Design and realization of remote sensing satellite fast-vision equipment

Design and realization of remote sensing satellite fast-vision equipment

Sun Lei , An Jianping , Bu Xiangyuan

In the field of ground source testing, remote sensing satellites need to record high-speed and continuous large-capacity of test sources in order to achieve the purpose of testing satellite sources. In some areas, such as radar signal processing, image communication, high-speed A/D data acquisition and other communications and measurement, it is often necessary to record high-speed data in real time for analysis and processing. Satellite fast-viewing equipment is to meet the requirements of satellite testing, high-speed image source data for real-time large-capacity record storage, through online and offline data analysis, to achieve the purpose of testing satellite performance. How to reliably and stably store high-speed data in real-time and send it to the computer for online or offline analysis is the key to the design and realization of satellite fast-viewing equipment system. By designing the SCSI hard disk controller, the storage and management of the hard disk will be separated from the computer, and the computer-based fast-vision device is realized, and the system performance and interface are unified in a friendly way. The test results show that the device can store the data with a total flow rate of up to 260MBps in real time, and record the time more than 900 seconds (the total recorded data is about 180GB). Through the computer to the data that is being recorded grayscale display, can monitor the running state of the source in real-time. You can also test the performance of the data source by testing the offline status of the computer online and replaying the recorded data.

1 System Design

The realization of high-speed data real-time storage is the core of this equipment development. Since the recording data is finally sent to the computer for subsequent processing, taking into account the requirements of equipment realization cost, it is an ideal choice to adopt the computer-controlled storage architecture. Multi-channel high-speed data acquisition and storage device based on computer card structure [1-2] in the existing literature, the data collection and recording of these schemes mostly adopt the structure principle of 1. In this processing mode, the external input high-speed data stream after the interface acquisition and data buffer processing, the data through the PCI bus is transferred to the computer memory, and then by the computer CPU control hard disk for data storage.

By analyzing the processing flow of data in this processing mode, we can find out the data processing rate bottleneck in this mode. Its general processing process is: Data acquisition card through the interruption to the computer to request an interruption, the CPU response is interrupted, the computer card on the buffer data received to the computer (in essence, to the computer memory); Then, under the intervention of the CPU, will need to save the data sent to the hard disk storage, Send the data you need to display to video memory for display. It should be noted that all of these operations are performed by the CPU under a specific operating system (such as Windows/unix). Because the operating system needs to manage the whole computer operation while collecting data, it is impossible to store the traffic speed in this processing mode. Therefore, the processing mode is more common in the storage and processing of data streams below 30Mbps, which is difficult to meet the requirements of storing and processing higher rate data.

At the same time, the scalability of the above-mentioned processing mode is also relatively poor. For 33m/32bit PCI bus, its maximum transfer rate is 132Mbps, and because of the limitation of computer control hard disk storage ability, even choose high-performance computer or enlarge the data buffer depth on board, can not solve the problem of rate bottleneck fundamentally.

While using the computer board to directly control the disk array for data storage operation mode, it can fundamentally solve the aforementioned data storage rate bottleneck problem. This processing mode of data flow and operating principle 2 is shown. The high-speed data stream of the external input is divided into two branches on the data acquisition and processing board, in which the data is deposited directly into the disk array by the hard disk controller, and the other data is pumped into the computer via the PCI bus. The hard disk controller here is a dedicated CPU that controls the hard drive for data access in real time. The computer can display the input data in grayscale to monitor the running state of the collected data stream. Monitoring data can be high-power data extraction, as long as the higher than 25 frames per second requirements, you can achieve a good real-time monitoring effect. This processing mode has a relatively strong system scalability. Because this mode of disk operation is not directly controlled by the computer CPU, but the use of dedicated hard disk controller card to control the hard drive for data storage. By extending the hard disk controller and the number of hard drives that come with it, you can increase the throughput rate of your system data logging.

2 System Design Implementation

2.1 System Hardware Structure

The hardware of the system mainly includes: an industrial control computer, LVDS signal Adapter Board, four pieces of high-speed data receiving processing board inserted into industrial chassis and a hard disk array consisting of eight SCSI hard disks. Each high-speed data receiving processing board connects two SCSI disks and controls the data storage for one channel.

The LVDS signal Adapter board mainly completes the physical connection of the input signal, the level conversion and the timing logic adaptation of the data processing board. The signal of the LVDS signal Adapter board output is sent to the high-speed data receiving processing board through the high-speed communication cable inside the storage device to complete the data real-time receiving and buffering, and the input data stream is divided into two ways, and the data is stored in the hard disk array by the SCSI hard disk controller on the processing board. The other data is extracted by PCI bus in real-time to the industrial computer for real-time image display. This uses the QLogic company's fas566[3] SCSI hard disk controller to complete the data access operation control of the SCSI hard disk array. The FAS566 can support up to 160Mbps data transfer speeds and can control the SCSI hard disk array to access data in Raid0[4] mode. High-speed data receiving and processing board also includes the microprocessor, data buffer, PCI bridge and other hardware modules and the corresponding software control module, the composition principle 3 is shown.

Compared to traditional IDE drives, SCSI drives have many advantages over transmission control and access speed. In the case of 10 000 rpm drives, the SCSI hard drive can achieve a continuous storage speed of approximately 35Mbps, while the IDE hard drive can only reach about 15Mbps. The SCSI drive is also much faster than the IDE hard drive, and the current Ultra320 SCSI bus data transfer rate is up to 320Mbps. In this scenario, a Ultra160 SCSI controller with a bus transfer rate of 160Mbps is selected. The use of SCSI buses and SCSI hard drives not only provides high data transfer rates, but also expands storage space by simply increasing the number of hard drives in the system, and a SCSI hard disk controller can plug and control up to 15 SCSI drives.

2.2 System software Composition

The software of this system mainly consists of driver, on-board processor real-time control module, SCSI hard disk array data storage Management module and upper user application program, etc., the system software is composed of Block diagram 4. Use Windows 2000 as the system to control the computer's operating system.

The real-time data receive and preprocessing module runs on the data Processing board and receives the data to be measured from the LVDS signal Adapter board in real time. Data storage unit control SCSI hard disk array for data storage, mainly including the SCSI hard disk array on the management of data files (establishment, deletion, modification, retrieval and maintenance, etc.) and in the image playback of image data reading and transmission operations.

Real-time data sent to the computer, mainly used to monitor the running state of the test source, so that the received data can be high-power extraction, in order to reduce the real-time transmission of data rates. After extraction, the data is transmitted to the industrial computer via PCI bus for image display.

3 System Performance Test

First, the system's single channel data logging capability is tested. The test uses a hard drive model of st318404lw[5], recording data in a non-file format, with each write buffer data of 2MB. The test results show that the maximum recording speed of the hard disk is changed, that is, the storage speed of the SCSI hard disk decreases with the increasing of record data. The recording speed of the hard disk varies with the recording time as shown in table 1.

The computer-based SCSI hard disk controller controls the disk array for data recording, which enables continuous recording of the 260Mbps high-speed data stream for a continuous recording time of more than 900 seconds. The computer can complete the gray display of the measured data stream in real time, and achieves the real-time monitoring of the recorded data. The device has been successfully used in the satellite source test, the system is stable and reliable, it can be widely used in the field of high-speed signal continuous recording.

Design and realization of remote sensing satellite fast-vision equipment