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The transverse leaf spring (TLS) suspensions are a promising option for van vehicles due to their high load-carrying capacity and excellent handling stability. However, its ride comfort remains a major challenge. This paper investigates and compares the effects of semi-active and active control strategies to enhance the ride comfort of TLS suspensions. Firstly, a four-degree-of-freedom (4-DOF) half-car model and a multi-body dynamics (MBD) model of the TLS suspensions are established. The MBD model has higher accuracy and can describe the medium and high frequency characteristics of the TLS suspensions, such as the suspension offset frequency and the frequency response function of the body vertical acceleration (BVA). Therefore, based on the MBD half-car model with TLS suspensions, this paper proposes an optimal fuzzy PID active control strategy considering the left and right suspension coupling. The optimization objectives are the BVA, the left and right suspensions dynamic deflection, and the left and right wheels dynamic displacement. The integral absolute error is used as the evaluation criterion. The left and right fuzzy PID controllers' parameters are obtained through particle swarm optimization. Simulation results demonstrate that the particle swarm optimization fuzzy PID active control strategy effectively controls the low-frequency vibration of the TLS suspensions and suppresses the medium- and high-frequency vibration characteristics compared with the traditional skyhook semi-active control strategy. This technology provides a reference for improving the ride comfort of the TLS suspensions. [ABSTRACT FROM AUTHOR]

The automotive industry has transitioned from internal combustion engine (ICE) vehicles to electric vehicles (EVs) in recent years. Also essential to the development of the next generation are the enhancement of engine performance and production of lightweight vehicle bodies. Through this method, it is possible to increase vehicle output. However, as the vehicle's excitation strength increases, structural noise and vibrations caused by the engine increase. Intelligent structure-based active mounting systems are widely used in the automotive industry to reduce vibration and noise. It can continuously control the dynamic characteristics of the mount system, enabling real-time control of active mounting systems. When determining the position of the active mounting system, it must be installed in the most efficient position possible. Therefore, the purpose of this study is to determine the optimal placement criteria for an active mounting system consisting of a piezoelectric actuator and a rubber grommet. The lumped parameter model is used to model the plate structure with two hybrid mounting systems based on the source–path–receiver structure. In addition, the forces of two active mounts are calculated using static and dynamic approaches. When the calculated force on the hybrid mount system is relatively low, the location with the greatest vibration reduction can be determined, and this location can be regarded as the optimal location for the active mounting system. In addition, a feasibility test is conducted to validate the proposed criteria and validate the static and dynamic results. The findings indicate that the optimal location for the active engine mounting system can be determined. [ABSTRACT FROM AUTHOR]

Robotic Friction Stir Welding (RFSW) technology integrates the advantages of friction stir welding and industrial robots, finding extensive applications and research in aerospace, shipbuilding, and new energy vehicles. However, the high-speed rotational process of friction stir welding combined with the low stiffness characteristics of serial industrial robots inevitably introduces vibrations during the welding process. This paper investigates the vibration patterns and impacts during the RFSW process and proposes an active vibration avoidance control method for variable speed welding based on constant heat input. This method utilizes a vibration feedback strategy that adjusts the spindle speed actively if the end-effector's vibration exceeds a threshold, thereby avoiding the modal frequencies of the robot at its current pose. Concurrently, it calculates and adjusts the welding speed of the robot according to the thermal equilibrium equation to maintain constant heat input. A simplified dynamic model of the RFSW robot was established, and the feasibility of this method was validated through simulation experiments. This study fills the gap in vibration analysis of RFSW and provides new insights into control strategies and process optimization for robotic friction stir welding. [ABSTRACT FROM AUTHOR]

This is the first research on the smart control and frequency analysis of a cylindrical sandwich nanoshell in the framework of the numerical-based generalized differential quadrature method (2D-GDQM). The current sandwich smart nanostructure is made of a honeycomb core and piezoelectric face sheets as sensor and actuator (PFSA). For modeling the size-dependent nanoshell, nonlocal stress-strain gradient theory (NSGT) is presented. Also, this nanostructure is under conveying viscous fluid, and the related force is calculated by the modified formulation of Navier–Stokes. Also, the current structure rotates around its axial direction. The stresses and strains are obtained using the higher-order shear deformation theory (HSDT). The external voltage is applied to the sensor layer, and a Proportional-Derivative (PD) controller is used for sensor output control. Governing equations and boundary conditions of the cylindrical sandwich nanoshell are obtained by implementing Hamilton's principle. The results show that the geometry of honeycomb core, PD controller, velocity of fluid flow, length to radius ratio (L/R), and applied voltage and have a significant influence on the frequency characteristics of a cylindrical sandwich nanoshell. Another important consequence is that applying the PD controller leads to an increase in the critical velocity of fluid flow in the smart nanostructure. [ABSTRACT FROM AUTHOR]

Recently, active mounting systems have been applied to automotive engine mounts to effectively mitigate structure-borne vibrations throughout the vehicle chassis. Active mounting systems have been investigated extensively to alleviate the vibration and noise of automobiles; however, the actual engine mounting orientation is not considered, and only an extremely small range of specific vibration and noise control is examined. This paper presents the modeling, analysis, and control of a source structure with an active mounting system while considering the location and direction of actual automotive engine mounts. Two active mounts comprising a piezoelectric stack actuator arranged in series with an elastomeric mount are applied to mitigate both vertical and horizontal vibrations by setting a variable parameter via the dynamic relation of the source structure. When harmonic excitation forces are employed, the secondary force required by each active mount can be calculated mathematically, and a control signal is applied to reduce vibrations through destructive interference with the input signal. Simulation results show that the excitation vibration can be reduced using this bidirectional active mount. Hence, noise vibration harshness is expected to be improved by controlling the vibration of the actual automotive engine structure and the secondary force of actuators. [ABSTRACT FROM AUTHOR]

Flexible vibration has a great impact on flexible spacecraft attitude control, which will reduce the pointing accuracy of the spacecraft platform and bring severe challenges to the design of a high-precision attitude control system for flexible spacecraft. Aiming at the problem of attitude and vibration coupling control of flexible spacecraft, an anti-unwinding attitude coupling controller using the positive position feedback (PPF) control is proposed in this paper. The model compensation control term is constructed based on the prior information to improve the tracking performance. The proposed attitude coupling control method can effectively suppress the flexible vibration while achieving more accurate attitude control. The obtained closed-loop system under the proposed control scheme is asymptotically stable, which is proved by the Lyapunov stability theory. The numerical simulation illustrates that the proposed method can effectively improve the attitude control accuracy of the flexible spacecraft and is capable of large-angle attitude maneuver control because of its prominent performance in attitude tracking and its unwinding-free performance. • Coupling control for flexible spacecraft. • Active vibration control using positive position feedback. • Model compensation control term is constructed to improve the dynamic performance. • The obtained closed-loop system achieves the asymptotic stability and anti-unwinding performance. [ABSTRACT FROM AUTHOR]

In this paper, a ground-based experimental system for solar array active vibration suppression has been established. Firstly, in order to establish an accurate model of the solar array, the solar array is regarded as a flexible cantilevered thin plate, and the corresponding dynamical equations are derived using the absolute nodal coordinate method. In addition, in this paper, the more advanced MFC piezoelectric patch is used instead of the traditional PZT piezoelectric ceramic patch. The electromechanical coupling finite element model of the P1-type MFC patch is established and substituted into the kinetic equation of the solar array. Finally, the accuracy of the electromechanical coupling modeling and the control effect of active vibration suppression were verified using the PID control. A set of experimental frameworks for evaluating the active vibration suppression effect, including the free vibration test, sinusoidal perturbation test, and white noise perturbation test, as well as the analysis strategy of the test data, are established. [ABSTRACT FROM AUTHOR]

Aiming at the position coupling, gyroscopic effect, and synchronized vibration caused by the unbalance mass in the magnetic bearing rotor, a linear active disturbance rejection notch decoupling control method is proposed. Firstly, a model with coupling and unbalanced vibration of the system was established. The terms of position coupling, gyroscopic effect, and unbalanced vibration in the system are estimated by Extended State Observer and the estimator is treated as the system disturbance to be compensated, then the radially existing coupled and unbalanced vibration systems are decoupled into four independent second-order series-integrated subsystems. The nonlinear state error feedback control law is designed to implement the decoupling control of each subsystem. For the problem of unbalanced vibration of the rotor after decoupling, the suppression method of the dynamic unbalanced force of the same frequency notch filter is designed, and then the closed-loop feedback structure of the new method is deduced, and its frequency characteristics are analyzed. Then the rules and principles of controller parameter selection are summarized using Bode diagram. The simulation results show that the designed linear active disturbance rejection notch decoupling controller not only achieves the decoupling control of the respective degrees of the magnetic bearing rotor but also suppresses the unbalanced vibration of the rotor. At the same time, it solves the influence of the gyroscopic effect on the control under the high-speed running of the magnetic bearing rotor. [ABSTRACT FROM AUTHOR]

The vibration of piping systems is one of the most important causes of accelerated equipment wear and reduced work efficiency and safety. In this study, an active vibration control method based on a fractional-order proportional–integral–derivative (PID) controller was proposed to suppress pipeline vibration and reduce pipeline damage. First, a mathematical model of the distributed piping system was established using the finite element analysis method, and the characteristics of the distributed piping system were studied effectively. Further, the time-frequency domain parameter identification method was used to realise the system identification of the cross-point vibration transfer function between the brake and sensor, and the particle swarm optimisation algorithm was utilised to further optimise the transfer function parameters to improve the system identification accuracy. Therefore, a fractional-order PID controller was designed using the D-decomposition method, and the optimal controller parameters were obtained. The experimental and numerical simulation results show that the improved system identification algorithm can significantly improve modelling accuracy. In addition, the designed fractional-order PID controller can effectively reduce the system's overshoot, oscillation time, and adjustment time, thereby reducing the vibration response of piping systems. [ABSTRACT FROM AUTHOR]

In this study, we created an accurate model for a homogenous smart structure. After modeling multiplicative uncertainty, an ideal robust controller was designed using μ-synthesis and a reduced-order H-infinity Feedback Optimal Output (Hifoo) controller, leading to the creation of an improved uncertain plant. A powerful controller was built using a larger plant that included the nominal model and corresponding uncertainty. The designed controllers demonstrated robust and nominal performance when handling agitated plants. A comparison of the results was conducted. As an example of a general smart structure, the vibration of a collocated piezoelectric actuator and sensor was controlled using two different approaches with strong controller designs. This study presents a comprehensive simulation of the oscillation suppression problem for smart beams. They provide an analytical demonstration of how uncertainty is introduced into the model. The desired outcomes were achieved by utilizing Simulink and MATLAB (v. 8.0) programming tools. [ABSTRACT FROM AUTHOR]

The vibration and sound radiation characteristics of the submarine pressure hull structure are important performance indicators for the acoustic design of the submarine structure. In this paper, the spectral element method is used to analyze the vibration of the shell structure. Combined with the periodic structure theory, the theoretical calculation method of the periodic ribbed shell structure is deduced, and the analytical method that can be used to calculate the vibration of the pressure shell structure is established. The feasibility of applying the spectral element method to the vibration calculation of the pressure shell structure is verified by comparing the analytical calculation and the finite element simulation. The vibration characteristics test experiment of the actual submarine pressured hull structure is carried out. The results show that the theoretical analysis is correct. Highlights: The vibration and sound radiation characteristics of the submarine pressure hull structure have an important influence on the radiated noise of the submarine. A theoretical analysis method of vibration characteristics of pressure hulled based on spectral element method and periodic structure theory is proposed. The experimental study on vibration characteristics and active control of line spectrum of the pressure hull is carried out. [ABSTRACT FROM AUTHOR]

Vibration induced by marine power devices (MPD) transmitting to the hull structure is one of the most important factors that cause ship vibration and underwater sound radiation. Vibration isolation technologies (VIT) are widely applied to reduce the vibration transmission. However, the overweight issue of VIT for marine power devices is a currently challenging engineering problem. The current reserve of lightweight and high-efficiency VIT for MPD and relevant theoretical and design research are seriously insufficient. This article first elaborates the causes of the overweight problem of VIT for MPD: (1) failing to grasp the quantitative law; (2) single vibration suppression mechanism. Then, it systematically sorts out the technical methods and application examples with potential to solve the overweight problem, such as dynamic optimization design, lightweight material method, novel intermediate mass structures, distributed dynamic vibration absorbers (DDVAs), locally resonant structures (LRS), particle damping (PD), quasizero stiffness isolators (QZSI), and active vibration control (AVC) technologies. Finally, the future development of lightweight VIT for MPD is prospected. It can be used as a reference for marine vessel vibration attenuation research and engineering design. [ABSTRACT FROM AUTHOR]

The active vibration absorber represents an effective means to mitigate excessive vibrations in low-damping structures. Nevertheless, the dynamics of the actuators employed in such systems may negatively affect their performance and stability restricting their operational frequency range. This article presents an application of dynamics inversion techniques to the force control of electrodynamic proof-mass actuators employed as active vibration absorbers in lightweight pedestrian structures. The dynamics inversion approach is applied to enhance the classical direct velocity feedback scheme. Additionally, a novel method relying on dynamics inversion is presented: the Broadband Force Cancellation Algorithm. This procedure consists in estimating, in real-time, the equivalent force acting on the system to later apply it back to the structure with the opposed sign. The effectiveness of the proposed methods is assessed via numerical simulations carried over a realistic model of an existing lightweight footbridge and an electrodynamic proof-mass actuator. Two load cases are analyzed: a fixed swept-sine force and a walking load. Both cases account for the actuator-structure interaction. The human-structure interaction is considered in the latter scenario due to its importance when dealing with lightweight pedestrian structures. Simulation results demonstrate that the dynamics inversion techniques effectively cancel out actuator dynamics leading to an excellent tracking of the reference force output by the suggested or other vibration control algorithm. The proposed schemes are proved promising since they substantially outperform the widespread direct velocity feedback approach. In particular, the Broadband Force Cancellation Algorithm minimizes the action of the external forces within their estimation frequency range, thus being especially suited to tackle broadband excitations, important in lively pedestrian structures, whereas the velocity feedback methodology performs best at the structural resonant frequencies. [ABSTRACT FROM AUTHOR]

The primary focus of this study is to analyze the vibrational properties of a nanobeam with a porous structure, which is composed of a functionally graded material. Additionally, the nanobeam comprises a magnetostrictive substance known as Terfenol-D. The nanobeam is postulated to include three distinct layers, whereby the central layer is comprised of a magnetostrictive material, while the outside layers are built of functionally graded material. On the other hand, the use of higher-order parabolic shear deformation beam theory is utilized to get the kinematic relations. Moreover, Eringen's nonlocal theory is used to include the impact of small-scale phenomena. The governing equations are derived by the application of Hamilton's principle and then solved using analytical techniques. This study presents a thorough examination and elucidation of the influence exerted by several elements, such as aspect ratio, feedback gain, and gradient index, on the system being studied. Based on extant research, empirical evidence indicates that increasing the feedback gain results in a decrease in the natural frequencies. In order to establish the accuracy and dependability of our present study, we have undertaken a comparison examination of our results in relation to the existing body of the literature. The results of the present study have the potential to advance the understanding and progress in the field of nano-systems, namely nano-sensors and nano-actuators. [ABSTRACT FROM AUTHOR]

Although frequency-domain optimization approaches are commonly used for noise control, ubiquitous transient behaviors indicate that time-domain approaches cannot be ignored. Thus, this paper minimizes the transient noise radiated from the vibration system with constant gain velocity feedback (GGVF) control by combining topology optimization and parameter optimization. Based on the solid isotropic material with penalization (SIMP) model, the pseudo density is introduced to characterize the presence or absence of piezoelectric material. To satisfy engineering requirements, constraints on the usage amount of piezoelectric material, consumable energy, and maximum transient voltage are considered. Transient sound radiation is predicted by using a finite element/time-domain boundary element method (FEM/TDBEM). Sensitivity formulae of objective function to pseudo density and feedback gain are derived using a combination scheme. Namely, a direct method is applied to obtain the vibration sensitivity information at all boundary nodes, the results of which are input into the sensitivity calculation of transient sound radiation addressed by an adjoint variable method. This scheme integrates the advantages of the direct method which can calculate the vibration sensitivity of all nodes at once and of the adjoint variable method which has high computational efficiency. The gradient-based method of moving asymptotes (MMA) is employed to solve for optimised solutions. Numerical examples demonstrate the accuracy of the sensitivity formulae and the effectiveness of the concurrent optimization strategy. [ABSTRACT FROM AUTHOR]

The power unit on board the ship generates periodic low-frequency vibration that affects the normal operation of the equipment on board, and the adaptive feedforward control algorithm can effectively suppress such harmful vibration noise. But the adaptive feedforward control algorithm needs to obtain the identification model of the secondary channels, and the frequency domain least squares method based on the linear Extended auto-regressive model (ARX) is difficult to obtain the identification model with nonlinear characteristics. The nonlinear auto-regressive model (NARX) adds nonlinear mapping layers to the topology of the ARX model to enhance the identification capability of the NARX model for complex systems. In this paper, a block diagram of the Fx-LMS feedforward control algorithm based on the NARX model is proposed, then the initial parameters of the NARX neural network are optimized using the Quantum Particle Swarm Optimization (QPSO) algorithm and the secondary channel is identified, and the identification results show that the accuracy of identifying the secondary channel using the NARX neural network is higher than that of the ARX model. The simulation and experimental results show that the vibration damping effect of the proposed method is better than the traditional Fx-LMS method for both single-line spectrum and multi-line spectrum periodic low-frequency disturbances, which provides a new method for the suppression of periodic low-frequency disturbances. [ABSTRACT FROM AUTHOR]

This paper presents analytical and numerical studies on the active assignment of poles to a planetary gear system for vibration control in order to avoid resonance. This involves feeding back the displacement and velocity to add active stiffness and damping, respectively. A rotating frame of reference has been adopted in order to describe the dynamics over a broad range of rotational speed. As an illustration, the closed loop poles were assigned to the translational directions of the sun gear first and thereafter the carrier. This can be achieved by placing the actuators on the outer race of their bearings mounted onto their shafts. The controller was designed such that the closed loop poles can be assigned considering the rotational speed. In this way, it is possible to apply a robust pole-placement that is insensitive to the rotational speed. Numerical examples, where sensors and actuators were collocated, are presented to demonstrate the feasibility of the method when applied to a physical system. The results shows that the active control force and power required for the system, when rotating, can be determined using a rotating frame of reference and transformed for practical implementation. In addition, the same conjugate poles were assigned to the carrier and sun gear and the optimal place to apply control forces was discovered. This depends upon the control power required to shift the poles from one location to another. The results show that more control power will be required to shift the poles of the system when poles were assigned to the sun gear, where higher active bearing stiffness was required. Therefore, the optimal place to assign poles in this case is the carrier due to lower control power required to shift the system poles. [ABSTRACT FROM AUTHOR]

Recent hybrid control concepts, mixing active control with a fail-safe passive device, have drawn attractivity as they benefit from a theoretical hyperstability, ensuring very high stability margins. However, they have been experimentally tested until now only for the control of bending vibrations. The main purpose of this paper is to prove the performance of such systems also on torsional vibrations, with a specifically designed electromagnetic device, in order to contemplate the possibility to use them also for rotating machinery. As these control laws are model-free and require the adjustment of a few parameters related to the passive damper only, we demonstrate here their ease of integration for an application in rotating machines and we exhibit a direct experimental validation on an academic test bench. The latter which enables this experience despite the peculiarities of the rotation is therefore described, and the torsion reduction permitted by the hybrid control laws is assessed. A comparison between two of the newest hybrid control laws is also provided, proving the robustness and performance of these two hyperstable control laws. The main control parameters have been investigated and the performances are given through classical indicators but also in terms of energy consumption. [ABSTRACT FROM AUTHOR]

This work proposes an algorithm for feedback ANC that does not require a prior secondary path model and usually remains stable after fast secondary path changes, as other algorithms proposed for feedforward ANC. This is achieved using a recursive least squares algorithm to model the secondary path and the primary noise with an autoregressive moving average model. The resulting model allows for predicting future values of the primary noise. Finally, the primary noise values predicted are filtered by a non-causal inverse of the secondary path model to generate the anti-noise signal. Simulation results attest to the validity of the algorithm in reducing narrowband noise. [ABSTRACT FROM AUTHOR]

The objective of this investigation is to explore the issue of microgravity vibration isolation control within a space station, while considering constraints on output and unexpected disturbances. Drawing upon an analysis of the environment and operating conditions within the space station, the uncertainties resulting from variable payloads and unforeseen disturbances are depicted as combined disturbances. On this basis, an actor–critic neural network with energy consumption evaluation is used to estimate the combined disturbances and devise strategies for compensatory control. Furthermore, an adaptive robust term is devised to handle errors generated by the estimation process of the neural network. Additionally, to ensure that the output of the isolation system remains within specified bounds, an improved predefined performance function is introduced, thereby ensuring adherence to constraints regardless of initial conditions. Simulations conducted under different operational scenarios demonstrate the effectiveness of the proposed controller in achieving system stability. The results indicate a remarkable suppression of onboard vibration amplitude, amounting to approximately 60 dB within the frequency range of 2 to 100 Hz. • The analysis of the space station environment and working conditions is introduced. • An adaptive neural network with improved prescribed performance function is used. • The proposed approach is robust as it is insensitive to the unexpected disturbances. • Onboard vibration amplitude is suppressed by about 60 dB at 2 to 100 Hz. [ABSTRACT FROM AUTHOR]

In this paper, active vibration control of a composite beam bonded with piezoelectric layers on the top and bottom surfaces as actuators/sensors rested on a Winkler-Pasternak elastic foundation and subjected to an axial load on the beams' both ends and also under the lateral excitation load is studied using the first-order shear deformation theory (FSDT). When a constant electric charge is imposed, the governing equations of motion have been derived based on the FSDT in conjunction with the classical laminated beam theory applying the Hamilton's principle. The governing coupled partial differential equations are converted to the coupled ordinary differential equations using the harmonic series solution and then are solved by the fourth-order Runge–Kutta method. The effect of changes different parameters including geometric ratio of the beam's length to its height, the composite lay-up angle, number of vibrational modes, density of the composite beam, boundary conditions and feedback control gain on the natural frequency of vibration and transverse displacement of the beam are investigated. The obtained results show that the natural frequency of the beam decreases with increasing the length of the beam. Moreover, it is noticed that by increasing the feedback control gain the frequency of vibration reduces which leads to a better control of the beam's vibration. [ABSTRACT FROM AUTHOR]

This article proposes an efficient strategy for the active vibration control of smart beam that combines the Finite Element Method (FEM) and advanced robust control to suppress vibration. The piezoelectric actuator and sensor are coupled as part of the smart structure by using the 2D First-order Shear Deformation (FSDT) plate theory. The accurate modeling of the mechanical displacement field and electric potential field is achieved by approximating the sub-layered coupling of the piezoelectric potential field in the z-axis direction. In practice, most active controls of smart structures do not take into account the influence of the piezoelectric itself and the piezoelectric effect on the natural frequency of the smart structures, and they do not emphasize the internal stability and stability margin of the control system. Regarding the above questions, a modeling method of a generalized uncertain plant for the piezoelectric smart beam is proposed in this article. Fully considering the uncertainty of the system model caused by parameter perturbation and modeling error, a dynamic controller is designed with the μ-Synthesis technology. The proposed approach is numerically verified to have good robust performance on piezoelectric smart beam, which can effectively enhance the performance of smart structure control in other scenarios. [ABSTRACT FROM AUTHOR]

It is necessary to cut off all vibration transmission paths for an active vibration isolation system. A greater suppression of local responses will result in a better overall attenuation. In order to realize impediment at possible transmission paths, a new scenario of multi-axis transmission control is proposed, in which the active/passive isolator attenuates vibration transmission at multi-degrees of freedom by vertical and horizontal actuators mounted orthogonally on the intermediate inertial mass. This scenario is able to weaken the cross-coupling of control action between isolators by the passive parts. In order to investigate the characteristics of multi-axis transmission control, the dynamic model of a partitioned isolation system with one active/passive isolator is established and the involved transmission control is analyzed. The numerical results show that the foundation vibration can be attenuated along with the decrease of vibrations of the intermediate inertial mass. It is further revealed by experimental results that the multi-axis transmission control at the intermediate inertial mass is necessary to achieve sufficient vibration attenuation in the foundation, whereas the control in a single axis is ineffective. These verified results imply that the active/passive isolation with local transmission path control makes it possible to apply decentralized control in a large active vibration isolation system. [ABSTRACT FROM AUTHOR]

A gyroscopic rotor exposed to unbalance and internal damping is controlled with an active piezoelectrical bearing in this paper. The used rotor test-rig is modelled using an FEM approach. The present gyroscopic effects are then used to derive a control strategy which only requires a single piezo actuator, while regular active piezoelectric bearings require two. Using only one actuator generates an excitation which contains an equal amount of forward and backward whirl vibrations. Both parts are differently amplified by the rotor system due to gyroscopic effects which cause speed-dependent different eigenfrequencies for forward and backward whirl resonances. This facilitates eliminating resonances and stabilize the rotor system with only one actuator but requires two sensors. The control approach is validated with experiments on a rotor test-rig and compared to a control which uses both actuators. [ABSTRACT FROM AUTHOR]

In order to extract more wind energy, the wind turbine rotor becomes larger and the tower becomes taller. With more flexibility and smaller damping, wind turbine tower is prone to vibrate in winds. Meanwhile, the tower suffers the periodic loadings caused by the rotor rotation in the operational condition. The excessive vibrations could not only significantly affect the power generation but shorten the structural life due to the fatigue as well. It is challenging to reduce the vibration caused by the rotor rotation using the passive tuned mass damper (TMD) and traditional LQR controller due to the limited effective bandwidth. Therefore, an active tuned mass damper (ATMD) using a virtual TMD algorithm is proposed to mitigate the along-wind vibration of the tower under parked and operational conditions. The virtual TMD algorithm exhibits wide effective bandwidth and only requires the acceleration information on the top of the tower or the relative displacement of the active TMD. Firstly, the aerodynamic-structure-servo coupling (ASSC) model of the wind turbine is established which considers the interaction among the aerodynamic load, structure, and servo system. Secondly, the accuracy of the ASSC model is then verified using the onshore 5 MW wind turbine by the National Renewable Energy Laboratory (NREL). Thirdly, the ATMD feedback control force is designed by the virtual TMD algorithm. Finally, the reduction effect on the along-wind vibration by the proposed controller is evaluated at both of operational and parked conditions using the ASSC model. The TMD and LQR controller are utilized for comparison. The numerical results demonstrate that tuned mass damper (TMD) system with fixed parameters becomes detuned and may loses its effectiveness at different wind speeds. In contrast, active control can suppress the vibration of wind turbines at different wind speeds. Compared to the LQR controller, the proposed controller can enhance the reduction effect of wind turbine response with smaller stroke and control force at operational conditions. [ABSTRACT FROM AUTHOR]

The bearings are important paths for the shaft vibration transmitting to the hull structure. A new scenario based on non-contact electromagnetic actuators mounted at bearing pedestals is proposed to suppress the vibration transmission from the shaft to the elastic foundation. The dynamic model of a shafting system with the non-contact electromagnetic actuators is established on the Hamilton's principle. With this model, the influence of the displacement stiffnesses of the electromagnetic actuators on the vibration transmission is discussed, and the feasibility of active control is investigated. A multi-harmonic vibration suppression method is adopted and the performance is evaluated. Numerical results show that the vertical control by the electromagnetic actuators is able to attenuate the vibration transmission from the shaft to the foundation. With the addition of horizontal control, the foundation vibration is further decreased due to the reduction of power flow generated by the moments between the bearing pedestals and foundation. The results of a proof-of-principle experiment have also verified the effectiveness of the vertical control by the non-contact electromagnetic actuators in vibration transmission suppression and the foundation acceleration responses are remarkably reduced. [ABSTRACT FROM AUTHOR]

A model of piezoelectric phononic crystal (PC) double-layer nanobeam periodically attached by "spring-mass" resonators is proposed. As a comparison, two other simplified models are also proposed. In order to calculate the band structure, the plane wave expansion (PWE) method is improved by introducing the Euler beam and surface piezoelectricity theories. All the results and analysis demonstrate that the tunable advantage is displayed in double-layer nanobeam on account of the antisymmetric and symmetric vibrational modes controlled by adding additional springs between two different nanobeams. Moreover, the influencing rules of parameters related to additional spring and "spring-mas" resonator are also revealed. The bandgap properties can be applied to nano electro-mechanical system (NEMS) to realize active control of vibration. [ABSTRACT FROM AUTHOR]

In this article, the damped nonlinear transient response of a smart sandwich plate (SSP) comprising of agglomerated CNT-reinforced porous nanocomposite core with multifunctional magneto-piezo-elastic (MPE) facesheets, subjected to the thermal environment, is numerically investigated. The synergistic influence of agglomeration, porosity and pyro-coupling on vibration control is studied for the first time under the finite element framework. The attenuation of the vibrations is caused by active constrained layer damping (ACLD) treatment. The kinematics of the plate is based on the layer-wise shear deformation theory and von-Karman's nonlinearity. The viscoelastic properties of the ACLD patch and CNT agglomeration of the core are mathematically modelled using Golla–Hughes–McTavish and Eshelby–Mori–Tanaka methods, respectively. A comprehensive examination of the inter-related effects of different agglomeration states, porosity distributions and thermal loading profiles has been performed. The new insights on controlling pyro-coupled induced vibrations of smart sandwich plates by supplying control voltage directly to the MPE facesheets without ACLD treatment have been discussed thoroughly. The numerical analysis confirms the significant effects of pyro-coupling associated with active vibration control response of SSP. [ABSTRACT FROM AUTHOR]

Undesirable vibration of aircraft panel structures has a significant impact on the safety of their occupants and the operational reliability of various systems. The traditional time-domain controller based on the parallel multi-frequency filtered-x least mean square (FxLMS) control algorithm is simple and effective. However, the mutual influence of convergence steps and the induced harmonic components will limit its performance. An improved parallel multi-input multi-output multi-frequency FxLMS (MIMOMF-FxLMS) algorithm is proposed, considering the multi-input multi-output (MIMO) control requirement of the aircraft panel structure active vibration control (AVC) system and its inevitable channel coupling phenomenon. The feedback error signal and the control channel model are processed by frequency division in the MIMOMF-FxLMS algorithm, so that the FxLMS algorithm of each control channel runs independently, effectively avoiding mutual interference between convergence steps and the generation of induced harmonic components. Simulation and experimental research on multi-frequency AVC of the panel structure model is performed using a new type of piezoelectric stack actuator. The test results show that the proposed controller reduces the vibration level of each observation point by more than 98%, and the vibration responses of the first two-order frequency component are significantly suppressed, which also has strong adaptability and anti-noise ability. [ABSTRACT FROM AUTHOR]

During the actual wind power generation process, wind turbines are often affected by side effects such as blade vibrations, input constraints, and actuator faults. This can lead to a reduction in power generation efficiency and even result in unforeseen losses. This study discusses a robust adaptive fault-tolerant boundary control approach to address the issues of input-constrained and actuator-fault problems in wind turbine blade vibration control. By employing projection mapping techniques and hyperbolic tangent functions, a novel robust adaptive controller based on online dynamic updates is constructed to constrain vibrations, compensate for unknown disturbance upper bounds, and ensure the robustness of the coupled system. Additionally, considering the possibility of actuator faults during the control process, a fault-tolerant controller is proposed to effectively suppress elastic vibrations in the wind turbine blade system even in the presence of actuator faults. The effectiveness of the proposed controller is validated through numerical simulations. [ABSTRACT FROM AUTHOR]

Active vibration control of tensegrity structures is often challenging due to the geometrical nonlinearity, assemblage uncertainties of connections, and actuator saturation of controllers. To tackle these technical difficulties, a fast model predictive control (FMPC) strategy is herein implemented to effectively mitigate the structural vibration. Specifically, based on the explicit expression form of the Newmark- β method, the computation of the matrix exponential is avoided and replaced by one online and two offline transient analyses at each sampling instant on the structure, and the optimal control input is attainted from the second-order dynamic equation without forming an expanded state-space equation. Meanwhile, the artificial fish swarm algorithm (AFSA) is embedded to automatically derive optimal arrangement of actuators with the selection of a reasonable objective function. Two illustrative examples, including two standard and clustered tensegrity beams and a clustered tensegrity tower, have been fully investigated. The outcomes from illustrative examples prove the effectiveness and feasibility of the proposed method in optimal active vibration control of tensegrity structures, implying a promising prospect of the investigated approach in analyzing and solving relevant engineering problems. [ABSTRACT FROM AUTHOR]

The purpose of this study is to propose an innovative solution for evaluating the performance of a full-scale Active Mass Damper (AMD). The AMD adopted is a custom hydraulic actuator, developed for active control of existing buildings against earthquakes. For vibration control, a sky-hook algorithm was implemented. Its characteristics ensure good robustness, which is fundamental in structural engineering since buildings are subjected to significant variation in dynamic properties in presence of damage or ambient conditions. A Hardware-In-the-Loop (HIL) test bench was specifically designed to simulate the actual working condition of the anti-seismic system. The HIL setup consists of a shaking table moved by a hydraulic actuator in accordance with the roof's displacement, evaluated using a structural numerical model of the building to which the AMD is fixed. The presence of two distinct active systems (HIL and AMD) could generate control issues; therefore, a Triple Variable Control logic was introduced to reduce the interaction delay. The effectiveness of the proposed AMD is validated comparing the roof's displacement in an uncontrolled structure with that in a controlled one. Also, the robustness of the control algorithm was verified using a non-linear structural model and applying seismic excitation at different intensities. [ABSTRACT FROM AUTHOR]

Active vibration control (AVC) effect of the classical strategy is mainly restricted to a limited region around the error sensor, while the structural vibration at other locations may be dramatically enlarged. The enlargement is non-negligible when the global vibration suppression is considered. Aiming at this enlargement, an indicator is presented to reveal the effect of the classical strategy on the whole controlled structure. By establishing a cost function related with the indicator, an improved AVC strategy is proposed. Utilizing the proposed strategy, an optimized secondary force is obtained to achieve the global vibration suppression. Numerical simulations of AVC are undertaken on a typical plate to verify the superiority of the proposed strategy. Results demonstrate that the proposed strategy is still effective to achieve the global vibration suppression at frequencies where the classical strategy fails. This performance indicates that the proposed strategy is advantageous for global vibration suppression by attenuating the total input power, which provides more attraction for the actual application of AVC. [ABSTRACT FROM AUTHOR]

This paper proposes a new adaptive feedforward control method for the rejection of multiple periodic disturbances in the propulsion shafting system. The active vibration control scheme of the propulsion shafting system is established by employing the equivalent-input-disturbance principle which reduces the complexity of the control system in applications. The adaptive control algorithm is designed by taking the scale transformation procedure and the frequency-tracking technique into consideration. The scale transformation normalizes the iso-surface of the optimization function by the frequency response characteristics of the control channel, which immensely improves the convergence rate of the control algorithm for multi-harmonic disturbance. Moreover, the adaptive controller tracks the fluctuating frequencies in a direct method, enhancing the efficiency and robustness of the algorithm for eliminating time-varying disturbances. Finally, numerical simulation and experimental validation are carried out to show that the proposed method has good performance on the application of the active vibration control of the propulsion shafting system. [ABSTRACT FROM AUTHOR]

Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications. They are subject to various excitations from the conveying fluids, the supporting structures, and the working environment, and thus are prone to vibrations such as flow-induced vibrations and acoustic-induced vibrations. Vibrations can generate variable dynamic stress and large deformation on fluid-conveying pipes, leading to vibration-induced fatigue and damage on the pipes, or even leading to failure of the entire piping system and catastrophic accidents. Therefore, the vibration control of fluid-conveying pipes is essential to ensure the integrity and safety of pipeline systems, and has attracted considerable attention from both researchers and engineers. The present paper aims to provide an extensive review of the state-of-the-art research on the vibration control of fluid-conveying pipes. The vibration analysis of fluid-conveying pipes is briefly discussed to show some key issues involved in the vibration analysis. Then, the research progress on the vibration control of fluid-conveying pipes is reviewed from four aspects in terms of passive control, active vibration control, semi-active vibration control, and structural optimization design for vibration reduction. Furthermore, the main results of existing research on the vibration control of fluid-conveying pipes are summarized, and future promising research directions are recommended to address the current research gaps. This paper contributes to the understanding of vibration control of fluid-conveying pipes, and will help the research work on the vibration control of fluid-conveying pipes attract more attention. [ABSTRACT FROM AUTHOR]

Higher harmonic control algorithms in frequency domain are generally used for active vibration control of helicopter fuselage. However, these algorithms are inefficient to control transient vibration caused by rapid changing of helicopter flight conditions. Time domain feedback algorithms are efficient to control the transient vibration. In this paper, an excellent harmonic feedforward-sliding mode output feedback hybrid algorithm by combining frequency and time domain algorithms is presented to improve the effect and performance of active vibration control of helicopter fuselage, meanwhile to avoid the requirement of full state information of control system due to using the time domain algorithms. The convergence criterions of the harmonic feedforward algorithm and the hybrid algorithm are theoretically derived, respectively. The convergence speed of the hybrid algorithm is theoretically proved to be faster than that of the harmonic feedforward algorithm. Active vibration control simulation and experiment on a dynamically similar and geometrically scaled frame structure of a helicopter fuselage verify the proposed hybrid algorithm with excellent control effect and performance. [ABSTRACT FROM AUTHOR]

In recent years, with the development of sensor technologies, communication platforms, cyber-physical systems, storage technologies, internet applications and controller infrastructures, the way has been opened to produce competitive products with high quality and low cost. In turning, which is one of the important processes of machining, chatter vibrations are among the biggest problems affecting product quality, productivity and cost. There are many techniques proposed to reduce chatter vibrations for which the exact cause cannot be determined. In this study, an active vibration control based on the Sliding Mode Control (SMC) has been implemented in order to reduce and eliminate chatter vibration, which is undesirable for the turning process. In this context, three-axis acceleration data were collected from the cutting tool during the turning of Ti6Al4V. Finite Impulse Response (FIR) filtering, Fast Fourier Transform (FFT) analysis and integral process were carried out in order to use the raw acceleration data collected over the system in control. The system is modeled mathematically and an active control block diagram is created. It is observed that chattering decreased significantly after the application of active vibration control. The surface quality formed by the amplitude of the graph obtained after active control has been compared and verified with the data obtained from the actual manufacturing result. [ABSTRACT FROM AUTHOR]

Due to the complexity of the structure and the instability of the external air flow, considerable problems inevitably occur during the operation of aero-engines. Aiming at the vibration problem of the whole aero-engine, a general dynamic model of rotor-support-casing vibration transmission is established according to the actual structure of the aero-engine and the summary of experience. Moreover, starting from the vibration control problem of the internal and external cases of the aero-engine, a novel control algorithm (geometric design method） is used to design the vibration reduction controller in the limited frequency domain. In the case of limited sensors and actuator, the controller is used to try to control the vibration of multiple outputs （i. e., the inner and outer cases of the aero-engine), and compare the vibration reduction effect with the vibration reduction controller designed by proportional integral derivative (PID). Finally, the simulation model is built and verified by Matlab/Simulink. The results show that the geometric design method can intuitively obtain the existence, uniqueness and optimality of the optimal controller in the limited frequency domain, and the optimal vibration reduction control for the main control object can be as high as 25 dB. Compared with traditional control methods, the geometric design method has obvious advantages. [ABSTRACT FROM AUTHOR]

In the paper, a generalized mathematical formulation for active vibration control of rotating machines with voltage‐driven electrodynamic actuators between machine feet and steel frame foundation is derived. This generalized mathematical formulation is based on a state space description in the Laplace domain, where the state space vector is lead back, for considering the actuator forces. The aim of the paper is that this generalized mathematical formulation can be used now for arbitrarily models of rotating machines—1D‐, 2D‐, and 3D‐models—with voltage‐driven electrodynamic actuators between machine feet and steel frame foundation, and where the vertical vibration acceleration at each machine foot is lead back to a separate controller. Of course, this mathematical formulation can also be adopt easily to other boundary conditions. As an example, the generalized mathematical formulation is used here for a 1D‐model of a rotating machine, to calculate the poles and the frequency response functions. [ABSTRACT FROM AUTHOR]

An on-line estimation technique of multiple-frequency oscillatory forces combined with the Hilbert–Huang transform for an important class of actively controlled, forced vibrating mechanical systems with nonlinear stiffness forces is proposed. Polynomial parametric nonlinearities are incorporated in the significantly perturbed vibrating system dynamics. This class of nonlinear vibrating systems can exhibit harmful large-amplitude vibrations, which are inadmissible in many engineering applications. Disturbing oscillations can be also provoked due to interactions of the primary mechanical system to be actively protected against dangerous vibrations with other forced uncertain multidegree-of-freedom nonlinear vibrating systems. Taylor's series expansion to dynamically model uncertain vibrating forces into a small time window for real-time estimation purposes is employed. Intrinsic mode functions of multiple-frequency vibrating forces can be then obtained by the Hilbert-Huang transform. Uncertain instantaneous frequencies and amplitudes of disturbing oscillations can be directly computed in temporal space. An active vibration control scheme for efficient and robust tracking of prescribed motion reference profiles based on multiple frequency force estimation is introduced as well. The presented closed-loop on-line estimation technique can be extended for other classes of nonlinear oscillatory systems. Analytical, experimental and numerical results to prove the estimation effectiveness are presented. Numerical results show reasonable estimation errors of less than 2%. [ABSTRACT FROM AUTHOR]

Due to the excellent performance, giant magnetostrictive actuator is used in the active vibration isolation control system. However, its hysteresis nonlinear dynamic model is too complex for engineering practical applications, so it is necessary to establish an accurate and easy-to-use model. Based on Simulink/Simcape, a magnetic circuit model and a nonlinear dynamic physical model of the giant magnetostrictive actuator are developed. In the optimization of the magnetic circuit, the uniform distribution and the magnetic energy utilization of the giant magnetostrictive actuator are taken as the optimization objective, and the design criteria of the magnetic circuit are given. The hysteresis performance between the current and the magnetization is analyzed by simulating the magnetic circuit model. From the perspective of energy conservation, a linear magnetostrictive model which can reflect the effects of the frequency doubling and preload is established. Finally, the accuracy of the nonlinear dynamic physical model for the giant magnetostrictive actuator is verified by an experiment. The results show that the physical model agrees well with the experiment results not only under the quasistatic operating conditions but also under dynamic operating conditions. The error of the output displacement of the GMA under step response is less than 0.6 μm. [ABSTRACT FROM AUTHOR]

The paper investigates the active vibration control (AVC) of flexible thin-walled structure using dielectric elastomer (DE) actuator. It is proposed to bond directly DE film to the surface of flexible thin-walled structure so as to actively control structural vibration through in-plane actuation of DE film. This kind of actuator is referred to as planar DE actuator, which has advantages such as small additional mass and easy installation, and thereby can realize more easily active vibration control of flexible thin-walled structures in comparison with DE actuators with columnar configuration. In order to reduce control voltage, a multi-layer planar DE actuator (MPDEA) is further developed. Based on the Hamilton principle and the constitutive equation of DE material, the governing equation in the form of finite element for a cantilever polycarbonate beam with MPDEA is derived. Simulated and experimental studies are carried out on active vibration control of flexible thin-walled beam using MPDEA with different layers. The results show that MPDEA can achieve good vibration control effect for flexible thin-walled beam. Especially, the driving voltage can be greatly reduced by employing MPDEA. Moreover, a nonlinear compensation model is proposed to suppress the control spillover caused by nonlinear actuating properties of MPDEA. The simulated and experimental results of AVC of cantilever flexible thin-walled beam with the compensation model show that the overall control performance can be improved due to noticeable restrain of the control spillover. [ABSTRACT FROM AUTHOR]

To tackle the active control problem of the heavy platform-struts structure, this paper designs a kind of hydraulic servo actuator that can withstand large static load and generate high-precision, small-amplitude dynamic forces as well, and develops a multi-channel cross-coupling suppression control algorithm that can consider the strong coupling effect in structure. Subsequently, combining the designed actuators with the control algorithm, this paper puts forward an active heavy platform-struts structure vibration control method. By embedding the designed actuators into the support struts, a platform-struts structure experimental system is constructed to assess the vibration suppression effect of the proposed method. Excited by the amplitude-varying disturbing force, four different kinds of experiments are conducted. The experimental results show that the distributed multi-channel adaptive active control method without considering the coupling effect will lead to the instability, and the vibration attenuation of the proposed method in this paper exceeds 90%. The proposed method therefore has an important potential in addressing the problem of vibration suppression in the practical engineering. In addition, it has strong convergence and robustness. [ABSTRACT FROM AUTHOR]