Electrical Damping for Haptic Displays (24093/24111
The invention applies electrical damping in order to improve haptic display performance. A challenge of virtual environments is that a haptic system can become unstable near the "virtual walls," where high frequency oscillations result. The invention uses electrical damping to damp over a range of high frequencies. Electrical damping for haptic displays has the following advantages over mechanical damping:
It can damp oscillations over a range of high frequencies that occur at or near virtual walls. Damping can easily be made frequency dependent, to avoid adverse affects on low frequency oscillations occurring away from virtual walls. It enables simplicity of design. The invention utilizes a variety of techniques. One such technique includes the addition of a resistor and capacitor in parallel with the haptic motor. Other methods incorporated by this invention exploit the commutation characteristics of multi-phase motors, especially those of DC brushless motors. The invention is intended to provide damping only in the high frequency range. Nevertheless, it is not a tuned damping system, because it applies damping over a broadband of high frequencies. This is important, because a goal of haptic display design is to maximize frequency range so that a wider range of virtual environments can be modeled stably and effectively for the user.
Fig. 1: Experimental data shows that additio of a resistor and capacitor in parallel with the motor can increase the stability boundary of a haptic display several fold.
Ed Colgate, Michael Peshkin, Joshua Mehling, and David Weir
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