The Study On Control Strategies For 3-DOF Helicopter Experimental System

Helicopter system is a nonlinear, multivariable, strong coupling of complex systems, it is difficult to establish accurate mathematical model of the helicopter. There are also many uncertainties while actual flight. Therefore, the design of the helicopter flight control system must be able to quickly respond to the helicopter pilot's operation commands and have strong robustness to the outside interference, in order to ensure the stability of the helicopter flight. In this paper, the 3 degree of freedom (3-DOF) helicopter is used as the model of tandem rotors helicopter to simulate its flight attitude, the flight controllers are designed to tracking control the helicopter flight attitude. The experiment results proved the effectiveness of the algorithms. Full-text includes the following components:First of all, the characteristics and classification of helicopters, the development status of modern flight control system, the current research situation and their advantages and disadvantages based on 3-DOF helicopter model are introduced. The hardware, software composition and flight movement pattern of the3-DOF helicopter are detailed described. When the helicopter on its ideal stability flight position, the linear mathematical model of the 3-DOF helicopter is established based on the 3-axis dynamic equation, and the stability, controllability and observability of the mathematical model are analyzed.Second, the basic principles of the PID controller, fuzzy controller, fuzzy self-tuning PID controller and their respective advantages and disadvantages are introduced. According to the linear mathematical model, conventional PID controllers based on LQR are designed for the helicopter's 3 axes. Two fuzzy self-tuning PID controllers are designed for the elevation and travel axis of the helicopter, in order to control the helicopter elevation angle and travel speed. For the two control strategies, two sets of experiments that without/with active disturbance system (ADS) are designed. By comparing the control effects of the conventional PID controller and fuzzy self-tuning PID controller, the conclusion can be reached that fuzzy self-tuning PID controller not only makes the helicopter be able to quickly track the fixed flight attitude, but also makes the system have better stability and robustness.Again, the basic principle of guaranteed cost control and linear matrix inequalities (LMI) toolbox are introduced. Consider the extreme value of elevation angle, pitch angle and the friction in the 3 axis while the helicopter model actual flight, the linear uncertainty matrix of the helicopter mathematical model is obtained. Guaranteed cost controller is designed for tracking control the helicopter elevation angle and travel angle. Two experiments without/with ADS are designed, experimental results show that the guaranteed cost controller enable the helicopter has a faster track for the given attitude, and has good stability and robustness.Finally, the research work in this thesis is concluded, and the interested directions and research goals in the future are described.