Patents by Inventor Lilit Kovudhikulrungsri

Lilit Kovudhikulrungsri 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).

  • Patent number: 8080957
    Abstract: An object of the present invention is to provide a motor control device capable of suppressing voltage composite vector fluctuation to increase the output of a brushless motor, and a motor-driven power steering system using this device. The present control device calculates motor phase current command values based on a target current and a rotor rotational position detection value, calculates voltage command values based on the motor phase current command values and phase current detection values, and supplies phase currents to a three-phase brushless motor based on the voltage command values. The present control device outputs the phase current command values so that the absolute value of a composite vector of respective phase drive voltages is substantially a value ?3/2 times the power supply voltage.
    Type: Grant
    Filed: April 11, 2007
    Date of Patent: December 20, 2011
    Assignee: NSK, Ltd.
    Inventors: Tomohiro Miura, Masahiro Maeda, Yousuke Imamura, Lilit Kovudhikulrungsri
  • Publication number: 20090167224
    Abstract: An object of the present invention is to provide a motor control device capable of suppressing voltage composite vector fluctuation to increase the output of a brushless motor, and a motor-driven power steering system using this device. The present control device calculates motor phase current command values based on a target current and a rotor rotational position detection value, calculates voltage command values based on the motor phase current command values and phase current detection values, and supplies phase currents to a three-phase brushless motor based on the voltage command values. The present control device outputs the phase current command values so that the absolute value of a composite vector of respective phase drive voltages is substantially a value ?3/2 times the power supply voltage.
    Type: Application
    Filed: April 11, 2007
    Publication date: July 2, 2009
    Inventors: Tomohiro Miura, Masahiro Maeda, Yousuke Imamura, Lilit Kovudhikulrungsri
  • Publication number: 20090009127
    Abstract: A motor driving control device includes a current instruction value computing section 31 which computes a current instruction value for driving a brushless motor 12, a motor current detector 38 which detects a motor current of the brushless motor 12, a current controller 34 which computes a voltage instruction value based on the current instruction value and the motor current, and a rotation information detector 22 which detects an electric angle and a rotation angular velocity of the brushless motor, and the motor driving control device includes a disturbance compensation voltage computing section 41 which computes a disturbance compensation voltage value base on the current instruction value, the electric angle of the brushless motor, and the rotation angular velocity of the brushless motor, and a feed-forward compensator 35 which corrects a voltage instruction value outputted from the current controller based on the disturbance compensation voltage value computed by the disturbance compensation voltage com
    Type: Application
    Filed: July 3, 2008
    Publication date: January 8, 2009
    Applicant: NSK LTD.
    Inventors: Yousuke IMAMURA, Lilit KOVUDHIKULRUNGSRI, Shuji ENDO, Kenji MORI
  • Publication number: 20080297077
    Abstract: A motor drive control device includes: a generation part for generating a current command value; a current detection part for detecting a drive current of an electric motor; a motor feedback control part for controlling feedback of the electric motor based on the current command value and a drive current detection value; a prefilter with order of one or more for adjusting the current command value, the prefilter being interposed between the generation part and the motor feedback control part; and a series compensator with order of two or more for determining a voltage command value of the motor feedback control part based on the current command value adjusted by the prefilter and the drive current detection value of the electric motor.
    Type: Application
    Filed: October 16, 2007
    Publication date: December 4, 2008
    Applicant: NSK LTD.
    Inventors: Lilit KOVUDHIKULRUNGSRI, Kenji MORI
  • Patent number: 7382105
    Abstract: In a motor driving device where a motor having a winding wire with small inductance value is driven by a digital control means comprised of control means including a current command value calculating means, a current control means and a PWM control means whose sampling periods are different from each other, when discrete signals sampled by the respective control means are zero-order-held, a motor current includes a lot of higher harmonic waves due to a quantization error, thereby increasing a motor noise. When an n-th-order hold means is provided between the respective control means with different sampling periods, the quantization error can be reduced remarkably, and thus the higher harmonic wave components included in the motor current are reduced, thereby greatly reducing the motor noise.
    Type: Grant
    Filed: December 2, 2004
    Date of Patent: June 3, 2008
    Assignees: NSK Ltd., NSK Steering Systems Co., Ltd.
    Inventors: Shuji Endo, Masahide Saito, Kenji Mori, Lilit Kovudhikulrungsri, Toru Sakaguchi
  • Publication number: 20070296375
    Abstract: This invention provides a control method for a motor that calculates a voltage command value based on a difference between a current command value and a current detected value and controls a PWM based on the voltage command value. The control method includes steps of: detecting a failure or an undetectable state of a current detecting system; obtaining a current estimated value of a failure phase or an undetectable state phase by using the current detected value except the failure phase or the undetectable state phase when the failure or the undetectable state is detected; and continuously controlling the motor by using the current estimated value.
    Type: Application
    Filed: June 8, 2007
    Publication date: December 27, 2007
    Applicant: NSK LTD.
    Inventors: Toru SAKAGUCHI, Shuji ENDO, Lilit KOVUDHIKULRUNGSRI
  • Patent number: 7265509
    Abstract: The present invention provides an excellent electric power steering apparatus in which torque ripple caused by a quantization error of a current control system generated in case of slow steering state and steering holding state, namely, vibration and noise on a steering wheel can be suppressed. A current controller in which a steady state gain of feedback control is a finite value is used so as to be capable of suppressing the vibration and noise. Further, according to the present invention, a smoothing filter is included in a current control system so that the quantization error is smoothed so that the torque ripple is suppressed.
    Type: Grant
    Filed: July 15, 2005
    Date of Patent: September 4, 2007
    Assignee: NSK, Ltd.
    Inventors: Shuji Endo, Yuho Aoki, Kenji Mori, Toru Sakaguchi, Sakae Nejo, Hideaki Okazaki, Lilit Kovudhikulrungsri
  • Publication number: 20070107973
    Abstract: A motor drive control apparatus for controlling a motor has a main control part that performs a flux weakening control by a vector control of d-q axes and a rate-limit control part that controls a rate of change in a d axis current command value in the vector control. Further, there is provided a motor control apparatus for controlling a motor has a motor angular speed detection part that detects a motor angular speed of the motor and a motor control part having a current control system that controls the electric motor based on a motor current and a current command value. The motor control part calculate the current command value in which torque becomes constant by considering characteristics of the current control system based on a motor angular speed detected by the motor angular speed detection part.
    Type: Application
    Filed: October 23, 2006
    Publication date: May 17, 2007
    Inventors: ChunHao Jiang, Kenji Mori, Toru Sakaguchi, Lilit Kovudhikulrungsri
  • Publication number: 20070100524
    Abstract: In a control device for an electric power steering system for controlling a motor on the basis of an auxiliary steering command value calculated from a steering torque generated in a steering shaft and a vehicle speed, and a current detection value of the motor that applies an auxiliary steering force to a steering mechanism, the device comprises a damping compensation unit that calculates a basic damping compensation value on the basis of a steering speed and adjusts the basic damping compensation value on the basis of an SAT estimated value and the steering speed, wherein an adjusted damping compensated value that is adjusted in the damping compensation unit is added to the auxiliary steering command value.
    Type: Application
    Filed: November 1, 2006
    Publication date: May 3, 2007
    Inventors: Toru Sakaguchi, Lilit Kovudhikulrungsri
  • Publication number: 20070081799
    Abstract: In a motor driving device where a motor having a winding wire with small inductance value is driven by a digital control means comprised of control means including a current command value calculating means, a current control means and a PWM control means whose sampling periods are different from each other, when discrete signals sampled by the respective control means are zero-order-held, a motor current includes a lot of higher harmonic waves due to a quantization error, thereby increasing a motor noise. When an n-th-order hold means is provided between the respective control means with different sampling periods, the quantization error can be reduced remarkably, and thus the higher harmonic wave components included in the motor current are reduced, thereby greatly reducing the motor noise.
    Type: Application
    Filed: December 2, 2004
    Publication date: April 12, 2007
    Inventors: Shuji Endo, Masahide Saito, Kenji Mori, Lilit Kovudhikulrungsri, Toru Sakaguchi
  • Publication number: 20060012323
    Abstract: The present invention provides an excellent electric power steering apparatus in which torque ripple caused by a quantization error of a current control system generated in case of slow steering state and steering holding state, namely, vibration and noise on a steering wheel can be suppressed. A current controller in which a steady state gain of feedback control is a finite value is used so as to be capable of suppressing the vibration and noise. Further, according to the present invention, a smoothing filter is included in a current control system so that the quantization error is smoothed so that the torque ripple is suppressed.
    Type: Application
    Filed: July 15, 2005
    Publication date: January 19, 2006
    Inventors: Shuji Endo, Yuho Aoki, Kenji Mori, Toru Sakaguchi, Sakae Nejo, Hideaki Okazaki, Lilit Kovudhikulrungsri