| 其他摘要 | Lunar 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. |
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