Three-DOF Helicopter Modeling And Control Method Research

Compared to other models, the greatest advantage of the helicopters is thatthey can do hover, low-altitude, low-speed and head direction remains unchangedflight. Especially, they can takeoff and landing vertically in a small area. Thesecharacteristics make the helicopters have wide use and development prospects.They have been widely used both in military aspects and civilian aspects, such as:Ground attack, reconnaissance patrols, anti-submarine and mine clearance,medical assistance, disaster relief, aerial photography. Helicopter flight controlsystem is a common type of high order, nonlinear, multiple input multiple output(MIMO) system, which is unstable, and has strong channel couplingcharacteristics. It is a relatively complicated controlled object in controlengineering field. Helicopter models used for scientific experiments or teachinghave been made by domestic and foreign manufacturers. They can partly simulatethe real helicopter flight status and features. So they are powerful tools and idealmodels to test the effectiveness of various control theory and control algorithms.This paper makes a study of the GHP2002three degree of freedomhelicopter model produced by Googol Technology (Shenzhen) Limited, mainlyon the helicopter flight attitude stability control problem. The control effect ofdifferent control algorithms and theory are analyzed and compared in this paperas well.Firstly, the basic structure and working principle of the3-DOF helicoptersystem is introduced in detail. Secondly, approximate transfer function model foreach degree of freedom and state space model of the helicopter control systemare established by rigid body dynamics analysis. Stability, controllability andobservability of the3-DOF helicopter system is analyzed as well. Thirdly, aseparate PID adjustor is designed for each channel according to thecharacteristics of the three channels and MATLAB simulation of the corrected system is made. Then, the basic principle of the linear quadratic optimal controlis introduced, and a LQR controller is designed. The Simulink simulation modelsare set up and the two control algorithms are simulated and compared. Finally,the real-time control effect of these two kinds of controllers is verified andcompared on the3-DOF helicopter platform.MATLAB simulation and system real-time control experiment results showthat the two control algorithms are both effective and the control effect is good.But compared with traditional PID control, the LQR control has better dynamicperformance, which mainly reflects in: faster response, smaller overshoot, shorteradjusting time, better stability and robustness.