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Showing papers by "Shaikh Faruque Ali published in 2017"


Journal ArticleDOI
TL;DR: In this article, the authors derived analytical closed form expressions for the magneto-elastic potential and the nonlinear restoring forces in the system, assuming a single mode approximation, taking into account the effect of linear elastic and nonlinear magnetic forces.

40 citations


Journal ArticleDOI
TL;DR: In this paper, an array of pendulums as a potential broadband energy harvester is investigated and closed form expression of the total power is analyzed numerically, and the effect of parameters on the total energy harvested and on frequency band of the harvested power is accessed numerically.
Abstract: This article investigates an array of pendulums as a potential broadband energy harvester. Closed form expression of the total power is analytically obtained. Effect of parameters on the total power harvested and on frequency band of the harvested power is accessed numerically. Finally experiments are carried out for arrays with two to five pendulums, which strongly supports the numerical observations. Different configurations are studied; (a) pendulums in the array are independent of each other, (b) pendulums are coupled using springs in between. The effect of mechanical grounding, where in the extreme pendulums are connected to the support through a spring, is also investigated. Observations show that array of coupled pendulums with mechanical grounding increased the bandwidth of harvesting frequency. The bandwidth and the total power harvested saturates with the number of pendulums.

27 citations


Journal ArticleDOI
TL;DR: In this article, a low frequency magneto-mechanically coupled energy harvesting system is proposed to increase the power magnitude and bandwidth simultaneously, where two pendulums are magnetically and mechanically coupled.
Abstract: A low frequency magneto-mechanically coupled energy harvesting system is proposed to increase the power magnitude and bandwidth simultaneously. The system consists of two pendulums that are magnetically and mechanically coupled. The analytical formulation for the coupled system is developed based on the extended Lagrangian formulation. The experimental and simulated results are reported. The results exhibiting the benefits of magneto-mechanical coupling are reported. The experiments show an increment of 30.69% in the power magnitude and 100% enhancement in the bandwidth when compared to independent harvesters even at a low amplitude of excitation. Moreover, Chaos is observed at low frequency and at a low amplitude, which tends to provide larger bandwidths with more power.

25 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the gap between the cylinder and the flapper on the energy harvested was investigated through wind tunnel experiments and numerical simulations, and it was shown that the choice of gap influences the energy harvesting potential of such harvesters.
Abstract: This study investigates energy harvesting from vortex induced vibrations of a flexible cantilevered flapper placed in the wake of a rigid circular cylinder. The effect of the gap between the cylinder and the flapper on the energy harvested is investigated through wind tunnel experiments and numerical simulations. As the flow speed is varied, a transition in the flapper dynamics is observed, which in turn affects the power extracted by the harvester. Numerical investigations reveal that the flapper dynamics is different depending on whether the vortices are shed ahead or behind the flapper. This study concludes that the choice of the gap influences the energy harvesting potential of such harvesters.

24 citations


Book ChapterDOI
01 Jan 2017
TL;DR: In this paper, a comparison between the harvesting capabilities of different electroactive polymers and the challenges faced are discussed to draw an overall picture on energy harvesting from conductive and crystalline polymers.
Abstract: Modern electronic devices require less energy on-board and could be powered by energy harvested from the environment. Mechanical vibrations are attractive sources for energy harvesting due to their high availability in technical environments. Among the various mechanisms available to convert mechanical energy into electrical energy, piezoelectric transduction offers high power density at microenergy scales. In piezoelectric energy harvesters, the amount of electrical energy harvested directly depends on the strain undergone by the transducer. Commonly used piezoelectric transducers are made of perovskite ceramics such as PZT and are brittle. This limits the maximum allowable strain in the harvester and consequently the power harvested. In such cases, electroactive polymers act as viable alternatives due to their flexibility. Energy harvesting from conductive and crystalline electroactive polymers is explored in this chapter. Crystalline polymers such as polyurethane and semicrystalline polymers such as PVDF are commonly used in energy harvesting devices owing to their flexibility, affordability, and good electromechanical coupling properties. This chapter begins with a brief account on the material properties of PVDF and polyurethane. Subsequently, design of energy harvesters based on these materials is elucidated. A short note on energy harvesting from crystalline biopolymers such as cellulose nanocrystals is also included therein. Such harvesters are attractive as they are environment friendly and biocompatible. Among conductive polymer composites, harvesters based on polyaniline and carbon nanotubes are described. A comparison between the harvesting capabilities of different electroactive polymers and the challenges faced are discussed to draw an overall picture on energy harvesting from electroactive polymers.

7 citations


Proceedings ArticleDOI
01 Jan 2017
TL;DR: In this paper, a magnetorheological fluid based semi active damper is proposed to alleviate ground resonance in a helicopter and a nonlinear dynamic inversion based control law is designed to monitor the voltage of the damper directly based on the feedback from the blades.
Abstract: Ground resonance is an aero-mechanical instability that occurs in soft in-plane rotors where there is a coalescence of low frequency lead-lag motions of the blade with that of the frequencies of the fuselage, when on ground. Such a coalescence results in violent oscillations of the fuselage and can prove catastrophic to the helicopter if not reduced in time. The present work focuses on a nonlinear control strategy to alleviate ground resonance in helicopters. In this work, a magnetorheological (MR) fluid based semi active damper is proposed. Nonlinear dynamic inversion based control law is designed to monitor the voltage of the MR damper directly based on the feedback from the blades. The damper dynamics is integrated into the classical ground resonance model and its performance is assessed to control the unstable rotor.

3 citations


Proceedings ArticleDOI
01 Dec 2017
TL;DR: It is proposed that a finite time control effort can be applied to the system states, once per period, to bring back the chaotic trajectory to the desired orbit so as to stabilize it.
Abstract: This manuscript presents a novel method of creating and stabilizing limit cycles in a chaotic attractor. Chaos control techniques such as the OGY and OPF techniques apply small perturbations to a system parameter to stabilize an unstable periodic orbit present in a chaotic attractor. But it may happen that the system parameters may not be available for control. For example, in structural systems, it is difficult to alter their geometry and material properties in real-time, so as to suppress chaos. In such cases, use of state feedback control will provide ease of implementation. But impulse-like small perturbations, prescribed by the OGY technique, applied as a feedback to the state equations cannot drive the system from its current state to the desired state. A proper control law must be devised to drive the system from one state to another. Hence, we propose that a finite time control effort can be applied to the system states, once per period, to bring back the chaotic trajectory to the desired orbit so as to stabilize it. The implementation of the proposed technique is demonstrated with the help of a bistable Duffing oscillator in this manuscript. It is shown through numerical simulations that the proposed technique is able to stabilize periodic orbits passing through a prescribed set of points lying in the chaotic attractor of a Duffing oscillator.

2 citations


Proceedings ArticleDOI
01 Dec 2017
TL;DR: This paper presents active morphing and vibration control of thin cantilever plates using an array of piezoelectric sensor and actuator system and Dynamic Inversion technique is used to determine the control variables to morph the plate and suppress its vibrations.
Abstract: This paper presents active morphing and vibration control of thin cantilever plates using an array of piezoelectric sensor and actuator system The piezoelectric actuators and sensors are used to form a feedback control loop to suppress the undesired vibrations caused during configuration change Dynamic Inversion technique is used to determine the control variables to morph the plate and suppress its vibrations The partial differential equations governing the plate deformation and piezoelectric actuation are solved using projection method to obtain algebraic equations, following Design-then-Approximate (DTA) method Two configurations are considered from its eigenspace to perform simulations The actuators are designed for both morphing and vibration control since thin plates have poor damping characteristics and need external damping The displacement norm and velocity norm time histories and the configuration achieved by the system are analysed