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Automatic Voltage Offset Zeroing for Multiple Servo Loop Disk Files

IP.com Disclosure Number: IPCOM000060966D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Ell, TE: AUTHOR

Abstract

The method for automatically zeroing out voltage offsets on multiple servo loop disk files eliminates the need for using operational amplifiers with low input offset voltages, which are expensive, or potentiometers, which require manual adjustments. The figure shows a portion of an electronic tachometer. The tachometer generates a velocity signal by differentiating the "+position" signal and integrating the "+current sense in" signal. These two outputs are then combined based on frequency content. In the figure, only those portions of the tachometer that were changed or added to for zeroing offsets are labeled. The zeroing of offsets depends on two conditions: one, that the seek mode only lasts a finite maximum time, and two, that the electronic tachometer is not used during tack follow. Both of these condition are met.

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Automatic Voltage Offset Zeroing for Multiple Servo Loop Disk Files

The method for automatically zeroing out voltage offsets on multiple servo loop disk files eliminates the need for using operational amplifiers with low input offset voltages, which are expensive, or potentiometers, which require manual adjustments. The figure shows a portion of an electronic tachometer. The tachometer generates a velocity signal by differentiating the "+position" signal and integrating the "+current sense in" signal. These two outputs are then combined based on frequency content. In the figure, only those portions of the tachometer that were changed or added to for zeroing offsets are labeled. The zeroing of offsets depends on two conditions: one, that the seek mode only lasts a finite maximum time, and two, that the electronic tachometer is not used during tack follow. Both of these condition are met. Assume the file is track following or retracted. During these times the tachometer is not needed for controlling the actuator and therefore can be zeroed out. Switches SW2-a and SW2-c are open, and switches SW2-b and SW2-d are closed. This shorts the input to the differentiator path after the differentiator. The circuit is built using all four switches so that only one storage element, in this case capacitor C1, is needed. Switches SW1-a, SW1-b and SW1-c are open. The closing of SW1-d forms a closed loop circuit with the output of u4, becoming the input to the circuit. The output...