Showing papers by "J.E. Colgate published in 2008"

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 Z- width 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

On the Design of a Thermal Display for Upper Extremity Prosthetics

Abstract: We are developing a multi-function haptic device that displays pressure, vibration, shear force, and temperature to the skin of upper extremity amputees, especially those who have undergone targeted nerve reinnervation (TRI) surgery. This paper presents the design of the thermal display portion of this device. Through psychophysical temperature discrimination tests, the unique thermal response characteristics of intact hands and TRI-chests are explored.

Haptic display of dynamic systems subject to holonomic constraints

Abstract: This paper presents a framework that enables an operator to haptically and visually interact with a simulated dynamic environment subject to virtual holonomic constraints. The framework combines a geometric constraint solver with a constrained dynamics simulation engine that controls an admittance-type haptic display. This system takes on relevant issues in the context of assisted teleoperated tasks, from providing an intuitive interface for creating and combining virtual constraints, to haptically displaying rigid motion constraints in simulated environments subject to desired inertial dynamics. Two experiments carried out using the Cobotic Hand Controller haptic display are presented.