Demonstration of the optimal control modification for general aviation: design and simulation

Abstract

This work presents the design and simulation of a model reference adaptive flight control system for general aviation. The controller is based on previous adaptive control research conducted at Wichita State University (WSU) and the National Aeronautics and Space Administration (NASA) Ames Research Center. The control system is designed for longitudinal control of a Beech Bonanza given the commands of pitch rate and airspeed. The structure of the controller includes a first-order model follower, proportional-integral (PI) controller, inverse controller, and adaptation element. Two adaptation methods were considered, the WSU-developed Adaptive Bias Corrector (ABC) and the Optimal Control Modification (OCM). The ABC is used with two error schemes, adapting to the modeling-error and the tracking-error. Three variations of the OCM are presented, which differ in the parameterization of the adaptive signal. The first is called OCM-Linear (OCM-L), where the adaptive signal is linearly related to the states. The second variation is OCM-Bias (OCM-B), which only includes a bias term. The third is the OCM-Linear and Bias (OCM-LB), a combination of the previous two variations. To design the controllers, varied values of the PI gains and adaptive gains were evaluated based on time response tracking of a pitch doublet and time delay margin. The time delay margin is based on error metrics developed at NASA Ames. Of the five controllers presented, the OCM-L and ABC with tracking-error adaptation performed the best. The ABC with modeling-error adaptation did not track the pitch doublet. The OCM-B and OCM-LB are good controllers but had worse performance than OCM-Linear in tracking and time delay margin, respectively.