Active Vibration Control Research Articles

Development of a High-Performance Low-Weight Hydraulic Damper for Active Vibration Control of the Main Rotor on Helicopters—Part 1: Design and Mathematical Model

The helicopter vibrations generated by the main rotor/gearbox assembly are the principal cause of damage to cockpit instruments and discomfort of the crew in terms of cabin noise. The principal path of vibration transmission to the fuselage is through the gearbox rigid support struts. With the aim of reducing these vibrations, this paper presents the design of a low-weight high-performance active damper for vibration control developed by Elettronica Aster S.p.A. The system is intended to replace the conventional struts and is composed of an electro-hydraulic actuator hosted within a compliant structure. This parallel nested structure allows the system to reach a high-power density. A physics-based mathematical model was used as a design digital twin to optimize the performance to meet the strict requirements. The active damper was designed for a reference application of a 15-seat medium-sized twin-engine helicopter. The model was used to perform the tests specified in the acceptance and testing procedure document, showing the compliance with the requirements of the current design. The damper physical realization, test bench design, experimental campaign, and model validation will be presented in Part 2.

실시간 상태-공간 식별 기반 제어기를 이용한 유한 국부공진 메타물질 평판의 적응형 진동 저감

To improve the internal sound quality of an electric vehicle, the noises (tire and road noises), vibration, and discomfort should be reduced effectively. Compared to the conventional damping materials, the locally resonant metamaterial is advantageous in terms of reducing the vibration in the low frequency band and reducing the weight through a stop band, where vibration is not transmitted. However, the locally resonant metamaterial installed in a finite structure fails to form an ideal stop band. Additionally, there is a problem of occurrence vibration mode at an arbitrary frequency. Accordingly, there is a need for an active vibration control method capable of learning and actively reducing the vibration modes occurring at arbitrary frequencies within the stop band in real-time. In this study, a real-time state-space identification-based active vibration control method was proposed to reduce the vibration modes occurring at arbitrary frequencies within the stationary band of local resonance metamaterials. The active vibration control method proposed in this study, combined with the existing passive vibration reduction method, can be utilized to effectively reduce the vibration for random disturbance of a fluctuating system.

Accuracy Characterization of a MEMS Accelerometer for Vibration Monitoring in a Rotating Framework

Active and passive vibration control systems are of paramount importance in many engineering applications. If an external load excites a structure’s resonance and the damping is too low, detrimental events, such as crack initiation, growth and, in the worst case, fatigue failure, can be entailed. Damping systems can be commonly found in applications such as industrial machines, vehicles, buildings, turbomachinery blades, and so forth. Active control systems usually achieve higher damping effectiveness than passive ones, but they need a sensor to detect the working conditions that require damping system activation. Recently, the development of such systems in rotating structures has received considerable interest among designers. As a result, the development of vibration monitoring equipment in rotating structures is also a topic of particular interest. In this respect, a reliable, inexpensive and wireless monitoring system is of utmost importance. Typically, optical systems are used to measure vibrations, but they are expensive and require rather complex processing algorithms. In this paper, a wireless system based on a commercial MEMS accelerometer is developed for rotating blade vibration monitoring. The proposed system measurement accuracy was assessed by means of comparison with a reference wired measurement setup based on a mini integrated circuit piezoelectric (ICP) accelerometer adapted for data acquisition in a rotating frame. Both the accelerometers were mounted on the tip of the blade and, in order to test the structure under different conditions, the first four blade resonances were excited by means of piezoelectric actuators, embedded in a novel experimental setup. The frequency and amplitude of acceleration, simultaneously measured by the reference and MEMS sensors, were compared with each other in order to investigate the viability and accuracy of the proposed wireless monitoring system. The rotor angular speed was varied from 0 to 300 rpm, and the data acquisitions were repeated six times for each considered condition. The outcomes reveal that the wireless measurement system may be successfully used for vibration monitoring in rotating blades.

Vibration characteristics and cross-feedback control of magnetically suspended blower based on complex-factor model

The research of vibration characteristics and active control methods of the magnetically suspended blower (MSB) are conducted for mitigation of the vibration amplitudes and the dynamic displacements of rotor shaft of the MSB at high speed. Firstly, the dynamic models with four degrees of freedom (DOFs) of the rotor shaft in the MSB are established. Secondly, the vibration characteristics of rotor shaft considering the rotor unbalance and misalignment are analyzed using the complex-factor model. Furthermore, the complex-factor and complex-exponential function cross-feedback models are respectively used to suppress the vibration amplitudes and the dynamic displacements of rotor shaft. Both numerical simulation and experimental tests of the cross-feedback model are conducted to verify the models. It is shown that a wide cutoff frequency of low-pass filter (LPF) could mitigate the precession, and a wide cutoff frequency of high-pass filter (HPF) could suppress the nutation. The proposed complex-exponential function cross-feedback model could be used to reduce the precession amplitude of the rotor shaft by 38.88%, and mitigate its nutation by 60.42%.

Dynamic analysis of a tunable electromagnetic bistable system

Bistable structures exhibit a unique snap-through behaviour, which is widely used in different engineering disciplines. Some bistable systems have the ability to change dynamic characteristics such as the depth of the potential wells, distribution of the stable equilibrium points, and symmetry of the potential function, but only for the initial assembly. Therefore, this study presents a novel tunable electromagnetic bistable system (EBS), which can be adjusted online. An EBS is composed of a mechanical spring and an electromagnetic negative-stiffness unit in parallel. To characterise such a system, a static model was developed using the filament method, and the dynamic response was calculated using the harmonic balance method to better understand the EBS tunability. We conducted a series of studies aimed at revealing the effects of the geometric parameters, initial conditions, and excitation level on the dynamic characteristics. Finally, a switch between the interwell and intrawell oscillations of the actively tunable EBS was experimentally demonstrated, improving applications such as adaptive energy harvesting and active vibration control.

Particle swarm optimization of a non-collocated MIMO PPF active vibration control of a composite sandwich plate

The Particle Swarm Optimization (PSO) algorithm is employed to tune the Multiple-Input Multiple-Output (MIMO) Positive Position Feedback (PPF) controller to reduce vibrations on a composite sandwich plate with free boundary conditions, equipped with piezoelectric actuators and sensors. The PSO algorithm determines the value of forty-four parameters describing the transfer functions of the MIMO PPF controllers. The solution found by the PSO code depends on the cost-function employed. In this work, two cost functions are investigated. The first function minimizes the time necessary for free vibrations to decay to zero, while the second function minimizes the area under the resonance peaks of the frequency response of the controlled plate. For both cost-function cases, the parameters found by the PSO algorithm are determined through simulations based on a reduced-order model of the structure. Once the parameters are determined, they are loaded on a real-time prototyping board and employed to dampen the vibrations of the sandwich plate tested in laboratory experiments. The compatibility of simulations and experiments was verified at various points on the surface of the plate, and vibration reductions up to 90% of the uncontrolled amplitude were achieved experimentally for the first eight modes. The absence of spillover on following modes was verified in simulations and experiments.

Energy-Based Optimal Placement of Piezoelectric Actuator on Smart Thin Plate

PurposeTo 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.MethodNormal 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.ResultsThree 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.ConclusionThe 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.

Design of Decoupled and Dynamically Isotropic Parallel Manipulators Considering Five Degrees-of-Freedom

AbstractA six degrees-of-freedom (DOF) two-radii Gough–Stewart Platform (GSP) can be designed to be dynamically isotropic and has been proposed for micro-vibration isolation. In many applications, the torsional mode can be ignored, and a 5DOF dynamically isotropic, parallel manipulator capable of attenuating three translational (3T) and two rotational (2R) modes are sufficient. In this work, we present the designs of a novel 5DOF dynamically isotropic parallel manipulator for vibration isolation where the torsion mode can be ignored. We present closed-form solutions in their explicit form, and these are obtained using a geometry-based approach. The first design is based on a modification to the two-radii GSP and provides enhanced design flexibility and feasibility. The second design, with the first five decoupled modes, is based on superposing geometrical parameters of two three-legged dynamically isotropic or decoupled parallel manipulators. It is shown that this design has two translational modes, namely the X, Y modes, which are decoupled from two rotational modes Rot(X), Rot(Y) and are controlled by two different sets of three legs. This feature can lead to simpler control and less power requirements if active vibration control is chosen. The designs presented in this work include the effect of asymmetry and the payload center of mass variation. The dynamically isotropic and decoupled designs were successfully validated using the finite element software ansys®. Experimental results based on a two-radii GSP prototype further validate analytical and simulation results.

Active vibration control and experimental investigations of the composite parabolic shell with variable cross-section under thermal load

The accurate dynamic equation of the parabolic shell with variable cross-section is developed in this paper. The geometric nonlinearity is used to amend the expression of the strain. Considering the large overall motion and solar heat flux, the flexible deformations and freedom vibrations of the parabolic shell are analyzed by the proposed method. Meanwhile, the strain rate feedback control law with piezoelectric layer is presented to improve the dynamic performance of the parabolic shell during the motion process. The experiments with parabolic shell are studied to verify the correctness of the proposed method and control strategy. It is found that the results obtained by the proposed method agree very well with the experiments. Furthermore, the numerical results show that high-frequency vibration and flexible deformation can be effectively improved by the Macro Fiber Composite (MFC). And the optimized controller gain coefficient is also discussed at the end of this paper. This paper demonstrates the importance of the piezoelectric layer for the improvement of the dynamic response of flexible parts.

Simulation and Experiment of Active Vibration Control Based on Flexible Piezoelectric MFC Composed of PZT and PI Layer.

In order to improve the vibration suppression effect of the flexible beam system, active control based on soft piezoelectric macro-fiber composites (MFCs) consisting of polyimide (PI) sheet and lead zirconate titanate (PZT) is used to reduce the vibration. The vibration control system is composed of a flexible beam, a sensing piezoelectric MFC plate, and an actuated piezoelectric MFC plate. The dynamic coupling model of the flexible beam system is established according to the theory of structural mechanics and the piezoelectric stress equation. A linear quadratic optimal controller (LQR) is designed based on the optimal control theory. An optimization method, designed based on a differential evolution algorithm, is utilized for the selection of weighted matrix Q. Additionally, according to theoretical research, an experimental platform is built, and vibration active control experiments are carried out on piezoelectric flexible beams under conditions of instantaneous disturbance and continuous disturbance. The results show that the vibration of flexible beams is effectively suppressed under different disturbances. The amplitudes of the piezoelectric flexible beams are reduced by 94.4% and 65.4% under the conditions of instantaneous and continuous disturbances with LQR control.

Structural Design and Analysis of New Electromagnetic Actuator

active vibration control can effectively restrain low-frequency line spectrum vibration. As an output end of control force, an electromagnetic actuator has the problem of low precision of output force and zero drift. Therefore, a new type of electromagnetic actuator is designed in this paper. The parametric modeling of the magnetic circuit structure is carried out, and it is verified that the magnetostatic attraction in direct current (DC) magnetic circuit is zero. Then, a calculation method of electromagnetic force in alternating current/direct current (AC/DC) magnetic circuit is deduced. The mechanical-electrical-magnetic-thermal multi-physical coupling field simulation of the electromagnetic actuator is carried out, which shows that the improved magnetic circuit structure effectively solves the zero drift, improves the precision of output force of the actuator, and allows the actuator to have lower electromagnetic heat output and electromagnetic loss.

Active vibration control of flexible beam system based on cuckoo search algorithm

<p>A flexible beam is recognized as a lightweight structure that is prone to excessive vibration, resulting in poor performance. Thus, controlling unwanted vibration is necessary to maintain the system’s performance. Therefore, this study presents a technique to suppress undesired vibration in a flexible beam structure by introducing active vibration control (AVC). However, to develop an effective controller, an appropriate flexible beam model must first be obtained. In recent times, one of the best methods employed to model a flexible beam structure is system identification via a swarm intelligence algorithm. In this study, an intelligent algorithm acknowledged as cuckoo search (CS) was acquainted. The capability of the proposed algorithm was verified using three robustness techniques which were correlation test, pole-zero diagrams and mean square error (MSE). The simulation result showed that the CS algorithm achieved superior performance by achieving the lowest MSE of 6.1547x10<sup>-9</sup>, a correlation test between a 95% confidence level and high stability. Next, a proportional-integral-derivative (PID) controller tuned by the Ziegler-Nichols method was developed using the transfer function accomplished from the CS model. Two types of interference, namely single and multiple sine waves were introduced to validate the effectiveness of the controller. The controller successfully achieved a 30.2 dB of attenuation level for both disturbances.</p>

Analysis and Experimental Research on Vibration Characteristics of Pressure Shell Structure

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.HighlightsThe 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.

Novel vibration control method of acoustic black hole plates using active–passive piezoelectric networks

In recent decades, many methods have been applied to vibration system damping and control, including acoustic black hole (ABH) structures and active–passive hybrid piezoelectric network(APPN) structures. This paper takes a two-dimensional ABH plate based on Kirchhoff plate theory as the research object, systematically researching the structure of the integration of APPN and ABH. Firstly, the vibration modes of the ABH plate are obtained by the finite element method. Then, Hamilton’s principle and the Rayleigh–Ritz method are used to derive the dynamic models. The open-loop and closed-loop control characteristics are analyzed, respectively. The results show that the ABH plates with active–passive piezoelectric networks perform better than those with active vibration control. Finally, the parameters (resistance and inductance) in APPN are optimized to obtain the best vibration control performance. The results show that the new system combined APPN and ABH firmly controls vibration and noise reduction.

Radio Frequency Cavity’s Analytical Model and Control Design

Reduction or suppression of microphonic interference in radio frequency (RF) cavities, such as those used in Electron Linear Accelerators, is necessary to precisely control accelerating fields. In this paper, we investigate modeling the cavity as a cylindrical shell and present its free vibration analysis along with an appropriate control scheme to suppress vibrations. To this end, we first obtain an analytical mechanical dynamic model of a nine-cell cavity using a modified Fourier-Ritz method that provides a unified solution for cylindrical shell systems with general boundary conditions. The model is then verified using the ANSYS software in terms of a comparison of eigenfrequencies which prove to be identical to the proposed model. We also present an active observer-based vibration control scheme to suppress the dominant mechanical modes of the cavity. The control system performance is investigated using simulations.

VIBROACOUSTIC SOUNDPROOFING FOR HELICOPTER INTERIOR

As VIP passengers generally want to fly civil and executive jets where vibratory and acoustic environment is smoother than on the normal jets. Helicopter interior noise is generated by main and tail rotors, engines, main gearbox, and aerodynamic turbulence (Lu et al., 2018). Because of these sources, the tonal and broadband noise is incredibly high and needs to be reduced. Conventional passive system (soundproofing) is the best way to control the acoustic of the cabin whereas active systems (active vibration and noise control) are not completely reliable or applicable. The design of the soundproofing may be researched by simulation using one of these programs: ANSYS, SOLIDWORKS 2020 and ACOUSTIC analysis Vibroacoustic Monitoring (VAM) approach. The analyses were performed from frequency ranges, 5-10Hz and 0-2000Hz then transformed into frequency velocity domain using Proudman’s equations (Lu et al., 2017). Soundproofed ANSYS models are validated using instantaneous sound pressure levels measured within the helicopter during flight. The acoustic detection method for GAZELLE is also performed successfully in SOLIDWORKS for aluminum alloy and titanium alloy, this proves the relationship between acoustic power levels and material configuration. The noise coefficient responses of interior materials are used as main index for soundproofing helicopter interiors. The results of this research can be used for implementation of VAM approach for soundproofing helicopter interiors.

An Improved Feedforward-Robust Algorithm for Active Vibration Control of Helicopter Maneuver Flight

To solve the problem of secondary path mutation and external disturbance abrupt changes during helicopter maneuver flight, the previous research proposed a hybrid active vibration control law. To improve the engineering applicability, the original algorithm is ameliorated to the least mean square-input-output-based robust (LMS-IOBR) algorithm. The system model within the target frequency band can be identified through the input-output data to avoid constructing complex state observers. In addition, the output form of the feedback controller is constructed by an autoregressive moving average model with extra input, which is beneficial to improve operational efficiency. Numerical simulations demonstrate that compared with the original algorithm, controller real-time computation can be reduced by 52% with control effects guaranteed at the same time. Furthermore, to verify the effectiveness and adaptability of LMS-IOBR, multi-input multioutput vibration control experiments are carried out on a specially developed simple platform for simulating helicopter maneuver states. Comparative tests in various typical states are performed between the LMS-IOBR and the multichannel least mean square algorithm. Under the complex circumstances of simulating continuous subduction uplift, the peak response of closed-loop system attenuates by 80% and 70%, and the vibration of two points is reduced to 15% and 20%, respectively, within 3 s. The experimental results demonstrate that the proposed LMS-IOBR algorithm shows stronger transient adaptability and robustness against external disturbance excitation and secondary channel mutation in helicopter maneuver flight.

Fuzzy logic based active vibration control using novel photostrictive composites

Although conventional actuators like piezoelectric and electrostrictive are efficient, but they required hard wiring, which contaminates the control signal and adds to the weight of the structure. The current study presents a wireless control strategy using photostrictive actuators. Owing to the fortunate combination of photovoltaic effect and converse piezoelectric effect, a photostrictive actuator can generate mechanical strain, when irradiated with light intensity. Limited choices of photostrictive material with high electromechanical coupling coefficient give the motivation to design photostrictive composites. The finite element-based formulation incorporating fuzzy logic controller is employed to study the active vibration control response of cantilever structure when equipped with photostrictive composite actuator. A parametric study has been carried out to study the influence of inclusion’s volume fraction on wireless active vibration control of the structure. Control merits have been defined to compare the control performance of different composites. It is found that particulate composites are the better choice for lightweight structure and fiber composites are better if there is no weight constraint.

Design and Implementation of an Active Vibration Control Algorithm Using Servo Actuator Control Installed in Series with a Spring-Damper

The membrane-type air spring can be used to suppress lateral vibration of a vibration isolation table. However, compared to voice coil actuators, pneumatic actuators are difficult to use for precise vibration control, because servo valves have nonlinear dynamic characteristics. Therefore, actuators, such as voice coil actuators, can be placed in parallel with air springs, allowing force-type actuators to provide additional force to the system. These actuators generate force. In the case of a ball-screw mechanism device or a linear servomotor, it is an actuator that generates displacement. These actuators are represented as serial active systems. Serial active systems are structurally simpler than parallel active systems. However, there are very few studies on vibration isolation systems using serial active systems compared to parallel active systems. As the two are different types of systems, a new control algorithm suitable for the serial active system is needed. This study proposes a system in which an actuator capable of accurately controlling displacement is connected in series with a support spring-damper. A new active vibration control algorithm for the proposed control system is also developed, which is termed the position input and position output. The proposed control algorithm uses the displacement of the system as an input and outputs the desired displacement of the actuator installed in series with the damper and spring. The proposed control algorithm increases the damping at the target frequency and reduces the response of the system. Numerical studies and experiments were conducted on the single-degree-of-freedom and multi-degree-of-freedom systems. The results show the efficacy of the proposed control system and the novel control algorithm for the vibration suppression of the lateral vibration of a vibration isolation table.

Sizing optimization and experimental characterization of a variable stiffness shape memory polymer filled honeycomb composite

Variable stiffness structures and materials have been considered for many applications, including active vibration control and shape morphing. With regards to shape morphing, variable stiffness materials and composites have been considered for reconfigurable skin materials in aerospace vehicles. Of the many concepts that have been developed for such applications, shape memory polymers (SMPs) are one such promising materials for shape morphing. SMPs exhibit both high modulus ratios and recoverable strains but suffer from a low overall modulus and often require reinforcements, such as honeycomb. This work investigates the design space of such honeycomb reinforced SMPs as variable stiffness materials. Unit cell finite element models are developed for the material, and parametric studies are completed for varying honeycomb cell geometries. A multiobjective, constrained Pareto front optimization is completed for two honeycomb material models and in two loading directions using selected sizing design variables. Pareto fronts are established, and cell geometries are selected and fabricated to experimentally verify the optimized model predictions. The results both predict and demonstrate the advantages of using honeycomb reinforcements for SMPs. Effective in-plane moduli as high as 45 GPa are predicted while achieving a change in modulus of 450X. Compared to existing reinforcement strategies for shape memory polymers, these composites exhibit favorable combinations of both high stiffness and high changes in stiffness with a high degree of tailorability through the honeycomb cell geometry and predicted performances that meet and exceed the state of the art.