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This paper constructs a new 4D chaotic system from the Sprott B system. The system is dissipative, chaotic with two saddle foci. The bifurcation diagrams verify that the system exists multiple attractors with different initial values, including two strange attractors, two periodic attractors. Furthermore, we apply the passive control to control the system. A controller is designed for driving the system to the origin. The simulations show our theoretical results visually.

In this study, active and passive control techniques are applied for the synchronization of two identical Vilnius chaotic oscillators. The differential equations of Vilnius oscillator are described according to its circuit model. Based on Lyapunov function, the active and passive controllers are used to realize the synchronization of Vilnius chaotic systems. Numerical simulations are presented to verify and compare the effectiveness of proposed control techniques.

This work deals with the passive control-based chaos synchronization with circuit design for secure communication. First, the numerical simulation and electronic circuit design of a simple five-term chaotic system are performed. The numerical simulation and electronic circuit design outputs have confirmed each other. Then, the passive control method is applied for synchronizing two identical five-term chaotic systems using only one state control signal. After the synchronization study, design and analysis for secure communication by chaotic masking method are conducted in Matlab–Simulink platform. Finally, an electronic circuit design is performed for the designed communication system. In the designed communication system with Matlab–Simulink platform and electronic circuit design, information signal which is sent from the transmitter unit is successfully retrieved at the receiver unit. As a result, the electronic circuit design has shown that a single state passivity-based synchronization signal can be effectively used for secure data communication applications for the real environment.

Recently, the concept of feedback passivity-based control has drawn attention to chaos control. In all existing papers, the implementations of passivity-based control laws require the system states for feedback. In this paper, a passivity-based control law which only requires the knowledge of the system output is proposed. Simulation results are provided to show the effectiveness of the proposed solution.

Dynamics of a system formed by a linear structure coupled to a light nonlinear oscillator, both subjected to external excitations, is studied. Effects of the external forcing of the nonlinear oscillator are especially investigated. Complex geometry of the slow invariant manifold and equilibrium and singular points of the system are detected thanks to a multiple time scale strategy around 1:1:1 resonance. Equilibrium points lead to periodic regimes while singular points are hints of strongly modulated response of the system characterized by repeated bifurcations around its stable zones. A method for detection of changes in mechanical properties of main structural system is explained. Numerical simulations obtained by direct integration of the system are used to validate analytical predictions.

A Caputo fractional-order derivative is used in a Quadrotor Unmanned Aerial Vehicle (QUAV) chaotic system to transform it into fractional ordered QUAV (FoQUAV) chaotic system for the first time. Therefore, this study explores three control (adaptive, active, and passive) strategies applied on the FoQUAV system. Further, utilizing Lyapunov theory, we established global stability around the equilibrium point and conducted numerical simulations for validation and comparison. In this work, adaptive control technique is used by considering $a_f$, $a_g$, and $a_h$ as unknown parameters and are derived using updated law. Similarly, active control technique is derived using two sub-controllers including ${\widehat{\mu }}_i=A_i+N_i$ with $A_i$; linear and $N_i$; nonlinear controllers, respectively. Finally, a feedback linearization-based, passive controller is used, which has predefined control input and converges to a stable equilibria. Moreover, this work also revealed, during performing numerical simulations, that the open loop system stabilizes at times $t\approx 4$ s, $t\approx 60$ s, and $t\approx 90$ s, respectively, for adaptive, active, and passive controllers. Finally, the passive controller face several challenges during stabilizing the yaw of a considered system and overall is proved that adaptive controller perform best with respect to time consumption and quick performance in comparison.

The focus of the present research is to eliminate the undesired steady-state vibrations at selected lines or locations in a vibrating plate by means of adding attachments at arbitrary selected locations. These attachments can be either added concentrated masses and/or translational or rotational springs which are connected to the plate at one end and grounded at the other. The case of attachment of translational and/or rotational oscillators systems is examined. In addition, imposing lines of zero displacements (nodal lines) at selected locations are also investigated. The dynamic Green's function method is employed. Several numerical examples are cited to verify the utility of the proposed method. In addition, sample experiments to measure the plate free and forced vibrations for the given boundary conditions are conducted and the experimental measurements are compared with the analytical results.

A common and successful way of structural control is to dissipate the seismic kinetic energy via frictional dampers. Response of a friction damped frame during an earthquake excitation is heavily dependent to the slippage limit of the frictional dampers. Low values of slippage load may lead to excessive deformations while large slippage loads may prevent sliding. Therefore, selecting appropriate values for slippages loads of the dampers is very important in order to have optimum energy dissipating system. Utilizing a response modification factor, the standard seismic design code procedure can be applied to the frames equipped with frictional dampers to determine the value of slippage loads. In this investigation, the response modification factor of steel moment resisting frames equipped with frictional dampers is evaluated considering the effects of various slippage loads. The response modification factor is calculated for two bay widths of 5 m and 7 m in length. It is shown that the optimum slippage load that results in the maximum response modification factor is in the range of 8% to 20% of the total weight of the structure. The taller the structure is, the less the optimum slippage load will be. Finally, an equation is proposed for the response modification factor as a function of the slippage load.

This paper describes a case-study where the human-induced vibrations of a footbridge have been controlled by means of the modification of its natural frequencies. The structure, a Nielsen variable depth truss, is located over a highway on the outskirts of Malaga (Spain), so that it was designed to withstand low pedestrian densities and its dynamic behavior was just analyzed according to Spanish standards at the date of construction. However, the presence of a nearby sports pavilion originated unexpected large pedestrian flows. This new service condition was not properly anticipated, leading to significant longitudinal vibration levels. To overcome this problem, experimental and numerical studies were carried out, with the aim of finding a low cost solution that yet maintained the footbridge aesthetic appearance. Following these studies, corrective measures that increased its stiffness were then adopted. Subsequently, experimental tests and a finite element model tuning were performed to obtain: (i) its modified modal parameters; and (ii) a more accurate estimation of its dynamic behavior under different pedestrian flows. Presently, the footbridge has been in service for more than four years, maintaining an adequate comfort level.

The passive control using winglets has been considered to be an alternative solution for control of flutter and buffeting responses of long suspension bridges. This method is aimed at not only developing lightweight, reduced-cost stiffening girders without adding stiffness for aerodynamic stability, but also avoiding problems from malfunctions caused by the control and energy supply systems of active control devices by winglets. This paper presented a mechanically controlled approach using the winglets, for which a two-dimensional bridge deck model was numerically and experimentally studied. In addition, numerical research on the flutter and buffeting passive control of a 3000m span suspension bridge was carried out. The result showed that the flutter speed of the suspension bridge increases, whereas the buffeting response decreases, through the implementation of the winglets.

High and slender towers may experience excessive vibrations caused by both wind and seismic loads. To avoid excessive vibrations in towers, tuned mass dampers (TMDs) are often used as passive control devices due to their low cost. The TMDs can absorb part of the energy of vibration transmitted from the main structure. These devices need to be finely tuned in order to work as efficient dampers; otherwise, they can adversely amplify structural vibrations. This paper presents the optimal parameters of a pendulum TMD (PTMD) to control the vibrations of slender towers subjected to an external random force. The tower is modeled as a single-degree-of-freedom (SDOF) mass–spring system via an assumed-mode procedure with a pendulum attached. A genetic algorithm (GA) toolbox developed by the authors is used to find the optimal parameters of the PTMD, such as the support flexural stiffness/damping, the mass ratio and the pendulum length. The chosen fitness function searches for a minimization of the maximum frequency peaks. The results are compared with a sensibility map that contains the information of the maximum amplitude as a function of the pendulum length and the mass ratio between the pendulum and the tower. The optimal parameters can be expressed as a power-law function of the supporting flexural stiffness. In addition, a parametric analysis and a time-history verification are performed for several combinations of mass ratio and pendulum length.

To be a typical flexible structure with small damping, a high-rise television (TV) transmission tower is sensitive to wind excitations. The response control of TV transmission towers by semi-active friction dampers under strong external excitations is still very limited and the parametric study on control performance has not been systematically investigated. To this end, the semi-active control of a wind-excited TV transmission tower by piezoelectric friction dampers is conducted in this study. A fine finite element (FE) model of a real TV transmission tower is constructed and then a two-dimensional (2D) dynamic model is also established. The analytical model of a semi-active friction damper based on piezoelectric actuators is then established with damper stiffness considered. The equations of motion of the tower with friction dampers are then established. The local feedback control algorithm based on nonlinear Reid damping mechanisms is used to command piezoelectric friction dampers for wind-excited towers. A high-rise TV transmission tower in China is used to investigate the validity of the proposed semi-active control approach and compared with that of passive control. Furthermore, a detailed parametric investigation is conducted to examine the influence of gain coefficient, damper stiffness, hysteresis loops, damper force, and wind loading intensity on control efficacy. The analytical results indicate that piezoelectric friction dampers with optimal parameters are beneficial to the vibration mitigation of TV transmission towers under different wind loading intensities.

Atrium building is a common structural type that can be found in most of the big cities. For seismic vibration control of buildings with large atria, this paper proposes a novel approach of using a core structure inside the atrium building in combination with a truss-inertial mass damper (IMD) system to form a passive control mechanism. The proposed system utilizes the unsynchronized vibrations between the tops of the building and the core structure to activate the IMD for seismic energy dissipation. To evaluate the effectiveness of the proposed truss-IMD system, a numerical time-history method is first developed to compute structural response of the atrium building under an earthquake input, followed by parametric studies of the system. Effects of truss stiffness, inertance, and nonlinearity of the IMD on seismic performance of the atrium building are investigated. Results from a simple structural model and a six-story building indicate that the truss-IMD system can significantly alleviate the dynamic responses of the building, and the overall seismic performance improvement brought by the truss-IMD surpasses a truss-viscous damper system. Results also show that for a given set of truss stiffness and damper nonlinearity, there exists an optimal combination of inertance and damping coefficient for the IMD to achieve a maximum structural performance.

Improving the ability of nonlinear energy sink (NES) to suppress large vibrations under strong excitation has been widely concerned. Moreover, distributing NES to suppress multimodal resonances is also an issue that deserves more attention. This paper investigates the distribution strategy of the series NES in suppressing the vibration of a two-degree-of-freedom (2-DOF) system. Dynamic models are developed for two strategies: centralized and distributed series NES. The vibration reduction efficiency of these strategies is compared, and the approximate results obtained from the analytical analysis were verified using numerical methods. The research results indicate that distributing the series NES among different vibration sources can lead to improved vibration reduction performance. Moreover, the distributed vibration reduction strategy exhibits greater adaptability to different modes of primary system. Furthermore, while keeping the total additional weight of the NES unchanged, the effects of the series NES and 1DOF NES on vibration control were compared. The results demonstrate that, under large amplitude excitation, the series NES has a better vibration reduction effect than the 1DOF NES when using distributed NES to control the vibration of a 2-DOF system. Additionally, by studying the energy transfer between NES oscillators in series, the series NES with high stiffness asymmetry exhibits superior vibration reduction. The findings of this study contribute to the advancement of research on the NES control of strong excitation vibration and multi-mode structure vibration.

In recent years, much attention has been paid to research and development of structural control techniques with particular emphasis on alleviation of wind and seismic response of buildings and bridges in China. Structural control in civil engineering has been developed from the concept into a workable technology and applied into practical engineering structures. The aim of this paper is to review a state-of-the-art of researches and application of structural control in civil engineering in China. It includes the passive control, active control, hybrid control, and semi-active control. Finally, the possible future directions of structural control in civil engineering in China are presented.

Previous research has shown the effectiveness of the integrated design of weakening and damping techniques (WeD) for the seismic retrofitting of structures. Indeed, WeD techniques are able to reduce inter-story drifts and total accelerations, the two major performance measures to evaluate the seismic behavior of structures. Past research has been applied to fixed-based structures considering relatively stiff soil conditions. It has been suspected, though, that using such techniques in soft soil sites while considering soil structure interaction, may diminish some of the advantages observed in past research. This paper examines the effect of site conditions and soil-structure interaction on the seismic performance of Weakening and Damping techniques. An established rheological soil-shallow foundation-structure model with equivalent linear soil behavior and nonlinear behavior of the superstructure has been used. A large number of models incorporating wide range of soil, foundation and structural parameters were generated using robust Monte-Carlo simulation. The various structural models, along with the various site conditions, have been used for the comparative study. The design methodologies previously developed by the authors have been applied to each model considering different site conditions leading to the optimal weakening and damping. The results of the comparative study are used to quantify the effects of site conditions and foundation flexibility on the performance of the retrofitted structures.

This paper presents two control methods for a leg prosthesis: a passive based and a variable-damping based. First, the concept of the mechanical design for the leg prosthesis is described. A simulated environment is used to compare the two control methods. The joint setup and its control scheme, in which a passive or a variable-damping control can be easily implemented, are introduced for the prosthetic leg in the simulated environment. Intelligent prosthesis require a specific adjustment for each gait phase based on kinematic events of knee and ankle joints along a gait cycle. A feasible damping profile is generated based on kinematic and dynamical data of the knee joint along a gait cycle. This data set was extracted from a simulated biped which is 1.8m in height and 76 kg in weight with 21 degrees of freedom during normal walking. The data show that the damping profile is critical between the toe-off and heel contact events. Tests using the simulated biped with the passive and the variabledamping controlled leg prosthesis during walking enables the comparison of both control approaches.