Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-07-12
2001-05-29
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S210000, C342S357490
Reexamination Certificate
active
06240368
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to a positioning system for a motor vehicle having a satellite receiver. It is already known from European Published Patent Application No. 496 538 A2 that not only the position of a vehicle but also its direction of travel can be calculated with the help of the satellite receiver. The direction of travel is determined by calculating the difference between two position determinations. This method functions satisfactorily only when the GPS positions are measured over great distances, because each individual position is subject to considerable error (in civilian use: approximately 100 m).
Therefore, it is impossible to determine the direction of travel in real time with this method. Furthermore, this method assumes little or no coupling sensor error during the GPS measurement; however, that is only rarely the case in practice.
SUMMARY OF THE INVENTION
The present invention has the advantage that the determination of the direction of travel with the help of the satellite receiver is not affected by the positioning accuracy, and the direction of travel is determined almost in real time. It is especially advantageous that first an angular range of the direction of travel is assumed for the direction of travel of the vehicle; this range contains the direction of travel with a predetermined tolerance. The actual direction of travel and the location of the vehicle are advantageously determined with a high accuracy with the help of the angular range of the direction of travel and prioritization of a main path.
It is especially advantageous that the direction of travel of the motor vehicle is determined by the Doppler method from the received satellite frequencies (carrier wave) while the vehicle is traveling. With conventional GPS receivers, a velocity vector of the vehicle in the direction of travel can be determined with an accuracy of 0.1 m/s to 0.2 m/s with the help of the Doppler effect. However, the accuracy drops due to the artificial manipulation of the satellite signals by the GPS operator. The higher the vehicle velocity, the more accurately the velocity vector can be determined. To obtain the direction of the velocity vector with sufficient accuracy, the vehicle velocity must be considerably above this absolute value, because at a higher velocity, the manipulations of the carrier frequency (selective availability) performed by the GPS operator (U.S. Department of Defense) can also be disregarded. Experiments have shown that a GPS receiver yields usable results starting from speeds as low as approx. 15 km/h.
Since the determination of direction with the help of the GPS receiver can be regarded as an absolute measurement of the direction of travel, a direction sensor such as a rotational rate sensor or a gyro sensor may be calibrated to advantage. If there is an interruption in reception, the calibrated direction sensor can then advantageously detect the absolute direction of travel of the motor vehicle.
It is also advantageous that the computer of the positioning system determines a main path and optionally secondary paths with the help of the angular range of direction for the position determination. Weighting the main path and the secondary paths yields a new main path whose direction at the location of the presumed position best agrees with that of the angular range of direction. Due to the weighting of the individual paths, the determination of the direction of travel and the vehicle position is very reliable, because the vehicle can travel on only one of the paths (roads) detected.
It is also advantageous that with unclear determinations, in particular with a narrow network of roads with parallel paths, the previous main path is retained. This avoids making the driver of the motor vehicle uncertain about the actual direction of travel due to repeated changes between a main path and a secondary path.
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Kenyon & Kenyon
Robert & Bosch GmbH
Zanelli Michael J.
LandOfFree
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