Abstract: In this paper, a method to measure the drop evaporation velocity by image feedback control system is presented. 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 per unit time. In order to determine the accurate contour of the dynamically changed drop, the contour approach principle is investigated and some numerical algorithms such as Laplace equation, Newton-Raphson method and Runge-Kutta method are introduced. Based on the drop contour determined from the contour approach, the volume and the surface area of drop could be calculated by numerical integral. The software structure and hardware structure of the system are described, an experiment result is given finally. The system is developed for the liquid experiment in SJ-10 recoverable satellite.