K-modification and a novel approach to output feedback adaptive control
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This dissertation presents novel adaptive control laws in both state feedback and output feedback forms. In the setting of state feedback adaptive control K-modification provides a tunable stiffness term that results in a frequency dependent filtering effect, smoother transient responses, and time delay robustness in an adaptive system. K-modification is combined with the recently developed Kalman filter (KF) based adaptive control and derivative-free (DF) adaptive control. K-modification and its combinations with KF adaptive control and DF adaptive control preserve the advantages of each of these methods and can also be combined with other modification methods such as - and e-modification. An adaptive output feedback control law based on a state observer is also developed. The main idea behind this approach is to apply a parameter dependent Riccati equation to output feedback adaptive control. The adaptive output feedback approach assumes that a state observer is employed in the nominal controller design. The observer design is modified and employed in the adaptive part of the design in place of a reference model. This is combined with a novel adaptive weight update law. The weight update law ensures that estimated states follow both the reference model states and the true states so that both state estimation errors and state tracking errors are bounded. Although the formulation is in the setting of model following adaptive control, the realization of the adaptive controller uses the observer of the nominal controller in place of the reference model to generate an error signal. Thus the only components that are added by the adaptive controller are the realizations of the basis functions and the weight adaptation law. The realization is even less complex than that of implementing a model reference adaptive controller in the case of state feedback. The design procedure of output feedback adaptive control is illustrated with two examples: a simple wingrock dynamics model and a more complex aeroelastic aircraft transport model.