Flight Control Law Design Of Tilt-rotor Aircraft Based On QFT

Tilt-rotor aircraft is a unique aircraft.It can fly as fast as the ordinary propeller aircraft,but also take-off and landing vertically like a helicopter.The flight control problem is the key to the research of the tilt rotor aircraft.The method to design the flight control law by QFT and PID has been researched in this paper.Firstly,based on the nonlinear flight dynamics model of the tilt rotor aircraft,the helicopter mode,tilting transition mode and airplane mode,have been trimmed with the assumption of small disturbance.The equation of motion was linearized.The stability and maneuverability of the aircraft were analyzed,which lays the foundation for the design of the control law.The operating efficiency of each control surface of the tilt rotor was analyzed,and the control strategy of the tilt rotor in different flight modes was obtained.Secondly,the good anti-interference and decoupling performance of the inner loop was ensured by use of QFT method(angular rate loop)to design the controller and filter.The stability of the system was improved.The classical PID control theory has been used to design the outer loop(attitude loop and speed loop)controller of the vehicle in the three flight modes.The simulation of the tilt rotor was carried out under the condition of full nonlinear control.At last,in view of the failure of the rudder surface in the tilting transition mode,the QFT controller has been used to design the redundant rudder surface.The fault model was analysed.The problem of control reconfiguration in the case of longitudinal channel failure was studied.The fully nonlinear model has been verified and ensured that the tilt-rotor aircraft after the failure can still be completed in accordance with the expected task.