Carlos De Marqui

Piezoaeroelastic Modeling and Analysis of a Generator Wing with Continuous and Segmented Electrodes

Unmanned air vehicles (UAVs) and micro air vehicles (MAVs) constitute unique application platforms for vibration-based energy harvesting. Generating usable electrical energy during their mission has the important practical value of providing an additional energy source to run small electronic components. Electrical energy can be harvested from aeroelastic vibrations of lifting surfaces of UAVs and MAVs as they tend to have relatively flexible wings compared to their larger counterparts. In this work, an electromechanically coupled finite element model is combined with an unsteady aerodynamic model to develop a piezoaeroelastic model for airflow excitation of cantilevered plates representing wing-like structures. The electrical power output and the displacement of the wing tip are investigated for several airflow speeds and two different electrode configurations (continuous and segmented). Cancelation of electrical output occurs for typical coupled bending-torsion aeroelastic modes of a cantilevered generator wing when continuous electrodes are used. Torsional motions of the coupled modes become relatively significant when segmented electrodes are used, improving the broadband performance and altering the flutter speed. Although the focus is placed on the electrical power that can be harvested for a given airflow speed, shunt damping effect of piezoelectric power generation is also investigated for both electrode configurations.

Modeling and Analysis of Piezoelectric Energy Harvesting From Aeroelastic Vibrations Using the Doublet-Lattice Method

Multifunctional structures are pointed out as an important technology for the design of aircraft with volume, mass, and energy source limitations such as unmanned air vehicles (UAVs) and micro air vehicles (MAVs). In addition to its primary function of bearing aerodynamic loads, the wing/spar structure of an UAV or a MAV with embedded piezoceramics can provide an extra electrical energy source based on the concept of vibration energy harvesting to power small and wireless electronic components. Aeroelastic vibrations of a lifting surface can be converted into electricity using piezoelectric transduction. In this paper, frequency-domain piezoaeroelastic modeling and analysis of a cantilevered platelike wing with embedded piezoceramics is presented for energy harvesting. The electromechanical finite-element plate model is based on the thin-plate (Kirchhoff) assumptions while the unsteady aerodynamic model uses the doublet-lattice method. The electromechanical and aerodynamic models are combined to obtain the piezoaeroelastic equations, which are solved using a p-k scheme that accounts for the electromechanical coupling. The evolution of the aerodynamic damping and the frequency of each mode are obtained with changing airflow speed for a given electrical circuit. Expressions for piezoaeroelastically coupled frequency response functions (voltage, current, and electrical power as well the vibratory motion) are also defined by combining flow excitation with harmonic base excitation. Hence, piezoaeroelastic evolution can be investigated in frequency domain for different airflow speeds and electrical boundary conditions.

Electroaeroelastic analysis of airfoil-based wind energy harvesting using piezoelectric transduction and electromagnetic induction

The concept of transforming aeroelastic vibrations into electricity for low-power generation has received growing attention in the last few years. The goal is to convert airflow energy into electricity for powering small electronic components employed in wireless applications. The potential applications for aeroelastic energy harvesting range from aircraft structures to several engineering problems involving wireless electronic components located in high wind areas. The use of a typical airfoil section is a convenient approach to create instabilities and persistent oscillations in aeroelastic energy harvesting. This article analyzes two airfoil-based aeroelastic energy harvesters using (a) piezoelectric transduction and (b) electromagnetic induction. An airfoil with two degrees of freedom is investigated by adding piezoelectric and electromagnetic couplings to the plunge degree of freedom in two separate cases. The governing dimensionless electroaeroelastic equations are given in each case with a resistive load in the electrical domain for predicting the power output at the flutter boundary. The effects of several dimensionless system parameters on the dimensionless electrical power output as well as the dimensionless linear flutter speed are investigated for piezoelectric and electromagnetic energy harvesting from airflow-induced vibrations. The simulations presented in this study can be employed for designing and optimizing airfoil-based wind energy harvesters.

Macro-Fiber Composite Actuators for Flow Control of a Variable Camber Airfoil

This research employs solid-state actuators for delay of flow separation seen in airfoils at low Reynolds numbers. The flow control technique investigated here is aimed for a variable camber airfoil that employs two active surfaces and a single four-bar (box) mechanism as the internal structure. To reduce separation, periodic excitation to the flow around the leading edge of the airfoil is induced by a total of nine piezocomposite actuated clamped-free unimorph benders distributed in the spanwise direction. An electromechanical model is employed to design an actuator capable of high deformations at the desired frequency for lift improvement at post-stall angles. The optimum spanwise distribution of excitation for increasing lift coefficient is identified experimentally in the wind tunnel. A 3D (non-uniform) excitation distribution achieved higher lift enhancement in the post-stall region with lower power consumption when compared to the 2D (uniform) excitation distribution. A lift coefficient increase of 18.4% is achieved with the identified non-uniform excitation mode at the bender resonance frequency of 125 Hz, the flow velocity of 5 m/s and at the reduced frequency of 3.78. The maximum lift (Clmax) is increased 5.2% from the baseline. The total power consumption of the flow control technique is 639 mWRMS.

Piezoceramic Composite Actuators for Flow Control in Low Reynolds Number Airflow

The research presented here employs solid-state actuators for flow separation delay or for forced attachment of separated flow seen in airfoils at low Reynolds numbers. To reduce separation, periodic excitation to the flow around the leading edge of the airfoil is induced by Macro-Fiber Composite actuated clamped-free unimorph benders. An electromechanical model of the unimorph is briefly presented and parametric study is conducted to aid the design of a unimorph to output high deformation at a desired frequency. The optimum frequency and amplitude for lift improvement at post-stall angles are identified experimentally. Along with aerodynamic force and structural displacement measurements, helium bubble flow visualization is used to verify existing separated flow, and the attached flow induced by flow control. The lift enhancement induced by several flow control techniques is compared. A symmetric and non-uniform (3D) flow excitation results in the maximum lift enhancement at post-stall region at the lowest power consumption level. A maximum lift coefficient increase of 27.5% (in the post-stall region) is achieved at 125 Hz periodic excitation, with the 3D symmetric actuation mode at 5 m/s and the reduced frequency of 3.78. Cl, max is increased 7.6% from the baseline.

Nonlinear Dynamic Model and Simulation of Morphing Wing Profile Actuated by Shape Memory Alloys

Morphing aircraft have the ability to actively adapt and change their shape to achieve different missions efficiently. The development of morphing structures is deeply related with the ability to model precisely different designs in order to evaluate its characteristics. This paper addresses the dynamic modeling of a sectioned wing profile (morphing airfoil) connected by rotational joints (hinges). In this proposal, a pair of shape memory alloy (SMA) wires are connected to subsequent sections providing torque by reducing its length (changing airfoil camber). The dynamic model of the structure is presented for one pair of sections considering the system with one degree of freedom. The motion equations are solved using numerical techniques due the nonlinearities of the model. The numerical results are compared with experimental data and a discussion of how good this approach captures the physical phenomena associated with this problem.

Finite Element Analysis of a UAV Wing Spar with Piezoceramics for Vibration Energy Harvesting

The research goal in vibration-based energy harvesting is to convert waste vibration energy available in the environment of remotely operated systems or wireless systems with limited energy sources to usable electrical energy. Unmanned Air Vehicles (UAVs) and Micro Air Vehicles (MAVs) constitute unique applications for vibration-based energy harvesting. An additional energy source to run small electronic devices during the flight has the practical value of relieving auxiliary power sources of such systems. Aspect ratios of piezoelectric harvesters in several cases are plate-like and predicting the power output to general (symmetric and asymmetric) excitations requires a plate-type formulation. In this paper, an electromechanically coupled finite element (FE) plate model is presented for predicting the electrical power output of piezoelectric energy harvester plates. Generalized Hamilton’s principle for electroelastic bodies is reviewed and the FE model is derived based on the Kirchhoff plate assumptions as typical piezoelectric energy harvesters are thin structures. Presence of conductive electrodes is taken into account in the FE model. The predictions of the FE model are verified against the analytical solution for a unimorph cantilever and then against the experimental and analytical results of a bimorph cantilever with a symmetric tip mass reported in the literature. The electromechanical behavior of a bimorph cantilever with an asymmetric tip mass is also investigated. Cancellation of the potential of electrical energy that can be extracted from torsional modes is investigated when continuous electrodes are used. Possible solutions to avoid the cancellation of electrical output are discussed in this paper. Finally, an optimization problem is solved where the aluminum wing spar of a UAV is modified to obtain a generator spar by embedding piezoceramics for the maximum electrical power without exceeding a prescribed mass addition limit.

Effect of segmented electrodes on piezo-elastic and piezo-aero-elastic responses of generator plates

In this paper, the use of segmented electrodes is investigated to avoid cancellation of the electrical outputs of the torsional modes in energy harvesting from piezo-elastic and piezo-aero-elastic systems. The piezo-elastic behavior of a cantilevered plate with an asymmetric tip mass under base excitation is investigated using an electromechanically coupled finite element (FE) model. Electromechanical frequency response functions (FRFs) are obtained using the coupled FE model both for the continuous and segmented electrodes configurations. When segmented electrodes are considered torsional modes also become significant in the resulting electrical FRFs, improving broadband (or varying-frequency excitation) performance of the generator plate. The FE model is also combined with an unsteady aerodynamic model to obtain the piezo-aero-elastic model. The use of segmented electrodes to improve the electrical power generation from aeroelastic vibrations of plate-like wings is investigated. Although the main goal here is to obtain the maximum electrical power output for each airflow speed (both for the continuous and segmented electrode cases), piezoelectric shunt damping effect on the aeroelastic response of the generator wing is also investigated.Copyright

Experimental study on the aeroelastic behavior of a typical airfoil section with superelastic shape memory alloy springs

An experimental study on the aeroelastic behavior of a 2-degree-of-freedom typical airfoil section with superelastic shape memory alloy springs is reported. Shape memory alloy helical springs are included in the pitch degree-of-freedom of the typical section so that the effects of pseudoelastic hysteresis on the aeroelastic behavior of the system can be investigated. The experimental identification of the aeroelastic parameters is described. Wind tunnel tests are conducted for different shape memory alloy springs’ preload levels, airflow speeds, and initial conditions. It is shown that the linear unstable post-flutter behavior is transformed into stable limit cycle oscillations of acceptable amplitudes over a range of airflow speeds due to pseudoelastic hysteresis. Therefore, shape memory alloy springs can be effectively exploited to passively enhance the aeroelastic behavior of a typical section.An experimental study on the aeroelastic behavior of a 2-degree-of-freedom typical airfoil section with superelastic shape memory alloy springs is reported. Shape memory alloy helical springs are included in the pitch degree-of-freedom of the typical section so that the effects of pseudoelastic hysteresis on the aeroelastic behavior of the system can be investigated. The experimental identification of the aeroelastic parameters is described. Wind tunnel tests are conducted for different shape memory alloy springs’ preload levels, airflow speeds, and initial conditions. It is shown that the linear unstable post-flutter behavior is transformed into stable limit cycle oscillations of acceptable amplitudes over a range of airflow speeds due to pseudoelastic hysteresis. Therefore, shape memory alloy springs can be effectively exploited to passively enhance the aeroelastic behavior of a typical section.

Non-Linear Modeling and Analysis of Composite Helicopter Blade for Piezoelectric Energy Harvesting

Converting aeroelastic vibrations into electricity for low-power generation has received growing attention over the past few years. Helicopter blades with embedded piezoelectric elements can provide electrical energy to power small electronic components. In this paper, the non-linear modeling and analysis of an electromechanically coupled cantilevered helicopter blade is presented for piezoelectric energy harvesting. A resistive load is considered in the electrical domain of the problem in order to quantify the electrical power output. The non-linear electromechanical model is derived based on the Variational-Asymptotic Method (VAM). The coupled non-linear rotary system is solved in the time-domain. A generalized-α integration method is used to guarantee numerical stability, adding numerical damping at high frequencies. The electromechanical behavior of the coupled rotating blade is investigated for increasing rotating speeds (stiffening effect).Copyright