Design And Implementation Of Multi-mode Flight Control System For Small Scale Unmanned Helicopter

Small scale unmanned helicopter has variety of flight modes, such as vertical taking-off and landing, hovering, coordinated turn, longitudinal flight, lateral flight and so on. It has broad application prospects for the reason of its special flight capabilities. In this paper, the small scale unmanned helicopter is taken as the research object. The research is focused on multi-modal flight control and switch control, and the obstacle avoidance algorithm based on the optical flow technology is proposed which realizes the appilication of bionic technology "optical flow" for autonomous obstacle avoidance of the small unmanned helicopter. The feasibility of multi-modal flight controller and algorithm for autonomous obstacle avoidance are verified through simulation. Eventually an original flight control system is accomplished and the actual flight of small scale unmanned helicopter is successfully realized.Firstly, a nonlinear mathematical model on small scale unmanned helicopter is established and linear models is obtained through small-disturbance linearization technique. The flight modes of small scale unmanned helicopter are divided and analysed. On this basis, the control law of inner and outer loop based on PID is designed and for different flight modes, corresponding controllers and switch controllers is designed respectively. The designed controllers are validated by digital simulation.Secondly, in order to increase the autonomy of small scale unmanned helicopter flight, bionic technology "optical flow" is applied to the autonomous obstacle avoidance of small scale unmanned helicopter in this paper. Optical flow principle and the relationship with the sports ground are analyzed, an obstacle avoidance algorithm based on optical flow is designed. And then through the creation of three-dimensional virtual environment, the feasibility of this algorithms is verified.Then, the multi-modal flight control system of small scale unmanned helicopter, which includes hardware and software platforms, is designed and implemented. From the perspective of mission requirements and functional realization, the whole design scheme of flight control system is also developed. The design of fight control computers, sensor systems, actuator, communication are accomplished. In order to achieve rational distribution and management of tasks, a master-slave processor framework is adopted for flight control computer; and flight control software is designed based on the task.Finally, this flight control system is applied to the real small scale unmanned helicopter, static experiments as well as outdoor flight tests show that the multimodal flight can be well realized and flexibly controlled by the controller. Experimental results show that the design of flight control system is stable and operable. The small unmanned helicopter can be controlled by the multi-modal control system, which has a character of high performance. It is significant for the engineering realization of control system.