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Vestibular dysfunction has been reported as a potential cause in adolescent idiopathic scoliosis (AIS). However, it remained unclear how stochastic galvanic vestibular stimulation (GVS) affected kinetic performance of patients with AIS. This study aimed to investigate the effect of stochastic GVS on ground reaction forces (GRF) measures during obstacle negotiation among patients with AIS. Fifteen patients with AIS and 15 age/sex-matched healthy controls (HC) participated in this study. Stochastic GVS was applied via electrodes placed over bilateral mastoid process with the intensity of 80% of individual sensory thresholds. Six walking trials including 2 types of GVS (stochastic GVS/sham stimulation) and 3 obstacle conditions (Level/Low/High) were randomly allocated to each participant, and each trial was repeated 3 times. Four AMTI force plates were used to measure GRF peaks and impulses in anterior-posterior (AP1/AP2), medial-lateral (ML1/ML2), and vertical (V1/V2) directions. Significant interactions were observed in AP1 (F2,56=3.537, p = 0.036), V1 (F2,56=4.118, p = 0.021), ML1 (F2,56=3.313, p = 0.044) and medial-lateral impulses (F2,56=4.386, p = 0.017) for the step negotiating obstacles. Post-hoc comparisons showed that in comparison to sham stimulation, the application of stochastic GVS significantly (1) increased AP1 (Low: p = 0.038) and V1 (Low: p < 0.001; High: p = 0.035) in two groups; (2) decreased ML1 of two groups (AIS: ps < 0.01; HC: ps < 0.05) and medial-lateral impulses in patients with AIS (Low: p = 0.013; High: p = 0.015) during obstacle negotiation. Additionally, the rates of change in ML1 and medial-lateral impulses among patients with AIS were significantly higher than that of HC, indicating that stochastic GVS demonstrated a greater effect of decreasing ML1 and medial-lateral impulses in AIS. Stochastic GVS ameliorated kinetic performance of patients with AIS during obstacle negotiation, and its potential mechanism may involve the induction of stochastic resonance phenomenon to enhance vestibular perception. Our study offered stochastic GVS as a novel approach to target vestibular-related postural instability in AIS. [ABSTRACT FROM AUTHOR]

The durability of aging bridge structures has become a serious societal concern. It has been estimated that 40%–50% of the bridge stock in Europe and 36% in the US is approaching and exceeding the intended service life in some cases. Conventional retrofitting methods are generally effective under predetermined loading scenarios and can mitigate to some extent the effect of damage through strengthening and stiffening. However, typical retrofit measures involve the addition of components, which might cause unwanted stress accumulation, and in addition, they cannot perform adaptation after damage to recover functionality. Adaptive structural systems can modify the response under loading using sensors and mechanical actuators, instead of relying solely on the resistance offered through material and geometry. Previous work has shown that well-designed adaptive structures are effective in reducing peak responses under strong loading resulting in configurations that embody far fewer material and carbon resources than conventional passive systems. This work investigats retrofit strategies using active control through mechanical actuators integrated into the bridge's primary load path or as external systems. The objective is to extend the durability of most common bridge types including beam, tied-arch, and cable-stayed. Two active retrofit systems are considered: (1) an external adaptive tensioning (EAT) for beam bridges; (2) linear actuators placed in the hangers and stays of tied-arch and cable-stayed bridges. Depending on the failure mode (e.g., corrosion-, fatigue-induced), the effect of active control is simulated through a quasi-static controller based on least-squares minimization or through a linear quadratic regulator and explicit time-history analysis. Results shows that the stress reduction achieved by the EAT system retrofitted to a concrete bridge with corrosion-induced damage could extend service by approximately 12 years. In both cable-stayed and tied-arch bridges, the stress range amplitude caused by vehicular traffic is reduced below the constant amplitude fatigue limit, potentially extending service beyond 75 years. [ABSTRACT FROM AUTHOR]

The multichannel Airy surface plasmon polariton (SPP), which has the potential for wider propagation ranges, increased excitation channels on a chip, optical tweezers, nanoparticle capture, energy routing, and so on, has been used in diverse applications in photonics and nanotechnology for years. However, previous studies primarily focused on the dynamic manipulation of Airy SPP beams in single-channel configurations; a path manipulation for multichannel Airy SPP remains unexplored to date. In this investigation, we design a composite fishbone nanostructure for the first time that supports the excitation and active manipulation of multichannel Airy SPP main lobes by changing the polarization direction and wavelength of the incident light. Through quantitative characterization using the extinction ratio, we found it exhibits excellent multichannel Airy SPP directional propagation. Moreover, with embedded oxide nanostructures in the gold film, it is found that the main lobe intensity can be effectively enhanced in the propagation path. Our results provide a higher degree of freedom for the application of optical tweezers, nanoparticle capture, and energy routing. [ABSTRACT FROM AUTHOR]

Among various structural vibration control categories, active control typically provides superior control performance. However, its high energy demand often limits its extensive implementation in large-scale civil structures. Very recently, electromagnetic dampers, which can convert kinetic energy into electrical energy, have emerged as a novel solution for active control with reduced or even zero energy consumption. This study explored the feasibility of an energy-harvesting active tuned mass damper (ATMD) by using an electromagnetic damper for simultaneous vibration suppression and energy harvesting. Numerical simulations were conducted for a full-scale, 76-story benchmark building equipped with the proposed design. The proposed ATMD outperforms the optimised passive counterpart of the same mass, as the former introduces an evident reduction in displacement responses. Furthermore, the proposed ATMD can offer a commensurate control performance to a passive damper with a weight three times heavier. The proposed ATMD also exhibits promising energy-harvesting performance, achieving an average output power at the kilowatt level. The results suggest that electromagnetic devices hold great potential for large-scale applications in civil structures, paving the way for a prosperous future in this field. [ABSTRACT FROM AUTHOR]

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 af, ag, and ah as unknown parameters and are derived using updated law. Similarly, active control technique is derived using two sub-controllers including μ̂i = Ai + Ni with Ai; linear and Ni; 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 ≈ 4 s, t ≈ 60 s, and t ≈ 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. [ABSTRACT FROM AUTHOR]

Hunting stability is an inherent property of railway vehicles that determines the operational speed. This paper establishes a half-vehicle model with nonlinear wheel/rail equivalent conicity and interactive forces. Additionally, the dynamic performances of vehicle under various levels of wheel wear with passive suspension are compared and analyzed. Importantly, the investigation delves into the hunting stability of the vehicle system, employing both linear and nonlinear control approaches. The results demonstrate a notable reduction in critical speed during the end-worn period with a passive suspension. However, this reduction can be substantially countered through the application of active control, resulting in a significant speed increase. The implementation of stiffness control raises the frequency of limit cycles, whereas damping control serves to diminish it. Notably, an appropriate linear cubic stiffness control effectively mitigates the amplitudes of limit cycles during instances of instability. Moreover, the control strategy derived from the simplified model is extended to enhance the stability of the entire vehicle system. The research findings hold the potential to offer a promising strategy for the active control of high-speed vehicles, particularly during periods of wheel wear. [ABSTRACT FROM AUTHOR]

In petroleum engineering, the performance of drilling fluid is the key factor affecting the drilling success. Drilling fluid rheology can be measured by tube measurement. Fluid pulsation will cause measurement deviation of differential pressure and flow velocity data during measurement, and it accumulates when the flow curve is drawn. Finally, the accuracy of drilling fluid rheological pipe measurement is seriously affected. In view of the problem of fluid pulsation can seriously affect the accuracy of tube measurement. This paper proposed an algorithm based on Filtered-x least mean square (FxLMS). First, the active control strategy is studied, the mathematical model of electric regulating valve control is established, the FxLMS algorithm of variable step length is studied, the simulation model of the control system is established, and the control effect of different algorithms is compared. The dynamic experimental platform of fluid pulse active control for drilling fluid rheological pipe measurement is designed and built. The experimental data show that: after active control, the average relative error of drilling fluid shear force decreased by 179.6%, the average relative error of plastic viscosity decreased by 78.1%, and the average relative error of the apparent viscosity decreased by 25.5%. It proves that the active control algorithm can improve the accuracy of tube measurement more effectively. [ABSTRACT FROM AUTHOR]

This research introduces a novel active mass damper (AMD) that operates based on magnetic force. The proposed AMD utilizes magnetic force to control the damper's and reduces the structural vibrations by the reaction force exerted by the mass onto the system. The utilization of magnetic force increases the performance of the AMD. The magnitude of the control force is determined by employing PID control based on the measured acceleration response of the structure on which the AMD is mounted. An experimental study is conducted to assess and evaluate the performance of the AMD. The study utilizes an experimental three-story shear frame as the testing platform, with the AMD mounted on the structure. The AMD's mass is chosen to be approximately 3% of the total structural mass. A comparison of the obtained structural responses to those of the structure fitted with a passive mass damper shows the promising efficacy of the proposed AMD in reducing the structural responses across a broad frequency range. The results obtained from both experimental tests and analytical analyses provide confirmation of the effectiveness of the AMD within the range of the structure's primary modes. The most significant points of the presented device are having a high performance in reducing vibration despite the small weight and efficiency in a wide frequency range by using magnetic force. [ABSTRACT FROM AUTHOR]

Abstract In this work, a control strategy based on fuzzy sliding mode control (FSMC) is applied to effectively manage the large-amplitude chaotic vibrations exhibited by a simply supported beam. The analysis considers the nonlinear beam structure, which is subjected to an external load. Hamilton’s principle is employed, and the equations of motion are derived for the studied structure. The 3rd Galerkin discretization is employed to derive the ordinary differential governing equation of the structure. A control strategy is presented to decrease the response of the obtained multidimensional system. The vibration of a one-dimensional system is compared with that of the derived multidimensional system. As shown throughout the study, a multidimensional nonlinear system of the structure must be considered for accurate dynamic estimation. By using the recurrent neural network (RNN) model, we can accurately predict chaotic motion and effectively apply control strategies to suppress chaotic motion. The efficacy and suitability of the employed control strategy have been demonstrated by controlling chaos in the beam’s multidimensional system.

Quasi-zero-stiffness (QZS) isolator has great application potential in the field of low-frequency vibration isolation due to its high-static and low-dynamic (HSLD) nonlinear stiffness characteristic, but it is precisely this characteristic that makes it very sensitive to load changes. Once the load changes, causing it to deviate from the equilibrium position, it no longer qualifies zero-stiffness characteristic, and the vibration isolation capacity will be significantly decrease. To make the QZS isolator possess variable load capacity and be more suitable for engineering practice, an active QZS vibration isolator based on electromagnetic actuator is designed in this paper, which eliminates the influence of load changes through the active force of the electromagnetic actuator. First, the dynamic equation of the isolator is established by Newton–Euler method, and the dynamic characteristic of the isolator under standard load and load variations are analyzed through improved incremental harmonic balance (IHB) method based on discrete Fourier transform (DFT). Next, the improved particle swarm optimization (PSO) algorithm are employed to optimize the Proportion Integration Differentiation (PID) controller parameters. Then, the vibration isolation performance of QZS isolator in controlled and uncontrolled and linear systems in the same control state are compared in frequency domain and time domain, respectively. Finally, the performance of active QZS isolator under load variation is discussed. The results indicate that the isolation performance of the QZS isolator under active control is significantly better than in uncontrolled conditions and the controlled linear system. When the load changes, real-time compensation through the actuator output control force can also enable the QZS isolator to achieve a better vibration isolation performance. [ABSTRACT FROM AUTHOR]

Active control of pantograph is an effective method to improve the current received quality in electrified railway systems. To alleviate the negative impact of time delay in pantograph actuator, a Controlled Auto-Regressive Integrated Moving Average (CARIMA) model was designed for pantograph active control. In conjunction with the Euler-Bernoulli catenary model, an improved generalized predictive control (IGPC) algorithm was proposed, and its stability was analyzed. Then, the control performance was verified and discussed through testing. Subsequently, the effects of external disturbances and time delay on control performance were discussed. The results indicate that the proposed controller with a larger control gain, exhibits better performance in reducing fluctuation in contact force between pantograph and catenary, despite being affected by external disturbance and actuator time delay, it still shows significant control performance. [ABSTRACT FROM AUTHOR]

The field of civil engineering has witnessed significant development since the emergence of innovative control strategies that enhanced the construction of structures, imparting valuable resistance against dynamic loads like wind or earthquakes. Despite numerous articles highlighting the potential of various control approaches to reduce vibration, their effectiveness in mitigating the dynamic effects on structures under real-world conditions appears limited once implemented. A variety of factors, including practical constraints, the choice of the control system device, the shape of the structure, and the amount of control energy deployed, contribute to this lack of efficiency. Within this context, the literature primarily addressed the discrepancy between the mathematical model and the actual structure model, commonly referred to as parameter uncertainties, in the controller design process. In other words, logical continuity in this field involves the application of a more adapted control approach, which enhances performance by incorporating more practical aspects in the controller synthesis procedure. These aspects include the dynamics of the control device, high-frequency neglected modes, and the inherent limitations or constraints of the control equipment. Thus, this study treats two main active control systems, ABS and AMD. While applying an approach known as μ-synthesis, the robust control was retained because of its ability to include all these considerations when they act simultaneously. We used this control to make sure that a three-degree-of-freedom structure responds as little as possible to seismic requests, which are shown by an uncertain model. We then conducted a comparative study between these two systems, focusing on displacement reduction and control force, while exploring a classic AMD control system at the top of the structure and an ABS control system at the bottom. This approach proved to be a powerful way to deal with the uncertainties affecting the structure and achieve the stability design objectives, given the satisfying simulation results. [ABSTRACT FROM AUTHOR]

In this work, a control strategy based on fuzzy sliding mode control (FSMC) is applied to effectively manage the large-amplitude chaotic vibrations exhibited by a simply supported beam. The analysis considers the nonlinear beam structure, which is subjected to an external load. Hamilton's principle is employed, and the equations of motion are derived for the studied structure. The 3rd Galerkin discretization is employed to derive the ordinary differential governing equation of the structure. A control strategy is presented to decrease the response of the obtained multidimensional system. The vibration of a one-dimensional system is compared with that of the derived multidimensional system. As shown throughout the study, a multidimensional nonlinear system of the structure must be considered for accurate dynamic estimation. By using the recurrent neural network (RNN) model, we can accurately predict chaotic motion and effectively apply control strategies to suppress chaotic motion. The efficacy and suitability of the employed control strategy have been demonstrated by controlling chaos in the beam's multidimensional system. [ABSTRACT FROM AUTHOR]

This study introduces a brand-new, four-dimensional hyperchaotic system and provides a full analysis of its dynamical characteristics. Time series, phase portraits, Poincaré maps, bifurcation diagrams, estimating the Lyapunov exponents, and determining the Kaplan–Yorke dimension are all used to examine the system. Additionally, the system's equilibrium points are located and their stability is explored. Through the use of active, adaptive, and sliding-mode control approaches, we have also synchronized the newly introduced system. The Lyapunov stability theory and Vaidyanathan's theorem are the foundations upon which the controllers are built to guarantee synchronization between the systems. Finally, MATLAB-based numerical simulations are used to verify the theoretical findings. [ABSTRACT FROM AUTHOR]

A bridge hybrid isolation system, integrating both active and passive control strategies, is proposed and investigated to enhance seismic performance. The system is modeled as a two-layer structure, with the upper layer subjected to active control via a Proportional–Integral–Derivative (PID) controller, and the lower layer employing a conventional passive base isolation system. The displacement response of the superstructure is minimized by the control forces generated by the PID controller, which also accounts for the reaction forces transmitted to the lower isolation layer. To optimize the controller's performance, a genetic algorithm is implemented for real-time tuning of the PID parameters. Numerical simulations, conducted using the Newmark method, are employed to assess the influence of active control on the lower isolation system. The results reveal that, while active control increases the peak displacement of the superstructure to some extent, it significantly prolongs the structural period, thus enhancing the system's overall seismic resilience and stability. [ABSTRACT FROM AUTHOR]

The High-Static-Low-Dynamic (HSLD) stiffness vibration isolators have been exploited in many engineering applications due to its capability in having a wider isolation bandwidth, while maintaining the high static load capacities. However, it will lead to a large payload oscillation at the static equilibrium position, if the source of vibration is an oscillating force originating within the payload. In this case, the considerably large resultant motion of the payload will change the system nonlinearity. An active stiffness control for reducing the displacement amplitude of the payload oscillation subjected to a harmonic force excitation is proposed in this paper. The dynamic model of an actively stiffened HSLD stiffness isolator is introduced, and the approximate analytical expression for forced response is obtained using the Harmonic Balance Method (HBM). The obtained forced response curve has demonstrated that the active stiffness control is able to reduce the system's force response, particularly at low frequencies with an approximation of 50%. The nonlinearity of the system becomes smaller as the active stiffness control is applied. [ABSTRACT FROM AUTHOR]

The interest in phononic crystals and acoustic metamaterials has been an intensive subject of research in recent years. Finding a robust way to significantly expand or actively control the bandgap has received extensive attention. In this study, we propose a prestressed metamaterial beam attached with multiply local resonators connected by actively tunable piezoelectric springs. The Euler–Bernoulli beam theory and Timoshenko beam theory are applied in the theoretical analysis of the system. Further, the spectral element method is utilized to analytically compute the dispersion relation and transmission ratio and excellent agreement with reference to the benchmark is reported. The influences of an external axial force on the bandgap range and attenuation behavior are further studied. Subsequently, the effect of resonator number and mass on the local resonance bandgap structure is investigated in two parametric studies. The active control of bandgap range and frequency is then verified. By analyzing frequency response function, the tunable transmission ratio of a supercell can be observed. To conclude, this paper not only provides a guideline for designs of wave attenuation with multiple frequency regimes in a one-dimensional system, but it can also be extended to sub-wavelength wave manipulation designs. [ABSTRACT FROM AUTHOR]

The performance of neutral‐point‐clamped (NPC) converters is subject to the regulation of neutral point balance. In the literature, researchers have addressed two main modulation methods: the active space vector PWM (SVPWM) technique and the virtual SVPWM (VSVPWM) method. However, those two approaches respectively suffer from reduced DC‐link voltage utilization and poor active regulation capability. To address this, an improved VSVPWM modulation scheme with actively strong voltage regulation capability is proposed in this paper. The fast and precise control of capacitor voltages is achieved by optimizing the synthesis scheme of the virtual vectors. When there is a voltage imbalance, the proposed technique can quickly restore and maintain the capacitor voltage balance till the full DC‐link voltage utilization without affecting the converter output quality. The experimental validation results on the NPC converter have demonstrated the benefits of the proposed active VSVPWM method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this manuscript, a novel four-dimensional hyperchaotic system is introduced. The dynamical properties of the proposed system are examined. A linear active control approach is established and necessary conditions are derived for synchronizing hyperchaotic systems. A new algorithm for generating one time passwords (OTPs) is developed by utilizing the proposed hyperchaotic system. The effectiveness of the suggested techniques are demonstrated through numerical simulations. [ABSTRACT FROM AUTHOR]

This paper endeavors to tackle the issue of horizontal vibrations encountered in high-speed and ultra-high-speed elevator cabins during operation. Given the limitations of traditional passive-control guide shoes in effectively mitigating these vibrations and the complexity and cost associated with active control systems, a novel approach involving passive-control rolling guide shoes (PCRGS) integrated with hydraulic damping is explored. The PCRGS incorporates a hydraulic actuator and hydraulic damping, which can be modeled by a mechanical and hydraulic co-simulation model using AMESim2020 software. The simulation reveals a substantial reduction in cabin vibrations equipped with PCRGS. Specifically, under pulse excitation, the reduction ranges from 26.2% to 27.5%; under white noise excitation, it varies between 14.3% and 17.1%; and under sine wave excitation, the reduction spans 21.2% to 24.1%. Notably, the system meets the stringent 'Excellent' (<=0.07 m/s2) performance criteria under sine wave excitation at lower frequencies, signifying its high effectiveness. These findings not only underscore the potential of hydraulic passive-control guide shoes in mitigating elevator vibrations but also provide invaluable guidance for their further development and refinement. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive for Locomotives is the property of Electric Drive for Locomotives Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to control the vibrational behavior of an auxetic plate coated with magnetostrictive material. The kinematic relations of the plate, rested on a Winkler–Pasternak medium, are expressed based on the first-order shear deformation theory (FSDT). The governing equations are derived by employing the Hamilton's principle and solved analytically by applying the Navier's method. The effects of various parameters such as auxetic inclination angle, auxetic rib length, and feedback gain, on the control behavior of the system are monitored in detail. In order to exhibit the accuracy and validity of this study, our results are compared to those available in the literature. The results indicate that adding auxetic core to magnetostrictive plate results in increasing dimensionless natural frequency. The results obtained from this study can potentially contribute to the advancement of various applications such as the design and improvement of sensors, actuators, and vibration cancellation systems. Additionally, the obtained results could serve as a foundational basis for subsequent investigations. [ABSTRACT FROM AUTHOR]

In response to the issues of vibrations affecting the construction safety, speed, and accuracy of suspended structures due to dynamic disturbances during lifting, environmental disturbances, and improper operator actions, this paper investigates the application of the Active Rotary Inertia Driver (ARID) system for double-rope suspended structures, namely analyzes, and applies control to the vibration response of double-rope suspended structures under external excitations. Taking the double-rope suspended structure as an example, a dynamic analytical model of the double-rope suspended structure is established based on D’Alembert’s principle. Through shake table tests, the dynamic response characteristics and vibration control effects of the double-rope suspended structure under various external excitations are studied, and the influence of the twisting radius of the suspended structure on the control effect is analyzed. The experimental results show that the ARID control system achieves significant control effects on the swing and torsional vibrations of the suspended structure, which validates the accuracy of the theoretical model for the ARID control system and demonstrates its feasibility for practical applications. [ABSTRACT FROM AUTHOR]

Emergency medical diseases (EMDs) are the leading cause of death worldwide. A time‐to‐death analysis is needed to accurately identify the risks and describe the pattern of an EMD because the mortality rate can peak early and then decline. Dose‐ranging Phase II clinical trials are essential for developing new therapies for EMDs. However, most dose‐finding trials do not analyze mortality as a time‐to‐event endpoint. We propose three Bayesian dose‐response time‐to‐event models for a secondary mortality analysis of a clinical trial: a two‐group (active treatment vs control) model, a three‐parameter sigmoid EMAX model, and a hierarchical EMAX model. The study also incorporates one specific active treatment as an active comparator in constructing three new models. We evaluated the performance of these six models and a very popular independent model using simulated data motivated by a randomized Phase II clinical trial focused on identifying the most effective hyperbaric oxygen dose to achieve favorable functional outcomes in patients with severe traumatic brain injury. The results show that the three‐group, EMAX, and EMAX model with an active comparator produce the smallest averaged mean squared errors and smallest mean absolute biases. We provide a new approach for time‐to‐event analysis in early‐phase dose‐ranging clinical trials for EMDs. The EMAX model with an active comparator can provide valuable insights into the mortality analysis of new EMDs or other conditions that have changing risks over time. The restricted mean survival time, a function of the model's hazards, is recommended for displaying treatment effects for EMD research. [ABSTRACT FROM AUTHOR]

Piezoelectric transducers are used within smart structures to create functions such as energy harvesting, wave propagation or vibration control to prevent human discomfort, material fatigue, and instability. The design of the structure becomes more complex with shape optimization and the integration of multiple transducers. Most active vibration control strategies require the tuning of multiple parameters. In addition, the optimization of control methods has to consider experimental uncertainties and the global effect of local actuation. This paper presents the use of a Deep Reinforcement Learning (DRL) algorithm to tune a pseudo lead-lag controller on an experimental smart cantilever beam. The algorithm is trained to maximize a reward function that represents the objective of vibration mitigation. An experimental model is estimated from measurements to accelerate the DRL's interaction with the environment. The paper compares DRL tuning strategies with H 2 and H ∞ norm minimization approaches. It demonstrates the efficiency of DRL tuning by comparing the control performance of the different tuning methods on the model and experimental setup. [ABSTRACT FROM AUTHOR]

Active yaw dampers (AYDs) show promise in addressing the carbody and bogie hunting issues of high-speed rail vehicles. However, the bifurcation behaviour under active control and the control law for hunting instability still require investigation. This study presents a comprehensive description of the linear control law, which can be simplified to various schemes, including skyhook damping, groundhook stiffness, modal, and blended schemes. The bifurcation behaviour under active control was analysed using a simplified lateral-dynamics-intended seven DOFs vehicle model and verified using a 3D full DOFs model in SIMPACK. Besides the well-known Hopf bifurcation, results also revealed a branching point (BP) and two new stable asymmetric equilibria. Although the asymmetric equilibria born through BP are stable, BP bifurcation should still be avoided for wheel flange contact and derailment concerns. Possible control laws are explored for two hunting scenarios: carbody hunting and bogie hunting. For carbody hunting cases, the control force can be either a linear function of bogie yaw displacement or a linear weighting function of bogie lateral and carbody roll velocity. The dominant frequency of the actuated force falls below 2 Hz, with a peak of 1.6 kN, and the allowable time delay is 70 ms. For bogie hunting cases, the control force can be a linear function of either bogie yaw displacement or velocity. In other words, both the groundhook stiffness and damping strategy are applicable. However, the actuated force contains several relatively high-frequency components (6∼13 Hz), which poses challenges to the control system and actuators, and the allowable time delay is relatively small. [ABSTRACT FROM AUTHOR]

The primary goal of this research is to lessen the high vibration that the model causes by using an appropriate vibration control. Thus, we begin by implementing various controller types to investigate their impact on the system's reaction and evaluate each control's outcomes. The controller types are presented as proportional (P), proportional-integral (PI), and proportional-integral-derivative (PID) controllers. We employed PID control to regulate the torsional vibration behavior on a dynamical system. The PID controller aims to increase system stability after seeing the impact of P and PI control. This kind of control ensures that there are no unstable components in the system. By using the multiple time scale perturbation (MTSP) technique, a first-order approximate solution has been obtained. Using the frequency response function approach, the stability and steady-state response of the system at the primary resonance scenario ( Ω 1 ≅ ω 1 , Ω 2 ≅ ω 2 ) are considered as the worst resonance and addressed. Additionally examined are the nonlinear dynamical system's chaotic response and the numerical solution for various parameter values. The MATLAB programs are utilized to attain simulation outcomes. [ABSTRACT FROM AUTHOR]

AbstractIn this paper, we study the propagation of surface waves on an A-shape metasurface, whose structure of the unit-cell is composed regularly of an A-shape surface column (made of steel), a thin magnetorheological plate and a soft thick rubber base. On the basis of the commercial program COMSOL Multiphysics, finite element method (FEM) analyses are carried out. The localization of elastic waves surrounding the surface allows surface waves to be distinguished among various complex wave modes. By adjusting the geometry, the A-shape surface column can be transformed from snowflake to A-shape. Owing to the C3v symmetry system, a Dirac cone of surface wave is observed in a snowflake metasurface. When the surface column changes to A-shape, the C3v symmetry is broken, making the Dirac cone vanish and a new band gap of surface waves arise. The band gap can be opened or closed by changing a geometric parameter, which determines the shape of the surface column changing from gadarene A-shape to snowflake or even upturned A-shape. Furthermore, we discover that although the topological phases of the gadarene A-shape and upturned A-shape metasurfaces are opposite, they share overlapped band gaps. Based on this phenomenon, we design a topological insulator for surface waves, whose super-cell is composed of gadarene A-shape units and upturned A-shape units. Through the calculation of the super-cell band structure, we observe the topologically protected interface states (TPISs). Subsequently, we design several waveguides whose paths are controllable. Up to now, most of the existing metasurfaces are made of passive materials, whose properties cannot be adjusted in real time, making them inconvenient for engineering applications when external conditions are changed. Therefore, we use tunable magnetorheological elastomer (MRE) to control the properties of the topological insulators. The stiffness of the surface layer can be converted by applying a magnetic field, which makes the topological metasurface controllable. These intelligent topological insulators may find important applications in the design of surface acoustic wave (SAW) devices. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic equation of a rigid body coupled with two flexible beams was established, considering the rotational motion of the rigid body and the elastic deflection of the flexible beams. The coupling effect between the rigid body rotation and flexible beam vibration was studied in detail. The dynamic response of the flexible beam with piezoelectric effect was established based on Hamilton’s principle. Under the premise of ignoring the nonlinear vibration coupling term of flexible beams, only the first two modes of transverse displacement and one directional rotation motion were studied in case studies. It was found that the coupling term caused by rigid body rotation can slightly alter the natural frequency and amplitude of flexible beams, mainly reflected in the first-order mode. With increasing the external excitation on the rigid body, the induced transverse displacement at the tip of the flexible beam increased significantly. Meanwhile, when the flexible beam was under external excitation, the vibration could also induce rigid body rotation. With the inverse piezoelectric effect, one may actively actuate the flexible beam vibration and rigid body rotation or control the undesired motion of the system. The control effect can be adjusted by varying the applied voltage excitation on the piezoelectric patches as well as patch positions. The conclusions drawn from this study can be applied to active precise control of space facilities such as satellites. Based on the dynamic modeling of rigid–flexible multi-body systems, this paper completed the study of the coupling effects of rigid body rotation and flexible body vibration, and proposed an application idea for completing small-angle maneuvers of rigid–flexible multi-body systems through piezoelectric control. [ABSTRACT FROM AUTHOR]

Hybrid Foil Magnetic Bearings (HFMBs) are a promising bearing technology for high-speed, oil-free turbomachinery that structurally embeds a gas foil bearing (GFB) into the inner diameter of an active magnetic bearing (AMB). The flexible foil structure provides sufficient support stiffness for the rotor, while closed-loop control allows real-time adjustment of the dynamic performance of the bearing. In this paper, the static and dynamic performance of the HFMB is measured experimentally. The effect of the control gain on the static and dynamic performance of the HFMB is highlighted. The proportional gain increases the stiffness but weakens the stability of the system, while the differential gain increases the damping but unexpectedly increases the stiffness. The static and dynamic performance of the HFMB is compared with that of the GFB. At low excitation frequencies, the stability of the GFB is higher than that of the HFMB, while as the excitation frequency is increased, the stability of the HFMB exceeds that of the GFB. [ABSTRACT FROM AUTHOR]

In this paper, we construct a new 4 - D hyperchaotic system with a nonlinear term in the form of an exponential function. The system is derived from a modified 3 - D Lü system. Firstly, we discuss the qualitative properties of the proposed system, using tools such as hyperchaotic attractors, symmetry, dissipation, equilibrium points, and Lyapunov spectrum for analysis. Next, we present an adaptive controller for stability analysis of the system. An active controller is designed to achieve complete synchronization between two identical systems. All stability results are established using Lyapunov stability theory. Finally, numerical examples and computer simulations are provided to illustrate the main results. [ABSTRACT FROM AUTHOR]

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The diversity and practicability of terahertz metamaterials have experienced rapid development in the past decade due to the increasing demand for various devices. This topic has attracted significant interest from researchers. Among the key functional devices in terahertz metamaterial systems, the active control ability of terahertz metamaterials is highly valuable and captivating. This implies that the electromagnetic properties of metamaterials can be modulated over a wide dynamic range by external stimuli. This review categorizes the different types of tunable terahertz metamaterials based on the external stimuli to which they respond, namely, mechanical modulation, electrical modulation, magnetic modulation, and optical modulation. Mechanically modulated devices offer simple yet efficient modulation, while electrical and magnetic modulation provide effective active modulation through electrical mechanisms. Optical modulation, in contrast, focuses on incorporating various materials to achieve active modulation. [ABSTRACT FROM AUTHOR]

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This paper presents the design, modeling, and characterizing tests of an assembled freely pendulum-type active tuned mass damper (AP-ATMD) for structural vibration control, highlighting its unique features such as noncontact force transmission, nonextra stiffness, and damping members. This device can operate passively as a tuned mass damper (TMD) with optimal tuning when environmental disturbances are minimal, or it can engage efficiently in active control when significant disturbances are present. The AP-ATMD mainly consists of a robust suspension system, an arc-shaped mass block with permanent magnets (PMs), and an arc-shaped electromagnetic motor. Notably, both the electromagnetic motor and the mass block have identical curvatures. A laboratory prototype of the AP-ATMD was designed and fabricated for the purpose of characterizing tests. Furthermore, an electromechanical model based on the Bouc–Wen hysteresis loop was developed to accurately characterize the active force behavior generated by the device. The parameters of this model were identified through a series of characterizing tests of the prototype AP-ATMD under harmonic excitations, and subsequently were validated under random excitation. The results confirmed the efficacy of the proposed electromechanical model in precisely capturing the active force behavior across a wide array of operational conditions. Finally, a numerical simulation of a 3-story frame with the AP-ATMD installed was conducted. The outcomes of the simulation highlighted the AP-ATMD's ability to reduce structural responses significantly. Moreover, the system employing the proposed electromechanical model outperformed a linear model, demonstrating a superior reduction in structural response. [ABSTRACT FROM AUTHOR]

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