The Research On Autonomous Takeoff And Landing Control Strategy For Small-scale Unmanned Helicopter

Small-scale unmanned helicopter (SUH) has received extensive attention from the researchers all over the world, as a result of its widely application prospect in both in military and civilian domain. Autonomous takeoff and landing is an important process of autonomous flight control, which lasts shortly and demands for precisely control. Abundant experience is required in manual flight control, yet safety is not ensured. Therefore, to enhance flight ability of SUH, it is quite important to realize safe autonomous take off and landing.This dissertation takes a certain type of SUH as flight platform. The hardware-in-loop simulation experiment and flight experiment have been combined to discuss and research the control strategy of autonomous takeoff and landing as well. The main work of this dissertation is:(l)At first, the current progress of SUH, as well as the research of autonomous takeoff and landing, key technology and difficulty is presented. Then the architecture of flight control system for this platform is introduced, and the key technologies of ground control station are solved. At last a full state nonlinear model of SUH for takeoff and landing is established by combining first-principles and system identification methods, which is linearized by microvariations method.(2)The influence of ground effect on takeoff and landing is analysed, then the solution is presented and verified the validity by experimental results. According to the requirement of altitude measurement for takeoff and landing, the outliers filter and re-adjusted methods are adopted to fuse the vertical velocity and sonar altimeter which ensure the accuracy and instantaneity of altitude measurement.(3)Because of the unbalanced moment before takeoff, the pressure sensor has been installed on undercarriage to measue the force as the feedback to realize the automatic balancing of force and moment before takeoff, which can make SUH vertical takeoff without ground constraints.(4)According to the control requirements of autonomous takeoff and landing for SUH, the control strategy has been proposed and verified rationality and validity by hardware-in-the-loop simulation experiment. Finally, autonoumous landing experiment has been fulfilled. The experiment results have shown that the control strategy of autonomous landing can realize the autonoumous landing task successfully and ensure the accuracy of the landing in the range of 1 meter. In addition, the strategy based on the finite state machine mode scheduling is effective to finish landing mode scheduling, and the safety in the process of landing is ensured, therefore the autonomous flight ability of SUH has been improved greatly.