Research On Laser Collimation Measurement Technology Of Large-scale Cable-strut Deployable Articulated Mast

With rapid development of space exploration, earth observation,military reconnaissance,marine explorationand requirement of future complicated space mission, there is an urgent need to space deployable masts of extra large scale, ultrahigh precision, ultrahigh stiffness and ultra-lightweight structure. Because of the space restriction of astronautics carrier, it requests the space stretchable arm must be folded in the cowling in the launching phase, and launches to an active status by power from its own power supply after it reaches planed orbit, which need a higher position precision after the extension. How to measure the position precisely has become a future key point on studying stretchable arms.This paper basing on the analysis of extension and folding of rope hinge stretchable arm, raised the concrete solutions for the main measuring accuracy, straight line error of rope hinge stretchable arms, and the reverse angle, horizontal and vertical displacement of crosswise frame nose after it is launched. According to the principle of laser alignment measurement, proposed the rope hinge stretchable arm laser alignment measuring plan. The straight line and position error of the stretchable arm is obtained indirectly according to the space coordinates position of the crosswise frame corresponding points, which is measured by the laser system.By analyzing the light source of the laser measurement system, according to the characteristics of the laser light source, the proper laser devices are chosen as the light source and the laser fixation is also designed. The right laser beam photoelectric detector is chosen, and the principle and performance of four-quadrant laser detector is analyzed. After analyzing the factors affecting the four-quadrant detector, some factors like the beam drifting, spot size and background light are found. According to the output signal characteristics of the four-quadrant detector, the output signal processing circuit, amplification and filter circuit of the four-quadrant detector are designed. Beyond these, a data acquisition and processing control box is made and the real-time measurement software is developed for the stretchable arm laser autocollimator system.According to the principle of the laser beam expanding, the specific methods for laser beam expanding and adjustment to verticality and alignment of the laser beam. Because of the limitation of one-dimensional calibration, a two-dimensional calibration set is designed to make plane calibration for the four-quadrant detector. The set can determine the actual displacement and corresponding voltage value of the standard fixed-point in the calibration plane. The approximate relationship of the actual voltage value is determined by the interpolation of non-calibration points in the plane, and the error which comes from the uneven character of the four-quadrant detector is also corrected. Several experiments are taken out under the laboratory condition, including the stability of laser light output, the consistency of the spot energy center, linearity of the four-quadrant detector and plane calibration experiments. The straightness and position error of the minified model machine is measured and the cause is analyzed.