1,308 research outputs found
Multi-objective design of robust flight control systems
The aim of this work is to demonstrate the capabilities of evolutionary methods in the design of robust controllers for unstable fighter aircraft in the framework of H1 control theory. A multi–objective evolutionary algorithm is used to find the controller gains that minimize a weighted combination of the infinite–norm of the sensitivity function (for disturbance attenuation requirements) and complementary sensitivity function (for robust stability requirements). After considering a single operating point for a level flight trim condition of a F-16 fighter aircraft model, two different approaches will then be considered to extend the domain of validity of the control law: 1) the controller is designed for different operating points and gain scheduling is adopted; 2) a single control law is designed for all the considered operating points by multiobjective minimisation. The two approaches will be analysed and compared in terms of efficacy and required human and computational resources
Multi-objective design of robust flight control systems
A multi–objective evolutionary algorithm is used in the framework of H1 control theory
to find the controller gains that minimize a weighted combination of the infinite–norm
of the sensitivity function (for disturbance attenuation requirements) and complementary
sensitivity function (for robust stability requirements). After considering a single operating
point for a level flight trim condition of a F-16 fighter aircraft model, two different
approaches will then be considered to extend the domain of validity of the control law: 1)
the controller is designed for different operating points and gain scheduling is adopted; 2)
a single control law is designed for all the considered operating points by multiobjective
minimisation. The two approaches are analyzed and compared in terms of effectiveness of
the design method and resulting closed loop performance of the system
Evolutionary design of a full-envelope full-authority flight control system for an unstable high-performance aircraft
The use of an evolutionary algorithm in the framework of H1 control theory is being considered as a means for synthesizing controller gains that minimize a weighted combination of the infinite norm of the sensitivity function (for disturbance attenuation requirements) and complementary sensitivity function (for robust stability requirements) at the same time. The case study deals with a complete full-authority longitudinal control system for an unstable high-performance jet aircraft featuring (i) a stability and control augmentation system and (ii) autopilot functions (speed and altitude hold). Constraints on closed-loop response are enforced, that representing typical requirements on airplane handling qualities, that makes the control law synthesis process more demanding. Gain scheduling is required, in order to obtain satisfactory performance over the whole flight envelope, so that the synthesis is performed at different reference trim conditions, for several values of the dynamic pressure, used as the scheduling parameter. Nonetheless, the dynamic behaviour of the aircraft may exhibit significant variations when flying at different altitudes, even for the same value of the dynamic pressure, so that a trade-off is required between different feasible controllers synthesized at different altitudes for a given equivalent airspeed. A multiobjective search is thus considered for the determination of the best suited solution to be introduced in the scheduling of the control law. The obtained results are then tested on a longitudinal non-linear model of the aircraft
Design and Development of the Engine Unit for a Twin-Rotor Unmanned Aerial Vehicle
Advanced computer-aided technologies played a crucial role in the design of an unconventional Uninhabited Aerial Vehicle (UAV), developed at the Turin Technical University and the University of Rome “La Sapienza”. The engine unit of the vehicle is made of a complex system of three two stroke piston engines coupled with two counter-rotating three-bladed rotors, controlled by rotary PWM servos. The focus of the present paper lies on the enabling technologies exploited in the framework of activities aimed at designing a suitable and reliable engine system, capable of performing the complex tasks required for operating the proposed rotorcraft. The synergic use of advanced computational tools for estimating the aerodynamic performance of the vehicle, solid modeling for mechanical components design, and rapid prototyping techniques for control system logic synthesis and implementation will be presented.
Interactions in Mobile Sound and Music Computing
none4siopenGeronazzo M.; Avanzini F.; Fontana F.; Serafin S.Geronazzo, M.; Avanzini, F.; Fontana, F.; Serafin, S
Fatigue behavior and cyclic damage of peek short fiber reinforced composites
Fatigue strength and failure mechanisms of short fiber reinforced (SFR) PEEK have been investigated in
the past by several research groups. However some relevant aspects of the fatigue behavior of these
materials, like cyclic creep and fatigue damage accumulation and modeling, have not been studied yet,
in particular in presence of both fillers and short fibers as reinforcement. In the present research these
aspects were considered by carrying out uni-axial fatigue tests in load control (cycle ratio R = 0) on neat
PEEK and PEEK based composites reinforced either with short carbon fibers only or with addition of fillers
(graphite and PTFE). For each material stress-life curves were obtained and compared. Fatigue fracture
surfaces were analyzed to identify failure mechanisms in presence of different reinforcement types.
The evolution of cyclic creep strain was also monitored as a function of the number of cycles, thus allowing
investigation on the correlation between cyclic creep parameters and fatigue life. The evolution of
cyclic damage with loading cycles was then compared by defining a damage parameter related to the
specimen stiffness reduction observed during the tests. Progressive cyclic damage evolution of short fiber
reinforced PEEK composites presented significantly different patterns depending on applied stress level
and on the presence of different reinforcement typologies. In order to reproduce the different fatigue
damage kinetics and stages of progressive damage accumulation observed experimentally, a cyclic
damage model was finally developed and implemented into a finite element code by which a satisfactory
agreement between numerical prediction and experimental data at different stress levels for each examined
material
Spectral and temporal cues for perception of material and action categories in impacted sound sources
Stima di feature spettrali di HRTF mediante modelli antropometrici non lineari per la resa di audio 3D
La relazione tra i parametri antropometrici di un soggetto umano e le feature tipiche delle Head-Related Transfer Function (HRTF), in particolare quelle collegabili al padiglione auricolare (o pinna), non \ue8 compresa appieno. In questo articolo applichiamo tecniche di elaborazione del segnale per estrarre le frequenze del primo notch dovuto alla pinna (conosciuto come N1) nella porzione frontale del piano mediano e costruiamo un modello basato su una rete neurale artificiale che relazioni le frequenze stesse a 13 diversi parametri antropometrici della pinna, alcuni dei quali dipendono dall'elevazione della sorgente sonora. I risultati mostrano una corrispondenza incoraggiante tra l'antropometria e le feature spettrali, la quale conferma la possibilit\ue0 di predire la frequenza centrale del notch a partire da una semplice fotografia dell'orecchio
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