Study of spaceborne laser imaging tracking systems and simulation

空间激光成像跟踪系统利用激光实现主动照明，利用CCD图像传感器实现目标成像，具有探测能力强、跟踪精度高、可实现凝视成像、具有目标识别能力且能够获得目标的距离信息等特点，是实现对暗黑环境下暗目标的远距离跟踪的一种首选方案。本文主要从空间激光成像跟踪系统的探测能力分析、图像跟踪处理器的设计和伺服机构的设计这三个方面对空间激光成像跟踪系统进行了初步的研究。 在系统的探测能力分析部分，利用随机信号的统计探测理论，对空间激光成像跟踪系统的作用距离进行了详尽的理论分析。首先分析了空间激光成像跟踪系统中的内部噪声和外部噪声的特性，在此基础上确定了系统的判决门限；接下来详细分析了漫反射目标的激光散射现象，分析了激光散射现象对信号特性的影响，在此基础上确定了系统的最小可探测光功率；然后详细分析了高斯光束在空间的传输方程，在此基础上得到了系统的作用距离。 在图像跟踪处理器的设计部分，主要完成了图像预处理、目标识别和目标位置提取三个方面的工作。首先，针对空间背景下的目标激光图像的特点，通过对多种图像增强技术的作用效果的对比分析，提出了“灰度值线性变换+中值滤波+Lee滤波”的组合处理方法并以之完成了目标图像的预处理。其后，通过对数值方法和几何方法的对比分析，确定了利用二值形态学方法的目标边界特征提取方案，并提出了一种以“闭运算+开运算”进行预处理的形态学边界提取方法；在利用归一化差分链码对目标的边界进行描述的基础上完成了对目标的匹配识别。最后，在对比分析了相关匹配跟踪算法和对比度跟踪算法各自特点的基础上，选用对比度跟踪算法进行目标位置的提取并对其定位精度进行了理论分析。 在伺服机构的设计部分，首先介绍了伺服系统的一般组成、性能指标和设计内容及设计步骤；然后以应用于空间交会的激光成像跟踪系统为例，进行了伺服系统的整体架构、技术要求分析和执行电机的选取，进而得到了伺服系统的原始数学模型；接下来由内而外、由稳态到动态、由模拟到数字地先后进行了视轴稳定内回路和位置跟踪外回路的设计，最后利用Matlab/Simulink对伺服系统进行了仿真。Spaceborne laser imaging tracking system use laser to realize the actively illuminate, and CCD image sensor to achieve target imaging. It has the characteristic of excellent detection capability, high tracking precision, and the capability of gaze imaging, target recognition and acquiring the information of target’s distance. So, spaceborne laser imaging tracking system is the optimal way of tracking the dark target in the distance under the dark circumstance. In this thesis, spaceborne laser imaging tracking systems is studied primarily with the aspect of the analysis of system’s detection capability, the design of image tracking processor, and the design of the servo sub-system. The first part of article is analysis of the detection capability of spaceborne laser imaging tracking systems. In this part, based on the statistical detection theory of random signal, the effectual distance of the spaceborne laser imaging tracking system is analyzed in detail. At first, the statistical characteristic of inner and outer noise of spaceborne laser imaging tracking system is analyzed and based on this, the system’s detection judge threshold is determined. Then, the statistical characteristic of laser scattered from the diffuse target and the statistical characteristic of system’s signal are analyzed in detail, and based on this, the system’s minimal detectable light power is determined. At last, the transmission equation of gauss laser in space is analyzed in detail and based on this, the effectual distance spaceborne laser imaging tracking system is acquired. The second part of article is the design of image tracking processor, and it consists of image preprocessing, target recognition and pick-up of target’s position. First, aiming at the characteristic of laser speckle image of target in space, some methods of image enhancement are tried and compared and based on it, the scheme of combination of linear transformation, median filtering and Lee filter is selected to carry out the image’s preprocess. Then, based on some methods’ comparing, morphology method is selected to pick-up the boundary of target image, and unitary difference chain codes is selected for boundary’s descriptor, and based on it, accomplishes target’s character match recognition. At last, the correlation match tracking arithmetic and contrast tracking arithmetic are compared and based on it the contrast arithmetic is selected and its orientation precision is analyzed. The third part of article is the design of servo system. At first, the common buildup, and performance parameter, and design content and process of servo system are introduced. Then, taking laser imaging tracking system applied for space rendezvous for example, the servo system’s configuration is designed, the technical need of servo system is analyzed, and the electromotor is selected , and then the original mathematic model is get. Then, from inter to outer, from stable state to dynamical state, from analog to digital, the sight axis stabilization inter-loop and position tracking outer-loop is design in turn, and then the whole servo system of laser imaging tracking system is simulated with Matlab/Simulink