Variable stiffness for shared authority control in robotic walkers

This paper presents a robotic solution to assist older adults with mild cognitive impairments in navigation. The system is based on a passive robotic walker, called FriWalk, which features actuated front steering wheels. Its key contribution is a guidance mechanism designed to follow a path while maintaining the user’s freedom of movement. When the user strays from the path, the system becomes rigid to ensure safe realignment. When the user’s movements are closely aligned with the path, the walker switches to ‘vehicle compliance mode’, allowing shared control through adjustable stiffness. In this mode, the system provides minimal interference, giving the user full control when s/he is very close to the planned path. However, as the user’s deviation increases, the walker gradually stiffens to keep the user on track. The paper includes theoretical validation of this mechanism, as well as simulations and experiments that demonstrate a strong balance between safety and user comfort.