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The control algorithm could greatly help the suspension system improve the comprehensive performance of the vehicle. Existing control methods need to obtain the intermediate states, which are difficult to obtain directly or accurately when estimated by filters or observers. Thus, this paper proposed a new practical finite state LQR control method to deal with this problem. By combining with the output state of the finite sensor of the vehicle suspension system and weakening the unknown state as the goal, an optimization model is established with the design variables as the LQR weight coefficients. Then, the direct relationship between the current control input and the finite sensor output is obtained, and the finite state LQR control is realized. Taking the quarter-car suspension model as an example, the corresponding noise is added considering sensor accuracy, and the control performance of the four control methods is studied considering the uncertainties of suspension system parameters. In addition, the acceleration of sprung mass and the dynamic travel coefficient of suspension have been separately calculated by methods of finite state LQR control, LQR control, and PID control. The results show that there is not much difference between them under shock excitation or random excitation. However, the finite state LQR control method has the best comprehensive control performance in that its dynamic tire load coefficient is better than other methods; it could take into account the suspension work stroke coefficient, dynamic tire load coefficient, and sprung mass' acceleration of the vehicle suspension system at the same time. In order to realize the optimal control effect with limited sensor arrangement, the finite state LQR control method only needs to obtain the current sensor output and the current control input, without estimating the unknown intermediate state. By this means, the proposed control method greatly simplifies the design of the control system and has great advantages on practical value. [ABSTRACT FROM AUTHOR]

The outer skins of aerospace structures, which are frequently experiencing variations of temperature, are threatened by thermally induced vibration. Vibration in space has dangerous effects on the safety of structures and may result in structural failure. So, the construction of an active control system to suppress thermally induced vibrations is necessary. Active thermally induced vibration control of homogenous isotropic beams, and plates through magnetostrictive layers are presented here. Negative velocity feedback with a constant gain is employed to make appropriate strain in the magnetostrictive actuator layer. Ultimately, a closed-form solution is presented for thermally induced vibration control of the hybrid magnetostrictive-Aluminum beams and plates. Effects of material properties, thickness of magnetostrictive layers, and control gain on vibration suppression have been evaluated. [ABSTRACT FROM AUTHOR]

Active vibration controllers are designed to mitigate chatter vibrations and increase the productivity of machines. Such controllers, however, often do not perform well in real applications if uncertainties are present in the system. In this study, a controller design is presented for a test configuration, where the actuation is utilized by an electromagnetic actuator. The robust stability charts, which take into account the bounded uncertainties in the measured frequency response functions (FRFs), are calculated in frequency domain using the zero-order approximation method. The predictions for the experimental configuration are validated in cutting tests. [ABSTRACT FROM AUTHOR]

Residual compressive stress can effectively improve fatigue the life of aerospace thin-walled parts. In this study, residual compressive stress control is taken as the target. Firstly, a surface residual stress prediction model is proposed, which considers both machining parameters and milling force heat. The model of the relationship between milling force, thermal load, and residual stress is established, which quantifies the effects of mechanical and thermal loads on the formation of residual compressive stresses. The results show that the feed rate of each tooth and the cutting-edge radius play an important role in the residual compressive stress of the milling surface. The prediction models of surface residual stress for thermal load, mechanical load, feed per tooth, and radius are established. Secondly, the ratio α of the feed rate per tooth fz to the cutting-edge radius r is quantified. When αxx = 0.42–0.65 and αyy = 0.36–0.7, the surface residual compressive stress in the x and y directions of the workpiece reaches the maximum value. Thus, the ratio of the feed rate per tooth fz to the cutting-edge radius r is optimized to control the mechanical and thermal load quantization. It realizes active control of residual compressive stress on the workpiece surface. [ABSTRACT FROM AUTHOR]

An active type of upgraded tuned liquid column damper (AUTLCD) based on hedge-algebras (HA) theory is proposed to mitigate structural vibrations of seismic-excited buildings in this paper. The AUTLCD consists of an upgraded tuned liquid column damper (UTLCD) and an actuator to generate the control force, in which UTLCD is constituted by a traditional tuned liquid column damper (TLCD) fixed on an undamped tuned mass damper (TMD). In this study, the HA-based-on controllers are used to determine the value of control force through the state variables, including the displacement and velocity of the floor installing the actuator. This approach allows one to find the optimal parameters of UTLCD and the HA-based controller. The balancing composite motion optimization (BCMO), a novel and potential algorithm, is utilized for optimization problems in the paper. The effectiveness of AUTLCD is compared with an active tuned liquid column damper (ATLCD) having the same weight as the AUTLCD. The results obtained from this research indicate that AUTLCD is more effective than ATLCD for aspects of control performance and average control force. Furthermore, although the optimal HA controller is only designed for the El Centro earthquake data in 1940, it still offers a high-efficiency level for many other earthquakes. In addition, the HA-based controller also makes sure the system's stability in the operating process. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing 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.)

To change the present situations of the low energy conversion efficiency, a new type hopping robot was proposed. The basic thought was to control the energy storage and release by non-circular gear meshing. Based on the principles of robot mechanisms, the main structure of the hopping robots was built. Motion principle was analyzed and motion procedure of the hopping robots was developed. According to the pre-given key parameters of energy conversion curve, pitch curves of non-circular gears were investigated by exploring the energy conversion curves, while hopping properties of hopping robots were revealed by exploring meshing properties of non-circular gears. The mathematical models of non-circular gear transmission were established. A detailed introduction about the deign processes of non-circular gears was given by using examples. Using 3D printing technique, the robot prototype was developed, and the experiments for hopping robots were carried out. The results confirm that the stable hopping may be realized, and the experimental results are close to the pre-given values. [ABSTRACT FROM AUTHOR]

Based on passive heat and mass transfer enhancement technology, a control method combining a cylindrical obstacle and a flexible beam was proposed to improve heat transfer performance in a microchannel. The optimal layout of a flexible beam was investigated under varying inclination angles of the beam and its spacing distances to the cylindrical obstacle through two-dimensional simulations of heat transfer, fluid and solid interaction. The control mechanism of the flexible beam was qualitatively analyzed from views of flow pattern and structural vibration. It was found that the pressure loss and heat flux should be considered simultaneously, to achieve the best performance of the heat transfer. Results showed that optimal performance occurred when the inclination angle of the beam and its spacing distance to the cylinder took specific values. In such circumstances, the flexible beam's vibration was amplified by the periodic vortex shedding from the upstream cylinder, without introducing too large a blocking effect. The appropriate control strategy of fluid-structure interaction can enhance the disturbance of the thermal boundary layer and result in the largest thermal enhancement factor. [ABSTRACT FROM AUTHOR]

With development of distributed generation (DG), configuration of optimization equipment is crucial for absorbing excess electricity and stabilizing fluctuations. This study proposes a two-layer configuration strategy coordinates active cyber control and the physical energy storage (ES) system. First, an upper economic model is developed. Based on chanceconstrained programming, an operation model accounts for inherent uncertainty are then developed. Under constraint of voltage risk level, a lower operation model is developed. Finally, a solution based on differential evolution is provided. An IEEE 33 bus system simulation was used to validate efficacy of model. The effects of risk level, equipment price, and chance-constrained probability were analyzed, providing a foundation for power consumption and expansion of cyberphysical systems. [ABSTRACT FROM AUTHOR]

In this paper, the dual combination–combination hybrid synchronization (DCCHS) scheme has been investigated in fractional-order chaotic systems with a distinct dimension applying a scaling matrix. The formulations for the active control have been analyzed numerically using Lyapunov's stability analysis in order to achieve the proposed DCCHS among the considered systems. With the evolution of time, the error system then converges to zero by applying a suitably designed control function. The proposed synchronization technique depicts a higher degree of complexity in error systems, and therefore, the DCCHS scheme provides higher protection for secure communication. Mathematical simulations are implemented using MATLAB, the results of which confirm that the proposed approach is superior and more effective in comparison to existing chaos literature. [ABSTRACT FROM AUTHOR]

The active control of flow past an elliptical cylinder using the deep reinforcement learning (DRL) method is conducted. The axis ratio of the elliptical cylinder Γ varies from 1.2 to 2.0, and four angles of attack α = 0°, 15°, 30°, and 45° are taken into consideration for a fixed Reynolds number Re = 100. The mass flow rates of two synthetic jets imposed on different positions of the cylinder θ1 and θ2 are trained to control the flow. The optimal jet placement that achieves the highest drag reduction is determined for each case. For a low axis ratio ellipse, i.e., Γ = 1.2, the controlled results at α = 0° are similar to those for a circular cylinder with control jets applied at θ1 = 90° and θ2 = 270°. It is found that either applying the jets asymmetrically or increasing the angle of attack can achieve a higher drag reduction rate, which, however, is accompanied by increased fluctuation. The control jets elongate the vortex shedding, and reduce the pressure drop. Meanwhile, the flow topology is modified at a high angle of attack. For an ellipse with a relatively higher axis ratio, i.e., Γ ⩾ 1.6, the drag reduction is achieved for all the angles of attack studied. The larger the angle of attack is, the higher the drag reduction ratio is. The increased fluctuation in the drag coefficient under control is encountered, regardless of the position of the control jets. The control jets modify the flow topology by inducing an external vortex near the wall, causing the drag reduction. The results suggest that the DRL can learn an active control strategy for the present configuration. [ABSTRACT FROM AUTHOR]

The research focuses on the active control scheme of a fully-developed turbulent boundary layer (TBL) forced by the submerged synthetic jet, and the particle image velocimetry (PIV) system is used to capture the two components velocity signals in the flow field. The mean velocity profiles near the wall obtained by the single-pixel ensemble correlation (SPEC) algorithm evidence the decline of streamwise velocity gradient, indicating the reduction of skin-friction drag. The deficit of streamwise velocity as well as turbulence attenuation in the cross flow attests that the perturbation effects are persistent in a certain range downstream of the synthetic jet injection section. The spatial topologies of the coherent structures detected by the improved quadrant splitting method (IQSM) reveal that the sweep events, responsible for the significant wall friction, are repressed under the action of synthetic jet. By employing the method of two-point correlation, destruction of the near-wall streaks is observed, and the control mechanism acts in a way to suppress the extension along the streamwise direction of the correlation coefficient. Based on the linear stochastic estimation, it is inferred that the influence of force is such the near-wall hairpin vortex detaches from the wall, and its ability to induce environmental fluid is vastly weakened. [ABSTRACT FROM AUTHOR]

There are three motion stages for an industrial robot manipulator, including the acceleration stage, the constant velocity stage, and the deceleration stage. Aiming at reducing the residual vibration of the manipulator after the movement of the deceleration, a new method is proposed by configuring the movement parameters of the flexible manipulator. Firstly, we conduct experiments to verify a numerical vibration model of the manipulator, and then, we analyze the vibration suppression effect under different conditions based on the numerical model. The results show that in the range of one movement, the residual vibration can be well suppressed when the acceleration and deceleration time are set as a positive integer to the natural period of the manipulator operation; otherwise, the vibration suppression effect is not obvious and proportional to the difference between the acceleration/deceleration time and the manipulator natural period. [ABSTRACT FROM AUTHOR]

When exposed to fluid flow, elastically supported multiple square cylinders may experience either one or a combination of vortex-induced vibration, galloping, and wake-induced vibration phenomena. Due to these high-amplitude instabilities, it is necessary to utilize vibration control devices. The present paper studies the suppression of flow-induced vibration (FIV) of tandem-arranged square-section cylinders, which can oscillate independently in the streamwise and transverse directions at low Reynolds numbers. The vibration reduction is achieved by directly applying opposing forces using an active FIV control system based on the intelligent proportional-integral-derivative controller. In the present study, the fluid flow equations are calculated through the finite volume technique, by which the aerodynamic forces are attained. Next, based on the computed excitation forces, the motion equations of cylinders are solved within a user-defined function code. The numerical results show that the controller successfully suppresses the vibrations of the front and rear cylinders by a maximum of 94% and 92% at Re = 80 and by 98% and 97% at Re = 100. At Re = 230 and 250, the controller successfully diminishes the oscillation of the front cylinder by a maximum of 79% and 80%, respectively. The significant intensity of the front cylinder's wake makes the active control system unable to capably affect the vibrations of the downstream cylinder at Re = 230 and 250. [ABSTRACT FROM AUTHOR]

Variable volume Helmholtz resonator systems offer an advantage for trim adjustment active control in liquid rocket engines due to the low bandwidth requirement on the actuator. In the present work, a trim adjustment active control system based on twin variable volume Helmholtz resonators is investigated experimentally in open loop on a dedicated test setup. It is found that the twin variable resonators can control combustion noise in open loop in a methane-air combustion chamber. The frequency at which acoustic absorption is optimum deviates significantly from the fundamental system frequency at some of the equivalence ratios studied. This happens when the correlation for impedance available in the published literature is used as such. In this work, the impedance characteristics were derived directly from the measurements. It is demonstrated from the impedance characteristics that the twin resonator system is able to achieve consistently better performance than a single resonator over a range of equivalence ratios. It is concluded that the twin resonator system concept stands validated in open loop for combustion noise. A practical scheme for implementing a twin resonator active control system in open loop is outlined. The results indicate that twin resonators should be further investigated for closed loop suppression of thermoacoustic instability. [ABSTRACT FROM AUTHOR]

Thermoacoustic instabilities occur when heat release is coupled with pressure fluctuation, which may cause performance degradation of the combustor and serious structural damage. This study focued on an active control method using discharge plasma and showed experimentally that discharge plasma can make a difference in controlling the thermoacoustic instabilities in a Rijke tube. A vertically placed Rijke tube thermoacoustic system using induction heating tungsten mesh as a heat source was built. The results show that the high repetition rate discharge can effectively suppress the thermoacoustic oscillations in the Rijke tube and that they will not re-occur for some time. Additionally, their effectiveness depended more on average power than energy per pulse. Combining the collected pressure, schlieren data, and theoretical analysis, it can be suggested that the plasma discharge could heat the inlet airflow, which could influence the heat exchange and then could break thermo-acoustic coupling, and its high-frequency pressure perturbation might increase the dissipation of the energy of sound. [ABSTRACT FROM AUTHOR]

The feature of constructing a power supply system for the mechanisms of own needs of nuclear power plants is reflected. It is noted that the emergency power supply system of power units should provide power supply to consumers in all operating modes of the station, including in the event of loss of working and backup power sources from the power system. The paper shows that thanks to intelligent distribution technologies, the widespread use of distributed generation sources, the NPP's own network can be converted from passive to active. The integration of distributed generation, including renewable distributed generation, changes the flow of energy in the grid from unidirectional to bi-directional. A diagram of the possible application of these devices in the emergency power supply system of a nuclear power plant is proposed. Hybrid hierarchical control is recommended as the most effective method of active control of the emergency power supply system. This will allow widespread use of modern controllers, power electronics for DC / DC, DC / AC conversions and software adapted for small distributed generation.

A strip speaker is the simplified panel speaker adopting a thin beam as the radiator, which is operated under the traveling-wave control method (TCM) with three actuators. The structural resonances are suppressed fundamentally by nullifying the reflected bending waves near the boundary, thus radiating a smooth sound spectrum in a wide frequency band. This study develops the design guidelines for such TCM-controlled strip speakers by investigating the effect of design variables on acoustic performances, such as the effective frequency range and the radiation efficiency. To this end, the acoustic performances are normalized by the size and physical properties of the beam so that a parametric study in the normalized domain can generalize the conditions for the desired acoustic performances. The result shows that the effective frequency range becomes wider when the beam material has a fast wave speed, and the radiation efficiency is enhanced as the beam density decreases. It is found that the two acoustic performances require a trade-off in selecting the actuator location and beam thickness. The suggested design procedure is validated using acrylic and aluminum beams having the same size. The aluminum beam has a faster wave speed, thus covering the effective bandwidth of 5800 Hz, 2.5 times wider than the acrylic case. On the other hand, the acrylic beam has five times higher radiation efficiency due to its low density. As a result, one can select the dimension and material of the beam appropriately to achieve the desired acoustic performance by using the suggested design method.

In this paper, a state-of-the-art literature review is presented emphasising on the development of control variants for mass damper schemes on building-like structures. Additionally, a systematic literature review is conducted addressing three relevant questions: What type of mass damper is preferable by the associated industry? How are mass dampers distributed around the world? Is industry following research? Through the systematic literature review, updated lists of mass damper implementations and control algorithm applications in real-life structures were compiled. 208 case-studies are discussed in total. It is found that, 63% of them refer to passive tuned mass dampers, 31% to hybrid mass dampers, 4.0% to active mass dampers and only 2% to semi-active mass dampers. Regarding control algorithms, controllers of 24 structures driving semi-active, active or hybrid mass dampers are presented. It is concluded that the industry considerably lags behind latest structural control research both regarding implementations and overall management.

A suitable initial point for understanding multiphase flows is a phenomenological description of the mechanism of geometric distributions or flow patterns that are observed. The challenge however is the prediction of the flow patterns for a combination of flow operating conditions and the characteristics of the phases as well as points of transition from one pattern to the other. Different flow patterns occur in different pipeline configurations for which U-shape risers are part. In the quest to stabilise unstable slug flow in the U-shape riser, an experimental study of gas-liquid flow mixture is conducted to understand the behaviour of the flow in the riser.This paper seeks to understand the flow dynamics in a 2-inch internal diameter U-shape pipeline riser system with much emphasis on unstable slug flow. The initiation of this flow instabilities in the U-shape pipeline riser system and the impact of the downcomer on the flow behaviour is investigated experimentally. Understanding the flow behaviour in the U-shape riser could help in developing effective control techniques to stabilise the multiphase flows in the flowlines. Experimentally, flow patterns observed from the U-shape pipeline riser configuration is used to develop a flow regime map which was then compared to that observed in literature and similarly to a purely vertical riser with similar pipe diameter. Thus, a slug envelope was developed for the U-shape riser to help identify which regions slugging could occur in the system.

The complex unsteady flow in cavities leads to the formation of large-scale disturbances in the shear layer. Natural closed-loop mechanisms provoke a dramatic increase in pressure pulsations and aerodynamic noise. This paper presents the experimental study of pressure fluctuations in closed-loop control in rectangular cavities using plasma dielectric barrier discharge. The flow velocity was 37 m/s, and the Reynolds number based on a cavity depth was approximately 120,000. The discharge ignition near the leading edge of the cavity provoked the shear layer restructuring. It was found that pressure fluctuations with an amplitude of 120 dB occur at frequencies 480 and 820 Hz. Frequency modulation of the discharge at resonant peaks was carried out by changing the phase shift of the power supply. The peak amplitude was reduced or increased by phase shifts from natural disturbances to forced ones. The optimum energy input was 50 W/m. This was three times less than the power consumption of the open-loop mode. The PIV visualization was organized in the phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity.

Targeting the problems of conventional active–passive hybrid vibration isolation systems, such as low output force, poor bearing capacity, large power loss and inability to withstand strong impacts, this paper proposes an active–passive hybrid vibration isolation system combining an electromagnetic actuator, rubber passive vibration isolator and magnetorheological damper. The overall design of the hybrid vibration isolation system is first introduced. Then, a two-dimensional electromagnetic frequency-domain simulation is carried out on the electromagnetic actuator to obtain the output characteristics. A three-dimensional modeling is conducted to simulate the electromagnetic–mechanical coupling in the time–frequency domain to obtain nephograms of the magnetic flux diffusion distribution and power loss. Then, a dynamic stiffness test is carried out on the rubber vibration isolator to obtain the dynamic stiffness characteristics and the damping angle curve. At the same time, an adaptive suppression filtered-x least mean square (ASFXLMS) algorithm is proposed to adjust the update of the control weight coefficients to ensure that the current signal does not exceed the effective operating range of the actuator when the electromagnetic actuator is subjected to strong external disturbances. Finally, a hybrid vibration isolation system-based active vibration isolation experimental platform is built, and multifrequency line spectra active–passive vibration isolation experiments are carried out. The results demonstrate that the hybrid vibration isolation system has good control effects in the time–frequency domain and shows good robustness when subjected to impact.

Recently, many novel results have appeared on the control-oriented design and analysis of active prostheses. This paper presents a review of recent advances in the control of robotic prostheses, with an emphasis on lower limb prostheses. Arm and hand prostheses are also included, to have a more comprehensive view of the prosthesis. It includes the most common control strategies and unconventional proposals, such as intelligent control methods. The design methods of sensors, actuators, and control strategy are also discussed, which allow one to achieve the desired behavior of the mechanisms. [ABSTRACT FROM AUTHOR]

The paper investigates a new hybrid synchronization called modified hybrid synchronization (MHS) via the active control technique. Using the active control technique, stable controllers which enable the realization of the coexistence of complete synchronization and anti-synchronization in four identical fractional order chaotic systems were derived. Numerical simulations were presented to confirm the effectiveness of the analytical technique. [ABSTRACT FROM AUTHOR]

A lack of curvature reduces the out-of-plane stiffness of cable net façades. Therefore, they may experience large deformations and severe damage under heavy vertical loads such as earthquakes and wind. Axially movable smart supports are proposed for controlling structural vibrations by controlling tension of the cables. The equation of motion of the cable net, controlled by the smart support, is developed following a finite element method based program to solve the equation. The linear quadratic regulator control strategy is utilized to find the optimal control gain. The results show that smart supports, especially when connected to the central cables, can significantly control the vibrational amplitude of the structure. [ABSTRACT FROM AUTHOR]

Due to the particularity of the structure, the dynamic properties of multiunit articulated rubber-wheel autonomous rail rapid transit system are very complex, which increases the difficulty of studying its braking stability. In this paper, a dynamic analysis model for the emergency braking of a multiunit articulated rubber-wheel autonomous rail rapid transit system is established by introducing the axle load transfer, suspension deformation compatibility equation, articulation force relationship equations, etc. Based on an in-depth analysis of the risks of the lateral swing instability and their formation mechanisms, an active control strategy for the multiunit articulated rubber-wheel autonomous rail rapid transit system under emergency braking conditions is innovatively proposed to ensure the stability of the vehicle, with the shortest braking distance as the optimization goal. Through simulation and experimentation, the established dynamic model is confirmed to approach the real vehicle well, and the feasibility of the active control strategy is proved. [ABSTRACT FROM AUTHOR]

The control–structure interaction (CSI) affects the performance and robustness of protective structures in active control system, and it is important to consider the CSI effect to achieve high performance in structural vibration control. In this paper, the electro-mechanical model of the torsional servomotor is derived by establishing dynamic voltage equilibrium equation. Three different active control models (non-CSI, reduced-order CSI, and higher-order CSI model) which considering different accuracy requirements of the electro-mechanical relationship are established to investigate the influence of the CSI on active tuned mass damper (ATMD) control system. The frequency- and time-domain responses of a three-story steel frame structure during different excitations are investigated, and as a comparison, the responses of the uncontrolled and tuned mass damper (TMD) control system are also studied. It can be concluded that the control performance of the active control system is reduced due to the CSI effect, especially at resonance frequency region of the structure (around 2.7 Hz, 8.2 Hz, and 13.2 Hz). The input voltage, velocity of the top floor, velocity of active mass, and higher-order of control forces have an important influence on the servomotor output control force. Furthermore, it can be found that, to achieve the same control effect, the required control voltage has been significantly increased due to the CSI effect. [ABSTRACT FROM AUTHOR]

Objectives University students experience heightened levels of stress and are seeking mental health services with increasing frequency. Mindfulness-based interventions (MBIs) may be an effective resource for managing stress. The present study examined the effectiveness of an MBI in reducing stress, anxiety, and rumination compared to active and traditional control conditions. Methods Undergraduate students at a southeastern university participated in either a 4-week MBI, active control, or traditional control condition. Measures were collected pre- and post-intervention. Results: Overall the MBI had a significant impact on perceived stress over and above both traditional and active control conditions. The MBI also had a significant impact on trait mindfulness and anxiety compared to the traditional control condition. No significant differences were observed for rumination. Conclusions: The MBI significantly impacted trait mindfulness, perceived stress, and state anxiety. MBIs may be a useful approach to successfully alleviating stress in a highly stressed population. [ABSTRACT FROM AUTHOR]

The boundary layer suction (BLS) has the merit of effectively suppressing the formation and development of separation vortices by removing low-momentum fluid occurs on the leading-edge of airfoil suction surface. The present paper numerically investigates the impacts of BLS on the aerodynamic performance of a horizontal axis wind turbine (HAWT). First, the dynamic mode decomposition method is adopted to gain an insight into the improvement mechanism of BLS control by analyzing the flow patterns of a two-dimensional S809 airfoil. Subsequently, the BLS is arranged on a NREL Phase VI reference turbine to study the power increment and flow field characteristics, and the effects of different working angles α s and momentum coefficients C μ are investigated at different tip speed ratios (TSRs). The results indicate that the use of BLS control can increase the pressure difference between the suction surface and the pressure surface, raise the peak negative pressure at the leading edge and shift the airfoil flow separation point backwards, and thus effectively enhance the stability of the flow field. Furthermore, the BLS control can significantly improve the power extraction at low to medium TSR if this active device is appropriately implemented on the HAWT. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of a simplified aircraft model with a pair of actively deformed membrane wings is investigated experimentally in this work. The active deformation is achieved with Macro fiber composite (MFC) actuators, which are attached to the upper surface of the wings and occupied 13.7% of the wing surface area. Wind tunnel experiments are conducted to evaluate the influence of membrane active deformation on the aerodynamic performance of the aircraft. The results show that the membrane deforms and vibrates under the actuation which can effectively suppress the leading-edge separation and facilitate the reattachment. Therefore, compared with the rigid wing model, the lift coefficient of the actively deformed membrane wing model is enhanced remarkably from the angle of attack of 7° to 22°. The stall angle is delayed by 2°, and a maximum lift coefficient enhancement of 32.5% is reached, which shows a wide potential application in improving the aerodynamic performance of modern aircraft. [ABSTRACT FROM AUTHOR]

This paper reviews various active control measures used for controlling the wind-induced vibration, which is a problem of great concern for long-span suspension bridges. Firstly, a brief discussion of passive control measures and their limitations is presented. Then, the development of active aerodynamic control and active mechanical control is comprehensively reviewed to present the characteristics and limitations of numerous control devices with emphasis on the control surfaces adopted for active aerodynamic control. Particularly, the existing challenges and suggestions for future studies are proposed for various countermeasures, especially for the control surfaces used in active control. It is expected that the information provided in this article will facilitate further research in the area of vibration control for long-span suspension bridges under various wind conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University of Engineering Science / Shanghai Gongcheng Jishu Daxue Xuebao is the property of Journal of Shanghai University of Engineering Science 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.)

In recent decades, quasi-zero stiffness (QZS) vibration isolation systems with nonlinear characteristics have aroused widespread attention and strong research interest due to their enormous potential in low-frequency vibration isolation. This work comprehensively reviews recent research on QZS vibration isolators with a focus on the principle, structural design, and vibration isolation performance of various types of QZS vibration isolators. The negative-stiffness mechanism falls into two categories by different realization methods: passive and active/semi-active negative-stiffness mechanisms. Representative design, performance analysis, and practical application are elaborated for each category. The results show that passive vibration isolation systems have excellent low-frequency vibration isolation performance under specific payload and design parameters, whereas active/semi-active vibration isolation systems can better adapt to different environmental conditions. Finally, the development trends and challenges of QZS vibration isolators are summarized, and the solved and unsolved problems are highlighted. This review aims to give a comprehensive understanding of the QZS vibration isolation mechanism. It also provides guidance on designing new QZS vibration isolators for improving their vibration isolation performance and engineering applicability. [ABSTRACT FROM AUTHOR]

In this article, a fuel tank is coupled with gyrostat in a moving spacecraft to discuss its dynamical behaviour and bringing stability in velocity vectors. Parametric study is performed using Hopf bifurcation to find the bifurcation parameter for a considered mechanical model. Furthermore, a region is constructed in which negligible limit cycles appear around unstable spirals for angular momentum greater than bifurcation point. Based on local dynamical analysis, trajectories of angular velocities are observed with respect to damping constant, which is formulated in the form of bifurcation parameter. Moreover, a controller is designed in this article for considered dynamical system by achieving global stability, with the help of Lyapunov theory, into the spacecraft coupled with filled fuel tank, and their results are compared with effective spacecraft control strategies to observe the effectiveness of our proposed control technique. Finally, in presented research, numerical simulations are performed using MATLAB for validation of analytical results, which the authors have achieved for Hopf bifurcation and designed controller.