METHODS AND SYSTEMS FOR ESTIMATION OF SHAPE-CHANGES APPLICABLE TO NAVIGATION AND CONTROL OF FLEXIBLE AEROSPACE VEHICLES
Baraniello, Vincenzo Rosario (2011) METHODS AND SYSTEMS FOR ESTIMATION OF SHAPE-CHANGES APPLICABLE TO NAVIGATION AND CONTROL OF FLEXIBLE AEROSPACE VEHICLES. [Tesi di dottorato] (Inedito)
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Weight reduction has always represented an important factor in the design of aerospace structures and actually this tendency is increasing. New materials, as composite materials, and new structural solutions have been proposed in recent years in order to reduce weights and improve the performances. Lightweight structures and large wingspans induce an increment of deformations because of a detriment in the structural stiffness. In this thesis the impact of structural flexibility on guidance, navigation and control disciplines will be discussed and some innovative solutions will be proposed in order to overcome limits of traditional rigid-body dynamic models. The main effect of structural flexibility is an aircraft shape change in presence of maneuvers or gust. Concerning shape changes estimation, in this work two innovative solutions are presented: o extension of integrated navigation algorithms to flexible aircraft taking into account the flexible motions (shape changes); o an algorithm for estimation of the shape changes alone, to be used, for example, in a load alleviation system. A specific sensor setup has been associated to each one of these two proposals. In the case of integrated navigation, GPS and inertial sensors are used to estimate the rigid and flexible states (the word “rigid state” denotes at least position, speed and attitude, the word “flexible state” denotes some variables used to describe elastic motions), while for the determination of the shape changes alone, inertial sensors are associated with a video-based system. This last point also represents an innovative solution. The need for estimation of shape changes, independently by the rigid state, is justified by the consideration that for some classes of aircrafts, structural flexibility has not a big effect on navigation (estimation of navigation parameters is not strongly affected by the flexible state, essentially because of navigation sensors accuracy which is lower than the magnitude of elastic motions). The knowledge of shape changes is however required in load or gust alleviation techniques or for other applications, as for example the correction of the output provided by particular sensors installed onboard the aircraft. In this work a simulation model of an aircraft, including elastic dynamic, will be presented, discussing the hypotheses on which it is based. This simulation model will be used to verify the performances of the proposed systems, but, above all, to analyze the main factors influencing the algorithms for shape changes estimation within gust or load control systems.
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