Design of remote centralized monitoring system for loom status based on single chip microcomputer

1. Remote centralized monitoring system solution for loom status

    There are many parameters for the working status of looms. For the remote centralized monitoring system of loom status, its main goal is to complete the collection of the overall status data of the loom group in a remote location, provide calculation, statistics, analysis and query functions, and be able to store, browse and print various reports to provide information management services for production. Mainly including:

    (1) Monitoring of the main working parameters of the loom, such as production shift, loom number, machine speed, weft insertion rate, output, fabric variety, weaving defect type, downtime, fault cause, etc.

    (2) Analysis and processing of loom production data, such as production reports of different products at the job, workshop and enterprise levels, working efficiency of each loom, fault classification and causes, etc.

    According to this goal requirement, and because there are many working parameters when the loom is working normally, it is not necessary to centralize all the data of a single loom to the monitoring end for processing. Therefore, the remote centralized monitoring system of the loom status adopts a hierarchical monitoring method. Since the CAN bus is a network technology mainly used for various process monitoring, it is a multi-master working mode, and can transmit information in point-to-point, point-to-multipoint and global broadcast modes. The communication rate is up to 1Mbps, and the transmission distance can reach 10km. It has the advantages of extremely high reliability, good flexibility and real-time performance. Taking advantage of these advantages of the CAN bus, the CAN bus is used as a network for two-way communication of loom status information to realize remote centralized monitoring of the loom status. The structural diagram of the remote centralized monitoring system of the loom status is shown in Figure 1.

Figure 1 Schematic diagram of the remote centralized monitoring system for loom status

    As shown in Figure 1, the system consists of two parts: the single loom monitoring and management level and the host computer remote centralized monitoring and management level. The single loom monitoring and management level is mainly composed of a 32-bit single-chip microcomputer MC68336 to complete the loom working parameter setting, loom five major motion control and loom working status parameter data processing, realizing the data collection, processing and control of the working status of a single loom.

    The upper computer remote centralized monitoring management level is mainly composed of computers, CAN bus and other auxiliary external devices such as printers. The CAN bus node is composed of a single-chip microcomputer MC68332, a CAN controller, and a CAN transceiver. The CAN bus system can be easily expanded into a monitoring system for multiple loom objects.

    The working process of the system is as follows: When the system starts working, each CAN bus node MC68332, CAN controller, etc. are initialized. MC68332 receives the loom motion state parameters detected by each loom sensor for data processing, and displays some process parameters on the loom display. On the other hand, the host computer sends a command to the CAN bus to read the loom state parameters of each node. After receiving the command, MC68332 writes the main working parameters of the loom, such as loom machine number, speed, weft insertion rate, fabric type, output, downtime hours, fault cause, etc., into the sending buffer of the CAN controller according to the format specified by the CAN specification, and starts sending commands, which are transmitted to the host computer through the CAN bus for analysis and processing, realizing the reception and transmission of information on the CAN network.

2 CAN bus system node hardware design

    The CAN bus system node is the receiving and sending station of information on the network. This system uses the MC68332 microcontroller as the intelligent node of the CAN network. The CAN communication controller uses the SJAl000 type, and the CAN transceiver uses the matching 82C250 type. The CAN bus system node circuit is shown in Figure 2.

Figure 2 CAN bus system node circuit

    In order to ensure the timing synchronization between CAN and MC68332 microcontroller, CAN controller SJAl000 provides clock signal to MC68332. In actual application, CANH and CANL pins of 82C250 are connected to CAN bus through a 120Ω resistor, which can limit the impact of overcurrent on 82C250 and improve the anti-interference ability of data communication system.

    If necessary, in order to improve the anti-interference ability of the node, an optoelectronic isolation circuit can be added between the CAN controller and the CAN transceiver. Since the CAN network cannot be directly connected to the serial port of the host computer, RS232 and CAN converters are used to achieve mutual communication. [page]

3 System Software Design

    The key to system software design is the design of communication program. It mainly includes the single-chip MC68332 data acquisition and processing module program and the CAN transceiver module program. The data acquisition and processing module program is mainly completed by a single loom intelligent control system, and the CAN transceiver module program is the main part of system software design. The CAN transceiver module program control block diagram is shown in Figure 3.

Figure 3 CAN transceiver module program control block diagram

    The main task of the CAN transceiver module program is to initialize the controller, respond to the host computer's query sending program and receiving program. In order to increase the transmission speed, the node uses interruption to achieve real-time data transmission. After receiving the query command from the host computer, MC68332 will generate a corresponding interrupt and send the collected data to the host computer according to the format of the corresponding data frame. Since any node in the system can actively communicate with other nodes at any time, the communication program of each node is the same.

4 Conclusion

    Since the CAN bus has the advantages of reliability, real-time and flexibility in data communication, the remote centralized monitoring system of the loom status based on the CAN bus can obtain the actual working status of the loom in a timely, reliable and comprehensive manner. At the same time, the system is easy to expand, and the system network nodes can be expanded as needed, up to 110, which meets the scale requirements of most textile enterprises. With the help of the internal LAN of the enterprise, it is easy to form a loom working status information management and service system, and can exchange information with functional departments such as process, equipment, production and sales, which greatly improves the degree of enterprise automation and information management, and lays a certain technical foundation for the comprehensive information management of the enterprise.