The invention is a method of characterizing the frequency response of the servo control system in a disk drive having a sampled servo system having a sampling rate and a nominal bandwidth, wherein the sampled servo system comprises a plant and a servo controller that controls the plant using a compensator and a gain element with a nominal open loop gain. The invention is, in more detail, a method for adaptively modifying the servo controller to compensate for plant variations which are incompatible with the nominal gain and bandwidth, including the steps of implementing a self-generated bode plot to determine a gain margin and a phase margin, and if the gain margin is not greater than a predetermined minimum, adjusting the open loop gain of the servo controller to provide a gain margin which is greater than the predetermined minimum at a bandwidth which is different than the nominal bandwidth; and adjusting the compensator to provide a phase margin which is greater than a predetermined minimum.

Disk drive capable of autonomously evaluating and adapting the frequency response of its servo control system

A disk drive is disclosed comprising a head, a disk surface, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop and a microactuator servo loop operable to actuate the head over the disk surface. A microactuator compensator in the microactuator servo loop is disabled, a sinusoid is injected into a control signal applied to the microactuator, and coefficients of a corresponding sinusoidal response in a DSA error signal of the DSA servo loop is measured. The sinusoid is injected into a model of the microactuator to generate a compensation signal. A gain of the microactuator is adjusted based on a VCM error signal and the coefficients of the sinusoidal response in the DSA error signal.

Disk drive adjusting microactuator gain by injecting a sinusoid into a servo control system

A disk drive is disclosed comprising a head, a disk surface, and a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface. A sensitivity of the microactuator is periodically measured over a lifetime of the microactuator. Each measured sensitivity is stored in a timeline log, wherein the timeline log represents a degradation curve of the microactuator over the lifetime of the microactuator.

Disk drive performing lifetime logging of microactuator sensitivity

A disk drive is disclosed comprising a head actuated over a disk, a spindle motor operable to rotate the disk, and control circuitry comprising a speed control loop operable to control a rotation speed of the disk. A rotation speed of the disk is measured, and a speed error is generated in response to the measured rotation speed. The speed error is processed with a compensator to generate a control signal, a disturbance is injected into the control signal to generate a modified control signal, and the modified control signal is applied to the spindle motor. An amplitude of the disturbance is ramped, and after ramping the amplitude of the disturbance, an open-loop gain of the speed control loop is estimated at a frequency of the disturbance, and at least one parameter of the compensator is adjusted in response to the estimated open-loop gain.

Disk drive tuning speed control loop for a spindle motor

A disk drive is disclosed comprising a head actuated over a disk, a spindle motor for rotating the disk, and a spindle motor control system comprising a servo compensator operable to generate a control signal applied to the spindle motor, the servo compensator comprising a programmable gain term (PGT). The disk is spun at a first speed RPM — 1 using a first value PGT — 1 selected for the PGT, and the disk is spun at a second speed RPM — 2 using a second value PGT — 2 selected for the PGT, wherein the second value PGT — 2 is generated in response to the first value PGT — 1 scaled by a function of a ratio of RPM — 2 to RPM — 1.

Disk drive adjusting gain of spindle motor compensator based on a ratio of spin speeds

In a positioning control device for a two-stage actuator having a coarse-movement actuator and a fine-movement actuator, a notch filter having a cutoff frequency fn is provided to a coarse-movement control loop, and the fine-movement actuator is driven by a sine wave of the frequency fn. At the frequency fn, a head position signal becomes identical with an output signal of the fine-movement actuator, by which the gain of the fine-movement actuator can be estimated by an adaptive identification unit with high accuracy based on the control input to the fine-movement actuator and the head position signal.

Positioning control device for two-stage actuator

A disk apparatus has a gain identifying apparatus for identifying a gain from a control signal for controlling each head to a detection position signal, a memory device to store the identified gain, and an apparatus for correcting the control signal on the basis of the gain at at time point when each head which is provided for each recording surface of disks is located at each of a plurality of track positions.

Disk apparatus and its control method

PROBLEM TO BE SOLVED: To provide a disk device equipped with an adaptive identifying means which presumes the input/output characteristics of a fine adjusting actuator at a high speed and with high accuracy SOLUTION: A notch filter 48 having a frequency fn is provided in a control loop for coarse motion and a fine adjusting actuator 40 is driven in the shape of a sinusoidal wave with the frequency fn The signal in the frequency fn of a head position signal Y45 becomes equal to the output signal 42 of the fine adjusting actuator As a result, the gain of the fine adjusting actuator can be presumed with high accuracy by an adaptive identifying means 61 from the operation signal Up50 of the fine adjusting actuator and the head position signal 45 COPYRIGHT: (C)2004,JPO

Masahito Kobayashi

Papers

Positioning control device for two-stage actuator

Disk apparatus and its control method

Positioning controller for two-stage actuators