The development of a generic and effective force model for semi-automatic ormanual virtual assembly with haptic support is not a trivial task, especiallywhen the assembly constraints involve complex features of arbitrary shape. Theprimary challenge lies in a proper formulation of the guidance forces andtorques that effectively assist the user in the exploration of the virtualenvironment (VE), from repulsing collisions to attracting proper contact. Thesecondary difficulty is that of efficient implementation that maintains thestandard 1 kHz haptic refresh rate. We propose a purely geometric model for anartificial energy field that favors spatial relations leading to properassembly, differentiated to obtain forces and torques for general motions. Theenergy function is expressed in terms of a cross-correlation of shape-dependentaffinity fields, precomputed offline separately for each object. We test theeffectiveness of the method using familiar peg-in-hole examples. We show thatthe proposed technique unifies the two phases of free motion and preciseinsertion into a single interaction mode and provides a generic model toreplace the ad hoc mating constraints or virtual fixtures, with no restrictiveassumption on the types of the involved assembly features.
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