Self-repairing flight control system program overview

Abstract

The Air Force Flight Dynamics Laboratory initiated the Self-Repairing Flight Control System Program in 1984. The program objective is to significantly improve the reliability, maintainability, survivability, and life cycle cost of aircraft flight control systems through aerodynamic reconfiguration and maintenance diagnostics. When a control surface becomes impaired due to a failure or battle damage, a reconfiguration strategy uses the remaining control surfaces to substitute for the lost force and moment generating capability. The reduced criticality of individual control surfaces allows for simplification of upstream flight control system components, e.g., actuators. Reconfiguration technology includes a Positive Pilot Alert system which informs the pilot of impairments and new performance limits. Maintenance diagnostics technology includes both expert ground based systems, to help flight line maintenance personnel, and airborne systems, to begin the diagnostics process before the aircraft lands. The diagnostics systems significantly decrease the time to diagnose failures and lover cannot duplicate and retest OK maintenance actions. The program transitions technology to current and advanced fighter aircraft through feasibility studies, development studies, design criteria development, ground simulations, field demonstrations, and fighter flight tests.

Adaptive Backstepping Flight Control for Modern Fighter Aircraft

“…An important early example of this type of approach was developed by General Electric Aircraft Controls [55]. This design used a single extended Kalman estimator to perform all FDIE and a pseudo-inverse approach based on a linearized model of the aircraft was used to determine controller effector commands, so that the degraded aircraft would generate the same accelerations as the nominal aircraft.…”

“…The least-squares update law forΘ and the covariance update are defined aṡ 55) where ν ≥ 0 is the normalization coefficient and λ ≥ 0 is a forgetting factor. By Lemma 6.1 the modular controller with x-swapping filters and least-squares update law achieves global asymptotic tracking of the modified tracking errors.…”

Historical Overview of Research in Reconfigurable Flight Control

“…Much of the research in reconfigurable control in the 1980s would fit within the definitions provided earlier with a requirement for explicit failure detection, isolation, and estimation (FDIE). An important early example of this type of approach was developed by General Electric (GE) Aircraft Controls in Binghamton for the USAF [16]. The initial design used a single extended Kalman estimator to perform all FDIE.…”

Retrofit systems for reconfiguration in civil aviation

“…Chandler [3], 20% of aircraft losses are due to faulty or damaged control systems. Zemlaykov [2] notes that today, control surfaces are the primary cause of control system unreliability.…”

“…Many of the early reconfiguration attempts via gain scheduling were based on Pseudo-Inverse Methods (PIM) [2,10,3]. The objective of this approach was to minimize the differences between the nominal and failed linear time-invariant closed loop dynamics in the sense of a Frobenius norm [10].…”