PLC ladder logic code in minutes

Tom Shelley reports on PLC developments poised to further radically advance manufacturing and reduce times to market

Tom Shelley reports on PLC developments poised to further radically advance manufacturing and reduce times to market Researchers in the Warwick Manufacturing Group have been studying the automatic generation of reliable PLC code with its own built-in diagnostics. It can in some cases reduce programming tasks normally requiring two and a half days work to five minutes. Although still in the development stage, it shows the way forward for automation technology, and is just one of the developments recently revealed which show how much life there still is in the PLC as opposed to the PC. The technology for automatic PLC code generation was revealed by Dr Ken Young, a reader in the Warwick Manufacturing Group, speaking at the "Rockwell Automation University" seminar recently held at the NEC. System suppliers and integrators are under constant pressure to cut costs and improve reliability, no small matter when the typical cost of a hold up in a car production plant is around £18,000 per minute. The problem is exacerbated by the need for more frequent line changes to keep abreast of changing market demands, and maintenance by smaller numbers of staff, often working remotely. Dr Young said that what is needed are modules of pre-tested code that can be called up, each with its own diagnostics, links to higher level systems and built-in security. To this end, his team has been working with a Rockwell prototype that can automatically generate standard ladder logic code, in Dr Young's words, "To see how effective it is and what the issues are with it." Dedicated software engineers will often say that ladder logic was long ago surpassed by easier to use and more versatile methods of programming. However, it is still very widely used, especially by the automotive industries, and there are many programmers available who can interface with it and add their own code to extend system capabilities. What is presently available is limited by being applicable to only a single PLC, requiring manual allocation of I/O, and with 'limited' communications between modules. Automatic code generation is not a new concept of course. CAM programs have been coughing out reliable, automatically generated CNC code for more than 20 years. However the barriers to automatic PLC code generation seem to be mainly inertial - persuading PLC companies to invest serious money to go down this route, and overcoming what Dr Young described as "A lack of trust" in the concept. He also said that another barrier to implementing any kind of major change is that, "The government keeps pushing the lean message to the point that companies have taken out anybody who is not adding added value today, as opposed to tomorrow. This particularly applies to R&D. We are perhaps in a worse case in the UK than elsewhere." On the hardware front, Dr Young thinks that manufacturers should go more for fault tolerant hardware which has sufficient processing resource to be able re-allocate it in the event of faults being encountered. Factory networks too, should be made self optimising and self repairing. All these technologies are, of course, already available, if not generally used in factory automation. Controllers for safety critical systems, such as those used in civil aircraft, have to have dual if not triple redundancy and the supreme example of a network that self optimises and re-routes itself round blockages is the Internet, which goes right back to its birth as an originally military communications system. Rockwell, is incidentally, promoting Industrial EtherNet/IP as a communications standard. Rather than hang everything off a single bus, the company advocates connecting islands of units to Cisco and N-Tron switches, which are then connected to each other. This reduces the possibility of congestion and should ensure that in the event of a break, only part of the system should go down. There was quite a lot of concern expressed at the meeting about security. Jan Roschek of Cisco told us that there were between 100 and 500 unreported cyber attacks on process and control systems every year, and that 50% resulted in financial losses of more than $1 million each. The figures, we later found out, come out of a report entitled, "The myths and facts behind cyber security risks for industrial control system," jointly produced by security experts at the British Columbia Institute of Technology (BCIT) and PA Consulting Group (PA). Research was based on data collected in the BCIT Industrial Security Incident Database, dating back to 1981. There has, apparently been a tenfold increase in successful attacks since 2000. Many of the attacked systems are said to be responsible for the operation of critical services such as electricity, petroleum production, nuclear power, water, transportation and communications. Data is collected through research into publicly known incidents (such as the Australian Sewage Spill) and from private reporting by member companies that wish to have access to the Database. We have to say at this point that so far we have only been able to find two real examples and a lot of fear. The two examples we can discover are said to be the 2001 case of a disgruntled employee hacking into the Maroochy Shire sewage system, in Queensland, Australia, and releasing raw sewage into parks and waterways. Another is said to be the hijacking of Gazprom's gas network in1999 when group of hackers are alleged to have gained full control over the gas flows in the Russia's largest gas network. Cyber security is one of the strongest arguments we have heard for sticking with PLCs as opposed to basing systems on PCs running Microsoft Windows. Dr Young said, "I can't see PLCs going away, my PC falls over far too often." Jordi Cruz of Rockwell added, "We don't use a commercially available operating system which protects us. Who is going to write a virus for a Control Logix processor? Much the most common causes of calamities, however, are still those resulting from human incompetence rather than malicious intent, which is a strong argument for systems that ensure users are properly authorised, preferably by biometric identification, and are designed to fail safe in all circumstances. Rockwell Automation British Columbia Institute of Technology industrial security incident knowledge base Dr Ken Young Eureka says: PLCs look likely to remain the backbone of industrial control systems for the foresee-able future, both because of their robustness compared with PCs and their relative invulnerability to computer viruses Pointers * Future PLCs look likely to be programmed with automatically generated code and systems based on them look likely to become even more robust and reliable than they are already * While cyber security is certainly a worry, use of PLCs, with their proprietary robust operating systems continue to give a large measure of protection