The United States of America As Represented by the Administrator of the

United States of America As Represented by the Administrator of Nasa

John J Burken

Frank W Burcham, Jr

Nhan Thanh Nguyen

Nilesh Vijay Kulkarni

Kalmanje Srinivas Krishnakumar

John T Kaneshige

John Bull

Curtis E Hanson

Jeanette Le

Disclosed is a novel adaptive control method and system called optimal control modification with normalization and covariance adjustment. The invention addresses specifically to current challenges with adaptive control in these areas: 1) persistent excitation, 2) complex nonlinear input-output mapping, 3) large inputs and persistent learning, and 4) the lack of stability analysis tools for certification. The invention has been subject to many simulations and flight testing. The results substantiate the effectiveness of the invention and demonstrate the technical feasibility for use in modern aircraft flight control systems.

Control systems with normalized and covariance adaptation by optimal control modification

A method for modeling error-driven adaptive control of an aircraft. Normal aircraft plant dynamics is modeled, using an original plant description in which a controller responds to a tracking error e(k) to drive the component to a normal reference value according to an asymptote curve. Where the system senses that (1) at least one aircraft plant component is experiencing an excursion and (2) the return of this component value toward its reference value is not proceeding according to the expected controller characteristics, neural network (NN) modeling of aircraft plant operation may be changed. However, if (1) is satisfied but the error component is returning toward its reference value according to expected controller characteristics, the NN will continue to model operation of the aircraft plant according to an original description.

Aircraft system modeling error and control error

A system for emergency aircraft control uses at least one engine and lateral fuel transfer that allows a pilot to regain control over an aircraft under emergency conditions. Where aircraft propulsion is available only through engines on one side of the aircraft, lateral fuel transfer provides means by which the center of gravity of the aircraft can be moved over to the wing associated with the operating engine, thus inducing a moment that balances the moment from the remaining engine, allowing the pilot to regain control over the aircraft. By implementing the present invention in flight control programming associated with a flight control computer (FCC), control of the aircraft under emergency conditions can be linked to the yoke or autopilot knob of the aircraft. Additionally, the center of gravity of the aircraft can be shifted in order to effect maneuvers and turns by spacing such center of gravity either closer to or farther away from the propelling engine or engines. In an alternative embodiment, aircraft having a third engine associated with the tail section or otherwise are accommodated and implemented by the present invention by appropriately shifting the center of gravity of the aircraft. Alternatively, where a four-engine aircraft has suffered loss of engine control on one side of the plane, the lateral fuel transfer may deliver the center of gravity closer to the two remaining engines. Differential thrust between the two can then control the pitch and roll of the aircraft in conjunction with lateral fuel transfer.

Emergency flight control system using one engine and fuel transfer

An emergency flight control system is disclosed for lateral control using only differential engine thrust modulation of multiengine aircraft having at least two engines laterally displaced to the left and right from the axis of the aircraft in response to a heading angle command .psi..sub.c to be tracked. By continually sensing the heading angle .psi. of the aircraft and computing a heading error signal .psi..sub.e as a function of the difference between the heading angle command .psi..sub.c and the sensed heading angle .psi., a track control signal is developed with compensation as a function of sensed bank angle .PHI., bank angle rate .phi., or roll rate p, yaw rate .tau., and true velocity to produce an aircraft thrust control signal ATC.sub..psi.(L,R). The thrust control signal is differentially applied to the left and right engines with equal amplitude and opposite sign such that a negative sign is applied to the control signal on the side of the aircraft to which a turn is required to reduce the error signal until the heading feedback reduces the error to zero.

Emergency multiengine aircraft system for lateral control using

A digital longitudinal Aircraft Propulsion Control (APC) system of a multiengine aircraft is provided by engine thrust modulation in response to comparing an input flightpath angle signal .gamma.c from a pilot thumbwheel or an ILS system with a sensed flightpath angle .gamma. to produce an error signal .gamma.e that is then integrated (with reasonable limits) to generate a drift correction signal to be added to the error signal .gamma.e after first subtracting a lowpass filtered velocity signal Vel.sub.f for phugoid damping. The output error signal is multiplied by a constant to produce an aircraft thrust control signal ATC of suitable amplitude to drive a throttle servo for all engines, each of which includes its own full-authority digital engine control (FADEC) computer. An alternative APC system omits sensed flightpath angle feedback and instead controls the flightpath angle by feedback of the lowpass filtered velocity signal Vel.sub.f which also inherently provides phugoid damping. The feature of drift compensation is retained.

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Tehachapi, CA, United States of America

John J Burken