Research On Airborne Platform Control System Of Multi-rotor UAV

As the main mission payload platform of UAV,the multi-rotor UAV airborne stabilized platform is widely used in aviation surveying and mapping,object tracking and positioning,military strike calibration,aviation investigation,aerial photography and other fields.The purpose of airborne stabilized platform is to isolate the disturbance of the airframe so that the visual axis of the mission equipment can track the designated target quickly and stably on the basis of keeping the space orientation constant.In the field of UAV aerial photography,the stability of airborne stabilized platform is an important factor affecting the quality of aerial photography.It is of great theoretical significance and engineering application value to design and research an airborne stabilized platform with high stability accuracy,small overshoot and fast response speed.In this paper,the multi-rotor UAV airborne stabilized platform is taken as the research object,and the following aspects are studied in depth.（1）The frame structure and characteristics and characteristics of the airborne stabilized platform are introduced.The principle of airborne stabilized platform and the interference sources that affect the control performance of airborne stabilized platform are analyzed comprehensively.At the same time,the traditional control system of airborne stabilized platform adopts the mode of individual control of each frame.The dynamic coupling existing in the working process of airborne stabilized platform is not deeply analyzed,which causes interference to the control accuracy to some extent.In order to solve the appeal problem,based on Newton Euler dynamic equation,a more perfect three degree of freedom dynamic coupling model is established,and its specific dynamic equation is given.Then,the dynamic coupling model is reasonably simplified according to the characteristics of engineering application.Finally,combined with the mechanical and electrical principle of the motor and the actual parameters of the pan tilt motor,the mathematical model of the motor and the precise model of the pan tilt servo control circuit are derived.（2）This paper describes the attitude detection process of airborne stabilized platform.The attitude detection of airborne stabilized platform directly affects the performance of platform control system.In this paper,MEMS inertial sensor is used to detect the attitude of airborne stabilized platform.Then,the reference coordinate system which is often used in attitude calculation is introduced.The basic principle,advantages and disadvantages of the commonly used attitude angle calculation methods are analyzed in detail.The Quaternary method is selected to calculate the attitude angle of the airborne stabilized platform.Finally,aiming at the shortcomings of single sensor attitude detection,in order to further improve the stability and accuracy of attitude detection,the complementary filtering algorithm is applied to multi-sensor information fusion attitude calculation.（3）The double closed loop PID control strategy of the airborne stabilized pan tilt control system is proposed.The simulation model is built by using the Simulink toolbox of MATLAB,and the control performance of the traditional PID controller is analyzed in detail.At the same time,aiming at the problems of traditional PID controller parameters optimization timeconsuming and the optimal control performance is difficult to guarantee,a method based on cuckoo search algorithm to optimize PID controller parameters is proposed.The simulation results show that compared with the traditional PID control system,the PID control system based on cuckoo search algorithm has the advantages of smaller overshoot,higher steady-state accuracy and stronger disturbance resistance.（4）The verification system of airborne stabilized platform is designed.According to the comparative analysis of the advantages and disadvantages of the commonly used actuators and the application characteristics,the brushless DC motor is selected as the actuator of the airborne stabilized pan tilt,and the airborne stabilized pan tilt system is designed,and the indoor stability enhancement test and outdoor aerial photography test are carried out.The test results show that the picture is stable and clear without obvious jitter.The experimental results show that the multi-rotor UAV control system designed in this paper has obvious stability enhancement effect,strong anti-interference ability and high tracking accuracy,which can meet the design requirements of the system.