Vehicle position determination system and method

• US 5,438,517 A
• Filed: 02/18/1993
• Issued: 08/01/1995
• Est. Priority Date: 02/05/1990
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Gudat, Adam J., Kyrtsos, Christos T., Stafford, Darrell E., Christensen, Dana A., Sennott, James W., Friedrich, Douglas W.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/019,441
• Time in Patent Office: 894 Days
• Field of Search: 364/443, 364/449, 364/453, 364/455, 364/459, 342/357, 342/358, 342/450, 342/451, 73/178 R
• US Class Current: 701/213
• 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: G08G 1/20 Monitoring the location of vehicles belonging to a group, e.g. fleet of vehicles, countable or determined number of vehicles

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 method for improving the accuracy of terrestrial position estimates of a user antenna located on a vehicle based on pseudoranges derived from satellites of a global position system, the method comprising the steps of:

(1) obtaining a known position of a reference antenna;

(2) receiving electromagnetic signals at said reference antenna from a constellation of satellites and responsively determining respective reference antenna pseudoranges;

(3) determining an estimated position of said reference antenna using said reference antenna pseudoranges;

(4) comparing said estimated position of said reference antenna with said known position of said reference antenna to derive a spatial bias;

(5) transmitting said reference antenna pseudoranges and said spatial bias to the vehicle;

(6) receiving electromagnetic signals at the user antenna on the vehicle, receiving said reference antenna pseudoranges and said spatial bias at the vehicle and responsively determining a position estimate of the vehicle as a function of said spatial bias and said electromagnetic signals;

(7) at the vehicle, determining another estimate of the position of the reference antenna as a function of said reference antenna pseudoranges;

(8) determining an offset as a function of said another estimate of the position of said reference antenna and said known position of said reference antenna; and

(9) updating said position estimate of the vehicle as a function of said offset; and

(10) repeating steps (7)-(9) until said offset is less than a predetermined threshold.

2. A method for improvingthe accuracy of terrestrial position estimates of a user antenna located at a vehicle, the method comprising the steps of:

(1) obtaining a known position of a reference antenna;

(2) receiving electromagnetic signals at said reference antenna from a constellation of satellites and responsively determining respective reference antenna pseudoranges;

(3) computing an estimated position of said reference antenna using said reference antenna pseudoranges;

(4) comparing said estimated position of said reference antenna with said known position of said reference antenna to derive a base residuals bias;

(5) transmitting said base residuals bias and said reference antenna pseudoranges to the vehicle;

(6) receiving electromagnetic signals at the user antenna, receiving said base residuals bias and said reference antenna pseudoranges at the vehicle, and computing future user pseudoranges as a function of said base residuals bias;

(7) determining a position estimate of the vehicle as a function of said future user pseudoranges;

(8) at the vehicle, determining another estimate of the position of the reference antenna as a function of the reference antenna pseudoranges;

(9) determining an offset as a function of said another estimate of the position of the reference antenna and said known position of said reference antenna;

(10) updating said position estimate of the vehicle as a function of said offset; and

(11) repeating steps (8)-(10) until said offset is less than a predetermined threshold.

3. A method for estimating the terrestrial position of a vehicle (102), comprising:

(1) receiving electromagnetic signals at a base station from a constellation of satellites and responsively determining a base spatial bias, a base clock bias, and base pseudoranges;

(2) transmitting said base spatial bias, said base clock bias, and said base pseudoranges to the vehicle;

(3) receiving electromagnetic signals at the vehicle from said constellation of satellites and responsively determining vehicle pseudoranges;

(4) receiving said base spatial bias and said base clock bias at the vehicle and determining a position estimate of the vehicle as a function of said base spatial bias, said base clock bias, and said vehicle pseudoranges;

(5) determining an estimate of the position of said base station at the vehicle as a function of said base pseudoranges;

(6) determining an offset as a function of said estimate of the position of said base station and a known position of said base station;

(7) updating said position estimate of the vehicle as a function of said offset; and

(8) repeating steps (5)-(7) until said offset is less than a predetermined threshold.