Showing papers by "Shaikh Faruque Ali published in 2015"

Analysis of energy harvesting from multiple pendulums with and without mechanical coupling

Abstract: Multiple energy harvesters in a single device has become important to harvest enough power for sensors. In such situation presence of mistuning may change the performance of the overall system. This paper studies the issue of presence of mistuning in such system and also extend the study to performance evaluation when mechanically coupling is present between the multiple harvesters. A simple case of two pendulums in a same frame is analysed for electromagnetic energy harvesting. Experiments are carried out to support the numerical evaluation. The study limits its observations to low frequency and low amplitude motions. The observation made are very interesting and intricate.

Dynamic response mitigation of floating wind turbine platforms using tuned liquid column dampers.

Abstract: In this paper, we experimentally study and compare the effects of three combinations of multiple tuned liquid column dampers (MTLCDs) on the dynamic performance of a model floating tension-leg platform (TLP) structure in a wave basin The structural stability and safety of the floating structure during operation and maintenance is of concern for the performance of a renewable energy device that it might be supporting The dynamic responses of the structure should thus be limited for these renewable energy devices to perform as intended This issue is particularly important during the operation of a TLP in extreme weather conditions Tuned liquid column dampers (TLCDs) can use the power of sloshing water to reduce surge motions of a floating TLP exposed to wind and waves This paper demonstrates the potential of MTLCDs in reducing dynamic responses of a scaled TLP model through an experimental study The potential of using output-only statistical markers for monitoring changes in structural conditions is also investigated through the application of a delay vector variance (DVV) marker for different conditions of control for the experiments

Broadband Vibration Energy Harvesting from a Vertical Cantilever Piezocomposite Beam with Tip Mass

Abstract: 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 nonlinearity 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 nonlinear properties of the system using base excitation in conjunction with the tip mass at the end of the beam. Such a 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.

The effect of noise on the response of a vertical cantilever beam energy harvester

Abstract: An energy harvesting concept has been proposed comprising a piezoelectric patch on a vertical cantilever beam with a tip mass. The cantilever beam is excited in the transverse direction at its base. This device is highly nonlinear with two potential wells for large tip masses, when the beam is buckled. For the pre-buckled case considered here, the stiffness is low and hence the displacement response is large, leading to multiple solutions to harmonic excitation that are exploited in the harvesting device. To maximise the energy harvested in systems with multiple solutions the higher amplitude response should be preferred. This paper investigates the amplitude of random noise excitation where the harvester is unable to sustain the high amplitude solution, and at some point will jump to the low amplitude solution. The investigation is performed on a validated model of the harvester and the effect is demonstrated experimentally. c

Piezomagnetoelastic broadband energy harvester: Nonlinear modeling and characterization

Abstract: Piezomagnetoelastic energy harvesters are one among the widely explored configurations to improve the broadband characteristics of vibration energy harvesters. Such nonlinear harvesters follow a Moon beam model with two magnets at the base and one at the tip of the beam. The present article develops a geometric nonlinear mathematical model for the broadband piezomagnetoelastic energy harvester. The electromechanical coupling and the nonlinear magnetic potential equations are developed from the dimensional system parameters to describe the nonlinear dynamics exhibited by the system. The developed model is capable of characterizing the monostable, bistable and tristable operating regimes of the piezomagnetoelastic energy harvester, which are not explicit in the Duffing representation of the system. Bifurcations and attractor motions are analyzed as nonlinear functions of the distance between base magnets and the field strength of the tip magnet. The model is further used to characterize the potential wells and stable states, with due focus on the performance of the system in broadband energy harvesting.

Energy Harvesting from Near Periodic Structures

Abstract: 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.

Performance of a Single Liquid Column Damper for the Control of Dynamic Responses of a Tension Leg Platform

Abstract: Tuned liquid column dampers have been proved to be successful in mitigating the dynamic responses of civil infrastructure. There have been some recent applications of this concept on wind turbines and this passive control system can help to mitigate responses of offshore floating platforms and wave devices. The control of dynamic responses of these devices is important for reducing loads on structural elements and facilitating operations and maintenance (O&M) activities. This paper outlines the use of a tuned single liquid column damper for the control of a tension leg platform supported wind turbine. Theoretical studies were carried out and a scaled model was tested in a wave basin to assess the performance of the damper. The tests on the model presented in this paper correspond to a platform with a very low natural frequency for surge, sway and yaw motions. For practical purposes, it was not possible to tune the liquid damper exactly to this frequency. The consequent approach taken and the efficiency of such approach are presented in this paper. Responses to waves of a single frequency are investigated along with responses obtained from wave spectra characterising typical sea states. The extent of control is quantified using peak and root mean squared dynamic responses respectively. The tests present some guidelines and challenges for testing scaled devices in relation to including response control mechanisms. Additionally, the results provide a basis for dictating future research on tuned liquid column damper based control on floating platforms.