A morphing aircraft can be defined as an aircraft that changes configuration to maximize its performance at radically different flight conditions. These configuration changes can take place in any part of the aircraft, e.g. fuselage, wing, engine, and tail. Wing morphing is naturally the most important aspect of aircraft morphing as it dictates the aircraft performance in a given flight condition, and has been of interest to the aircraft designers since the beginning of the flight, progressing from the design of control surfaces to the variable-sweep wing. Recent research efforts (mainly under DARPA and NASA sponsorships) however, are focusing on even more dramatic configuration changes such as 200% change in aspect ratio, 50% change in wing area, 5 o change in wing twist, and 20 o change in wing sweep to lay the ground work for truly multi-mission aircraft. Such wing geometry and configuration changes, while extremely challenging, can be conceptually achieved in a variety of ways -folding, hiding, telescoping, expanding, and contracting a wing, coupling and decoupling multiple wing segments, etc. These concepts can be classified under a few 'independent' categories and sub-categories so as to permit a systematic evaluation of benefits and challenges. This paper presents: 1) a review of prior work leading to current R&D efforts, 2) classification of morphing designs, and 3) a summary of technical challenges encountered in designing a morphing aircraft.
One of the limitations of a piezoelectric actuator is the amount of force it can exert. Hence, it is important to optimize the locations and sizes of the actuators so that the required control effort is minimal. Similarly, to obtain good signal-to-noise ratio, sensors should be chosen to provide maximum output for the vibration in the modes of interests. These problems become more critical as the number of actuators and sensors increases, and the mode shapes become more complicated. This is true for the case of an inflated torus. In this study, we try to find optimum places and sizes of actuators and sensors attached to an inflated toroidal shell using a genetic algorithm. Using the expressions for the generalized forces and sensor voltages, modal forces and modal sensing constants are determined. To obtain a cumulative performance measure for all the controlled and observed modes, controllability and observability indices are used. Using these performance indices, optimal locations and sizes of the actuators and sensors are determined so that the actuators and sensors provide good control and sensing authorities in the considered modes. Finally, vibration suppression of the inflated torus using these actuators and sensors has been demonstrated using an optimal control technique.
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