The design and remote monitoring system of the con

2022-07-28
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The design of the controller of the new computerized flat knitting machine and the remote monitoring system (2)

3 can bus design inside the controller

the communication design of the traditional flat knitting machine controller generally adopts direct cable connection, and each functional module is connected with a dense power supply/control wiring, which increases the complexity of user system installation, debugging and fault judgment. Aiming at the client problem, this design despises the conventional direct cable operation, and the internal communication adopts the CAN bus design

can bus is one of the most widely used field buses at present. Because of its high reliability, it can make our foundation evergreen with good real-time response, simple communication protocol and low system cost. It is suitable for the needs of high quality, low cost, multi varieties, small batch, rapid response and clean production in the textile industry. Therefore, can bus technology has been rapidly applied in the controller of textile machinery. The application of CAN bus in the control system of flat knitting machine has the following advantages:

(1) can focuses on communication. It is a computer communication network specially used in the field of industrial automation, and can effectively support the control system of flat knitting machine with real-time control operation

(2) high reliability: the data frame of CAN bus adopts short frame structure, with short data transmission time, low probability of interference in loom real-time data transmission, and short retransmission time

(3) good real-time performance: the maximum transmission rate of CAN bus can reach 1Mbps. Due to the fast data transmission speed, different parameters can be monitored, collected and fed back to the main CPU in the production process of the flat knitting machine, forming a feedback control system with strong real-time performance

(4) low requirements for communication medium: the CAN bus can meet the requirements by using twisted pair, which reduces the cost of the flat knitting machine controller using CAN bus

in order to simplify the circuit design and improve the overall performance of the system, the CAN bus control node of this design adopts can transceiver mcp255 1+ DSP (dspic33fj256mc710) with embedded can module. The DSP chip has two enhanced can modules. The enhanced can module conforms to the canl.2, can2.0a and can2.08 standards, with 8 transmit buffers, 32 receive buffers, L6 full receive filters and 3 receive mask registers. When receiving can messages, it can automatically wake up devices and automatically process remote transmission requests

4 technical innovation of controller design

(1) the whole machine adopts modular design. For different electromagnets, stepping motors and other actuators, as long as the corresponding drive modules are inserted and replaced, the control system is stable and reliable. The purpose of loom modular design is to respond to changes with less changes, to output as many products as possible with as little input as possible, and to meet various requirements with the most economical design method. The market demand of the flat knitting machine is ever-changing, and different users have different functional requirements for the flat knitting machine. Therefore, the controller of the flat knitting machine generally needs customized production, and the system configuration of the flat knitting machine with different functions is always different. Because the modules have different combinations and can be configured to generate diversified products that meet the needs of users, the modules also have standard industrial interfaces and input-output interfaces that pay attention to common protection and maintenance, and the division of modules and interface definitions conform to the actual situation of procurement, logistics, production and service in enterprise batch production, Therefore, the products configured according to the modular design mode are in line with the actual situation of mass production, so that the contradiction between customized production and mass production can be satisfactorily solved

(2) the frequency converter adopts the most advanced 180 degree control technology (i.e. sine wave drive technology). This design is based on the field oriented vector frequency conversion technology of irmcf341 microcontroller. The 120 degree control technology (i.e. square wave drive technology) commonly used in the frequency converter of traditional looms has obvious shortcomings: the motor produces a large slip when the speed and torque change, resulting in large current and low energy efficiency; The torque characteristic is poor, and the speed will be lost when the actuator load increases; The low-speed torque characteristic is poor, and the motor jitter is easy to occur. The magnetic field oriented vector frequency conversion technology can directly control the magnetic flux and torque through certain coordinate conversion, realize the double closed-loop control of current and speed, and realize fast dynamic response without large current, that is, high energy efficiency ratio: good torque performance, and sufficiently hard torque characteristics without loss of speed. This technology is more suitable for the controller of the collar and flat knitting machine, which has fast actuator

structure and high dynamic response requirements

(3) IPM (intelligent power module) symbol discrete components are introduced into the motor drive circuit, and iramxl 6up60a module, 62mm, is selected in the design × 26mm × SMM small insulated package integrates 6 high-voltage power transistors, motor drive chips and other circuits, and has protection functions such as overheating, overcurrent, undervoltage and drive dead time control, so as to ensure safe operation and reliable system. Compared with discrete components, the module not only has well-known advantages (smaller, more reliable and can be regarded as a single component), but also can avoid several common problems in the design of discrete components: the module has a very small circuit inductance, which can reduce the voltage spike, and can work at a higher switching frequency with low switching loss; The transmission delay of all low-end and high-end power tubes is matched to prevent DC current from being loaded onto the motor; Drive dead time control provides sufficient dead time to prevent short circuit of low-end and high-end power tubes; The built-in safe working circuit ensures the automatic shutdown in case of over-current and over-voltage, and there is no need to design the over-current and over-voltage protection circuit separately

5 loom group remote monitoring system based on CAN bus

there are many working parameters of the flat knitting machine, including loom needle pitch, needle type, head system structure, weaving speed, degree and mesh selection, yarn mouth configuration, winding setting and real-time control of automatic six color yarn change. For the loom group remote monitoring system, its work goal is to collect the working parameters of the loom group in different places, provide the functions of calculation, statistics, analysis and query, form various reports through data analysis, and provide information management services for the automatic production of the loom group

although there are many state parameters during the operation of the flat knitting machine, it is not necessary to collect all the data of a single loom to the monitoring host for processing, so the remote monitoring system needs to adopt distributed control. As can bus belongs to field bus, it can effectively support the communication network of distributed control. Different from the traditional control system, which can only connect point-to-point according to the control loop, can bus adopts intelligent equipment and has the functions of calculation, real-time control and high-speed communication. The communication rate can reach up to lmbps. It can complete the functions of data acquisition and analysis, real-time control, etc. on site, and send the relevant data to the monitoring host and the controller of a single loom, so as to realize the real distributed control. Its internal structure is shown in Figure 3

the monitoring system consists of the controller management level of a single loom and the remote monitoring management level of the monitoring host. The core of the controller management level of a single loom is DSP, which mainly completes the parameter setting, motion control and data processing of the flat knitting machine, and realizes the local monitoring functions such as automatic six color yarn change, automatic adjustment of degree, automatic needle bed shift, and automatic fault stop. The remote monitoring management level of the monitoring host is mainly composed of PC (upper computer), RS232/can converter, can bus and peripherals such as printer. The CAN bus node in this design is composed of can transceiver mcp2551 and DSP embedded with CAN controller

rs232/can converter is a protocol converter used to perform data exchange between CAN bus and RS232 bus of upper computer. 1 RS232 channel and 1 can channel are integrated in the converter, which can be easily embedded in the communication node of upper computer. Without changing the original hardware structure, the production of low iron and aluminum not only puts forward higher and stricter requirements for various raw materials, but also enables the upper computer to obtain can communication interface, Thus, the effective connection and data communication between the upper computer and the can network can be realized

when the monitoring system starts to work, the upper computer sends a reset command to initialize each can bus node, and six connectors shall be cut for re inspection; If one joint still fails to meet the requirements, the CAN bus node guides the actuator of the flat knitting machine to enter the working state, and then the upper computer sends an instruction to the CAN bus to read the loom state data of each node. The DSP of a single loom reads the motion state data detected by each sensor of the collar machine from time to time, and converts the state data of the stepping motor, electromagnet, density (degree) zero position plate, remote rod zero position plate, roller motor and other mechanisms into digital signals. After receiving the instructions from the upper computer, the DSP writes the relevant status data into the sending buffer according to the established can protocol requirements, and starts the sending instructions, which are fed back to the upper computer through the CAN bus. The upper computer completes the data collection, status analysis and overall control of the loom group, so as to realize the information receiving and sending of the monitoring system. At the same time, DSP will also display the process parameters on the loom display screen, so that the on-site operator can patrol and check

6 conclusion

this paper introduces a kind of computer flat knitting machine controller based on embedded system with DSP as the core. The internal communication adopts can bus design, which fully improves the reliability and real-time performance of the loom control system. Through technological innovations such as modular design, magnetic field oriented vector frequency conversion technology and intelligent power module, the market cycle is continuously shortened and the cost is gradually reduced. The statistical data show that the mean time between failures (MTBF) of the controller is as high as 40000 hours, the interrupt response time of the control system is only about 1.6 microseconds, and the cycle from the beginning of the design scheme to mass sales is only about 6 months. The monthly sales volume of controllers has remained at about 500 sets after they were listed. Some products have been exported overseas, and the annual profit has exceeded 5million yuan; For the final customers who use the controller, the innovative design has reduced the production cycle by at least 25% compared with similar domestic equipment. In addition, the loom group remote monitoring system based on CAN bus eliminates the influence of factors such as the distance between the production site and the control site and the bad production environment, and further improves the automation level of production management in textile enterprises

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