The basic research of criss-cross rotatable varifocal mechanism

With aircrafts´ growing need for Autonomy of the navigation systems, Inertia/image matching assistant navigation system, as one of the most suitable systems in the country, has received increasing requirements for application. Traditional varifocal mechanisms in navigation system, however, have shortages like comparatively long zooming time, large occupation of room, low control accuracy, and as a result which can not meet requirements of image matching efficiency and quality of the images to get. In order to compensate for the shortcomings above, a new-type criss-cross rotatable varifocal mechanism driven by Ultrasonic Motor was developed after the design on mechanical structure and driven source. In the mechanical structural design, criss-cross rotatable structure is to fix two and more sets of variable lens for various resolution images. On the choice of the driving source, Ultrasonic Motor was applied in the mechanism, to realize zoom function with high accuracy through closed loop control system. The experiment suggested when the load generated 0.32N.m torque, and criss-cross rotatable varifocal mechanism drives two sets of lens to switch, shaking error of axis´ stability and accuracy is less than 0.1°, and varifocal mechanism´s starting was 11.28ms, and shutoff was 9.17ms; the time running for half cycle was 450.25ms and the experimental data were all in half a minute as to meet the requirements for the following image matching.