Browse Prior Art Database

Digital Velocity Reference Curve Anticipator

IP.com Disclosure Number: IPCOM000046935D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Pennington, DH: AUTHOR [+2]

Abstract

High performance disk files typically move their actuators to a new position by accelerating with full power, switching to decelerate mode at some appropriate point from the new position and then, following a reference velocity or trajectory curve, bringing the actuator to zero velocity at the new position. This is shown graphically in Fig. 1 by plotting velocity vs. distance to go, referenced to the new position. As seen in Fig. 1, the point at which the actuator switches occurs when its velocity intercepts the velocity reference curve. In practice, the velocity reference curve is lowered during acceleration to cause the actuator velocity to intercept the reference curve early (Fig. 2).

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Digital Velocity Reference Curve Anticipator

High performance disk files typically move their actuators to a new position by accelerating with full power, switching to decelerate mode at some appropriate point from the new position and then, following a reference velocity or trajectory curve, bringing the actuator to zero velocity at the new position. This is shown graphically in Fig. 1 by plotting velocity vs. distance to go, referenced to the new position. As seen in Fig. 1, the point at which the actuator switches occurs when its velocity intercepts the velocity reference curve. In practice, the velocity reference curve is lowered during acceleration to cause the actuator velocity to intercept the reference curve early (Fig. 2). This early switching or anticipation of the velocity reference curve compensates for the time it takes the current to reverse in the actuator coil. Without some means of anticipation, the actuator velocity would overshoot the reference curve. The above anticipation and switching are typically handled by analog methods. In a completely digital system, new techniques may be used. In a digital system, the velocity reference or trajectory curve would be stored digitally in a read-only memory (ROM). It would be accessed using a digital distance-to-go value. The output of the ROM would then be the corresponding reference or trajectory velocity. Digital Velocity Reference Curve Antic The system in Fig. 3 has no anticipation. A second ROM coul...