Benefits of using open source Linux
The main advantage of using open source is reduction in costs and making use of tried and tested systems. The machine builder can install Linux as an operating system and to have the real time capabilities can use the RT PREEMPT patch for Linux. This will ensure the deterministic operation needed on the field level. Thus the machine builder can scale down the PC and still achieve a higher machine performance. Like other operating systems Linux offers the users to have different application running and thanks to the RT PREEMPT patch it provides a real time deterministic behavior for the field level communication. B&R Automation system is an example using Linux as an operating system in machines as well as processes. APROL which is the DCS solution from B&R operates completely on open source Linux.
Ethernet POWERLINK: Network the key differentiator
Once Linux is in place on the PCs the machine builder needs to gather data from the field devices like encoders, IOs, pneumatic valves, drives etc. This is done using a network. Ask any machine builder the network demands are very stringent in automation and needs a perfectly deterministic performance. In motion application this determinism and real time communication needs go down to as low as 200µs and in process it could be even a few milliseconds. Topology also plays an important role in the machine and process. In many instances high availability is of keen importance.
Looking at all the above aspects Ethernet POWERLINK has the perfect blend of all the features coupled with the having the source code open source. It is the only protocol which provides the master and slave source codes free of cost. The protocol also provides high availability and redundancy features in the open source stack. On both the master and slave devices it functions on standard Ethernet and complies with the IEEE802.3 standards. The protocol is completely hardware and operating system independent. The stack is maintained on the website by the Ethernet POWERLINK standardization Group which is a consortium of over 3200 members and users.
The machine builder can thus implement the master solution on the Linux PC and achieve the deterministic performance on the field. The machine builder has the option of using the field devices compliant with POWERLINK communication with off-the-shelf components from various companies. A huge list of device manufacturers is available at http://www.etherent-powerlink.org. With this configuration the machine builder can easily achieve cycle times as low as 200µs. A redundant master solution can also be implemented by having two masters in the network to avail high availability. The complete details of the protocol for any platform and operating system implementation are readily available here.
A video of the a position control demo using FPGA and ARM controllers controlled by an open source Linux based PC is available here
openSAFETY: Safety no longer a limitation
Safety is of utmost importance in machine as well as process industries. To make the machine safety compliant needs effort and certifications. We try to make the life of machine builders easy by providing a TUV certified stack complying with the IEC 61508 standards. The machine builder thus gets a networked safety solution. Networked safety has not only improved the cooperation between humans and robots but also reduced development time, reduced wiring, eliminated setup errors, improved maintenance, and added intelligent features. This has facilitated robots to no longer be restricted by cages. Similar to communication networks, most safe networks are proprietary and limited to certain fieldbuses and they are not compatible with each other. Thus connecting all machines on a shop floor would have been a distant dream. But thanks to openSAFETY which is fully open and totally fieldbus independent safety protocol makes lives of millions of plant operators and machine builders very easy. It is SIL 3 certified standard and available for all industries.
OPC UA: Field to MES/ERP connectivity
POWERLINK and openSAFETY enable to machine builder to gather data from the field in a deterministic and same method. On a shop floor there could be requirements for the controllers from different machines to exchange data or a central PC working as SCADA would require the data for sending it to the ERP and MES. The machine builders could use OPC UA which is another open source protocol based on standard Ethernet for transferring the data. Being based on standard Ethernet, POWERLINK effectively mergers well with OPC UA and facilitates seamless data transfer from the shop floor to the MES/SAP. OPC UA is already playing a central role in the IT related areas of modern production systems. An OPC UA server and OPC UA client are now available directly on Linux-based runtime servers to allow open, vendor-independent communication. Motor management and control units, compact OPC controllers and other devices can directly exchange all important operating, service and diagnostic data with the OPC UA client. OPC UA is standardized in accordance with IEC 62541 and offers easy-to-use functions for vendor-independent data exchange. This makes it easy for software developers to engineer complex systems with high data communication demands. Implementing flexible and modular automation solutions more easily is the result.
No vendor lock-ins
With the usage of open platforms the machine builder can be free from licensing and copyrights. He gains an edge over his competition as he offers the customer a flexible, high performance and on top of all a cost effective solution. Usage of the open platforms helps him to avoid vendor lock-ins. The machine builder is able to provide a complete solution from field to the board over a standard networks.