The input constraints of control fr9967 surfaces may lead to saturations, which could limit the achievable performance or even cause instability of vertical take-off and landing (VTOL) tail-sitter unmanned aerial vehicle (UAV).To improve flight safety and attitude tracking performance, a novel L1 adaptive control architecture for attitude tracking of a tail sitter subjected to input constraints is proposed in this study.The imprecise mathematical model, low weight, and small size all present different challenges when designing a control system.In this work, a feedforward compensator is first used to narrow down the uncertain bounds with the consideration of finite accuracy from prior knowledge.Second, according to the linearized model, a baseline controller is thread feathers cabernet designed to offer basic performance for a nominal system without uncertainty.
Finally, the L1 adaptive controller is developed to compensate for unmatched uncertainties based on the control system developed before.The stability and performance bounds of the closed-loop system are analyzed to illustrate the impact of input constraints.The numerical simulations and flight tests are carried out to verify the improved attitude tracking performance when input saturation exists.