Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potentia...Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potential reduction in controller dependency by utilizing soft pneumatic oscillators,challenges such as low flow rates,complex manufacturing processes,and lack of adjustment ability persist.Inspired by the geckos'spine,we propose a Spinal Bistable Oscillator(SBO)that operates without discrete components or electronic control hardware,achieving stable oscillatory motion under constant air pressure.This oscillator employs a soft control valve and lagging pin,which can switch the direction of airflow conduction based on the oscillation angle of the spine.Different types of actuators can be controlled using a series connection.In this study,the effective working range of the soft control valve,influence of the spring pretension force on the torque during oscillation,and effect of different throttle tube lengths on the oscillation frequency were investigated.Furthermore,a self-crawling robot was developed.Experimental results demonstrate that the robot can crawl at speeds ranging from 3.6 to 5.7 mm/s(or 3.1 to 4.9 body length/min)and overcome its own gravity(with a weight of 165 g)to climb vertically.The SBO proposed in this study exhibits characteristics of lightweight,low cost,high oscillation torque,and tunable frequency.It holds promise for application in joint control of future pneumatic soft robots.展开更多
The snap-through behaviors and nonlinear vibrations are investigated for a bistable composite laminated cantilever shell subjected to transversal foundation excitation based on experimental and theoretical approaches....The snap-through behaviors and nonlinear vibrations are investigated for a bistable composite laminated cantilever shell subjected to transversal foundation excitation based on experimental and theoretical approaches.An improved experimental specimen is designed in order to satisfy the cantilever support boundary condition,which is composed of an asymmetric region and a symmetric region.The symmetric region of the experimental specimen is entirely clamped,which is rigidly connected to an electromagnetic shaker,while the asymmetric region remains free of constraint.Different motion paths are realized for the bistable cantilever shell by changing the input signal levels of the electromagnetic shaker,and the displacement responses of the shell are collected by the laser displacement sensors.The numerical simulation is conducted based on the established theoretical model of the bistable composite laminated cantilever shell,and an off-axis three-dimensional dynamic snap-through domain is obtained.The numerical solutions are in good agreement with the experimental results.The nonlinear stiffness characteristics,dynamic snap-through domain,and chaos and bifurcation behaviors of the shell are quantitatively analyzed.Due to the asymmetry of the boundary condition and the shell,the upper stable-state of the shell exhibits an obvious soft spring stiffness characteristic,and the lower stable-state shows a linear stiffness characteristic of the shell.展开更多
Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of ...Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.展开更多
Bistate plates have found extensive applications in the domains of smart structures and energy harvesting devices.Most bistable curved plates are characterized by a constant thickness profile.Regrettably,due to the in...Bistate plates have found extensive applications in the domains of smart structures and energy harvesting devices.Most bistable curved plates are characterized by a constant thickness profile.Regrettably,due to the inherent complexity of this problem,relatively little attention has been devoted to this area.In this study,we demonstrate how deep learning can facilitate the discovery of novel plate profiles that cater to multiple objectives,including maximizing stiffness,forward snapping force,and backward snapping force.Our proposed approach is distinguished by its efficiency in terms of low computational energy consumption and high effectiveness.It holds promise for future applications in the design and optimization of multistable structures with diverse objectives,addressing the requirements of various fields.展开更多
This study presents a numerical investigation into the equilibrium shapes and snapthrough response of an innovative bistable symmetric composite wing.The proposed design is a compound plate that consists of a symmetri...This study presents a numerical investigation into the equilibrium shapes and snapthrough response of an innovative bistable symmetric composite wing.The proposed design is a compound plate that consists of a symmetric flat platform followed by a winglet that utilizes the modified hybrid bistable symmetric laminate recently developed in the reference.The hybrid layup of the winglet resolves the issue of losing the bistability of the unsymmetric laminate when attached to another structure.An approximate analytical model based on the Rayleigh-Ritz method is developed for the compound plate that considers the geometric nonlinearity,the clamping conditions at the wing root,and the compatibility conditions at the interface.The static equilibrium positions predicted by the model were verified against the ABAQUS finite element(FE)results and an excellent agreement was obtained.The influence of the geometrical and material parameters of the proposed design on the static equilibrium shapes and the snapthrough response was examined.The following parameters were considered:the length ratio of the flat plate to the bistable winglet,the thickness and location of the bidirectional glass epoxy layers,the load location,and the wing’s taperness and aspect ratio.All parameters were found significant,and their effects were discussed.The novelty of this work is that it presents the equilibrium shapes and the snapthrough response of a bistable laminate as a part of a bigger compliant structure,which mimics the scenario in real-life applications.展开更多
The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relations...The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relationship between two order vibration modes of the system is verified.The resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales method.The Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are analyzed.The discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance responses.The numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the system.Furthermore,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare maps.Finally,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.展开更多
The chaotic dynamic snap-through and complex nonlinear vibrations are investigated in a rectangular asymmetric cross-ply bistable composite laminated cantilever shell,in cases of 1:2 inter-well internal resonance and ...The chaotic dynamic snap-through and complex nonlinear vibrations are investigated in a rectangular asymmetric cross-ply bistable composite laminated cantilever shell,in cases of 1:2 inter-well internal resonance and primary resonance.The transverse foundation excitation is applied to the fixed end of the structure,and the other end is in a free state.The first-order approximate multiple scales method is employed to perform the perturbation analysis on the dimensionless two-degree-of-freedom ordinary differential motion control equation.The four-dimensional averaged equations are derived in both polar and rectangular coordinate forms.Deriving from the obtained frequency-amplitude and force-amplitude response curves,a detailed analysis is conducted to examine the impacts of excitation amplitude,damping coefficient,and tuning parameter on the nonlinear internal resonance characteristics of the system.The nonlinear softening characteristic is exhibited in the upper stable-state,while the lower stable-state demonstrates the softening and linearity characteristics.Numerical simulation is carried out using the fourth-order Runge-Kutta method,and a series of nonlinear response curves are plotted.Increasing the excitation amplitude further elucidates the global bifurcation and chaotic dynamic snap-through characteristics of the bistable cantilever shell.展开更多
Weak signal reception is a very important and challenging problem for communication systems especially in the presence of non-Gaussian noise,and in which case the performance of optimal linear correlated receiver degr...Weak signal reception is a very important and challenging problem for communication systems especially in the presence of non-Gaussian noise,and in which case the performance of optimal linear correlated receiver degrades dramatically.Aiming at this,a novel uncorrelated reception scheme based on adaptive bistable stochastic resonance(ABSR)for a weak signal in additive Laplacian noise is investigated.By analyzing the key issue that the quantitative cooperative resonance matching relationship between the characteristics of the noisy signal and the nonlinear bistable system,an analytical expression of the bistable system parameters is derived.On this basis,by means of bistable system parameters self-adaptive adjustment,the counterintuitive stochastic resonance(SR)phenomenon can be easily generated at which the random noise is changed into a benefit to assist signal transmission.Finally,it is demonstrated that approximately 8dB bit error ratio(BER)performance improvement for the ABSR-based uncorrelated receiver when compared with the traditional uncorrelated receiver at low signal to noise ratio(SNR)conditions varying from-30dB to-5dB.展开更多
Bistable curved shells have become a promising low-cost application in energy absorption fields owing to recentadvances in material and technology.Significant research has been conducted to improve their energy absorp...Bistable curved shells have become a promising low-cost application in energy absorption fields owing to recentadvances in material and technology.Significant research has been conducted to improve their energy absorptioneffect through forward prediction and single-objective optimization.However,these approaches may not fully explore their functional potential.In this study,we propose a multi-objective optimization framework based on theprinciple of main objective optimization that combines neural networks and genetic algorithms.The energy absorption effect and backward snapping force of the bistable curved shell are improved synchronously.Meanwhile,a reverse design algorithm is developed to generate the preset load-displacement curve,which further expandsthe application of machine learning methods in the field of multi-objective optimization.The combination ofmachine learning and multi-objective optimization is highly effective for building meta-structures with specificperformance requirements and has potential applications in solving complex optimization tasks in various fields.展开更多
Smart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices.Smart bistable coordination complexes are a class of functional comp...Smart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices.Smart bistable coordination complexes are a class of functional complexes which have two stable states that can be reversibly switched in response to external stimuli.Such bistable molecules play a vital role in various applications,such as sensors,data storage,spintronics,smart windows,optical switches,information encryption and decryption,displays,actuators,etc.Herein,the recent research studies into the development of these smart bistable metal coordination complexes are reviewed.According to the different external stimuli,these smart bistable coordination systems have been classified and summarized,including light-responsive systems,thermally-responsive systems,electrically-responsive systems,mechanicallyresponsive systems,and some other cases.These systems are further subdivided according to the changes in signals(e.g.,color,fluorescence,spin state,crystalline phase)under external stimuli.The design principles of each type of smart bistable metal complexes as well as their broad and innovative applications are comprehensively described.Finally,the challenges and opportunities in this field are briefly analyzed and discussed.展开更多
This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting eff...This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.展开更多
The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a...The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a Ti/AgTCNQ/Ati crossbar structure array as organic bistable devices （OBD）.A reversible and reproducible memory switching property,caused by intermolecular charge transfer （CT） in the AgTCNQ thin-film, was observed in the organic bista- ble devices. The positive threshold voltage from the high impedance state to the low impedance was about 3.8-5V, with the reverse phenomenon occurring at a negative voltage of - 3.5- - 4. 4V,lower than that with a CuTCNQ active layer. The crossbar array of OBDs with AgTCNQ is promising for nonvolatile organic memory applications.展开更多
This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates ...This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.展开更多
In this paper we present the control and synchronization of a coupled Bragg acousto-optic bistable map system using nonlinear feedback technology. This nonlinear feedback technology is useful to control a temporally c...In this paper we present the control and synchronization of a coupled Bragg acousto-optic bistable map system using nonlinear feedback technology. This nonlinear feedback technology is useful to control a temporally chaotic system as well as a spatiotemporally chaotic system. It can be extended to synchronize the spatiotemporal chaos. It can work in a wide range of the controlled and synchronized signals, so it can decrease the sensitivity down to a noise level. The synchronization can be obtained by the analysis of the largest conditional Lyapunov exponent spectrum, and easily implemented in practical systems just by adjusting the coupled strength without any pre-knowledge of the dynamic system required.展开更多
By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by ...By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by the second order Melnikov function. Secondly, the effects of each item in chaos threshold expression are analyzed. The excitation frequency and resistance values, which have the most influence on chaos threshold value, are found. The result from the second order Melnikov function is more accurate compared with that from the first order Melnikov function. Finally, the attraction basins of large amplitude motions under different exciting frequency, exciting amplitude, and resistance parameters are given.展开更多
Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and e...Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and expensive computations.In this work,we present a method to easily and rapidly design bistable buckled beams subjected to a transverse point force.Based on the Euler–Bernoulli beam theory,we establish a theoretical model of bistable buckled beams to characterize their snapthrough properties.This model is verified against the results from a finite element analysis(FEA)model,with maximum discrepancy less than 7%.By analyzing and simplifying our theoretical model,we derive explicit analytical expressions for critical behavioral values on the force-displacement curve of the beam.These behavioral values include critical force,critical displacement,and travel,which are generally sufficient for characterizing the snapthrough properties of a bistable buckled beam.Based on these analytical formulas,we investigate the influence of a bistable buckled beam's key design parameters,including its actuation position and precompression,on its critical behavioral values,with our results validated by FEA simulations.Our analytical method enables fast and computationally inexpensive design of bistable buckled beams and can guide the design of complicated systems that incorporate bistable mechanisms.展开更多
This paper investigates the stochastic resonance in a time-delayed bistable system subjected to multiplicative and additive white noise and asymmetric dichotomous noise. Under the adiabatic approximation condition, th...This paper investigates the stochastic resonance in a time-delayed bistable system subjected to multiplicative and additive white noise and asymmetric dichotomous noise. Under the adiabatic approximation condition, the expression of the signal-to-noise ratio （SNR） is obtained. It finds that the SNR is a non-monotonic function of the delayed times, of the amplitude of the driving square-wave signal, as well as of the asymmetry of the dichotomous noise. In addition, the SNR varies non-monotonously with the intensities of the multiplicative and additive noise as well as the system parameters. Moreover, the SNR depends non-monotonically on the correlate rate of the dichotomous noise.展开更多
As two crucial indicators of bistable energy harvesting performance,band width and power amplitude are simultaneously investigated for obtaining the synergy effect.Toward this goal,a nonlinear electromechanical-couple...As two crucial indicators of bistable energy harvesting performance,band width and power amplitude are simultaneously investigated for obtaining the synergy effect.Toward this goal,a nonlinear electromechanical-coupled distributed-parameter model of the bistable piezoelectric energy harvester is established.Based on the electromechanical decoupled method,approximate higher-order analytical solutions of the beam displacement,harvested power and effective bandwidth are derived.The cubic-function discriminant of the analytical solution is introduced to determine the nonlinear excitation-frequency boundaries of multiple solutions and power peak.The stability of the multiple solutions is analyzed through Jacobi matrix of the modulation equation.Superharmonic resonance is notified.Upward and downward sweep experiments and numerical solutions of time history curves,phase portraits and power spectra confirm the analytical findings.To realize optimized broadband energy harvesting,the parametric study on the coefficients of the linear and cubic elastic external forces with the corresponding optimal load resistance is performed.For the nonlinear hardening case,more positive linear coefficient is preferred.For the nonlinear softening case,the cubic coefficient slightly larger than its optimal value is recommended at each given linear coefficient.By tuning the load resistance and linear and cubic coefficients of the external force,broadband bistable energy harvesting with optimized power is realized.展开更多
Stochastic resonance（SR） is studied in an under-damped bistable system driven by the harmonic mixing signal and Gaussian white noise. Using the linear response theory（LRT）, the expressions of the spectral amplific...Stochastic resonance（SR） is studied in an under-damped bistable system driven by the harmonic mixing signal and Gaussian white noise. Using the linear response theory（LRT）, the expressions of the spectral amplification at fundamental and higher-order harmonic are obtained. The effects of damping coefficient, noise intensity, signal amplitude, and frequency on spectral amplifications are explored. Meanwhile, the power spectral density（PSD） and signal-to-noise ratio（SNR） are calculated to quantify SR and verify the theoretical results. The SNRs at the first and second harmonics exhibit a minimum first and a maximum later with increasing noise intensity. That is, both of the noise-induced suppression and resonance can be observed by choosing proper system parameters. Especially, when the ratio of the second harmonic amplitude to the fundamental one takes a large value, the SNR at the fundamental harmonic is a monotonic function of noise intensity and the SR phenomenon disappears.展开更多
The steady-state properties of a bistable system are investigated when both the multiplicative noise and the coupling between additive and multiplicative noises are coloured with different values of noise correlation ...The steady-state properties of a bistable system are investigated when both the multiplicative noise and the coupling between additive and multiplicative noises are coloured with different values of noise correlation times T1 and T2. After introducing a dimensionless parameter R（R = α/D, D is the intensity of the multiplicative noise and a is the intensity of the additive noise）, and performing the numerical computations, we find the following points： （1） For the case of R 〉 1, A （the intensity of correlation between additive and multiplicative noises）, T1 and T2 can induce the stationary probability distribution （SPD） transition from bimodal to unimodal in structure, but for the cases of R _〈 1, the bimodal structure is preserved; （2） a can also induce the SPD transition from bimodal to unimodal in structure; （3） the bimodal structure of the SPD exhibits a symmetrical structure as D increases.展开更多
基金supported by Sichuan Provincial Department of Science and Technology Key Research and Development Program in High-Tech Fields(2022YFG0240).
文摘Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potential reduction in controller dependency by utilizing soft pneumatic oscillators,challenges such as low flow rates,complex manufacturing processes,and lack of adjustment ability persist.Inspired by the geckos'spine,we propose a Spinal Bistable Oscillator(SBO)that operates without discrete components or electronic control hardware,achieving stable oscillatory motion under constant air pressure.This oscillator employs a soft control valve and lagging pin,which can switch the direction of airflow conduction based on the oscillation angle of the spine.Different types of actuators can be controlled using a series connection.In this study,the effective working range of the soft control valve,influence of the spring pretension force on the torque during oscillation,and effect of different throttle tube lengths on the oscillation frequency were investigated.Furthermore,a self-crawling robot was developed.Experimental results demonstrate that the robot can crawl at speeds ranging from 3.6 to 5.7 mm/s(or 3.1 to 4.9 body length/min)and overcome its own gravity(with a weight of 165 g)to climb vertically.The SBO proposed in this study exhibits characteristics of lightweight,low cost,high oscillation torque,and tunable frequency.It holds promise for application in joint control of future pneumatic soft robots.
基金Project supported by the National Natural Science Foundation of China(Nos.11832002 and 12072201)。
文摘The snap-through behaviors and nonlinear vibrations are investigated for a bistable composite laminated cantilever shell subjected to transversal foundation excitation based on experimental and theoretical approaches.An improved experimental specimen is designed in order to satisfy the cantilever support boundary condition,which is composed of an asymmetric region and a symmetric region.The symmetric region of the experimental specimen is entirely clamped,which is rigidly connected to an electromagnetic shaker,while the asymmetric region remains free of constraint.Different motion paths are realized for the bistable cantilever shell by changing the input signal levels of the electromagnetic shaker,and the displacement responses of the shell are collected by the laser displacement sensors.The numerical simulation is conducted based on the established theoretical model of the bistable composite laminated cantilever shell,and an off-axis three-dimensional dynamic snap-through domain is obtained.The numerical solutions are in good agreement with the experimental results.The nonlinear stiffness characteristics,dynamic snap-through domain,and chaos and bifurcation behaviors of the shell are quantitatively analyzed.Due to the asymmetry of the boundary condition and the shell,the upper stable-state of the shell exhibits an obvious soft spring stiffness characteristic,and the lower stable-state shows a linear stiffness characteristic of the shell.
基金supported by the National Natural Science Foundation of China(No.52275231)the National Defense Basic Scientific Research Program of China(No.JCKY2019205C002).
文摘Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.
文摘Bistate plates have found extensive applications in the domains of smart structures and energy harvesting devices.Most bistable curved plates are characterized by a constant thickness profile.Regrettably,due to the inherent complexity of this problem,relatively little attention has been devoted to this area.In this study,we demonstrate how deep learning can facilitate the discovery of novel plate profiles that cater to multiple objectives,including maximizing stiffness,forward snapping force,and backward snapping force.Our proposed approach is distinguished by its efficiency in terms of low computational energy consumption and high effectiveness.It holds promise for future applications in the design and optimization of multistable structures with diverse objectives,addressing the requirements of various fields.
基金supported by the Project of American University of Sharjah(Grant No.FRG21-M-E92).
文摘This study presents a numerical investigation into the equilibrium shapes and snapthrough response of an innovative bistable symmetric composite wing.The proposed design is a compound plate that consists of a symmetric flat platform followed by a winglet that utilizes the modified hybrid bistable symmetric laminate recently developed in the reference.The hybrid layup of the winglet resolves the issue of losing the bistability of the unsymmetric laminate when attached to another structure.An approximate analytical model based on the Rayleigh-Ritz method is developed for the compound plate that considers the geometric nonlinearity,the clamping conditions at the wing root,and the compatibility conditions at the interface.The static equilibrium positions predicted by the model were verified against the ABAQUS finite element(FE)results and an excellent agreement was obtained.The influence of the geometrical and material parameters of the proposed design on the static equilibrium shapes and the snapthrough response was examined.The following parameters were considered:the length ratio of the flat plate to the bistable winglet,the thickness and location of the bidirectional glass epoxy layers,the load location,and the wing’s taperness and aspect ratio.All parameters were found significant,and their effects were discussed.The novelty of this work is that it presents the equilibrium shapes and the snapthrough response of a bistable laminate as a part of a bigger compliant structure,which mimics the scenario in real-life applications.
基金Project supported by the National Natural Science Foundation of China(Nos.12293000,12293001,11988102,12172006,and 12202011)。
文摘The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relationship between two order vibration modes of the system is verified.The resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales method.The Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are analyzed.The discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance responses.The numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the system.Furthermore,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare maps.Finally,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.
基金Project supported by the National Natural Science Foundation of China(Nos.11832002 and 12072201)。
文摘The chaotic dynamic snap-through and complex nonlinear vibrations are investigated in a rectangular asymmetric cross-ply bistable composite laminated cantilever shell,in cases of 1:2 inter-well internal resonance and primary resonance.The transverse foundation excitation is applied to the fixed end of the structure,and the other end is in a free state.The first-order approximate multiple scales method is employed to perform the perturbation analysis on the dimensionless two-degree-of-freedom ordinary differential motion control equation.The four-dimensional averaged equations are derived in both polar and rectangular coordinate forms.Deriving from the obtained frequency-amplitude and force-amplitude response curves,a detailed analysis is conducted to examine the impacts of excitation amplitude,damping coefficient,and tuning parameter on the nonlinear internal resonance characteristics of the system.The nonlinear softening characteristic is exhibited in the upper stable-state,while the lower stable-state demonstrates the softening and linearity characteristics.Numerical simulation is carried out using the fourth-order Runge-Kutta method,and a series of nonlinear response curves are plotted.Increasing the excitation amplitude further elucidates the global bifurcation and chaotic dynamic snap-through characteristics of the bistable cantilever shell.
基金supported in part by the National Natural Science Foundation of China(62001356)in part by the National Natural Science Foundation for Distinguished Young Scholar(61825104)+1 种基金in part by the National Key Research and Development Program of China(2022YFC3301300)in part by the Innovative Research Groups of the National Natural Science Foundation of China(62121001)。
文摘Weak signal reception is a very important and challenging problem for communication systems especially in the presence of non-Gaussian noise,and in which case the performance of optimal linear correlated receiver degrades dramatically.Aiming at this,a novel uncorrelated reception scheme based on adaptive bistable stochastic resonance(ABSR)for a weak signal in additive Laplacian noise is investigated.By analyzing the key issue that the quantitative cooperative resonance matching relationship between the characteristics of the noisy signal and the nonlinear bistable system,an analytical expression of the bistable system parameters is derived.On this basis,by means of bistable system parameters self-adaptive adjustment,the counterintuitive stochastic resonance(SR)phenomenon can be easily generated at which the random noise is changed into a benefit to assist signal transmission.Finally,it is demonstrated that approximately 8dB bit error ratio(BER)performance improvement for the ABSR-based uncorrelated receiver when compared with the traditional uncorrelated receiver at low signal to noise ratio(SNR)conditions varying from-30dB to-5dB.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102143,12172151,and 12172149)National funded postdoctoral researcher program(Grant No.GZC20230962)+4 种基金Guangdong Basic and Applied Basic Research Foundation(Grant No.2024A1515010379)Natural Science Foundation of Guangzhou City(Grant Nos.202201010217,202201020539,and 2024A04J3401)Young Talent Support Project of Guangzhou Association for Science and Technology,the Fellowship of China Postdoctoral Science Foundation(Grant No.2022M711333)the Fundamental Research Funds for the Central Universities(Grant No.21623332)the High Performance Public Computing Service Platform of Jinan University.
文摘Bistable curved shells have become a promising low-cost application in energy absorption fields owing to recentadvances in material and technology.Significant research has been conducted to improve their energy absorptioneffect through forward prediction and single-objective optimization.However,these approaches may not fully explore their functional potential.In this study,we propose a multi-objective optimization framework based on theprinciple of main objective optimization that combines neural networks and genetic algorithms.The energy absorption effect and backward snapping force of the bistable curved shell are improved synchronously.Meanwhile,a reverse design algorithm is developed to generate the preset load-displacement curve,which further expandsthe application of machine learning methods in the field of multi-objective optimization.The combination ofmachine learning and multi-objective optimization is highly effective for building meta-structures with specificperformance requirements and has potential applications in solving complex optimization tasks in various fields.
基金supported by the National Natural Science Foundation of China(Grant Nos.22271139)the Fundamental Research Funds for the Central Universities(020514380294).
文摘Smart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices.Smart bistable coordination complexes are a class of functional complexes which have two stable states that can be reversibly switched in response to external stimuli.Such bistable molecules play a vital role in various applications,such as sensors,data storage,spintronics,smart windows,optical switches,information encryption and decryption,displays,actuators,etc.Herein,the recent research studies into the development of these smart bistable metal coordination complexes are reviewed.According to the different external stimuli,these smart bistable coordination systems have been classified and summarized,including light-responsive systems,thermally-responsive systems,electrically-responsive systems,mechanicallyresponsive systems,and some other cases.These systems are further subdivided according to the changes in signals(e.g.,color,fluorescence,spin state,crystalline phase)under external stimuli.The design principles of each type of smart bistable metal complexes as well as their broad and innovative applications are comprehensively described.Finally,the challenges and opportunities in this field are briefly analyzed and discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11902081)the Science and Technology Projects of Guangzhou (Grant No. 202201010326)the Guangdong Provincial Basic and Applied Basic Research Foundation (Grant No. 2023A1515010833)。
文摘This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.
文摘The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a Ti/AgTCNQ/Ati crossbar structure array as organic bistable devices （OBD）.A reversible and reproducible memory switching property,caused by intermolecular charge transfer （CT） in the AgTCNQ thin-film, was observed in the organic bista- ble devices. The positive threshold voltage from the high impedance state to the low impedance was about 3.8-5V, with the reverse phenomenon occurring at a negative voltage of - 3.5- - 4. 4V,lower than that with a CuTCNQ active layer. The crossbar array of OBDs with AgTCNQ is promising for nonvolatile organic memory applications.
基金supported by the National Natural Science Foundation of China(Grants 11772008,11172009,11372015,11232009,10872010,11290152,10732020)the Tianjin Natural Science Foundation(Grant 19JCZDJC32300).
文摘This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.
文摘In this paper we present the control and synchronization of a coupled Bragg acousto-optic bistable map system using nonlinear feedback technology. This nonlinear feedback technology is useful to control a temporally chaotic system as well as a spatiotemporally chaotic system. It can be extended to synchronize the spatiotemporal chaos. It can work in a wide range of the controlled and synchronized signals, so it can decrease the sensitivity down to a noise level. The synchronization can be obtained by the analysis of the largest conditional Lyapunov exponent spectrum, and easily implemented in practical systems just by adjusting the coupled strength without any pre-knowledge of the dynamic system required.
基金supported by the National Natural Science Foundation of China (Grant 11172199)
文摘By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by the second order Melnikov function. Secondly, the effects of each item in chaos threshold expression are analyzed. The excitation frequency and resistance values, which have the most influence on chaos threshold value, are found. The result from the second order Melnikov function is more accurate compared with that from the first order Melnikov function. Finally, the attraction basins of large amplitude motions under different exciting frequency, exciting amplitude, and resistance parameters are given.
基金financial support from the National Science Foundation of the United State (Grants 1752575 and 1644579)
文摘Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and expensive computations.In this work,we present a method to easily and rapidly design bistable buckled beams subjected to a transverse point force.Based on the Euler–Bernoulli beam theory,we establish a theoretical model of bistable buckled beams to characterize their snapthrough properties.This model is verified against the results from a finite element analysis(FEA)model,with maximum discrepancy less than 7%.By analyzing and simplifying our theoretical model,we derive explicit analytical expressions for critical behavioral values on the force-displacement curve of the beam.These behavioral values include critical force,critical displacement,and travel,which are generally sufficient for characterizing the snapthrough properties of a bistable buckled beam.Based on these analytical formulas,we investigate the influence of a bistable buckled beam's key design parameters,including its actuation position and precompression,on its critical behavioral values,with our results validated by FEA simulations.Our analytical method enables fast and computationally inexpensive design of bistable buckled beams and can guide the design of complicated systems that incorporate bistable mechanisms.
基金supported by the Doctor Foundation of Southwest University of Science and Technology of China (Grant No. 08zx7108)
文摘This paper investigates the stochastic resonance in a time-delayed bistable system subjected to multiplicative and additive white noise and asymmetric dichotomous noise. Under the adiabatic approximation condition, the expression of the signal-to-noise ratio （SNR） is obtained. It finds that the SNR is a non-monotonic function of the delayed times, of the amplitude of the driving square-wave signal, as well as of the asymmetry of the dichotomous noise. In addition, the SNR varies non-monotonously with the intensities of the multiplicative and additive noise as well as the system parameters. Moreover, the SNR depends non-monotonically on the correlate rate of the dichotomous noise.
基金supported by National Natural Science Foundation of China(Grants 11802071,11902193,and 11625208)Natural Science Foundation of Shanghai(Grant 19ZR1424300).
文摘As two crucial indicators of bistable energy harvesting performance,band width and power amplitude are simultaneously investigated for obtaining the synergy effect.Toward this goal,a nonlinear electromechanical-coupled distributed-parameter model of the bistable piezoelectric energy harvester is established.Based on the electromechanical decoupled method,approximate higher-order analytical solutions of the beam displacement,harvested power and effective bandwidth are derived.The cubic-function discriminant of the analytical solution is introduced to determine the nonlinear excitation-frequency boundaries of multiple solutions and power peak.The stability of the multiple solutions is analyzed through Jacobi matrix of the modulation equation.Superharmonic resonance is notified.Upward and downward sweep experiments and numerical solutions of time history curves,phase portraits and power spectra confirm the analytical findings.To realize optimized broadband energy harvesting,the parametric study on the coefficients of the linear and cubic elastic external forces with the corresponding optimal load resistance is performed.For the nonlinear hardening case,more positive linear coefficient is preferred.For the nonlinear softening case,the cubic coefficient slightly larger than its optimal value is recommended at each given linear coefficient.By tuning the load resistance and linear and cubic coefficients of the external force,broadband bistable energy harvesting with optimized power is realized.
基金Project supported by the National Natural Science Foundation of China(Grant No.11772048)
文摘Stochastic resonance（SR） is studied in an under-damped bistable system driven by the harmonic mixing signal and Gaussian white noise. Using the linear response theory（LRT）, the expressions of the spectral amplification at fundamental and higher-order harmonic are obtained. The effects of damping coefficient, noise intensity, signal amplitude, and frequency on spectral amplifications are explored. Meanwhile, the power spectral density（PSD） and signal-to-noise ratio（SNR） are calculated to quantify SR and verify the theoretical results. The SNRs at the first and second harmonics exhibit a minimum first and a maximum later with increasing noise intensity. That is, both of the noise-induced suppression and resonance can be observed by choosing proper system parameters. Especially, when the ratio of the second harmonic amplitude to the fundamental one takes a large value, the SNR at the fundamental harmonic is a monotonic function of noise intensity and the SR phenomenon disappears.
基金Project supported by the National Nature Science Foundation of China （Grant No 10363001） and the project of Baoji University of Sciences and Arts of China （Grant No ZK2508）.
文摘The steady-state properties of a bistable system are investigated when both the multiplicative noise and the coupling between additive and multiplicative noises are coloured with different values of noise correlation times T1 and T2. After introducing a dimensionless parameter R（R = α/D, D is the intensity of the multiplicative noise and a is the intensity of the additive noise）, and performing the numerical computations, we find the following points： （1） For the case of R 〉 1, A （the intensity of correlation between additive and multiplicative noises）, T1 and T2 can induce the stationary probability distribution （SPD） transition from bimodal to unimodal in structure, but for the cases of R _〈 1, the bimodal structure is preserved; （2） a can also induce the SPD transition from bimodal to unimodal in structure; （3） the bimodal structure of the SPD exhibits a symmetrical structure as D increases.
