343 research outputs found
Pion mass dependence of the nucleon mass in the chiral quark soliton model
The dependence of the nucleon mass on the mass of the pion is studied in the
framework of the chiral quark-soliton model. A remarkable agreement is observed
with lattice data from recent full dynamical simulations. The possibility and
limitations to use the model results as a guideline for the chiral
extrapolation of lattice data are discussed.Comment: 14 pages, 12 figures, 4 tables. v2: References added, new figure
included, discussion improved, typos fixed, matches published versio
LPV model-based robust diagnosis of flight actuator faults
A linear parameter-varying (LPV) model-based synthesis, tuning and assessment methodology is developed and applied for the design of a robust fault detection and diagnosis (FDD) system for several types of flight actuator faults such as jamming, runaway, oscillatory failure, or loss of efficiency. The robust fault detection is achieved by using a synthesis approach based on an accurate approximation of the nonlinear actuator-control surface dynamics via an LPV model and an optimal tuning of the free parameters of the FDD system using multi-objective optimization techniques. Real-time signal processing is employed for identification of different fault types. The assessment of the FDD system robustness has been performed using both standard Monte Carlo methods as well as advanced worst-case search based optimization-driven robustness analysis. A supplementary industrial validation performed on the AIRBUS actuator test bench for the monitoring of jamming, confirmed the satisfactory performance of the FDD system in a true industrial setting
A Versatile Simulation Environment of FTC Architectures for Large Transport Aircraft
We present a simulation environment with 3-D stereo visualization facilities destined for an easy setup and versatile assessment of fault detection and diagnosis based fault tolerant control systems. This environment has been primarily developed as a technology demonstrator of advanced reconfigurable flight control systems and is based on a realistic six degree of freedom flexible aircraft model. The aircraft control system architecture includes a flexible fault detection and diagnosis system and a reconfigurable nonlinear dynamic inversion based controller, able to handle different fault situations
Combining sensor monitoring and fault tolerant control to maintain flight control system functionalities
To maintain nominal flight control system functionalities during fault scenarios, enhancements of the state-of-practise angle of attack and airspeed sensor fault accommodation strategies are presented. The strategy combines a fault detection and diagnosis (FDD) system
with a robust fault tolerant control law. The FDD system allows to maintain the nominal flight control law as long as at least one angle of attack and airspeed sensor are available. The FDD system is designed using advanced nullspace computation, optimization, and signal processing
techniques. For the scenario of a total airspeed measurement loss, an airspeed independent longitudinal backup control law is designed using global optimization techniques. Using this law avoids the state-of-practise switch to a direct law in which the pilot must control the Elevator positions directly. The results from an extensive industrial validation and veri�cation campaign are reported
The pion mass dependence of the nucleon form-factors of the energy momentum tensor in the chiral quark-soliton model
The nucleon form factors of the energy-momentum tensor are studied in the
large-Nc limit in the framework of the chiral quark-soliton model for model
parameters that simulate physical situations in which pions are heavy. This
allows for a direct comparison to lattice QCD results.Comment: 17 pages, 12 figure
The target asymmetry in hard vector-meson electroproduction and parton angular momenta
The target asymmetry for electroproduction of vector mesons is investigated
within the handbag approach. While the generalized parton distribution (GPD) H
is taken from a previous analysis of the elctroproduction cross section, we
here construct the GPD E from double distributions and constrain it by the
Pauli form factors of the nucleon, positivity bounds and sum rules. Predictions
for the target asymmetry are given for various vector mesons and discussed how
experimental data on the asymmetry will further constrain E and what we may
learn about the angular momenta the partons carry.Comment: 24 pages, 11 figures, late
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An Investigation of Cultural Influence on Perceptions of Abusive Supervision
The purpose of this study is to investigate the influence of culture on abusive supervision perceptions in the hospitality industry. To set the stage for this investigation, the literature review concentrates on abusive supervision (Tepper, 2000) and culture using Hofstede\u27s constructs (Hofsetde, 2001). The proposed methodology for this study will be discussed. The assumption is that culture will influence perceptions of abusive supervision
The nucleon form-factors of the energy momentum tensor in the Skyrme model
The nucleon form factors of the energy-momentum tensor are studied in the
large-Nc limit in the framework of the Skyrme model.Comment: 19 pages, 11 Figures, 2 Tables; correction in footnote 2, extension
in App.D, some reformulations, references added, results and conclusions
unchange
Synthèse et validation d'une lois de contrôle de charge a deux degrés de liberté
International audienceThe design and assessment of a two degree of freedom gust load allevi-ation control system for a business jet aircraft is presented in this paper. The two degrees of freedom are a disturbance estimator to compute the incoming gusts as well as a feedback control law to mitigate the estimated disturbance to reduce the aircraft loads. To facilitate the estimator design, high order, infinite models of the structural and aerodynamic aircraft dynamics are approximated by low order models using advanced model reduction techniques. For the robust disturbance estimator design an innovative approach relying on nullspace based techniques together with non-linear optimizations is proposed. Time delays, originating from the aerodynamics modeling, the discrete control loop, and the sensor and actuator dynamics, play a key role in the stability and performance assessment of a gust load alleviation controller. Thus, a novel analytical analysis method is presented to explicitly evaluate the influence of these time delays on the closed loop. Finally, the developed tool-chain is applied to a fly-by-wire business jet aircraft. The resulting two degree of freedom gust load alleviation system is verified in a simulation campaign using a closed loop, non-linear simulator of the aircraft
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