH-II robot arm with dynamic torque gain adjustment method for frozen shoulder rehabilitation

Frozen shoulder is a functional disorder related to shoulder muscles. Among many treatment strategies, rehabilitation exercise is one of the most common and viable therapy. In this research, a new 8 degrees of freedom (DOFs) rehabilitation robot arm named NTUH-II has been developed. The robot arm is able to provide most of upper limb rehabilitation motions in passive, active, and assistive modes. From the nature of muscle stretching, the exponential torque-angle relationship curve can be found, and thus it is possible to model and evaluate the condition of the patient's motion quality. The use of two parameters, stiffness and control authority, is proposed in this work. Based on these two parameters, an adjustment method of dynamic torque gain is developed and implemented on NTUH-II. Various experiments have been conducted, and appealing performance has been observed, which validates the method proposed in this paper.