Real Time Performance Analysis And Scheduling Mechanism Research Of EPA Industrial Ethernet

EPA (Ethernet for Plant Automation) is a type of fieldbus based on Chinese "863" program supported by the Ministry of science and technology of China and has been specified in IEC 61158 as type 14 and in IEC 61784-2 as the CPF14 (Communication Profile Family 14). It solves the nondeterministic problem of standard Ethernet and accomplishes real time communication by means of micro-segment topology and EPA deterministic scheduling mechanism.This dissertation analyzes the real time performance of EPA communication from theoretical and experimental perspective. On this basis, the main factors that limit EPA real time performance are given and the improvement methods of EPA deterministic scheduling mechanism are proposed. This dissertation includes the following contributions:(1) EPA real time performance theoretical model is established and its real time testing method is proposed. By analyzing EPA system model and EPA communication protocol stack, the influence models of EPA deterministic scheduling mechanism and the generating mechanism of network load in a micro-segment on the real time performance of EPA information transmission are given. On this basis, the architecture of EPA real time testing system and 7 real time indicators are presented. The testing principles and testing methods of the indicators are given respectively and the testing platform is implemented. Through the above analysis and an experiment, the key factors that limit EPA real time performance are found.(2) EPA-TSSA (EPA Time Slice Self-adaptive Adjustment) method that accomplishes the self-adaptive adjustment of data transmission time slice according to the variation of network load is proposed to improve its use efficiency. According to EPA-TSSA method, each device in a micro-segment acquires its data transmission demanding time by generating timestamps and uses it to calculate its time slice self-adaptive setting value. Then, the device announces its time slice self-adaptive setting values to the other devices in the micro-segment through adding new fields in nonperiodic data annunciation message. After receiving the time slice self-adaptive setting values from other devices, a device uses them to adjust its deterministic scheduling parameters and accomplishes the adjustment of data transmission time slice. (3) EPA-CLCS (EPA Cross Layer Cooperative Scheduling) method that can accomplish the cooperation between the control and the communication in EPA network control system is proposed. By setting alternate time slices without interruption for EPA function blocks and EPA periodic messages transmission and controlling the starting time and executing times of function blocks, the method can accomplish the cooperation between executing scheduling of EPA user layer function blocks and EPA deterministic scheduling mechanism of message transmission in data link layer to reduce the network load and optimize the deterministic scheduling parameters in EPA system, thus the real time performance and the control performance of EPA system are improved.(4) The application method of EPA industrial Ethernet in the control system of wave soldering machine is proposed. By analyzing the workflow of wave soldering machine and the functional requirements of its control system, the PEC8000 control models that support EPA communication protocol are connected to a control network to accomplish the control function in WS-350B wave soldering machine. An experiment is carried out to verify that EPA network control system is competent to implement the control of wave, temperature, spraying, electromotor and the real time communication during the operating process of wave soldering machine.The work in this dissertation provides groundwork for the improvement of EPA real time performance and a useful guideline for choosing and configuring an EPA system in industrial field.