Patents by Inventor Sang Chu

Sang Chu has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20060221492
    Abstract: A hard disk drive that redefines a notch filter of the drive. The update process may include initially disabling all notch filters and inducing a seek operation of the disk drive heads. A position error signal is read during a settling time of the seek operation and processed to determine the frequency of the signal. The frequency is selected as a resonant frequency if the error signal magnitude exceeds a threshold value. The notch filter is then redefined in accordance with the selected resonant frequency. The controller may also perform a routine to determine whether the resonant frequency is above or below a Nyquist frequency. Unlike prior art techniques, the method disclosed can obtain the resonant frequency without sweeping the excitation signal of the disk drive voice coil motor.
    Type: Application
    Filed: April 1, 2005
    Publication date: October 5, 2006
    Inventors: Cheol Park, Sang Chu, Yong Lee
  • Publication number: 20060187571
    Abstract: The invention applies to servo controllers for at least the voice coil motor of a hard disk drive. Today, many control algorithms require 80 to 90 percent of the sampling period to complete their calculation of the next control, making computation time delay no longer negligible. The invention accommodates the transport delay, such as computation time delay, into the state estimator and into the whole control system. Experimental results using a commercial hard drive, as well as simulation results, show that the invention's method effectively improves the hard disk drive control system stability by increasing the phase margin and gain margin. The invention includes the method of operating the servo-controller, as well as the apparatus implementing that method. The invention also includes hard disk drives containing servo-controllers implementing the method, and program systems residing in accessibly coupled memory to a computer within the servo controller implementing the method.
    Type: Application
    Filed: April 3, 2006
    Publication date: August 24, 2006
    Inventors: Young-Hoon Kim, Sang Chu, Seong-Woo Kang, Dong-Ho Oh, Yun-Sik Han, Tae Hwang
  • Publication number: 20060103972
    Abstract: A hard disk drive with a disk that has a plurality of servo sections and a plurality of data sections. At least some of the data sections have a track density different than the track density of the servo sections. The disk drive has a controller that may convert a data track number to a servo track number to compensate for the different densities. The conversion may be required to conduct a seek routine to access a data track associated with the data track number.
    Type: Application
    Filed: November 12, 2004
    Publication date: May 18, 2006
    Inventors: Sang Chu, Kang Lee, Keung Cho, Jong Kim, Jung Lee, Cheol Park, Hae Lee
  • Publication number: 20060103964
    Abstract: A hard disk drive that changes a variable write parameter of a head during a write operation. The controller can change the variable write parameter to compensate for a transient temperature profile of the head during the initial stage of a write operation. By way of example, the controller can provide a relatively large overshoot control signal of a head during the writing of a first sector of a write operation. The value of the overshoot control signal may be decremented for a second sector, a third sector etc., until the head attains a thermal steady state at which point the overshoot control signal is provided with a constant value.
    Type: Application
    Filed: November 12, 2004
    Publication date: May 18, 2006
    Inventors: Sang Chu, Kang Lee, Jong Yun, Yeong Lee
  • Publication number: 20060028755
    Abstract: The present invention is a method and apparatus for positioning a read/write head in a hard disk drive. The method comprises providing a disk having a at least one side with a plurality of tracks, where each of the tracks has a servo field with servo bits. The servo bits are read to provide a position signal for positioning a read/write head. The method determines a difference in position between an initial and a subsequent position of the read/write head on a track, where the subsequent location occurs after the read/write head has moved one revolution from the initial position on the track. The initial and subsequent positions are offset laterally. The method generates a compensation signal based on the initial position, the subsequent position and the difference. The position signal and the compensation signal are combined to provide a compensated position signal for positioning the read/write head. Various embodiments are described.
    Type: Application
    Filed: October 7, 2005
    Publication date: February 9, 2006
    Inventors: Tung Nguyen, Sang Chu, Jun Shim, Kang Lee, Soo Choi, Seong Yu
  • Publication number: 20060023340
    Abstract: The invention applies to servo controllers for at least the voice coil motor of a hard disk drive. Today, many control algorithms require 80 to 90 percent of the sampling period to complete their calculation of the next control, making computation time delay no longer negligible. The invention accommodates the transport delay, such as computation time delay, into the state estimator and into the whole control system. Experimental results using a commercial hard drive, as well as simulation results, show that the invention's method effectively improves the hard disk drive control system stability by increasing the phase margin and gain margin. The invention includes the method of operating the servo-controller, as well as the apparatus implementing that method. The invention also includes hard disk drives containing servo-controllers implementing the method, and program systems residing in accessibly coupled memory to a computer within the servo controller implementing the method.
    Type: Application
    Filed: July 29, 2004
    Publication date: February 2, 2006
    Inventors: Young-Hoon Kim, Sang Chu, Seong-Woo Kang, Dong-Ho Oh, Yun-Sik Han, Tae Hwang