In this article, the high angle of attack (AOA) maneuver control problem is studied under multiple disturbances and uncertainties For the first time, the switched distributed delay is constructed 

Disturbance observer–based neural flight control for aircraft with switched time-varying distributed delays:

In this paper, a new framework of the robust adaptive neural control for nonlinear switched stochastic systems is established in the presence of external disturbances and system uncertainties. In the existing works, the design of robust adaptive control laws for nonlinear switched systems mainly relies on the average dwell time method, while the design and analysis based on the model-dependent average dwell time (MDADT) method remains a challenge. An improved MDADT method is developed for the first time, which greatly relaxes the requirements of Lyapunov functions of any two subsystems. Benefiting from the improved MDADT, a switched disturbance observer for discontinuous disturbances is proposed, which realizes the real-time gain adjustment. For known and unknown piecewise continuous nonlinear functions, a processing method based on the tracking differentiator and the neural network is proposed, which skillfully guarantees the continuity of the control law. The theoretical proof shows that the semiglobal uniform ultimate boundedness of all closed-loop signals can be guaranteed under switching signals with MDADT property, and simulation results of the longitudinal maneuvering control at high angle of attack are given to further illustrate the effectiveness of the proposed framework. 

Adaptive neural control for nonlinear switched systems with improved MDADT and its applications

Adaptive neural tracking control for high angle of attack maneuver with average dwell time


Purpose
This study aims to achieve the post-stall pitching maneuver (PSPM) and decrease the deflection frequency of aircraft actuators controlled by the robust backstepping method based on event-triggered mechanism (ETM), nonlinear disturbance observer (NDO) and dynamic surface control (DSC) techniques.


Design/methodology/approach
To estimate unsteady aerodynamic disturbances (UADs) to suppress their adverse effects, the NDO is designed. To avoid taking the derivative of the virtual control law directly and eliminate the coupling term of the system states and dynamic surface errors in the stability analysis, an improved DSC is developed. Combined with the NDO and DSC techniques, a robust backstepping method is proposed to achieve the PSPM. Furthermore, to decrease the deflection frequency of the aircraft actuators, a state-dependent ETM is introduced.


Findings
An ETM-and-NDO-based backstepping method with an improved DSC technique is developed to achieve the PSPM and decrease the deflection frequency of aircraft actuators. And simulation results are presented to verify the effectiveness of the proposed paper.


Originality/value
Few studies have been conducted on the control of the PSPM in which the lateral and longitudinal attitude dynamics are coupled with each other considering the UADs. Moreover, the mechanism that can decrease the deflection frequency of aircraft actuators is rarely developed in existing research. This study proposes an ETM-and-NDO-based backstepping scheme to address these problems with satisfactory performance of the PSPM.


Robust backstepping control for maneuver aircraft based on event-triggered mechanism and nonlinear disturbance observer

Although the problem of locked-in deep stall is well known and has a long history, there currently exists no consistent procedure that can guarantee recovery. Past studies have suggested that it might be possible to rock the aircraft nose to destabilise the stable deep stall trim point, thereby gaining enough momentum to push the nose down. However, the methods used in these studies are either of preliminary or empirical nature and brought inconsistent results. In this paper, we use bifurcation analysis to derive a recovery manoeuvre, specifically by assessing the aircraft’s nonlinear frequency response under an elevator forcing. The ensuing nonlinear Bode plot detects unstable (divergent) solutions near resonance that contributes to a successful deep stall recovery. Moreover, the nonlinear resonant frequency is slightly lower than the result obtained using linear analysis, and time simulation shows that relying on the linear result does not lead to a successful recovery. It was also found that at the high angles-of-attack associated with deep stall, the frequency separation between the short period and phugoid mode is significantly reduced, leading to only one visible peak in the frequency response. This feature is also reflected in the time-domain step response. 

https://research-information.bris.ac.uk/ws/files/312655220/2022_SciTech_deep_stall.pdf

A Frequency-Domain Approach to Analysing Dynamic Deep Stall Recovery

In this paper, the problem of deep-stall recovery will be studied for the aircraft without longitudinal static stability. A new longitudinal short-period deep-stall model is established in the presence of time-varying distributed delays. Based on bifurcation analysis method, the effects of actuator fault on deep stall are analyzed in depth. Considering the system uncertainty, actuator fault, input saturation and unsteady disturbance, a finite-time prescribed performance deep-stall recovery law is designed according to the bifurcation analysis results. Further, to avoid the singularity problem in traditional finite-time control, an improved finite-time control law is developed. Stability of the closed-loop system is proved by common Lyapunov functional method. And simulations are given to illustrate the validity of the proposed deep-stall recovery control scheme.

Analysis and Recovery of Aircraft Deep-Stall Phenomena Using Bifurcation Analysis

Summary This article studies the high angle of attack (AOA) maneuver control based on an improved prescribed performance method, that is, switched prescribed performance control (SPP). Different fr...

High angle of attack flight control based on switched prescribed performance

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Analysis and Recovery of Aircraft Deep-Stall Phenomena Using Bifurcation Analysis

High angle of attack flight control based on switched prescribed performance

Adaptive neural tracking control for high angle of attack maneuver with average dwell time