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

TL;DR

This work tackles loss of control in agile aircraft by introducing an online framework that couples real-time controllability assessment with Lyapunov-based command saturation to bound pilot inputs during extreme maneuvers. It defines an Incremental Attainable Moment Set for instantaneous controllability and integrates it with an INDI-based control augmentation and optimization-based control allocation for an over-actuated F-16 model. The method aims to maximize maneuverability while preventing departure, demonstrated through two aggressive maneuvers and extensive Monte Carlo simulations that show a substantial expansion of the stable maneuverable volume compared to conventional state limiters. The findings suggest practical potential for safe, care-free aggressive flight, with future work on adaptive Lyapunov gains and applicability to other aircraft types and fault scenarios.

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%.

Figures (16)

• Figure 1: Entire flight control architecture.
• Figure 2: Overview of the proposed loss of control prevention logic
• Figure 3: State trajectory of the maneuver #1 without loss of control prevention.
• Figure 4: State trajectory of the maneuver #1 with loss of control prevention: indicates the intervention of the Lyapunov assessment.
• Figure 5: Command saturation trajectory of the maneuver #1 with loss of control prevention: indicates the intervention of the Lyapunov assessment.