Industrial Ethernet Periodic Message Real-time Scheduling Algorithm And Its Experiment

The Industrial Ethernet (IE) is the name given to the use of the Ethernet protocol in an industrial environment, for automation and production machine control. It has the features of higher communication rate, easier communication protocol, better openness, cheaper price, etc. These characteristics enhance the feasibility to build an integration network control system. But the traditional mode of communications dispatch (CSMA/CD) is an uncertainty mode. It may result in communication delay. Thus, it is important to study the real-time network technology base on the Ethernet as the basic physical network and the real-time attemper algorithms.This thesis makes a comprehensive analysis of the existing real-time enhancement techniques. Some problems arising in the current real-time enhancement techniques can be described as follows: (1) The bandwidth utilization is low; (2) The success of information scheduling can not be predicted; (3) The dynamic change of periodic information is not supported. To solve the first two issues, this thesis build up real-time scheduling tables using rate monotonic algorithm and schedulability judgement approach. The proposed real-time scheduling algorithm (Industrial Ethernet Periodic Message Real-time Scheduling, IEPMRS) can realize lesser average delay time and higher scheduling success rate. Our algorithm substituted the time division multiple access (TDMA) strategy and made some experiments for validation. It should be noted that the proposed algorithm is limited to the problem with periodic information. The main works of the thesis are illustrated as follows:(1) Propose an algorithm of periodic message industrial Ethernet real-time scheduling (PMIERS). The PMIERS algorithm include three steps: (a) build up scheduling information set; (b) judge the ability of scheduling, e.g. preemptive judgment and non-preemptive judgment; (c) build up real-time scheduling tables for non-interruption and obstruction conditions.(2) Implement the code of IEPMRS algorithm and give a detailed description of important data structure, function performance, input and output parameters, function flow chart and design of function code which the scheduling module used.(3) Study and test the evaluation factor of scheduling success rate, average delay time base on the industrial ethernet real-time test platform of DUT Computer Control Institute. The result shows that our PMIERS algorithm has the feasibility and effectiveness for periodic message scheduling.Our algorithm has the features of higher success ratio, less average waiting delay and simple implementation. But it has limits in application range. Base on the result of experiments, it is not mature and perfect enough for industry application.