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Complementary Controller for File Products and Method for Controlling Same

IP.com Disclosure Number: IPCOM000034280D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Green, MR: AUTHOR [+3]

Abstract

To control the head position in file products (magnetic disk files), a number of problems have to be solved in order to produce a product which has high yields and high enough robustness to avoid failing in the field if file tolerances change due to aging or changing environments. These problems are Repeatable Run Out (RRO), Non-Repeatable Run Out (NRRO), external vibration, variation in part tolerances, both electrical and mechanical and, to a limited extent, resonances. The present method of controlling a file actuator substantially solves these problems and consists of receiving a measured position error signal (PES) from a file and, by using either state feedback or a compensation network, a current is derived which is then fed back into the file voice coil motor (VCM) to stabilize the file actuator.

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Complementary Controller for File Products and Method for Controlling Same

To control the head position in file products (magnetic disk files), a number of problems have to be solved in order to produce a product which has high yields and high enough robustness to avoid failing in the field if file tolerances change due to aging or changing environments. These problems are Repeatable Run Out (RRO), Non-Repeatable Run Out (NRRO), external vibration, variation in part tolerances, both electrical and mechanical and, to a limited extent, resonances. The present method of controlling a file actuator substantially solves these problems and consists of receiving a measured position error signal (PES) from a file and, by using either state feedback or a compensation network, a current is derived which is then fed back into the file voice coil motor (VCM) to stabilize the file actuator. When using the complementary controller, a standard control loop is still used; however, the complementary controller also receives the PES and VCM current and modifies the VCM current such that the file will exhibit the same dynamic responses as a theoretical model of the file would produce. Referring to the figure, the F block represents the file. Though it is shown in the diagram by K3/S2, in reality, it includes variations in gain and unmodeled mechanical resonances. This block also includes a notch filter to attenuate some of these resonances, thus helping to ensure stability in the inner (F-D) loop. The M block includes the modeled file which has the gain and frequency response of the desired file.

This would ideally be represented by K3/S2 . However, due to implementation limitations, it is shown by K1S

S3+2Z1W1S2+W12S+K1...