Research On Flight Control Technology Of A Quad-rotor Unmanned Helicopter

Quad-rotor unmanned helicopter is an excellent, novel and simple structure unmanned helicopter (UMH) for both military and civilian usages. This paper concentrates on its characteristics, mainly researches the problems on mathematical modeling and flight control law. This article attempts to use Dynamic Inversion (DI) and Variable Structure Control (VSC) method to design a flight control law for Quad-rotor unmanned helicopter.At first, characteristics and motions of Quad-rotor unmanned helicopter are analyzed. The 6-DOF nonlinear dynamic model is given; its dynamic characteristics are discussed in detail. Then, the classical control method is used to design a flight control law for Quad-rotor unmanned helicopter.The control system is divided into three subsystems based on time-scale theory: the fast-variable subsystem, the relatively fast-variable subsystem and slow-variable subsystem. Then, DI is applied to three subsystems, the system employing DI has perfect dynamic characteristics, but the robustness is weak. The control system of Quad-rotor unmanned helicopter must resist the uncertain of aerodynamic parameters and disturbance, so VSC is applied to the robustness. This control law is easy and fit to engineering.The result of emulator shows that flight dynamic inversion method is an exact linearization manner, the outcome from theory would be more approving, if the model is exacter. However, there are some uncertain of aerodynamic parameters and disturbance, so the result is always not satisfying. This problem is resolved by using VSC robust control method. It makes the control system has greater performance in dynamic, loose-coupled and robust. So the control system employing DI and VSC can work effectly when applied to Quad-rotor unmanned helicopter.