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Structures, Actuation and Control of Morphing Systems

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A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: closed (31 August 2024) | Viewed by 27948

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Prof. Dr. Chen Wang

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Guest Editor

College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Interests: morphing aircraft; smart structures; aircraft design; structural dynamics
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Michael I. Friswell

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Guest Editor

Department of Aerospace Engineering, Swansea University, Swansea SA1 8EN, UK
Interests: morphing aircraft; structural dynamics; structural health monitoring; rotordynamics; smart structures; nonlinear dynamics
Special Issues, Collections and Topics in MDPI journals

Dr. Jiaying Zhang

E-Mail Website
Guest Editor

School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
Interests: morphing aircraft; structural dynamics; smart structure; nonlinear dynamics system
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Morphing technologies have the potential to improve aircraft performance and have attracted attention from researchers around the world in the past few decades. Through morphing, aircraft can change shape or even configuration in different flight conditions, which accordingly improves performance in multiple flight phases compared to fixed-geometry aircraft.

Structures, actuation, and control are among the key factors to design, manufacture, and certificate a promising morphing system. Different to conventional aircraft structures, morphing structures need to simultaneously have load-carrying and shape-changing capabilities, which makes it challenging for them to remain lightweight. Compliant structures and mechanisms have been investigated, and many promising solutions have been proposed. In terms of actuation, it is usually necessary to integrate actuators into structures. Quite a few options have appeared, including conventional electric actuators and innovative smart materials. With actuation integrated, the next step is to consider how to control the shape of the system accurately, considering the effects of structural stiffness, actuation force, and external loads. Finally, investigation of the aeroelastic effects of morphing aircraft and the control approach determined to facilitate shape control accuracy is required.

We are pleased to announce this Special Issue on “Structures, Actuation, and Control of Morphing Systems” and kindly invite you to submit full research and review papers on the following topics:

Morphing aircraft/rotorcraft;
Morphing wings;
Morphing structures;
Smart structures;
Actuation;
Aeroelasticity;
Flight control.

Dr. Chen Wang
Prof. Dr. Michael I. Friswell
Dr. Jiaying Zhang
Guest Editors

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Published Papers (11 papers)

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Research

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26 pages, 10513 KiB

Open AccessArticle

Structural Analysis and Experimental Tests of a Morphing-Flap Scaled Model

by Mürüvvet Sinem Sicim Demirci, Rosario Pecora, Luca Chianese, Massimo Viscardi and Metin Orhan Kaya

Aerospace 2024, 11(9), 725; https://doi.org/10.3390/aerospace11090725 - 5 Sep 2024

Cited by 1 | Viewed by 1890

Abstract

The implementation of morphing wing mechanisms shows significant potential for improving aircraft performance, as highlighted in the recent literature. The Clean Sky 2 AirGreen 2 European project team is currently performing ground and wind tunnel tests to validate improvements in morphing wing structures. The project aims to demonstrate the effectiveness of these morphing designs on a full-scale flying prototype. This article describes the design methodology and structural testing of a scaled morphing-flap structure, which can adapt to three different morphing modes for various flight conditions: low-speed (take-off and landing) and high-speed (cruise). A scale factor of 1:3 was selected for the wind tunnel test campaign. Due to challenges in scaling the embedded mechanisms and actuators necessary for shape-changing, a full geometrical scale of the real flap prototype was not feasible. Static analyses were performed using the finite element method to address critical load conditions determined through three-dimensional computational fluid dynamic (CFD) analysis. The finite element (FE) analysis was conducted and the results were compared with the empirical data from the structural test. Good correlations were found between the structural testing results and numerical predictions, including static deflections and elastic deformations under applied loads. This indicates that the modeling approaches used during the design and testing phases were highly successful. Based on simulations for the ultimate load conditions tested during the wind tunnel tests, the scaled flap prototype has been deemed suitable for further testing. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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12 pages, 3458 KiB

Open AccessArticle

Conceptual Design of Compliant Structures for Morphing Wingtips Using Single-Row Corrugated Panels

by Ziyi He, Siyun Fan, Chen Wang, Songqi Li, Yan Zhao, Xing Shen and Jiaying Zhang

Aerospace 2024, 11(8), 682; https://doi.org/10.3390/aerospace11080682 - 19 Aug 2024

Cited by 1 | Viewed by 1734

Abstract

Morphing wingtips have the potential to improve aircraft performance. By connecting the wingtips and the wings with a compliant structure, a continuous aerodynamic surface can be achieved for a better aerodynamic performance. However, how to maintain the shape-changing capability while keeping a high stiffness to carry aerodynamic loads is a key problem. In this paper, based on asymmetric stiffness, a type of single-row corrugated panel is designed to satisfy the limited space around the wingtip. A finite element model of the single-row corrugated panels is established, and parameter analysis is performed to investigate the impact of the thickness characteristics of the corrugated panel on the folding angle. The corrugated panel is then optimised to find the maximum folding angle. Based on the optimisation results, corrugated panels with asymmetric and symmetric stiffness are fabricated and tested. The results demonstrate that the asymmetric stiffness corrugated panels have the capability to increase the wingtip folding angle. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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25 pages, 12920 KiB

Open AccessArticle

Size-Dependent Finite Element Analysis of Functionally Graded Flexoelectric Shell Structures Based on Consistent Couple Stress Theory

by Zhuo Deng and Yan Shang

Aerospace 2024, 11(8), 661; https://doi.org/10.3390/aerospace11080661 - 12 Aug 2024

Cited by 5 | Viewed by 4294

Abstract

The functionally graded (FG) flexoelectric material is a potential material to determine the structural morphing of aircrafts. This work proposes the penalty 20-node element based on the consistent couple stress theory for analyzing the FG flexoelectric plate and shell structures with complex geometric shapes and loading conditions. Several numerical examples are examined and prove that the new element can predict the size-dependent behaviors of FG flexoelectric plate and shell structures effectively, showing good convergence and robustness. Moreover, the numerical results reveal that FG flexoelectric material exhibits better bending performance and higher flexoelectric effect compared to homogeneous materials. Moreover, the increase in the material length scale parameter leads to a gradual increase in the natural frequencies of the out-of-plane modes of FG flexoelectric plate/shell, while the natural frequencies of the in-plane modes change minimally, resulting in the occurrence of mode-switching phenomena. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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15 pages, 5813 KiB

Open AccessArticle

Numerical Analysis of the Water Entry Process of the Cabin Structure of the Trans-Domain Morphing Aircraft Considering Structural Deformation

by Yu Zhang, Ziyi He, Chen Wang, Qi Hu, Songwen Dong, Xing Shen, Jun Zhang and Taoxi Wang

Aerospace 2024, 11(8), 611; https://doi.org/10.3390/aerospace11080611 - 25 Jul 2024

Viewed by 1258

Abstract

During the water entry process of a trans-domain morphing aircraft, significant impact forces are generated when the aircraft hits the water surface, which will potentially cause the deformation of the cabin structure and might damage the structure or onboard devices. Thus, it is necessary to investigate the water entry process of the cabin structure. This paper analyses changes in fluid loads and the corresponding structural responses during the water entry process. Firstly, the numerical model is established for the water entry process and the modeling method is validated by comparing the results to the experimental data. An empirical formula is developed to correlate the impact loads with the water entry velocities. Then, fluid–structure interaction analysis of the water entry process is performed using a two-way coupling approach. The relationship between structural deformation and the water entry process is then investigated. The results are compared with those without considering the structural deformation. The empirical formula is then modified to reflect the effects of the deformation. The results show that structural deformation will disperse the impact load, which represents different responses compared to the rigid cabin structure. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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19 pages, 31051 KiB

Open AccessArticle

A Comprehensive Study on the Aerodynamic Characteristics of Electrically Controlled Rotor Using Lattice Boltzmann Method

by Lingzhi Wang and Taoyong Su

Aerospace 2023, 10(12), 996; https://doi.org/10.3390/aerospace10120996 - 28 Nov 2023

Cited by 3 | Viewed by 2172

Abstract

An electrically controlled rotor (ECR) is a kind of swashplateless rotor that implements the primary control via the trailing-edge flap system instead of a swashplate and demonstrates great potential in vibration reduction and noise alleviation. In this paper, the mesoscopic numerical simulation method known as the lattice Boltzmann method (LBM) is employed to investigate the aerodynamic characteristics of an ECR. In the LBM, the discretized Boltzmann transport equation is solved to simulate the macroscopic motion of the fluid, and the D3Q27 model is applied for this study. The effects of the flap deflection on the ECR aerodynamic characteristics can be accurately included with the appropriate refined wall lattice resolution. On this basis, the adaptive wake-refinement strategy is applied to track the evolution of the wake and adequately capture details of the wake structure in the wake flow field. Based on this method, an aerodynamic analysis model for the ECR can be established on the XFlow simulation platform. The aerodynamic analysis model is validated, and the results indicate that the LBM can accurately capture the details of the rotor flow field and calculate blade aerodynamic load, as well as predict the downwash of the rotor. Therefore, based on this model, the ECR aerodynamic characteristics under hovering and forward flight conditions are analyzed, and the effects of the flap deflection on the wake structure, induced inflow, and disc load can be captured. The results indicate that a relatively large flap deflection required to trim the rotor will cause the additional intense flap wake vortex in the ECR wake flow field, apart from the concentrated vorticity at the blade tip and root demonstrated in the conventional rotor wake flow field, and thus significantly change the distributions of the disc-induced inflow and aerodynamic load. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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16 pages, 4693 KiB

Open AccessArticle

Aerodynamic Exploration on Rough Airfoil Based on Overlapping Feathers of a Swift-Wing Structure

by Wei Huang, Qing Zhang, Jinsheng Xu, Jindong Wang, Jian Zheng and Xiong Chen

Aerospace 2023, 10(8), 660; https://doi.org/10.3390/aerospace10080660 - 25 Jul 2023

Cited by 2 | Viewed by 2403

Abstract

To investigate the flow mechanism of feather-like rough airfoils based on swift wings, computational simulations were employed to explore their overall aerodynamic characteristics in comparison to equivalent smooth airfoils. The study focused on angles of attack ranging from 0° to 20° at low Reynolds numbers. The results reveal that the rough airfoil exhibits higher lift and lower drag compared to the smooth airfoil at moderate angles of attack ranging from 6° to 10°, resulting in significantly improved aerodynamic efficiency. Notably, at an angle of attack of 8°, the aerodynamic efficiency is increased by 19%. However, at angles of attack smaller than 6°, the increase in drag outweighs the increase in lift, leading to lower aerodynamic efficiency for the rough airfoil. Conversely, when the angle of attack exceeds 16°, both airfoils experience separated flow-dominated flow fields, resulting in comparable effective aerodynamic shapes and similar aerodynamic efficiencies. Furthermore, the study found that increasing the Reynolds number results in greater pressure differences in the flow field, leading to higher aerodynamic efficiency. These preliminary conclusions are valuable for elucidating the flight mechanisms of bird-feather-like wings and can inform the design or morphing design of bio-inspired micro aerial vehicles in the near future. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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19 pages, 8674 KiB

Open AccessArticle

Rapid Parametric CAx Tools for Modelling Morphing Wings of Micro Air Vehicles (MAVs)

by Ángel Antonio Rodríguez-Sevillano, María Jesús Casati-Calzada, Rafael Bardera-Mora, Javier Nieto-Centenero, Juan Carlos Matías-García and Estela Barroso-Barderas

Aerospace 2023, 10(5), 467; https://doi.org/10.3390/aerospace10050467 - 17 May 2023

Cited by 5 | Viewed by 1879

Abstract

This paper shows a series of tools that help in the research of morphing micro air vehicles (MAVs). These tools are aimed at generating parametric CAD models of wings in a few seconds that can be used in aerodynamic studies, either via CFD directly using the model obtained or via wind tunnel through rapid prototyping with 3D printers. It also facilitates the analysis of morphing wings by allowing for the continuous parametric deformation of the airfoils and the wing geometry. In addition, one of the tools greatly simplifies the purely experimental design of this type of vehicle, allowing the transfer of experimental measurements to the computer, generating virtual models with the same deformation as the physical model. This software has two fundamental parts. The first one is the parameterization of the airfoils, for which the CST (Class-Shape Transformation) method will be used. CST coefficients can be modified according to the actuator variable that changes the wing geometry. The second part is the generation of a three-dimensional parametric model of the wing. We used OpenCASCADE technology in its Python version called PythonOCC, which enables the generation of geometries with good surface quality for typical and non-standard wing shapes. Finally, the use of this software for the study of a morphing aircraft will be shown, as well as improvements that could be incorporated in the future to increase its capabilities for the design and analysis of MAVs. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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23 pages, 9863 KiB

Open AccessArticle

Multidisciplinary Design and Optimization of Variable Camber Wing with Non-Equal Chord

by Yu Wang, Xiang Li, Tingjia Wu and Hailian Yin

Aerospace 2023, 10(4), 336; https://doi.org/10.3390/aerospace10040336 - 28 Mar 2023

Cited by 3 | Viewed by 2319

Abstract

Since the taper ratio of most wings is not equal to 1, the beam-disk trailing edge deflection mechanism originally designed for the rectangular wing is not fully applicable to the non-equal chord wing. Moreover, it is not only expected that the wing shape can achieve excellent aerodynamic performance under different flight conditions, but one also needs to consider whether the flexible skin can achieve this deformation. This paper used the honeycomb composite structure with zero Poisson’s ratio as the flexible skin of the trailing edge for the variable camber wing, and designed the beam-disk trailing edge deflection mechanism for the non-equal chord wing. The aerodynamic configuration was optimized considering the deformation capability of the skin, and the multidisciplinary design and optimization method of the variable camber wing with non-equal chord was studied. The results show that the aerodynamic performances of the optimized non-equal chord wings were better than before under all given flight conditions. The flexible skin could withstand the strain caused by the maximum deflection of the trailing edge of the wing, and the weight of the wing structure was reduced by 47.1% compared with the initial design when the structural stiffness and strength were satisfied. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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23 pages, 9066 KiB

Open AccessArticle

Design of a Distributedly Active Morphing Wing Based on Digital Metamaterials

by Zhigang Wang, Qi Wu, Yifei Lu, Panpan Bao, Yu Yang, Daochun Li, Xiasheng Sun and Jinwu Xiang

Aerospace 2022, 9(12), 762; https://doi.org/10.3390/aerospace9120762 - 27 Nov 2022

Cited by 2 | Viewed by 3628

Abstract

Morphing wings are a typical application of shape-adaptive structures in aviation, which play an important role in improving the comprehensive performance of an aircraft. However, traditional morphing wings based on purely mechanical, rigid-flexible coupling, or purely flexible structures usually cannot achieve a distributed morphing ability and have limitations in weight, intelligence level, and reliability. In this paper, a distributed morphing lattice structure based on variable geometry digital metamaterials is proposed. The innovative structural concept consists of three types of fundamental cells featuring remarkably different mechanical properties and three other types of derived cells. One type of the derived cells embedded with micro-actuators, named an active cell, can autonomously extend or contract. All these cells can be reversibly assembled in a random sequence to form an active distributed morphing lattice structure with the ability to realize different target aerodynamic contours. In addition, taking a simplified variable thickness wing as a designing case, this paper develops a cell combination optimization methodology on the basis of a heuristic algorithm to determine the optimal combination sequence of the six types of basic cells and the actuator inputs of active cells collaboratively. Final results show that the optimized lattice structure can morph its outer surface into a predefined aerodynamic contour with a maximum deviation of 3 mm. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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Review

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27 pages, 10948 KiB

Open AccessReview

Review on the Structure Design of Morphing Winglets

by Wenbo Wang and Guoqing Yuan

Aerospace 2024, 11(12), 1004; https://doi.org/10.3390/aerospace11121004 - 4 Dec 2024

Cited by 1 | Viewed by 2194

Abstract

Winglets have a significant impact on the aerodynamic performance of aircraft. When aircraft are in different flight phases such as takeoff, climb, cruise, descent, and landing, traditional fixed winglets often cannot provide optimal performance gains. If winglets that can morph according to different flight conditions are employed, it is expected that the aircraft’s lift-to-drag ratio and control performance can be optimized throughout the entire flight process. This paper reviews the current research status, from theoretical studies on the performance gains of morphing winglets and design studies based on mechanical transmission mechanisms, smart materials and novel structures, to optimization techniques and testing and verification technologies in the design of morphing winglets. It elucidates two main reasons for the low technological maturity of current morphing winglet research, and points out three areas worthy of further in-depth study. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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24 pages, 7273 KiB

Open AccessReview

A Brief Review of the Actuation Systems of the Morphing Systems in Wind Tunnel Models and a Case Study

by Guogang Pan, Xiaoyu Cui, Pengfei Sun and Biling Wang

Aerospace 2024, 11(8), 666; https://doi.org/10.3390/aerospace11080666 - 13 Aug 2024

Cited by 1 | Viewed by 1745

Abstract

Typical wind tunnel testing involves a series of configuration changes (to the angles of control surfaces) to simulate the lift and resistance characteristics of control surfaces in different flight conditions. It is very time-consuming and labor-intensive to manually change the angles of control surfaces, especially in the large continuous reflux wind tunnel. Thus, there is a demand for a morphing system design within the wind tunnel model that can deflect the control surfaces remotely and automatically. The basic design flow and characteristics of different actuator techniques for the morphing systems were summarized in this paper, including electromechanical actuator, pneumatic actuator, shape memory material actuator and piezoelectric actuator. In the case study, the accuracy of the control surface angle and aerodynamic performance of the ultrasonic-driven automatic control surface system reached the level of traditional fixed control surface systems, while its efficiency was much higher than that of the traditional fixed control surface systems. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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