Abstract: The present invention provides a digital filter which is capable of preventing filter outputs from being discontinuous when a filter characteristic is changed. Initially, a servo assistant (SA) computes parameters for computing servo data, and based on the computed parameters, the SA judges an operating mode. If the mode has been changed, the SA will advance in processing. Next, the parameters of a filter are changed in correspondence with the judged operating mode, and the initial values of the interior variables of the filter are set to appropriate values.

Abstract: Methods and systems for detecting and correcting for undesirable vibrations impacting the servo systems in data storage devices. A detection technique is provided wherein a detection filter is configured to scan a position signal of the servo system across a range of frequencies, and, at each respective scanned frequency, record an amplitude associated therewith. The recorded amplitudes are examined to determine whether any exceed a threshold, thereby locating a peak frequency of the vibration. Using the detected peak frequency of the vibration, a corrective filter is configured to operate about the peak frequency of vibration, thereby reducing its impact on the position signal in the servo system.

Abstract: An improved system and method for implementing a rotary memory device, including a host system and a disk-shaped memory medium storing position information, or a servo address mark (SAM). If a head fails to read a valid SAM, a dummy SAM is generated to prevent an arm with a read/write head from entering a neutral state. If the normal state cannot be restored within a fixed number of intervals, the system goes into the emergency brake control mode. In this emergency brake control mode, the direction of the head is determined, and the VCM current is applied in such a way drive the arm in the opposite direction. Damage to the magnetic medium and subsequent data loss problems are reduced because the velocity of the head is reduced to a safe level.

Abstract: A system for preventing off track data write operations in data storage devices such as hard disk drives. In a preferred embodiment, the amplitude of a head output signal is monitored. The output signal amplitude value is determined by measuring the voltage of a capacitor used in a Variable Gain Amplifier (VGA) in an Automatic Gain Control (AGC) circuit of a hard disk drive channel unit. The measured head output signal amplitude is compared with a previously determined minimum normal head output signal amplitude reference value to determine whether the head output signal amplitude is within a normal operating range. If the measured value is less than the reference value then the head is in an off track position, and the data write operation is inhibited. Radial position dependent amplitude reference values can also be used.

Abstract: A read/write head servo control system for data recording devices, wherein a method of compensating initial values is utilized to generate a control signal to move the head from an initial position to a target position. The method estimates and stores multiple position compensation values. A first control signal moves the head from an initial position to a target position. Head position values are sampled as the head moves. Head position deviation values are calculated for the sampled position values. The head position values are utilized to select a set of estimated position compensation values. These values are in turn utilized to generate a second control signal, which is then utilized to control the position of the head.

Abstract: A read/write head servo control system for data recording devices, wherein a method of compensating initial values is utilized to generate a control signal to move the head from an initial position to a target position. The method estimates and stores multiple position compensation values. A first control signal moves the head from an initial position to a target position. Head position values are sampled as the head moves. Head position deviation values are calculated for the sampled position values. The head position values are utilized to select a set of estimated position compensation values. These values are in turn utilized to generate a second control signal, which is then utilized to control the position of the head.

Abstract: A spindle motor start up method wherein a torque balance between the stator and rotor is broken so as to avoid startup malfunctions, and thereby improve motor startup time in spindle motors prone to startup malfunctions, such as hard disk drive motors having a 4:3 ratio of the number of rotor magnetic poles to the number of stator slots.

Abstract: The present invention teaches the realization of a stable feedback control by selecting an optimal notch filter in an apparatus, such as a hard disk drive, that employs a positioning apparatus, such as an actuator, for positioning an object. The present invention further teaches the derivation of a frequency characteristic of a control loop excluding a notch filter by employing a method that does not damage a positioning apparatus. The present invention further teaches the method of adjusting a notch filter in accordance with a change of the resonant frequency of an actuator caused by the temperature fluctuations to prevent any deterioration of a feedback control performance.

Abstract: A magnetic head position detecting method is provided in which a first and a second position detection signal representative of a particular position of a magnetic head with respect to a magnetic disk is obtained. The first and the second position detection signal preferably is obtained by utilizing a burst pattern formed on the magnetic disk. Subsequently, a third position detection signal is generated by multiplying the first and the second position detection signals by a predetermined gain so that the third position detection signal changes linearly. The particular position of the magnetic head is detected by using the third position detection signal. In addition, a magnetic disk apparatus implementing the magnetic head position detecting method is provided.

Abstract: This invention relates to a technique for obtaining a desired laser power. In write mode the laser power in an optical disk drive is determined in accordance with a DAC value which controls a power supply for the laser, but the correlation between the laser power and the DAC value significantly varies depending on the efficiency of the individual laser diode or laser oscillator. Because the laser power in read mode has been adjusted to a predetermined value during manufacturing, the DAC value which generates the same laser power as the reading laser power is known and is used to generate the desired laser power, such as the writing laser power.