Research On Control Method Of Electric Tail Rotor For Small Unmanned Helicopter

The unmanned helicopter electric tail rotor uses the motor to drive the helicopter tail rotor.Compared with the mechanical transmission tail rotor,the electric tail rotor has simple mechanical structure,easy maintenance,low noise,low vibration,clean and pollution-free,and high reliability.In addition,the electric tail rotor is decoupled from the main rotor of the helicopter to improve the flexibility and yaw mobility of the tail rotor control.In this thesis,the pylon channel of the small unmanned helicopter electric tail rotor is taken as the research object,and the nonlinear auto disturbance rejection control method is used to control the yaw passage of the helicopter electric tail rotor.Firstly,the power of the tail rotor of a helicopter is calculated.The power calculation can be used as a reference for selecting the motor for the electric tail rotor system.Secondly,the power consumption of the electric tail rotor increases and decreases with the increase of the speed of the tail rotor.Therefore,helicopter flight conditions with low yaw maneuverability can be selected,such as reducing the speed of electric tail rotor in hovering to reduce the power consumption of tail rotor.Secondly,according to the control requirements of the yaw channel of the electric tail rotor,such as the large dynamic uncertainty of the course channel,non-linear aerodynamics,external disturbances and disturbance factors of the system itself.The control method is not highly dependent on the model of the electric tail rotor and the control parameters can be adjusted.After analysis,the nonlinear ADRC control meets the control requirements of the electric tail rotor.Therefore,the nonlinear ADRC control method is selected to control the yaw channel of the electric tail rotor.Then,the simulation model of the yaw channel of the electric tail rotor is established,and the control model of the ADRC is established.The simulation results show that the yaw angle of the output of the electric tail rotor is fluctuated slightly by the conventional ADRC yaw channel.The reason is that the inflection point of the non-linear function in the control law is not smooth.In order to eliminate yaw angle jitter,the non-linear function of ADRC law is improved.The improved non-linear function not only smoothes the inflection point,but also changes the shape,center position and amplitude of the function.Simulink control model of improved nonlinear ADRC is established.Combining with the aforementioned electric tail rotor model,simulation results show that the improved ADRC eliminates yaw angle jitter and has faster response time than conventional ADRC.Finally,according to the helicopter flight conditions,the helicopter has the lowest requirement for yaw maneuverability in hovering,so we choose to reduce the speed of electric tail rotor when the helicopter hovering,and increase the speed to the standard speed in other flight conditions.In order to maintain the helicopter hovering attitude,the pitch angle should be increased while the speed decreases.Therefore,the change trend of pitch angle is opposite to that of tail rotor speed.The yaw channel of helicopter with variable tail rotor speed is controlled by improved non-linear ADRC.The simulation results show that the maneuverability of helicopter decreases and the power can be saved by about 20% when the tail rotor speed decreases.Then the control method of the yaw channel of the electric tail rotor is validated on the ground test bench.The experiment shows that the control method is effective.