Andrei Vladimir Popov

Closed-Loop Control Validation of a Morphing Wing Using Wind Tunnel Tests

In this paper a rectangular finite aspect ratio wing, having a wing trailing edge airfoil reference airfoil cross section, was considered. The wing upper surface was made of a flexible composite material and instrumented with Kulite pressure sensors and two smart memory alloys actuators. Unsteady pressure signals were recorded and visualized in real time while the morphing wing was being deformed to reproduce various airfoil shapes by controlling the two actuators displacements. The controlling procedure was performed using two methods which are described in the paper. Several wind-tunnel test runs were performed for various angles of attack and Reynolds numbers in the 6 × 9 foot wind tunnel at the Institute for Aerospace Research at the National Research Council Canada. The Mach number was varied from 0.2 to 0.3, the Reynolds numbers varied between 2.29 and 3.36 x 10 6 , and the angle-of-attack range was within -1 to 2 degrees. Wind-tunnel measurements are presented for airflow boundary layer transition detection using high sampling rate pressure sensors.

Modeling and Testing of a Morphing Wing in Open-Loop Architecture

This paper presents the modeling and experimental testing of the aerodynamic performance of a morphing wing in open-loop architecture. We show the method used to acquire the pressure data from the external surface of the flexible wing skin, using incorporated Kulite pressure sensors and the instrumentation of the morphing controller. The acquired pressure data are analyzed through fast Fourier transforms to detect the magnitude of the noise in the surface airflow. Subsequently, the data are filtered by means of high-pass filters and processed by calculating the root mean square of the signal to obtain a plot diagram of the noise in the airflow. This signal processing is necessary to remove the inherent noise electronically induced from the Tollmien-Schlichting waves, which are responsible for triggering the transition from laminar to turbulent flow. The flexible skin is required to morph the shape of the airfoil through two actuation points to achieve an optimized airfoil shape based on the theoretical flow conditions similar to those tested in the wind tunnel. Two shape memory alloy actuators with a nonlinear behavior drive the displacement of the two control points of the flexible skin toward the optimized airfoil shape. Each of the shape memory actuators is activated by a power supply unit and controlled using the Simulink/MATLAB® software through a self-tuning fuzzy controller. The methodology and the results obtained during the wind-tunnel test proved that the concept and validity of the system in real time are discussed in this paper. Real-time acquisition and signal processing of pressure data are needed for further development of the closed-loop controller to obtain a fully automatic morphing wing system.

Transition Point Detection from the Surface Pressure Distribution for Controller Design

airfoil types: NACA 4415 and WTEA-TE1, as well as for 17 modified WTEA-TE1 airfoil shapes, obtained by displacing the flexible wing upper surface using a single point control mechanism. The second derivative of the pressure distribution is calculated, using two interpolation schemes: piecewise cubic Hermite interpolating polynomial and Spline, from which it is determined that transition may be identified as the location of maximum curvature in the pressure distribution. The results of this method are validated using the well-known XFoil code, which is used to theoretically calculate the transition point position. Advantages of this new method in the real-time control of the location of the transition point are presented.

A hybrid fuzzy logic proportional- integral-derivative and conventional on-off controller for morphing wing actuation using shape memory alloy Part 1: Morphing system mechanisms and controller architecture design

The present paper describes the design of a hybrid actuation control concept, a fuzzy logic proportional-integral-derivative plus a conventional on-off controller, for a new morphing mechanism using smart materials as actuators, which were made from shape memory alloys (SMA). The research work described here was developed for the open loop phase of a morphing wing system, whose primary goal was to reduce the wing drag by delaying the transition (from laminar to fully turbulent flows) position toward the wing trailing edge. The designed controller drives the actuation system equipped with SMA actuators to modify the flexible upper wing skin surface. The designed controller was also included, as an internal loop, in the closed loop architecture of the morphing wing system, based on the pressure information received from the flexible skin mounted pressure sensors and on the estimation of the transition location. The controller’s purposes were established following a comprehensive presentation of the morphing wing system architecture and requirements. The strong nonlinearities of the SMA actuators’ characteristics and the system requirements led to the choice of a hybrid controller

Variations in Optical Sensor Pressure Measurements due to Temperature in Wind Tunnel Testing

In this paper, wind-tunnel measurements are presented for the airflow fluctuation detection using pressure optical sensors. Twenty-one wind-tunnel test runs for various Mach numbers, angles of attack, and Reynolds numbers were performed in the 6 x 9 ft 2 wind tunnel at the Institute for Aerospace Research at the National Research Council Canada. A rectangular finite aspect ratio half-wing, having a NACA 4415 cross section, was considered with its upper surface instrumented with pressure taps, pressure optical sensors, and one Kulite transducer. The Mach number was varied from 0.1 to 0.3 and the angle of attack range was within -3 to 3 deg. Unsteady pressure signals were recorded and a thorough comparison, in terms of unsteady and mean pressure coefficients, was performed between the measurements from the three sets of pressure transducers. Temperature corrections were considered in the pressure measurements by optical sensors. Comparisons were also performed against theoretical predictions using the XFoil computational fluid dynamics code, and mean errors smaller than 10% were noticed between the measured and the predicted data.

New Aeroelastic Studies for a Morphing Wing

For this study, the upper surface of a rectangular finite aspect ratio wing, with a laminar airfoil cross-section, was made of a carbon-Kevlar composite material flexible skin. This flexible skin was morphed by use of Shape Memory Alloy actuators for 35 test cases characterized by combinations of Mach numbers, Reynolds numbers and angles of attack. The Mach numbers varied from 0.2 to 0.3 and the angles of attack ranged between -1° and 2°. The optimized airfoils were determined by use of the CFD XFoil code. The purpose of this aeroelastic study was to determine the flutter conditions to be avoided during wind tunnel tests. These studies show that aeroelastic instabilities for the morphing configurations considered appeared at Mach number 0.55, which was higher than the wind tunnel Mach number limit speed of 0.3. The wind tunnel tests could thus be performed safely in the 6’×9’ wind tunnel at the Institute for Aerospace Research at the National Research Council Canada (IAR/NRC), where the new aeroelastic studies, applied on morphing wings, were validated.

An Intelligent Controller based Fuzzy Logic Techniques for a Morphing Wing Actuation System using Shape Memory Alloy

The paper presents a way to control the actuation lines of a morphing wing using an intelligent controller based on fuzzy logic techniques. The strong non-linear character of the used actuators, made from some smart materials, and the numerical simulations achieved in the design phase provides for the controller a fuzzy logic Proportional-Integral-Derivative architecture seconded by a conventional On-Off controller. The input-output mapping of the fuzzy model is designed, taking account of the system’s error and its change in error. The shapes chosen for the inputs’ membership functions are triangular, while the product fuzzy inference and the center average defuzzifier are applied (Sugeno). After the controller tuning, three validation steps are done: a numerical one, followed by other two experimentally. For the experimental validation, bench tests and wind tunnel tests are performed. The bench test experimental validation is made in laboratory conditions, in the absence of aerodynamic forces, for different actuation commands. In the wind tunnel tests, are also experimentally validated the optimized airfoils with the theoretically-determined airfoils obtained earlier. Both the transition point real time position detection and visualization are realized in wind tunnel tests.

Control of actuation system based smart material actuators in a morphing wing experimental model

The modeling and the experimental testing of the aerodynamic performance of a morphing wing, starting from the design concept phase all the way to the bench and wind tunnel tests phases, are presented here. Several wind tunnel test runs for various Mach numbers and angles of attack were performed in the 6 × 9 ft 2 wind tunnel at the Institute for Aerospace Research at the National Research Council Canada. A rectangular finite aspect ratio wing, having a morphing airfoil cross-section due to a flexible skin installed on the upper surface of the wing, was instrumented with Kulite transducers. The flexible skin needed to morph its shape through two actuation points in order to obtain an optimized airfoil shape for several flow conditions in the wind tunnel: the Mach number varied from 0.2 to 0.3 and the angle of attack between -1 o and 2 o . The two shape memory alloy actuators, having a non-linear behavior, drove the displacement of the two control points of the flexible skin towards the optimized airfoil shape. Unsteady pressure signals were recorded and analyzed and a thorough comparison, in terms of mean pressure coefficients and their standard deviations, was performed against theoretical predictions, using the XFoil computational fluid dynamics code. The acquired pressure data was analyzed through custom-made software created with Matlab/Simulink in order to detect the noise magnitude in the surface airflow and to localize the transition point position on the wing upper surface. This signal processing was necessary in order to detect the Tollmien-Schlichting waves responsible for triggering the transition from laminar to turbulent flow.

Self-adaptive morphing wing model, smart actuated and controlled by using a multiloop controller based on a laminar flow real time optimizer

The modeling, the design, the numerical simulation and the experimental testing of the control system for a self-adaptive morphing wing model are here exposed. The study was performed during a multidisciplinary research project, involving industrial partners, a research institute and three academic entities. The developed control system is a multiloop one, being designed, simulated and tested in two major steps, correlated with the validation phases of the aerodynamic gains provided by the morphed wing model in terms of the laminar flow improvement over its upper surface. The two validation phases were suggestively called open loop, respectively closed loop; in the first phase the aerodynamic validation was made just by comparing the experimentally obtained results with the numerical optimization obtained ones, while in the second phase the morphing wing model was left free, to adapt itself based on the information related to the transition point position provided by some pressure sensors installed on its upper surface. The used wing model was a rectangular one, equipped with a composite made flexible upper surface, morphed along of two lines by using some shape memory alloy actuators. For the open loop phase a database with some optimized airfoils was generated and a smart controller based fuzzy logic was designed to control the position of the actuators in real time so that the desired optimized skin corresponding to the desired displacements to be obtained and maintained during the flight tests. The closed loop architecture was realized by using a real-time optimization algorithm, which included the actuators controller as inner loop. The algorithm was developed in order to generate real-time optimized airfoils starting from the information received from the pressure sensors and targeting the morphing wing main goal: the improvement of the laminar flow over the wing upper surface.

Design and Experimental Validation of a Combined PI and Bi-Positional Laws Controller for Delaying the Transition from Laminar Flow to Turbulent Flow over a Morphing Wing

This chapter presents the design and the validation of the actuators control system for a morphing wing application. Some smart materials, like Shape Memory Alloy (SMA), are used as actuators to modify the upper surface of the wing made of a flexible skin. The finally adopted control law is a combination of a bi-positional law and a PI law. The controller is validated in two experimental ways: bench test and wind tunnel test. All optimized airfoil cases, used in the design phase, are converted into actuators vertical displacements which are used as inputs reference for the controller. In the wind tunnel tests a comparative study is realized around of the transition point position for the reference airfoil and for each optimized airfoil.