Research On Real-time Properties Of Shared Industrial Ethernet

As the increasing development of automation and information technology, how to design unified and opening communication protocol, to build up information and control co-networks have been confronted with a challenging issue. Industrial Ethernet was a kind of net control technology, which applied Ethernet technology to industrial control systems and adjusted itself to adapt to the requirement of industrial control features. Such that characterized by simply communication protocol and opening property, and made it possible to address the problems mentioned above. As a consequence, it has been directing the development in net control technology. However, the inherent non-determination in the course of communication was the bottleneck constraining the net control applications. Therefore, determination and real-time performance have been the key problem to be solved. Faced to the severe state, this paper investigated the improvement of real-time property, by associating the industrial control feature with the communication mechanism of Ethernet.In the first place, this paper summarized the development history and current situation of industrial networks. It analyzed the non-determination reasons caused by some factors in the net control systems via studying on method to ethernet medium visiting control. Based on the analysis above, a scheduling strategy was proposed to improve the real-time performance by adding a real-time control layer between layers of data link and network.Secondly, relative real-time communication scheduling mechanism was established, and RM algorithm was eventually chosen to real-time schedule the systems through comparing three classical scheduling ones, i.e., RM, DM, and EDP. Considering the real-time communication mechanism of industrial Ethernet, a real-time scheduling table was set up. Besides, considering the compatibility with existing Ethernet, with the help of abstract environment defined by NDIS in operating system network transferring module, real-time control system has been come true by deploying the middle driver of NDIS, programming under the environment of MS Windows 2000+Visual C, and compiling with DDK2000, etc.Third, modeling, simulation and test were carried out on the OPNET platform. It proven that the real-time property of system designed according to the thought above has been enhanced at a certain extent. Finally, some future work to be done to improve performance much more was given.