Data real-time synchronization method for PLC CANOPEN master station extension module and CPU module

Abstract

The invention provides a data real-time synchronization method for a PLC CANOPEN master station extension module and a CPU module. The method comprises the steps: a real-time task is established in a PLC and used for operating a real-time control program written by a user; a high-priority preemptive thread is established in a bottom layer system of the CPU module to serve as bottom layer implementation of a real-time task, wherein the real-time task period is the same as the synchronization period of the CANOPEN master station, after each period enters, data are written to the master station through internal bus communication, and meanwhile feedback data of the master station are read; the master station starts a hardware timer TIMER1 for measuring message deviation; the master station starts a hardware timer TIMER2 for timing a synchronous frame sending period; the master station receives the control data sent by the real-time task through the internal bus, records the count value of the TIMER1 in receiving interruption, compares the count value with the sending time of the synchronization frame to be sent, and if the count value exceeds a comparison window, compensation is carried out when the next synchronization frame is sent; then, the master station sends a synchronization frame, and sends the received control data sent by the internal bus to the slave station.

Description

technical field [0001] The invention relates to the technical field of industrial field bus communication, in particular to a method for synchronizing data between a PLC CANOPEN master station expansion module and a CPU module in real time. Background technique [0002] As the core controller of industrial control, PLC is equipped with various industrial field bus communication interfaces and communication protocols in order to meet the control and communication requirements of various equipment and sensors on the industrial site. In the industrial field communication bus, the CANOPEN protocol, as an open source and open communication bus protocol, is widely used, whether it is data acquisition or motion control, the number of slave devices supporting the CANOPEN protocol is huge, from servo drives, frequency converters to sensors, Remote distributed IO generally supports the CANOPEN protocol. [0003] The CAN port on the PLC generally adopts two forms: the CAN interface is...

AI Technical Summary

Problems solved by technology

But in occasions that require real-time control, such as motion control, the servo works in CSP or IP position mode, and the motion control algorithm runs in the user program of the CPU module. If the two cycles cannot be synchronized, the continuous position calculated by the user program will be given It must be impossible to update to the CANOPEN master station in time, resulting in duplication of the given position data sent by the CANOPEN master station to the servo

If the servo drives the motor at high speed, there will be strong vibration and shock at this time, which will seriously affect the operation of the equipment

[0005] Therefore, the PLC using the CANOPEN master station expansion module can only be used in occasions with low requirements such as collecting data with low real-time requirements or controlling frequency converters.

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