Aeronautics and astronautics – Aircraft control – Automatic
Reexamination Certificate
1999-11-01
2001-08-14
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft control
Automatic
C244S194000, C244S195000, C701S006000
Reexamination Certificate
active
06273370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to aircraft control systems, and more particularly to using accelerometers to generate angle-of-attack and sideslip angle to provide local flow corrections to probes or vanes within an angle-of-attack and stall warning system. Still more particularly, the present invention relates to a method and system for providing an ability to reconfigure an aircraft control system after a sensor failure within the angle-of-attack and stall warning system.
2. Description of the Related Art
It has long been recognized that signals representative of aircraft angle-of-attack and aircraft sideslip angle and their respective time derivatives are useful for aircraft flight control augmentation purposes. In the past, and at present, signals from angle-of-attack and sideslip aerodynamic probes and sensors cannot be utilized as part of control feedback computations because of measurement corruption inherent in measurement of local aerodynamic flow fields around the aircraft surfaces where these probes are positioned. For example, a typical angle-of-attack probe at the airfoil surface of an aircraft is, under various circumstances, subject to severe variations and rapid perturbations of the airflow. As a result, the signal from the probe is masked by interfering or noise signals. While it is possible to process the noisy signal by means of filtering techniques to extract the useful information, the magnitude of filtering required reduces bandwidth to an unacceptably low level and so increases the response time that use of the signal for control purposes is seriously affected.
Based on the foregoing, it can be appreciated that a need exists for an improved method and system wherein the use of conventional air data probes used on modem high performance aircraft can be minimized or eliminated while still providing signals representative of aircraft angle-of-attack and sideslip angle. The subject invention herein solves all of these problems in a new and unique manner that has not been part of the art previously.
SUMMARY OF THE INVENTION
A method and system is disclosed for using inertial sensors in an Inertial Navigation System (INS) to obtain analytic estimates of angle-of-attack (
&agr;
) and sideslip angle (
&bgr;
). The inertial sensors consist of one or more accelerometers which produce the estimated signals for angle-of-attack (
&agr;
) and sideslip angle (
&bgr;
). The estimated signals may be combined with conventional probes to improve the frequency content of conventional probes using a complementary filter or aKalman filter. The estimated signals are also improved in other (perpendicular) axes by generating correction curves, for example correcting the angle-of-attack (
&agr;
) signal by removing sideslip angle (
&bgr;
) effects. Three methods are shown for obtaining alpha and beta estimates from INS information and are programmed into a nonlinear simulation of a relaxed stability aircraft requiring a high level of artificial stability augmentation in its flight control system. Simulation results from the nonlinear simulation for each of the three methods were compared with the results obtained when conventional probes were used to obtain direct measurements of
&agr;
and
&bgr;
. Based on these comparisons, a method for determining
&agr;
and
&bgr;
analytically which estimates the turbulence level in each axis is combined with one of the three methods to provide derived inertial values for providing control system feedback to an aircraft.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.
REFERENCES:
patent: 3814912 (1974-06-01), Manke et al.
patent: 3924262 (1975-12-01), Melancon
patent: 3970829 (1976-07-01), Melvin
patent: 4769759 (1988-09-01), McGough
patent: 4893245 (1990-01-01), Zweifel
patent: 5988562 (1999-11-01), Linick
Best Christian M.
Jordan Charles T.
Lockheed Martin Corporation
Schruhl Robert A.
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