Loss of Control Prevention of an Agile Aircraft: Dynamic Command Saturation Approach

TL;DR

This paper introduces a Lyapunov-based dynamic command saturation method to prevent loss of control in agile aircraft during extreme maneuvers, enhancing stability and maneuverability beyond conventional limits.

Contribution

It presents a novel control architecture utilizing incremental nonlinear dynamic inversion and Lyapunov-based command saturation to improve aircraft stability during extreme maneuvers.

Findings

Expanded stable maneuverable volume by up to 55%

Superiority over conventional state limiters demonstrated in simulations

Effectively softens excessive pilot commands in-flight

Abstract

The prevention of the loss of control in agile aircraft during the extreme maneuvers is of concern due to the nonlinear aerodynamics and flight dynamics nature of the aircraft in this study. Within this context, the primary objective is to present an architectural framework and elucidate the methodology for its determination. This architecture enables agile maneuvering aircraft to execute more extreme maneuvers while avoiding departure from stable flight, surpassing maneuverability capabilities of conventional state limiters. Hence, the notion of an incremental attainable moment set is introduced for an instantaneous controllability investigation using demanded control moment coefficients derived in the high-level controller, which is the incremental nonlinear dynamic inversion. In the event of detecting a violation of controllability boundaries, Lyapunov-based dynamic command saturation is employed to limit pilot commands, preventing the aircraft from initiating departure from stable flight. As a result, abrupt and excessive pilot inputs are dynamically softened in-flight, and presumable departure tendencies are mitigated. Consequently, the superiority of the proposed method over conventional state limiters is proven through the flight simulations of agile and abrupt maneuvers, as well as Monte Carlo simulations that demonstrate the expansion of stable maneuverable volumes up to 55%.