Research On Flight Control And Visual Flight Simulation Of The Helicopter

Due to its special flying abilities, helicopters have been widely used in military and civilianapplications. Helicopter flight control is an important research topic in the studies of helicopters, andmathematical modeling, control system design and flight simulation are the three main directions inthe field of helicopter flight control. In this background, this thesis studies helicopter modeling,control system design and flight simulation.Firstly, the flight dynamics model of helicopter is established. According to the calculations ofaerodynamic forces and moments from different parts of the helicopter, the nonlinear dynamics modelof the helicopter is established and built in Matlab/Simulink. For the purpose of controller design,linear models of the helicopter in several special flight conditions such as hovering and low speedflight are obtained based on linear perturbation theory. The linear models are then used for designingcontrollers for the flight channels such as lateral, longitudinal, directional and altitude.Secondly, according to the analysis of the stability and coupling effects of the helicopter, controlstrategies and control laws are studied. The flight control laws of stability augmentation is designedfor hovering situation by using the PID method, based on which, the automatic control laws includingheight controller, course controller and trajectory controller are designed for the altitude-holdhovering. The results from integrated simulations of the control laws show that the parameters of thedesigned controllers are valid.Thirdly, considering the wide variations of models in different trimming points, QFT basedhelicopter nonlinear controller is designed for helicopter in low speed flight conditions (0~40Knots).An introduction of basic design procedure of QFT for MIMO system is given at the first, and thenbased on the QFT theory, the predefined performance requirements are transferred into a series ofboundaries with constraints in the Nichols chart, and the attitude controllers are then designed tosatisfy those boundary constraints. The results show that QFT method can successfully resolve therobust problem in the presence of model parameter uncertainties.Finally, on the VC6.0platform, a real-time visual flight simulation system based on FlightGearsimulator is developed. The system includes control system, dynamic model and FlightGear simulator.Control system and dynamic model are developed in C language so that can simulate the flightdynamics and control system effects of the helicopter in real time, and FlightGear provides realisticvisual simulations for the motions of the helicopter. The three parts are integrated together using serial port and UDP protocol based network communication to form a system, which can provide real timevisual flight simulations for the helicopters.