We’ve all been there – a call comes in on your mobile phone while you’re transitioning from a digital to an analog zone, and you can only hear half of the caller’s words. Think about this frustration and you’ll be able to understand the plight of the plant floor engineer who has inherited a diverse collection of new and old equipment, all communicating over an equally diverse collection of open and proprietary network protocols.
Although technology continually improves, the ability to quickly transmit a message between two points without disruption is often more difficult than it seems. With cell phones, interferences such as differing standards, physical obstructions, and older technologies result in dropped calls, bad connections, and poor communication. For the plant floor engineer, communication issues may stem from data transport across noncompatible networks, proprietary network integration and, of course, the garden-variety loose wire. Each can make communication between devices difficult, limiting data sharing and constraining manufacturers’ efforts to optimize plant floor systems.
Seamless communication in the past was near-impossible, because no single network was able to integrate safety and standard control systems, while also enabling the seamless transport of data across multiple plant floor physical networks. That has changed with emergence of new standards like the Common Industrial Protocol (CIP). CIP is an application protocol for industrial networking that is independent of the physical network. The CIP protocol, available on DeviceNet, ControlNet, and EtherNet/IP, provides a set of common services for control, configuration, collection, and sharing across all of the CIP networks.
Evolution of CIP
CIP encompasses the data-addressing method and the message-exchange rules for every data packet sent over a network. When CIP was first developed, users were excited about the ability to transfer data across device-, control-, and information-level networks. This ability eliminated the need to install expensive and difficult-to-maintain “store and forward” gateways between each network. CIP networks such as DeviceNet, ControlNet, and EtherNet/IP share a common application layer for fast data transmission across devices and networks. Engineers can communicate with systems on the plant floor or in IT, with consistent and accurate data flow. CIP builds in a standard set of services for control, configuration, and data collection that include:
- media independence;
- fully defined device profiles;
- control services;
- multiple data exchange options;
- seamless, multi-hop routing;
- unscheduled and scheduled communication; and
- producer and consumer services.
CIP Safety
CIP Safety greatly improves integration between standard and safety control functions, increasing the visibility of safety across the entire system. In the past, a safety event in one section of a machine could result in the entire machine shutting down because the standard system had limited knowledge of the safety event. CIP Safety allows the control and safety systems to coexist on the same network and to share data between the safety and standard applications. This enables engineers, for example, to perform “zone control,” where one zone of the machine is brought to a safe state while other zones continue to operate. CIP Safety also enables easy integration of the operator interface with the safety system, giving operator and maintenance personnel visibility to machine safety events and providing them the knowledge to rapidly respond to and recover machine production. This enables manufacturers to maximize production by synchronizing the safe and standard functions of their equipment.
CIP Safety: Above and Beyond
Bridging and routing is an important feature for CIP Safety because it enables seamless communication of both safety and standard data across multiple and potentially different physical networks. This feature removes the engineering need for message path routing and data translation, enabling the data to flow openly between networks and devices with minimal effort on the system engineer’s part. Seamless communication enables manufacturers to perform monitoring and data collection of both their standard and safety systems from any location in the facility that has authorization to view such data.
For instance, EtherNet/IP could be serving as a control network for safety and standard I/O, as a peer-to-peer network for data sharing between PLC systems, as a data transmission network for IT applications, and as a data acquisition network for operator interface systems. Using the seamless bridging and routing capability of CIP Safety, a Safety PLC on EtherNet/IP could also be directly controlling I/O on a DeviceNet subnet via an EtherNet/IP to DeviceNet bridge. Information technology applications, such as manufacturing execution systems (MES) or Change Management systems, could read the status of the safety PLCs and safety I/O modules on either of these networks. Likewise, the operator interface system can seamlessly retrieve data from the safety PLC or safety I/O devices on DeviceNet and EtherNet/IP. All of these data transactions are able to move freely between both networks using the CIP protocol. This greatly reduces system complexity, reduces engineering and maintenance costs, and enables the easy flow of information across all plant floor communication layers.
One reason safety networks have traditionally been isolated on the control floor is because the safety devices and controllers may need to react at different speeds than their standard counterparts. Historically, using a single network to accommodate both safety and standard systems proved problematic, because the larger a network grew the more the performance speed decreased. However, with CIP Safety, each node’s network update rate can be set at a different speed. This allows each device to perform at a rate that is best optimized to its safety function, ensuring efficient allocation of network bandwidth.
Who Benefits from CIP Safety?
Before the development of safety networks such as CIP Safety, a safety application’s scope was limited because of the difficulties in linking multiple safety functions into a comprehensive and cohesive system. Safety application engineers often had to reduce the size of their systems or minimize their performance requirements since it was difficult to hardwire interlocks and relay-based safety logic into a complete automation system.
Now, engineers can integrate their devices on common physical network segments and allow safety and standard information to flow as needed between devices and controllers. Case in point: International Automation, a retrofitter of stamping machines based in Canada, was able to reduce installation time by 65% and increase production efficiency by 50% by implementing CIP Safety into their tandem lines.
Implementing the Allen-Bradley® GuardLogix™ controller from Rockwell Automation in its machines, International Automation combined the flexibility and high performance of the Logix platform with integrated safety control features. This allowed the company to reduce programming time, since programming a standard system, along with safety components, took anywhere from two to three weeks. The ease of use provided by RSLogix 5000 and GuardLogix enabled International Automation to write the program for the new safety control system in eight hours. Because of the seamless communication between the safety and standard devices, users do not need to learn numerous protocols and programs. CIP Safety helped International Automation simplify their programming, helping reduce startup costs as well as improve production.
For companies like International Automation who seek to maintain a competitive edge in their industry, an open network like CIP Safety provides the opportunity to improve overall production efficiency, from lower startup costs to higher quality, from faster installation times to the use of different, but compatible, networks on the same system.
The Future of CIP Safety
Since the release of the conformance test through ODVA in January 2005, the CIP Safety network has already improved integration among controllers, devices, and networks. The future of CIP Safety promises to be bright as more automation suppliers continue to develop products that support integration between safety and standard controllers, devices, and networks.
With transparent bridging and routing, the ability to tune devices at different performance rates, and the integration of standard and safety networks, CIP Safety allows the plant floor to communicate seamlessly through different networks. Because of the integration of safety and standard control systems, programming is less complex, reducing training time and startup costs.
CIP Safety was designed and certified to function on any CIP-based network. The CIP Safety protocol meets the requirements of IEC 61508 up to Safety Integrity Level 3 (SIL3) and EN 954-1 Category 4 (Cat4) and has been certified by TUV Rheinland. For example, CIP Safety messages today can be bridged between DeviceNet and EtherNet/IP subnets.
Released in April 2006, the CIP Safety Protocol for EtherNet/IP enables automation suppliers to develop safety controllers, safety I/O, and safety devices that communicate directly on EtherNet/IP. Initial safety products on EtherNet/IP are available in the market starting in mid-2007, allowing manufacturers to choose the physical layer and network attributes that best apply to their application. For instance, if the user desires to power the sensors directly over the network, thereby reducing power distribution and wiring complexity, then CIP Safety over DeviceNet will best suit those needs.
If the user requires large message packets distributed over a great distance or wants a single network for control, operator interface, and IT integration, then CIP Safety over EtherNet/IP may best suit those needs. In both cases, the network protocol is common and appropriate information can be easily shared throughout the enterprise.
