Combined DI /QFT flight control for a quad-rotor unmanned helicopter

A nonlinear dynamic model for a quad-rotor unmanned helicopter is established.Considering the uncertainness and nonlinearity of the model,a method combining Dynamic Inversion(DI) with Quantitative Feedback Theory(QFT) is used to design a robust controller for attitude loop of the unmanned helicopter.The dynamic inversion method is used to treat the nonlinearity,which makes the system equivalent to a decoupled and uncertain linear object.Since dynamic inversion controller can not satisfy the control requirement when perturbation exists in pneumatic parameter,a QFT controller is designed.The QFT controller can overcome the uncertainties and ensure the robust stability of system.Simulation result showed that the DI/QFT controller can implement precise control to the attitude angle when pneumatic data varies within 20%.