Realization of on-line identification of coal gangue and design of multihead weigher based on embedded and fieldbus technology

Author: Smartweigh–Multihead Weighter

Foreword With the continuous development trend of embedded systems, the ARM microprocessor of the 32-bit system RISC processing chip with excellent performance, power consumption and low price shows a strong development trend. The advantages of the two provide a new transformation plan for the traditional coal preparation technology. Combining embedded system and computer interface technology, a new on-line identification of coal lumps and coal gangue and automatic multihead weigher is designed. The basic principle frame diagram of the online identification of coal lumps and coal gangue and the fully automatic multihead weigher is shown in Figure 1.

According to the regulations of coal preparation process, the software of this system mainly consists of the following three major parts: (1) Inspection part: It consists of feed bin, conveyor belt, CCD monitoring camera, image data collection power supply circuit, etc. The clean coal excavated often contains coal gangue, and the coal gangue must be selected from the conveyor belt. The CCD monitoring camera sends the coal and coal gangue images to the image data collection power supply circuit for conversion, and the converted information content is sent to the ARM microprocessor, which is transmitted to the PC according to the CAN bus Internet for resolution.

(2) Identification and manipulation part: It is composed of electronic computer, ARM microprocessor and measurement and control technology machinery and equipment. It is the key to all system software. The ash content of coal and coal gangue is calculated according to the computer vision optimization algorithm. After the ARM microprocessor identifies and distinguishes the coal gangue bricks, the operation posture is carried out. If it is identified as coal, and the operation is partially inactive, the clean coal will of course fall into the coal bunker and be transported out from the coal block safety channel.

If it is identified as coal gangue, the control data signal will be sent out, and the gate valve will be opened, so that the coal gangue will fall into the coal gangue safety channel. (3) Express sorting organization: It is composed of gate valve, raw material bucket and system software power distribution equipment, etc. According to the CAN bus Internet, automatic screening and transportation of coal and coal gangue in several safe channels are carried out. Detailed introduction of processing chip AT91M40800AT91M40800 is a processing chip with high cost performance in ATMEL's 16-bit/32-bit system microprocessor series products based on ARM7TDMI core. The key is the 32-bit system with excellent performance RISC (Reduced Intro-duction Set Computer) system architecture, and has a 16-bit (thumb) instruction system.

According to the external system bus socket (EBI) of the programmable controller, it is immediately connected to a variety of off-chip memories including FLASH. Eight priority interrupt vector control boards and on-chip field data information control boards significantly improve the real-time performance of components. characteristic. The AT91M40800 integrates the ARM7DMIARMThumbCPU core, provides 9kB on-chip SRAM, eight chip select lines, 32 programmable controller I/O ports, and an 8-bit or 16-bit system bus of the mobile phone software programmable controller. Addressable mode Indoor space 64MB, 2 USARTs, each USART has two dedicated external field data information control board safety channels, built-in programmable controller watchdog 1 timer, eight have priority, can be independent Masked space vector termination control board, 4 external interrupt manipulation memories, 4 external interrupts including a high priority, low latency interrupt request, 3 external digital clock inputs, 3 secure channel 16-bit timer/electronics counter. SJA1000 must have standardized management and information resource management because there is a certain distance between the coal yard, the coal gangue mountain and the screening production workshop.

The computer interface technology can turn the separate and decentralized precise measurement and control systems into nodes, and use the system bus as a bridge to combine them into an application system and an automatic control system that can communicate with each other and exchange information content and cooperate with each other in the daily tasks of the automatic control system. . The maximum CAN communication speed is 1Mbps, the immediate transmission distance is as far as 10km (the speed is below 8kbps), and up to 110 machines and equipment can be connected, which can perform multiple additional screening and daily tasks. SJA1000 is an independent CAN bus control board manufactured by Philips, which is used for wireless local area networks of control boards in cars and general industrial production environments. The working mode (PeliCAN mode) can be easily connected with different CPUs to form a CAN operation Internet.

The hardware configuration communication interface design scheme EPM7128 is used for the conversion and configuration of data signals between sockets. The input of EPM7128 comes from the chip selection data signal NCS2 of AT91M40800, the mobile phone charging line D0~D7, the detailed address A0~A1, the read signal NRD, the write The data signal NWE and the system software calibration data signal RST have undergone an internal logical and comprehensive solution, resulting in the action data signal required by the SJA1000. According to the regulation of the power line of each processing chip and the assignment of the port address, it can be written as the input/output logical sequence relationship of the CAN bus transceiver as follows: CAN=NCS2·A0CANALE=NCS2•A0•(NRD+NWE) CANRD=NRDCANWR=NWECANRST=NCS2+RST The detailed address port number of the selected SJA1000 is 400000H, the detailed address of the data information port number is 400001H and the calibration port address is 400002H. Because the detailed address data information of the CAN control board SJA1000 is multiplexed, the detailed address data signal on the system bus can be latched according to the falling edge of the ALE data signal.

However, the address bus and system bus of AT91M40800 are presented independently and cannot be connected to the detailed address system bus of SJA1000 immediately. Therefore, to deal with the socket problem of SJA1000 and AT91M40800, the key is how to send the data signal required for browsing SJA1000 into it. The method chosen here is to carry out the actual I/O operation in 2 times. For the first time, the detailed address value is sent to the detailed address port number 400000H as the detailed address of the SJA1000 module.

At this time, the chip selection is not selected, and the data information is latched on the AD0-AD7 system bus. When browsing the data information port number 400001H for the second time, SJA1000 is selected, and the first detailed address value is loaded into SJA1000 under the function of ALE data signal, and the CPU performs read/write actual operation on SJA1000. Calibration can be divided into system software calibration and program flow calibration.

The system software calibration data signal RST and the program flow calibration data signal carry out logical or practical operation in EPM7128, either of which can make SJA1000 reliable calibration. In order to better ensure the reliability of data communication, connect a 120Ω terminal device reflective surface resistor to each CAN bus terminal device to carry out system bus matching resistance. The TX1 pin of SJA1000 is grounded according to the 10k8 resistor, and the pulse signal of the RX1 pin must be kept above 0.9Vcc.

Otherwise, the logical pulse signal required by the CAN bus cannot be generated. If the communication distance is short and the influence of the natural environment is small, the optical protection power circuit 6N137 can be omitted. At this time, the VREF of the 82C251 can be connected to the RX1 pin immediately, thereby simplifying the power circuit. Data communication between ARM microprocessor and CAN bus AT91M40800 browses the data signals of off-chip memory and external components according to the external system bus socket (EBI). EBI applies different browsing protocols, which can complete the single cycle of external components. Time browsing, the setting of EBI in the design scheme is: (1) select 8-bit system bus; (2) select specification reading protocol; (3) select eight cycle time waiting time; (4) chip select line NCS2 The base detailed address is 400000H.

The entire program flow is written in the C language of the AT91 library, which has the advantages of strong readability, very easy to transplant, simple development and design, and convenient adjustment. Proper reset is the basis for the normal operation of the program flow. The reset of the system software is mainly the reset of the AT91M40800 microcontroller and the SJA1000 (SJA1000 working crystal oscillator circuit 16M). The reset steps are shown in Figure 3. Results The on-line identification and automatic multihead weigher of coal gangue bricks composed of AT91M40800 processing chip of ARM microprocessor and CAN bus control board SJA1000 were selected. Compared with the traditional CAN bus Internet operated by MCU, it is a novel CAN bus. operating system.

The solution system software based on the embedded operating system of ARM microprocessor and CAN bus has excellent practicability, reliability and coordination ability, which provides a new way for the outdated coal preparation technology.

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