The PC Image Feedback Control System In The Drop Evaporation Experiment

The liquid experiment in space needs intelligence to deal with the surveillance image right away to obtain the characteristics of object. A method is investigated to analyze the physical feature of a drop, such as surface tension, contact angle volume and evaporation velocity through fitting contour of the drop picture.The system is constituted of 3 parts: image acquisition, image processing, and feedback control. Analyzing drop pictures from the CCD camera, the physical features of the drop could be obtained, and evaporating volume could be calculated from the geometry differences between two pictures. To maintain the drop volume, drive the injector to inject dynamically. The evaporation velocity could be calculated by the evaporating volume during unit time.From the grey picture, generally contour of a drop is obtained by Edge detection and Segmentation algorithms. Constructed the Laplace equation of the drop, made contour approach process through comparing and using Newton-Raphson method, Runge-Kutta method,coordinate rotator method and GA. With the help of contour approach, physical feature of the drop is obtained. A new algorithm which nests Newton-Raphson method with One-dimensional optimization is presented. Compared with the original algorithm raised by Rotenberg, the new one reached convergence quickly with high accuracy. It is a key technology of the special experimental system for liquid experiment in"SJ10"returns type satellite. The method is especially applicable for unmanned environment as well as non-contact measurement in the experiments.