Measuring and Increasing Z-Width with Active Electrical Damping

Abstract

The "Z-Width" of a haptic display is the dynamic range of impedances that can be passively rendered. Haptic displays with larger Z-width generally render more realistic feeling virtual environments.We present a new method for measuring and displaying the Zwidth of a haptic display. Instead of stiffness-damping plots, we believe a more illustrative technique for plotting the Z-width of a haptic interface is the envelope of achievable passive impedances as a function of frequency. Both hardware and analysis software for this new type of Z-width measurement are discussed.As previous research has shown, the maximum passive impedance that a device can render is directly related to the physical damping available in the mechanism. In an effort to maximize the Z-width of the haptic display, we present a new technique for adding physical damping to a haptic display through the use of analog electronics in the motor amplifier. Due to its electrical nature, active electrical damping has the benefit of dynamically variable parameters with no added mechanical complexity or mass.With the addition of active electrical damping, we show a performance improvement via a larger Z-width and larger range of passive virtual environment parameters.

Model Based Compensation for Low Mass Objects Haptic Manipulation in Virtual Environments

“…Colgate et al proposed three methods to increase the damping of the HI [14][15][16], in order to extend the Z-Width. the addition of an active physical damping to the motor rotor was proposed in order to simulate larger virtual impedances.…”

An injecting method of physical damping to haptic interfaces based on FPGA

“…Mehling and Colgate [8] developed passive electrical damping which was implemented by an electrical circuit and the damping parameter can be dynamically changed. Recently, an active electrical damping method was presented by Weir and Colgate [9]. They added physical damping to a haptic display through the use of analog electronics in the motor amplifier.…”

Dual-channel Haptic Synthesis of Viscoelastic Tissue Properties using Programmable Eddy Current Brakes

“…Undoubtably, such a feedback controller would have to be realized with mixed signal technology, partly digital, partly analog, to be truly programmable. Recently, a circuit able to add modest programmable electrical damping over a limited range of motion with a brushless motor was presented (Weir et al, 2008). If such circuits can be realized to achieve wide-range modulation of damping independently from torque, then the methods described in Section 5 would apply directly to this approach.…”