Control system for a data storage device with constraint

#The present invention relates generally to data storage devices, and more particularly but not by limitation to control systems for data storage devices.

#Data storage devices store digital information on a rotating disc or data storage medium. Data storage devices include a head having a transducer element to read data from or write data to the disc or data storage medium. Heads are coupled to a primary or first actuator assembly which is energized to position the head relative to the disc surface for read-write operations. The primary actuator is coupled to a servo control system to provide head position control. Areal density is increasing requiring improved position control. In particular, as tracks per inch increase, track positioning error must decrease.

#Secondary actuators or microactuators have been proposed to improve track misregistration or track positioning. Typically, the secondary actuator or microactuator moves the head over a smaller stroke or displacement to provide micropositioning for dual stage actuation. The primary, or first actuator, and the secondary actuator, or microactuator, collectively provide head positioning. Control system architectures for single actuation devices are not designed to optimize servo control for the secondary actuator or microactuator relative to system constraints. Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.

#FIG. 1 is a perspective illustration of an embodiment of a data storage device.

#FIG. 2 is a schematic illustration of an embodiment of a control system for an actuator to position a head for read-write operations.

#FIG. 3 is a schematic illustration of an embodiment of a control system for a dual stage actuator assembly of the present invention.

#FIG. 1 is a perspective illustration of an embodiment of a data storage device 100 for storing digital information. Device 100 includes a plurality of discs 102 (or single disc) to store digital information. The discs 102 are supported for rotation as illustrated by arrow 104 relative to a base chassis 106 by a spindle motor (not shown). Heads 108 (only one shown in FIG. 1) are coupled to an actuator assembly 110 including a voice coil motor or actuator 112 which is energized to position the heads 108 relative to data tracks on the disc to read data from or write data to the disc through interface with a host system 114.

#As previously described, areal density and tracks per inch is increasing, demanding improved head positioning control. The size and response of the actuator 112 limits response or positioning control of the head 108. Microactuators as illustrated in block 116 are coupled to the head to provide a smaller actuation stroke for fine head positioning control relative to the voice coil motor or primary actuator 112.

#In particular, in the illustrated embodiment, heads 108 are supported relative to an actuator E-block 120 rotationally coupled to the base chassis 106. Energization of the voice coil motor 112 rotates the actuator E-block 120 to move the heads along a positioning stroke or arcuate path 122 between an inner diameter and outer diameter of the disc. Heads are coupled to suspension assemblies 124 (only one shown in FIG. 1) coupled to actuator arms 126 (only one shown in FIG. 1) of the actuator E-block 120.