| Generally, helicopter is statically unstable, the flight control system of helicopter is nonlinear, multi-variable and strong-coupling, and the airscrew's aerodynamics characteristic is very complicated, besides of that, much uncertain factors are also in the actual flight. So, the flight control system of helicopter must have strong robust characteristic in order to deal with the disturbances from the outside and unknown uncertainties. The robust flight control system can ensure better stabilization and safety of helicopter.In this paper, the characteristic of helicopter and the development of the flight control system are briefly introduced, and the requirement of robust control in the flight control system of helicopter is derived. The mathematic modal of the helicopter is established. Two robust control methods — H_∞ control and guaranteed control which using in the paper are expatiated. And the key techniques of the two robust control methods, like how to establish the linear matrix inequation,how to realize the optimize process and how to use the LMI tool boxes are stressed in the corresponding chapters.In the last two chapters of the paper, how to stabilize the three angles of the helicopter when there are unknown uncertainties and the disturbances from the outside is researched. First, establish the state feedback model of the helicopter. Then, choose the one flight parameter from the parameters group. Finally, use the LMI tool boxes to simulate the model, and compare the control effect with the one using classic control method. According to the comparing results, the robust controller can effectively restrain the closed loop disturb, strengthen the stability of the system, improve the robust performance.The research in the paper is not only a theoretic research, it stress that advanced theory must be used into project. The study solves the stability problem of helicopter's complex system to some degree, and provide a new method to design helicopter controller.
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