The tuned vibration absorber (TVA) can significantly reduce the vibration of the primary system when it is tuned to the excitation frequency. When it is mistuned, the TVA does not work. In recent years, the adaptive tuned vibration absorbers have been studied to broaden the bandwidth of the conventional absorber. An adaptive TVA usually has a variable stiffness element. By adjusting the stiffness, the absorber natural frequency is changed too. Variable mass is also used in some TVA designs. However, we have to make the stiffness (or mass) of the absorber changes over a much wider range if we want to obtain a wider bandwidth, because the natural frequency of the absorber and the TVA stiffness (and mass) are nonlinearly related. In order to solve this problem, a hybrid vibration absorber based on variable mass and variable stiffness is studied, while its control plan is investigated in this paper. Some simulations are carried out to test the performance of the absorber and the control plan. The result shows that the new hybrid vibration absorber can markedly broaden the effective frequency bandwidth of the absorber and reduce the vibration of the primary system.
This paper focuses on dynamical response characteristics of a flywheel mechanical hybrid powertrain (FMHP), comprising a continuously variable transmission (CVT) and a flywheel integrated into a conventional vehicle with an internal combustion engine. Having unique at-tractive features such as low cost, easy implementation to existing conventional vehicles, high fuel saving potential and mechanical maintenance-free long lasting components, FMHP is a very strong contender among other electric based hybrid powertrain solutions, especially for short-term and low investment conditions. FMHP is able to provide most important features of hybridization for fuel saving, that is regenerative braking, ICE load shifting for elimination of inefficient part load operation and engine shut-off during standstill. In the literature, promis-ing results can be found about the fuel saving potential of the FMHP, mostly based on quasi-static drive cycle simulations. Various case studies and parameter studies exist, investigating the effect of gear ratio spread/selection, energy management strategy and powertrain layout. Hence it is addressed to discover/surpass fuel saving potential as much as possible although diminishing results may be obtained due to high progress already made, thus to the authors' knowledge dynamic response of powertrain on those studies is neglected and a dedicated study/investigation of it does not exist in the literature. This paper introduces key dynamical properties and possible solutions as a starting point including throttle and brake response in addition to driver modelling for throttle and brake response evaluation, delay characteristics and delay compensation algorithms with blended braking, furthermore drivetrain stiff-ness/damping properties and controller design for preventing oscillations and jerk for driver comfort. A quasi-static simulation of FMHP is also included without dynamics, for compari-son of fuel saving capability with dynamical properties presented here, which is left for future work.
Vehicle ride is still one of the most important factors in the vehicle design. In this paper the application of a disturbance observer based (DOB) control algorithm is proposed to improve the vehicle ride performance of a vehicle that has magnetorheological damper (MR Damper) suspension. Vehicle is modeled as a quarter car model by employing Bouc-Wen model of the MR damper. Control performance of the proposed algorithm is compared to previously published skyhook algorithm under various road conditions using simulations. Integral Square Error criterion (ISE) is used to compare the performance of the control algorithms. The simulation results show that the application of the proposed algorithm effectively improves the vehicle ride.
When the magnetic flux is changed due to the motion of conductor within the applied magnetic field, eddy currents are generated in the conductor, which introduce their own magnetic field opposing in the nature of the applied magnetic field. This opposite magnetic field tries to overcome the change in magnetic flux. Using this concept an Eddy Current Damper is developed in which the conductor is a copper tube and magnetic field is generated by electromagnets of various dimensions. This damper is hybrid in nature as the damping effect is considered because of electromagnets as well as that of springs. This damper can be used to provide non- contact damping effects that will be advantageous for avoiding extra mass, friction and stiffness. This damper is tested on the Damping-testing machine and results so obtained are found in good agreement with those available in the literature. There are several different methods of inducing a time-varying magnetic field, and from each method arises the potential for a different type of damping system. Therefore, the research into eddy current and magnetic damping mechanisms have led to a diverse range of dampers, the factor which effects the magnetic field in eddy current based damper which is detailed discussed in this paper.
Tunable vibration absorber with liquid elastic chamber (TVA-LEC) is a novel device for structural vibration suppression. The TVA-LEC consists of a rigid cylindrical chamber covered with two rubber membranes to provide stiffness, and liquid inside to provide inertia. In this paper, we present an approach based on the piezoelectric effect to convert the TVA-LEC to an energy harvester, which can be used to supply power to other devices, such as IoT sensors. First, the design of this energy harvester is described. An array of cantilever beams is connected to the inner wall of the rigid cylindrical chamber. Then piezoelectric ceramic patches are attached to the beams to absorb the vibration induced by the liquid flow when the TVA-LEC vibrates. Next, an analytical model is developed to predict both the natural frequency and the voltage generated by this device. The nonlinear liquid impact term is linearized according to the principle that equal works are done within one complete cycle of vibration. Finally, experiments are carried out on an electrodynamic shaker to obtain the energy harvesting efficiency with different excitation frequency. The experimental results agree with the prediction.
Harvesting the widely propagated sound energy, especially from the low-frequency indus-try noise, may drive portable devices and wireless sensors conveniently. However, it's a daunting challenge to harvest low energy density and long-wavelength sound waves with small-scale devices. As acoustic metamaterials can manipulate sound waves in the sub-wavelength scale, the acoustic energy harvester (AEH) based on the metamaterials can be compact and may work efficiently. In this work, we propose an AEH system includes two critically coupled membrane-type acoustic metamaterials (AMs) and a ring-type piezoelec-tric energy-transducer inserted in. At the working frequencies, the coupled AM increasing the density of sound energy dramatically and the transducer can convert sound energy into electric energy. The simulated results of the finite element model show that the aperture of the transducer can increase the efficiency of the sound energy conversion but cause nonlin-ear phenomenon. An experiment was carried out in an acoustic impedance tube to verify effects of the LAM system.
With the ACARE directives on aircraft noise reductions for 2050, aircraft turbofan engines acoustic liners will have to overcome contradictory goals: to guarantee an efficiency at low frequencies while reducing treated surface area and liners thickness. The purpose of this paper is to present some concept reviews in the development of transducers-based acoustic liners. The use of transducers enables the coupling of several physical domains: acoustics, mechanics and electronics. As shown in former work, this can lead to highly efficient devices enabling low frequency absorption with thin liners with or without flow. The present work aims to better understand the key phenomena governing acoustic absorption and frequency range available for a given liner thickness and several transductions such as electrodynamic, electrostatic and piezoelectric. The effects of adding an electronic shunt circuit and using several transduction principles on the absorption level and bandwidth are discussed. In order to study several types of transductions, Finite Element Method and Lumped Element Method modelisations have both been developped but only the second one is used in this paper. The transductions are compared considering absorption efficiency due to the shapes of the devices on one hand and to the possibilities offered by the connection to an electrical impedance in terms of absorption enhancement and/or frequency shift on the other hand. Some perspectives are given in terms of structures optimization, electrical shunt impedances choices and expected absorption efficiency.
