Accuracy and Repeatability Study of An Elbow Exoskeleton for Multistage Exercises

The need for post-stroke rehabilitation is paramount especially with the increasing number of stroke survivors worldwide. It appears that patients must receive multistage therapy consisting of specific exercises to improve their neuro-motor function. Modern-day advancement in biomedical technology has transformed the exoskeleton into a potential tool for post-stroke rehabilitation. Several exoskeletons have been developed for providing post-stroke exercises, however, their actions are influenced by several inhibiting factors such as abnormal sensor data, continuous usage of power source, safety from anatomical range etc. Besides their working principle is limited to providing a specific type of exercise. To overcome the current limitations of the existing systems for providing multistage exercises in post-stroke rehabilitation, a novel elbow exoskeleton has been developed where joint movements are supported by an electric motor or springs in different stages. The innovative mechanism incorporates the benefits of an electric motor and springs; the electric motor is used to maintain external force-controlled joint movement during the acute stage whereas joint motion is partially assisted or resisted by spring force in the recovery stage hence minimizing the energy consumption from motors. A pilot experiment has been conducted among healthy participants to measure the joint parameters and to analyze the accuracy and repeatability of the measurements by the exoskeleton. The measured joint parameters from the exoskeleton have been also compared with the Kinect motion analysis system where the measurement error in joint angle is around 1% to 6%. The correlation coefficient between consecutive joint measurements is higher than 0.99 proving the high repeatability of measurement.