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Many potential applications of adaptive control, such as adaptive flight control systems, require that the controller have high performance, stability guarantees, and robustness to time delays. These requirements typically lead to engineering trade-offs, such as a trade-off between performance and robustness. In this paper, we examine a combined/composite model reference adaptive control (CMRAC) approach that can be used to achieve higher performance as well as higher levels of robustness. The CMRAC design is validated with flight tests of a light-weight, low-cost quadrotor UAV platform inside an indoor test facility. The combined/composite adaptive controller was found to offer increased robustness to parametric uncertainties. The design of the combined/composite adaptive controller is presented, followed by a comparison with the existing linear controller and a direct adaptive controller.

RECENT RESULTS IN ADAPTIVE FLIGHT CONTROL SYSTEMS x m .t /. The underlying Lyapunov function is quadratic in e and the parameter error   , with a negative semi-definite time-derivative P V [5]. ‡ The argument t is suppressed for the sake of convenience, except for emphasis. § One can choose to set to zero if k k 6  max , as performed in [4,7] and many other references in the literature.Assumptions 1 and 2 are standard and imply a minimal realization of the transfer function (26). Assumption 3 implies that the relative degree is unity. Assumption 4 is standard in the case of full states accessible adaptive control but is more restrictive than the classical output feedback case.