Image Servo Control using a Two-Dimensional Deflection Mirror for Sun Tracking

To evaluate the influence about the climate change and environmental pollution induced by the greenhouse gases, a Fourier Transform Infrared Spectrometer(FTIRS) instrument is used to detect the composition of the atmosphere. To track the position of the sun and reflect the sun lights into FTIRS as the background light, an image servo control system is designed to track the sun and keep the sun image in the center of the focal plane, the servo system is composed of a CMOS detector, a two-axis deflection mirror and a control unit. The detector provides the image bias on the focal plane, and the deflection mirror(DM) is driven by the voice-coil-motors(VCMs) for each axis with angular feedback measured by high resolution resolver. Due to the nonlinearity induced by the optics model of the two-axis deflection mirror, the whole control system is divided into two parts, one is the inner loop for angular position control, and another is the outer loop for image servo. Finally, the simulation and experiment results are presented to illustrate the effectiveness and performance of the proposed servo control system.