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Accessing Method for Track Following Disk Files

IP.com Disclosure Number: IPCOM000081908D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Case, WJ: AUTHOR [+2]

Abstract

Fig. 1 shows a typical servo loop position error signal generated in a servo head, as it is moved from track-to-track by an actuator mechanism forming part of a track-following disk file. The portion of the signal waveform shown is that generated as the head crosses three servo tracks. The tracks have been labelled N-1, N, N+1. The error signal shown has a negative feedback portion 1, which enables the position loop electronics to control the actuator to stop the servo head on track N, or indeed on any other track which is an even number of tracks away from track N.

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Accessing Method for Track Following Disk Files

Fig. 1 shows a typical servo loop position error signal generated in a servo head, as it is moved from track-to-track by an actuator mechanism forming part of a track-following disk file. The portion of the signal waveform shown is that generated as the head crosses three servo tracks. The tracks have been labelled N-1, N, N+1. The error signal shown has a negative feedback portion 1, which enables the position loop electronics to control the actuator to stop the servo head on track N, or indeed on any other track which is an even number of tracks away from track N.

If the error signal polarity is reversed when the servo head is stationary over track N, then the head will move away from track N towards either track N-1 or track n+1. In this case, the direction of motion will be random, but if the head is given an initial displacement in the desired direction it will continue to move in that direction to stop over the required track. Thus, by reversing the error signal polarity in a controlled manner as each track is crossed, track accessing operations can be performed. Further, by controlling the phasing of the polarity reversals with respect to the error signal phase, the servo head can be accelerated or retarded at will during the accessing operation.

Fig. 2 shows the waveforms in a track access operation using this technique. The head actuator mechanism is given a small initial displacement in the desired directi...