Study On Image Stabilization Technology For The Payload Of MUAV

The payload of m UAV(multi-rotors Unmanned Aerial Vehicle) often influenced very easily by disturbances such as gesture variety, atmospheric turbulence, fuselage vibration, friction, etc. The disturbances make the airborne videos and images shaking, blurring, and influence the application in military and civilian domains of m UAV seriously. Therefore, the studies on the disturbance compensation methods and the stability control technologies of payloads mounted on m UAV have great practical significance. The research object of this paper is the airborne platform system which is mounted on a Hex-rotor m UAV. The Hex-rotor m UAV was developed by our research group independently. The disturbance compensation methods and stability control technologies of the airborne platform system were in-depth studied by the theoretical analysis and experimental verification.This paper firstly outlines the development status and trend of micro payloads, and summarizes the research situation of disturbance compensation methods and stability control technologies of payloads at home and abroad. The model of the airborne platform system and the model of pitch-channel, yaw-channel, and roll-channel were established. The disturbances existing on each channel, the coupling disturbances existing on inter-channels and the main sources of disturbance and their impact on the image quality of the payloads have been analyzed in detail, which provided the theoretical foundation for research and implementation of disturbance compensation and stability control methods.For the requirements of disturbance compensation and stability control of the airborne platform, a fuzzy adaptive compensation control method based on an Improved Velocity Disturbance Observer(IVDOB) is proposed. From the perspective of disturbance compensation ability, the ability of compensate for noise of Velocity Disturbance Observer(VDOB) is improved by introduced a compensation control structure, the robust stability of IVDOB is analyzed. For improve the ability of disturbance compensation further, the universal approximation theory of the fuzzy system is used to approximate the disturbance of the system. The anti-disturbance and stability precision experiments show that, the ability of disturbance rejection and the LOS stabilization accuracy of airborne platform system are obviously improved.For the demands of the disturbance compensation and the stability control for airborne platform, a kind of composite method is proposed by combining a servo control system with an isolation system. For the improvement of the ability of the system to compensate disturbances, the isolation system is utilized to suppress vibration after using the servo control system to isolate fuselage disturbance and keep stability of the airborne platform. Meanwhile, smoothing effect on the high frequency part of the vibration improves the delay of servo control system. Vibration experiments show that after the introduction of isolation system, the amplitude of the vibration is dropped about 4/5 and vibration isolation increased by about 15 d B, which suppressed the impact of vibration on the airborne platform stability.In order to improve anti-disturbance performance, dynamic performance and robustness of control structure in servo control system, a control structure which has dual rate-speed loops is presented. It using the gyroscope to constitute the inner loop, and using the optical encoder to constitute the outer loop. Theoretical analysis and experimental results show that its anti-disturbance ability is stronger and control performance is better than the structure of single rate-speed loop.For the mutual restriction between stable precision and rapid response of servo control system, a fuzzy adaptive PID hybrid control strategy with a fuzzy switching condition is put forward. The self-learning control rules and the self-adjusting factor are introduced to meet the requirements of system control in different states, and to ensure that the system dynamic response rapidly. Using the gearshift integral PID control to realize the fine adjustment, and ensure the steady-state accuracy of the system. The fuzzy switching condition based on fuzzy switching rules is given to deal with jitter caused by the threshold switching. Experimental results of dynamic performance show that the regulating time and overshoot are reduced significantly. The design of the hybrid control strategy and the introduction of the adaptive mechanism played an effective role in the response speed improvement and overshoot inhibition. Experimental results of steady-state performance show that stable accuracy and smooth movement of the proposed method are superior to conventional fuzzy control. The proposed method solves the contradiction between stability accuracy and fast smooth response effectively.