Browse Prior Art Database

Time Optimal Control of Final Approach

IP.com Disclosure Number: IPCOM000089361D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Oswald, RK: AUTHOR

Abstract

When the heads of a magnetic disk file approach to within a predetermined small distance x(1) of the target track center during a seek motion, the final approach is controlled by a feedforward current trajectory in combination with a minor position feedback loop.

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Time Optimal Control of Final Approach

When the heads of a magnetic disk file approach to within a predetermined small distance x(1) of the target track center during a seek motion, the final approach is controlled by a feedforward current trajectory in combination with a minor position feedback loop.

Referring to the figure, a positioning motor together with heads, carriage and disks is shown as mechanical system 1. The motor positions the heads in response to control current from power amplifier 2, and the present position x of the heads is detected by position transducer 3 which may, in practice, be a servo head and servo disk surface. The approach motion is primarily controlled by a predetermined feedforward current signal I(F) applied at terminal 4 through switch S(1) to summing junction 5. During the final approach such a feedforward current has a direction and a substantially constant magnitude corresponding to maximum deceleration of the motor. Deviations between the actual system and the nominal system, implicit in the feedforward current trajectory, are corrected by means of a minor position feedback loop in which the actual head position x is compared with a reference position signal X, derived from the feedforward current. The difference (position error) between X and x is derived in summing junction 6, amplified in error amplifier 7, and summed with the feedforward current in junction 5.

The reference position signal X is generated by, firstly, integ...