Communications: electrical – Aircraft alarm or indicating systems
Patent
1999-02-24
2000-09-05
Wu, Daniel J.
Communications: electrical
Aircraft alarm or indicating systems
34235701, 342457, G08B 2100
Patent
active
061149756
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FR 97/0154 dated Sep. 2, 1997.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to assistance with navigation or with piloting, with a view to directing a mobile towards a target which can move or more generally towards a target whose exact position is not known a priori. This navigation or this piloting is referred to hereinafter as "relative navigation"; the mobile will be referred to as the "hunter", the objective of the hunter being the target.
The applications envisaged here are in particular the following: leader, (for helicopters or terrestrial vehicles) although the position of the beacon is not known a priori, although the position of the beacon itself is not known.
The applications envisaged are applications in which the accuracy of positioning is a predominant parameter.
2. Discussion of the Background
The systems proposed hitherto for these applications are not sufficiently accurate or demand calculating powers which are too large to allow real-time applications with sufficient accuracy. For the case of aircraft landing on an aircraft carrier, it is understood that the calculation must be performed in real time with great accuracy and a high rate of information refresh.
The following procedure could be used: a satellite-based positioning receiver placed on the target sends its position to the hunter by radio. Another receiver on the hunter calculates its position and performs a subtraction between the two calculated positions so as to determine the components of a vector joining the mobile to the target. The pilot of the mobile uses these components as an aid for steering towards the target.
This solution is not satisfactory owing to the uncertainties which affect the position information calculated by the receivers. It is recalled that the positions are calculated with a certainty tied to the clock fluctuations of the signals transmitted by the satellites.
SUMMARY OF THE INVENTION
The invention proposes a solution for facilitating, at the least cost, relative navigation of a hunter towards a target, this solution making it possible in particular to provide a fast rate of the most exact possible relative navigation information with means which are limited in terms of necessary computing power.
The invention relies on the sending by the target to the hunter of raw measurements of pseudo-distances between the receiver of the target and each of the satellites which this receiver can validly use, together with the identification of the satellites. The receiver of the target does not send any result of calculation of its own position in relation to a terrestrial reference marker. The hunter makes its own measurements of pseudo-distances then processes directly by calculating the differences of pseudo-distances so as to calculate the components of a relative-position vector joining the hunter to the target in relation to a terrestrial reference marker.
Likewise, the target can send raw measurements of relative pseudo-velocities between the target and each of the satellites, without sending any result of calculation of velocity in relation to a terrestrial reference marker. The hunter receives these measurements, calculates differences between its own measurements of pseudo-velocities and those which it receives from the target and performs a calculation directly on these differences which culminates in the components of a vector of relative velocity between the mobile and the target in relation to a terrestrial reference marker.
The terrestrial reference marker will in practice be the local geographical reference marker with three axes: longitude axis, latitude axis, and altitude axis.
The calculations of relative position and velocity will be made in this local reference marker, but the relative-navigation information may be displayed, after a change of coordinates, in relation to a reference marker tied to the target, on condition that the target transmits its attitude to the hunter.
More precisely, the invention proposes a process f
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patent: 5311194 (1994-05-01), Brown
patent: 5331329 (1994-07-01), Volkov et al.
patent: 5587715 (1996-12-01), Lewis
patent: 5831576 (1998-11-01), Sheynblat
patent: 5949375 (1999-09-01), Ishiguro et al.
Sextant Avionique
Tweel , Jr. John
Wu Daniel J.
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