Browsing by Author "Morris, Russell A."

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    Aeroelastic modeling and flutter control in aircraft with low aspect ratio composite wings
    Morris, Russell A. (Virginia Tech, 1996)
    A comprehensive study including modeling and control of aeroelastic instabilities in free flying aircraft with flexible wings has been completed. The structural model of the wing consists of a trapezoidal composite plate rigidly attached to a fuselage with rigid-body degrees of freedom. Both quasi-steady and quasi-static aerodynamic strip theories were used to analyze several different flutter mechanisms for a variety of low aspect ratio wing configurations. The most critical flutter mechanism was found to be body-freedom flutter, a coupling of aircraft pitching and wing bending motions, for wings in a forward-sweep configuration. In addition, a modal approximation to the flutter eigenvalue problem was used to substantially reduce computation cost, making the resulting model very attractive for use in larger multiobjective design packages. Composite ply angle tailoring was investigated as a passive method of increasing the body-freedom flutter airspeed of an aircraft model. In addition, wing mounted piezoelectric sensor and induced-strain actuator patches were used in conjunction with active feedback control laws to increase the airspeed at which body-freedom flutter occurs. Two control laws were tested, coupled and independent modal position feedback, to delay frequency coalescence and thus increase the flutter airspeed.
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    Optimal state estimation for the optimal control of far-field acoustic radiation pressure from submerged plates
    Morris, Russell A. (Virginia Tech, 1992)
    Sound pressure radiating from vibrating structures submerged in fluid, as in the case of a vibrating panel in a submarine hull, is usually undesirable. An optimal control methodology for the suppression of far-field acoustic radiation pressure from submerged structures has been developed by Meirovitch (ref. 1). The linear modal state feedback control law developed implies that the full state (displacements and velocities) is available, perhaps through measurements. However, in practice, it is not always feasible to measure the full modal state vector for feedback. To permit practical implementation of the feedback control law, an optimal stochastic state estimator, or Kalman-Bucy filter, has been developed here for incorporation into the control system design. The development has been specialized to a uniform simply supported rectangular plate.