基于电力载波的数字式倒车影像系统

发布时间：2018-02-26 07:33

本文关键词： 倒车影像系统电力线载波 H.264编解码器数字系统车载电网　出处：《武汉工程大学》2016年硕士论文　论文类型：学位论文

【摘要】：倒车影像系统(又称倒车后视仪)是一种可视化辅助泊车系统。倒车时,它通过安装在车尾部的摄像头将车后方的道路信息显示在驾驶室内的LCD上以供驾驶者参考,大大提高了泊车安全性。目前常见的倒车影像系统其视频传输介质基本采用AV信号线或Wi-Fi无线信号。但过长的AV信号线不但会引入较多的噪声干扰,而且安装时还需打孔,既破坏了车体结构又增加了安装成本。而Wi-Fi传输虽免除了布线的烦恼,但无线信号传输的稳定性欠佳。针对以上问题,经深入分析研究,本文提出了一种基于电力线载波传输技术的数字式倒车影像系统。该系统以H.264编解码器为核心,通过OFDM载频技术和直流耦合电路将调制好的编码信号耦合到车载直流电力网络中进行传输,然后由安放在驾驶室内的接收端进行接收并解码显示。此系统不仅免除了布线的烦恼,还借助了数字信号的强抗干扰特性使信号传输更稳定,并且数字系统的扩展性好,后续还可在其上面作进一步的功能开发。本文首先对RGB与YCbCr两种色彩编码方案进行了对比,得出YCbCr可在不明显降低视觉效果的前提下能有效减少数据传输量的结论。并以此为依据,选择了能够输出YCbCr编码格式的NT99141数字摄像头作为本项目的图像采集设备。其次,根据对视频流压缩的实际需求,本项目选取了集成有片内H.264编解码器的Nuvoton N32926U1DN处理器作为设计的核心,然后绕该处理器进行了相关外围电路的设计,如:电源电路,信号耦合电路、SyncLCD接口电路、以太网接口电路等。同时,为了解决车载直流电网上的随机扰动对载波信号传输带来的干扰问题,项目中选取了可对载波子信道通信质量进行评估的型号为LW-MPA524A电力猫模块。再以设计好的硬件平台为基础,以Linux系统为核心,进行了相应编译环境的搭建与程序开发。最后在以电源箱和信号源搭建的模拟环境中对本系统进行了应用测试。测试结果表明,本系统在帧率为8~10fps的情况下画面依就能够流畅显示,满足了作为倒车影响系统对画面流畅度提出的基本要求。因此本文提出的基于电力线载波传输技术的数字式倒车影像系统设计方案切实可行,具有广阔的发展空间。
[Abstract]:The rear-view system is a visual auxiliary parking system that displays road information at the rear end of the vehicle on the LCD in the cab for the driver's reference when the vehicle is backed up by a camera installed at the rear of the vehicle. The security of parking is greatly improved. At present, the video transmission medium of the common reversing image system basically uses AV signal line or Wi-Fi wireless signal. But the long AV signal line will not only introduce more noise interference, but also need to be perforated when installed. The Wi-Fi transmission eliminates the trouble of wiring, but the stability of wireless signal transmission is not good. In this paper, a digital reversing image system based on power line carrier transmission technology is proposed, which is based on H.264 codec. Through the OFDM carrier frequency technology and the DC coupling circuit, the modulated coded signal is coupled to the on-board DC power network for transmission. Then the receiver is placed in the cab to receive and decode the display. This system not only eliminates the trouble of wiring, but also makes the signal transmission more stable with the help of the strong anti-interference characteristic of digital signal, and the digital system has good expansibility. In this paper, we compare the two color coding schemes of RGB and YCbCr. It is concluded that YCbCr can effectively reduce the amount of data transmission without obviously reducing the visual effect. Based on this, the NT99141 digital camera which can output YCbCr coding format is selected as the image acquisition equipment of this project. According to the actual demand for video stream compression, this project selects Nuvoton N32926U1DN processor integrated with on-chip H.264 codec as the core of the design, and then designs the related peripheral circuits around the processor, such as: power supply circuit. The signal coupling circuit includes Sync LCD interface circuit, Ethernet interface circuit and so on. At the same time, in order to solve the interference problem caused by random disturbance of on-board DC network to carrier signal transmission, In the project, the model that can evaluate the communication quality of carrier subchannel is LW-MPA524A electric cat module. Then, based on the designed hardware platform, the Linux system is the core. Finally, the system is tested in the simulation environment of power box and signal source. The test results show that, The system can display the picture smoothly when the frame rate is 8 ~ 10fps. It meets the basic requirements for the screen fluency of the reversing system, so the design scheme of the digital reversing image system based on the power line carrier transmission technology is feasible and has a wide development space.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U463.6

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