抄録
This study investigates the estimation method of the human postural control ability while inclination and recovery in the sagittal plane and proposes an evaluation method of standing stability. One-link inverted pendulum model is applied to the human body and ankle joint torque is assumed to be generated based on time variant PID control method using tilt angle of the body. The subject is asked to stand still, incline forward as far and quickly as possible, and return to the original posture with subjects' eyes-opened, eyes-closed, and one-legged to simulate unstable condition of standing posture with visual disturbance and muscle weakness, respectively. Tilt angle in the sagittal plane is measured using optical motion capture system. Time variant PID gains are estimated according to the standing condition applying fixed trace method because conventional sequential least square method is affected by small noise of the tilt angle of body while standing still continued for a several seconds. Eleven healthy young subjects participated in the experiment and experimental results show that the body inclination is carried out by destabilizing the control system of standing posture and muscle weakness and visual disturbance are characterized by P-gain and D-gain, respectively. Estimated parameter variations are able to distinguish standing stability between three standing conditions.
