During close formation flight of fixed-wing UAVs, the wingman aircraft is subjected to interference from the wake vortex of the leader aircraft, increasing the difficulty of designing the wingman's controller. To address this issue, this paper first proposes a modeling method for aerodynamic coupling in close formation, establishes a mathematical model of the wake vortex for highly swept-back wing UAVs, and studies the mechanism of aerodynamic coupling in close formation. Subsequently, the concept of prescribed-time control is introduced into Incremental Nonlinear Dynamic Inversion (INDI) control, enabling the controller to achieve rapid convergence while maintaining strong robustness. Based on this control method, the inner-loop controller for the wingman aircraft is designed to ensure accurate tracking of command signals under aerodynamic disturbances. Since the incremental nonlinear dynamic inversion controller requires angular rate and angular acceleration signals for controlling the inner loop, but the angular rate signals obtained from sensors in practice contain measurement noise, traditional differentiation methods amplify noise and fail to provide accurate angular acceleration signals. To resolve this, the concept of predefined-time control is incorporated into the tracking differentiator, designing a modified tracking differentiator that achieves simultaneous signal tracking and differentiation extraction under noisy conditions, with both robustness and rapid response. The stability of the proposed controller is proven using the Lyapunov theorem, and digital simulations of the entire closed-loop system are conducted. Simulation results demonstrate that the designed controller achieves the expected control effect and meets the attitude control requirements of the wingman aircraft during fixed-wing UAV close formation flight. Comparison with control methods from other literature shows that in close formation scenarios, the controller designed in this paper exhibits faster convergence, smaller steady-state error, and stronger robustness.

A high-precision transition trajectory optimization and control method for shipborne Vertical Take-off and Landing (VTOL) aircraft is proposed to address the strong coupling nonlinearity between the propulsion system and aerodynamic forces during the transition process, and the sudden change in aerodynamic coefficients caused by the closure of the lift fan inlet hatch at the end of the transition. Firstly, considering the complex actuation structure and the influence of the lift fan inlet hatch, a transition model of the shipborne VTOL aircraft is established based on wind tunnel experimental data. Secondly, the attainable equilibrium set method is used to draw the transition corridor and transition objectives are defined based on corridor boundaries, aircraft dynamic constraints, transition height, and transition time as safety and performance indicators, and an optimization problem is established to solve the optimal transition trajectory using adaptive pseudo-spectral method. Finally, a Preset Time Disturbance Observer of Incremental Nonlinear Dynamic Inversion (PTDO-INDI) method is designed for aircraft control. This method can observe disturbances at preset times, overcome uncertain disturbances, and improve robustness. Simulation and semi physical verification show that the proposed method achieves the optimization of the transition trajectory of shipborne VTOL aircraft and accurate tracking of the optimal trajectory, while effectively suppressing disturbance effects, achieving high-precision transition goals that balance safety and performance.

Considering the influence of external interference and model uncertainty, a prescribed-time increment backstepping fault-tolerant control method is proposed to quickly recover the attitude angle of the aircraft when suffering the wing damage fault. First, based on wind tunnel test data, the aerodynamic characteristics of the aircraft after suffering wing-damage fault are analyzed, and the attitude angle and angular rate dynamics equations considering the change of the center of gravity are established. Second, a prescribed-time based filter is introduced, which can effectively avoid the differential explosion problem in the backstepping method. Then, a prescribed-time incremental backstepping attitude controller is designed to achieve rapid stabilization and precise control of the aircraft's attitude angle. On this basis, considering the higher-order infinitesimal terms ignored during the incremental backstepping design as well as the external perturbations and model uncertainties existing in the system, a preset time-perturbation observer is proposed to accurately estimate and quickly compensate for them, which further improves the fault-tolerance of the proposed attitude controller. It is proved by strict Lyapunov stability that the proposed controller can achieve stable control of the attitude angle within the user-defined time, which is independent of the initial state of the system and the parameters of the proposed controller, and simplifies the process of adjusting the parameters against the convergence time. Finally, numerical simulations verify the effectiveness of the proposed method.

The MAGIC CARPET carrier landing control system relies on stable and accurate flow angle signals. However, flow angle sensors operate in harsh environments, resulting in low accuracy and susceptibility to damage of the sensors. In such cases, other sensor signals can be used to reconstruct the required flow angle signal. However, existing flow angle reconstruction algorithms can only construct the inertial flow angle, and most algorithms overlook drift errors of inertial sensors. During the Magic Carpet carrier landing process, the carrier-based aircraft operates at low speeds and high angles of attack; disturbances from the ship’s wake flow can cause significant deviations between the estimated inertial angle of attack and the true flow angle, hindering the control system’s stability and trajectory correction. To address this issue, an algorithm for reconstructing Magic Carpet carrier landing flow angle is proposed for use in the event of sensor failure. This algorithm estimates the ship’s wake flow, the angle of attack, and the sideslip angle without the need for a flow angle sensor, while also considering the drift errors of inertial sensors. The algorithm is integrated into the Magic Carpet carrier landing control system loop, and the reconstructed flow angle signal is used in the landing control law calculation for digital and hardware-in-the-loop simulation verification. The results demonstrate that the algorithm can estimate the ship’s wake flow and inertial sensor drift errors, producing a reconstructed flow angle signal that accurately reflects the true information of flow angle. The signal is smooth and stable, without diverging over time, and can be used in the Magic Carpet carrier landing control law calculation to maintain a stable flow angle, enabling rapid and precise trajectory correction for the carrier-based aircraft.

This paper proposes a distributed controller that utilizes only distance measurements to address the problem of cooperative circumnavigating an unknown target by Multi-Unmanned Aerial Vehicle (UAV) in a Global Position System (GPS) denial environment. Unlike most existing algorithms, this controller does not require location information of UAV and target. Firstly, a novel guidance control algorithm is designed to drive a single UAV to circle around the target by assuming that the actual distance measurement and the distance rate measurement are available. Secondly, a second-order sliding mode observer is utilized to complete the estimation of the distance rate in a finite time instead of the distance rate measurement. The observer is designed by using distance measurement information, allowing the UAV to complete the circumnavigation mission using only distance measurement. Then, on the basis of the designed distance circling controller, the finite time observer and the distance measurement information are used to complete the relative position estimation, and then a velocity coordination algorithm is developed to realize the uniform circumnavigation of the target by multiple UAVs. Finally, the numerical and Hardware-in-the-Loop (HIL) simulation results verify the effectiveness of the proposed method.