Experimental analysis of squeal of read/write heads upon floppy-disk media

The measurement of low-amplitude vibration of small mechanisms is a difficult problem. This paper presents the results of refining a nonobtrusive optical method, previously discussed, capable of producing quantitative analog outputs proportional to displacements and rotations1. The fruit of the previous study was a device denoted as a laser reflectometer which could resolve rotations as small as 2 μ rad and displacements on the order of 0.1 mil. Refinements discussed here allow this system to resolve rotations as small as 0.035 μ rad and displacements as small as 7 μ in. In addition the refinements, which consist of an improvement in the optical sensors employed, provide outputs linearly proportional to the degrees of freedom in both the amplitude and frequency domains. This allows the separation of degrees of freedom in a fashion much simplified from the previous work. This device was implemented in an analysis of read/write head motion upon a traveling floppy disk enclosed in a jacket with specific interest in motions with frequency content in the 1- to 5-kHz range. The intent was to study read/write head-squeal phenomena and to design heads less susceptible to this phenomenon.