The Design of a Cell-Phone Based Balance-Training Device

Postural imbalance can result from various vestibular (central and peripheral), neurological, orthopedic, and vascular disorders, as well as sensory conflicts, head injuries, infections, medications, and aging. Balance rehabilitation has been shown to improve the quality of life of individuals with balance disorders by facilitating the development of compensatory strategies which mitigate dizziness, improve balance, and increase the ability to perform activities of daily living. The goal of this work is to design a cell phone based balance training device that can be used in the home to assist a patient with therapist-assigned balance exercises or in an environment where access to balance therapy is limited (i.e., rural regions in the developing world). The prototype comprises an iPhone (iPhone SDK, Apple), an auxiliary pager motor (Samsung GH31-00154C), and an audio amplifier (Analog Devices SSM2301). Body motion is detected by on-board tri-axial accelerometers, and a tilt estimate is computed using a low-pass filter. The phone's native pager motor and an auxiliary pager motor are used to provide real-time vibrotactile cues of body tilt along a single axis. The phone is worn on the small of the back to provide anterior-posterior vibrotactile trunk tilt feedback during stance, and worn near the right hip to provide medial-lateral vibrotactile trunk tilt feedback during gait. Auditory files direct the user through a series of standard balance rehabilitation exercises. A summary of the user's performance is displayed on the phone's screen following completion of the exercise.