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基于RTAI扩展源波前倾斜量实时补偿相关跟踪系统的研究
杨靖文
Subtype硕士
Thesis Advisor熊耀恒 ; 饶长辉
2010-05-31
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天体测量与天体力学
Keyword月球激光测距 自适应光学 Rtai Pci-e 实时补偿
Abstract月球激光测距是通过激光对地月距离进行的科学测量,代表着测距技术和探测技术的顶峰。 本论文主要是设计并实现了一种基于RTAI实时操作系统的相关跟踪系统,目的在于实时补偿扩展源目标波前倾斜畸变,增加月球激光测距的回波光子数,提高激光测距成功的几率。 月球激光测距是选取具有一定地理特征的月球表面,它属于低对比度扩展源目标,这一点跟点源目标有很大区别,直接造成计算量的大幅度增加,此为本系统设计中的难点之一;另外,具有统计性质的大气湍流的无规则运动频率较高,通常可达到几百赫兹,而相关跟踪系统的响应时间要求小于波前倾斜量变化的时间尺度。因此本论文要实现的目标是在大气湍流的冻结时间(2~5ms)内完成实时探测和实时补偿,也只有这样,大气波前倾斜量的实时补偿才是有效的。此为月球激光测距中相关跟踪系统实现的难点之二。 本相关跟踪系统引入倾斜校正自适应光学技术到月球激光测距中,根据倾斜校正自适应光学的相关跟踪原理,创新的设计了一种基于实时操作系统RTAI(Real-Time Application Interface)的相关跟踪处理机。该相关跟踪处理机基于Linux的硬实时扩展接口RTAI,采用绝对差分算法,使用通用CPU,并且创造性的引入汇编语言优化反复大量的实时计算,对实时计算速度带来了一个数量级的提高。同时为给高速计算提供实时数据来源,相关跟踪系统中独具创意的设计了基于PCI-Express接口的高速图像采集卡及在硬实时操作系统驱动程序,完成高速数据采集任务。本论文详细介绍了整个相关跟踪系统的结构以及系统各部分环节的软硬件设计,给出了PCI-Express高速图像采集卡设计结果及其RTAI实时驱动程序、相关跟踪处理机软件设计结果。最终相关跟踪系统实现闭环,它保证了较高的图像传输速度,最大限度的减小相关跟踪系统系统的延迟,提高系统响应带宽的目标,最终实现了图像数据的实时传输(≤28μs)及波前倾斜量的实时补偿(≤348μs)。相关跟踪的处理帧频远大于为1 KHZ,满足大气湍流的特征频率,能够胜任月球激光测距中大气波前倾斜量的实时补偿任务。 本论文是国内首例用于月球激光测距的相关跟踪系统,而采取的设计方式是以对通用计算机底层硬件直接写程序的方式,实现了其高帧频的系统带宽要求,在国内尚属先进。相对于同类设计更有集成度高,升级性能强,扩展性能好的特点。
Other AbstractLunar Laser Ranging is a scientific measurement on the Earth-Moon distance through the laser, representing the peak of Range Measurement and Detection technology. The goal of this thesis is to design a correlation tracking system based on real-time operating system RTAI . The aim of the system is to compensated the distortion of wavefront tilt of the extended sources on real-time, to increase returned photon numbers for the lunar laser ranging and to increase the successful probability of the lunar laserranging Lunar laser ranging generally select a certain geographical features of the lunar surface, it is low contrast extended source targets, it is very different from the point source, result in the substantial increase of computation, This is one of the difficulties in system design. In addition, the frequency of atmospheric turbulence which is non-regular exercises with statistical properties is very high, usually up to several hundreds frames per second. The correlation tracking system’s response time must less than the time that the wave-front tilt is changed.The system require a high control bandwidth to correct the atmospheric turbulence which changed rapidly, so the goal of design is to complete real-time detection and real-time compensation in the atmospheric turbulence freeze time (2ms to 5ms), only then, the real-time compensation of atmospheric wavefront tilt is effective.This is the second difficulty in achieving correlation tracking system of the lunar laser ranging. To meeting its large computational difficulties and high real-time requirements, the correlation tracking system is introduced tilt-correction adaptive optical system to the Lunar Laser Ranging. According to principle of the correlation tracking algorithm for tilt-correction adaptive optical system, we innovativly design a kind of based on real-time operating system RTAI. This correlation tracking processor based on Linux’s hard Real-Time Application Interface RTAI ,adopted the absolute difference algorithm, used the general CPU, and creatively introducted assembly language optimizing a large number of repeated real-time computing, it created an magnitude improvement the speed of real-time computing.At the same time , to provide the real-time data collection for the high speed computing, this thesis design high-speed image acquisition card based on PCI-Express and the hard real-time operating system drivers with the unique creativity, to complete the assignment of high-speed data collection. After analyzing the structure of the correlation tracking system and the hardware and software designs of the various parts of the whole system , this thesis presented the designs of high—speed image acquisition system based on PCI-Express and it’s RTAI real_time driver, the results of correlation tracking processor software designs. The correlation tracking system eventually implemented closed loop, it ensures a high image transmission speed , the minimum delay of the correlation tracking system, and improves the response bandwidth of the whole system. Ultimately,it implemented real-time transmission of image data (≤ 28μs) and the real-time compensation of wavefront tilt (≤ 348μs). This system is able to compute 1K frames per second with the correlation tracking algorithm. It meets the characteristic frequency of the atmospheric turbulence, and is competent for the real-time compensation of atmospheric wavefront tilt in the lunar laser ranging. This thesis is the first case of correlation tracking systems in the lunar laser ranging. It adopted the design approach which is directly writed programs to the general-purpose computer’s underlying hardware to achieve its high frame rate requirements of the system bandwidth. It is still advanced in China. Compared with the same design, it has more advantages, such as high integration, strong capability of upgrade and great capability of extend.
Subject Area天文学
Pages75
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/7355
Collection应用天文研究组
Recommended Citation
GB/T 7714
杨靖文. 基于RTAI扩展源波前倾斜量实时补偿相关跟踪系统的研究[D]. 北京. 中国科学院研究生院(云南天文台),2010.
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