Research On Robust Flight Control Technology Of Nano Quadrotor Unmanned Aerial Vehicle

Nano quadrotors are classified as a type of very small unmanned aerial vehicles,which have many good flight characteristics and high value in research,therefore,the academic community is paying more and more attention on them,and their application in both military an dcivil fields has emerged in recent years.Working on the design and implementation of the nano quadrotor platform,this thesis focuses on mathematical modeling and parameter measurement,error analysis of sensors and flight attitude estimation,disturbance compensation-based flight control methods,loop shaping –based robust control method.Main contents are shown as follows:Firstly,the nonlinear and linear mathematical models for nano quadrotor are established.Based on reasonable force analysis of a nano quadrotor,the balance equations for force and moment are derived,and nonlinear dynamic model containing translational equation and rotation equation are established.To obtain the parameters of the mathematical model,experiment for measurement of moment of inertia,lift coefficient,reverse torque coefficient was designed and carried out.Linear parameter varying is adopted for model linearization to facilitate control law design.Then,an algorithm for flight attitude estimation based on low cost MEMS sensors is designed.Considering of sensor errors,measurement model and error characteristics of the MEMS inertial components are analyzed and basic calibration for data of electronic compass is performed.Common attitude estimation methods are briefly introduced,and the theory for classic complementary filtering algorithm is detailed,with their merits and demerits analyzed.For outliers may emerge in measurement,quaternion-based robust extended Kalman filter method is designed,and Matlab simulation and experiment on nano quadrotor are carried out to verify the effectiveness of the designed attitude estimation method.Next,focusing on the disturbance in the flight of nano quadrotors,control methods based on observer compensation are designed.Classic cascade PID control is introduced,with the principles and disadvantages analyzed.To overcome the limitations of conventional PID controller,active disturbances rejection controller,which is evovled from PID controller,is presented,with the function of each components analyzed in detail.Employing advantages of active disturbances rejection controller,extended state observer-based nonlinear cascade PID controller is designed.Comparative simulations of the three methods are carried out to demonstrate the effectiveness of the controller designed.Following,considering of model uncertainties and external unknown disturbance on nano quadrotors,a robust control method based on H infinite loop shaping is designed.In terms of model uncertainties,methods for their description are introduced with left coprime factorization adopted.Base on the analysis of solving methods of robust stability problem,the concept and design procedures of loop shaping methods are introduced,and the design of compensator is further discussed.In order to realize practical application,the order of the robust controller designed is reduced,and simulation is carried out to demonstrate the effectiveness of the controller with reduced order.Finally,a platform for nano quadrotor is established,with the hardware structure,software structure and supporting test gears detailed.Flight tests based on the designed nano quadrotor were carried out to demonstrate the feasibility of the whole platform and related algorithms.