Challenges and Innovations in Aircraft Flight Control

Dear Colleagues,

Recent years have seen a rise in the aircraft performance, safety, and autonomy requirements for both crewed and uncrewed aircraft. This is creating new flight control challenges for different classes of aircraft. Civilian airliners are evolving towards increasing their levels of automation, but this is creating flight control safety challenges. Uncrewed aerial vehicles (UAVs) have also evolved with an unprecedented variety in their designs. Aircraft control systems are also increasingly required to save energy and reduce emissions, particularly in the case of electric aircraft, including urban air mobility.

In this Special Issue, particular prominence will be given to the development of estimation and control methods and algorithms for:

- Fault tolerant aircraft control systems under sensor and actuator faults;

- Optimal aircraft control allocation using multiple actuators;

- Flight envelope protection for enhanced flight safety;

- Optimal aircraft control problems of practical significance, including energy optimality, optimal tradeoffs, time optimality, and optimal coverage path planning;

- Adaptive flight control to handle aircraft parameter variations;

- Aircraft state, fault, disturbance, and model uncertainty estimation using advances in observers, Kalman filters, and other estimation methods;

- Advances in aircraft robust control;

- Hybrid (combined continuous and discrete time) control approaches for flight profiles with multiple flight modes;

- Artificial intelligence in flight control;

- Advances in the control of hybrid (cruise and VTOL) aircraft configurations;

- Combining open-loop and closed-loop aircraft control systems;

- Advances in autonomous and full authority flight control systems.

Review, theoretical, simulation-based, and practical-type papers are all within the scope of this Special Issue. All aircraft types are also within the scope of this Special Issue.

Dr. Nadjim Horri
Dr. Toufik Souanef
Guest Editors

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• UAV
• electric aircraft
• fault
• disturbance
• optimal
• robust control
• adaptive
• hybrid control

Title: A Robust Adaptive PID-like Controller for Quadrotor UAV Systems
Authors: Ahsene Boubakir; Toufik Souanef; Salim Labiod; James F. Whidborne
Affiliation: Cranfield University
Abstract: This paper introduces a stable adaptive PID-like control scheme for quadrotor Unmanned Aerial Vehicle (UAV) systems. The PID-like controller is designed to closely estimate an ideal controller to meet specific control objectives, with its gains being dynamically adjusted through a stable adaptation process. The adaptation process aims to reduce the discrepancy between the ideal controller and the PID-like controller in use. This method is considered model-free, as it does not require knowledge of the system's mathematical model. The stability analysis performed using a Lyapunov method demonstrates that every signal in the closed-loop system is Uniformly Ultimately Bounded (UUB). The effectiveness of the proposed PID-like controller is validated through simulations on a quadrotor for path following, ensuring accurate monitoring of the target positions and yaw angle, while simultaneously preserving stability in pitch and roll. Simulation results highlight the performance of this control scheme.

Title: Autonomous Parafoil Flaring Control System for eVTOL Aircraft
Authors: Stephen Doran, Toufik Souanef, and James Whidborne
Affiliation: Cranfield University
Abstract: Reducing landing kinetic energy during emergency landings is critical for minimizing occupant injury in eVTOL aircraft. This study presents the development of an autonomous parafoil control system for impact point targeting and flare control. A model predictive controller (MPC) for 6-degree-of-freedom parafoil and eVTOL payload model, was designed incorporating an inner-loop flare controller for descent speed-based flare height adjustments and an outer-loop nonlinear MPC to minimize line-of-sight error. Two guidance methods were explored: a standard fixed impact point approach and an adaptive method that adjusts the target point dynamically to account for horizontal travel during flaring. The standard method outperformed the uncontrolled system in 79.64% of cases, while the adaptive method achieved success in 40.73% of scenarios, with both methods maintaining vertical landing velocities below 8 m/s in all tested cases. Controller performance degraded under higher wind speeds and large control derivative variations, with the adaptive method position error attributed to flare distance estimation inaccuracies.