Patents by Inventor Liwen L. Dai

Liwen L. Dai 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: 10393882
    Abstract: Example methods disclosed herein include accessing carrier phase measurements and code measurements obtained for a plurality of satellite signals of a global navigation satellite system. Disclosed example methods also include determining an initial set of floating-point ambiguities based on the measurements, the initial set of floating-point ambiguities including inter-frequency bias (IFB). Disclosed example methods further include performing a least squares search process based on the initial set of floating-point ambiguities to determine a set of integer ambiguities and an estimate of the IFB. In some examples, an additional (e.g., wide-lane) filter is used to realize a combination of carrier phase and code IFB. In some examples, IFB estimation is further realized by determining a median of IFB estimates over a window time. In some examples, the resulting IFB estimate and the set of integer ambiguities are used to estimate a position of a receiver, determine a satellite correction signal, etc.
    Type: Grant
    Filed: September 26, 2016
    Date of Patent: August 27, 2019
    Assignee: Deere & Company
    Inventors: Liwen L. Dai, Yujie Zhang
  • Patent number: 10386496
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines narrow-lane navigation solutions for the plurality of reference receivers. The system also determines, in accordance with the narrow-lane navigation solutions, at a first update rate, an orbit correction for each satellite of a plurality of satellites; at a second update rate, a clock correction for each such satellite; and at a third update rate that is faster than the second update rate, an update to the clock correction for each such satellite. Further, the system generates navigation satellite corrections for each such satellite, including the orbit correction updated at the first update rate, and the clock correction that is updated at the third update rate.
    Type: Grant
    Filed: March 2, 2017
    Date of Patent: August 20, 2019
    Assignee: DEERE & COMPANY
    Inventors: Liwen L. Dai, Sonia Kuntz, Yiqun Chen, Yujie Zhang
  • Patent number: 10338232
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines wide-lane navigation solutions for the plurality of reference receivers. The system also determines clusters of single-difference (SD) wide-lane ambiguity values, each cluster comprising pairs of SD wide-lane floating ambiguities for respective pairs of satellites. A satellite wide-lane bias value for each satellite of a plurality of satellites is initially determined in accordance with fractional portions of the SD wide-lane floating ambiguities in the clusters, and then periodically updated by applying SD wide-lane integer constraints in a Kalman filter.
    Type: Grant
    Filed: March 2, 2017
    Date of Patent: July 2, 2019
    Assignee: Deere & Company
    Inventors: Yujie Zhang, Liwen L. Dai, Yiqun Chen
  • Patent number: 10191157
    Abstract: A wide-lane ambiguity and a respective satellite wide-lane bias are determined for the collected phase measurements for each satellite for assistance in narrow-lane ambiguity resolution. Satellite correction data is determined for each satellite in an orbit solution based on the collected raw phase and code measurements and determined orbital narrow-lane ambiguity and respective orbital satellite narrow-lane bias. A slow satellite clock correction is determined based on the satellite orbital correction data, the collected raw phase and code measurements, and clock narrow-lane ambiguity and respective satellite narrow-lane bias.
    Type: Grant
    Filed: September 6, 2016
    Date of Patent: January 29, 2019
    Assignee: DEERE & COMPANY
    Inventors: Liwen L. Dai, Sonia U. Kuntz, Yujie Zhang, Yiqun Chen
  • Patent number: 9846241
    Abstract: In a system for navigating a moving object according to signals received from satellites, a moving object receives mobile base data from a mobile base station, the received mobile base data including satellite measurement data of the mobile base station, the satellite measurement data of the mobile base station including code measurements and carrier phase measurements for the plurality of satellites, and position-related information of the mobile base station. In accordance with the satellite navigation data for the moving object and the received mobile base data, the moving object performing a real-time kinematic (RTK) computation process to resolve carrier phase ambiguities and determine a relative position of the moving object relative to the mobile base station. A signal reporting information corresponding to the relative position is sent via a transmitter of the moving object.
    Type: Grant
    Filed: March 16, 2015
    Date of Patent: December 19, 2017
    Assignee: DEERE & COMPANY
    Inventors: Liwen L. Dai, Yunfeng Shao
  • Publication number: 20170299730
    Abstract: A receiver or method uses an offset vector to provide seamless switching between a real-time kinematic (RTK) mode and a precise positioning mode (e.g., precise point positioning, PPP) mode. An offset module or data processor is arranged to determine an offset between precise position and the RTK position estimate. Upon loss of the RTK signal, switching to a precise position mode based a last available RTK position (e.g., if the precise position mode is converged on a position solution with resolved ambiguities of the carrier phase), wherein the next precise position estimate is compensated by the offset or reference frame bias to avoid a jump or discontinuity in the next precise position estimate.
    Type: Application
    Filed: March 18, 2016
    Publication date: October 19, 2017
    Inventors: F. Adhika Pradipta Lie, Michael A. Zeitzew, Yunfeng Shao, Liwen L. Dai
  • Publication number: 20170299728
    Abstract: An offset module or navigation positioning estimator determines a reference frame bias between precise point positioning (PPP) reference frame and an RTK reference frame, where the PPP reference frame is associated with relative position estimates generated by the relative position estimator and where the RTK reference frame is associated RTK position estimates generated by the RTK position estimator. Upon loss of the RTK correction signal, the navigation positioning estimator or controller switches to a relative position mode based a last available RTK position. The relative position estimator determines an estimated relative position based on time-differenced phase measurements by the mobile receiver in the relative position mode. The relative position estimator or offset module offsets the estimated relative position in the relative position mode.
    Type: Application
    Filed: March 18, 2016
    Publication date: October 19, 2017
    Inventors: F. Adhika Pradipta Lie, Michael A. Zeitzew, Yunfeng Shao, Liwen L. Dai
  • Publication number: 20170299731
    Abstract: A system or method uses an offset vector to provide seamless switching between a real-time kinematic (RTK) mode and a precise positioning mode. A correction wireless device is adapted to receive, at the reference receiver, a precise signal encoded with precise correction data. A precise positioning estimator of the reference receiver is arranged to determine a precise position based on the measured carrier phase of the received satellite signals and the received precise correction data in a precise correction mode. At the reference receiver, an offset module can determine a base offset vector between the precise position and a reference RTK position for the reference receiver. At the reference receiver, a wireless communications device is capable of transmitting, via an RTK signal, RTK correction data.
    Type: Application
    Filed: March 18, 2016
    Publication date: October 19, 2017
    Inventors: F. Adhika Pradipta Lie, Michael A. Zeitzew, Yunfeng Shao, Liwen L. Dai
  • Publication number: 20170269225
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines wide-lane navigation solutions for the plurality of reference receivers. The system also determines clusters of single-difference (SD) wide-lane floating ambiguities. A satellite wide-lane bias value for each satellite of a plurality of satellites is initially determined in accordance with fractional portions of the SD wide-lane floating ambiguities in the clusters and over-range adjustment criteria. A set of navigation satellite corrections for each satellite, including the satellite wide-lane bias value for each satellite, is generated and transmitted to navigation receivers for use in determining locations of the navigation receivers.
    Type: Application
    Filed: March 2, 2017
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Yiqun Chen, Yujie Zhang
  • Publication number: 20170269227
    Abstract: Example methods disclosed herein include accessing carrier phase measurements and code measurements obtained for a plurality of satellite signals of a global navigation satellite system. Disclosed example methods also include determining an initial set of floating-point ambiguities based on the measurements, the initial set of floating-point ambiguities including inter-frequency bias (IFB). Disclosed example methods further include performing a least squares search process based on the initial set of floating-point ambiguities to determine a set of integer ambiguities and an estimate of the IFB. In some examples, an additional (e.g., wide-lane) filter is used to realize a combination of carrier phase and code IFB. In some examples, IFB estimation is further realized by determining a median of IFB estimates over a window time. In some examples, the resulting IFB estimate and the set of integer ambiguities are used to estimate a position of a receiver, determine a satellite correction signal, etc.
    Type: Application
    Filed: September 26, 2016
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Yujie Zhang
  • Publication number: 20170269226
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines narrow-lane navigation solutions for the plurality of reference receivers. The system also determines, in accordance with the narrow-lane navigation solutions, at a first update rate, an orbit correction for each satellite of a plurality of satellites; at a second update rate, a clock correction for each such satellite; and at a third update rate that is faster than the second update rate, an update to the clock correction for each such satellite. Further, the system generates navigation satellite corrections for each such satellite, including the orbit correction updated at the first update rate, and the clock correction that is updated at the third update rate.
    Type: Application
    Filed: March 2, 2017
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Sonia Kuntz, Yiqun Chen, Yujie Zhang
  • Publication number: 20170269222
    Abstract: A wide-lane ambiguity and a respective satellite wide-lane bias are determined for the collected phase measurements for each satellite for assistance in narrow-lane ambiguity resolution. Satellite correction data is determined for each satellite in an orbit solution based on the collected raw phase and code measurements and determined orbital narrow-lane ambiguity and respective orbital satellite narrow-lane bias. A slow satellite clock correction is determined based on the satellite orbital correction data, the collected raw phase and code measurements, and clock narrow-lane ambiguity and respective satellite narrow-lane bias.
    Type: Application
    Filed: September 6, 2016
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Sonia U. Kuntz, Yujie Zhang, Yiqun Chen
  • Publication number: 20170269231
    Abstract: A real-time kinematic (RTK) filter uses the backup data to estimate a relative position vector between the mobile receiver at the first measurement time and the mobile receiver at the second measurement time and to provide recovery data associated with a satellite-differenced double-difference estimation for the mobile receiver between the first measurement time and the second measurement time. A navigation positioning estimator can apply the relative position vector, the backup data, the recovery data from the RTK filter, and received correction data with precise clock and orbit information on the satellite signals, as inputs, constraints, or both for convergence or resolution of wide-lane and narrow-lane ambiguities, and determination of a precise position, in accordance with a precise positioning algorithm.
    Type: Application
    Filed: October 7, 2016
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Min Wang, Soon Sik Hwang
  • Publication number: 20170269224
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines narrow-lane navigation solutions for the plurality of reference receivers. The system also determines clusters of single-difference (SD) narrow-lane floating ambiguities, each cluster comprising pairs of SD narrow-lane floating ambiguities for respective pairs of satellites. A satellite narrow-lane bias value for each satellite of a plurality of satellites is initially determined in accordance with fractional portions of the SD narrow-lane floating ambiguities in the clusters, and then periodically updated by a Kalman filter.
    Type: Application
    Filed: March 2, 2017
    Publication date: September 21, 2017
    Inventors: Yujie Zhang, Liwen L. Dai, Yiqun Chen
  • Publication number: 20170269216
    Abstract: A relative positioning module applies a real-time kinematic (RTK) algorithm to provide relative position vector between reference receiver and rover receiver and to provide recovery data. At the rover, the precise positioning module applies the relative position vector, the aiding data, recovery data, and correction data as inputs, constraints, or both for convergence of one or more predictive filters on wide-lane and narrow-lane ambiguities (e.g., in accordance with a precise positioning algorithm). At the rover, the precise positioning module or the navigation positioning estimator estimates a precise position of the rover based on the converged or fixed narrow-lane ambiguities and wide-lane ambiguities.
    Type: Application
    Filed: October 7, 2016
    Publication date: September 21, 2017
    Inventors: Liwen L. Dai, Soon Sik Hwang
  • Publication number: 20170269223
    Abstract: A satellite corrections generation system receives reference receiver measurement information from a plurality of reference receivers at established locations. In accordance with the received reference receiver measurement information, and established locations of the reference receivers, the system determines wide-lane navigation solutions for the plurality of reference receivers. The system also determines clusters of single-difference (SD) wide-lane ambiguity values, each cluster comprising pairs of SD wide-lane floating ambiguities for respective pairs of satellites. A satellite wide-lane bias value for each satellite of a plurality of satellites is initially determined in accordance with fractional portions of the SD wide-lane floating ambiguities in the clusters, and then periodically updated by applying SD wide-lane integer constraints in a Kalman filter.
    Type: Application
    Filed: March 2, 2017
    Publication date: September 21, 2017
    Inventors: Yujie Zhang, Liwen L. Dai, Yiqun Chen
  • Publication number: 20170212247
    Abstract: A moveable object determines a preliminary position for the moveable object using received satellite navigation signals and satellite orbit correction information and satellite clock correction information. A position correction is determined by identifying which cell, of a predefined set of geographical cells, corresponds to the determined preliminary position, and obtaining from a database, pre-computed tectonic terrestrial plate position information for the identified cell. Based on the information for the identified cell, a tectonic terrestrial plate, corresponding to the determined preliminary position of the moveable object is identified.
    Type: Application
    Filed: October 4, 2016
    Publication date: July 27, 2017
    Inventors: Yiqun Chen, Liwen L. Dai
  • Publication number: 20160377736
    Abstract: A tracking module processes the determined correlations to track a carrier of the received composite signal for estimation of a change in phase over a time period between a receiver antenna and one or more satellite transmitters that transmit the received signal as the receiver changes position with respect to an initial position during the time period. A relative position estimator estimates the relative position of the navigation receiver with respect to an initial position over the time period time by time-differencing of the phase measurements of the one or more tracked carrier signals. Bias estimators can estimate or compensate for errors in initial position and temporal changes in receiver clock and tropospheric delay.
    Type: Application
    Filed: September 17, 2015
    Publication date: December 29, 2016
    Inventors: Michael A. Zeitzew, Liwen L. Dai, Min Wang, David S. Chiu
  • Publication number: 20150185331
    Abstract: In a system for navigating a moving object according to signals received from satellites, a moving object receives mobile base data from a mobile base station, the received mobile base data including satellite measurement data of the mobile base station, the satellite measurement data of the mobile base station including code measurements and carrier phase measurements for the plurality of satellites, and position-related information of the mobile base station. In accordance with the satellite navigation data for the moving object and the received mobile base data, the moving object performing a real-time kinematic (RTK) computation process to resolve carrier phase ambiguities and determine a relative position of the moving object relative to the mobile base station. A signal reporting information corresponding to the relative position is sent via a transmitter of the moving object.
    Type: Application
    Filed: March 16, 2015
    Publication date: July 2, 2015
    Inventors: Liwen L. Dai, Yunfeng Shao
  • Patent number: 8983685
    Abstract: In a system and method for navigating a moving object according to signals from satellite, a moving object receives satellite navigation signals from a number of satellites. The moving object also receives moving base data from a moving base. The received moving base data includes satellite measurement data of the moving base. At the moving object a relative position vector of the moving object relative to the moving base is determined, based on the received moving base data and the received satellite navigation signals. The moving object sends a signal reporting information corresponding to the relative position vector.
    Type: Grant
    Filed: May 25, 2011
    Date of Patent: March 17, 2015
    Assignee: Deere & Company
    Inventors: Liwen L. Dai, Yunfeng Shao