基于ARM和线阵ccd的高速数据采集系统外文翻译资料

High–Speed Data Acquisition System Based on ARM amp; Linear-CCD

Dong Jianjun Zhao Xiaojin

Dept. Four, The First Aeronautical Technical College of the Air Force Xinyang 464000.China.

Abstract : This paper presents a high speed acquisition system of 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 the 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 system can be applied to the high speed data acquisition and operation situations from multi-channel analog signals.

Key Words : ARM; Linear CCD; Contact-line; Pantograph; Stagger –value

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 (electrified 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 .

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 pantograph 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. Pantograph-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 system 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 Companyrsquo;s high-speed linear array CCD to achieve the digitization of contact-line images (CCD output the signal of corresponding time sequence of position); (2) using Atmel Companyrsquo;s 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 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 bus width. As the real-time signal analysis and calculation require a high speed of computing, Atmel Companyrsquo;s ARM chip—AT91RM9200 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 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 diagram

III. Real-time processing and transmission of CCD digital image

In order to achieve 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 speed 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 Companyrsquo;s TCD1209D linear array CCD is used to meet the targets. Its clock pulse frequency can operate 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 diagram

Linear array CCD TCD1209D and its time sequence diagram are shown in figure 2.

B.Transmission speed between CCD and ARM processor

In order 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. Itrsquo;s a single-channel, 8-bit A/D converter, which operates over a 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 ADC080200

FIFO is used as a data buffer to co-ordinate the rate of ARM processor and ADC. 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

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