Field of its own

Integrated Ethernet technology claims to increase communication rates between PLCs and assembly line machines 10-fold.

An automation network technology that is claimed to increase communication rates between PLCs and their assembly line machines 10-fold is aiming to become an international industrial Ethernet standard.

Network promoter CC-Link Partner Association (CLPA) is making the technology available first to the Asian market before expanding internationally and taking on established rivals in Europe and the US.

Its product, CC-Link IE (Control and Communication Link Industrial Ethernet), the first completely integrated Ethernet with a one gigabit/sec signalling rate, can connect all levels of a manufacturing company — from the boardroom to sensors on the assembly line floor it is claimed.

The main difference between CC-Link IE and the current Asian standard CC-Link, developed by Mitsubishi Electric, is the new version uses an Ethernet physical layer. The system developers say this will make the network easier and cheaper to configure and maintain.

three technologies have the main global share of machine-control networks. Profibus or its Ethernet version Profinet, developed by Siemens, has a hold on the European market. In North America, DeviceNet is the most widely used, while CC-Link is the standard in Asia.

With the addition of this latest technology it means that all three standards have versions running on an Ethernet physical layer. ‘CC-Link IE is the only one specifically developed to use gigabit Ethernet over optical fibre,’ said CLPA general manager Stephen Jones.

He added that gigabit Ethernet is the only network fast enough to assure the best real-time machine control. Optical fibre provides sufficient bandwidth to carry signals and added benefits such as resistance to electromagnetic interference and weight reduction compared with copper wire cabling.

One of the new standard’s most distinct features is its ability to self-heal. It is based on a redundant dual loop architecture in which one node acts as a control station for the entire network. So if a cable breaks or a station is lost, the architecture will heal itself around the problem, and data will transfer in both the forward and reverse direction at undiminished speed. Also, a node failure does not interfere with communication between the remaining nodes.

The system can also carry on working after multiple network failures. With most constructions, two failures will separate the loop into two isolated segments, which makes it impossible for the control station to communicate with the nodes on the other isolated segment. Further failures would break it into multiple parts.

CC-Link IE has a way to keep nodes on the isolated segments running by assigning each one a media access control (MAC) address.

If a group of nodes loses communication with the control station, the node with the lowest MAC address on the isolated segment takes over as a sub-control station. Each station has a copy of the latest 256kB of data, so it has all the information it needs to keep the nodes in its segment operating.

The speed and redundant features of CC-Link IE make it particularly applicable where the required volume and speed of data exchange among plant floor controllers and information systems is exploding.

CLPA director Misuaki Tanaka said one example of this is the flat panel manufacturing industry where the panels are increasing in size and complexity. ‘With global competition, manufacturers realise their products need shorter time to market and CC-Link IE can help achieve that,’ he said.