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Calcination-free synthesis of high strength self-cleaning anti-reflective MgF2-TiO2 coating
摘要： In order to understand the nonlinear dynamic behavior of a planar mechanism with clearance, the nonlinear dynamic model of the 2-DOF nine-bar mechanism with a revolute clearance is proposed; the dynamic response, phase diagrams, Poincar′e portraits, and largest Lyapunov exponents (LLEs) of mechanism are investigated. The nonlinear dynamic model of 2-DOF nine-bar mechanism containing a revolute clearance is established by using the Lagrange equation. Dynamic response of the slider’s kinematics characteristic, contact force, driving torque, shaft center trajectory, and the penetration depth for 2-DOF nine-bar mechanism are all analyzed. Chaos phenomenon existed in the mechanism has been identi?ed by using the phase diagrams, the Poincar′e portraits, and LLEs. The e?ects of the di?erent clearance sizes, di?erent friction coe?cients, and di?erent driving speeds on dynamic behavior are studied. Bifurcation diagrams with changing clearance value, friction coe?cient, and driving speed are drawn. The research could provide important technical support and theoretical basis for the further study of the nonlinear dynamics of planar mechanism.
关键词： Lyapunov exponent,nonlinear dynamics,chaos,clearance joint,bifurcation
更新于2025-09-23 15:23:52
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A Parameter Estimation based MPPT Method for a PV System using Lyapunov Control Scheme
摘要： There are two types of external variations which change the operating point of a photovoltaic (PV) system: one is environmental change caused by variation in temperature and/or irradiance and the other is load change. The variation in environmental condition changes the PV array characteristic itself whereas the load variation changes the operating point within the same curve. Each type of change can be uniquely identified using history of PV voltage and current measurements. Using the above fact, this paper proposes a fast maximum power point tracking (MPPT) technique for PV array coupled with boost converter. The proposed method determines MPP in a single step by finding out temperature and irradiance at which the PV array is operating. Furthermore, based on the measured values of PV voltage and current, inductor current and load voltage are also calculated, eliminating the need for additional sensors. Lyapunov based controller (LBC) is implemented to track inductor current to its desired value and find the desired duty cycle to reach MPP. The proposed method is validated by both simulation and experimental results under varying temperature, irradiance and load condition. A comparison with the existing MPPT method is also presented in order to show the efficacy of the proposed method.
关键词： MPPT,DC-DC converters,Lyapunov Function,Incremental Conductance,PV cell,Parameter Estimation
更新于2025-09-23 15:21:21
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Two-dimensional optical chimera states in an array of coupled waveguide resonators
摘要： Two-dimensional arrays of coupled waveguides or coupled microcavities allow us to confine and manipulate light. Based on a paradigmatic envelope equation, we show that these devices, subject to a coherent optical injection, support coexistence between a coherent and incoherent emission. In this regime, we show that two-dimensional chimera states can be generated. Depending on initial conditions, the system exhibits a family of two-dimensional chimera states and interaction between them. We characterize these two-dimensional structures by computing their Lyapunov spectrum and Yorke–Kaplan dimension. Finally, we show that two-dimensional chimera states are of spatiotemporal chaotic nature.
关键词： Lyapunov spectrum,optical chimera states,Yorke–Kaplan dimension,spatiotemporal chaos,coupled waveguide resonators
更新于2025-09-23 15:19:57
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Intensity modulator based on femtosecond laser assisted waveguide fabrication inside X-cut LiNbO <sub/>3</sub> crystal
摘要： This paper presents a novel method to address the actuator saturation for nonlinear hybrid systems by directly incorporating user-defined input bounds in a controller design. In particular, we consider the application of bipedal walking and show that our method [based on a quadratic programming (QP) implementation of a control Lyapunov function (CLF)-based controller] enables a gradual performance degradation while still continuing to walk under increasingly stringent input bounds. We draw on our previous work, which has demonstrated the effectiveness of the CLF-based controllers for stabilizing periodic gaits for biped walkers. This paper presents a framework, which results in more effective handling of control saturations and provides a means for incorporating a whole family of user-defined constraints into the online computation of a CLF-based controller. This paper concludes with an experimental validation of the main results on the bipedal robot MABEL, demonstrating the usefulness of the QP-based CLF approach for real-time robotic control.
关键词： legged locomotion,Quadratic programming,Lyapunov methods
更新于2025-09-23 15:19:57
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Adaptive Pixel-Selection Fractional Chaotic Map Lattices for image cryptography
摘要： Chaotic theory has been employed in cryptography application for establishing a sequence of data closest to pseudorandom number. Image cryptography with Chaotic Map Lattices (CML) uses the chaos parameters, the number of iterations and the number of cycles for encryption as secret keys. Amount of secret keys has a great impact on security in cryptography. Adaptive Pixel-Selection Fractional Chaotic Map Lattices (APFCML) enhances the encryption security by introducing a novel non-integer fractional order concept as secret keys. Fractional chaos is modified chaos with a fractional differential equation containing derivatives of non-integer order. A non-integer order has an effect on the range of chaos's parameter. Moreover, the encryption sequence has been adaptively selected based on another chaos generator. In the experiments, the measurement indices of originality preservation, visual inspection, and statistical analysis are used to evaluate the performance of the proposed APFCML compared to that of the original CML.
关键词： fractional logistic,bifurcation diagram,image cryptography,Lyapunov exponent,Chaotic
更新于2025-09-23 15:19:57
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A Practicable Copula-Based Approach for Power Forecasting of Small-Scale Photovoltaic Systems
摘要： This paper presents a novel method to address the actuator saturation for nonlinear hybrid systems by directly incorporating user-defined input bounds in a controller design. In particular, we consider the application of bipedal walking and show that our method [based on a quadratic programming (QP) implementation of a control Lyapunov function (CLF)-based controller] enables a gradual performance degradation while still continuing to walk under increasingly stringent input bounds. We draw on our previous work, which has demonstrated the effectiveness of the CLF-based controllers for stabilizing periodic gaits for biped walkers. This paper presents a framework, which results in more effective handling of control saturations and provides a means for incorporating a whole family of user-defined constraints into the online computation of a CLF-based controller. This paper concludes with an experimental validation of the main results on the bipedal robot MABEL, demonstrating the usefulness of the QP-based CLF approach for real-time robotic control.
关键词： Lyapunov methods,Quadratic programming,legged locomotion
更新于2025-09-19 17:13:59
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Electro-Hydrodynamic Design of an Intelligent Balloon Water Gate Controlled by an Efficient Maximum-Power-Seeking Controller for a Solar Generation System
摘要： The intelligent balloon water gate (IBWG) invention is a hydraulic gate model made of reinforced plastic that controls the water level (WL) downstream or upstream of a barrage. The IBWG automatically in?ates and de?ates by compressed air to close and open the water passage, respectively. The whole design consists of a balloon, a waterway, sensors, an air compressor, a control panel, an electrical circuit and a photovoltaic generation (PVG) system. The Tyass barrage in Iraq was considered as a case study. The Tyass barrage was built with concrete and four sliding steel water gates and redesigned using the IBWG. The originality of the current research resides in the combination of the IBWG mechanism with an ef?cient maximum power point (MPP) seeking controller for a photovoltaic generation system, which is one of the most promising sources of renewable energy in the world. To the best of our knowledge, in this ?eld, this scenario has not yet been discussed in detail. Upper and lower water sensors are used to control the IBWG. The upper sensor sends a signal to the control panel when the downstream water level reaches its maximum value to open the air inlet valve and close the outlet valve, in?ating 14 IBWGs with a volume of 3.5 m3 under 122 psi of pressure and closing the water passage. When the WL decreases below the minimum level, the lower sensor initiates the opposite procedure. The air compressor automatically ?lls the air tank to 181 psi and is supplied by a 24 VDC AGM rechargeable battery with a capacity of 40-60 Ah, which is charged by four solar panels connected in parallel and exposed to an average of 8.8 hrs/day of sunshine. The proposed MPP-seeking controller was implemented by a backstepping design coupled with the grey wolf mechanism. The solar irradiance data were observed 39 years ago. The proposed controller is capable of following the MPP with minimum oscillations under an external irradiance variation. The IBWG system is veri?ed at night or during the early morning when the sun is not active. Nevertheless, it is possible to store compressed air in an auxiliary tank to avoid emergencies such as partial shading conditions.
关键词： PVG system,backstepping technique,lyapunov stability,grey wolf optimization,Electro-hydrodynamic rubber water gate
更新于2025-09-16 10:30:52
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A novel Lyapunov stable higher order B-spline online adaptive control paradigm of photovoltaic systems
摘要： In this paper, research on the control of photovoltaic (PV) using a novel higher order B-spline online adaptive neuro-fuzzy paradigm considering high external uncertainties in weather and load demand is presented. We optimize the existing neuro-fuzzy technique by incorporating third order B-spline membership functions in its antecedent part, which we solve using an on-line learning gradient-decent back propagation method. We fit the system parameters online through adaptive fuzzy rules extracted from the maximum power point tracking (MPPT) error and its derivative. Unlike many existing neuro-fuzzy techniques, our method addresses the trapping in local minima. The proposed controller is demonstrated to be stable using Lyapunov stability analysis. The performance of our control philosophy is checked in terms of output power tracking, efficiency, and MPPT error. Finally, we validate via simulation the high robustness and the self-adaptation ability of the proposed method over other existing traditional and intelligent techniques.
关键词： B-spline membership functions,Photovoltaic systems,Maximum power point tracking,Adaptive neuro-fuzzy control,Lyapunov stability
更新于2025-09-16 10:30:52
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[IEEE 2019 4th World Conference on Complex Systems (WCCS) - Ouarzazate, Morocco (2019.4.22-2019.4.25)] 2019 4th World Conference on Complex Systems (WCCS) - Adaptive High Gain Observer for Photovoltaic Systems
摘要： The problem of state and parameter estimation in photovoltaic (PV) systems is considered. The system is composed of a photovoltaic generator (PVG) which supplies power, via a long PV cable, to a DC centrifugal pump driven by a DC–DC boost converter. The maximum power point tracking (MPPT) techniques and controllers are generally designed based on the PVG delivered voltage and/or current measurements. From other side, PV arrays should be established in a location that pro?ts from good daily solar radiation. Such a location is, in numerous cases, remote from the converter, which obviously leads to dif?culty of PVG voltage and current measurement. Besides, the use of a long PV cable may result in MPPT control inaccuracies due to voltage drops in the cable. For remedying these issues, an adaptive observer for PV systems is proposed, in this work. It accomplishes online estimation of PVG current and voltage as well as of the unknown resistance parameter of the cable. The designed adaptive observer convergence is theoretically proved and its performances are evaluated by simulation.
关键词： PV Cable,Uncertainty,Adaptive High Gain Observer,Photovoltaic,MPPT,Lyapunov Stability
更新于2025-09-12 10:27:22
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Characterization of spatiotemporal chaos in arrays of nonlinear plasmonic nanoparticles
摘要： We investigate spatiotemporal chaos dynamics in a finite nanoparticles array with Kerr-type nonlinear response, excited by an incident plane wave of varying intensity and tunable frequency close to the localized plasmon resonance of a single particle. Considering dipole-dipole coupling between the nanoparticles described by their polarizability, we compute the temporal evolution of the dipoles and numerically extract the Lyapunov spectra, allowing us to characterize different dynamical behaviors. Furthermore, we estimate the Kaplan-Yorke dimension that provides a measure of the strange attractor complexity. We show that time-modulated solutions which are generated at the onset of modulational instability experience secondary instabilities leading to a complex nonlinear dynamic. It is also shown that in the highly nonlinear regime, the spatiotemporal chaos is robust and exists in a large range of parameters that we have determined numerically.
关键词： nonlinear plasmonic nanoparticles,modulational instability,Lyapunov spectra,spatiotemporal chaos,Kaplan-Yorke dimension
更新于2025-09-11 14:15:04