Feasible wrench space and its estimation for isometric haptic interaction

Standard approaches to mapping force to displacement or force to velocity with multi-DoF isometric haptic devices typically ignore the directional variability in a user's feasible wrench. We demonstrate that such a directionally-uniform mapping tends to either over-sensitize the interaction in some directions or under-utilize the user's operational range. To increase the effective use of the user's operational range it is necessary to model that range across all directions; for high-dimensional devices that measure wrenches (i.e, forces and torques) the space of directions is non-trivial to model by sampling. We present an approach that uses in-depth measurement of the feasible wrench space of a small number of users to extract a generic model for a given device interaction context; the generic model can then be automatically fitted to other users through a small number of measurements. In a user study comparing our method against the standard directionally-uniform assumption we show that our method generates a significantly better estimation of a user's output range, while requiring only a few measurements.