A numerical study on active control for tiltrotor whirl flutter stability augmentation

The use of active control to augment whirl flutter stability of tiltrotor aircraft is studied by means of a multibody simulation. The numerical model is based on a 1/5 scale semi-span aeroelastic wind tunnel model of a generic tiltrotor concept and possesses a gimballed, stiff-in-plane rotor that is windmilling. A single-input single-output controller and two types of multi-input multi-output algorithms, Linear Quadratic Gaussian Control and Generalized Predictive Control, are studied. They are using measured wing deflections in order to calculate appropriate swashplate input. Results on the closed-loop behavior of three wing and two gimbal natural modes are given. Robustness analyses with respect to major parameters like wing natural frequencies or structural damping are also briefly discussed. The rotor shear force is shown in the uncontrolled condition and in presence of a controller in order to illustrate the whirl flutter mechanism. The single-input single-output controller yielded substantial gain in stability and turned out to be most suitable for industrial application, whereas the Linear Quadratic Gaussian Regulator yielded even higher damping and still had good robustness characteristics

Procédé et aéronef muni d'un dispositif pour la réduction de vibrations

La présente invention concerne un aéronef (1) muni d'une boîte de transmission de puissance (3) fixée à une structure porteuse (2) par au moins trois barres de suspension (5). Un absorbeur de vibrations (10) actif est fixé autour de chaque barre de suspension (5), chaque absorbeur de vibrations (10) étant pourvu d'une première masse (11) reliée à la barre de suspension (5) associée par un premier moyen élastique (21) ainsi que d'une deuxième masse (12) reliée à la première masse (11) par un deuxième moyen élastique (22, ledit absorbeur de vibrations (10) ayant un générateur d'efforts (15) interposé entre la première masse (11) et la deuxième masse (12) introduisant un effort de commande sur ordre d'une unité de commande (16) en fonction d'informations provenant d'au moins un premier capteur de mesure (17) de paramètres de surveillance de la barre de suspension associée

Lightweight design: mass in transit

This paper is part of an effort to reduce a vehicle’s CO2 emissions through lightweight design. The originality of the approach consists in harnessing the optimal vehicle architecture with regard to CO2 emissions. Reducing a vehicle’s weight provides an opportunity to reassess performance features like shock, noise, vibrations and road holding, thereby generating additional savings through a virtuous cycle of weight reduction. The paper sheds light on some methodological aspects used by PSA Peugeot-Citroen for designing lightweight vehicles

New Science Gateways for Advanced Computing Simulations and Visualization Using Vine Toolkit in PL-Grid

A Science Gateway is a connection between scientists and their computational tools in the form of web portal. It creates a space for communities, collaboration and data sharing and visualization in a comprehensive and efficient manner. The main purpose of such a solution is to allow users to access the computational resources, process and analyze their data and get the results in a uniform and user friendly way. In this paper we propose a complex solution based on the Rich Internet Application (RIA) approach consisting of a web portal powered by Vine Toolkit with Adobe Flex/BlazeDs technologies. There are two Science Gateways described in detail one for engineers to manage computationally intensive workflows used in advanced airplane construction simulations, and one for nanotechnology scientists to manage experiments in nano-science field calculated with Density Functional Theory (DFT). In both cases the results show how modern web solution can help scientists in their work. &nbsp

Lightweight design: mass in transit

This paper is part of an effort to reduce a vehicle’s CO2 emissions through lightweight design. The originality of the approach consists in harnessing the optimal vehicle architecture with regard to CO2 emissions. Reducing a vehicle’s weight provides an opportunity to reassess performance features like shock, noise, vibrations and road holding, thereby generating additional savings through a virtuous cycle of weight reduction. The paper sheds light on some methodological aspects used by PSA Peugeot-Citroen for designing lightweight vehicles

Mechanical instability

This book presents a study of the stability of mechanical systems, i.e. their free response when they are removed from their position of equilibrium after a temporary disturbance. After reviewing the main analytical methods of the dynamical stability of systems, it highlights the fundamental difference in nature between the phenomena of forced resonance vibration of mechanical systems subjected to an imposed excitation and instabilities that characterize their free response. It specifically develops instabilities arising from the rotor-structure coupling, instability of control systems, the self-sustained instabilities associated with the presence of internal damping and instabilities related to the fluid-structure coupling for fixed and rotating structures. For an original approach following the analysis of instability phenomena, the book provides examples of solutions obtained by passive or active methods

A multibody study on single- and multi-variable control algorithms for tiltrotor whirl flutter stability augmentation

The results of a numerical study on prop-rotor whirl flutter stability augmentation are presented in this paper. Based on a 1/5 scale semi-span aeroelastic wind tunnel model of a generic tiltrotor concept, a numerical simulation is set up using a general purpose multibody simulation tool. The model possesses a gimballed stiff-in-plane rotor with a constant velocity drive system. Three different control algorithms are presented and evaluated. Firstly, there is a single-input single-output controller using conditioned wing deflection feedback on longitudinal cyclic swashplate input. Secondly, two types of multi-input multi-output control that are based on time domain identification of the model are presented: A Linear Quadratic Regulator with a Kalman-Bucy state estimator and a Generalized Predictive Control algorithm. Both of them use measured wing deflections in order to calculate appropriate swashplate input. The control studies are done with a windmilling rotor. Detailed results of the closed-loop behavior of three wing and two gimbal natural modes are presented up to the closed-loop stability boundaries. Robustness analyses of the algorithms with respect to wing natural frequencies, structural damping, flight speed, rotation speed, flight altitude and signal noise are an integral part of the article. The rotor shear force is shown in the open-loop condition and in presence of a controller in order to illustrate the whirl flutter mechanism and the action of the controller. The three control methods yielded substantial gain in stability and critical speed and they showed good robustness margins