Aeroelastic Control Research Articles

강인한 제어기를 이용한 공탄성 시스템의 응답특성

이 논문은 비압축성 유동장에 노출된 2차원 플랩이 있는 날개의 단면에 대한 강인한 공탄성 제어기법을 소개하고 있다. 강인한 제어기는 다목적 상태궤환 합성법을 위해 선형행렬부등식을 이용하여 설계되었다. 제어기의 설계목적은 모델불확실성이 존재하는 상황에서 주파수영역에서의 성능과 시간영역에서의 성능을 함께 만족시키는 것으로 하였다. 수치예제들은 2차원-3자유도 플랩이 있는 날개 단면의 공탄성 응답을 감쇠시키는데 있어서 선형행렬부등식의 접근법의 유효성을 잘 제시하고 있다. This paper presents a robust aeroelastic control methodology of a two dimensional flapped wing system exposed to an incompressible flow field. A robust controller is designed using a linear matrix inequality (LMI) approach for the multiobjective synthesis. The design objectives are to achieve a mix of <TEX>$H_{\infty}$</TEX> performance and H₂ performance satisfying constraints on the closed loop pole locations in the presence of model uncertainties. Numerical examples are presented to demonstrate the effectiveness of LMI approach in damping out the aeroelastic response of 3-DOF flapped wing system.

Active aeroelastic control of 2-D wing-flap systems operating in an incompressible flowfield and impacted by a blast pulse

This paper concerns the active aeroelastic control of 2-D wing-flap systems operating in an incompressible flowfield and exposed to a blast pulse. The goal is to implement an active flap control capability to suppress the flutter instability and enhance the subcritical aeroelastic response to time-dependent external pulses. To this end, a combined control law is implemented and its performances toward suppressing flutter and reducing the vibrational level in the subcritical flight speed range is demonstrated.

Enhanced eigenstructure assignment for aeroelastic control application

A sophisticated robust controller design method for regulation of weakly damped aeroelastic structures using the primary flight controls (PFC) is presented. The approach is based on eigenvalue eigenvector assignment, and is capable of taking into account potentially competing objective specifications in either time or frequency domains, as well as parametric constraints. The infinite set of flight conditions and fuel load distributions lead us to represent the underlying aeroservoelastic plant as a linear multivariable multi-model system, for which a robust output feedback controller is sought in line with technical feasibility, parametric and dynamic uncertainty, architectural and sensor layout constraints. While the method of eigenvalue eigenvector assignment is well known in the fields of flight control design and modal decoupling, here the primary objective is to apply it to constrained simultaneous robust eigenvalue stabilisation. Since the intrinsic controller calculation is implemented as an multiobjective optimisation problem, aeroservoelastic performance specifications can be specified in the problem formulation. The suitability of the resulting low-order static output controller is demonstrated via real-time simulation of a real PFC hardware-in-the loop actuation system, both for normal and degraded configurations.

Enhanced eigenstructure assignment for aeroelastic control application

A sophisticated robust controller design method for regulation of weakly damped aeroelastic structures using the primary flight controls (PFC) is presented. The approach is based on eigenvalue eigenvector assignment, and is capable of taking into account potentially competing objective specifications in either time or frequency domains, as well as parametric constraints. The infinite set of flight conditions and fuel load distributions lead us to represent the underlying aeroservoelastic plant as a linear multivariable multi-model system, for which a robust output feedback controller is sought in line with technical feasibility, parametric and dynamic uncertainty, architectural and sensor layout constraints. While the method of eigenvalue eigenvector assignment is well known in the fields of flight control design and modal decoupling, here the primary objective is to apply it to constrained simultaneous robust eigenvalue stabilisation. Since the intrinsic controller calculation is implemented as an multiobjective optimisation problem, aeroservoelastic performance specifications can be specified in the problem formulation. The suitability of the resulting low-order static output controller is demonstrated via real-time simulation of a real PFC hardware-in-the loop actuation system, both for normal and degraded configurations.

Adaptive control of an aeroelastic flight vehicle using piezoelectric actuators

The paper studies the feasibility of applying piezoelectric actuators to suppress aeroelastic vibrations in a flexible aircraft so that the aeroelastic response can be tailored to comply with specified dynamic performance characteristics. To that end, an adaptive aeroelastic flight vehicle demonstrator concept was designed, developed, manufactured and tested. Closed-loop buffet attenuation, gust response alleviation and flutter suppression results are presented. The performance of the active aeroelastic control approach using piezoelectric actuators is compared to the performance of the aerodynamic control surfaces. Issues related to instrumentation for flight testing are presented as well.

Aeroelastic response of an airfoil-flap system exposed to time-dependent disturbances

Aeroelastic response and control of airfoil-flap system exposed to sonic-boom, blast and gust loads in an incompressible subsonic flowfield are addressed. Analytical analysis and pertinent numerical simulations of the aeroelastic response of 3-DOF airfoil featuring plunging-pitching-flapping coupled motion subjected to gust and explosive pressures in terms of important characteristic parameters specifying configuration envelope are presented. The comparisons of uncontrolled aeroelastic response with controlled one of the wing obtained by feedback control methodology are supplied, which is implemented through the flap torque to suppress the flutter instability and enhance the subcritical aeroelastic response to time-dependent excitations.

Application of Fiber Optic Sensor and Piezoelectric Actuator to Flutter Suppression

Introduction F OR lightweight and flexible structures, it is important to measure and suppress the flow-induced vibrations caused by interactions between fluid and structures. Dynamic aeroelastic instabilities, such as flutter, involve the interaction of aerodynamic, inertia, and elastic forces of flight structures. Because flutter may cause disastrous structural failures in flight, the prediction of stability boundary and the suppression of flutter are very important analysis issues for flight structures. In recent years, several active control strategies have been studied to modify favorably the behavior of aeroelastic systems using smart material and structure technologies. Lazarus et al.1 successfully applied multi-input/multi-output controls to suppress vibration and flutter of a platelike lifting surface with surface-bonded piezoelectric actuators. Han et al.2 performed numerical and experimental investigation on active flutter suppression of a swept-back cantilevered plate. Application of piezoelectric actuation to flutter control of a more realistic wing model was achieved under the Piezoelectric Aeroelastic Response Tailoring Investigation program at NASA Langley Research Center.3 Recently, fiber bragg grating (FBG) sensors have been increasingly studied for a variety of applications: health monitoring, vibration measurement, nondestructive testing and so on. Gratings are simple, intrinsic sensing elements that can be photoinscribed into a silica fiber and have the same advantages normally attributed to fiber sensors. In addition, the devices have an inherent self-referencing capability and are easily multiplexed in a serial fashion along a single fiber.4 An overview of FBG sensors and systems is presented in Ref. 4. This paper investigates dynamic application of an FBG sensor system to the flutter suppression of a composite plate structure. In practical situations, the modeling of an aeroelastic system is complicated and the dynamic characteristics of an aeroelastic system changes with respect to the airflow speed. Therefore, the adaptiveness and the robustness are key features for an aeroelastic control system. A neuroadaptive feedback control algorithm is used in this study. The control system consists of the neuroidentification model and the neurocontroller. The real-time implementation of the adaptive controller is performed using a digital signal processing (DSP) board. The effectiveness of the flutter suppression system is evaluated via wind-tunnel testing.

Modeling and Control for Smart Mesoflap Aeroelastic Control

This paper introduces a novel concept termed Smart Mesoflaps for Aeroelastic Recirculation Transpiration (SMART) to render mass and momentum transfer for controlling shock/boundary-layer interactions in supersonic jet inlets. The SMART concept consists of a matrix of small flaps designed to undergo local aeroelastic deflection to achieve proper mass bleed or injection when subjected to shock loads. To optimize the performance of this system, NiTi shape memory alloy is used as an actuator for the flaps to control the amount of recirculation. The focus of this paper will be the subsystem modeling and control of a single flap. After a relatively detailed model is developed, a simpler model is generated, and it is experimentally shown that this approximation is adequate for control purposes. Next, the control strategy for this subsystem, subject to hysteresis and actuator saturation, is presented. A basic proportional integral derivative (PID) controller is enhanced using a hysteresis compensator (HC) and an error governor (EG). A generalized error governing scheme for PID controllers to compensate for actuator saturations is also developed. This EG method is generalizable to any stable process controlled by a PID. Finally, the PID with HC and the error governing method is experimentally applied to a benchtop SMART subsystem.

Output Feedback Control of the Nonlinear Aeroelastic Response of a Slender Wing

This paper presents the design of optimal constant gain output feedback based controllers for a nonlinear aeroelastic system. Controllers are designed for flutter suppression as well as gust-load alleviation. This controller architecture is one of the simplest, using direct feedback of the sensor outputs, but its performance is highly dependent on sensor selection and placement. Also, optimal design of such controllers require an accurate knowledge of the expected disturbance mode and gust spectrum. This paper presents results pertaining to the performance of SOF controllers for aeroelastic control (linear and nonlinear) and compares it to that of LQR and LQG controllers. Controllers are designed for various sensor placement. The gain and phase margins of the various controllers are also presented to understand the robustness characteristics. For optimal sensor placement and with knowledge of the disturbance, the constant gain output feedback controller performance and robustness was found to be equivalent to that of linear quadratic regulator and linear quadratic Gaussian controllers for the example considered. These controllers were also shown to be very easy to alter and combine with other controllers/filters for better overall system response.

Experimental Aeroelastic Response of Piezoelectric and Aileron Controlled 3D Wing

This paper presents the results of wind tunnel testing performed on a three-dimensional adaptive wing structure. The focus of this study was to test the aeroelastic response and control of a wing built with adaptive stressed skins. The aeroelastic performance of the wing using traditional aerodynamic control surface methods is compared to the results obtained using piezoelectric actuators bonded to the skins of the wing. Smaller piezoelectric sensors also bonded to the wing are used to provide feedback for the control law. Results are presented for the system identification, free stream vibration and buffeting tests performed in the wind tunnel.

Energy Approach to Flutter Suppression and Aeroelastic Control

Energy Approach to Flutter Suppression and Aeroelastic Control

Aeroelastic Control of Smart Composite Plate with Delaminations

In this paper, aeroelastic performance of smart composite wing in the presence of delaminations is investigated. A control system is designed to enhance the dynamic stability of the delaminated composite wing. The refined higher order theory for analyzing an adaptive composite plate in the presence of delaminations is used. The theory accurately captures the transverse shear deformation through the thickness, which is important in anisotropic composites, particularly in the presence of discrete actuators and sensors and delaminations. The effects of delamination on the aeroelastic characteristics of composite plates are investigated. An active control system is designed to redistribute the loads and to minimize the effect of delamination. The pole placement technique is applied to design the closed loop system by utilizing piezoelectric actuators. Due to delamination, the significant changes in the natural frequencies of the lower modes are observed. This causes the reduction on the flutter speed of the delaminated plate model. The aeroelastic control results show that controller makes the delaminated plate model behave like a normal plate. The controller also reduces a significant amount of the root mean square values of the gust response due to gust.

Aeroelastic Control of Smart Composite Plate with Delaminations

Aeroelastic Control of Smart Composite Plate with Delaminations

Comparison of Two Navier-Stokes Methods with Benchmark Active Control Technology Experiments

Two commonly used three-dimensional compressible Navier-Stokes codes are applied to select test cases from an experimental data set on a model known as the Benchmark Active Control Technology (BACT) wing. The BACT test provides data for the validation of aerodynamic, aeroelastic, and active aeroelastic control simulation codes. An overview will be presented of the two Navier-Stokes aeroelastic codes currently being used in an analysis of that data. A collection of results obtained by the two methods will be compared with the BACT experimental data for a wing with a statically deflected spoiler and statically and dynamically deflected aileron. Both methods employ structured computational fluid dynamics flow solvers and continuous surface modeling for the computation of complex moving control surface geometry. Motivation for this work is the development of an integrated computational aeroelasticity and active control simulation capability for the transonic flight regime and validation of that capability using the BACT wing data.

Optimal Wing Planform Design for Aeroelastic Control

An integrated aeroservoelastic design synthesis for flutter suppression and gust load reduction using multiple control surfaces is presented. For this multidisciplinary optimization procedure, structural design variables, control system, and aerodynamic design variables, such as wing planform, ply orientation of the composite layer, and control surface size and location, are considered simultaneously. The analysis for a composite wing with control surfaces is conducted by the finite element method. Unsteady aerodynamic forces calculated by the doublet lattice method are approximated as transfer functions of the Laplace variable by Roger's method. The output feedback control scheme is applied to design the active control system. Using a swept wing model, the performance of the control system is investigated. The geometry of wing planform and control surface size and location are determined by using the genetic algorithm. Design objectives are to minimize the control performance index and the root mean square of the gust responses for various airspeeds. Numerical results showed substantial improvements in performance index value as well as the root-mean-square values of the gust responses compared with the baseline wing model.

Optimal wing planform design for aeroelastic control

Optimal wing planform design for aeroelastic control

Discussion on aeroelastic detail and control in the flutter occurrences of long-span bridges

Considering the trend of longer-span bridges in future, aerostatic and aerodynamic features play a major role in their design. In this paper, the interaction between aeroelastic forces and structural response is discussed along with the effects of structural countermeasures for flutter instability of suspension bridges with spans longer than the Akashi Kaikyo Bridge of main span 1990 m. This analysis is conducted using a newly developed direct FEM flutter analysis method and its assessment system. To gain its aerodynamic stability effectively, the mode-shape control concept is presented. Its effect is discussed quantitatively with examples as an interaction problem between aeroelastic force and structural response of longer-span bridges.

Multivariable Active Lifting Surface Control Using Strain Actuation: Analytical and Experimental Results

This paper describes an analytical and experimental investigation into the use of active lifting surfaces with distributed strain actuators for dynamic aeroelastic control. A detailed analytical aeroelastic model is developed for analysis and control law design using the Rayleigh-Ritz assumed mode method, kernel function unsteady aerodynamics, and modern state-space techniques. The models are used to design multivariable dynamic compensators for applications such as gust alleviation, command following, and flutter suppression. The effectiveness of the control laws is assessed analytically and verified experimentally through closed-loop wind-tunnel testing. The experiments demonstrate that distributed strain actuation can be effectively employed for aeroelastic control, with gust alleviation of 8-dB broadband and an increase in flutter speed of 11 %.

H∞ control for flutter suppression of a laminated plate with self-sensing actuators

Active flutter suppression system of a composite plate wing model is designed using a reduced order model. The analysis for a laminated composite wing with segmented piezoelectric sensor/actuator pairs is conducted by the Ritz solution technique. Unsteady aerodynamic forces calculated by doublet lattice method are approximated as the transfer functions of the Laplace variable by the minimum state method. Among the aerodynamic states obtained from rational function approximation, only one aerodynamic state is included in the plant model for feedback purpose. The neglected aerodynamic states are regarded as modeling error. The control system uses the integrated and collocated piezoelectric self-sensing actuator pairs so as to prohibit the non-minimum phase model and the spillover due to the unmodeled dynamics. Based on the mixed-sensitivityH∞ control method, the control parameters are determined. Using a simple wing model, the performance of the controlled system is shown in the frequency and time domain respectively. The electric current and the power requirement for aeroelastic control are also predicted.

Design Considerations for a Strain Actuated Adaptive Wing for Aeroelastic Control

The dominant issues in the preliminary design of a strain actuated aeroelastic wing are examined. First, the scaling parameter for piezoelectric actuation authority is obtained and used to extrapolate strain actuation variables from an earlier model. Second, the interaction of composite fiber angle and geometric sweep angle is studied, specifically the effect of these parameters on the passive aeroelastic behavior and potential closedloop actuation authority. Finally, a taper ratio trade is completed to understand the effect of varying taper ratio on the passive and active aeroelastic characteristics.