Active Vibration Control For Image On Moving Vehicles

With the development of the modern military technology, the role of intelligence reconnaissance in modern wars has become more and more important. Because of the field of vision limited by view angle of optical systems, it is impossible for a fixed station to get much information. In order to solve this problem, reconnaissance systems are mounted on mobile stations, such as vehicles, airplanes, satellites and other mobile carriers, to extend the view angle of the optical systems. However, the vibration caused by mobile carriers has great influence on image quality of the optical systems. On condition that other relevant techniques are perfect, the image quality of aerial imaging mainly depends on the control of the vibration and disturbance of aerial imaging systems.Generally, passive vibration isolation is effective only when the frequency of disturbance is higher than 20-30Hz due to its limited wide band vibration isolation, so it can not meet the requirement of high isolation rate of long-focus systems. An active vibration control technology, featuring high adaptability and other potential advantages, has naturally become an important way for controlling vibrations. Optical transfer function (OTF), a tool for evaluating dynamic resolution of airborne optoelectronic systems , is proposed in this paper, by which the effect of linear movement and random vibration of a carrier on image shift is analyzed , providing theoretical basis for calculating the tolerable limit of image shift caused both by line movement and random vibration .According to quantitative analysis on the phase shift caused by angle vibration and line vibration of the carrier , it is concluded that the angle vibration has greater influence on imaging quality compared with the line vibration. Therefore, precision control should be implemented in controlling angle displacement in airborne imaging equipment, and the angle displacement of line vibration coupling imaging system of the platform bed frame should be avoided. On the basis of the image quality evaluated by OTF, a mobile carrier imaging vibration control process is provided, offering a method for designing the vibration control specifications of the airborne imaging equipment.In line with the requirements of the innovative project, piezoelectric components selected as key elements and their influence on the vibration active control system hadbeen studied. The paper also analyzes the piezoelectric components used as sensors and drivers for active control basic principle and electro-mechanical properties of the components. The main performances and feature values, as well as testing methods, and some important notes in using them are introduced.In accordance with characteristics, operating conditions of the airborne imaging equipment, a flexible vibration control model has been established, and some comparisons of feedback ways have been made, especially the system simulation and vibration experiment of absolute acceleration feedback. The max. vibration isolation of the system at 100-180Hz has reached to 10.45dB, and the experimental result of the single-axial accords well with the theoretical analysis, which shows that the feasibility and wide applications of the active vibration control in aerial imaging system.Finally, a scheme concerning the active vibration control of multiple-leg platforms and the engineering design of the active vibration control systems are briefed.