US 2011/0257882 A1Published application

Road map feedback server for tightly coupled gps and dead reckoning vehicle navigation

OwnerPAUL W. McBURNEY, Eric Hirschinventors

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Abstract

Road map feedback is used in a tightly coupled GPS and dead-reckoning system that collects wheel speed transducer data over a vehicle's CANbus network to compute vehicle range and direction. Road segment information provided by a network server provides a database of constraints that are templated on to current navigation solutions so that corrective feedback can be derived. The dead-reckoning bridges over gaps in navigation solutions that would otherwise occur when GPS signal transmission is lost in tunnels, parking garages, and other common situations. The road map fitting controls drift that would otherwise accumulate during long periods of dead reckoning only operation.

Claims10

Dependent claims

An improved vehicle navigation system, comprising:

a GPS receiver carried aboard a vehicle and subject to interruptions of signal transmissions from orbiting navigation satellites;
a DR-computer coupled to the GPS receiver and providing for range and heading information computed by dead reckoning during periods of said signal interruptions, and such that vehicle navigation solutions and assistance are continually available through a screen display to a user;
wheel-tick sensors coupled to the DR-computer and providing for rotational data related to the turning of individual wheels that carry said vehicle;
a road map database having road segment information that can be matched to said vehicle navigation solutions;
the improvement characterized by:
a network server for providing road segment information from the road map database for a limited local area on request by a motor vehicle to a look ahead database carried by the vehicle;
an estimate of the true radii of said individual wheels;
wherein, estimates of the true radii of said individual wheels are combined with said rotational data from the wheel-tick sensors to generate change in range, delta-range, and change in heading, delta-heading, information related to movements of said vehicle;
wherein, said delta-range and delta-heading information are propagated by the DR-computer from absolute position information periodically obtained from the GPS receiver, with the dead reckoning results alone sometimes being output as vehicle navigation solutions;
wherein, road segment information stored in said look ahead database is matched to said vehicle navigation solutions and is used to correct drifts in dead reckoning propagation during periods of GPS outages;
wherein, a combined GPS and dead reckoning position is corrected for drift each time a snapping error exceeds a predetermined value;
wherein, said vehicle navigation solutions and assistance are continually made available through a screen display to a user and that are derived solely from the GPS receiver, solely by the DR-computer, or from a mix provided by the GPS receiver and the DR-computer that have been periodically corrected for drift away from a road segment by feedback correction;
and
wherein, a map matching function is based on server provided map line segments.

11 more elements

A tightly coupled GPS, dead reckoning, and map matching navigation software application program for execution as a GPS application in a host computer, and connected to receive measurements from a GPS measurements platform (MP) aboard a vehicle with wheels, comprising:

an input process for collecting time, fix trigger, Doppler, and pseudorange reports from a GPS measurements platform (MP) device mounted aboard a vehicle with wheels;
a GPS-time to host computer time offset calculation process for aligning otherwise asynchronous data generated by said vehicle to GPS time;
a least squares snapshot estimator for position (P), velocity (V), calibration parameters for the wheel radii and ratio (B), delta-heading and delta-range (D), and time based on each new position fix and GPS system time;
a Kalman Filter configured for position (P), velocity (V), calibration parameters for the wheel radii and ratio (B), delta-heading and delta-range (D), and time, and for processing dead reckoning delta-range, delta-heading, mixed modes, and propagation;
a continuous mode selection process for operating in a GPS only mode, dead reckoning only mode, or a mixed mode of both GPS and dead reckoning, depending on an availability of GPS solutions and wheel data calibrations;
a new fix computation process for computing hardware preposition data and adjusting a GPS millisecond timer connected to the time offset calculation process;
a buffer process for collecting time-stamped CANbus data related to wheel turning ticks measured by a vehicle's wheel transducers;
a dead reckoning calibration Kalman filter for processing AL and AR calibration parameters for delta-heading/tick difference for left and right wheels, and BL, and BR calibration parameters for delta-range/tick for left and right wheels, and a heading-offset calibration parameter that translates a sum delta-heading to a known heading reference;
a dead reckoning data process for converting data from the buffer process into delta-range, delta-heading, and delta-heading sum information for subsequent processing by the Kalman Filter, and including a dead reckoning error model;
a feedback position data process in which a combined GPS and dead reckoning position is corrected for drift each time a snapping error exceeds a predetermined value;
a road segment matching process for correcting drifts in dead reckoning propagation during periods of GPS outages with road segment information downloaded periodically from a network server to a local look ahead database;
and
an applications programming interface (API) for outputting new navigation fixes.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/760,831Filed 15 Apr 2010
Published: 20 Oct 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01C 21/30
With correlation of data from several navigational instruments: map- or contour-matching
G01S 19/40
The satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting…:…
G01S 19/47
By combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement: the supplementary…
G01C
Measuring distances, levels or bearings

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