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1115results about "Track finding/aligning" patented technology

Read/write head including displacement generating means that elongates and contracts by inverse piezoelectric effect of electrostrictive effect

A read/write head includes a slider provided with an electromagnetic transducer element (or an optical module), an actuator, and a suspension. The actuator includes a fixed part, a movable part, and at least two beam members for coupling them together. The beam members have a displacement generating means that elongates and contracts by inverse piezoelectric effect or electrostrictive effect. The fixed part is fixed to the suspension, and the movable part is fixed to the slider. Upon the elongation and contraction of the displacement generator, the displacement generator deflects and the movable part displaces linearly, circularly or rotationally with respect to the fixed part, and the electromagnetic transducer element displaces in a linear or circular orbit, so that the electromagnetic transducer element intersects recording tracks. In the actuator, the fixed part, movable part and beam members are formed as an integrated single piece by providing a hole and/or a cutout in a sheet-like member constructed of a piezoelectric or electrostrictive material. The actuator of the structure illustrated is used for the positioning of a direction intersecting recording tracks. In this case, the total sum of voltages applied on the displacement generating means is controlled in such a manner that it is constant at any time, thereby controlling position fluctuations of the electromagnetic transducer element in the direction vertical to the recording medium surface.
Owner:TDK CORPARATION

Repeatable runout (RRO) compensation methods and apparatus for data storage devices

In one illustrative example, a method for use in reducing Repeatable Run Out (RRO) error in a data storage device involves obtaining an RRO measurement for each track of a limited number of N disk tracks; characterizing the RRO measurement for each track with real and imaginary values by performing a discrete Fourier transform (DFT) calculation on each RRO measurement; performing a least-squares fit on all of the real values to identify a first set of (n+1) coefficients of an nth-order polynomial function which is a function of disk track r and representable in the form Ai(r)=anrn+a(n−1)r(n−1)+ . . . +a1r+a0; and performing a least-squares fit on all of the imaginary values to identify a second set of (n+1) coefficients of an nth-order polynomial function which is a function of disk track r and representable in the form Bi(r)=bnrn+b(n−1)r(n−1)+ . . . +b1r+b0. RRO compensation is performed based on the relation DRRO(r, s)=Σi for all H {Ai(r)cos(i(s2π/total_sectors))+Bi(r)sin(i(s2π/total_sectors))} where DRRO is the estimated RRO error; r is a track number; s is a sector number at track number r; i is an RRO harmonic number; H is a set of harmonics to be compensated; and total_sectors is a total number of sectors along track number r. Advantageously, RRO variations across the disk can be accurately compensated for with use of a small amount of memory.
Owner:WESTERN DIGITAL TECH INC
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