Incremental Nonlinear Control for Aeroelastic Wing Load Alleviation and Flutter Suppression

An incremental differential proportional integral (iDPI) control law using eigenstructure assignment gain design is tested in flight on a subscale platform to validate its suitability for fixed-wing flight control. A kinematic relation for the aerodynamic side-slip angle rate is developed to apply a pseudo full state feedback. In order to perform the gain design and assessment, a plant model is estimated using flight test data from gyro, accelerometer, airspeed and surface deflection measurements during sine-sweep excitations. Transfer function models for the actuators and surface deflections are identified both in-flight and on the ground for several different actuators and control surfaces using hall sensor surface deflection measurements. The analysis reveals a large variation in bandwidth between the different types of servo motors. Flight test results are presented which demonstrates that the plant model estimates based on tests with good frequency excitation, high bandwidth actuators and surface deflection measurements can be used to reasonably predict the closed-loop dynamic behavior of the aircraft. The closed-loop flight test results of the iDPi control law show good performance and lays the groundwork for further development.

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Session 3: Low-speed wind tunnel testing

Raveh,

Sodja,

Mertens

et al. 2023

Preprint

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**Chair: Huub Timmermans, Netherlands Aerospace Centre**Analysis and Testing of the Pazy Benchmark WingThe Pazy wing is an aeroelastic benchmark wing design to explore nonlinear aeroelastic phenomena due to large deformations and gather data for model validation. The Pazy wing was tested in the low-speed wind tunnel at the Technion at static loading conditions that led to deformations in the order of the wing's semispan. The wing underwent limit cycle oscillations at some airspeed and angle of attack combinations. The talk will review the Pazy wing's design, the analyses conducted using the Modal Rotation Method, the test results, and insight into the wing's nonlinear aeroelastic behavior. Active Aeroelastic Wind Tunnel ExperimentsAeroelastic research has become very multidisciplinary involving various disciplines such as flight dynamics, control theory, morphing, novel aircraft, wing and movable concepts, just to mention a few. As a result aeroelastic tests have also grown in scope and complexity to provide validation data for the modelling and design methodologies. This talk will present some of the recent active aeroelastic tests conducted in TU Delft including the test design, hardware and software development and the main outcomes. In the end also the lessons learnt and the outlook will be elaborated.Optical Measurement Techniques for Wind Tunnel Testing of Flexible WingsOptical measurement technology has been gaining more and more traction in aerodynamic wind tunnel testing in recent years. Making these techniques available for the aeroelastic testing of flexible wings has a high potential but comes with certain challenges. This talk will present results from the application of optical measurement techniques to a highly flexible benchmark wing and will discuss the current limitations and potential improvements for the future of aeroelastic wind tunnel testing.Design and testing of subscale models of very flexible wings: lessons learntThe modelling, designing and testing of subscale flexible models present new challenges that did not exist for rigid models. These aspects, which characterise the model's behaviour, often lead to the nonlinear response of the model, which is difficult to predict and to replicate with consistency in the wind tunnel. This presentation will focus on the different elements that characterise the design of such flexible wings, from the design of the test matrix and prediction of the nonlinear behaviour of the model to more minor but essential aspects of the design, such as the impact of panel gaps, instrumentation layout and manufacturing technologies. Examples of different models will be presented to detail various approaches to the problem, stressing the benefits and limitations of the different techniques.

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Incremental Nonlinear Control for Aeroelastic Wing Load Alleviation and Flutter Suppression

Cited by 3 publications

References 19 publications

Flutter suppression of airfoil with control surface using a variable-throttle hydraulic system under extreme fault condition

Flutter suppression of airfoil with control surface using a variable-throttle hydraulic system under extreme fault condition

Practical System Identification and Incremental Control Design for a Subscale Fixed-Wing Aircraft

Session 3: Low-speed wind tunnel testing

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