This paper presents the design of an asymmetrically variable wingtip anhedral angles morphing aircraft,inspired by biomimetic mechanisms,to enhance lateral maneuver capability.Firstly,we establish a lateral dynamic mo...This paper presents the design of an asymmetrically variable wingtip anhedral angles morphing aircraft,inspired by biomimetic mechanisms,to enhance lateral maneuver capability.Firstly,we establish a lateral dynamic model considering additional forces and moments resulting during the morphing process,and convert it into a Multiple Input Multiple Output(MIMO)virtual control system by importing virtual inputs.Secondly,a classical dynamics inversion controller is designed for the outer-loop system.A new Global Fast Terminal Incremental Sliding Mode Controller(NDO-GFTISMC)is proposed for the inner-loop system,in which an adaptive law is implemented to weaken control surface chattering,and a Nonlinear Disturbance Observer(NDO)is integrated to compensate for unknown disturbances.The whole control system is proven semiglobally uniformly ultimately bounded based on the multi-Lyapunov function method.Furthermore,we consider tracking errors and self-characteristics of actuators,a quadratic programmingbased dynamic control allocation law is designed,which allocates virtual control inputs to the asymmetrically deformed wingtip and rudder.Actuator dynamic models are incorporated to ensure physical realizability of designed allocation law.Finally,comparative experimental results validate the effectiveness of the designed control system and control allocation law.The NDO-GFTISMC features faster convergence,stronger robustness,and 81.25%and 75.0%reduction in maximum state tracking error under uncertainty compared to the Incremental Nonlinear Dynamic Inversion Controller based on NDO(NDO-INDI)and Incremental Sliding Mode Controller based on NDO(NDO-ISMC),respectively.The design of the morphing aircraft significantly enhances lateral maneuver capability,maintaining a substantial control margin during lateral maneuvering,reducing the burden of the rudder surface,and effectively solving the actuator saturation problem of traditional aircraft during lateral maneuvering.展开更多
Fixed-wing long-endurance aircraft play an important role in many fields.However,to reduce drag,these aircraft often have an enormous aspect ratio and wingspan,leading to challenges such as high requirements for takeo...Fixed-wing long-endurance aircraft play an important role in many fields.However,to reduce drag,these aircraft often have an enormous aspect ratio and wingspan,leading to challenges such as high requirements for takeoff and landing sites and poor wind resistance.Morphing may be able to solve this problem,but conventional morphing aircraft often employ complex actuation mechanisms and actuators to drive the morphing process.The associated costs in terms of structural weight increase and space occupancy are prohibitively high.First,this article develops a high-aspect-ratio aircraft with aerodynamic-driven morphing and validates the rationality and feasibility of this concept through flight tests.Then,focusing on the RQ-4‘‘Global Hawk”as the design baseline,the article explores multidisciplinary overall design methods for the aircraft,analyzing the comprehensive impact of morphing on aerodynamic,structural,and flight control design.Finally,the article elaborates on the benefits and costs associated with aerodynamic-driven morphing.展开更多
Morphing technology is considered a crucial direction for the future development of aircraft.However,conventional morphing aircraft often employ complex actuation mechanisms and actuators to drive the morphing process...Morphing technology is considered a crucial direction for the future development of aircraft.However,conventional morphing aircraft often employ complex actuation mechanisms and actuators to drive the morphing process.The associated costs in terms of structural weight increase and space occupancy are prohibitively high,even exceeding the benefit of morphing.Especially for high aspect ratio aircraft with large root bending moments,it is very difficult for actuators to directly drive wing deformation.To address this issue,aerodynamic forces generated by control surface deflection can be utilized as an alternative to actuator-driven morphing.This approach reduces the overall cost of morphing while enhancing its benefits.This novel aerodynamic-driven morphing technique imposes new requirements and challenges on the aerodynamic design of aircraft.With a combination of flight experiments and numerical simulations,this article analyzes the variations in aerodynamic forces during the aerodynamic-driven process.Using a high aspect ratio longendurance UAV as the design baseline,the design method of the control surface for aerodynamic-driven morphing is also discussed.展开更多
Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent ...Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.展开更多
Inspired by flight biology,morphing flight technology has great potential to improve the adaptability and maneuverability of aircraft.This paper is devoted to the flight control problem of morphing aircraft,and aimed ...Inspired by flight biology,morphing flight technology has great potential to improve the adaptability and maneuverability of aircraft.This paper is devoted to the flight control problem of morphing aircraft,and aimed at safe and fuel-saving flight through morphing actively.Specifically,the longitudinal dynamics of a morphing aircraft with telescopic wings is modelled as a strict-feedback nonlinear system.Through fitting the expression of aerodynamic parameters by the mor-phing ratio,the model uncertainties induced by morphing errors are embedded in the dynamics.To meet the safety and fuel-saving requirements,an Adaptive Coordinated Tracking Control Scheme(ACTCS)is then proposed,which consists of a morphing control module and a tracking control module.For the morphing control module,an on-line morphing decision model is given in an optimization process with respect to the morphing ratio,and a second-order tracking filter is introduced to smooth the decision output and ensure the physical realizability.For the tracking control module,the novel adaptive controllers for the velocity and altitude subsystems are proposed based on the dynamic surface control method,in which adaptive mechanisms are designed to com-pensate for the model uncertainties.Finally,the proposed ACTCS is simulated in nine different cases of the test flight mission,to verify its effectiveness,robustness and fuel-saving effect.展开更多
This paper develops a novel Neural Network(NN)-based adaptive nonsingular practical predefined-time controller for the hypersonic morphing aircraft subject to actuator faults. Firstly, a novel Lyapunov criterion of pr...This paper develops a novel Neural Network(NN)-based adaptive nonsingular practical predefined-time controller for the hypersonic morphing aircraft subject to actuator faults. Firstly, a novel Lyapunov criterion of practical predefined-time stability is established. Following the proposed criterion, a tangent function based nonsingular predefined-time sliding manifold and the control strategy are developed. Secondly, the radial basis function NN with a low-complexity adaptation mechanism is incorporated into the controller to tackle the actuator faults and uncertainties. Thirdly, rigorous theoretical proof reveals that the attitude tracking errors can converge to a small region around the origin within a predefined time, while all signals in the closed-loop system remain bounded. Finally, numerical simulation results are presented to verify the effectiveness and improved performance of the proposed control scheme.展开更多
This paper reviews the various control algorithms and strategies used for fixed-wing morphing aircraft applications. It is evident from the literature that the development of control algorithms for morphing aircraft t...This paper reviews the various control algorithms and strategies used for fixed-wing morphing aircraft applications. It is evident from the literature that the development of control algorithms for morphing aircraft technologies focused on three main areas. The first area is related to precise control of the shape of morphing concepts for various flight conditions. The second area is mainly related to the flight dynamics, stability, and control aspects of morphing aircraft. The third area deals mainly with aeroelastic control using morphing concepts either for load alleviation purposes and/or to control the instability boundaries. The design of controllers for morphing aircraft/wings is very challenging due to the large changes that can occur in the structural, aerodynamic, and inertial characteristics. In addition, the type of actuation system and actuation rate/speed can have a significant effect on the design of such controllers. The aerospace community is in strong need of such a critical review especially as morphing aircraft technologies move from fundamental research at a low Technology Readiness Level(TRL) to real-life applications. This critical review aims to identify research gaps and propose future directions. In this paper, research activities/papers are categorized according to the control strategy used. This ranges from simple Proportional Integral Derivative(PID) controllers at one end to complex robust adaptive controllers and deep learning algorithms at the other end. This includes analytical, computational, and experimental studies. In addition, the various dynamic models used and their fidelities are highlighted and discussed.展开更多
A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft invo...A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft involves three steps that determine its ability and intelligent:configuration design,dynamic modeling and flight control.This study conducts a comprehensive survey of morphing aircraft.First,the methods to design the configuration of a morphing aircraft are presented and analyzed.Then,the nonlinear dynamic characteristics and aerodynamic interference caused by a morphing wing are described.Subsequently,the dynamic modeling and flight control methods for solving the flight control problems are summarized with respect to these features.Finally,the general as well as special challenges ahead of the development of intelligent morphing aircraft are discussed.The findings can provide a theoretical and technical reference for designing future morphing aircraft or morphing-wing UAVs.展开更多
This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as a...This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as an LPV system, whose scheduling parameter is the variation rate of the wing sweep angle. By dividing the scheduling parameter set into subsets with overlaps, output feedback controllers which consider smooth switching are designed and the controllers in over- lapped subsets are interpolated from two adjacent subsets. A switching law without constraint on the average dwell time is obtained which makes the conclusion less conservative. Furthermore, a systematic algorithm is developed to improve the efficiency of the controllers design process. The parameter set is divided into the fewest subsets on the premise that the closed-loop system has a desired performance. Simulation results demonstrate the effectiveness of this approach.展开更多
This paper develops a robust control methodology for a class of morphing aircraft,which is called innovative control effector（ICE） aircraft.For the ICE morphing aircraft,the distributed arrays of hundreds of shape-c...This paper develops a robust control methodology for a class of morphing aircraft,which is called innovative control effector（ICE） aircraft.For the ICE morphing aircraft,the distributed arrays of hundreds of shape-change devices are employed to stabilize and maneuver the air vehicle.Because the morphing aircraft have the inherent uncertainty and varying dynamics due to the alteration of their configuration,a desired control performance can not be satisfied with a fixed feedback controller.Therefore,a novel control framework including an adaptive flight control law and an adaptive allocation algorithm is proposed.Firstly,a state feedback adaptive control law is designed to guarantee closed-loop stability and state tracking in the presence of uncertain dynamics caused by the wing shape change due to different flight missions.In the control allocation,many distributed arrays are managed in an optimal way to improve the robustness of the system.The scheme is used to an uncertain morphing aircraft model,and the simulation results demonstrate their performance.展开更多
This article investigates gain self-scheduled H 1 robust control system design for a tailless fold- ing-wing morphing aircraft in the wing shape varying process. During the wing morphing phase, the aircraft＇s dynamic...This article investigates gain self-scheduled H 1 robust control system design for a tailless fold- ing-wing morphing aircraft in the wing shape varying process. During the wing morphing phase, the aircraft＇s dynamic response will be governed by time-varying aerodynamic forces and moments. Nonlinear dynamic equations of the morphing aircraft are linearized by using Jacobian linearization approach, and a linear parameter varying （LPV） model of the morphing aircraft in wing folding is obtained. A multi-loop controller for the morphing aircraft is formulated to guarantee stability for the wing shape transition process. The proposed controller uses a set of inner-loop gains to provide stability using classical techniques, whereas a gain self-scheduled H 1 outer-loop controller is devised to guarantee a specific level of robust stability and performance for the time-varying dynamics. The closed-loop simulations show that speed and altitude vary slightly during the whole wing folding process, and they converge rapidly after the process ends. This proves that the gain self-scheduled H 1 robust controller can guarantee a satisfactory dynamic performance for the morphing aircraft during the whole wing shape transition process. Finally, the flight control system＇s robustness for the wing folding process is verified according to uncertainties of the aerodynamic parameters in the nonlinear model.展开更多
This paper deals with the problem of non-fragile linear parameter-varying（LPV） H_∞ control for morphing aircraft with asynchronous switching.The switched LPV model of morphing aircraft is established by Jacobian li...This paper deals with the problem of non-fragile linear parameter-varying（LPV） H_∞ control for morphing aircraft with asynchronous switching.The switched LPV model of morphing aircraft is established by Jacobian linearization approach according to the nonlinear model.The data missing is taken into account in the link from sensors to controllers and the link from controllers to actuators,which satisfies Bernoulli distribution.The non-fragile switched LPV controllers are constructed with consideration of the uncertainties of controllers and asynchronous switching phenomenon.The parameter-dependent Lyapunov functional method and mode-dependent average dwell time（MDADT） method are combined to guarantee the stability and prescribed performance of the system.The sufficient conditions on the solvability of the problem are derived in the form of linear matrix inequalities（LMI）.In order to achieve higher efficiency of the designing process,an algorithm is applied to divide the whole set into subsets automatically.Simulation results are provided to verify the effectiveness and superiority of the method in the paper.展开更多
This paper proposes an adaptive neural control(ANC)method for the coupled nonlinear model of a novel type of embedded surface morphing aircraft which has a tiltable V-tail.A nonlinear model with sixdegrees-of-freedom ...This paper proposes an adaptive neural control(ANC)method for the coupled nonlinear model of a novel type of embedded surface morphing aircraft which has a tiltable V-tail.A nonlinear model with sixdegrees-of-freedom is established.The first-order sliding mode differentiator(FSMD)is applied to the control scheme to avoid the problem of“differential explosion”.Radial basis function neural networks are introduced to estimate the uncertainty and external disturbance of the model,and an ANC controller is proposed based on this design idea.The stability of the proposed ANC controller is proved using Lyapunov theory,and the tracking error of the closed-loop system is semi-globally uniformly bounded.The effectiveness and robustness of the proposed method are verified by numerical simulations and hardware-in-the-loop(HIL)simulations.展开更多
Physical monotonicity is a pervasive phenomenon in the aerodynamic characteristics of aircraft,where the aerodynamic lift consistently increases with the angle of attack within the stalling range.Existing machine lear...Physical monotonicity is a pervasive phenomenon in the aerodynamic characteristics of aircraft,where the aerodynamic lift consistently increases with the angle of attack within the stalling range.Existing machine learning models for aerodynamic predic-tions often overlook this monotonicity,resulting in poor interpretability and credibility.To address this issue,we introduce a monotonic model,the Deep Lattice Network,which integrates the monotonicity constraint of the lift coefficient into machine learn-ing based aerodynamic prediction framework.In this paper,we propose a novel deep learning model,Deep Lattice Cross Network,which aims to rapidly predict aerody-namic forces with high precision while ensuring monotonic constraints.Multi-Task Learning method is utilized to simultaneously predict both lift and drag coefficients,thereby enhancing the efficiency of the model.To optimize the training process and minimize costs,we adopt a unique two-phase deep network training strategy.Based on computational fluid dynamics simulation datasets of a morphing aircraft,the model is trained,and the efficacy of the model is tested by two interpolation and two extrapolation datasets.The results show a remarkable alignment with com-putational fluid dynamics outcomes across all test scenarios.Extended testing across a wider range of attack angles further highlights the superiority of the Deep Lat-tice Cross Network in upholding monotonicity.Incorporating monotonicity constraints not only improves predictive accuracy of the model but also greatly enhances its physi-cal interpretability,which is crucial for advancing the development of more depend-able aerodynamic prediction models.展开更多
Flexible smart sensing skin is a key enabling technology for the future"Fly-by-Feel"control of morphing aircraft.It represents the next-generation skin of aircraft that can exhibit a more powerful sensing fu...Flexible smart sensing skin is a key enabling technology for the future"Fly-by-Feel"control of morphing aircraft.It represents the next-generation skin of aircraft that can exhibit a more powerful sensing function than a conventional one and could be mounted on arbitrary curvilinear surfaces,especially for advanced autonomic,morphing aircraft.Recent significant technical advances in flexible electronics have overcome many historic drawbacks of conventional smart skin,e.g.,only a limited number of discrete block sensors can be integrated due to the inevitable structural damage and heavy guidelines.Herein,we review the key developments in flexible sensors technology and highlight both the state-of-the-art devices and the potential applications for the measurement of aircraft.We begin with the importance of flexible smart skin for morphing aircraft and then expand to the latest progress in various types of flexible sensors.Then we highlight flexible sensors as smart skin to measure aerodynamic parameters and monitor the structural health,and further to achieve the Fly-by-Feel control.Finally,the challenges and opportunities on flexible smart sensing skin are discussed,from the functional design to practical applications.展开更多
Morphing aircraft can adaptively regulate their aerodynamic layout to meet the demands of varying flight conditions,improve their aerodynamic efficiency,and reduce their energy consumption.The design and fabrication o...Morphing aircraft can adaptively regulate their aerodynamic layout to meet the demands of varying flight conditions,improve their aerodynamic efficiency,and reduce their energy consumption.The design and fabrication of high-performance,lightweight,and intelligent morphing structures have become a hot topic in advanced aircraft design.This paper discusses morphing aircraft development history,structural characteristics,existing applications,and future prospects.First,some conventional mechanical morphing aircraft are examined with focus on their morphing modes,mechanisms,advantages,and disadvantages.Second,the novel applications of several technologies for morphing unmanned aerial vehicles,including additive manufacturing for fabricating complex morphing structures,lattice technology for reducing structural weight,and multi-mode morphing combined with flexible skins and foldable structures,are summarized and categorized.Moreover,in consideration of the further development of active morphing aircraft,the paper reviews morphing structures driven by smart material actuators,such as shape memory alloy and macro-fiber composites,and analyzes their advantages and limitations.Third,the paper discusses multiple challenges,including flexible structures,flexible skins,and control systems,in the design of future morphing aircraft.Lastly,the development and application of morphing structures in the aerospace field are discussed to provide a reference for future research and engineering applications.展开更多
This work evaluates the viability of a cutting-edge flexible wing prototype actuated by Shape Memory Alloy(SMA)wire actuators.Such flexible wings have garnered significant interest for their potential to enhance aerod...This work evaluates the viability of a cutting-edge flexible wing prototype actuated by Shape Memory Alloy(SMA)wire actuators.Such flexible wings have garnered significant interest for their potential to enhance aerodynamic efficiency by mitigating noise and delaying flow separation.SMA actuators are particularly advantageous due to their superior power-to-weight ratio and adaptive response,making them increasingly favored in morphing aircraft applications.Our methodology begins with a detailed delineation of the fishbone camber morphing wing rib structure,followed by the construction of a multi-mode morphing wing segment through 3D-printed rib assembly.Comprehensive testing of the SMA wire actuators’actuation capacity and efficiency was conducted to establish their operational parameters.Subsequent experimental analyses focused on the bi-directional and reciprocating morphing performance of the fishbone wing rib,which incorporates SMA wires on the upper and lower sides.These experiments confirmed the segment’s multi-mode morphing abilities.Aerodynamic assessments have demonstrated that our design substantially improves the Lift-to-Drag ratio(L/D)when compared to conventional rigid wings.Finally,two phases of flight tests demonstrated the feasibility of SMA as an aircraft actuator and the validity of flexible wing structures to adjust the aircraft attitude,respectively.展开更多
To investigate the transient aeroelastic responses and flutter characteristics of a variablespan wing during the morphing process,a novel frst-order state-space aeroelastic model is proposed.The time-varying structura...To investigate the transient aeroelastic responses and flutter characteristics of a variablespan wing during the morphing process,a novel frst-order state-space aeroelastic model is proposed.The time-varying structural model of the morphing wing is established based on the Euler-Bernoulli beam theory with time-dependent boundary conditions.A nondimensionalization method is used to translate the time-dependent boundary conditions to be time-independent.The time-domain aerodynamic forces are calculated by the reduced-order unsteady vortex lattice method.The morphing parameters,i.e.,wing span length and morphing speed,are of particular interest for understanding the fundamental aeroelastic behavior of variable-span wings.A test case is proposed and numerical results indicate that the flutter characteristics are sensitive to both of the two morphing parameters.It could be noticed that the aeroelastic characteristics during the wing extracting process are more serious than those during the extending process at the same morphing speed by transient aeroelastic response analysis.In addition,a faster morphing process can get better aeroelastic performance while the mechanism comlexity will arise.展开更多
The high-performance morphing aircraft has become a research focus all over the world.The morphing aircraft,unlike regular unmanned aerial vehicles(UAVs),has more complicated aerodynamic characteristics,making itmore ...The high-performance morphing aircraft has become a research focus all over the world.The morphing aircraft,unlike regular unmanned aerial vehicles(UAVs),has more complicated aerodynamic characteristics,making itmore difficultto conduct its design,model analysis,and experimentation.This paper reviews the recent process and the current status of aeroelastic issues,numerical simulations,and wind tunnel test of morphing aircrafts.The evaluation of aerodynamic characteristics,mechanism,and relevant unsteady dynamic aerodynamicmodeling throughout the morphing process are the primary technological bottlenecks formorphing aircrafts.The unstable aerodynamic forces have a significant impact on the aircraft handling characteristics,control law design,and flight safety.In the past,the structural analysis of morphing aircrafts,flight dynamics modeling,computational mesh morphing technology,and aerodynamic calculation were performed in promoting the development of next generation UAVs,with nonlinear dynamic challenges includingtransonic aeroelastic problems and high angle of attack aeroelastic problems.At present,many facets of these difficulties,together with the accompanying numerical simulation studies,remain under-explored.In addition,wind tunnel experiments face significant challenges in the dynamic morphing process.Finally,dynamic unsteady aerodynamic characteristics in the continuous morphing process still need to be verified by more related experiments.展开更多
The measurement of wing dynamic deformation in morphing aircraft is crucial for achieving closed-loop control and evaluating structural safety.For variable-sweep wings with active large deformation,this paper proposes...The measurement of wing dynamic deformation in morphing aircraft is crucial for achieving closed-loop control and evaluating structural safety.For variable-sweep wings with active large deformation,this paper proposes a novel videogrammetric method for full-field dynamic deformation measurement.A stereo matching method based on epipolar geometry constraint and topological constraint is presented to find the corresponding targets between stereo images.In addition,a new method based on affine transformation combined with adjacent closest point matching is developed,aiming to achieve fast and automatic tracking of targets in time-series images with large deformation.A calculation model for dynamic deformation parameters is established to obtain the displacement,sweep variable angle,and span variation.To verify the proposed method,a dynamic deformation measurement experiment is conducted on a variable-sweep wing model.The results indicate that the actual accuracy of the proposed method is approximately 0.02%of the measured area(e.g.,0.32 mm in a 1.6 m scale).During one morphing course,the sweep variable angle,the span variation and the displacement increase gradually,and then decrease.The maximum sweep variable angle is 36.6°,and the span variation is up to 101.13 mm.The overall configuration of the wing surface is effectively reconstructed under different morphing states.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62103052 and No.52175214)。
文摘This paper presents the design of an asymmetrically variable wingtip anhedral angles morphing aircraft,inspired by biomimetic mechanisms,to enhance lateral maneuver capability.Firstly,we establish a lateral dynamic model considering additional forces and moments resulting during the morphing process,and convert it into a Multiple Input Multiple Output(MIMO)virtual control system by importing virtual inputs.Secondly,a classical dynamics inversion controller is designed for the outer-loop system.A new Global Fast Terminal Incremental Sliding Mode Controller(NDO-GFTISMC)is proposed for the inner-loop system,in which an adaptive law is implemented to weaken control surface chattering,and a Nonlinear Disturbance Observer(NDO)is integrated to compensate for unknown disturbances.The whole control system is proven semiglobally uniformly ultimately bounded based on the multi-Lyapunov function method.Furthermore,we consider tracking errors and self-characteristics of actuators,a quadratic programmingbased dynamic control allocation law is designed,which allocates virtual control inputs to the asymmetrically deformed wingtip and rudder.Actuator dynamic models are incorporated to ensure physical realizability of designed allocation law.Finally,comparative experimental results validate the effectiveness of the designed control system and control allocation law.The NDO-GFTISMC features faster convergence,stronger robustness,and 81.25%and 75.0%reduction in maximum state tracking error under uncertainty compared to the Incremental Nonlinear Dynamic Inversion Controller based on NDO(NDO-INDI)and Incremental Sliding Mode Controller based on NDO(NDO-ISMC),respectively.The design of the morphing aircraft significantly enhances lateral maneuver capability,maintaining a substantial control margin during lateral maneuvering,reducing the burden of the rudder surface,and effectively solving the actuator saturation problem of traditional aircraft during lateral maneuvering.
基金supported by the National Natural Science Foundation of China(No.92741205)。
文摘Fixed-wing long-endurance aircraft play an important role in many fields.However,to reduce drag,these aircraft often have an enormous aspect ratio and wingspan,leading to challenges such as high requirements for takeoff and landing sites and poor wind resistance.Morphing may be able to solve this problem,but conventional morphing aircraft often employ complex actuation mechanisms and actuators to drive the morphing process.The associated costs in terms of structural weight increase and space occupancy are prohibitively high.First,this article develops a high-aspect-ratio aircraft with aerodynamic-driven morphing and validates the rationality and feasibility of this concept through flight tests.Then,focusing on the RQ-4‘‘Global Hawk”as the design baseline,the article explores multidisciplinary overall design methods for the aircraft,analyzing the comprehensive impact of morphing on aerodynamic,structural,and flight control design.Finally,the article elaborates on the benefits and costs associated with aerodynamic-driven morphing.
基金supported by the National Natural Science Foundation of China(No.92741205).
文摘Morphing technology is considered a crucial direction for the future development of aircraft.However,conventional morphing aircraft often employ complex actuation mechanisms and actuators to drive the morphing process.The associated costs in terms of structural weight increase and space occupancy are prohibitively high,even exceeding the benefit of morphing.Especially for high aspect ratio aircraft with large root bending moments,it is very difficult for actuators to directly drive wing deformation.To address this issue,aerodynamic forces generated by control surface deflection can be utilized as an alternative to actuator-driven morphing.This approach reduces the overall cost of morphing while enhancing its benefits.This novel aerodynamic-driven morphing technique imposes new requirements and challenges on the aerodynamic design of aircraft.With a combination of flight experiments and numerical simulations,this article analyzes the variations in aerodynamic forces during the aerodynamic-driven process.Using a high aspect ratio longendurance UAV as the design baseline,the design method of the control surface for aerodynamic-driven morphing is also discussed.
基金supported by the National Natural Science Foundation of China(No.52305262)the Aeronautical Science Foundation of China(No.20230015052002)the Fundamental Research Funds for the Central Universities(No.NT2024001)。
文摘Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.
基金co-supported by the National Natural Science Foundation of China(Nos.62203033,62273024,62073016)the Zhejiang Provincial Natural Science Foundation of China(Nos.LQ23F030020,LZ22F030012)+1 种基金the Defense Industrial Technology Development Program,China(No.JCKY2021601B016)the Equipment Pre-research Key Laboratory Foundation,China(No.JSY6142219202210)。
文摘Inspired by flight biology,morphing flight technology has great potential to improve the adaptability and maneuverability of aircraft.This paper is devoted to the flight control problem of morphing aircraft,and aimed at safe and fuel-saving flight through morphing actively.Specifically,the longitudinal dynamics of a morphing aircraft with telescopic wings is modelled as a strict-feedback nonlinear system.Through fitting the expression of aerodynamic parameters by the mor-phing ratio,the model uncertainties induced by morphing errors are embedded in the dynamics.To meet the safety and fuel-saving requirements,an Adaptive Coordinated Tracking Control Scheme(ACTCS)is then proposed,which consists of a morphing control module and a tracking control module.For the morphing control module,an on-line morphing decision model is given in an optimization process with respect to the morphing ratio,and a second-order tracking filter is introduced to smooth the decision output and ensure the physical realizability.For the tracking control module,the novel adaptive controllers for the velocity and altitude subsystems are proposed based on the dynamic surface control method,in which adaptive mechanisms are designed to com-pensate for the model uncertainties.Finally,the proposed ACTCS is simulated in nine different cases of the test flight mission,to verify its effectiveness,robustness and fuel-saving effect.
基金supported by the National Natural Science Foundation of China (Nos. 52233014, U2241215)。
文摘This paper develops a novel Neural Network(NN)-based adaptive nonsingular practical predefined-time controller for the hypersonic morphing aircraft subject to actuator faults. Firstly, a novel Lyapunov criterion of practical predefined-time stability is established. Following the proposed criterion, a tangent function based nonsingular predefined-time sliding manifold and the control strategy are developed. Secondly, the radial basis function NN with a low-complexity adaptation mechanism is incorporated into the controller to tackle the actuator faults and uncertainties. Thirdly, rigorous theoretical proof reveals that the attitude tracking errors can converge to a small region around the origin within a predefined time, while all signals in the closed-loop system remain bounded. Finally, numerical simulation results are presented to verify the effectiveness and improved performance of the proposed control scheme.
基金funded by Abu Dhabi Education Council Award for Research Excellence Program (AARE 2019) _(No. AARE19-213)by Khalifa University of Science and Technology through Faculty Start-up Award (No. FSU-2020-20)。
文摘This paper reviews the various control algorithms and strategies used for fixed-wing morphing aircraft applications. It is evident from the literature that the development of control algorithms for morphing aircraft technologies focused on three main areas. The first area is related to precise control of the shape of morphing concepts for various flight conditions. The second area is mainly related to the flight dynamics, stability, and control aspects of morphing aircraft. The third area deals mainly with aeroelastic control using morphing concepts either for load alleviation purposes and/or to control the instability boundaries. The design of controllers for morphing aircraft/wings is very challenging due to the large changes that can occur in the structural, aerodynamic, and inertial characteristics. In addition, the type of actuation system and actuation rate/speed can have a significant effect on the design of such controllers. The aerospace community is in strong need of such a critical review especially as morphing aircraft technologies move from fundamental research at a low Technology Readiness Level(TRL) to real-life applications. This critical review aims to identify research gaps and propose future directions. In this paper, research activities/papers are categorized according to the control strategy used. This ranges from simple Proportional Integral Derivative(PID) controllers at one end to complex robust adaptive controllers and deep learning algorithms at the other end. This includes analytical, computational, and experimental studies. In addition, the various dynamic models used and their fidelities are highlighted and discussed.
基金supported by the National Key R&D Program of China(No.2018YFC0810102)the National Natural Science Foundation of China(Nos.91848203 and 91948202)+1 种基金the State Key Laboratory of Robotics(2020-Z02)Natural Science Foundation of Liao Ning Province of China(20180520014)。
文摘A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft involves three steps that determine its ability and intelligent:configuration design,dynamic modeling and flight control.This study conducts a comprehensive survey of morphing aircraft.First,the methods to design the configuration of a morphing aircraft are presented and analyzed.Then,the nonlinear dynamic characteristics and aerodynamic interference caused by a morphing wing are described.Subsequently,the dynamic modeling and flight control methods for solving the flight control problems are summarized with respect to these features.Finally,the general as well as special challenges ahead of the development of intelligent morphing aircraft are discussed.The findings can provide a theoretical and technical reference for designing future morphing aircraft or morphing-wing UAVs.
基金supported by the National Natural Science Foundation of China(Nos.61273083 and 61374012)
文摘This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as an LPV system, whose scheduling parameter is the variation rate of the wing sweep angle. By dividing the scheduling parameter set into subsets with overlaps, output feedback controllers which consider smooth switching are designed and the controllers in over- lapped subsets are interpolated from two adjacent subsets. A switching law without constraint on the average dwell time is obtained which makes the conclusion less conservative. Furthermore, a systematic algorithm is developed to improve the efficiency of the controllers design process. The parameter set is divided into the fewest subsets on the premise that the closed-loop system has a desired performance. Simulation results demonstrate the effectiveness of this approach.
基金supported by the National Natural Science Foundation of China(61074063)
文摘This paper develops a robust control methodology for a class of morphing aircraft,which is called innovative control effector（ICE） aircraft.For the ICE morphing aircraft,the distributed arrays of hundreds of shape-change devices are employed to stabilize and maneuver the air vehicle.Because the morphing aircraft have the inherent uncertainty and varying dynamics due to the alteration of their configuration,a desired control performance can not be satisfied with a fixed feedback controller.Therefore,a novel control framework including an adaptive flight control law and an adaptive allocation algorithm is proposed.Firstly,a state feedback adaptive control law is designed to guarantee closed-loop stability and state tracking in the presence of uncertain dynamics caused by the wing shape change due to different flight missions.In the control allocation,many distributed arrays are managed in an optimal way to improve the robustness of the system.The scheme is used to an uncertain morphing aircraft model,and the simulation results demonstrate their performance.
基金co-supported by China Postdoctoral Science Foundation(Nos.20110490259,2012T50038)
文摘This article investigates gain self-scheduled H 1 robust control system design for a tailless fold- ing-wing morphing aircraft in the wing shape varying process. During the wing morphing phase, the aircraft＇s dynamic response will be governed by time-varying aerodynamic forces and moments. Nonlinear dynamic equations of the morphing aircraft are linearized by using Jacobian linearization approach, and a linear parameter varying （LPV） model of the morphing aircraft in wing folding is obtained. A multi-loop controller for the morphing aircraft is formulated to guarantee stability for the wing shape transition process. The proposed controller uses a set of inner-loop gains to provide stability using classical techniques, whereas a gain self-scheduled H 1 outer-loop controller is devised to guarantee a specific level of robust stability and performance for the time-varying dynamics. The closed-loop simulations show that speed and altitude vary slightly during the whole wing folding process, and they converge rapidly after the process ends. This proves that the gain self-scheduled H 1 robust controller can guarantee a satisfactory dynamic performance for the morphing aircraft during the whole wing shape transition process. Finally, the flight control system＇s robustness for the wing folding process is verified according to uncertainties of the aerodynamic parameters in the nonlinear model.
基金supported by the National Natural Science Foundation of China(Nos.61374012,61273083 and 61403028)
文摘This paper deals with the problem of non-fragile linear parameter-varying（LPV） H_∞ control for morphing aircraft with asynchronous switching.The switched LPV model of morphing aircraft is established by Jacobian linearization approach according to the nonlinear model.The data missing is taken into account in the link from sensors to controllers and the link from controllers to actuators,which satisfies Bernoulli distribution.The non-fragile switched LPV controllers are constructed with consideration of the uncertainties of controllers and asynchronous switching phenomenon.The parameter-dependent Lyapunov functional method and mode-dependent average dwell time（MDADT） method are combined to guarantee the stability and prescribed performance of the system.The sufficient conditions on the solvability of the problem are derived in the form of linear matrix inequalities（LMI）.In order to achieve higher efficiency of the designing process,an algorithm is applied to divide the whole set into subsets automatically.Simulation results are provided to verify the effectiveness and superiority of the method in the paper.
基金funded by the National Natural Science Foundation of China(No.61573286)the Natural Science Foundation of Shaanxi Province(2019JM-163,2020JQ-218)+1 种基金the Fundamental Research Funds for the Central Universities(3102019ZDHKY07)supported by Shaanxi Province Key Laboratory of Flight Control and Simulation Technology。
文摘This paper proposes an adaptive neural control(ANC)method for the coupled nonlinear model of a novel type of embedded surface morphing aircraft which has a tiltable V-tail.A nonlinear model with sixdegrees-of-freedom is established.The first-order sliding mode differentiator(FSMD)is applied to the control scheme to avoid the problem of“differential explosion”.Radial basis function neural networks are introduced to estimate the uncertainty and external disturbance of the model,and an ANC controller is proposed based on this design idea.The stability of the proposed ANC controller is proved using Lyapunov theory,and the tracking error of the closed-loop system is semi-globally uniformly bounded.The effectiveness and robustness of the proposed method are verified by numerical simulations and hardware-in-the-loop(HIL)simulations.
基金supported by the National Natural Science Foundation of China(Grants No.12202384 and No.U2241274)the Defense Industrial Technology Development Program(Grants No.JCKY2023205B013 and No.JCKY2021205B003).
文摘Physical monotonicity is a pervasive phenomenon in the aerodynamic characteristics of aircraft,where the aerodynamic lift consistently increases with the angle of attack within the stalling range.Existing machine learning models for aerodynamic predic-tions often overlook this monotonicity,resulting in poor interpretability and credibility.To address this issue,we introduce a monotonic model,the Deep Lattice Network,which integrates the monotonicity constraint of the lift coefficient into machine learn-ing based aerodynamic prediction framework.In this paper,we propose a novel deep learning model,Deep Lattice Cross Network,which aims to rapidly predict aerody-namic forces with high precision while ensuring monotonic constraints.Multi-Task Learning method is utilized to simultaneously predict both lift and drag coefficients,thereby enhancing the efficiency of the model.To optimize the training process and minimize costs,we adopt a unique two-phase deep network training strategy.Based on computational fluid dynamics simulation datasets of a morphing aircraft,the model is trained,and the efficacy of the model is tested by two interpolation and two extrapolation datasets.The results show a remarkable alignment with com-putational fluid dynamics outcomes across all test scenarios.Extended testing across a wider range of attack angles further highlights the superiority of the Deep Lat-tice Cross Network in upholding monotonicity.Incorporating monotonicity constraints not only improves predictive accuracy of the model but also greatly enhances its physi-cal interpretability,which is crucial for advancing the development of more depend-able aerodynamic prediction models.
基金supported by the National Natural Science Foundation of China(Grant Nos.51925503 and 51635007)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Program for HUST Academic Frontier Youth Team。
文摘Flexible smart sensing skin is a key enabling technology for the future"Fly-by-Feel"control of morphing aircraft.It represents the next-generation skin of aircraft that can exhibit a more powerful sensing function than a conventional one and could be mounted on arbitrary curvilinear surfaces,especially for advanced autonomic,morphing aircraft.Recent significant technical advances in flexible electronics have overcome many historic drawbacks of conventional smart skin,e.g.,only a limited number of discrete block sensors can be integrated due to the inevitable structural damage and heavy guidelines.Herein,we review the key developments in flexible sensors technology and highlight both the state-of-the-art devices and the potential applications for the measurement of aircraft.We begin with the importance of flexible smart skin for morphing aircraft and then expand to the latest progress in various types of flexible sensors.Then we highlight flexible sensors as smart skin to measure aerodynamic parameters and monitor the structural health,and further to achieve the Fly-by-Feel control.Finally,the challenges and opportunities on flexible smart sensing skin are discussed,from the functional design to practical applications.
基金supported by the Key Project of National Natural Science Foundation of China(Grant Nos.92271205,51790171,51735005,and 11620101002).
文摘Morphing aircraft can adaptively regulate their aerodynamic layout to meet the demands of varying flight conditions,improve their aerodynamic efficiency,and reduce their energy consumption.The design and fabrication of high-performance,lightweight,and intelligent morphing structures have become a hot topic in advanced aircraft design.This paper discusses morphing aircraft development history,structural characteristics,existing applications,and future prospects.First,some conventional mechanical morphing aircraft are examined with focus on their morphing modes,mechanisms,advantages,and disadvantages.Second,the novel applications of several technologies for morphing unmanned aerial vehicles,including additive manufacturing for fabricating complex morphing structures,lattice technology for reducing structural weight,and multi-mode morphing combined with flexible skins and foldable structures,are summarized and categorized.Moreover,in consideration of the further development of active morphing aircraft,the paper reviews morphing structures driven by smart material actuators,such as shape memory alloy and macro-fiber composites,and analyzes their advantages and limitations.Third,the paper discusses multiple challenges,including flexible structures,flexible skins,and control systems,in the design of future morphing aircraft.Lastly,the development and application of morphing structures in the aerospace field are discussed to provide a reference for future research and engineering applications.
基金co-supported by the National Key R&D Program of China(No.2022YFB3402200)the National Natural Science Foundation of China(Nos.12372123,12272305 and 12372156)+2 种基金the Key Project of NSFC,China(Nos.92271205,12032018 and 12220101002)the Fundamental Research Funds for the Central Universities of China(No.G2022KY0606)the Basic Research Program of China(No.JCKY2022603C016).
文摘This work evaluates the viability of a cutting-edge flexible wing prototype actuated by Shape Memory Alloy(SMA)wire actuators.Such flexible wings have garnered significant interest for their potential to enhance aerodynamic efficiency by mitigating noise and delaying flow separation.SMA actuators are particularly advantageous due to their superior power-to-weight ratio and adaptive response,making them increasingly favored in morphing aircraft applications.Our methodology begins with a detailed delineation of the fishbone camber morphing wing rib structure,followed by the construction of a multi-mode morphing wing segment through 3D-printed rib assembly.Comprehensive testing of the SMA wire actuators’actuation capacity and efficiency was conducted to establish their operational parameters.Subsequent experimental analyses focused on the bi-directional and reciprocating morphing performance of the fishbone wing rib,which incorporates SMA wires on the upper and lower sides.These experiments confirmed the segment’s multi-mode morphing abilities.Aerodynamic assessments have demonstrated that our design substantially improves the Lift-to-Drag ratio(L/D)when compared to conventional rigid wings.Finally,two phases of flight tests demonstrated the feasibility of SMA as an aircraft actuator and the validity of flexible wing structures to adjust the aircraft attitude,respectively.
基金supported by Defense Industrial Technology Development Program(Nos:A2120110001 and B2120110011)111 Project(No.B07009)the National Natural Science Foundation of China(Nos:90816024 and 10876100)
文摘To investigate the transient aeroelastic responses and flutter characteristics of a variablespan wing during the morphing process,a novel frst-order state-space aeroelastic model is proposed.The time-varying structural model of the morphing wing is established based on the Euler-Bernoulli beam theory with time-dependent boundary conditions.A nondimensionalization method is used to translate the time-dependent boundary conditions to be time-independent.The time-domain aerodynamic forces are calculated by the reduced-order unsteady vortex lattice method.The morphing parameters,i.e.,wing span length and morphing speed,are of particular interest for understanding the fundamental aeroelastic behavior of variable-span wings.A test case is proposed and numerical results indicate that the flutter characteristics are sensitive to both of the two morphing parameters.It could be noticed that the aeroelastic characteristics during the wing extracting process are more serious than those during the extending process at the same morphing speed by transient aeroelastic response analysis.In addition,a faster morphing process can get better aeroelastic performance while the mechanism comlexity will arise.
文摘The high-performance morphing aircraft has become a research focus all over the world.The morphing aircraft,unlike regular unmanned aerial vehicles(UAVs),has more complicated aerodynamic characteristics,making itmore difficultto conduct its design,model analysis,and experimentation.This paper reviews the recent process and the current status of aeroelastic issues,numerical simulations,and wind tunnel test of morphing aircrafts.The evaluation of aerodynamic characteristics,mechanism,and relevant unsteady dynamic aerodynamicmodeling throughout the morphing process are the primary technological bottlenecks formorphing aircrafts.The unstable aerodynamic forces have a significant impact on the aircraft handling characteristics,control law design,and flight safety.In the past,the structural analysis of morphing aircrafts,flight dynamics modeling,computational mesh morphing technology,and aerodynamic calculation were performed in promoting the development of next generation UAVs,with nonlinear dynamic challenges includingtransonic aeroelastic problems and high angle of attack aeroelastic problems.At present,many facets of these difficulties,together with the accompanying numerical simulation studies,remain under-explored.In addition,wind tunnel experiments face significant challenges in the dynamic morphing process.Finally,dynamic unsteady aerodynamic characteristics in the continuous morphing process still need to be verified by more related experiments.
基金supported by the National Natural Science Foundation of China(Grant No.12202282).
文摘The measurement of wing dynamic deformation in morphing aircraft is crucial for achieving closed-loop control and evaluating structural safety.For variable-sweep wings with active large deformation,this paper proposes a novel videogrammetric method for full-field dynamic deformation measurement.A stereo matching method based on epipolar geometry constraint and topological constraint is presented to find the corresponding targets between stereo images.In addition,a new method based on affine transformation combined with adjacent closest point matching is developed,aiming to achieve fast and automatic tracking of targets in time-series images with large deformation.A calculation model for dynamic deformation parameters is established to obtain the displacement,sweep variable angle,and span variation.To verify the proposed method,a dynamic deformation measurement experiment is conducted on a variable-sweep wing model.The results indicate that the actual accuracy of the proposed method is approximately 0.02%of the measured area(e.g.,0.32 mm in a 1.6 m scale).During one morphing course,the sweep variable angle,the span variation and the displacement increase gradually,and then decrease.The maximum sweep variable angle is 36.6°,and the span variation is up to 101.13 mm.The overall configuration of the wing surface is effectively reconstructed under different morphing states.
