Stability Margin Monitoring in Steering-Controlled Intelligent Walkers for the Elderly

This paper emphasizes the importance of assessing stability index for steering-controlled three-wheeled walkers. The paper describes a stability computation model that can be used to generate a reference input to the intelligent sharedcontrol algorithm. The model can be used to evaluate the instantaneous stability margin of the walker-user system. This knowledge of the online stability of the walker will enable the shared controller to intelligently decide on the most appropriate time for the activation of the control to minimize the likelihood of jeopardizing the system stability as a result of the system’s control actions, and possibly prevent falls due to control actions. The results of a stability computation model, based on the force-angle stability measure, are presented for different walker-assisted navigational scenarios including: walking straight, making soft turns, making sharp turns, and control fighting. The results showed that assisted steering enhanced the user’s stability when the user’s and the walker’s intents were aligned. However, the results also indicated that a conflict between the user’s intent and the walker’s control actions (or walker’s intent) in so called intelligent walkers could jeopardize the stability of the walker-user system, and hence that of the walker’s user.