Cooperative Control Design for Robot-Assisted Balance During Gait

Abstract

Summary Avoiding falls is a challenge for many persons in aging societies, and balance dysfunction is a major risk factor. Robotic solutions to assist human gait, however, focus on average kinematics, and less on instantaneous balance reactions. We propose a controller that only intervenes when needed, and that avoids stability issues when interacting with humans: Assistance is triggered only when balance is lost, and this action is purely feed-forward. Experiments show that subjects who start falling during gait can be uprighted by such feed-forward assistive forces. Zusammenfassung Sturzvermeidung ist eine ständige Herausforderung für viele Menschen in alternden Gesellschaften, und Gleichgewichtsprobleme stellen ein bedeutendes Risiko für einen Sturz dar. Heutige robotische Lösungen zur Unterstützung des menschlichen Gangs sind allerdings hauptsächlich auf das gemittelte Gangbild ausgerichtet und weniger auf instantane Gleichgewichtsreaktionen. Wir schlagen hier einen Regler vor, der nur dann interveniert, wenn nötig, und der keine Stabilitätsprobleme verursacht, wenn er mit dem Menschen interagiert: Stellgrößen werden erst dann generiert, wenn der Mensch das Gleichgewicht verliert, und diese Unterstützung fungiert als reine Vorsteuerung. Experimentelle Ergebnisse zeigen, dass menschliche Probanden, die während des Gehens zu fallen beginnen, durch solche unterstützenden, vorgesteuerten Kräfte in eine aufrechte Haltung gebracht werden können.

Directional Singularity-Robust Torque Control for Gyroscopic Actuators

“…A controller for a CMG array generally consists of two (not necessarily distinct) components: an outer feedback law responsible for converting the objective quantity (typically a reference attitude) into a reference moment and compensating for disturbances, and an inner model-based control allocation scheme (often called a gimbal steering law) responsible for generating the gimbal and rotor acceleration commands necessary to track this moment. We describe in [7] an exemplary outer control law in the form of a pre-parametrized moment profile, and instead focus here on the latter element.…”

A MUltidimensional Compliant Decoupled Actuator (MUCDA) for Pelvic Support During Gait

“…Impulsive forces could for example assist balance by inducing quick recovery movements. Previously, we had proposed a model-based control scheme that assisted lateral balance [33] using a modified Lokomat robot with lateral actuation. That controller was based on the concept of the extrapolated center of mass [46] or capture point [47].…”

“…However, the stiffness must be at least as high as the maximum expected virtual stiffness that will be rendered by an assistive controller [24]. From experience with balance assistance on a similar robot [33], we know that making use of feed-forward assistance, a relatively low stiffness of 3000 N /m is sufficient.…”

Multidirectional transparent support for overground gait training

“…For specialized therapy, further algorithms may support subjects in balance tasks, possibly based on the approach we proposed in [22]. The question remains how humans might alter their balance reactions when additional help is provided.…”