Power spectral analysis of walking stability using personal navigation system

This study presents a new developed simple and cordless personal navigation system (PNS). The PNS is a synchronized system consisting of a gyro and magnetic compass sensors, and connected to a small wearable personal computer (WPC) of a wrist watch type. Nickel-hydrogen rechargeable batteries are supplied as the electrical power of both sensors. While walking, the WPC is worn like a wrist watch, the small sensors are fixed to a person's back near the center of body gravity, and batteries are inserted into a person's waist pouch. When a switch is turned on, the serial time count, three relative angles, i.e., roll, pitch and yaw, meterage and absolute direction of the person's back are recorded at 30 cps. They are also displayed on a liquid crystal display on the WPC. In this study, persons who have suffered a pelvic fracture, a foot fracture, or lumbar disk herniation, and normal persons were selected as subjects. In the case of persons who had experienced orthopedic damage, it was observed that the power spectrum density of the three angles and direction of back fluctuation were wavy. In the case of normal persons, it was observed that their power spectrum density was approximately close to 1/f/sup 3/ (f: frequency) fluctuation. This study provides useful information for medical rehabilitation and physical fitness in daily movement.