Showing papers by "Michael A. Peshkin published in 2010"

ShiverPaD: A Glass Haptic Surface That Produces Shear Force on a Bare Finger

Abstract: We discuss the design and performance of a new haptic surface capable of controlling shear force on a bare finger. At the heart of the ShiverPaD is the TPaD variable friction device. It modulates the friction of a glass surface by using 39 kHz out-of-plane vibrations to reduce friction. To generate shear forces, the TPaD is oscillated in-plane (i.e., “shivered”) while alternating between low and high friction within each cycle. In previous research, the ShiverPaD produced shear forces using in-plane vibrations below 100 Hz. In this research, we develop a new ShiverPaD that produces force using 854 Hz vibrations, where human sensitivity to vibration is diminished. The new device is used to display a virtual toggle switch and a variety of virtual edges. A human subject study is conducted to demonstrate that users can easily trace virtual edges displayed on the surface of the ShiverPaD.

On the Design of Miniature Haptic Devices for Upper Extremity Prosthetics

Abstract: We have developed three different versions of a multifunction haptic device that can display touch, pressure, vibration, shear force, and temperature to the skin of an upper extremity amputee, especially the one who has undergone targeted nerve reinnervation (TR) surgery. In TR patients, sensation from the reinnervated skin is projected to the missing hand. This paper addresses the design of the mechanical display, the portion responsible for contact, pressure, vibration, and shear force. A variety of different overall design approaches satisfying the design specifications and the performance requirements are considered. The designs of the fully prototyped haptic devices are compared through open-loop frequency response, closed-loop force response, and tapping response in constrained motion. We emphasize the tradeoffs between key design factors, including force capability, workspace, size, bandwidth, weight, and mechanism complexity.

Preswing Knee Flexion Assistance Is Coupled With Hip Abduction in People With Stiff-Knee Gait After Stroke

Abstract: Background and Purpose—Stiff-knee gait is defined as reduced knee flexion during the swing phase. It is accompanied by frontal plane compensatory movements (eg, circumduction and hip hiking) typically thought to result from reduced toe clearance. As such, we examined if knee flexion assistance before foot-off would reduce exaggerated frontal plane movements in people with stiff-knee gait after stroke. Methods—We used a robotic knee orthosis to assist knee flexion torque during the preswing phase in 9 chronic stroke subjects with stiff-knee gait on a treadmill and compared peak knee flexion, hip abduction, and pelvic obliquity angles with 5 nondisabled control subjects. Results—Maximum knee flexion angle significantly increased in both groups, but instead of reducing gait compensations, hip abduction significantly increased during assistance in stroke subjects by 2.5°, whereas no change was observed in nondisabled control subjects. No change in pelvic obliquity was observed in either group. Conclusions—Hip abduction increased when stroke subjects received assistive knee flexion torque at foot-off. These findings are in direct contrast to the traditional belief that pelvic obliquity combined with hip abduction is a compensatory mechanism to facilitate foot clearance during swing. Because no evidence suggested a voluntary mechanism for this behavior, we argue that these results were most likely a reflection of an altered motor template occurring after stroke. (Stroke. 2010;41:1709-1714.)

Friction measurements on a Large Area TPaD

Abstract: We describe a variable friction haptic display on a large area of glass, and characterize its performance. The Large Area Tactile Pattern Display (LATPaD) uses modulation of surface friction created by ultrasonic vibration, as in previous smaller devices [8]. Unlike those, the LATPaD does not operate in the lowest resonant mode. As a consequence, the vibration amplitude varies across the surface of the LATPaD (being zero at nodal lines) and therefore the friction reduction effect varies spatially. In practice, the variation in friction reduction is less than might be expected, due to the finite extent of the finger pad. We measure friction over the surface for several mode shapes.

Haptic device with controlled traction forces

Abstract: A haptic device includes a substrate that is subjected to lateral motion such as lateral oscillation with one or more degrees of freedom together with modulation of a friction reducing oscillation in a manner that can create a shear force on the user's finger or on an object on the device.