1,721,019 research outputs found
Dual Loop PI^m PI^n Control for an Aileron Positioning
Full text linkAircraft control surfaces are subjected to uncertain design parameters and time–varying external disturbances related to aerodynamic loads. This paper presents a control formulation for their positioning based on a velocity/position dual loop, embedding an arbitrary order of integral actions determined through a simple linear design. The adoption of an appropriate high order integration aims to compensate for external disturbances, modeling uncertainties and the impact of some nonlinearities. Relevant design and implementation issues were also described, including windup mitigation and the use of an observer to compensate for out–of–band disturbances. After a numerical model validation comprising a Monte Carlo assessment of the combined uncertainties, the controller was verified experimentally. The test bench was made up of the aileron of a wind tunnel model, driven by an electric motor through a mildly tensioned timing belt transmission. The results of a significant test set are provided to demonstrate the effectiveness of such a controller against noteworthy design uncertainties, such as sliding friction, sensor failure, free play due to inadequate belt tension, and approximate design parameters
Using Multilevel Optimization for the Design of Morphing Wings Based on Compliant Mechanisms
No full textMultiobjective Optimization for the Aero-Structural Design of Adaptive Compliant Wing Devices
Full text linkThe design of morphing structures must combine conflicting structural requirements and multiple load conditions that are related to the aerodynamic shapes aimed at optimizing aircraft performance. This article proposes a multilevel approach for the design of adaptive compliant wing devices. A set of aerodynamic shapes, and associated their loads, is defined by a shape optimization, coupled with a three-dimensional parametric technique, that can identify only feasible shape changes due to the morphing. A topology and sizing multiobjective optimization drives the Pareto-optimal structural design of the compliant structure, which is able to deform itself to match, once actuated, all of the previously defined aerodynamic shapes. Next two design levels produce a more detailed solution which is extended until the definition of the complete device. A 90 pax, twin prop green regional aircraft is used as an innovative aircraft demonstration platform for the design of the morphing droop nose to be installed on the wing. The results show the structural capabilities of this device in terms of the external shape quality and the strain requirements. This work enables the validation of the design method and prove the functionality of compliant structures when accounting for the aeroelastic effects due to the interaction with the wing-box
Study on the Actuation Aspects for a Morphing Aileron Using an Energy–Based Design Approach
Full text linkEvaluating the impact of morphing devices in terms of actuation energy is a promising approach to quantify, from the earliest stages of wing design, the convenience of active camber morphing compared to the use of conventional control surfaces. A morphing wing device consists of an adaptive structure coupled with an actuation system. The starting point for the design of the adaptive structure is a three-dimensional parametric-geometry-representation technique working on the definition of the external morphing shape. The morphing shape is defined to be feasible from the structural point of view and able to meet the aerodynamic design requirements. The new method presented here enables the computation of the actuation energy as a combination of strain energy and external aerodynamic work. The former is the energy required to deform the skin and can be computed in an analytical way, based on the same quantities used by the parameterization technique. The latter is used to compute the energy needed to counteract the external aerodynamic loads during the deformation. This method is applied to the design optimization of a morphing aileron which is installed on a 24 m span wing, starts at 65% of both the chord and the semi-span and extends for one third of the span. A parametric study shows the superiority of the morphing aileron, compared with an equivalent hinged aileron, in terms of energy saving, weight penalty reduction and ease of on-board installation. The morphing aileron is more compact and requires a lower actuation energy combined with a lower deflection, while providing the same roll moment
Experimental and performance validation of a full-scale morphing droop nose design based on composite compliant structures
Full text linkActive camber morphing technology can be used to improve aircraft performance in takeoff and landing flight conditions, while preserving a smooth wing shape. This study begins with the design of a morphing droop nose to be installed on a regional aircraft, and focuses on the manufacturing and testing of a full-scale and fully representative experimental prototype. All work is driven by the morphing shape change, which was optimized to provide the required aerodynamic performance. The adoption of a composite structure that combines a flexible skin with a compliant structure makes this device capable of achieving such a shape change, and sufficiently insensitive to external load variations. These capabilities are successfully demonstrated through experimental testing. A validation phase was conducted based on strain gauge measurements, and a motion capture system was used to identify three-dimensional shape changes due to the morphing. Finally, a validated numerical model is used to assess the aerodynamic performance of the experimental prototype
Aeroelastic Analysis of a Regional Aircraft with Active Camber Morphing Device
No full textStarting from the previous activities developed by Politenico di Milano in the framework of FP7-NOVEMOR, this paper reports the aeroelastic assessment carried out on the so-called Reference Aircraft to validate the proposed morphing concepts. Indeed, in the case of morphing devices based on compliant structures like ones here proposed, the aeroelastic assessment is fundamental to verify the reliability of the proposed morphing solutions. After a reminder on the tools developed aiming at the design of variable camber morphing wings, the paper describes the main aeroelastic results obtained from the application of the morphing concepts based on compliant structures to a typical regional aircraft
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