Shaikh Faruque Ali

This paper presents active vibration control and morphing of thin plates using an array of piezoelectric actuator-sensor system whose locations are determined by optimization. The sudden application of control input for morphing leads to unwanted vibrations which are suppressed using the piezoelectric actuator-sensor couples, which form a feedback control loop. Dynamic Inversion technique is used to determine the control inputs to morph the plate and to suppress the vibrations in the process. The Dynamic Inversion controlled system is compared to uncontrolled system and as a reference, the results are compared with that of Linear Quadratic Controller. The partial differential equations governing the behaviour of plate and piezoelectric actuation are solved using lower dimensional projection method, following Design-then-Approximate (DTA) method, which will reduce spillover effects. Two reference configurations are considered to perform simulations. The actuators are designed for both vibration control and morphing since thin plates have poor damping characteristics and need external damping. The displacement, velocity and error norm time histories are analysed and the configuration achieved by the system by both controllers are compared.

An inverted cantilevered beam vibration energy harvester with a tip mass is evaluated for its electromechanical efficiency and power output capacity in the presence of pure harmonic, pure random and various combinations of harmonic and random base excitation cases. The energy harvester employs a composite piezoelectric material device that is bonded near the root of the beam. The tip mass is used to introduce non-linearity to the system by inducing buckling in some configurations and avoiding it in others. The system dynamics include multiple solutions and jumps between the potential wells, and these are exploited in the harvesting device. This configuration exploits the non-linear properties of the system using base excitation in conjunction with the tip mass at the end of the beam. Such nonlinear device has the potential to work well when the input excitation does not have a dominant harmonic component at a fixed frequency. The paper presents an extensive experimental analysis, results and interesting conclusions derived directly from the experiments supported by numerical simulations. Copyright © 2013 by ASME.

Nano-piezoelectric energy harvesters, due to their ability to convert mechanical vibrations to electrical current, are apt candidates for self-powered NEMs devices. Further, these are strain based electrical potential generators and can be used in tactile devices for accurate position sensing. ZnO, due to its piezoelectric properties and semiconducting nature is the ideal candidate for such applications. This paper proposes an analytical model to explain the potentials generated due to ZnO nano-films on being subjected to different forms of static loading. The model also incorporates the effect of different boundary conditions imposed on the nano-film. A perturbation theory based approach has been used to generate the analytical model. Initially, the strains are calculated ignoring the piezoelectric effect. Later, the electromechanical coupling is taken into consideration and the potentials have been calculated as a second order effect. The finite element simulation results agree with the theory to an accuracy of 5%. The profiles for piezoelectric potential distribution agree also well with the simulations. These piezoelectric potential profiles can also be used in smart materials for obtaining the required deformation in a specimen by applying a similar electrical potential across it.

This paper proposes a novel energy harvesting system model based on combined electromechanical and electromagnetic transduction technique. A cantilever substrate (beam) with piezoelectric (PZT) patch and a mass at the tip is considered for electromechanical transductions. A magnet is hanged through a spring at the tip of the composite beam over a printed circuit board. When the cantilever system is subjected to base excitations, the motion of the magnet relative to a conducting circuit placed near it generates electric energy in the circuit, while the strains induced in the PZT patch will also generate electric energy. In this paper a simplified two-degree of freedom lumped mass model is studied for the analysis of the proposed hybrid harvesting system for harmonic vibration input. Attempts are made to optimize the parameters of the model to get maximum net power generated by the system. © 2013 IEEE.

Geometrically non-linear von Karman plate vibrations are suppressed using optimal dynamic inversion technique. Two types of controller are considered, a continuous and finite discrete controllers in spatial domain to control the vibrations of the plate. Non-linear Finite Element (FE) method is used to transform the non-linear partial differential equations (PDE) into a set of non-linear algebraic equations and are solved. The non-linear PDE is directly used for controller design i.e. design-then-approximate (DTA) method is followed which ensures the stability and controllability of the system. The simuation study shows the effectiveness of controlling plate vibrations using continuous and discrete controllers.

The current aircraft industry, specially unmanned aerial vehicles, is shifting from fixed wing vehicles to morphed wing. Morphing wings can create smoother aerodynamic surfaces, making an aircraft more agile and efficient than an aircraft that flies with many discrete moving surfaces. In present study, a double corrugated variable camber configuration of morphing wing with trailing edge morphing sections are proposed. The two configurations available from literature; one Fish Bone Active camber concept and other is variable camber morphing wing composed of single corrugated structure is considered for comparison of structural and aerodynamic analysis. The structural analysis of all prototype models is done using finite element analysis with actuation mechanism. Aerodynamic analysis is done using two methods; one analytical approach based on thin airfoil theory, and the other one is numerically using XFOIL, which couples a potential-flow panel method with viscous boundary-layer solver. A comparison is done on the basis of stress and deformation developed in various parts of the models. The results show that the double corrugated variable camber morphing configuration can take more structural load without harmful deformation. The aerodynamic analysis also shows that the aerodynamic efficiency of double corrugated variable camber morphing configuration is higher compared to other configurations.

In this research energy harvesting from near periodic structure is discussed. The near periodic system consists of two pendulums connected using a common linear spring. Mistuning in the simple coupled pendulum system is achieved by varying the length of one of the pendulums. Effect of this mistuning on amount of energy harvested is developed analytically and numerically. This will be discussed in this paper and at the same time effect of harvesting on mistuning will be presented. It is shown that with a proper electrical damping, optimal power can be obtained and effect of mistuning can be minimized. Same analysis is carried out with energy harvesting from both the pendulums. In case of harvesting from both the pendulums the harvesting bandwidth is increased and electrical damping required to minimize mistuning is more than that in case of harvesting with mistuned pendulum alone.

In this article two numerical approaches for the shape prediction of a composite wing panel under the combined actuation of a Shape memory alloy (SMA) wire and a Macro fiber composite (MFC) bimorph has been developed. The first approach is a Euler-Bernouilli beam theory based linear finite element iterative scheme and the second approach is a Timoshenko beam theory based nonlinear finite element iterative scheme that takes into account the von Karman strains. The force due to the SMA wire is modeled as a follower force. It is shown that both the techniques developed are capable taking into account this non conservative follower force, while accounting for any additional arbitrary loading. The numerical schemes developed in this paper are validated using the existing techniques while elucidating the lacuna in the existing methods.

Energy harvesting from structural vibration using piezoelectric material has received much attention in the past few years. The idea is to scavenge energy out of a vibrating host. Coupling energy harvesting with structural vibration control is a challenging task due to conflicting goals. But dynamic vibration absorbers (DVA) used to reduce vibrations in the primary structure has potential for energy harvesting capability. In this mechanism the host structure vibration is reduced by suitably shifting the motion to DVA. Vibration energy in DVA can be harvested. The harvested energy can be used to power low-powered wireless sensor systems. This paper analyses the prospect of using vibration absorbers for possible energy harvesting under random excitation. To achieve this goal, vibration absorber is supplemented with a piezoelectric stack for both vibration confinement and energy harvesting. The primary goal is to control the vibration of the host structure and the secondary goal is to harvest energy out of the dynamic vibration absorber simultaneously. It is shown that with a proper choice of harvester parameters a broadband energy harvesting can be obtained combined with vibration reduction in the primary structure. Analytical studies are carried out considering stationary Gaussian white noise excitation within the frequency band of interest. Finally a single storey building under seismic excitation is considered and numerical results of structural control and energy harvested are shown. © 2013 IEEE.

Multiple energy harvesters in a single device has become important to harvest enough power at wider frequencies for sensors. In such situation presence of magnetic force and mechanical coupling may change the performance of the overall system. This paper, studies a simple case of two pendulums in a same frame coupled magnetically and mechanically for electromagnetic broadband energy harvesting under low frequency excitation. The effect of mechanical coupling, frequency and distance between harvesters on bandwidth and magnitude of power are analyzed. The numerical analysis shows that the mechanical coupling with magnetic coupling increases the power magnitude and band width.