Abstract: A hard-disk drive (HDD). The HDD includes a main control circuit. The main control circuit includes a frequency-hunting peak filter. The frequency-hunting peak filter includes a peak filter wherein a gain at a center frequency becomes finite and a reciprocal of the transfer function is represented by z/FD in z-transform space. The denominator of the transfer function of the peak filter that is represented by FD, has a real part that becomes zero at the center frequency and an imaginary part that becomes a positive number at the center frequency. In addition, the frequency-hunting peak filter includes a frequency updating unit that updates the center frequency to converge onto a frequency of disturbance by obtaining a comparative relation between the center frequency and the frequency of disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by z/FD.

Abstract: Embodiments of the present invention provide a disk drive capable of appropriately measuring non-linearity in a head position control system, and a control method therefore. According to one embodiment, a magnetic disk drive inputs a reference signal SR into a voice coil motor, inputs into the voice coil motor a control signal SC in which a harmonic component resulting from the reference signal SR is suppressed, and measures an error signal PES that may be obtained in the state where the reference signal SR and the control signal SC, in which the harmonic component is suppressed, are input in the voice coil motor.

Abstract: Embodiments of the present invention provide a recording disk capable of curtailing the amount of servo data to be stored thereon, and a disk drive. According to one embodiment, servo data area sets each of a first servo data area and plural second servo data areas arranged in that order in a read direction HR are arranged successively on each of tracks of a magnetic disk. Stored in a second sector data section included in the second servo data area is data representing a distance in the read direction HR from the position of the first servo data area to that of the same second servo data area. The amount of data stored in the second sector data section is less than that of data stored in a first sector data section included in the first servo data area.

Abstract: An infinite impulse response (IIR) filter circuit in accordance with an embodiment of the invention has transfer function coefficients that are adaptively changed. Using a Nth-order polynomial A(z) and a polynomial B(z) whose order is not higher than N, the transfer function is defined by L ? ( z ) = B ? ( z ) A ? ( z ) ; where ? i = 0 - 1 ? ? ( z 2 + 1 - 2 ? ? k i ? z ) = 1 is also defined. The polynomial A(z) is transformed to make the term of the Nth power of z equal to 1.

Abstract: A hard-disk drive (HDD). The HDD includes a main control circuit. The main control circuit includes a frequency-hunting peak filter. The frequency-hunting peak filter includes a peak filter wherein a gain at a center frequency becomes finite and a reciprocal of the transfer function is represented by z/FD in z-transform space. The denominator of the transfer function of the peak filter that is represented by FD, has a real part that becomes zero at the center frequency and an imaginary part that becomes a positive number at the center frequency. In addition, the frequency-hunting peak filter includes a frequency updating unit that updates the center frequency to converge onto a frequency of disturbance by obtaining a comparative relation between the center frequency and the frequency of disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by z/FD.

Abstract: Embodiments of the present invention help to provide a magnetic disk drive that is capable of reducing a time period necessary for positioning a magnetic head when positioning the magnetic head by use of a dual-stage actuator. According to one embodiment, a main control circuit of a magnetic head device selects one of a seek mode and a positioning mode. The seek mode is to set a coarse adjustment control system to be a stable system by not causing control of a piezoelectric actuator to be performed by a fine adjustment control circuit. The positioning mode is to set the coarse adjustment control system to be an unstable system and setting a total control system inclusive of the coarse adjustment control system and a fine adjustment control system to be the stable system by causing the control of the piezoelectric actuator to be performed by the fine adjustment control circuit. Thereby the main control circuit causes the control system to operate.

Abstract: Embodiments of the invention provide a servo information write method that makes it possible to properly locate the last-written servo information even when old servo information is overwritten by new servo information. In one embodiment, a servo track writer controller, which is within a servo track writer, reads a serial number (S/N) from a HDD (step 101), and acquires a magnetic disk drive servo information write count (P-ID) from a manufacturing process host (step 102). The next step (step 103) is then performed to control a positioner and a read/write channel so as to start writing servo information onto a magnetic disk. Servo information is sequentially written until the last track is written into (step 104). When the Nth servo information is to be written, a P-ID (N) is written subsequently to a burst signal (step 105). When the last track is written into in step 104, step 106 is performed to notify the manufacturing process host that the Nth servo information write is performed.

Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive capable of alleviating an adverse effect of vibrations inherent to a housing on positioning control, reducing the adverse effect over other frequency range, and stabilizing the positioning control. In a magnetic disk drive according to embodiments of the present invention, a position control circuit that controls the position of a magnetic head produces a signal, based on which the position of the magnetic head is controlled, according to positional information read by the magnetic head. The signal is transmitted via a multi-rate filter circuit that decreases a sensitivity function relevant to a predetermined object frequency by a first predetermined gain, and suppresses an increase in the sensitivity function relevant to frequencies lower than the object frequency to a second predetermined gain.

Abstract: Embodiments of the present invention provide a disk drive capable of appropriately measuring non-linearity in a head position control system, and a control method therefor. According to one embodiment, a magnetic disk drive inputs a reference signal SR into a voice coil motor, inputs into the voice coil motor a control signal SC in which a harmonic component resulting from the reference signal SR is suppressed, and measures an error signal PES that may be obtained in the state where the reference signal SR and the control signal SC, in which the harmonic component is suppressed, are input in the voice coil motor.

Abstract: Embodiments of the present invention provide a recording disk capable of curtailing the amount of servo data to be stored thereon, and a disk drive. According to one embodiment, servo data area sets each of a first servo data area and plural second servo data areas arranged in that order in a read direction HR are arranged successively on each of tracks of a magnetic disk. Stored in a second sector data section included in the second servo data area is data representing a distance in the read direction HR from the position of the first servo data area to that of the same second servo data area. The amount of data stored in the second sector data section is less than that of data stored in a first sector data section included in the first servo data area.

Abstract: Embodiments of the invention reduce the information (storage) overhead for determining the rotational position of a magnetic disk medium, as well as reducing the rotational position detection time. In one embodiment, a sector servo magnetic disk medium is configured such that: each track is divided into blocks each including a series of sectors; each block stores a positional information bit string as rotational position information; the positional information bit string is made up of a position code and an identification code, the position code including a block number, the identification code being used to identify the start or the end of the position code; and each bit of the positional information bit string is stored in a different sector of the block. When each block is made up of 12 sectors, for instance, if the block number is denoted as b0b1b2b3b4b5, the positional information bit string may be expressed as 00001b0b1b21b3b4b5, where the first 5 bits “00001” constitute an identification code.

Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: Embodiments of the present invention help to provide a magnetic disk drive that is capable of reducing a time period necessary for positioning a magnetic head when positioning the magnetic head by use of a dual-stage actuator. According to one embodiment, a main control circuit of a magnetic head device selects one of a seek mode and a positioning mode. The seek mode is to set a coarse adjustment control system to be a stable system by not causing control of a piezoelectric actuator to be performed by a fine adjustment control circuit. The positioning mode is to set the coarse adjustment control system to be an unstable system and setting a total control system inclusive of the coarse adjustment control system and a fine adjustment control system to be the stable system by causing the control of the piezoelectric actuator to be performed by the fine adjustment control circuit. Thereby the main control circuit causes the control system to operate.

Abstract: An information recording method in a rotating storage apparatus comprising a rotating recording medium for recording information, a head for performing at least a write operation onto the rotating recording medium, and an acceleration sensor for detecting a shock. The method comprises outputting a shock out signal if an output from the acceleration sensor exceeds a predetermined threshold. A signal is output at a first level for a write inhibit period in response to the input of the shock out signal, where the write inhibit period is selected based at least in part on a time span in which the output of the acceleration sensor exceeds the predetermined threshold. Writing to the rotating recording medium is prohibited during the write inhibit period.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive capable of alleviating an adverse effect of vibrations inherent to a housing on positioning control, reducing the adverse effect over other frequency range, and stabilizing the positioning control. In a magnetic disk drive according to embodiments of the present invention, a position control circuit that controls the position of a magnetic head produces a signal, based on which the position of the magnetic head is controlled, according to positional information read by the magnetic head. The signal is transmitted via a multi-rate filter circuit that decreases a sensitivity function relevant to a predetermined object frequency by a first predetermined gain, and suppresses an increase in the sensitivity function relevant to frequencies lower than the object frequency to a second predetermined gain.

Abstract: Embodiments of the invention provide a magnetic disk drive that exhibits excellent overall stability of a feedback control system even when the preset frequency for a peak filter significantly changes. In one embodiment, the symbol P denotes a VCM model, which outputs a head current position signal. The symbol C denotes a controller. The controller inputs a position error signal PES that is derived from a head current position signal output from the P, and outputs to addition point a control signal of a drive device for moving a magnetic head. Signal x to which disturbance noise is added enters a peak filter. The output y from the peak filter is output to addition point via a phase determination filter and added to a control signal output from the controller.

Abstract: Embodiment of the invention inhibit an effect of repeatable runout errors without expanding servo data areas of the magnetic disk. With regard to low frequency components of positional information read by a magnetic head, which are substantially equivalent to a rotational frequency of a magnetic disk, a servo controller according to one embodiment includes: a peak filter for removing such low frequency components from the positional information; a correction module for correcting the positional information by using repeatable runout compensation data; a phase correction circuit for calculating the amount of control based on an output of the correction module; and an adding circuit for adding an output of the peak filter and an output of the phase correction circuit.

Abstract: Embodiments in accordance with the present invention provide an infinite impulse response (IIR) filter circuit which can operate stably even when the coefficients are adaptively changed. The IIR filter circuit in accordance with an embodiment of the present invention has transfer function coefficients that are adaptively changed. Wherein using a Nth-order polynomial A(z) and a polynomial B(z) whose order is not higher than N, the transfer function is defined by L ? ( z ) = B ? ( z ) A ? ( z ) ; where ? i = 0 - 1 ? ? ? ( z 2 + 1 - 2 ? ? ? k i ? z ) = 1 is also defined. The polynomial A(z) is transformed to make the term of the Nth power of z equal to 1.

Abstract: Embodiments of the invention eliminate noise from burst signals by use of a reliable and simple method. In one embodiment, the read processor of the HDD has a noise elimination circuit. The noise elimination circuit retains multiple integral values of the waveform absolute values for each period in the burst signals read out from the head, then removes a maximum value and/or a minimum value from the multiple integral values, and transmits the remainder as noise-eliminated signal data. The noise elimination circuit is a circuit for eliminating noise from an N number of periods of burst signal data, and this circuit integrates the absolute values of the waveforms for each period in the N number of periods of burst signal data, compares the integral values of each period with one another, and outputs the remainder obtained by removing the maximum and minimum integral values, to the servo data decoder of the following stage.