Research On Robust Control Technology Of Small-scale Unmanned Helicopter

The small-scale unmanned helicopter which is capable of vertical take-off and landing,hovering in the air,sideward flight and inverted flight can be categorized to the unmanned rotorcraft family.Compared with the fixed wing UAV,the unmanned helicopter has better maneuverability and greater flexibility in the process of the flight mission.It can be used in air reconnaissance,forest fire monitoring,water transportation,agricultural spraying and ground mapping and so on.Thus,it has widely prospect in application.Accordingly,the flight control of the small-scale unmanned helicopter has become one of the hot issues in the field of flight control.In this dissertation,the mathematical model of the helicopter is established,and the robust disturbance rejection flight control methods of the quadrotor under the influences of modeling errors,input constraints and external disturbances are studied.The main research contents are as follows:Firstly,the force of each component of the small-scale unmanned helicopter is analyzed.According to the mechanism modeling method,the nonlinear dynamic model of the unmanned helicopter is established.In order to facilitate the design of the controller below,the nonlinear dynamic model established is simplified.The linear model and the nonlinear simplified model of the small unmanned helicopter are obtained respectively.Then,the optimization control of the small-scale unmanned helicopter based on disturbance observer and robust servo LQR is studied.The coupling characteristics of the unmanned helicopter are analyzed.And the decoupled unmanned helicopter linear modes are obtained based on the principle of small disturbance.Based on the original LQR theory,the integral of the deviation of the input signal is introduced,and the servo LQR method is used to design the controllers.By considering the disturbance of the unmanned helicopter system,a linear disturbance observer is introduced to estimate the external unmeasured disturbance,and the tracking controller is designed based on robust servo LQR and disturbance observer output.Simulation results show that the unmanned helicopter's position and attitude tracking effect and the system robustness is better.Next,the optimization control of the small-scale unmanned helicopter with quantitzed input is studied.Taking into account that the unmanned helicopter control signal may be subject to interference in the transmission process.Therefore,the quantifier is introduced to enhance the control signal immunity.Based on the unmanned helicopter's linear models,the controlle is designed by Backstepping method and the stability of closed-loop system is proved by Lyapunov function.In order to get the best control effect,the particle swarm optimization algorithm is used to adjust the controller parameters in the Backstepping method.Furthermore the validity of this method is verified by MATLAB simulation.It can be seen from the simulation results that the control method proposed in this paper can realize the position and attitude tracking of the unmanned helicopter and the controller parameters obtained through the optimization algorithm make the best controller performance.Following,the optimization control of the small-sacle unmanned helicopter based on disturbance observer and SDRE is studied.Considering the high order of unmanned helicopter system,the unmanned helicopter system is divided into four subsystems,which are position loop,velocity loop,attitude loop and attitude angular rate loop.Furthermore,the SDRE method is used to design the controller for each subsystem.By considering that the unmanned helicopter system with the disturbance,the nonlinear disturbance observer is introduced to estimate the unmeasured disturbance.Combined with the output of SDRE and disturbance observer,the tracking controller is designed.The simulation results show that the designed control method makes the unmanned helicopter more robust under external interference and has better tracking performance.Finally,the 3D visual simulation of the small-scale unmanned helicopter is studied.In the previous section,the flight control problem for unmanned helicopter was studied,and the effectiveness of each control method was verified by numerical simulation.In order to simulate the actual flight of the small-scale unmanned helicopter,computer simulation technology that is three-dimensional visual simulation is used to reproduce the unmanned helicopter trajectory tracking process.Here,Visual C ++ 6.0 is used to design the software platform and OpenGL draws three-dimensional objects and natural objects.The final scene simulation shows that the designed software platform can effectively simulate the trajectory tracking of small unmanned helicopters.