Study For The Design And Control Methods Of The 3 DOF Helicopter

With the more and more popularity of helicopters in both military and civilian areas, the aircraft control theories are also increasingly given attention by domestic and foreign researchers. But at present the helicopters are still very expensive and it costs too much to use it in the experiments. Considering the security and economic factors, helicopters can be simplified as a model to simulate its flight, which provides a more convenient way for the research of aircraft theories and technologies. The 3 degree of freedom (DOF) helicopter is the model which can simulate parts of the helicopters’ movements. It has the characteristics of multi-input multi-output (MIMO), nonlinearity and, strong coupling etc. This model can verify the control theories and algorithms, and it the mainly used in the researches and teaching experiments.In the article a 3 DOF helicopter experimental platform is proposed. The platform includes two parts of the mechanical structure and the embedded control system. The PID control algorithm is applied in the system. And the neural network adaptive control theory is researched to control the elevation axis of 3 DOF helicopter. The main research contents are as follows:1) First the overall design scheme of the 3 DOF helicopter is formulated. On the basis of modularization, the rotating shaft, pitch, elevation and travel axes and other parts are designed. Also, the processing and integrated debugging procedure of 3 DOF helicopter are introduced. Then the mathematical model of pitch, elevation and travel axes is built based on the measured parameters.2) The embedded control system, including the data acquisition module, communication module, motor control module, host computer and slave computer, is constructed for the 3 DOF helicopter. The sensors consist of the incremental encoder and gyroscope, accelerometer sensor integrated in MPU6050. The data acquisition system can achieve angles and speeds of the three axes. Meanwhile the serial communication protocol is designed to transfer data between the chip and the PC software. And the DC motor is controlled based on PWM technology.3) The PC software is designed based on VC++, through which the commands and data can be transmitted to control the 3 DOF helicopter and its real-time altitudes can be monitored. The commands include starting and stopping the system, setting the attitude, debugging the control algorithm etc. Besides via the interface of PC software users can choose the way that angle and rotating speed of three axes display to observe the overall results or the control effect during a period of time.4) PID control algorithm is used to control the pitch, elevation and travel axes of 3 DOF helicopter. The simulation results are obtained using MATLAB, and the input is step signal. To test the system and verify the effect of PID control algorithm, the experiments is done to control the 3 DOF helicopter, and the results indicate that the system has been basically controlled.5) Finally, the principle and structure of neural network adaptive control algorithm is studied, and a neural network adaptive controller is designed to control the elevation axis of 3 DOF helicopter. Also, it is verified in the simulation and experiment. Compared with the PID controller, it’s clear about that the PID controller can make the elevation axis be controlled easily, but the steady-state error and slow response exist. The neural network adaptive controller improved the control effect. The steady-state error is reduced, and the accuracy and speed are also raised.