PLC Checker verifies and improves quality of PLC programs

Herakles is a world leader in the design, development and manufacture of solid rocket motors for missiles and space launchers. Its products meet demanding requirements for safety, performance, reliability and availability.

The very demanding domain of activity of Herakles requires advanced quality control of the manufacturing process. However, Herakles, which is a Safran Group subsidiary, had no way of verifying software quality for its industrial control systems. Previously quality had been monitored by means of sampling and manually checking code compliance, but this method was felt to be too limited to meet Herakles' strict quality requirements.

PLC Checker, Itris Automation's automatic verification tool for PLC programs, has been used systematically since 2010 on every new or significantly modified program. The return on investment is estimated to be 200 per cent, with significant improvements in programs quality and more efficient maintenance.

Implementation

Itris Automation first starting working with Herakles to define the process of how to measure the quality of the PLC programs in terms of compliance with Herakles' rules and standards. The original method used by Herakles consisted of manual code reviews to verify compliance. However, this approach had many drawbacks: relevance and precision of the review was highly dependent on the person in charge and an exhaustive review was unfeasible because of the huge volume of code. The cost of the approach was also a limit when reviewing large PLC programs. Finally, the return on investment of this mandatory activity was considered to be very low.

As a consequence, the development teams were looking for an alternative and they discovered PLC Checker, a collaborative cloud-based tool for the static analysis of PLC programs. PLC Checker enables programming mistakes to be identified, computation of quality metrics and verification of compliance with standards. Herakles was also very interested in the fact that industry leaders such as Schneider Electric, EDF, Areva, PSA Peugeot Citron or GDF Suez were already using PLC Checker.

After a pilot project, Herakles concluded that PLC Checker was the right solution to the problem of how to control automatically and systematically PLC software quality as required by its internal standards and also an independent third-party approach.

Pascal Pothier, an Automation Project Manager at Herakles, explains: "We decided to leverage PLC Checker for two different usages. First we wanted to do some one-shot audits at the end of the development, thus making a 'picture' of the quality. Then, we decided to deploy PLC Checker during the whole development, thus making a 'movie' to see how quality was evolving and allowing bug fixing as early as possible. All system integrators working on our programs are trained and granted a license for PLC Checker for the duration of the project. They can make as many 'pictures' as they want to build the 'movie' and we are very satisfied with such a continuous improvement approach."

Teams from Herakles and Itris Automation have collaborated to deploy PLC Checker step by step. First, Itris Automation's engineers created a set of coding rules inspired by Herakles' existing standards and practices, and leveraging Itris' experience in several sectors.

A couple of months later, Herakles decided to use PLC Checker systematically on every new, migrated or significantly modified PLC program. Feedback from developers and users of PLC Checker has been taken into account to improve the rules and, since 2010, 26 programs from ten different projects have been verified with PLC Checker.

Business benefits

Pascal Pothier further explains: "Between 2010 and 2012 we have improved our compliance ratio from 63 per cent to 85 per cent and have thus improved significantly the maintainability of our programs. This was made possible by the formalisation and standardisation of the development."

After these first use cases, Herakles has now decided to use PLC Checker more widely and beyond the scope of its factory at Le Haillan. Pascal Pothier adds: "After a couple of years using it, we can consider that the deployment of PLC Checker is a success. Of course, at the beginning, system integrators were reluctant but they have been convinced by the tool itself and now agree that this is necessary in our industry.

"Since we began using PLC Checker, our Factory Acceptance Tests have been quicker and more efficient. Plus, the maintenance of the programs is easier. We estimate the return on investment of the usage of PLC Checker to roughly 200 per cent just by counting the savings in the test and commissioning phases. The programs are easier to read and thus to modify and correct in the factory. Also, thanks to a better consistency, the training of our maintenance team is faster."

PLC Checker is currently available for use on the following platforms:

• Schneider Electric Unity Pro and PL7 Pro
• Siemens Step 5 and Step 7
• CoDeSys v2.3, v3.2 and v3.5
• Rockwell Automation RSLogix 5000
• Mitsubishi GXWorks 2
• Omron Sysmac Studio
• PLCopen XML

Follow the link for more information about Itris Automation and its tools PLC Checker (automatic analysis of PLC program quality), PLC Converter (automatic conversion of PLC programs) and PLC DocGen (automatic documentation and reverse engineering of PLC programs): www.itris-automation.com.