Design Of Flight Control System For Small Twin-engine Fixed-wing UAV

The value of UAV is the ability to form an aerial platform that can be extended to other applications to complete aerial operations.With the development of technology,and the demographic dividend has gradually decreased,and manufacturing costs have been greatly reduced.UAVs have also been widely used in various fields.Based on the laboratory pre-research topic and the requirements of the project,to study and design the control law for the take-off,cruise and landing processes of small twin-engine fixedwing UAVs,a small twin-engine fixed-wing UAV experimental platform has been built in this paper.The research at the stage is mainly based on simulation,and almost no verification is performed on the actual small twinengine fixed-wing UAV,and there is no complete process.Therefore,this paper mainly relies on the twin-engine small fixed-wing UAV experimental platform to design the strategies and control methods of take-off,cruise and landing stages and to carry out real machine verification to improve the integrity and reliability of the algorithm and the small fixed-wing unmanned the overall framework of the machine experiment platform.1.First of all,combined with the research content of this subject,a small twin-engine fixed-wing UAV experimental platform has been built.Based on the easy-to-expand characteristics of the open source platform,the NIMBUS fixed-wing aircraft and the Pixhawk are used to design the twin-engine fixed-wing UAV experimental platform.In order to verify the reliability of the algorithm,the corresponding simulation environment are built.2.Thinking about the actual situation of the small twin-engine fixed wing used in this paper,a nonlinear mathematical model of the UAV is obtained.The nonlinear mathematical model is linearized,and the linearized model is identified by the recursive least squares method.In order to complete the design of the corresponding control algorithm,the linear state space model is obtained.3.In order to better design the control law of take-off and landing of small twin-engine fixed-wing UAVs,the actual take-off and landing tests are carried out and relevant key parameters are obtained.In order to better realize the take-off and landing of small twin-engine fixed-wing UAVs,a dual closed-loop PID anti-interference control strategy was designed for small twin-engine fixed-wing UAVs during take-off and landing,and in order to solve the overshoot and rapidity of PID controllers.The contradiction between them was added to the feedforward,followed by the semi-physical simulation of the takeoff/landing under the extremely harsh flight environment.Finally,the actual flight test was carried out.From the test results,the control effect is very better.4.Finally,the control law design of the small twin-engine fixed-wing UAV cruise phase was carried out.The small twin-engine fixed-wing UAV is in the cruise phase most of the time during the mission.Therefore,the path planning can help the UAV to achieve the optimal path selection from the starting point to the final point and the path algorithm tracking is designed.During the experiment,it was found that for the PID controller,the parameter adjustment is difficult,and it is necessary to continuously cooperate with the real-time flight to judge whether the current controller is adjusted enough.And for systems without coupling or weak coupling,the PID controller can achieve better results.In order to avoid major accidents during the flight,some state quantities need to be constrained.Therefore,the linear state space model obtained by the recursive least squares method is used to design the predictive controller.