Elbow orthosis for tremor suppression - A torque based input case

Abstract

In the endeavor to offer alternative treatments and solutions to patients with pathological tremor, robotic technologies are at the forefront, and represent a noninvasive potential solution to the needs of tremor patients. We developed a wearable robotic device having one Degree of Freedom, anthropomorphic to the human elbow. The device control architecture involves a speed controlled voluntary driven suppression approach whereby the robotic device tracks the voluntary motion. The tremor motion instead is considered a disturbance and is rejected. A second motor is attached to the orthosis in order to provide an input simulating the human voluntary and tremor motions. In this work, the human input to the robotic suppression device follows a torque profile. It is demonstrated that the suppression approach can successfully attenuate the tremor while following the voluntary motion component. However, it is also shown that a lag in the voluntary motion ensues. The experimental testing with the device resulted in a 99.4% reduction of the tremor power and 0.34% reduction to the voluntary component power. An analysis of the cause of the voluntary component delay is performed and associated hardware limitations are suggested. Finally, we consider whether the lag observed in the experiments, would be expected to also be observed if tests with human subjects are performed, as well as possible future solutions.