Development of Robust Flight Control Laws for a Highly Flexible Aircraft in the Frequency Domain

Köthe, Alexander; Luckner, Robert; Ramirez, Pedro J. González; Silvestre, Flávio J.; Pang, Zi Yang; Cesnik, Carlos E. S.

doi:10.2514/6.2016-3394

Cited by 4 publications

(5 citation statements)

References 10 publications

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“…As presented in Sec. I, there are previous examples of linear controllers for flexible and VFAs: two-loop schemes [13,25], multiloop architectures [19], and different cascade controllers [11,15]. Nevertheless, these approaches considered assumptions that made their real-time implementation difficult or unfeasible, such as considering the rigid-body dynamics completely decoupled (which is no longer valid for an aircraft with an asymmetric lateral c.g.).…”

Section: Loop-separation Controllermentioning

confidence: 99%

“…All poles of the closed-loop system must be placed on the left-hand side of the complex plane. The control system must be able to ensure stability under a 25% uncertainty of sensor measurements and control actuation [19,38]. This information may be assessed via a robustness analysis using the small-gain theorem [39].…”

Section: Robustness and Stabilitymentioning

confidence: 99%

“…Köthe et al used a multiloop control structure to ensure stability and optimal shape of the structure of a VFA [19]. This approach showed one of the problems associated with full order or unstructured H ∞ controllers.…”

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confidence: 99%

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Loop-Separation Control for Very Flexible Aircraft

et al. 2020

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In this research, a loop-separation concept (LSC) is applied to a very flexible aircraft. Appealing features of this control architecture include decoupled control logic and the use of high-order models for controller design, thus not requiring model order reduction. The LSC consists of two control loops. The inner loop employs a linear quadratic regulator capable of stabilizing the aircraft while controlling the shape of the half-wings independently from each other by artificially stiffening the structure. Structural dynamics can potentially be used in the design of the inner-loop regulator. The outer-loop design is based on rigid-body outputs. The outer loops for tracking velocity, heading, sideslip angle, and altitude are designed using nonsmooth H ∞ optimization techniques. Numerical results show that structural feedback in the inner loop yields better regulation performance and reduced structural deformations. The autopilot is capable of attaining the commanded reference with low control energy while meeting the maneuver requirements and regulating the elastic deformations of the wing.

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Section: Loop-separation Controllermentioning

confidence: 99%

Section: Robustness and Stabilitymentioning

confidence: 99%

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Loop-Separation Control for Very Flexible Aircraft

et al. 2020

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“…Nastran, and Ansys Workbench) are quite mature, repeated solutions of high-fidelity models are often required to perform stability analysis, 4 sensitivity analysis, 5 dynamic analysis, 6 parameterized design, optimization, 7 and control law design. 8 However, simulations can be computationally expensive and memory intensive due to the large number of degrees of freedom required for accurate solution of these problems, making the application of high-fidelity models impractical or infeasible. Fortunately, in some cases, reduced-order modeling techniques can be used to identify a simpler underlying structure that transforms large-dimensional and large-order nonlinear models into lower-dimensional and lower-order models.…”

Section: Introductionmentioning

confidence: 99%

Regression-based identification and order reduction method for nonlinear dynamic structural models

Wang,

2023

Proceedings of the Institution of Mechanical Engineers, Part G:

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In this paper, we propose a regression-based nonlinear reduced-order model for nonlinear structural dynamics problems, called the Nonlinear Identification and Dimension-Order Reduction (NLIDOR) algorithm. We evaluate the algorithm using a simple toy model, a chain of coupled oscillators and an actual three-dimensional flat plate. The results show that NLIDOR can accurately identify the natural frequencies and modes of the system and capture the nonlinear dynamical features, while the linear Dynamic Mode Decomposition (DMD) method can only capture linear features and is influenced by nonlinear terms. Compared with the full-order model (FOM), NLIDOR can effectively reduce computational cost, while compared with DMD, NLIDOR significantly improves computational accuracy. The results demonstrate the effectiveness and potential of NLIDOR for solving nonlinear dynamic problems in various applications.

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“…[17][18][19] Nevertheless, most of the works pay attention to the study of anti-saturation control and robust control combined with the control input saturation of the unstable system. 20,21 In another word, the limitation of controllable region, influenced by the structural flexibility needs further discussion. Therefore, the main problem is that an approach should be proposed to calculate the controllable region for performance analysis.…”

Section: Introductionmentioning

confidence: 99%

Stability boundary analysis of highly flexible aircraft with control saturation and structural flexibility

Chen

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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In this work, a method has been presented to analyze the influence of control saturation and structural flexibility on the stable radius of highly flexible aircraft. A dynamic model of aircraft is constructed followed by the analysis of kinetic characteristics. In this paper, the closed-loop stability boundary of highly flexible aircraft with open-loop instability is studied. The amplitude limit and bandwidth limit of the control signal are considered in the closed-loop stability boundary calculation. Our analysis shows that the boundary is related to the left eigenvector corresponding to the unstable poles and the amplitude constraint of the control signals. Stability of the boundary of feedback control system further reduces the limitation of the bandwidth of actuators. Focused on the phugoid instability of highly flexible aircraft, computational formulation of the closed-loop stable boundary is achieved. The Monte Carlo analysis has been employed to validate the stable region, under the LQR controller. Both the theory and simulations have nice correlations with each other which verify the stability of the closed-loop system, restricted by the open-loop system, and the influence of control signal bandwidth constraints.

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Development of Robust Flight Control Laws for a Highly Flexible Aircraft in the Frequency Domain

Cited by 4 publications

References 10 publications

Loop-Separation Control for Very Flexible Aircraft

Loop-Separation Control for Very Flexible Aircraft

Regression-based identification and order reduction method for nonlinear dynamic structural models

Stability boundary analysis of highly flexible aircraft with control saturation and structural flexibility

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