Implementation of stiff virtual walls in force-reflecting interfaces

The performance of a haptic interface is often reported in terms of the dynamic range of impedances it may represent. At the low end, the range is typically limited by inherent dynamics of the interface device, such as inertia and friction. At the high end, the range is typically limited by system stability. In a number of the applications, the principal limitation has proven to be the achievable upper limit on impedance. Therefore, a benchmark problem of considerable importance is the implementation of a stiff "wall". Contacting a wall may be described as the reversible transition from a region of very low impedance to one of very high impedance. A theoretical analysis (supplemented with discussion of experimental and simulation results) of stiff wall implementation is presented. The main result is a criterion for the passivity of a virtual wall in terms of two nondimensional parameters.>