Frantisek M. Sobolic

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Retrospective cost adaptive control (RCAC) is a discrete-time adaptive control algorithm for stabilization, command following, and disturbance rejection. RCAC requires knowledge of the nonminimum-phase (NMP) zeros in the transfer function from the control input to the performance variable. This knowledge is embedded in the target model used to define the(More)
Unanticipated and unknown changes in an aircraft’s aerodynamic stability derivatives may cause undesirable effects that render pre-designed control laws unsuitable for maintaining stability. Gradual changes in the stability derivatives may be due to icing on lifting surfaces, whereas structural damage may cause a sudden change. For this study, we use the(More)
We use retrospective cost adaptive control (RCAC) with a constant forgetting factor (CFF), variable forgetting factor (VFF), and Kalman Filter (KF) to control a planar missile with nonlinear dynamics and aerodynamics. RCAC/CFF, RCAC/VFF, and RCAC/KF are used within an inner-loop/outerloop control architecture, where the normal acceleration command is used(More)
Retrospective estimation of the process noise covariance is performed by minimizing the cumulative stateestimation error based on the innovations. This technique is applied to parameter estimation problems, where the parameters to be estimated are time-varying and thus do not fit in the classical Kalman filter noise structure. This technique is compared to(More)
We consider retrospective cost adaptive control (RCAC) of a plant whose NMP zeros are time-dependent. The goal is to estimate the NMP zeros and replicate the estimated NMP zeros in the target model used by RCAC. This problem is challenging due to the fact that the estimates of the locations of the NMP zeros must be sufficiently accurate at each instant of(More)
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