Postural stability control for Robot-Human cooperation for sit-to-stand assistance

This article presents a fuzzy controller, for a robotic device, to ensure stability of the user during the assisted sit-to-stand transfer. The first problem to be addressed is the postural analysis of the chair rising. Experiments, with healthy subjects, were performed with this aim in view. Analysis of external forces shows that sit-to-stand transfer can be subdivided into several phases. The observation of the Center of Pressure and of the horizontal component of the handle force yields rules to observe the stability of the patient and consequently adjust the robotic interface motion to the human volontary movement. These rules are used in the fuzzy control implementation. The controller is validated on experiments with healthy subjects and diseaded patients.