Rotating Space Slender Flexible Structures(RSSFS)are extensively utilized in space operations because of their light weight,mobility,and low energy consumption.To realize the accurate space operation of the RSSFS,it i...Rotating Space Slender Flexible Structures(RSSFS)are extensively utilized in space operations because of their light weight,mobility,and low energy consumption.To realize the accurate space operation of the RSSFS,it is necessary to establish a precise mechanical model and develop a control algorithm with high precision.However,with the application of traditional control strategies,the RSSFS often suffers from the chattering phenomenon,which will aggravate structure vibration.In this paper,novel deformation description is put forward to balance modeling accuracy and computational efficiency of the RSSFS,which is better appropriate for real-time control.Besides,the Neural Network Sliding Mode Control(NNSMC)strategy modified by the hyperbolic tangent(tanh)function is put forward to compensate for modeling errors and reduce the chattering phenomenon,thereby improving the trajectory tracking accuracy of the RSSFS.Firstly,a mathematical model for the RSSFS is developed according to the novel deformation description and the vibration theory of flexible structure.Comparison of the deformation accuracy between different models proves that the novel modeling method proposed has high modeling accuracy.Next,the universal approximation property of the Radial Basis Function(RBF)neural network is put forward to determine and compensate for modeling errors,which consist of higher-order modes and the uncertainties of external disturbances.In addition,the tanh function is proposed as the reaching law in the conventional NNSMC strategy to suppress driving torque oscillation.The control law of modified NNSMC strategy and the adaptive law of weight coefficients are developed according to the Lyapunov theorem to guarantee the RSSFS stability.Finally,the simulation and physical experimental tests of the RSSFS with different control strategies are conducted.Experimental results show that the control law according to the novel deformation description and the modified NNSMC strategy can obtain accurate tracking of the rotation and reduce the vibration of the RSSFS simultaneously.展开更多
The multi-body flexible morphing airfoil can improve the aerodynamic characteristics based on different flight missions continuously.Recently researches have focused on the unsteady aerodynamic characteristics of flex...The multi-body flexible morphing airfoil can improve the aerodynamic characteristics based on different flight missions continuously.Recently researches have focused on the unsteady aerodynamic characteristics of flexible wings under passive actuation.However,the unsteady aerodynamic characteristics with the fluid-structure interaction effects in the multi-body active actuation process of morphing airfoil deserve further investigation.In this paper,a fluid-structure coupled simulation method for multi-body flexible morphing airfoil with active actuation subsystem was investigated,and the aerodynamic characteristics during deformation were compared with different skin flexibility,flow field environment,actuation mode and actuation time.The numerical results show that for the steady aerodynamic,the skin flexibility can improve the stability efficiency.In the unsteady process,the change trend of the transient lift coefficient and pitching moment are consistent with those of the active drive characteristics,while the instantaneous lift-drag ratio coefficient is greatly affected by the driving mode and can be improved by increasing the driving duration.展开更多
Appropriate modeling for a controlled plant has been a remarkable problem in the control field. A new modeling theory, i.e. characteristic modeling, is roundly demonstrated. It is deduced in detail that a general line...Appropriate modeling for a controlled plant has been a remarkable problem in the control field. A new modeling theory, i.e. characteristic modeling, is roundly demonstrated. It is deduced in detail that a general linear constant high-order system can be equivalently described with a two-order time-varying difference equation. The application of the characteristic modeling method to the control of flexible structure is also introduced. Especially, as an example, the Hubble Space Telescope is used to illustrate the application of the characteristic modeling and adaptive control method proposed in this paper.展开更多
Although the simple adaptive control （SAC） is widely studied both in theory and application in flexible space structure control and other control problems, it is restricted by the almost strictly positive real （ASP...Although the simple adaptive control （SAC） is widely studied both in theory and application in flexible space structure control and other control problems, it is restricted by the almost strictly positive real （ASPR） conditions. In most practical control problems, the ASPR conditions are not satisfied. Therefore, based on the SAC theory, this paper proposes a backstepping simple adaptive control algorithm which suits the system with arbitrary relative degree with no need of parallel feed forward compensa- tor. The proposed control algorithm consists of decomposition of the arbitrary relative degree system into a known subsystem and an unknown ASPR subsystem which are connected in cascade, design of constant output feedback controller for the known subsystem, and implementation of backstepping method and SAC of the unknown ASPR subsystem. Inheriting the characteristics of the SAC, this method can be adaptive online for the parameter uncertainties. Then, the application of the proposed controller to large flexible space structure with collocated sensors and actuators is studied, and the simulation results validate the proposed controller. It is a new strategy to apply the classical SAC to high relative degree plants.展开更多
Interactions between surface gravity wave and submerged horizontal flexible structures are studied under the assumption of small amplitude water wave theory and structural response. The generalized dispersion relation...Interactions between surface gravity wave and submerged horizontal flexible structures are studied under the assumption of small amplitude water wave theory and structural response. The generalized dispersion relation associated with surface gravity wave interaction with submerged horizontal flexible plate is analyzed to understand the characteristics of the two propagating modes due to the presence of the free surface and submerged horizontal plate. The phase and group velocities are studied in order to analyze the effect of submerged flexible plate on gravity wave motion. The expansion formulae based on Green’s function technique and eigenfunction expansion method using Fourier transform with appropriate orthogonal mode-coupling relation associated with surface gravity wavemaker problems are derived and compared in both the cases of water of finite and infinite depths. The usefulness of the expansion formulae is demonstrated by deriving the solution for surface gravity wave interaction with submerged articulated flexible plate in water of finite depth. Several numerical results on reflection and transmission coefficients related to submerged flexible plate are presented in order to understand the effect of submerged flexible structure on surface wave motion in different cases.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
The composite structure with the dielectric elastomer and soft materials is the main form of theactuators in soft robots. However, the theoretical model is hard to obtain due to the nonlinear large deformationof mater...The composite structure with the dielectric elastomer and soft materials is the main form of theactuators in soft robots. However, the theoretical model is hard to obtain due to the nonlinear large deformationof materials. In this paper, a new composite element model is established based on the absolute nodal coordinateformulation. The consistent deformation conditions at the contact interface between two thin plates are deduced.The hyperelastic constitutive model and the dielectric elastomer constitutive model are introduced for the twothin plates. Then the dynamic model is established to study the dynamic behaviors of the composite flexiblestructure with various parameters. The results show that the nonlinear deformation appears obviously whenthe flexible composite plate structure is driven by various voltages, and the warping deformation becomes moreobvious with the increase of the voltage. The width and thickness of the driven thin plate influence the stabilityof the whole structure. With the decrease of the width or thickness, the deformation of the structure is moreconsistent with obvious periodicity, and the control performance is improved. Finally, the structural parametersof the composite structures are optimized to improve the control performance based on the dynamic performance.Additionally, smaller width and thickness parameters are preferred to obtain better performance in the design offlexible actuator of soft robot.展开更多
The development and rapid usage of numerical codes for fluid-structure interaction(FSI) problems are of great relevance to researchers in many engineering fields such as civil engineering and ocean engineering. This m...The development and rapid usage of numerical codes for fluid-structure interaction(FSI) problems are of great relevance to researchers in many engineering fields such as civil engineering and ocean engineering. This multidisciplinary field known as FSI has been expanded to engineering fields such as offshore structures, tall slender structures and other flexible structures applications. The motivation of this paper is to investigate the numerical model of two-way coupling FSI partitioned flexible plate structure under fluid flow. The adopted partitioned method and approach utilized the advantage of the existing numerical algorithms in solving the two-way coupling fluid and structural interactions. The flexible plate was subjected to a fluid flow which causes large deformation on the fluid domain from the oscillation of the flexible plate. Both fluid and flexible plate are subjected to the interaction of load transfer within two physics by using the strong and weak coupling methods of MFS and Load Transfer Physics Environment, respectively. The oscillation and deformation results have been validated which demonstrate the reliability of both strong and weak method in resolving the two-way coupling problem in contribution of knowledge to the feasibility field study of ocean engineering and civil engineering.展开更多
Two kinds of neuro-fuzzy gust response alleviation control laws are designed for a flexible large-aspect-ratio wing model. Simulations and comparisons of random gust alleviation using the two control laws are performe...Two kinds of neuro-fuzzy gust response alleviation control laws are designed for a flexible large-aspect-ratio wing model. Simulations and comparisons of random gust alleviation using the two control laws are performed. Based on the better neuro-fuzzy control law,experiments and simulations of sinusoidal gust alleviation using one-control-surface control system and two-control-surface control system are developed. The investigations show that the two kinds of neuro-fuzzy gust response alleviation control laws can alleviate random gust responses effectively. The neuro-fuzzy gust response alleviation control law including a modifying factor is better than the other one without it. Further,the better one has good effects on the sinusoidal gust alleviation at different frequencies and flow velocities. The two-control-surface control system has better effects on gust response alleviation than the one-control-surface control system when the gust is strong. The simulation results agree well with the experimental results. These results can be usefully referenced to the design of actual gust alleviation control systems.展开更多
Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are ...Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are derived. The kinetic equation for aerodynamic force coupled with elastic movement is set up, and relevant formulae are derived. The unsteady aerodynamic one in that formulae is revised. The design principle, design process and range of application of such oscillating wing analytical method are elaborated. A flexible structural oscillating wing model is set up, and relevant time response analysis and frequency response analysis are conducted. The analytical results indicate that adopting the new-type driving way for the oscillating wing will not have flutter problems and will be able to produce propulsive force. Furthermore, it will consume much less power than the fixed wing for generating the same lift.展开更多
The hydrogen-bonded organic frameworks(HOFs)as a new type of porous framework materials have been widely studied in various areas.However,the lack of appropriate active sites,low intrinsic conductivity,and poor stabil...The hydrogen-bonded organic frameworks(HOFs)as a new type of porous framework materials have been widely studied in various areas.However,the lack of appropriate active sites,low intrinsic conductivity,and poor stability limited their performance in the field of electrocatalysis.Herein,we designed two 2D metal hydrogen-bonded organic frameworks(2D–M–HOF,M=Cu^(2+)or Ni^(2+))with coordination compounds based on 2,3,6,7,14,15-hexahydroxyl cyclotricatechylene and transition metal ions(Cu^(2+)and Ni^(2+)),respectively.The crystal structure of 2D–Cu–HOF is determined by continuous rotation electron diffraction,indicating an undulated 2D hydrogen-bond network with interlayeredπ-πstacking.The flexible structure of 2D–M–HOF leads to the formation of self-adaption interlayered sites,resulting in superior activity and selectivity in the electrocatalytic conversion of CO_(2) to C_(2) products,achieving a total Faradaic efficiency exceeding 80%due to the high-efficiency C–C coupling.The experimental results and density functional calculations verify that the undulated 2D–M–HOF enables the energetically favorable formation of*OCCHO intermediate.This work provides a promising strategy for designing HOF catalysts in electrocatalysis and related processes.展开更多
Recent developments in micro- and nano-satellites have attracted the interest of the research community worldwide. Many colleges and corporations have launched their satellites in space. Meanwhile, the space flexible ...Recent developments in micro- and nano-satellites have attracted the interest of the research community worldwide. Many colleges and corporations have launched their satellites in space. Meanwhile, the space flexible probe-cone docking system for micro- and nano-satellites has become an attractive topic. In this paper, a dynamic model of a space flexible probe-cone dock- ing system, in which the flexible beam technology is applied, is built based on the Kane method. The curves of impact force versus time are obtained by the Lagrange model, the Kane model, and the experimental method. The Lagrange model was presented in the reference and verified by both finite element simulation and experiment. The results of the three methods show good agreements on the condition that the beam flexibility and the initial relative velocity change. It is worth mentioning that the introduction of vectorial mechanics and analytical mechanics in the Kane method leads to a large reduction of differential operations and makes the modeling process much easier than that of the Lagrange method. Moreover, the influences of the beam flexibility and the initial relative velocity are discussed. It is concluded that the initial relative velocity of space docking operation should be controlled to a certain value in order to protect the docking system.展开更多
This paper is devoted to study the application of the decentralized sliding mode control method, which is used to reduce the vibration of large spacecraft flexible appendage. In the process of control design, the slid...This paper is devoted to study the application of the decentralized sliding mode control method, which is used to reduce the vibration of large spacecraft flexible appendage. In the process of control design, the sliding surface of sliding mode control is determined by minimizing the optimal cost function, and the controller is the saturation controller. The controlled structure is subject to arbitrary, unmeasurable and uncertainty disturbance forces and initial displacement. The decentralized control method and the centralized control method are used to control vibration of the structure respectively. When the system is subjected to the initial displacement or external disturbance, the computer simulation shows that both of these control methods perform effectively, but the number of Riccati equation of the decentralized method is far smaller than that of centralized control method, especially in a large system.展开更多
Unlike traditional manipulators with high rigidity and limited degrees of freedom,pneumatic manipulators have significant superiorities such as flexibility,lightweight and cleanliness,and therefore,have been one of th...Unlike traditional manipulators with high rigidity and limited degrees of freedom,pneumatic manipulators have significant superiorities such as flexibility,lightweight and cleanliness,and therefore,have been one of the most popular research directions in robotics.However,most existing pneumatic manipulators have disadvantages such as low rigidity and simple functionality.In order to make up for the shortcomings of existing pneumatic manipulators,this paper proposes a new pneumatic flexible manipulator inspired by the concept of origami,which realizes the combination and balance of flexibility and rigidity.Finite element analysis is conducted to study influences of the number of airbags,the angle of main beam,and the width of main beam on the performance of the flexible manipulator.The simulation results are utilized to optimize the structure of the flexible manipulator.A pneumatic control system is designed to realize the automatic control of the pneumatic flexible manipulator.At the same time,a prototype is 3D printed,the experimental platform for pneumatic deformation is built,and the verification experiments of the single-jaw manipulator and the three-jaw manipulator are completed.展开更多
As a special type of novel flexible structures, tensegrity holds promise for many potential applications in such fields as materials science, biomechanics, civil and aerospace engineering. Rhombic systems are an impor...As a special type of novel flexible structures, tensegrity holds promise for many potential applications in such fields as materials science, biomechanics, civil and aerospace engineering. Rhombic systems are an important class of tensegrity structures, in which each bar constitutes the longest diagonal of a rhombus of four strings. In this paper, we address the design methods of rhombic structures based on the idea that many tensegrity structures can be constructed by assembling one-bar elementary cells. By analyzing the properties of rhombic cells, we first develop two novel schemes, namely, direct enumeration scheme and cell-substitution scheme. In addition, a facile and efficient method is presented to integrate several rhombic systems into a larger tensegrity structure. To illustrate the applications of these methods, some novel rhombic tensegrity structures are constructed.展开更多
A dual-band flexible frequency selective surface （FSS） with miniaturized elements and maximally flat （Butterworth） response is presented in this paper. It is composed of three metallic layers, which are fabricated...A dual-band flexible frequency selective surface （FSS） with miniaturized elements and maximally flat （Butterworth） response is presented in this paper. It is composed of three metallic layers, which are fabricated on thin flexible polyimide substrates and bonded together using thin bonding films. The overall thickness of the proposed structure is only about 0.3 mm, making it an attractive choice for conformal FSS applications. All the three layers can constitute a miniaturized- element FSS （MEFSS） and produce the first pass-band with miniaturization property, while the up and bottom layers can constitute a symmetric biplanar FSS and produce the second pass-band with maximally fiat （Butterworth） response. The two pass-bands are independent and there is a wide band spacing up to 30 GHz between them. The principles of operation, the simulated results by using the vector modal matching method, and the experimental values of the fabricated prototype are also presented and discussed.展开更多
The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is impl...The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is implemented based on the independent modal control law. Experimental results show that the structural damping of the flexible cantilever beam is effectively improved and an excellent degree of vibration suppression is achieved with the active vibration control strategy.展开更多
Past investigations of the hydrodynamic forces on vertical columns have generally been based on rigid structure assumptions.The effects of structural flexibility and geometry characteristics on the hydrodynamic force ...Past investigations of the hydrodynamic forces on vertical columns have generally been based on rigid structure assumptions.The effects of structural flexibility and geometry characteristics on the hydrodynamic force distribution are not well understood.In this study,fluid-structure interaction models are developed for numerical analyses.This modeling technique is verified with an experimental test in the literature using both circular and rectangular cross-sections.A series of material elasticities that present structural properties ranging from rigid to flexible is then used to conduct analyses.This finding indicates that an increase in structural flexibility can decrease the impact force to some extent,but this effect is limited.A concrete bridge pier with fluid flow impact can be considered rigid when it is fixed at the bottom.After that,the effects of the initial downstream water height and the width of water tank on the hydrodynamic force are thoroughly investigated.The results demonstrate that the increase in the downstream water height with a constant upstream water height corresponds to a decreased force.Moreover,the vertical column results in a blockage effect on the fluid flow.The greater the blockage effect,the higher the hydrodynamic force.The blockage effect from the vertical column can be neglected when the tank width is greater than eight times the structural cross-section diameter.展开更多
Due to the shortage of non-renewable energy in the world, China has started to vigorously develop nuclear power construction in recent years. With the introduction of the concept of "modularization" for plan...Due to the shortage of non-renewable energy in the world, China has started to vigorously develop nuclear power construction in recent years. With the introduction of the concept of "modularization" for plant construction, a single nuclear island is divided into several hundred modules for operation. Due to its particularity, nuclear power has put forward more stringent requirements on hoisting technology. The concept of "integral zero deformation" has greatly increased the difficulty of hoisting, especially for large eccentric flexible structures such as cylinder, the control of deformation is of great significance and far-reaching impact on the docking of adjacent modules. Reasonable hoisting technology is a strong guarantee for subsequent safety construction.展开更多
基金Supported by the Applied Basic Research Program of Liaoning Province,China(No.2023JH2/101300159)the National Natural Science Foundation of China(No.52275090).
文摘Rotating Space Slender Flexible Structures(RSSFS)are extensively utilized in space operations because of their light weight,mobility,and low energy consumption.To realize the accurate space operation of the RSSFS,it is necessary to establish a precise mechanical model and develop a control algorithm with high precision.However,with the application of traditional control strategies,the RSSFS often suffers from the chattering phenomenon,which will aggravate structure vibration.In this paper,novel deformation description is put forward to balance modeling accuracy and computational efficiency of the RSSFS,which is better appropriate for real-time control.Besides,the Neural Network Sliding Mode Control(NNSMC)strategy modified by the hyperbolic tangent(tanh)function is put forward to compensate for modeling errors and reduce the chattering phenomenon,thereby improving the trajectory tracking accuracy of the RSSFS.Firstly,a mathematical model for the RSSFS is developed according to the novel deformation description and the vibration theory of flexible structure.Comparison of the deformation accuracy between different models proves that the novel modeling method proposed has high modeling accuracy.Next,the universal approximation property of the Radial Basis Function(RBF)neural network is put forward to determine and compensate for modeling errors,which consist of higher-order modes and the uncertainties of external disturbances.In addition,the tanh function is proposed as the reaching law in the conventional NNSMC strategy to suppress driving torque oscillation.The control law of modified NNSMC strategy and the adaptive law of weight coefficients are developed according to the Lyapunov theorem to guarantee the RSSFS stability.Finally,the simulation and physical experimental tests of the RSSFS with different control strategies are conducted.Experimental results show that the control law according to the novel deformation description and the modified NNSMC strategy can obtain accurate tracking of the rotation and reduce the vibration of the RSSFS simultaneously.
基金supported by National Natural Science Foundation of China(61125306,91016004)Foundation of Ministry of Education of China(20110092110020,20120092110026)the Post-Doctoral Research Funds(1108000137,3208004602)
基金supported by the National Natural Science Foundation of China(Nos.52192633,11872293)the Natural Science Foundation of Shaanxi Province,China(No.2022JC-03)。
文摘The multi-body flexible morphing airfoil can improve the aerodynamic characteristics based on different flight missions continuously.Recently researches have focused on the unsteady aerodynamic characteristics of flexible wings under passive actuation.However,the unsteady aerodynamic characteristics with the fluid-structure interaction effects in the multi-body active actuation process of morphing airfoil deserve further investigation.In this paper,a fluid-structure coupled simulation method for multi-body flexible morphing airfoil with active actuation subsystem was investigated,and the aerodynamic characteristics during deformation were compared with different skin flexibility,flow field environment,actuation mode and actuation time.The numerical results show that for the steady aerodynamic,the skin flexibility can improve the stability efficiency.In the unsteady process,the change trend of the transient lift coefficient and pitching moment are consistent with those of the active drive characteristics,while the instantaneous lift-drag ratio coefficient is greatly affected by the driving mode and can be improved by increasing the driving duration.
基金This paper was supported by the National Natural Science Foundation of China (Grant No. 60034010) .
文摘Appropriate modeling for a controlled plant has been a remarkable problem in the control field. A new modeling theory, i.e. characteristic modeling, is roundly demonstrated. It is deduced in detail that a general linear constant high-order system can be equivalently described with a two-order time-varying difference equation. The application of the characteristic modeling method to the control of flexible structure is also introduced. Especially, as an example, the Hubble Space Telescope is used to illustrate the application of the characteristic modeling and adaptive control method proposed in this paper.
基金National Natural Science Foundation of China(10902003)
文摘Although the simple adaptive control （SAC） is widely studied both in theory and application in flexible space structure control and other control problems, it is restricted by the almost strictly positive real （ASPR） conditions. In most practical control problems, the ASPR conditions are not satisfied. Therefore, based on the SAC theory, this paper proposes a backstepping simple adaptive control algorithm which suits the system with arbitrary relative degree with no need of parallel feed forward compensa- tor. The proposed control algorithm consists of decomposition of the arbitrary relative degree system into a known subsystem and an unknown ASPR subsystem which are connected in cascade, design of constant output feedback controller for the known subsystem, and implementation of backstepping method and SAC of the unknown ASPR subsystem. Inheriting the characteristics of the SAC, this method can be adaptive online for the parameter uncertainties. Then, the application of the proposed controller to large flexible space structure with collocated sensors and actuators is studied, and the simulation results validate the proposed controller. It is a new strategy to apply the classical SAC to high relative degree plants.
文摘Interactions between surface gravity wave and submerged horizontal flexible structures are studied under the assumption of small amplitude water wave theory and structural response. The generalized dispersion relation associated with surface gravity wave interaction with submerged horizontal flexible plate is analyzed to understand the characteristics of the two propagating modes due to the presence of the free surface and submerged horizontal plate. The phase and group velocities are studied in order to analyze the effect of submerged flexible plate on gravity wave motion. The expansion formulae based on Green’s function technique and eigenfunction expansion method using Fourier transform with appropriate orthogonal mode-coupling relation associated with surface gravity wavemaker problems are derived and compared in both the cases of water of finite and infinite depths. The usefulness of the expansion formulae is demonstrated by deriving the solution for surface gravity wave interaction with submerged articulated flexible plate in water of finite depth. Several numerical results on reflection and transmission coefficients related to submerged flexible plate are presented in order to understand the effect of submerged flexible structure on surface wave motion in different cases.
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the National Natural Science Foundation of China(No.51775345)。
文摘The composite structure with the dielectric elastomer and soft materials is the main form of theactuators in soft robots. However, the theoretical model is hard to obtain due to the nonlinear large deformationof materials. In this paper, a new composite element model is established based on the absolute nodal coordinateformulation. The consistent deformation conditions at the contact interface between two thin plates are deduced.The hyperelastic constitutive model and the dielectric elastomer constitutive model are introduced for the twothin plates. Then the dynamic model is established to study the dynamic behaviors of the composite flexiblestructure with various parameters. The results show that the nonlinear deformation appears obviously whenthe flexible composite plate structure is driven by various voltages, and the warping deformation becomes moreobvious with the increase of the voltage. The width and thickness of the driven thin plate influence the stabilityof the whole structure. With the decrease of the width or thickness, the deformation of the structure is moreconsistent with obvious periodicity, and the control performance is improved. Finally, the structural parametersof the composite structures are optimized to improve the control performance based on the dynamic performance.Additionally, smaller width and thickness parameters are preferred to obtain better performance in the design offlexible actuator of soft robot.
文摘The development and rapid usage of numerical codes for fluid-structure interaction(FSI) problems are of great relevance to researchers in many engineering fields such as civil engineering and ocean engineering. This multidisciplinary field known as FSI has been expanded to engineering fields such as offshore structures, tall slender structures and other flexible structures applications. The motivation of this paper is to investigate the numerical model of two-way coupling FSI partitioned flexible plate structure under fluid flow. The adopted partitioned method and approach utilized the advantage of the existing numerical algorithms in solving the two-way coupling fluid and structural interactions. The flexible plate was subjected to a fluid flow which causes large deformation on the fluid domain from the oscillation of the flexible plate. Both fluid and flexible plate are subjected to the interaction of load transfer within two physics by using the strong and weak coupling methods of MFS and Load Transfer Physics Environment, respectively. The oscillation and deformation results have been validated which demonstrate the reliability of both strong and weak method in resolving the two-way coupling problem in contribution of knowledge to the feasibility field study of ocean engineering and civil engineering.
基金National Natural Science Foundation of China(90716006)
文摘Two kinds of neuro-fuzzy gust response alleviation control laws are designed for a flexible large-aspect-ratio wing model. Simulations and comparisons of random gust alleviation using the two control laws are performed. Based on the better neuro-fuzzy control law,experiments and simulations of sinusoidal gust alleviation using one-control-surface control system and two-control-surface control system are developed. The investigations show that the two kinds of neuro-fuzzy gust response alleviation control laws can alleviate random gust responses effectively. The neuro-fuzzy gust response alleviation control law including a modifying factor is better than the other one without it. Further,the better one has good effects on the sinusoidal gust alleviation at different frequencies and flow velocities. The two-control-surface control system has better effects on gust response alleviation than the one-control-surface control system when the gust is strong. The simulation results agree well with the experimental results. These results can be usefully referenced to the design of actual gust alleviation control systems.
基金National Natural Science Foundation of China(10432040, 90716006)
文摘Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are derived. The kinetic equation for aerodynamic force coupled with elastic movement is set up, and relevant formulae are derived. The unsteady aerodynamic one in that formulae is revised. The design principle, design process and range of application of such oscillating wing analytical method are elaborated. A flexible structural oscillating wing model is set up, and relevant time response analysis and frequency response analysis are conducted. The analytical results indicate that adopting the new-type driving way for the oscillating wing will not have flutter problems and will be able to produce propulsive force. Furthermore, it will consume much less power than the fixed wing for generating the same lift.
基金financially supported by the National Natural Science Foundation of China(nos.21971012,61933002,21601015,21625102,21674012,and 81601549)the National Key Research and Development Program of China(2020YFB1506300)Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘The hydrogen-bonded organic frameworks(HOFs)as a new type of porous framework materials have been widely studied in various areas.However,the lack of appropriate active sites,low intrinsic conductivity,and poor stability limited their performance in the field of electrocatalysis.Herein,we designed two 2D metal hydrogen-bonded organic frameworks(2D–M–HOF,M=Cu^(2+)or Ni^(2+))with coordination compounds based on 2,3,6,7,14,15-hexahydroxyl cyclotricatechylene and transition metal ions(Cu^(2+)and Ni^(2+)),respectively.The crystal structure of 2D–Cu–HOF is determined by continuous rotation electron diffraction,indicating an undulated 2D hydrogen-bond network with interlayeredπ-πstacking.The flexible structure of 2D–M–HOF leads to the formation of self-adaption interlayered sites,resulting in superior activity and selectivity in the electrocatalytic conversion of CO_(2) to C_(2) products,achieving a total Faradaic efficiency exceeding 80%due to the high-efficiency C–C coupling.The experimental results and density functional calculations verify that the undulated 2D–M–HOF enables the energetically favorable formation of*OCCHO intermediate.This work provides a promising strategy for designing HOF catalysts in electrocatalysis and related processes.
基金supported in part by the National Natural Science Foundation of China (Nos. 91216201, 51205403)
文摘Recent developments in micro- and nano-satellites have attracted the interest of the research community worldwide. Many colleges and corporations have launched their satellites in space. Meanwhile, the space flexible probe-cone docking system for micro- and nano-satellites has become an attractive topic. In this paper, a dynamic model of a space flexible probe-cone dock- ing system, in which the flexible beam technology is applied, is built based on the Kane method. The curves of impact force versus time are obtained by the Lagrange model, the Kane model, and the experimental method. The Lagrange model was presented in the reference and verified by both finite element simulation and experiment. The results of the three methods show good agreements on the condition that the beam flexibility and the initial relative velocity change. It is worth mentioning that the introduction of vectorial mechanics and analytical mechanics in the Kane method leads to a large reduction of differential operations and makes the modeling process much easier than that of the Lagrange method. Moreover, the influences of the beam flexibility and the initial relative velocity are discussed. It is concluded that the initial relative velocity of space docking operation should be controlled to a certain value in order to protect the docking system.
文摘This paper is devoted to study the application of the decentralized sliding mode control method, which is used to reduce the vibration of large spacecraft flexible appendage. In the process of control design, the sliding surface of sliding mode control is determined by minimizing the optimal cost function, and the controller is the saturation controller. The controlled structure is subject to arbitrary, unmeasurable and uncertainty disturbance forces and initial displacement. The decentralized control method and the centralized control method are used to control vibration of the structure respectively. When the system is subjected to the initial displacement or external disturbance, the computer simulation shows that both of these control methods perform effectively, but the number of Riccati equation of the decentralized method is far smaller than that of centralized control method, especially in a large system.
基金National Natural Science Foundation of China(12002032).
文摘Unlike traditional manipulators with high rigidity and limited degrees of freedom,pneumatic manipulators have significant superiorities such as flexibility,lightweight and cleanliness,and therefore,have been one of the most popular research directions in robotics.However,most existing pneumatic manipulators have disadvantages such as low rigidity and simple functionality.In order to make up for the shortcomings of existing pneumatic manipulators,this paper proposes a new pneumatic flexible manipulator inspired by the concept of origami,which realizes the combination and balance of flexibility and rigidity.Finite element analysis is conducted to study influences of the number of airbags,the angle of main beam,and the width of main beam on the performance of the flexible manipulator.The simulation results are utilized to optimize the structure of the flexible manipulator.A pneumatic control system is designed to realize the automatic control of the pneumatic flexible manipulator.At the same time,a prototype is 3D printed,the experimental platform for pneumatic deformation is built,and the verification experiments of the single-jaw manipulator and the three-jaw manipulator are completed.
基金supported by the National Natural Science Foundation of China (10732050)Tsinghua University (2009THZ02122)the National Basic Research Program of China (973) (2010CB631005)
文摘As a special type of novel flexible structures, tensegrity holds promise for many potential applications in such fields as materials science, biomechanics, civil and aerospace engineering. Rhombic systems are an important class of tensegrity structures, in which each bar constitutes the longest diagonal of a rhombus of four strings. In this paper, we address the design methods of rhombic structures based on the idea that many tensegrity structures can be constructed by assembling one-bar elementary cells. By analyzing the properties of rhombic cells, we first develop two novel schemes, namely, direct enumeration scheme and cell-substitution scheme. In addition, a facile and efficient method is presented to integrate several rhombic systems into a larger tensegrity structure. To illustrate the applications of these methods, some novel rhombic tensegrity structures are constructed.
基金Project supported by the Third Innovation Fund of Changchun Institute of Optics and Fine Mechanics and Physics(Grant No.093Y32J090)
文摘A dual-band flexible frequency selective surface （FSS） with miniaturized elements and maximally flat （Butterworth） response is presented in this paper. It is composed of three metallic layers, which are fabricated on thin flexible polyimide substrates and bonded together using thin bonding films. The overall thickness of the proposed structure is only about 0.3 mm, making it an attractive choice for conformal FSS applications. All the three layers can constitute a miniaturized- element FSS （MEFSS） and produce the first pass-band with miniaturization property, while the up and bottom layers can constitute a symmetric biplanar FSS and produce the second pass-band with maximally fiat （Butterworth） response. The two pass-bands are independent and there is a wide band spacing up to 30 GHz between them. The principles of operation, the simulated results by using the vector modal matching method, and the experimental values of the fabricated prototype are also presented and discussed.
基金Supported by the National Natural Science Foundation of China (11172026)
文摘The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is implemented based on the independent modal control law. Experimental results show that the structural damping of the flexible cantilever beam is effectively improved and an excellent degree of vibration suppression is achieved with the active vibration control strategy.
基金The National Natural Science Foundation of China(No.52222804,U21A20154).
文摘Past investigations of the hydrodynamic forces on vertical columns have generally been based on rigid structure assumptions.The effects of structural flexibility and geometry characteristics on the hydrodynamic force distribution are not well understood.In this study,fluid-structure interaction models are developed for numerical analyses.This modeling technique is verified with an experimental test in the literature using both circular and rectangular cross-sections.A series of material elasticities that present structural properties ranging from rigid to flexible is then used to conduct analyses.This finding indicates that an increase in structural flexibility can decrease the impact force to some extent,but this effect is limited.A concrete bridge pier with fluid flow impact can be considered rigid when it is fixed at the bottom.After that,the effects of the initial downstream water height and the width of water tank on the hydrodynamic force are thoroughly investigated.The results demonstrate that the increase in the downstream water height with a constant upstream water height corresponds to a decreased force.Moreover,the vertical column results in a blockage effect on the fluid flow.The greater the blockage effect,the higher the hydrodynamic force.The blockage effect from the vertical column can be neglected when the tank width is greater than eight times the structural cross-section diameter.
文摘Due to the shortage of non-renewable energy in the world, China has started to vigorously develop nuclear power construction in recent years. With the introduction of the concept of "modularization" for plant construction, a single nuclear island is divided into several hundred modules for operation. Due to its particularity, nuclear power has put forward more stringent requirements on hoisting technology. The concept of "integral zero deformation" has greatly increased the difficulty of hoisting, especially for large eccentric flexible structures such as cylinder, the control of deformation is of great significance and far-reaching impact on the docking of adjacent modules. Reasonable hoisting technology is a strong guarantee for subsequent safety construction.
