Adaptive Control Design for Nonaffine Models Arising in Flight Control

Adaptive tracking control algorithms are developed for a class of models encountered in flight control that are nonaffine in the control input. The essence of the approach is to differentiate the function that is nonlinear in the control input and obtain an increased-order system that is linear in the derivative of the control signal and can be used as a new control variable. A systematic procedure is developed and related theoretical and practical issues are discussed. The proposed procedure, referred to as the controller for nonaffine plants, is developed for several cases of nonaffine models with unknown parameters. It is shown that the key aspect in the adaptive control design is the definition of the estimate of the derivative of system's state, which results in a convenient error model from which the adaptive laws can be written in a straightforward manner. The proposed approach is tested using a three-degree-of-freedom simulation of a typical fighter aircraft and is shown to result in a substantially improved system response.