Knee joint angle measurement system using gyroscope and flex-sensors for rehabilitation

This paper focuses on developing a novel approach for measuring body joint angles, mainly the knee angles, for surface electrical stimulator system. In this work, we only focus on the sensing mechanism for measuring the knee joint angle using wearable sensors. Our system consists of multiple flex-sensors mounted on a supportive cloth and microelectromechanical systems (MEMS) vibratory gyroscope. In Body Sensor Network (BSN) field for medical purpose, body joint angle measurement system is quite important and useful for continuous monitoring in rehabilitation activities especially for Spinal Cord Injury (SCI) patients. Body joint angle measurement system is sensory type systems that provide information about angle movement of body joint. It is usually used at knee and arm joint to monitor the movement while patients do some exercises. This very important and helpful for the therapists and physicians in order to see the effectiveness of rehabilitations training. For knee angle movement evaluation, lower limb joint angles and segment angles were estimated by the Kalman filter from the data measured with wireless MEMS vibratory gyroscope and flex-sensors. Electrical stimulation was applied to the common peroneal nerve or the tibialis anterior muscle by detecting stimulus timing automatically from the data of wireless sensor attached at the back of knee which known as popliteal fossa and shank of the paraplegic side. The developed system performed well in monitoring the effectiveness of rehabilitations training with the knee joint angle measurement average error rate of 6.92°. The comparison between measured data of the gyroscope and flex-sensors for knee joint angle measurement system were also demonstrated.