Path Tracking Control Of Operational Quadrotor Platform

A quadrotor aircraft has simple structure and can achieve excellent performance.It's flexibility and stability in three-dimensional space in particular have drawn people's attention from various fields.Now the enthusiasm for researches on quadrotors matches that for ground vehicle in the last century.When equipped with different kinds of payload the quadrotors can carry out numerous tasks such as environmental exploration,3D map construction,cargo delivery,accurate agriculture and security monitoring,etc.It is our main goal in research to come up with a reliable flight platform to ensure the stable performance.In this paper,the following work is carried out based on the operational quadrotor platform.1.An experimental platform based on Pixhawk open source flight control system is built.The analysis on kinematics of the quadrotor aircraft is performed using rigid body dynamics,leading to a set of dynamical equations.Combining with the original navigation scheme,a framework of multi-sensor integrated navigation is developed based on Kalman filter.We tuned the parameters of Kalman filter to fit the sensor suit in our platform,in the pursuit of obtain accurate aircraft state estimation.2.A quadrotor aircraft is a highly nonlinear system,and it is easily affected by the disturbance brought by wind,blade flapping and induced drag,etc.Therefore,it is difficult to guarantee the performance of the cascade PID controller which is based on the linear small angle hypothesis and implemented in the original open-source flight controller.The Active Disturbance Rejection Controller proposed by professor Han works effectively well when addressing parameter uncertainty and time-varying nonlinear systems,with strong robustness to external disturbances.In this paper we present the nonlinear attitude controller based on ADRC method.And the idea of bandwidth in linear system is introduced to help simplify the parameter tuning process.3.Several common aerial trajectories are given for the operational quadrotor air-craft platform.Then we design corresponding linear and nonlinear controllers for tracking trajectories based on extended state observers(ESO),which can counter-act the total disturbance exerting on a quadrotor during flight.Next,a simulation of a two-dimensional quadrotor in lateral plane with suspended payload is carried out to verify the effectiveness of the controller proposed in this paper.4.Not only did we develop a set of theoretically reliable control strategy in this pa-per,more importantly,on the real platform we also achieved good experimental results.The videos of our experiments can be found in Youku channel(http://i.youku.com/i/UNjI4NjAwMTM2/videos?spm=a2hzp.8253876.0.0)Lastly,we gave a brief summary of the proposed theory and experimental ex-perience,along with analysis on the key points of building a stable quadrotor platform and some prospect for the future works.