System and method for using parabolic models to improve position estimates from a global positioning system

• US 5,629,855 A
• Filed: 06/01/1995
• Issued: 05/13/1997
• Est. Priority Date: 02/05/1990
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Friedrich, Douglas W., Gudat, Adam J., Kyrtsos, Christos T., Stafford, Darrell E., Christensen, Dana A., Sennott, James W.
• Primary Examiner(s): PARK, COLLIN
• Application Number:
  US08/457,960
• Time in Patent Office: 712 Days
• Field of Search: 364/449, 364/460, 340/988, 342/352, 342/357, 342/450, 342/457
• US Class Current: 701/300
• CPC Class Codes: B60K 31/0008 including means for detecting potential obstacles in vehicle path
• CPC Class Codes: B60K 31/04 and means for comparing one electrical quantity, e.g. voltage, pulse, waveform, flux, or the like, with another quantity of a like kind, which comparison means is involved in the development of an electrical signal which is fed into the controlling means
• CPC Class Codes: B62D 1/28 non-mechanical , e.g. following a line or other known markers
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/52 Determining velocity
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G05D 1/0011 associated with a remote control arrangement
• CPC Class Codes: G05D 1/024 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals
• CPC Class Codes: G05D 1/0268 using internal positioning means
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: G05D 1/0278 : using satellite positioning signals, e.g. GPS
• CPC Class Codes: G05D 1/0297 : by controlling means in a control room
• CPC Class Codes: G08G 1/202 : Dispatching vehicles on the basis of a location, e.g. taxi dispatching

Abstract

Systems and methods allow for the accurate determination of the terrestrial position of an autonomous vehicle in real time. A first position estimate of the vehicle 102 is derived from satellites of a global positioning system and/or a pseudolite(s). The pseudolite(s) may be used exclusively when the satellites are not in the view of the vehicle. A second position estimate is derived from an inertial reference unit and/or a vehicle odometer. The first and second position estimates are combined and filtered using novel techniques to derive a more accurate third position estimate of the vehicle'"'"'s position. Accordingly, accurate autonomous navigation of the vehicle can be effectuated using the third position estimate.

Claims

1. A system for improving the accuracy of a position estimate provided by a global positioning system based on pseudoranges derived from the global positioning system, the system comprising:

first means for determining a plurality of pseudoranges for each of a plurality of satellites;

in the global positioning system, said plurality of pseudoranges determined for each corresponding;

satellite at consecutive times over a time period, wherein each pseudorange represents a distance between a reference antenna and a corresponding satellite in view of said reference antenna at a corresponding time;

second means, responsive to said first means, for constructing a parabolic model for each satellite from said corresponding plurality of pseudoranges;

third means, responsive to said first means and said second means, for computing a parabolic bias for each satellite from an extrapolated pseudorange determined from said parabolic;

model and a future pseudorange derived after the time period; and

fourth means, responsive to said third means, for using said parabolic bias for each satellite to improve the accuracy of the position estimates.

2. The system of claim 1, wherein said second means comprises means for constructing said parabolic model for each satellite from said corresponding plurality of pseudoranges using a statistical R squared value of 0.98 or greater.

3. A method for using parabolic models to improve an accuracy of a position estimate based on actual pseudoranges derived from satellites of a global positioning system, the method comprising the steps of:

determining a plurality of actual pseudoranges corresponding to each of a plurality of satellites in view of a reference antenna;

constructing, for each satellite, a parabolic model from said corresponding plurality of actual pseudoranges;

extrapolating an estimated pseudorange for each satellite at a future time from said corresponding parabolic model;

computing a parabolic bias for each satellite based on a corresponding actual pseudorange determined at said future time and a corresponding estimated pseudorange; and

using said parabolic bias from each satellite to improve the accuracy of the position estimate.

4. A system for improving the accuracy of a position estimate based on pseudoranges derived from a global positioning system, the system comprising:

first means for determining a plurality of reference pseudoranges corresponding to each satellite in view of a reference antenna at consecutive times over a time period, said plurality of reference pseudoranges each representing a distance between said reference antenna and a corresponding satellite over said time period;

second means, responsive to said first means, for constructing a parabolic model for each satellite based on said corresponding plurality of reference pseudoranges; and

third means, responsive to said first means and said second means, for computing a first spatial bias for each satellite, said spatial bias being a difference between an extrapolated pseudorange determined from said parabolic model and a future pseudorange derived after said the time period;

fourth means, responsive to said first means, for computing an estimated position of said reference antenna using said plurality of reference pseudoranges;

fifth means, responsive to said second means, for comparing said estimated position with a known position of said reference antenna to derive a second spatial bias; and

sixth means for determining a position estimate of a user, for receiving said first and second spatial biases, and for using said first and second spatial biases to improve said terrestrial position estimates.