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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]

Tuned mass damper inerter (TMDI) is a device that couples traditional tuned mass dampers (TMD) with an inertial device. The inertial device produces resistance proportional to the relative acceleration at its two ends through its "inertial" constant. Due to its unique mechanical properties, TMDI has received widespread attention and application in the past twenty years. As different configurations are required in different practical situations, TMDI is still active in the research on vibration control and energy harvesting in structures. This paper provides a comprehensive review of the research status of TMDI. This work first examines the generation and important vibration control characteristics of TMDI. Then, the energy harvesting performance of electromagnetic tuned mass damper inerter (EM-TMDI) is discussed. This work emphasizes the formation of a passive dynamic vibration absorber by coupling traditional TMD with inertial devices. This paper also summarizes the design and implementation of optimal vibration control and energy harvesting for TMDI. Furthermore, this paper details the applications of TMDI in the fields of bridges and building engineering. Finally, this paper summarizes the necessity of research on tuned mass-damper-inertia, the challenges faced currently, and future research directions, such as control of parameters in electromagnetic energy harvesting TMDI systems and low-cost TMDI. [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]

The paper concerns the technology of the design, realization, and testing of a flexible smart wing in a wind tunnel equipped with a turbulence generator. The system of smart wing, described in detail, consists mainly of: a physical model of the wing with an aileron; an electric servomotor of broadband with a connecting rod-crank mechanism for converting the rectilinear motion of the servoactuator into the aileron deflection; two transducers: an encoder for measuring the deflection of the control aileron and an accelerometer mounted on the wing to measure its bending and torsional vibrations; a procedure for determining the mathematical model of the wing by experimental identification; a turbulence generator in the wind tunnel; implemented ℋ ∞ and LQG algorithms for active control of vibrations. The attenuation experimentally obtained for the aeroelastic vibrations of the wing, but also for those accentuated by the turbulence, reaches values of up to 50%. [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]

For the vibration of automobile powertrain, this paper designs electro–hydraulic composite engine mounts. Subsequently, the dynamic characteristics of the hydraulic mount and the electromagnetic actuator were analyzed and experimentally studied separately. Due to the strong nonlinearity of the hybrid electromechanical engine mount, a Fractional-Order Least-Mean-Square (FGO-LMS) algorithm was proposed to model its secondary path identification. To validate the vibration reduction effect, a rapid control prototype test platform was established, and vibration active control experiments were conducted based on the Multiple–Input Multiple–Output Filter-x Least-Mean-Square (MIMO-FxLMS) algorithm. The results indicate that, under various operating conditions, the vibration transmitted to the chassis from the powertrain was significantly suppressed. [ABSTRACT FROM AUTHOR]

This paper proposes a reinforcement learning method using a deep residual shrinkage network based on multi-reward priority experience playback for high-frequency and high-dimensional continuous vibration control. Firstly, we keep the underlying equipment unchanged and construct a vibration system simulator using FIR filters to ensure the complete fidelity of the physical model. Then, by interacting with the simulator using our proposed algorithm, we identify the optimal control strategy, which is directly applied to real-world scenarios in the form of a neural network. A multi-reward mechanism is proposed to assist the lightweight network to find a near-optimal control strategy, and a priority experience playback mechanism is used to prioritize the data to accelerate the convergence speed of the neural network and improve the data utilization efficiency. At the same time, the deep residual shrinkage network is introduced to realize adaptive denoising and lightweightness of the neural network. The experimental results indicate that under narrowband white-noise excitation ranging from 0 to 100 Hz, the DDPG algorithm achieved a vibration reduction effect of 12.728 dB, while our algorithm achieved a vibration reduction effect of 20.240 dB. Meanwhile, the network parameters were reduced by more than 7.5 times. [ABSTRACT FROM AUTHOR]

A novel time-domain algorithm is proposed in this paper for the iterative estimation of drive files. A drive file is a synchronized batch of dynamic time series commands that are simultaneously sent to one or more actuators in a test rig that is designed for service environment replication (SER). When drive file commands are input to an SER test rig, the response of the article under test is similar to what was measured in a service environment. The proposed Pulse Train Filtered-X Least Mean Square (PT-Fx-LMS) algorithm is based on methods developed for active noise and vibration control (ANVC). A time-domain PT-Fx-LMS algorithm is shown through several simulation studies to rapidly converge to a dynamic solution in a small number of iterations for a one degree-of-freedom nonlinear suspension. The PT-Fx-LMS algorithm is also shown to enable targeted iteration over isolated time slices within the data set, which challenges conventional frequency-domain techniques. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to address the limitations of the filtered-x least mean square (FXLMS) control algorithm in terms of significant noise in filtered results and hindered convergence and steady-state error reduction due to fixed-step size iterations. Methods: In this study, a new adaptive filtering algorithm based on error weight is proposed. Multiple moment weight errors are introduced into the objective function, and the error weights are automatically calculated during the iterative process. The step size is optimized to accelerate convergence speed and curtail steady-state error. The state space equation and transfer function expression of the simply supported plate system are calculated, and a hybrid control algorithm for plate vibration control is designed. Results: The proposed algorithm is simulated and compared with various existing variable step size algorithms and gradient-based least-squares (GLS) algorithms using Mathematica software. The simulation results demonstrate that the proposed algorithm achieves a convergence rate at least six iteration steps ahead of other algorithms, with a minimum reduction of 0.00405 in the average absolute error. This indicates the superiority of the proposed algorithm in terms of convergence speed and steady-state error reduction. Conclusion: The proposed algorithm demonstrates clear advantages in enhancing the rate of convergence of the FXLMS control algorithm and reducing steady-state error. Future research can focus on reducing variable step input parameters and minimizing algorithmic computational complexity. [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]

Purpose: Due to the influence of uneven guide rail, rope swing and unbalanced shaft wind pressure, the high-speed elevator car may experience violent horizontal vibration, which seriously affects the comfort and safety of elevator passengers. Hence, it is vital to suppress horizontal vibration for high-speed elevator car (HSEC). Methods: This paper proposes a horizontal vibration active control method for high-speed elevators via acceleration feedback. First, based on passive vibration reduction, the active control is used to establish a four-degree of freedom (4-DOF) horizontal vibration model for elevator car. Then, we design an acceleration feedback-based controller for horizontal vibration response induced by guide rail excitation. The control objective functions in the multi-objective genetic algorithm are the system performance and control cost. The Pareto optimal solution set of the optimal controller parameters can be obtained only through one optimization calculation. Results: We use the comprehensive control simulation analysis through MATLAB/Simulink to validate the vibration suppression effect for the proposed active control strategy. For the system performance, by comparing the time domain responses of no controller and using controllers C1/C2/C3, the horizontal vibration acceleration is reduced to a certain extent. The offset of the high-speed elevator car high-speed elevator car frame relative to the center of the hoistway and relative displacements between the HSEC and the HSEC frame are also reduced in a certain proportion. The control cost is employed to evaluate the control force and represents the energy consumption to a certain extent. Combining system performance and control costs, we choose C2 among the 3 sets of controller parameters, the horizontal vibration acceleration of the HSEC can be reduced by about 80%, while the power consumption is between C2 and C3. Conclusions: The proposed optimal controller could effectively suppress elevator car horizontal vibration and significantly improve comfort while reducing the controller's power consumption. [ABSTRACT FROM AUTHOR]

With the increasing requirements for vibration isolation in multiple degrees of freedom (multi-DOFs), active control strategy is becoming more meaningful. However, the vibration isolation performance is limited by the time delay of feedback control, and cannot meet higher requirements. Therefore, this paper proposes a multi-DOFs active vibration hybrid control (AVHC) strategy based on a piezoelectric platform. The AVHC integrates the adaptive feedforward control based on the modified recursive least squares (MRLS) algorithm, and the feedback control based on the integral force feedback (IFF) algorithm. To achieve advanced response, the ground-based vibration signal is offset by the MRLS algorithm. To further reduce the coupling of multi-DOFs, the feedback and feedforward coordinates are fused through the matrix transformation, and the signals are linearly superimposed by the AVHC. The experimental results show that the AVHC can further reduce the resonance peaks of the three translational directions (X / Y / Z) compared with the feedback (FB) control. The resonance peaks are reduced from 14.6 dB (FB) to 3.11 dB (AVHC), from 14.56 dB (FB) to 5.14 dB (AVHC), and from 12.44 dB (FB) to 3.78 dB (AVHC) in X / Y / Z directions, respectively. The attenuation rates are improved by 73.36%, 66.19%, and 63.10% in X / Y / Z directions, respectively. [ABSTRACT FROM AUTHOR]

In wind tunnel tests, the cantilever sting supporting system often suffers from low-frequency and large-amplitude resonance due to its inherent low structural damping characteristic, resulting in the degradation of data quality and structural safety. To improve wind tunnel testing safety and data accuracy, this paper is dedicated to establish an active vibration control system using piezoelectric stack actuators. A novel methodology of vibration monitoring based on modal transformation, which uses measured strain and a Strain-to-Displacement Transformation (SDT) matrix to reconstruct dynamic displacement field, is proposed herein. Meanwhile, strain sensor positions are optimized by an improved Particle Swarm Optimization (PSO) algorithm to reduce systematic estimation errors of this method. Furthermore, a Back-Propagated Neutral Network (BPNN) is established to implement a self-adaptive control strategy. A series of verification tests are performed to demonstrate the validity of the proposed system. Experimental results indicate that the relative Root Mean Square Error (RMSE) between estimated vibration displacement and measured vibration displacement is less than 3%, and a vibration attenuation of over 14 dB/Hz is achieved in ground tests, proving the superiority of this intelligent active vibration suppression system. [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]

The control of systems like: bipedal locomotion robots, space launch vehicle, offshore wind turbines, and active vibration control systems in buildings and bridges, have to ensure, besides stability and accuracy, the system's insensitivity to parameters' uncertainties, unmodeled dynamics, external disturbances, and measurements noise. In such systems analysis and controller design, a triple inverted pendulum can be used as a benchmark to mimic systems characteristics and effect of different sources of uncertainty. μ-synthesis is a robust control method which seeks a controller that minimizes the robust H-infinity performance of the closed-loop system through D-K iteration. The D-K iteration is not guaranteed to converge to a global, or even local minimum. Hence this paper proposes the enhancement of controller design by applying gazelle optimization technique to shape the fictitious output by determining the parameters of the performance weighting matrix. The incorporation of optimization with controller design allows avoiding getting unnecessarily conservative system at the expense of performance. The developed control system is simulated using Matlab R2023b for different scenarios of system uncertainty. The results show that the requirements of robustness and performance can be balanced through the right choice of cost function. The robust performance measure obtained is 0.6432 which leads to good response for both stabilization and tracking in the presence of uncertainty. The results also show that even the baseline μ-synthesis design achieves higher robust stability margin about 2.818, the proposed optimized method stabilizes the system with overshoot been reduced by 67.65% and steady state error reduced by 5.69% without sacrificing robustness. [ABSTRACT FROM AUTHOR]

Purpose: In the paper, a theoretical analysis—based on a 2D multibody model—is presented regarding active vibration control of a rotating machine with voltage-driven electrodynamic actuators between machine feet and steel frame foundation under multiple base excitations. Methods: Mathematical formulations are derived in the time domain and then transferred into the Laplace domain, where a state space formulation is used to describe the controlled vibration system. With this mathematical formulations, it is possible to analyze separately the two different kinds of actuator forces—the actuator forces, caused by the motion-induced voltage and the actuator forces caused by the control system—and their influence on the vibration behavior. Afterward, the mathematical formulations are transferred into the Fourier domain, for considering harmonic excitations of the base. Also a numerical example is presented, where different cases regarding machine mounting and operation conditions are investigated and compared to each other. Results: It could be clearly demonstrated that with the presented control system, most of the resonance peaks in the frequency responses could be strongly damped. Conclusions: With the presented mathematical formulations, the controlled vibration system can be well described, considering separately the two different kinds of electrodynamic actuator forces and their influence. [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]

• A pipe dynamic model is created considering fluid-structure coupling and piezoelectric effects. • A new method is proposed to solve state equations with rigid equation characteristics. • An experimental system for active vibration control of fluid-filled pipes with MFC is built. • The feasibility of MFC for pipe vibration reduction is verified by experiments and simulations. • The influences of fluid velocity and pressure on the active control effect are revealed. For the fluid-conveying pipeline with macro-fiber composites (MFC), relevant dynamic modeling and experimental testing studies are rarely found in previous papers. Therefore, this paper has carried out related research work. Firstly, considering the fluid-structure interaction and piezoelectric effects, a semi-analytical modeling method for the fluid-conveying pipeline with MFC attaching to any position is proposed. A new Runge-Kutta-Gear (RKG) time-domain solution method is presented for solving state-space equations with the characteristics of rigid equations, and the design methods of Linear-Quadratic Regulator (LQR) controller and Proportional-Integral-Derivative (PID) controller are introduced, respectively. Secondly, an experimental system for active control and vibration test is built, and the dynamic model and control method are verified by experiments and simulations. Finally, the influence of relevant control parameters in the controller on the active control effect is discussed, and the influence law of fluid parameters such as fluid velocity and fluid pressure on the active control is also clarified. The novelty of this work is that the active vibration control and solution methods for the fluid-conveying pipeline with MFC are proposed, and the feasibility of MFC for pipeline vibration suppression is verified by experiments, which provides a new technical idea for the vibration reduction design of the fluid-conveying pipeline. [Display omitted] [ABSTRACT FROM AUTHOR]

Nature's morphology and optimal energetic solutions remain the key motivation for designing cellular-based lattice structures. Understanding the nonlinear dynamical behaviors that arise from different lattice topologies of such structures in the metastructure framework is crucial for their successful implementation in various novel designs and technologies related to vibration and shape control. This paper presents a study of the static and dynamic response of auxetic and honeycomb lattices with hourglass or dome-shaped metastructures. The potential tailoring of nonlinearity of such responses through various design parameters that play a vital role in shaping the dynamic properties of such structures is discussed here. The impact of cell design parameters on the resulting macroscopic behavior is assessed using both numerical simulations and experimental studies. The transition from softening to hardening nonlinear dynamic responses is reported with cell topologies ranging from the regular honeycomb to auxetic topologies that are widely used as fundamental cells of cellular materials design. The experimental study is based on the time responses measured to verify the numerical predictions. The experimental system consists of different 3D printed hourglass samples based on the auxetic and honeycomb lattices on which dynamic testing using a laser Doppler vibrometer is performed. The design strategies proposed in this paper can be integrated into a wide range of lattice-based materials for noise and vibration control applications and biomedical devices. • Transitioning from softening to hardening nonlinear dynamic responses through lattice. • Achieved controlled nonlinearities by utilizing the instabilities of the dome structure. • Numerical simulations and experimental investigations using laser Doppler vibrometer. • Study will potentially help the selection of lattice for functionally graded materials. [ABSTRACT FROM AUTHOR]

Current offshore wind turbine installation and positioning methods require mechanical equipment attached on the lifted components and human intervention. The present paper studies the development of a contactless motion compensation technique by investigating a magnetically controlled pendulum. The technique involves the interaction of a magnetic pendulum with an electromagnetic actuator. Two control modes are considered: the imposition of a desired motion to the mass and the motion attenuation of a prescribed pivot excitation. The numerical model is validated and calibrated against experiments and demonstrates excellent predictive capabilities. The control exerted is effective for a broad range of excitation frequencies and amplitudes. Important parameters associated with the performance of the technique such as the separation distance of the magnets and the saturation of the controller are identified. The controllability regions for effective control depending on the characteristics of the excitation are derived. The force amplitude of the contactless actuator is comparable to currently-used active tugger line control systems, but with the additional advantage of both attractive and repulsive forces. The findings of this paper illuminate the path for the further development of a non-contact control technique which has the potential to increase the efficiency of offshore wind installations. • Contactless position control for offshore wind turbines: a proof of concept. • Pendulum motion control via magnetic interaction. • Additional control authority with both repulsive and attracting forces. • Efficient control for the desired motion of a pendulum mass for a fixed or moving pivot. • Estimated force amplitude comparable to active tugger control systems. [ABSTRACT FROM AUTHOR]

In an active vibration control (AVC) system, the secondary path can generally only be identified when the system has been built. The performance of a typical adaptive feedforward control system using the filtered-x least mean square (FxLMS) algorithm is heavily dependent upon the dynamic characteristics of the secondary path. It would, therefore, be helpful for engineers to have knowledge of this behavior early in the design process. In this paper, pre-identification of the secondary path is proposed, which means its offline identification model can be obtained without installing the AVC equipment. This can save both time and money. In the pre-identification process, the secondary path is split into three parts. The first part includes the actuator and related electrical equipment. The frequency response function of this part can be identified after the hardware has been selected. The second part involves the dynamic behavior of the structure to be controlled, which is identified by impact excitation using a specially developed pneumatic impact harmer. The third part concerns the analogue/digital and digital/analogue converters whose effect on the secondary path is offset by a phase shift corresponding to half the sampling time. In this paper, the pre-identification process of the secondary path components is described, and some experiments are conducted to verify the feasibility of the approach and to demonstrate the significance of the pre-identification results. This mainly involves predicting the control performance and optimizing the parameters of the control system. Combined with the simulation of the control system, the approach proposed can improve the work efficiency of large-scale engineering projects and reduce the cost of testing. [ABSTRACT FROM AUTHOR]

This work focuses on the development of custom capacitive sensors for measuring vibration and small displacements of high-speed rotating machines. The main criteria for this development are to use cheap and available resources and to optimize these resources to achieve the best possible performance. The aim was to design a solution that could be implemented within an Active Vibration Control (AVC) system, where the focus is mainly on high measurement frequency. The paper also includes a theoretical description of the measurement methodology with capacitive sensors and the use of the FDC2214 capacitive-digital converter (CDC), which works on the principle of a resonant LC circuit. The last part of the paper is devoted to the comparison of different designs of sensitive parts and also the concepts themselves. In addition to the calibration, the static characteristics are also described, and a measurement range error analysis is performed. The result of this work is a solution with a maximum measurement frequency of 3.8 MHz, maximum relative error of about 0.7% and sensor resolution from about 700 nm to 14 µm. The work also includes the deployment of the resulting smart sensors on the high-speed rotating machine to prove the capability to use them in the already mentioned AVC system. [Display omitted] • Explanation of the principles of capacitive sensing. • Development of an efficient and low-cost solution for measuring small displacements in the range of 0–1000 micrometers. • Comparison of several developed sensor designs. • The maximum relative error of the sensor is approximately 0.7% over the measuring range. • Maximum measurement frequency reached up to 3.8 MHz. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy to improve the performance of a low-frequency vibration calibration system. The low-frequency vibration calibration system based on a linear motor is first developed. The amplitude sensitivity and phase sensitivity are then derived. Subsequently, the composite control strategy of the iterative learning control (ILC) and Luenberger observer is established to improve the performance of the linear motor vibration generator. Finally, the frequency stability of the linear motor is measured, and a tri-axial accelerometer is calibrated. Experimental results indicate that the linear motor controlled by the proposed composite strategy can fulfill accelerometer calibration with high precision, and maintain the performance in the full frequency band. [ABSTRACT FROM AUTHOR]

In the offshore pipeline plugging operation, the coupling vibration between the in-pipe fluid, the pipeline isolation plugging robot (PIPR) and the pipeline will aggravate the deterioration damage of the pipeline and PIPR. Therefore, this paper proposes an active vibration reduction control method for the PIPR to reduce vortex-induced vibration during dynamic plugging. A PIPR active vibration reduction structure with a spoiler end face is designed, and a numerical simulation-based response surface method is utilized to optimize the relevant parameters of the spoiler end face. The vibration evolution law of the in-pipe fluid is revealed when the spoiler end face continuously changes during dynamic plugging. Pressure prediction model of dynamic plugging process is established based on back propagation (BP) neural network. The active vibration reduction control strategy is proposed to actively adjust the spoiler end face based on predicted pressure during dynamic plugging process, which can restrain the wake vortex and reduce the plugging-induced vibration. Finally, an experimental setup is designed to verify the effectiveness of the active vibration reduction control method. The results indicate that this method can effectively ensure the safety and stability of plugging operation. • Active vibration reduction structure is designed for PIPR with a spoiler end face. • Active vibration reduction control strategy is proposed for spoiler end face. • Dynamic evolution law of the flow field is revealed under turbulent models. • Pressure prediction models for different spoiler end faces are established. [ABSTRACT FROM AUTHOR]

High-precision payloads such as ultra-stable optical clocks for next-generation space missions are greatly sensitive to the low-frequency micro-vibrations induced by various flexible appendages equipped on the spacecraft. The frequencies of such micro-vibrations are uncertain and near the measurement limit of acceleration sensors, leading to insufficient vibration control performance of classical feedback control. To solve this problem, a hybrid control algorithm which combines PI controller and the filter-x least-mean-square (FxLMS) algorithm is proposed in the paper. In particular, a frequency estimation algorithm is designed for the active vibration control system to provide the reference signal. In the new system, the rough estimation of disturbance frequency is given by the adaptive notch filter. Then, the frequency is refined by Kalman filter and provided into the autoregressive model, which fine-tunes the estimated frequency and offers the reference signal for the hybrid PI-FxLMS algorithm. Finally, the experimental prototype of active vibration control system is developed and the proposed control algorithm is adopted. The experimental results demonstrate the effectiveness of the frequency estimation algorithm and further validate that the proposed hybrid PI-FxLMS algorithm can effectively suppress the low-frequency micro-vibrations near the measurement limit of acceleration sensors and with uncertain frequency. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to active chatter control in milling operations using a new concept called the virtual inerter-based dynamic vibration absorber (VIDVA). While passive control methods, such as tuned mass damper (TMDs), have their merits, they may not provide optimal performance and adaptability in certain scenarios. Moreover, the realisation of an idealised inerter-based absorber as a localisation addition can be a difficult task to achieve. In response of these challenges, the integration of the inerter concept into virtual passive absorber (VPA) control to improve chatter stability performance is proposed. Four IDVAs are numerically evaluated to enhance the absolute chatter stability limit, and the numerical results are experimentally validated using cutting tests with a proof-mass actuator providing the control force. The study also includes robustness and actuator saturation analysis to provide a comprehensive evaluation of the proposed virtual IDVA. The findings demonstrate that the virtual IDVA offers improved chatter suppression performance, making it a promising solution for active chatter control and application of IDVAs in milling operations. • A virtual passive inerter-based absorber is proposed for chatter suppression. • A robustness analysis is presented, applicable also passive control methods. • Actuator saturation is evaluated for chatter suppression. • Inerter-based absorbers are more preferable than TMDs in virtual active controls. [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]

In this paper, the combination of a nonlinear system and a robust sliding-mode controller with sliding integral surface is studied. This controller is composed of a linear part and a nonlinear part defined by a non-smooth function. Calculating the frequency response curve of such a system can be time-consuming and difficult using time integration methods. An original algorithm based on the harmonic balance method and capable of directly calculating the periodic solutions of a robust sliding-mode controller with sliding integral surface is proposed. In addition, the classical numerical methods for continuation of nonlinear frequency response curves and stability calculation of periodic solutions have been adapted to take into account the integral component of the control law. Finally, experimental validations on a non-linear structure have been carried out, attesting to the efficiency of the proposed controller and the robustness of the proposed numerical tools. • Nonlinear system coupled with sliding mode control law. • Original algorithm for periodic solutions based on the harmonic balance method. • Continuation and stability of nonlinear frequency response curves. • Comprehensive bifurcation tracking to assess the influence of the nonlinear controller. • Experimental validation on a non-linear structure. [ABSTRACT FROM AUTHOR]

In this paper, considering the influence of uncertainties in piezoelectric intelligent structures with active vibration control law, a robust topology optimization method to reduce the sensitivity of structural dynamic flexibility to uncertainty factors for piezoelectric intelligent structures is proposed. The effect of active control can be equivalent to the damping. Considering the influence of uncertainty, the structural dynamic response of the system will be within the interval range. Due to the monotonicity of the steady-state displacement response on uncertain parameters and the monotonicity of dynamic flexibility on uncertain parameters are both difficult to determine, a more accurate upper and lower limit is obtained using the collocation method. With the constraints of reliability and volume, the robustness index is defined based on the dynamic flexibility of the structure and defined as the objective function to establish the robust topology optimization model. In terms of optimization solution, the reliability index is transformed into the constraint translation distance. The sensitivity of constraint functions and objective functions to design variables is derived by employing the chain derivative method and the adjoint vector method. Finally, two examples are used to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The cable-strut structures have the features of low stiffness and weak damping, resulting in large vibration response under dynamic excitation. The vibration response of the cable-strut structures can be reduced by active control methods. However, many traditional active control methods need to build a state-space model (SSM) based on finite element model (FEM), and solving the active control force for the high-dimensional SSM is time-consuming. In this paper, the dynamic mode decomposition with control (DMDc) method is proposed to achieve a data-driven reduced-order SSM for active vibration control of cable-strut structures. This proposed method only uses the data of structural response and control force input to build reduced-order SSM and does not rely on the FEM. Linear quadratic regulator (LQR) design using the DMDc-based reduced-order SSM (DMDc-LQR) is more computationally efficient than that using the FEM-based SSM (FEM-LQR). The relationship between the design parameters of the DMDc-LQR controller and the FEM-LQR controller is established, which ensures that the control performance indexes of the DMDc-LQR controller and the FEM-LQR controller are equal. The effectiveness of the proposed DMDc-LQR method is validated using numerical Kiewitt cable dome and tensegrity grid under wind and seismic loads. The results show that the DMDc-LQR controller maintains similar control effect to that of the FEM-LQR controller and has advantage of high computing efficiency as well. In addition, the influence of critical parameters (i.e., data noise and model order) on vibration control effect is comprehensively explored. It is found that increasing the model order is effective to mitigate the noise influence on the DMDc-based reduced-order SSM and ensures the effectiveness of the DMDc-LQR controller. • A data-driven reduced-order state-space model (SSM) method is proposed. • The linear quadratic regulator (LQR) is designed based on reduced-order SSM. • The control effect and design efficiency of two LQR controllers are discussed. • The influence of noise and model order on the vibration control effect is explored. [ABSTRACT FROM AUTHOR]

• Two computationally efficient, model-free adaptation schemes for active vibration control are proposed. • Frequency and gain of the resonant controller are adaptively tuned. • Fraction-order adaptive control outperforms integer-order control. • Analytical and simulation results are supported by experiments. • The proposed controller is robust compared to the existing control schemes in the literature. The efficacy of different class of resonant controllers has been successfully established for active vibration control. This class of controllers utilize a second-order filter fed back with the structural response (displacement, velocity or acceleration) and the control signal is synthesized as the linear/nonlinear function of the filter response. However, the performance of the controller largely depends on the tuning of the filter frequency to the structural natural frequency. Thus, for structural systems where the natural frequency and the excitation frequency are uncertain, one requires to tune the filter frequency adaptively. The present paper introduces two computationally efficient, fractional-order nonlinear adaptive resonant controllers with acceleration feedback for vibration control. The control signal is synthesized as the linear/nonlinear function of the filter variable and its fractional order derivative. Two parameters, namely the filter frequency and the control gain, are adaptively varied to control the phase and amplitude of the control signal, respectively. The objective of frequency adaptation is to maintain the phase of the control signal in the quadrature of the system displacement/acceleration. Theoretical analysis of the system is performed by the method of multiple scales under the assumption of slowly varying parameters. The results are verified by both numerical simulations and experiments. The theoretical and experimental results demonstrate the robustness of the proposed adaptive control against uncertainties in excitation force and system parameters. It is comprehensively shown that the fractional-order control is superior to the integer-order control already studied in previous works. Moreover, the effect of feedback time-delay is also studied, and it is shown that the fraction-order control can offset the detrimental effects of time-delay on the frequency response of the system. [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]

Purpose: Active magnetic bearing (AMB) is designed and optimized for contactless support and active vibration control in a flexible twin-spool rotor system subjected to mass unbalance and harmonic base excitation. A multiobjective genetic algorithm is utilized to optimize the AMBs supporting the inner rotor. The primary aim of this analysis is to control the vibration amplitude within a tolerable range at those positions along the rotor where AMBs and disks are located. Besides, a comparative study is also performed to investigate the effect of increasing the mass unbalance on AMB design parameters. Methods: The system response is evaluated through a finite element method (FEM) based vibration analysis, for which the mathematical model is developed using the Lagrangian approach with due consideration to the rotary inertia and shear effects. For rotordynamic analysis and implementation of multiobjective genetic algorithm, MATLAB codes have been developed. Results and Conclusion: With optimized design parameters, a maximum reduction of 73.66% in the amplitude peak is obtained at the AMBs locations. Besides, it has been found that forward and backward whirling modes get excited due to mass unbalance and base excitation. Also, it is found that on increasing the mass unbalance, the optimum number of turns, pole width and length are found to increase by 32.87%, 23.16% and 15.42%, respectively. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the event-triggered vibration control problem for active full-vehicle suspension systems based on preview road information. The motivation is to design a novel event-triggered mechanism combined with preview information for improving vehicle stability while considering network-induced delays and limited communication bandwidth of networked control systems (NCSs). Methods: Firstly, as the payload of the vehicle is time varying, Takagi–Sugeno (T–S) algorithm is employed to characterize the vehicle suspension model. Secondly, a novel event-triggered function is designed to dynamically adjust the data transmission rate through preview information in the resource-limited communication network. Finally, since data transmission delays occur in the network system, an augmented Lyapunov–Krasovskii functional is employed to guarantee the suspension system stability with the H∞ standard. Results: The stability of the proposed event-triggered control system is proven. In addition, numerical and experimental details are presented to substantiate the feasibility of the event-triggered controller. Conclusion: The proposed event-triggered controller is more effectively to utilize the limited communication resource and improve the vehicle stability than the traditional control method. [ABSTRACT FROM AUTHOR]

Purpose: To establish a smart thin plate in which structural health monitoring (SHM) and active vibration control purposes are integrated, the locations of attached piezoelectric ceramic (PZT) actuators as well as their applied normalized voltage are investigated. Method: Normal strains of such coupled electro-mechanical systems are defined using Kirchoff's classical laminate plate theory (CLPT), and then, by Ritz solution, these normal strains are converted to spatially dependent functions that are employed to define virtual work for the actuators as a function of location and applied voltage. Finally, genetic algorithm (GA)-based iterative optimization is carried out to locate the actuators as well as determine the normalized applied voltage for each of them in the desired modes. Results: Three plates with different boundary conditions are studied for optimal placement of PZT actuator/s. The PZT actuator/s are optimally placed where the maximum amount of exerted virtual work is reached to fulfil the perfect excitation needed by SHM and provide the highest damping energy for undesired vibration at designated modes. The results show that the optimum location of PZT actuator/s lies where the maximum sum of normal strains is. Conclusion: The proposed process is valid for any mixed boundary conditions on a thin plate with any number of square actuators with a minimum computational effort, where both location of the actuator/s and applied voltage can be manipulated via GA to achieve the maximum exerted work done by PZT actuator/s at each desired natural mode. [ABSTRACT FROM AUTHOR]

Purpose: Thin-walled structures are widely used in modern engineering, and their vibration problems are usually complicated and changeable. In this work, an inertial piezoelectric actuator with simple structure and easy reconfiguration is developed to solve such problems. Method: Active vibration control method is adopted to suppress the vibration of thin-walled structures. Fuzzy adaptive PID algorithm is introduced to improve the output ability and active control efficiency of the actuator. Results: The thin plate with size 580 × 580 × 1 mm was taken as the controlled object. Experimental results show that with step input, the maximum amplitude decreases by more than 50% and the steady-state time decreases by more than 30%. Under sinusoidal excitation, the steady-state amplitude decreases by more than 90% and the steady-state time is less than 1 s. Conclusion: Both the free vibration and forced vibration of the thin plate are attenuated obviously. The feasibility of using the fuzzy adaptive PID algorithm to realize the active vibration control of thin-walled structure with inertial piezoelectric actuator is verified. [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 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]

The vibrations of the helicopter fuselage are mainly induced by the rotor with blade pass frequency and the high order harmonics. The conventional filtered-x least mean square (FxLMS) control algorithm usually used a uniform convergence factor for all the harmonics which leads poor effect in controlling multi-harmonic vibration. In this paper, a novel parallel multi-harmonic global multi-channel (MHGMC) control method is proposed to suppress the multi-harmonic vibration components transmitted from the main rotor to the fuselage. Bandpass filters are used to separate multiple frequency components of the error signals, the control channel models are identified for the corresponding frequency range to independently control each frequency component, and the reconstruction of the reference input signals can be obtained from the separated error signal, effectively improving the performance of tracking interference signals. In addition, the coupling of the control channels is considered, and the global vibration optimization is taken as the control objective to update the weight coefficient of the controller. An active vibration control system of the helicopter main gearbox eight-strut installation configuration has been established. The simulation and experiment results show that the proposed controller has faster control convergence speed and better control effect of multiple harmonics than the conventional filtered-x least mean square algorithm, and the attenuations of the disturbing frequency harmonic components at all measurement points in the experiment are over 38dB. The experimental results of variable excitation also verify that the proposed control algorithm has excellent adaptability and strong robustness. [ABSTRACT FROM AUTHOR]

In this paper, an analysis model of adaptive active vibration control system of composite laminated plate using macro fiber composite (MFC) piezoelectric patches is presented, and the experimental testing is carried out. Electromechanical coupling equations of the composite laminated plate are established by considering the influence of the mass and stiffness of MFC piezoelectric patches. The adaptive active vibration control scheme for composite laminated plate based on the filtered-x least mean square (FxLMS) algorithm is proposed. The accuracy of the present analysis model is validated by the results of experimental test and finite element method (FEM). It can be found that the vibration responses nearby the first and second natural frequencies of the composite laminated plate can be rapidly and greatly suppressed by the adaptive active control system and experimental test. Moreover, the dynamic responses of the composite plate under multi-frequency excitation and random excitation can be fast controlled by the presented adaptive active control system. The novelty of this work is that a theoritical analysis model of adaptive closed-loop control system based on the MFC piezoelectric patches is presented for vibration suppression of composite laminated plate, and the effectiveness of the proposed adaptive active model are validated by experimental testing. [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]

Purpose: The present work proposes active vibration control in a composite material beam using electromagnetic actuators. The advantage of using electromagnetic actuators is applying control force without mechanical contact. Method: In order to evaluate the performance of the fuzzy control technique, a controller using fuzzy logic was designed. The mathematical model of the beam was obtained through the eigensystem realization algorithm/observer/Kalman identification, which consists of an identification method used to identify modal parameters in complex structures. With the obtained mathematical model, the controllers were designed, responsible for determining the control effort. Electromagnetic actuators are responsible for applying control efforts to stabilize the system. Results: The numerical simulations responses and the experimental system control responses were obtained from this. The system vibration attenuation was obtained in both procedures with three types of controllers, such that all responses were evaluated, both in the time and frequency domains. Conclusion: Finally, the robustness of the controller was analyzed from the variation inserted in the dynamic matrix of the system, thus validating the studied methodology. [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]