Sensory Perception & Interaction Research Group

In some applications of simulated haptic feedback, it is necessary not only that the display feel stable and adequately realistic: it must resemble with high fidelity a particular real device, emulating the feedback supplied by a physical environment that does or will exist. An automated haptic characterization technique was developed in which the haptic display itself is used under tight position control to probe the real environment while measuring interaction forces. A model structure is assumed which may be nonlinear and globally discontinuous but piecewise continuous, and is refined for successively higher-order parameters by application of appropriately chosen position trajectories. A one degree-of-freedom linear-acting motor with 90 mm stroke, a peak force of 60 N and equipped with position and force sensors was used as both a probe and a force display. This algorithm was tested on one real environment, a toggle switch with a nonlinear, compliance-dominated impedance. Because of the nature of the real device, only stiffnesses were extracted; this zero-order, piecewise linear model assumption provided a close t to the measured trajectory with under 30 seconds of measurement and processing time. This was a substantial improvement in playback fidelity over that achieved by other characterization methods. Future work includes testing the algorithm on higher order systems.