Smartphone-based sensory augmentation technology for home-based balance training

This paper describes the design and development of a smartphone-based sensory augmentation technology through vibrotactile biofeedback to support home-based balance training for individuals with balance disorders. The proposed system comprises a smartphone and a 3rd party sensor/actuator module. The smartphone´s application software communicates with the wearable module wirelessly via Bluetooth, provides instructions for a recommended balance training exercises (i.e., dynamic weight-shifting exercises) in clinical and/or home-based balance rehabilitation settings, and displays knowledge of results after the completion of the exercise. The 3rd party sensor/actuator module incorporates a nine degrees-of-freedom inertial measurement unit (IMU) and four vibrating actuators (tactors) for vibrotactile biofeedback. To estimate the body motion, a sensor fusion algorithm is developed based on an Extended Kalman Filter (EKF) to yield accurate and reliable orientation of the IMU. For dynamic weight-shifting exercises, a motion generation algorithm is developed by taking a user´s limits of stability (LOS). Furthermore, an algorithm for continuous coding scheme to control real-time vibrotactile biofeedback is developed to provide a user with the error magnitude while he/she is performing the recommended balance training exercises. The proposed system is the first step towards developing a portable balance training technology with vibrotactile biofeedback that could eventually be used at home.