Browse Prior Art Database

Compact Diskette Drive

IP.com Disclosure Number: IPCOM000040766D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Karidis, JP: AUTHOR

Abstract

Dual actuators provide controlled two-degree-of-freedom (2-DOF) motion of a read/write head assembly over a stationary recording medium, using a dual actuator to find the recording track and provide head/disk relative motion. Fig. 1 shows an extremely small, dual-actuator four-link system 1-4 which serves to move a read/write head assembly 5 over a given area of a stationary magnetic storage disk 6. The read head is magnetoresistive to allow the data to be read independently of the head velocity (assuming, of course, that the velocity is known). The head assembly 5 is preloaded lightly against the recording medium 6 to allow high data-recording densities without excessive wear.

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Compact Diskette Drive

Dual actuators provide controlled two-degree-of-freedom (2-DOF) motion of a read/write head assembly over a stationary recording medium, using a dual actuator to find the recording track and provide head/disk relative motion. Fig. 1 shows an extremely small, dual-actuator four-link system 1-4 which serves to move a read/write head assembly 5 over a given area of a stationary magnetic storage disk 6. The read head is magnetoresistive to allow the data to be read independently of the head velocity (assuming, of course, that the velocity is known). The head assembly 5 is preloaded lightly against the recording medium 6 to allow high data-recording densities without excessive wear. The medium 6 contains buried servo information, such as an appropriate capacitive pattern under the recording layer, or coded magnetic information which is sensed by the head assembly 5 to provide accurate 2-DOF position information to the dual head-positioning actuators. The technologies of magnetoresistive heads, contact recording, and buried servo techniques are known.

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There are many different coordinate systems for the 2-DOF head positioning, and many ways to produce the desired motion. However, some coordinate systems are more convenient in terms of the magnetic medium format, and utilize more conventional technology than others. Polar coordinate systems are particularly attractive. Fig. 2 shows dual-actuator links 1-4 in polar coordinates. Two rotary pancake motors 7-8 independently control the angular orientation of two concentric output shafts 9-10 (similar to the concentric output shafts which drive the hands of a clock) and four-element linkage 1-4. The exact dimensions of the links depend on the range-of-motion, transmission angle, and other standard linkage design considerations.

The recording head assembly 5 is mounted to link 3 at its distal end; the radius from the shaft to head 5 is a nonlinear function of the difference between the output shaft angles, while the angular position of head 5 relative to a fixed radial line is a function of the sum of the output angles. Thus, head 5 can be positioned anywhere within a ring sector whose minimum and maximum radii are determined by the linkage parameters and whose total angle is only limited by wiring considerations. The repeatability of the head positioning depends strongly on the accuracy of the linkage bearings. This potential problem is alleviated by the use of flexural joints (if the angular excursions of the joints are small) or by using leaf springs mounted between the links so as to preload the bearing in one direction by trying to open the joint angle. Operation is as follows:

The storage medium is loaded by inserting a disk 6 (which may or may not be round) into retaining grooves on the inside of a hinged door. The door is closed, bringing the storage medium into a fixed position above the head-positioning assembly. The angle (or phase) between the...