ワンボード・マイコンを利用した障害歩行診断のための無拘束長時間歩行モニタ

Abstract

A microcomputer-based ambulatory monitor has been developed. This monitor utilizes a CMOS one-chip microprocessor (Toshiba Z 84 C 015-10), which has an Intel Z 80-compatible 8 bit CPU, two 8-bit parallel I/Os, four 8-bit counter/timers, and a fullduplex serial I/O. A general purpose min/max detector circuit has been designed to detect minimum and maximum values of a single-channel cyclic analog signal correlated to human gait. The analog signal fed to this circuit is converted to two logical pulses the width of which is proportional to the minimum and maximum values during one gait cycle. A logical signal which represents the gait cycle is also generated. These three logical signals are connected to three signal lines of a parallel port. Clock pulses of 100Hz and 10kHz are also generated and connected to three counters which convert pulse width or pulse cycle of the logical signals into corresponding digital representations of minimum, maximum, and cycle time of the gait-associated analog signal. The digital representations of 8,000 gait cycles can be stored in 32kbyte RAM, and retrieved from serial port via RS232C interface at a request from any host personal computer. The min/max detector circuit is assembled with DIP ICs, and contains a one-chip microcomputer, other peripheral circuits and a 006 P 9[v] battery, in a plastic box measuring 140(W)×80(H)×40(D)[mm]. The weight of the total monitor box is 120g. As one application of this ambulatory monitor, measurement of stride length and walking velocity was attempted. The absolute segmental angle of the thigh of one leg in the sagittal plain was detected by a piezoelectric gyroscope attached to the top of the knee. The angle signal was fed to the min/max detector circuit. Stride length was estimated from the absolute of this segmental angle by utilizing a simple mathematical model of biped locomotion. Walking velocity can be calculated from stride length and cycle time. The accuracy of the stride length and walking velocity was evaluated for 8 normal female, 11 normal male, 3 hemiplegic, and 3 A/K amputee subjects. The result was promising. Possible applications of this ambulatory monitor for assisting clinical decisions on patients with gait disabilities are discussed.