Patents by Inventor LeeLing Tan
LeeLing Tan 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).
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Patent number: 7349174Abstract: A method of preventing a write operation to a disc in a disc drive during a shock event without the use of a separate shock sensor comprises steps of monitoring an actuator voice coil motor (VCM) control plant output signal, generating an actuator voice coil motor (VCM) plant model module output signal, comparing the VCM plant model module output signal to the VCM control plant module output signal to produce a difference signal, and triggering a write protect gate if the difference signal exceeds a predetermined threshold value.Type: GrantFiled: May 9, 2002Date of Patent: March 25, 2008Assignee: Seagate Technology LLCInventors: Qiang Bi, Xiong Liu, LeeLing Tan, Wen-Jun Cao, ChoonKiat Lim
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Patent number: 7330328Abstract: Method and apparatus for generating a random number, such as for use in a security protocol to control access to a data processing system. A processor generates the random number in relation to a back electromotive force (BEMF) value. The BEMF value is preferably obtained in response to application of current to a circuit. The circuit preferably comprises a coil and the application of current preferably induces a relatively small movement of the coil. The random number is preferably a multi-bit digital value, and each bit of the random number is determined in relation to whether the corresponding BEMF value is even or odd. The coil preferably comprises a coil of a voice coil motor (VCM) used to position a transducer adjacent a rotatable storage medium, and the random number is preferably generated while the medium is in a non-rotatable state.Type: GrantFiled: February 17, 2006Date of Patent: February 12, 2008Assignee: Seagate Technology LLCInventors: WenXiang Xie, LeeLing Tan, Xiong Liu, WeiLoon Ng
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Publication number: 20070195448Abstract: Method and apparatus for generating a random number, such as for use in a security protocol to control access to a data processing system. A processor generates the random number in relation to a back electromotive force (BEMF) value. The BEMF value is preferably obtained in response to application of current to a circuit. The circuit preferably comprises a coil and the application of current preferably induces a relatively small movement of the coil. The random number is preferably a multi-bit digital value, and each bit of the random number is determined in relation to whether the corresponding BEMF value is even or odd. The coil preferably comprises a coil of a voice coil motor (VCM) used to position a transducer adjacent a rotatable storage medium, and the random number is preferably generated while the medium is in a non-rotatable state.Type: ApplicationFiled: February 17, 2006Publication date: August 23, 2007Applicant: Seagate Technology LLCInventors: WenXiang Xie, LeeLing Tan, Xiong Liu, WeiLoon Ng
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Patent number: 6937427Abstract: An apparatus and method of measuring a back electromotive force (BEMF) voltage of a disc drive voice coil motor (VCM) is provided in which a temperature of the VCM is obtained. The BEMF voltage of the VCM is computed as a function of the temperature of the VCM.Type: GrantFiled: June 19, 2003Date of Patent: August 30, 2005Assignee: Seagate Technology LLCInventors: LeeLing Tan, Xiong Liu, ChoonKit Lim, MuiChong Chai
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Publication number: 20050034539Abstract: Method and apparatus for compensating variations in motor torque in a control system that employs a motor to accelerate a control object, such as a data transducing head in a data storage device. During acceleration of the control object, a plurality of distances successively traveled by the control object are measured, and the measured distances are combined to compensate for said variations in motor torque. Preferably, a constant control input is applied to accelerate the control object at a constant rate of acceleration less than a maximum rate of acceleration that can be obtained by the motor. A coarse adjustment routine is preferably applied to arrive at a first compensation value that compensates for said variations at a first resolution, after which a fine adjustment routine is performed using the first compensation value to arrive at the final compensation value at a second resolution greater than the first resolution.Type: ApplicationFiled: March 31, 2004Publication date: February 17, 2005Inventors: LeeLing Tan, MingZhong Ding, KianKeong Ooi, JianYi Wang
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Publication number: 20040257695Abstract: An apparatus and method of measuring a back electromotive force (BEMF) voltage of a disc drive voice coil motor (VCM) is provided in which a temperature of the VCM is obtained. The BEMF voltage of the VCM is computed as a function of the temperature of the VCM.Type: ApplicationFiled: June 19, 2003Publication date: December 23, 2004Inventors: LeeLing Tan, Xiong Liu, ChoonKit Lim, MuiChong Chai
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Publication number: 20040075934Abstract: A disc drive includes an information storage disc and an actuator assembly. A retraction voltage and a retraction time interval are calculated based on the location of a transducer over a surface of the information storage disc. The retraction voltage is applied for the retraction time interval such that the actuator assembly reaches the park position at a predetermined velocity. A brake time interval is calculated when the disc drive is operating in seek mode while power to the disc drive is interrupted. A brake is applied for the brake time interval to halt movement of the actuator assembly before the retraction voltage is applied. The values of retraction voltage, retraction time interval and brake time interval are continually updated in data tables. The values are retrieved when power to the disc drive is unexpectedly interrupted such that the actuator assembly reaches the park position at the predetermined velocity.Type: ApplicationFiled: June 25, 2003Publication date: April 22, 2004Inventors: LeeLing Tan, Xiong Liu, KianKeong Ooi, James LaiKein Chang, Jimmy TzeMing Pang, ChoonKiat Lim
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Method and apparatus for handling multiple resonance frequencies in disc drives using active damping
Patent number: 6690534Abstract: A method of handling multiple resonance frequencies in a disc drive includes monitoring a position error signal (PES) for an actuator arm, generating a plurality of feedforward compensation signals from the PES using a plurality of bandpass filters, and applying the compensation signals to a servo control signal. Each filter has a center frequency that is set to a problematic resonance frequency. The method may also include identifying the problematic frequencies by, for example, commanding a movement of the actuator arm, collecting data points for the PES that are associated with the movement, and performing a digital fourier transform of the data points to identify resonant frequencies. Other methods of identifying problematic frequencies include analyzing PES zero-crossing data, or using principal component analysis.Type: GrantFiled: April 5, 2001Date of Patent: February 10, 2004Assignee: Seagate Technology LLCInventors: MingZhong Ding, YangQuan Chen, LeeLing Tan, Wing Kong Chiang, KianKeong Ooi, BengWee Quak -
Patent number: 6687065Abstract: A disc drive includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The actuator assembly includes an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method for screening disc drives for resonant frequencies associated with the actuator arm includes the steps of following a track within the disc drive, and selectively boosting the servo control signal. The method further includes a step of monitoring a position error signal from a transducer attached to an actuator arm of a disc drive. The position error signal is monitored by filtering the position error signal using a bandpass filter. Boosting the servo control loop includes tuning the magnitude of the booster signal gain.Type: GrantFiled: February 7, 2001Date of Patent: February 3, 2004Assignee: Seagate Technology LLCInventors: LeeLing Tan, MingZhong Ding, WeeMeng Yio, KianKeong Ooi, KokHoe Chia
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Publication number: 20030103286Abstract: A method of preventing a write operation to a disc in a disc drive during a shock event without the use of a separate shock sensor comprises steps of monitoring an actuator voice coil motor (VCM) control plant output signal, generating an actuator voice coil motor (VCM) plant model module output signal, comparing the VCM plant model module output signal to the VCM control plant module output signal to produce a difference signal, and triggering a write protect gate if the difference signal exceeds a predetermined threshold value.Type: ApplicationFiled: May 9, 2002Publication date: June 5, 2003Applicant: Seagate Technology LLCInventors: Qiang Bi, Xiong Liu, LeeLing Tan, Wen-Jun Cao, ChoonKiat Lim
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Patent number: 6574067Abstract: A repetitive learning compensator for a servo system of a disc drive includes a memory buffer having a length N/m where N is the number of servo sectors in a track, m is a parsing factor greater than 1 and N/m is an integer. A down sampler supplies servo signals containing error signals to the repetitive learning compensator at a frequency of fs/m, where fs is a sampling frequency based on N and a fundamental frequency f0 of the spindle motor. An up sampler supplies filtered signals from the repetitive learning compensator to the actuator assembly at the sampling frequency fs. One aspect of the disclosure includes tuning the repetitive learning compensator with a phase advance represented by NPA and a cutoff frequency fc, where NPA and fc are selected as a pair to provide the greatest transfer function amplitude at the harmonic frequencies for the repetitive learning compensator.Type: GrantFiled: January 12, 2001Date of Patent: June 3, 2003Assignee: Seagate Technology LLCInventors: YangQuan Chen, MingZhong Ding, LinCheng Xiu, KianKeong Ooi, LeeLing Tan
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Patent number: 6437936Abstract: A method and apparatus for compensating for written-in repeatable runout in a disc drive is provided. Compensation values are determined through an iterative learning process in which parameters of the learning process such as learning gain, servo loop gain, etc. are functions of the iteration number. The learning process also employs a nominal double integrator model of an actuator of the disc storage system. The learning process is also a function of a zero-phase low-pass filter.Type: GrantFiled: January 21, 2000Date of Patent: August 20, 2002Assignee: Seagate Technology LLCInventors: YangQuan Chen, LeeLing Tan, KianKeong Ooi, Qiang Bi, KokHiang Cheong
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Method and apparatus for handling multiple resonance frequencies in disc drives using active damping
Publication number: 20020041472Abstract: A method of handling multiple resonance frequencies in a disc drive includes monitoring a position error signal (PES) for an actuator arm, generating a plurality of feedforward compensation signals from the PES using a plurality of bandpass filters, and applying the compensation signals to a servo control signal. Each filter has a center frequency that is set to a problematic resonance frequency. The method may also include identifying the problematic frequencies by, for example, commanding a movement of the actuator arm, collecting data points for the PES that are associated with the movement, and performing a digital fourier transform of the data points to identify resonant frequencies. Other methods of identifying problematic frequencies include analyzing PES zero-crossing data, or using principal component analysis.Type: ApplicationFiled: April 5, 2001Publication date: April 11, 2002Inventors: MingZhong Ding, YangQuan Chen, LeeLing Tan, Wing Kong Chiang, KianKeong Ooi, BengWee Quak -
Publication number: 20010043427Abstract: A repetitive learning compensator for a servo system of a disc drive includes a memory buffer having a length N/m where N is the number of servo sectors in a track, m is a parsing factor greater than 1 and N/m is an integer. A down sampler supplies servo signals containing error signals to the repetitive learning compensator at a frequency of fs/m, where fs is a sampling frequency based on N and a fundamental frequency f0 of the spindle motor. An up sampler supplies filtered signals from the repetitive learning compensator to the actuator assembly at the sampling frequency fs. One aspect of the disclosure includes tuning the repetitive learning compensator with a phase advance represented by NPA and a cutoff frequency fc, where NPA and fc are selected as a pair to provide the greatest transfer function amplitude at the harmonic frequencies for the repetitive learning compensator.Type: ApplicationFiled: January 12, 2001Publication date: November 22, 2001Inventors: YangQuan Chen, MingZhong Ding, LinCheng Xiu, KianKeong Ooi, LeeLing Tan
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Efficient sensorless rotational vibration and shock compensator for hard disk drives with higher TPI
Publication number: 20010036026Abstract: A low cost sensorless technique for attenuating an actuating force experienced by the actuator arm assembly due to an external vibration and shock during a track following operation includes, in one example embodiment, measuring an applied signal and a position error signal during the track following operation within a sampling time. Then, the method includes the step of computing an acceleration signal from the measured position error signal. Further, the method includes comparing the acceleration signal with the applied signal to obtain a correction signal. Then, the force experienced by the actuator arm due to the external vibration and shock is attenuated by filtering the correction signal using one or more low-pass frequency filters.Type: ApplicationFiled: February 23, 2001Publication date: November 1, 2001Applicant: Seagate Technology LLCInventors: YangQuan Chen, MingZhong Ding, LeeLing Tan, KianKeong Ooi -
Publication number: 20010028519Abstract: A disc drive includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The actuator assembly includes an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method for screening disc drives for resonant frequencies associated with the actuator arm includes the steps of following a track within the disc drive, and selectively boosting the servo control signal. The method further includes a step of monitoring a position error signal from a transducer attached to an actuator arm of a disc drive. The position error signal is monitored by filtering the position error signal using a bandpass filter. Boosting the servo control loop includes tuning the magnitude of the booster signal gain.Type: ApplicationFiled: February 7, 2001Publication date: October 11, 2001Inventors: LeeLing Tan, MingZhong Ding, WeeMeng Yio, KianKeong Ooi, KokHoe Chia