Input Vibration Research Articles

Optimal control of structural vibration using LQG algorithm

This paper proposes a Linear Quadratic Guassian Design (LQG) with based semi-active control algorithm for vibration reduction of building structures. The controlled damper force required by the structure has been calculated from an MR damper of load capacity 100N. A building frame has been selected to illustrate the performance of the proposed algorithm. Four different earthquake acceleration data has been used as input vibration data to the numerical frame. The proposed method of damping on the frame has been found to be more effective to reduce the structural response significantly in comparison with the conventional tuned liquid column damper. The developed method is efficient in providing the optimum control force required to the frame. Therefore, it minimizes the need of high damping capacity and the number of dampers. As a result, it reduces the cost of maintenance and structural control during earthquakes.

Optimal design of cubic nonlinear energy harvester device for random vibrations

Linear energy harvesters have a narrow frequency bandwidth and hence operate efficiently only when the excitation frequency is very close to the fundamental frequency of the harvester. Consequently, small variations of the excitation frequency around the harvester’s fundamental frequency drop the energy output making the harvesting process inefficient. To extend the harvester’s bandwidth, some recent solutions call for using electromechanical devices with stiffness-type nonlinearities. This work deals with the optimisation of the performance of a single degree-of-freedom electromagnetic energy harvester whose mechanical behaviour has a Duffing-type nonlinearity, as for suspended masses, to reduce the size of energy harvesting devices without affecting their power output. The vibration input is assumed as a broadband Gaussian white noise base acceleration. It is analytically shown that the optimum load resistance of the device is different to that which is dictated by the principle of impedance matching.

SMA-based adaptive tuned mass dampers: Analysis and comparison

Different types of adaptive tuned mass dampers have been recently proposed in the literature. One of the most promising approaches to make tuned mass dampers adaptive is the use of shape memory alloys. In this class of tuned mass dampers, different layouts have been proposed. This paper aims at comparing the two main layouts (wire-based and beam-based) in terms of adaptation capability, exerted force and electrical power consumption. To this purpose, the models of the two layouts are developed. These models minimise the number of required inputs, which basically are only related to device geometry, shape memory alloy characteristics, and vibration input. After an experimental validation, the models are employed for the mentioned comparisons between the two considered layouts.

Electrical network optimization for electrically interconnected suspension system

The electrically interconnected suspension (EIS) can control vehicles' multiple-degree of freedom dynamics by designing a proper electrical network that connects independent electromagnetic suspensions. However, developing an electrical network (EN) for passive EIS to deal with complicated vibration is challenging. This paper proposes an EN optimization methodology for the EIS and experimentally validates the effectiveness of the optimized ENs with a hardware-in-the-loop (HIL) platform. First, a half-car model with a passive EIS is built and analysed for the EN design. The candidate EN structures are identified with an innovative method, which can cover all possible layouts with pre-determined complexity. Then, the optimization procedure of the EIS EN structures is determined to achieve a satisfactory level of ride comfort and handling stability. Finally, the optimized parameters of ENs are obtained with the genetic algorithm. In the HIL tests, the optimised ENs are validated with typical road vibration inputs and steering inputs. Experimental results demonstrate that a vehicle with optimized ENs can achieve better ride comfort and handling stability than vehicles with traditional passive suspension and unoptimized EIS electrical networks.

Vibration Energy Conversion Power Supply Based on the Piezoelectric Thin Film Planar Array.

Vibration energy harvesting has received much attention as a new type of power solution for low-power micro/nano-devices. However, VEH (vibration energy harvester) based on PVDF (polyvinylidene fluoride) piezoelectric materials have a low output power and energy conversation efficiency due to the relatively low piezoelectric constant, coupling coefficient, and dielectric constant. For this reason, we design a vibration energy conversion power supply, which consists of a VEH with a PVDF piezoelectric thin film planar array vibration structure and an energy harvesting circuit for regulating the electric energy of multiple sources. Furthermore, our solution was validated by simulations of structural dynamics in COMSOL and equivalent circuits model in Multisim. From the circuitry simulation results, the output current and the charging period increase and decrease, doubling, respectively, for each doubling of the number of array groups of films. Moreover, the solid mechanics simulation results show that the planar array structure makes the phase and amplitude of the input vibration waves as consistent as possible so that the same theoretical enhancement effect of the circuitry model is achieved. An identical experimental test was implemented with vibration conditions of 75 Hz-2.198 g. The fabricated harvester quickly charged the 22 V-0.022 F ultracapacitor bank to 5 V in 24 min. The maximum open circuit voltage and output power, respectively, were 10.4 V and 0.304 mW. This maximum charging power was 11.69 times higher than that of a single film. This special power supply can replace batteries to power low-power electronics deployed in vibrating environments, thus reducing the maintenance costs of equipment and environmental pollution rates.

Prediction of Traffic Vibration Environment of Ancient Wooden Structures Based on the Response Transfer Ratio Function.

Traffic-induced vibration is increasingly affecting people's lives, which necessitates scrutiny of the environmental vibrations caused by traffic. This paper proposed a vibration prediction method suitable for the ancient wooden structures subjected to traffic-induced vibrations based on the multi-point response transfer ratio function. The accuracy of the proposed approach was also checked by comparing the predicted results with the measured results in the context of both the time domain and frequency domain. Subsequently, the environmental vibrations due to heavy-duty trucks passing at various speeds were measured, and the measurements were utilized as the input vibration excitation to assess the structural vibration of the Feiyun Pavilion. The structural safety was evaluated according to the "Technical specifications for protecting historic buildings against man-made vibration". In order to meet the structural safety requirements of the Feiyun Pavilion, it is strongly recommended to limit the type and speed of vehicles in the nearby area.

Quantitative Power Flow Characterization of Energy Harvesting Shock Absorbers by Considering Motion Bifurcation

Vibration energy harvesting technology can capture ambient energy forms. Using an energy harvesting shock absorber (EHSA) is one of the methods to achieve this function. The EHSA with mechanical motion rectifier (MMR) has motion bifurcation, which can improve energy harvesting performance and reduce the impact between gears. However, the motion bifurcation makes it difficult to quantitatively predict the vibrational energy dissipation and energy harvesting of the MMR−EHSA. Evaluating the performance of an MMR−EHSA during the design phase becomes highly complex. In this paper, a novel nonlinear dynamics model of MMR−EHSAs is established to solve motion bifurcation and quantitative power flow. Furthermore, the proposed MMR−EHSA prototype is fabricated, and dynamics testing is initiated to verify the theoretical model under harmonic vibration. The testing results show that the theoretical model can predict the working characterization of MMR−EHSAs. The resistance of optimal harvesting energy and maximum damping power is revealed by the quantitative power flow model under harmonic vibration. In addition, the working performance under random vibration is discussed. The proposed nonlinear dynamics model has advantages when solving random vibration input and has potential for practical application.

Evaluation of human perception thresholds of transient vibrations for the assessment of building vibration

Vibrations in low-rise buildings in the frequency range from a few hertz to tens of hertz are caused by external sources, such as road traffic, and could induce annoyance in occupants if their magnitude is in excess of human perception levels. Although there have been several different standardised metrics to evaluate human responses to such vibrations, no common metric has been accepted worldwide. In the present study, laboratory experiments were conducted to determine human perception thresholds of transient vibrations similar to building vibrations. The thresholds were evaluated by three methods based on running r.m.s. acceleration with different integration methods and frequency weightings and by the fourth power vibration dose method. The metrics based on the Vibration Level used in Japan and the Vibration Dose Value in the international standard were better than the other methods for the evaluation of perception of the input vibrations used in the experiments. The evaluation of threshold of transient vibrations was also investigated with short-time average acceleration by optimising the integration time and time constant for averaging. The optimised integration time and time constant appeared to be dependent on the frequency and waveform of transient vibration.

Conducting polymer-based generators for vibro-electrochemomechanical energy conversion and harvesting

Energy harvesting technologies have received much attention to alleviate providing energy crisis by batteries for different applications including sensors and actuators. Compared to other sources, mechanical energy is more available and most widely distributed. Conducting polymers as piezoionic materials have gained a large number of attention in light of their advantages of having promising electrical and mechanical properties for electrochemical energy conversion and storage. In this paper, conducting polymer-based PEDOT/IPN/PEDOT trilayer structure is proposed for electrochemomechanical energy harvesting applications. For the proposed trilayer power generator, the vibro-electrochemomechanical model is demonstrated. In this modeling approach, the mechanical behavior of the trilayer is modeled in finite element software to capture the induced strain due to vibration input. Resistive-capacitive transmission line model is implemented to model the electrochemical response of the trilayer to mechanical input which is induced strain and predict the generated voltage. Finally, the simulation results show the ability of the energy harvester to convert the 2 g and 20 mm input acceleration and displacement to electrical energy and generate 986 µW power. This model enables one to find the best parameters and also calculate the potential generating power to have an optimal design.

CONTROL OF A SINGLE LINK FLEXIBLE MANIPULATOR USING SEQUENCED CONTROL

Mekanik sistemler çalışmaları esnasında titreşimlere ve bozucu etkilere maruz kalırlar. Bu etkilerden kurtulmak için çeşitli kontrol yöntemleri geliştirilmiştir. Sıralı kontrol, PID kontrol ve giriş şekillendirmeyi bir araya getiren bir kontrol yöntemidir. Temelinde giriş şekillendirme kullanarak sistemin hızlı ve titreşimsiz bir şekilde istenen referans değerine ulaşması sağlandıktan sonra, anahtarlama yardımıyla PID kontrole geçilerek sistemin bozucu etkilere karşı dayanıklı olmasını sağlamak yatar. Sıralı kontrol, PID kontrol ve giriş şekillendirmeyi optimum zamanlarda kullandığı için, her iki kontrol yönteminin avantajlarından faydalanırken, dezavantajlarından kurtulmayı amaçlar. Sıralı kontrolün, doğru uygulandığında, her iki kontrol yönteminin birlikte kullanıldığı hibrit kontrol yöntemlerinden avantajlı olduğu görülmüştür. Bu çalışmada tek eklemli esnek robotun transfer fonksiyonu MATLAB-Simulink ortamında modellenmiştir. Modellenen sisteme sırasıyla basamak giriş, giriş şekillendirme, PID kontrol ve sıralı kontrol uygulanarak sistem yanıtları elde edilmiş, çıkışlar performans açısından karşılaştırılarak sistem performansının iyileştirilmesi için öneriler sunulmuştur.

A vibration energy harvesting system for Self-Powered applications in heavy railways

Heavy-duty trains with intelligent autonomous rail transit systems play an essential role in transporting goods and storing a large amount of energy to make it more sustainable. This paper presents a vibration energy harvesting system using a two-ball pair mechanism to collect track vibration for power sensors of a heavy railway network. The track vibration input module, motion conversion module, generator module, and energy storage module are essential subdivisions of the proposed system. The reciprocating linear vibrations of the track are transferred to the motion conversion module via the track vibration input module. The motion conversion module converts the vertical vibration into unidirectional rotation by employing a two-ball pair mechanism. The generator module utilizes the unidirectional rotary motion to generate electricity and is stored in an energy storage module. The performance of the energy harvesting system is evaluated based on simulation and experimental analyses under similar boundary conditions and found a good agreement between the results. The results indicate a maximum performance of 48.3% with an output power of 0.928 W, and this power is sufficient for self-propelled applications around heavy railways.

A piezo stack energy harvester with frequency up-conversion for rail track vibration

To enable predictive and preventive maintenance in rail transportation systems, energy harvesting is a promising powering method. Piezoelectric energy harvesters have great powering potential, but so far the power harvested by piezoelectric railway generators is low. To explore the capability, this work presents a piezo stack energy harvester with frequency up-conversion method consisting of both the inertial mass system and the piezo stack transducer system from rail track vibration energy harvesting. The frequency up-conversion method uses the impact between the inertial mass system and the piezo stack transducer system to enable the piezoelectric transducer to operate at the transient resonant frequency response in spite that the input vibration frequency is much lower than the transducer one to achieve high-power generation. A theoretical model considering the impact between the two systems is established to describe the motion of the energy harvester. Numerical simulation and finite element analysis are conducted to model the proposed energy harvester and compared with experimental results to validate the proposed method. The time-dependent reactions, the frequency response characteristics, and the influence factors on output such as impedance, initial interval, acceleration, signal waveform are studied to evaluate the energy harvesting performance. In the experiments, the proposed energy harvester outputs a maximum power of 495.74 mW and an average power of 43.58 mW at an input rms acceleration of 0.7 g applied at 18 Hz with an optimum load impedance of 150 Ω, exhibiting good performance in comparison with the state-of-the-art piezoelectric energy harvesters applied on the rail track.

1g model test of piled-raft foundation subjected to vibration load and its simulation considering small confining stress

The numerical simulations of 1 g model tests are presented to evaluate the feasibility of the proposed elasto-plastic constitutive model, which can precisely describe the less compressibility of clean sand under small confining stress. The dynamic responses of piled-raft foundations subjected to cyclic train loads were investigated by comparing the results of model tests and simulations. Different frequencies of dynamic loading and different grounds including dry loose sand, dry/saturated medium dense sand, were taken into consideration. It is confirmed that for all types of grounds and input vibration, the numerical results showed a good match with model tests data, especially the settlement and acceleration of piled-raft foundation. Both numerical simulations and experiments showed that the higher the frequency of the dynamic load is, the greater the peak acceleration will be. The proposed constitutive model has greatly improved the accuracy of the numerical simulations on the small-scale 1 g model tests because this model can accurately describe the mechanical characteristics of sand from very small confining stress to normal confining stress, especially the less compressibility and more dilative behavior of sand under small confining stress. • The proposed constitutive model can precisely describe the less compressibility of sand under small confining stress (CS). • The model tests were well reproduced by the numerical analysis with proposed constitutive model in the different grounds. • The proposed model has greatly improved the accuracy of the numerical simulation on the small-scale 1 g model test. • Excess pore water pressure was small both in the tests and simulations, because of more dilative behavior of sand at small CS.

Case study: Effect of asymmetry of vibration on the perceived illusion force

The illusion force perceived by exciting asymmetric vibration has been studied, and the kinesthetic effect is recently clarified to be largely influenced by the asymmetry of the excited vibration waveforms. However, it has not yet been investigated how the extent of asymmetry influenced the perception of the illusion force. In this study, the effect of the asymmetry of the input vibration waveform on the extent of induced traction force was experimentally investigated by changing the extent of asymmetry that is controlled by the summation order of Fourier series expansion of the original waveform. As a result, it was confirmed that the extent of induced traction form increases as the extent of asymmetry of the actuated sawtooth waveform increases up to the summation order of 3; however, the induced traction form does not increase in case of n of over 4.

Selectively emissive fluoropolymer film for passive daytime radiative cooling

Passive daytime radiative cooling is an attractive method to reduce overheating and the heat island effect, thus addressing the global warming effect. This technology does not require any input energy, noise, vibrations, and polluting gas to produce sub-ambient temperatures. In this study, we propose a simple passive daytime radiative cooler, composed of a silver back layer and commercial ethylene tetrafluoroethylene film. With many molecular vibration peaks in the sky window and high solar transmittance of ethylene tetrafluoroethylene, the silver-deposited film exhibits only 3.5% solar absorption and 88.6% emissivity in the sky window, resulting in a substantial sub-ambient cooling effect of up to 9.7 °C in outdoor measurements. The theoretical prediction was confirmed to match well with experimental results, and the passive daytime radiative cooling ability of the film was examined using global-scale cooling energy density maps.

A sliding mode control strategy for active horizontal seat suspension under realistic input vibration

In the paper, an innovative active control of a horizontal seat suspension system is discussed in context of realistic input vibration that occurs in the cabins of agricultural tractors. The vibration reduction system is represented by the state-space model and its numerical parameters are determined experimentally. For such a reliable mathematical representation of the system dynamics, the finite-time sliding mode controller is successfully designed for different spectral classes of the random excitation signal. A multi-objective control strategy is implemented in order to satisfy opposite requirements, that is, at the limited value of active force, a horizontal vibration of the seated human body is considerably reduced, but the suspension travel does not exceed unacceptable stroke of the system. Laboratory measurements of the seated human body have shown improved comfort of drivers under fore-and-aft vibrations.

Rotating Machinery Fault Diagnosis Using HHO-RSSD and RCGmvMAAPE

Rotating machinery has played an enormous role in industrial production, and its stable operation is related to whether production can proceed smoothly. At present, multichannel entropy-based methods are usually be adopted to analyze multichannel vibration signals. However, the collected signal may only have one channel in the actual situation. At this time, analyzing only a single channel signal cannot effectively utilize the advantages of multivariate analysis. For this reason, this paper presents a novel multivariate analysis approach and applies it to the fault diagnosis of machinery. Firstly, the parameter-optimized resonance sparse decomposition (RSSD) algorithm is adopted to decompose the single-channel vibration signal into high and low resonance components. Then, the two components are regarded as dual-channel vibration signals and input into the refined composite generalized multivariate multiscale amplitude aware permutation entropy (RCGmvMAAPE) method to gain fault features. Eventually, the features are input to the deep belief network (DBN) classifier to perform fault judgment. The experiments of rotating machinery are carried to verify the effectiveness of the developed approach. The results display that the proposed fault diagnosis method can achieve the classification accuracy of 100% and 98% when only a single-channel vibration signal is used, which is better than the fault diagnosis method based on a multichannel vibration signal and enjoys strong stability.

Vibration Model of a Power Capacitor Core under Various Harmonic Electrical Excitations

Power capacitors are widely used in power transmission systems. During their operation, an electric force acting on the electrodes of the power capacitors actuates mechanical vibrations and radiates an audible noise. Considering a power capacitor as a general system, the frequency response with the electric force as the input and mechanical vibration as the output have been measured by engineers in recent years and used to evaluate the acoustic and mechanical features of products. Accidentally, it was found that the frequency of the capacitor vibration was not consistent with its excitation due to electro-mechanical coupling. This electro-mechanical coupling had not been considered in previous vibration models of power capacitors. Therefore, a new vibration model of power capacitors was built up in this paper and a so-called multi-frequency vibration characteristic was revealed. A theoretical analysis showed that the electric force and mechanical vibration of the power capacitors were coupled, which resulted in the multi-frequency vibration. The vibration frequency response was measured and the result was consistent with the vibration model proposed in this paper. Once the frequency of the electric force was near half the natural frequency of the power capacitor, a predominant multi-frequency vibration was triggered and the power capacitor was in a superharmonic resonance.

Design, modeling and testing of a vibration absorption device with energy harvesting based on force amplifier and piezoelectric stack

This article presents the design, modeling and testing of a novel vibration absorption device with energy harvest based on compliant mechanism and piezoelectric stack. The vibration absorption device can absorb external vibration with high bandwidth through a hybrid compliant mechanism. Meanwhile, the mechanical energy of the vibration can be converted into electrical energy by piezoelectric stack. The hybrid compliant mechanism contains a bridge type force amplifier and a lever type force amplifier both based on flexure hinges. The analytical model is established for predicting the force amplification ratio and the output electricity power. Also, the dimensions of the device are optimized. A prototype is fabricated and tested with input vibration at different frequencies. The experimental results are well identical with the analytical model. In addition, the proposed vibration absorption device has better performance by comparing with existing designs.

Train-induced floor vibration and structure-borne noise predictions in a low-rise over-track building

Frequent train operations in metro depots can have adverse effects on the buildings’ occupants in terms of feelable vibration and noise. A method is proposed to predict vibration transmissions from columns into girders and subsequently into the floors. This method is quite efficient in modeling and computation, saving engineers time and computational cost. It is highly useful in the design phase for identifying undesirable feelable vibration and audible noise within buildings and for developing mitigation measures that improve human comfort, operation of sensitive equipment, and manufacturing.Train-induced ground-borne vibration in metro depots transmits into the upper floors of over-track buildings primarily through axial waves in the supporting columns. The vertical vibration of a column at a floor inputs mechanical power into the attached girders based on their impedance at the column. An analytical model of the girder impedance is developed that accounts for the coupling to the floor and for composite action where in-plane deformation in the floor stiffens the girder. Along with the measured vibration velocity levels at the columns, impedances of the coupled floor and girders are used to predict the mechanical power input at individual columns into the girders. The input mechanical power generates bending waves in the girders with subsequent transmission out into the attached floor along their length. The resulting average floor vibration levels in the bay are predicted in response to the total mechanical power input, which in turn radiate noise from the floor structure into the room.The overall model from vibration inputs at the columns to room noise levels was applied to a 4-story over-track building during train passbys under the building in the Qianhai Metro Depot in Shenzhen, China. The predicted average floor vibration levels and room noise levels were in good agreement with their corresponding measurements.