Nichtlineare Bahnregelung eines geladenen Mikrotropfens
FacultiesFakultät für Ingenieurwissenschaften und Informatik
LicenseStandard (Fassung vom 01.10.2008)
Microdroplets with diameters in the range of a few microns are important for various industrial processes and atmospheric research. Characteristic properties like evaporation and condensation rates of single droplets have been studied in the current literature using almost exclusively electrodynamic levitation traps of hyperbolic geometry. Because the positioning of a charged microdroplet in these traps is very restricted, a feedback-control using a high-speed camera has been developed. The schematic set-up consists of an electrode arrangement, a camera system, a trajectory follow-up controller and a high-voltage amplifier. As conducting liquid a solution of calcium chloride, ethylene glycol, and water is dispensed. In order to position the droplet at predefined initial conditions, the injected charged microdroplet is slowed down and stabilized by a two-phase ac voltage according to conventional electrodynamic levitation traps. The information about the position of the droplet, resulting from image processing, is transferred to an external digital signal processor (DSP). To reach the desired trajectory and to allow trajectory following, a flatness based follow-up controller is implemented. For the compensation of the time delay due to image processing and to get a higher position information update rate than the approximately 10 ms of the intelligent camera system, a prediction model for the actual position is used. All significant forces, particularly the electrical force, are implied to estimate the trajectory within the tracking. Compared to conventional electrostatic or electrodynamic levitation traps, in this new approach the trajectory can be freely chosen in a two-dimensional plane. The droplet can be positioned for example for light scattering experiments without any oscillations. The set-up can also be extended in the third dimension perpendicular to the image plane and therefore a wide range of new applications for motion control of microdroplets arises.
Subject HeadingsIonenfalle [GND]
Trajectories: Mechanics [LCSH]