노인용 보행보조기의 안전성 향상을 위한 노면 상태 및 기울기 추정

Abstract

This paper proposes a method for estimating the road surface condition and tilt angle using an inertial measurement unit (IMU) to improve the safety in the use of mobility aids for the elderly. The tilt of a road surface can be obtained by using the gravitational acceleration measured from the accelerometers of the IMU. However, the measurements of the accelerometers usually include the accelerations caused by not only the gravitational force but also linear and rotational motions. This paper presents a method to obtain the gravitational acceleration based on the fact that: the mobility aid cannot move laterally and vertically; and the gravitational force is equal to the Euclidean vector norm of the gravitational acceleration vector measured. The tilt of the road surface is eventually estimated through the Kalman filter using the obtained gravitational acceleration. In addition, the magnitudes of the accelerations produced by the rotational motions (roll and pitch motions) vary with the road surface condition and thus criterion is also presented to classify the condition of the road surface based on such accelerations. The obtained road surface condition and tilt are finally incorporated to provide the safety information e.g., safe, warning, and danger for the user to improve walking safety. Experiments are carried out and the results show that the proposed method can provide the condition of the road surface, the tilt of the road surface, and the safety information in the use of the mobility aid correctly.