Measurement of Stiffness and Damping Characteristics of Computer Keyboard Keys

[+] Author and Article Information
Mark Nagurka

Department of Mechanical and Industrial Engineering,  Marquette University, P.O. Box 1881, Milwaukee, WI 53201-1881, USAmark.nagurka@marquette.edu

Richard Marklin

Department of Mechanical and Industrial Engineering,  Marquette University, P.O. Box 1881, Milwaukee, WI 53201-1881, USArichard.marklin@marquette.edu

J. Dyn. Sys., Meas., Control 127(2), 283-288 (Jun 01, 2005) (6 pages) doi:10.1115/1.1902823 History:

To determine the stiffness and damping of computer keyboard keys, a computer-controlled test rig that can measure computer key displacement, velocity, and contact force has been designed. The test rig, consisting of a single-axis stage carrying a probe for contacting keys, has been used to collect contact force and motion data as computer keys are depressed and released at constant velocities up to 80mms. Keys that employ a rubber-dome under their caps to achieve the necessary compliance and toggling action were tested. The results demonstrate a nonlinear stiffness force versus displacement characteristic at a given speed and the presence of damping-type forces that increase with key depression speed at a given displacement. In particular, the results indicate that the peak force at the 80mms rate of depression increases relative to the quasistatic (0.5mms) force level by over 12% for the “Enter,” “K,” and “Spacebar” keys. This paper describes the hardware and software configuration, and presents sample results of the stiffness and damping characteristics of keys during depression-return stroke tests.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Schematic of rubber-dome key mechanism and photograph of rubber domes

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Figure 2

Relationship between key force and key displacement, adapted from ISO/DIS 9241/4.2 standard (ISO, 1998 (14))

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Figure 3

Test rig: (a) side view; and (b) photograph

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Figure 4

Test device actuation and measurement block diagram showing subsystems

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Figure 5

Force-displacement of depression and release of rubber-dome keys at 0.5 and 80mm∕s speeds for (a) “Enter,” (b) “K,” and (c) “Spacebar”

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Figure 6

Peak and trough forces of three rubber-dome keys as a function of depression speed

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Figure 7

Damping force as a function of depression speed of rubber-dome keys at the peak force displacement for (a) “Enter,” (b) “K,” and (c) “Spacebar”



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