PERFORMANCE OF GIGABIT ETHERNET IN NETWORKED CONTROL SYSTEMS

Abstract

INDUSTRIAL control was traditionally based on point to point communication, where single point failures could drive the whole system into instability. With the introduction of control networks, individual machines can be interconnected to share control as well as information throughout the complete industrial line. New "intelligent" machines are based on having an intelligent control scheme to facilitate diagnostic and solve problems that may arise during operation.

In Networked Control Systems (NCS), entire machines are implemented in the form of a control network that accommodates sensors, controllers, and actuators. These are nodes communicating over the network to form automated workcells. NCS were studied in the literature when running on-top-of deterministic networks like ControlNet and DeviceNet. Also, several suggestions to use the Ethernet protocol were made ..

All E them et protocol versions r nay show non-deterministic behavior. To be• used in control systems, modifying the standard protocol to bound control packets transmission delay was discussed in previous studies.

In this study, it is shown. that with the high speeds of the new Ethernet versions, the requirements of a particular control system may be satisfied without modifying the standard protocol. Both, Fast and Gigabit Ethernet were used in star topology without modifying the IEEE 802.3 LAN protocol. Industrial models where built and systems under research by the Open DeviceNet's Vendor Association (ODY A) were tested.

OPNET simulations were run to test five industrial models. Studies were made for comparison and performance evaluation of both Fast and Gigabit Ethernet when used in NCS to satisfy real-time round-trip delay constraints. Mixed environment of control packets of deterministic nature and communication packets of non• deterministic nature was implemented.