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1、河北大学工商学院装订线 本科生外文文献翻译外文题目：HighSpeed Data Acquisition System Based on ARM & Linear-CCD中文题目：基于ARM与线性CCD的高速数据采集系统 学 部 信息科学与工程学部 学科门类 工学 专 业 电子信息工程 学 号 2008480236 姓 名 倪启蒙 指导教师 王兰勋 HighSpeed Data Acquisition System Based on ARM & Linear-CCDAbstract : This paper presents a high speed acquisition system of
2、 linear-CCD based on ARM, high-speed linear-CCD and high-speed ADC are selected. As the sampling speed of A/D is slower than the working clock frequency of ARM, CPLD and FIFO are used as I/O between A/D and ARM. It makes the circuit works harmonious, simple and easy controlling, and also increases t
3、he efficiency of ARM. In order to increase the communication speed, the Universal Serial Bus (USB) technology is adopted to communicate with the PC. ARM is the key processor utilized to control the data sampling, data compute and data transfer. As a result, the whole system works effective. The syst
4、em can be applied to the high speed data acquisition and operation situations from multi-channel analog signals. I. Introduction In electrification railways, in order to extend the life of the pantograph on electric locomotives, so that the slider of pantograph wear evenly, the contact-line (electri
5、fied railway power feed line) in straight-line segments is arranged as zigzag route (curve section arranged in the form of polyline). The distance between the contact-line of positioning point and the pantograph centerline track is called out stagger-value, which is a key indicator of contact-line .
6、Stagger-value can not be ignored, the value too small will affect the slider of pantograph wear evenly and the purpose of extending using life; otherwise, in some cases (such as caught in a stiff winds), cause a large range of lateral movement of the roof (and the higher the speed, the greater panto
7、graph swing around), some parts of contact-line will be in excess of the effective work length of pantograph, so that the stagger-value of contact-line beyond the standard range, leading to deterioration of the current collection, and even cause incorrect running of the pantograph accident. Pantogra
8、ph-catenary malfunction will result in interruption of train operation, which impact on rail transport seriously. In order to avoid these phenomena, the stagger-value and its changes should be tested regularly.Therefore, a locomotive contact-line monitoring system and its mating data acquisition sys
9、tem were developed, which calculate the instant stagger-value quickly.II. System Components System hardware components are shown in figure 1. The system consists of the following components: (1) using TOSHIBA Companys high-speed linear array CCD to achieve the digitization of contact-line images (CC
10、D output the signal of corresponding time sequence of position); (2) using Atmel Companys AT91RM9200 processor of ARM9 series to realize digital signal acquisition and processing; (3) using PDIUSBD12 USB interface device to complete the data communications between measurement system and the PC. Due
11、to the characteristics of its improved Harvard structure, special instructions and quick to realize a variety of signal processing, ARM processor is widely used in image processing, communications, radar, sonar, precision machinery fields, etc. ARM processor is adopted for its arithmetic speed and b
12、us width. As the real-time signal analysis and calculation require a high speed of computing, Atmel Companys ARM chipAT91RM9200 is selected. The chip is ARM920T based, high-performance, low power consumption 16/32-bit RISC(reduced instruction set computer) microcontroller, which incorporates a rich
13、set of application peripherals and provide a single-chip solution for industrial control applications that require a wide range of peripherals at low power consumption and strictly stable working. Fig 1 System block diagramIII. Real-time processing and transmission of CCD digital image In order to a
14、chieve real-time digital image transmission, several major factors which affect real-time transmission should be necessary to solve: First, the speed of linear array CCD data acquisition; Second, the transmission speed between linear array CCD and ARM processor; the third is the data transmission sp
15、eed between ARM processor and computer. The following will be described in detail. A. Linear array CCD acquisition speed Acquisition speed is a critical performance indicator for image sensor, TOSHIBA Companys TCD1209D linear array CCD is used to meet the targets. Its clock pulse frequency can opera
16、te as high as 20MHz, especially suitable for high-speed conditions of size measurement and dynamic analysis.Fig 2 Linear CCD TCD1209D and its time sequence diagramLinear array CCD TCD1209D and its time sequence diagram are shown in figure 2. B.Transmission speed between CCD and ARM processor In orde
17、r to improve the speed of CCD data acquisition and reduce conversion time, adopting high speed A/D converter can make it exchange data with ARM processor at high-speed. ADC08200, Analog Companys nanosecond conversion device is adopted. Its a single-channel, 8-bit A/D converter, which operates over a
18、 wide range of temperature, converts fast, operates at conversion rates up to 230 MSPS, thus achieving entire signal acquisition of linear array CCD. ADC08200 is shown in figure 3.Fig 3 High-speed A/D converter ADC080200FIFO is used as a data buffer to co-ordinate the rate of ARM processor and ADC.
19、It is a two-port (input and output port) memory for temporary storage of first in first out data. Due to the time to write data to FIFO is far less than the A/D conversion time, therefore, the acquisition speed depends on the A/D conversion speed. In order to improve the speed of the entire measurem
20、ent system, the time sequence of entire circuit is precisely controlled by the CPLD to make the circuit works harmonious. CCD driving signal, integration time control, address decoding, A/D conversion control, data buffer and data acquisition logic functions integrate in the CPLD, so that the entire
21、 circuit structure is simple and reliable. In order to further enhance the system speed, when the system starts, system programs are transferred to high-speed SRAM for running and SDRAM for data storage; SRAM, SDRAM should be placed as close as possible to ARM processors, and the signal lines the sh
22、ortest possible. ARM processor (AT91RM9200), the signal processing core of the entire hardware system, read the CCD light intensity signal from FIFO, calculate the distribution of contact-line image in the CCD with corresponding algorithm, and transfer the result to the slave computer through USB. C
23、. Transmission speed between ARM processor and computer In order to increase the speed of data transmission and reduce transmission delay, USB interface is used for data transmission. USB1.1 interface support low-speed and full-speed transmission, data transfer rates has reached 1.5Mbps in low-speed
24、 mode, the transmission speed up to 12Mbps in full speed mode. Philips Companys PDIUSBD12 is adopted. When a USB device inserted into the PC, PC enumerates USB device automatically. When detecting equipment to insert, PC send query request. USB devices respond to the request and send equipment Vendo
25、r ID and Product ID; PC loads the corresponding device driver with these two ID to complete the enumeration process. PC-side USB device driver is completed by WinDriver. Data communication between PC and USB equipment mainly includes two aspects: first, read the sample data; second, send control com
26、mands to the acquisition system. IV. CCD image recognition algorithm ARM processor is mainly responsible for the solution of stagger-value; its the process of image identification, including background separation and feature extraction of the image data. Identification of the image is for image gray
27、 only; the standard deviation threshold tracking method is adopted. The image is composed of black-and-white texture, and gray-scale varies greatly, with a larger standard deviation; and background gray distribution is relatively flat, with small standard deviation. Therefore, the standard deviation
28、 of each point as the center of a group of pixels is calculated, the value greater than a certain threshold determine the point in the foreground, or as the background. This system not only measures the contact-line instant position, but also calculates the abrasion state of the contact-line to eval
29、uate its life span. System support by associated PC software, through subsequent playback of the data collected, to check the situation of stagger-value, as well as the abrasion of contact-line, and decide whether to adjust and replace or notV. Measures of improving system reliability High-speed dat
30、a acquisition system is inevitably affected by interference from the external environment. As the complex environment around the measurement system, many factors interfere with the system. Electromagnetic interference around 27.5KV high-voltage catenary affects great; the pantograph detaching will b
31、e accompanied by the emergence of arc sparks, this phenomenon interfere with communication line along the lines, accompanied by high-frequency electromagnetic waves, therefore, necessary anti-interference measures should be taken.In order to improve the ability of anti-interference, anti-jamming mea
32、sures taken are as follows: take anti-interference design of PCB circuit to reduce the external interference on system; all cables adopt shielded cable with wave-proof sleeve; equipment shell adopts shielding material and detection window of the shell use gauze to isolate the interference. 基于ARM与线性C
33、CD的高速数据采集系统摘要：本文介绍了一个基于ARM的线性CCD高速采集系统，系统中选择了高速线性CCD和高速ADC。因为ADC的采样速度相对ARM的工作时钟频率较慢，所以使用CPLD和FIFO作为A/D和ARM之间的I/O接口。它使电路工作在更加平稳、简洁而易于控制，同时也提高了ARM的工作效率。为了提高通信速度，这里采用通用串行总线（USB）技术来与PC进行通信。 ARM是用来控制主处理器的数据采集，数据的计算和数据传输。结果证明，整个系统能高效运作。该系统可应用于高速数据采集及多路模拟信号的工作环境下。1 引言在电气化铁路，为了扩大对电力机车受电弓的寿命，所以要使受电弓滑块磨损均匀，接触
34、线的直线段（电气化铁路供电线）排列为曲折路线（弯段被安排成折线的形式）。之间的接触线的定位点和受电弓轨道中心线距离称为错开值，这是一种接触线的关键指标。错开值是不可忽视的，这个值过小会影响到受电弓滑块磨损的均匀性，从而影响到延长使用寿命的目的，然而，在某些情况下（比如陷入了激烈的风中），造成大范围的在屋部的横向运动（并且速度越快，受电弓的左右摆动越剧烈），接触线将在某些部分将会超过受电弓的有效工作长度，从而使错开，接触线值超出标准范围的错开值，导致了当前连接的破坏，甚至导致了会产生受电弓事故的错误运行。受电弓与滑触线发生故障，将导致列车正常运行的中断，从而对铁路运输产生严重的影响。为了避免这些
35、情况，错开值及其变化应经常性地予以测试。因此，一个机车的接触线式在线监测系统，及与其配套的数据采集系统被开发出来，它的工作是实时地、迅速地计算错开值。2 系统组件系统硬件组成如图1所示。该系统由下列部分组成：（1）采用东芝公司的高速线阵CCD实现接触线影像的数字化（CCD输出对应的时间序列位置的信号），（2）采用Atmel公司ARM9系列处理器中的AT91RM9200，实现了数字信号的采集和处理；（3）采用PDIUSBD12的USB接口设备，完成测量系统与PC机之间的数据通讯。由于它改进型的哈佛结构，特殊的指令系统以及迅速实现各种信号处理的特点，ARM处理器被广泛应用于图像处理，通信，雷达，声
36、纳，精密机械等领域。ARM处理器正因其算术速度和总线宽度而被采用。随着实时信号分析和计算都需要很快运算速度，所以系统选择了ATMEL公司的ARM芯片AT91RM9200。该芯片是基于ARM920T的，高性能，低功耗的16/32位RISC（精简指令集计算机）微控制器，它集成了一套丰富的外围设备的应用，并在那些需要一大批外围设备，并能在低功耗的外设和严格稳定工作的工业控制应用中，提供了一个单芯片的解决方案。图1 系统硬件组成3 CCD数字图像的实时处理与传输为了实现实时的数字图像的传输，几大影响实时传输的因素应该予以解决：第一，线阵CCD的数据采集速度；二是线阵CCD和ARM处理器之间的传输速度；
37、第三是ARM处理器和计算机之间的数据传输速度。下面将给以详细描述。A. 线阵CCD的采集速度采集速度对于图像传感器来说，是一个关键的性能指标，这里采用东芝公司的TCD1209D线阵CCD来满足目标要求。它可工作在可高达20MHz的时钟脉冲频率下，所以对高速条件下的尺寸测量和动态分析特别适合。图2 TCD1209D及它的时序线阵CCD TCD1209D，以及它的时序图如图2所示。B.CCD和ARM处理器之间的传输速度为了提高CCD的数据采集速度，减少转换时间，现使用高速A/D转换器，以使它在高速环境下与ARM处理器进行数据交换。这里选择ADC08200，Analog公司的一个纳秒级转换器。这是一
38、个单通道，8位的A/D转换器，它可以在一较宽的温度范围内工作，转换速度快，工作时的转换速率高达230 MSPS，从而实现整个线阵CCD的信号采集。ADC08200如图3所示。图3 ADC08200FIFO用于作为数据缓冲区，协调了ARM处理器和ADC的速率。这是一个两端口（输入和输出端口）的，临时性存储的，先入先出的数据存储器。由于向FIFO中写入数据的时间远远小于A/D转换的时间，因此，数据采集的速度取决于A/D转换的速度。为了提高整个测量系统的速率，整个电路的时序是由CPLD的精确控制，以使电路协调地工作。 CCD驱动信号，积分时间控制，地址译码，A/D转换控制，数据缓冲和数据采集逻辑功能
39、都集成在CPLD上，使得整个电路结构简单，功能可靠。为了进一步提高系统的速度，当系统启动时，系统程序被传送到高速SRAM去运行，并且使用高速SRAM来存储数据；SRAM，SDRAM应尽量靠近ARM处理器放置，而信号线应尽可能地最短。ARM处理器（AT91RM9200）作为整个硬件系统的信号处理内核，需要读取存储在FIFO中的CCD光强信号，应用相应的算法计算CCD中接触线图像的分布，并通过USB把结果传送给从属计算机。C.ARM处理器和计算机之间的传输速度为了提高数据传输速度，减少传输延迟，USB接口用于数据传输。 USB1.1接口支持低速和全速传输，数据传输速率在低速模式下已经达到了1.5M
40、bps，全速模式下传输速率可达12Mbps。这里采用飞利浦公司的PDIUSBD12。当一个USB设备插入到PC，PC机会自动枚举USB设备。当检测设备插入时，电脑发送查询请求。 USB设备便响应请求并发送设备供应商的ID和产品的ID；电脑根据这两个ID加载相应的设备驱动程序以完成枚举过程。PC端的USB设备驱动程序由WinDriver完成编写。 PC与USB设备之间的数据通信主要包括两个方面：首先，阅读样本数据；第二，发送控制命令到数据采集系统。4 CCD图像识别算法ARM处理器主要负责错开值的解决；这是个图像识别的过程，包括背景的分离和图像数据中特征的提取。图像识别只在于图像的灰度；这里采用
41、标准差阈值法进行跟踪。该图像是由黑色和白色纹理组成的，并且灰度变化较大，有很大的标准偏差；还有背景灰度分布较为平滑，有较小的标准偏差。因此，把每个点作为它那一组像素点的中心，计算出它的标准偏差，得出值超过一定的阈值的点确定为前台点，或作为背景。该系统不仅是测量接触线的即时位置，还计算了接触线的磨损程度，以评估它的使用寿命。通过随后对采集到数据的回放，相关的PC软件支持着系统来检查错开值的情况，以及接触线磨损，并且决定是否予以调整和更换。5 提高系统可靠性的措施高速数据采集系统会不可避免地受到外部环境的干扰。由于测量系统周围复杂的环境，许多因素会干扰到系统。27.5KV的高压滑触线周围的电磁干扰所产生的影响很大；受电弓的分离将带来电弧火花，这种现象会干扰通讯线路沿线的高频电磁波，因此，需要采取一些必要的抗干扰措施。为了提高抗干扰能力，这里采用的抗干扰措施如下：采取抗干扰的PCB电路设计，以减少系统的外部干扰；所有电缆都采用带有波防套的防护型电缆；设备的外壳采用屏蔽性材料和用于检测的窗口，这些外壳使用纱布来隔离干扰。
