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Integrated Flexural Theta-Mount System For Reducing Effect of Vibration in Disk Drives

IP.com Disclosure Number: IPCOM000016664D
Publication Date: 2003-Jul-08
Document File: 8 page(s) / 212K

Publishing Venue

The IP.com Prior Art Database

Abstract

An integrated flexural theta-mount system for a disk drive incorporates a series of varying length flexures that are combined with an external and internal frame, therefore comprising a singular system for theta rotation. The integrated flexural system is embodied in a way to preserve the present industry standard form factor of a 3.5 inch disk drive while solving the associated read/write position errors resulting from sources of vibration.

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  Integrated Flexural Theta-Mount System For Reducing Effect of Vibration in Disk Drives

      Traditional approaches to vibration attenuation in disk drives were to isolate the sensitive component from the source of the vibration by introducing vibration dampening or isolation mounting systems. In the case of a closed loop position sensing device, such as the control and positioning servo electronics of a disk drive system, filtering algorithms are employed to correct for position errors induced from known periodic dynamics. A contemporary method for correcting for the seek induced transient dynamics is to employ piezoelectric sensors to detect vibrations and to use the sensed information to correct position error using a feed forward algorithm. However, as the track density of disk drive continues to increase algorithmic approaches will become more difficult to implement as the cost of ultra sensitive sensors will become prohibitive in an already cost sensitive industry. Also traditional isolation design approaches typically require additional drive volume to isolate the vibration from the drive.

    In published PCT patent application WO-0148758A1, published 7/15/2001, a method of incorporating a passive isolation system is disclosed which builds on a "Theta" mounting scheme. A rigid body motion can take place along three linear (X, Y, Z) and three angular (phi, theta, psi) coordinates (see Fig. 1a). A disk drive with rotary actuator-based positioning mechanism is mounted so that it can rotate freely about an axis normal to the plane of actuator motion. The integrated flexural system provides sufficient angular rotational freedom along theta coordinate mean while it constrains the disk drive along all other 5 coordinates. No substantial linear or angular freedom of motion along the remaining 5-coordinates is allowed by the mount. The maximum amplitude of rotational degree of freedom is about 300 times smaller than the actuator rotation angle in a typical 3.5" drive. This could amount to about 0.1 degree. The pivotal axis of the base plate rotation must pass through the center-of-gravity of the rotationally free disk drive hardware in order to eliminate external linear vibration coupling into theta motion of the disk drive. Ideally, the axis of rotation of the spindle motor would coincide with the pivotal axis of the base plate to minimize the harmonic excitation of the base plate due to spindle mass imbalance. However, it can be assumed that the spindle motor has been balanced or filtering algorithms have been employed to subdue any excitations associated from the spindle motor to the control system. In addition, the actuator is assumed to be mass balanced about its own pivotal axis. The rotational freedom for the base plate mount, in an integrated flexural system, is realized using a group of integrated flexures. The mount system can be an integral part of a disk drive, or it could be offered as a part of the computer mounting structure.

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