Fall detection and prevention in the elderly based on the ZMP stability control

An intelligent cane robot is designed for assisting the elderly or physically challenged people walking in daily life. The cane robot is driven by an Omni-directional mobile base; an aluminous stick is fixed on the base. A variety of sensors are installed on the cane robot for estimating the user´s intention and status (normal walking or falling). The user´s intentions of to which user want to move can be estimated by analyzing the active force on cane robot. As a nursing-care robot, the safety is a most important concern; before the elderly fall over, the cane robot should detect the sign of the falling and control the robot to assist the elderly to prevent it. Therefore a fall detection concept is proposed to estimate the risk of the falling based on the theory of zero moment point (ZMP) stability. An on-shoe sensor is designed to measure the ground reaction force and calculate the ZMP based on distributed force. The safety walking status is defined in the case of the ZMP is in the boundary of the support polygon. While the ZMP moving out of that boundary, the user will fall over.