By Dean Donnelly
Dean Donnelly is the Product Marketing Manager of Industrial Networks, Woodhead Industries
Ethernet is popular in the industrial world, but pockets of automation still exist that use other networks. Because Ethernet can integrate separate communications’ networks within a manufacturing plant, however, robotics engineers are giving this protocol a closer look. Ethernet reduces installation costs, increases design and maintenance efficiency, aids diagnostic capability, and boosts overall system intelligence. In the automotive sector, for example, major robotic equipment users have begun to issued mandates for their suppliers to convert to and support Ethernet as well as traditional industrial networks. What’s more, many robot manufacturers have implemented support for Ethernet-based control.
But the transition to Ethernet from current networks, such as DeviceNet and Profibus, must be carefully managed. Many Ethernet features have not yet been fully developed and tested. Current networks are well supported and relatively inexpensive to implement. To gain user confidence and avoid major problems, the move to Ethernet must be well planned and gradually implemented so that robotic equipment suppliers, integrators, component manufacturers, and users can generate additional value.
Over the past 10 years, most man-sized robotic systems—responsible for welding, part placement, and assembly within automotive and other industries—have been moving away from proprietary network communication toward open systems that give a transparent view of information exchange within robotic operations, all the way down to the end-of-arm level.
Brad® products provide a complete line of infrastructure solutions for robotic applications.
The automotive industry has largely driven the shift to open network communications. That process began approximately 10 years ago with DeviceNet, originally developed by Rockwell Automation. Rockwell helped set up the Open DeviceNet Vendors Association (ODVA), Ann Arbor, MI, which assumed responsibility for managing the development of DeviceNet. In the same manner, Profibus from Siemens, another network popular in the automotive industry, became the responsibility of Profibus International, Karlsruhe, Germany. These were the first true open network interfaces and communication protocols. The robotics industry has widely adopted them.
BradCommunications™ SST™ interfaces provide the connection between the robot controller and the robot. The DeviceNet version also supports Quick Connect.
Most robot manufacturers use DeviceNet and Profibus in their robotic operations to control multi-channel communication with PLCs, support end-of-arm applications, and more. These protocols have been regularly updated to increase the flexibility of robots in the manufacturing process, implementing next-generation feature sets such as Quick Connect for DeviceNet.
One of the drawbacks of traditional fieldbus networks, however, is that manufacturing facilities often require multiple networks for operation. For example, typically one network controls the manufacturing cell; and one controls the robot’s interaction with the cell; and in some cases, a separate network handles peripheral products such as weld controllers.
Today, the control industry’s goal is to move to the next level—integrating robotic information networks into plantwide information networks. The vision is for Ethernet to replace discrete information networks, enabling wider peer-to-peer communications and robotics control on the plant floor. One of the benefits of Ethernet is that it can draw basic communications from discrete robotic safety networks into a standard Ethernet-based system. This application alone would dramatically reduce wiring and operating costs. Another example is the ability to streamline configuration using web browsers.
Robotics communication can be complex. In North America, most new robots operate with DeviceNet; in Europe, most run with Profibus. Many robotic applications also have two
network channels in the robot controller: one network acting as a slave to the PLC, and the other network acting as master to its own local I/O. Exchanging end-of-arm tooling frequently, precise motion control, and interfacing with supervisory software cause additional challenges.
As these needs converge, Ethernet is gaining traction. Many technicians already understand it; tools are readily available to troubleshoot it; and several built-in mechanisms make peer-to-peer data exchange seamless.
Ethernet is also being adopted in some end-of-arm or device level applications. Many robotic equipment users are asking device manufacturers—from producers of low-level proximity sensors to manufacturers of high-level vision sensing equipment—to support these Ethernet applications, which can reduce robotic system implementation costs.
However, like any major technology shift, implementing Ethernet poses significant challenges. One challenge is the management of change. DeviceNet and Profibus are defacto standards in the robotics industry, and the move to Ethernet is meeting some resistance.
Some observers argue that, from a control standpoint, Ethernet as it is applied today is not a single network. They say that protocols differ, collision and avoidance issues must still be worked out, and that divisions between Ethernet enterprise-wide operations and Ethernet process control still exist. For some observers, Ethernet raises as many questions as it answers about open control.
An example of the difficulties involved moving from discrete networks to Ethernet is the Quick Connect feature in DeviceNet. Today, more end-of-arm robotic tooling applications are changed out regularly, so one robot operates multiple tooling heads. For example, many automotive manufacturers use Quick Connect extensively because it reduces the arm count or robot count within a manufacturing facility. Quick Connect expedites end-of-arm changeouts within DeviceNet, switching components in and out of the robot in a millisecond time frame. A few robotic equipment suppliers support this optional specification.
Currently, Ethernet does not have any features that include Quick Connect. While this gap is being worked on within ODVA, it has not yet been resolved.
Also, timelines for moving to Ethernet are being extended. Four years ago, major automotive manufacturers announced a requirement for their suppliers to shift their controls infrastructure from DeviceNet to Ethernet by 2009. Some manufacturers have extended this requirement because of the availability and cost of implementing the new Ethernet-based infrastructure.
User loyalty to a system that works is also a factor. As a lead engineer in the robotics group at a major automotive facility recently told me, “I’ve been using DeviceNet for a long time because it works and it’s cheap.”
Forecasting the future
Despite these problems and concerns, the move to Ethernet will continue because of its inherent benefits. A unified system reduces costs for cabling and installation. Also, new devices
deploy factory-assembled connectors and cordsets, which further reduce installation costs.
A unified network makes documentation and programming easier to follow. With enhanced intelligence, system designers and installers have more flexibility and information to make networks more efficient. Diagnostic capability is also better with a unified system, with such features as constant querying of the network to see what parts of the system are not functioning properly.
BradControl™ IO for DeviceNet supports Quick Connect to expedite end-of-arm change outs
while the BradConnectivity™ cordsets use the Ultra-Lock™ connection system, a “push & lock” system for fast, simple and secure connections eliminating connector-related intermittent signals that lead to costly production downtime.
Robotics manufacturers are moving to Ethernet/IP, a version of Ethernet. Like DeviceNet, it is based on the Common Industrial Protocol (CIP). ODVA supports and administers both networks, as well as the CIP.
During this shift, suppliers to the robotics industry will need to pursue a dual-track approach. Many customers are already asking for delivery of hardware-based and software-based
EtherNet/IP solutions, but also want DeviceNet-compatible implementations.
Even if the move to Ethernet occurs more slowly than expected, it will most likely become a new networking standard for the robotics industry. The opportunities and benefits are too great, and customers will eventually demand it.
Woodhead Industries, Inc. Div. of Molex, Inc.
: Design World :
Using ethernet to improve safety networks
Intelligent safety networks (ISN) have multiple advantages over traditional separate control and safety networks. Combining the wiring of the control and safety networks significantly reduces
infrastructure costs. Better zone control and false trigger elimination in the safety zone decreases production downtime. Integrating of control and safety code lets production lines continue to flow in specific locations even when other areas may be shut down. Equipment and workers can work in smaller defined areas without sacrificing safety because the system is aware in real-time of the process status.
These advantages work in the real world. For example, Woodhead Industries connects safety
networks, including sensors, scanners, light curtains, and other elements. Connections made in independent safety networks can be spun into the Ethernet network, which helps consolidate wiring and reduce costs. Network diagnostic tools and products are available to help with integration. As manufacturers fold safety into one network, they can access safe messaging on Ethernet networks as well as standard data packets for control information, clearly differentiating between safety messages and non-safety messages.
Filed Under: Ethernet — cables • hubs • switches, Networks • connectivity • fieldbuses