Study And Design Of Flight Control Systems For Small Scale Quadrotors

Rotary-wing aircrafts have many military and civilian applications due to their requiring small areas for taking off and landing, great maneuverability in obstacle-heavy environment and great ability to maintain the position and orientation. The research of small scale quadrotors, one kind of rotary wing aircrafts, have gradually become mature in recent years, and also provided an important platform for investigations in such fields as the autonomous control, advanced sensor technology and computer science. Investigations on the control system of small scale quadrotor proved to be of high value in such applications as intelligent control of the aerial robot, 3D trajectory planning and the air traffic management and collision avoidance of multi aircrafts.In this paper, different kinds of flight control algorithms applying to the small scale quadrotor are presented, and a large number of simulations on these control algorithms are made. This paper demonstrates all the work we have done and the final results we have achieved which are outlined as follows:1) Small scale quadrotor modeling: An essential point we held when we did the modeling is to treat the quadrotor as a rigid body. Those forces and moments which have significant effects on the quadrotor are selected and the dynamic equations for the three linear translations and three angular rotations are considered and deducted according to the Newton's law of machnics and Euler Equation.2) The control strategy based on the classic PID method: According to the dynamic model of the small scale quadrotor, a control system based on the classic PID method is devised. The whole control system is separated into two parts, namely the inner loop control (angular rotations control) and the out loop control(translational position control), and designed each of them respectively. The simulation results showthat with this control strategy, the quadrotor can reach the target position accurately and keep its stabilization when hovering.3) The control strategy based on the Backstepping method: A control strategy is designed based on the Backstepping method to cope with the quadrotor's non linear and sub-actuate dynamic model. The formula of the control variables are calculated out by applying the Backstepping method according to the quadrotor's state equations. The simulation results indicate that this control strategy greatly improves the system's response in terms of its overshoot, rise time and settle time.4) The adaptive control strategy based on the Backstepping method: Based on the controller designed in the last step, the estimators of the unknown mass and external disturbances are added. The simulation results illustrate that the quadrotor is able to keep its stabilization when its mass decreases in a stair-like way and the external disturbances of some certain patterns exist.This paper is closely centered on the control strategy design based on the dynamic model of the quadrotor. The whole design process was guided by one methodology: Start with the simple, and increase the complexity bit by bit. Each time one new control strategy is added based on the former one, and finally the adaptive control strategy under which the quadrotor was highly stabilized is developed, which is illustrated by the simulation. This robust control strategy provides a vital theoretical foundation for the practical application of the quadrotor.