Hypersonic vehicles can be very difficult aircraft to control due to system uncertainties and a wide range of potential operating conditions. Adaptive control techniques have been shown to be useful in circumstances with this type of parametric uncertainty, and so are often utilized for the control of hypersonic aircraft. In addition to these difficulties, another challenge present for all aircraft, but especially vehicles flying at hypersonic speeds, is the ability to accurately measure angle-of-attack. Often this challenge is neglected in the literature and it is assumed that angle-of-attack can be measured perfectly. For the case of hypersonic vehicles, this assumption is hard to validate. Therefore, an observer-based feedback adaptive controller is presented that utilizes a nonlinear observer, and is capable of controlling a fully nonlinear longitudinal model of a hypersonic vehicle without measuring angle-of-attack. The observer is designed with the ability to lessen the influence of noisy measurement signals. All tracking and estimation errors are shown to be ultimately bounded, and the ability of this control architecture to track a command signal in the presence of noise is demonstrated on a high fidelity simulation.
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