Westinghouse Rail Systems reduces SIL4 validation effort by 70% with Artisan Studio

WRSL has developed equipment compatible with the European Rail Traffic Management System (ERTMS), under the Invensys Rail Group’s FUTUR brand. A major element of the ERTMS Level 2 solution is the Radio Block Centre (RBC) which sends proceed authorities to trains based on their position and signaling status.

The first application of FUTUR at ERTMS Level 2 is being implemented on the Cordoba to Malaga high speed rail line in Spain. ERTMS Level 2 provides significant benefits in terms of capacity and performance improvements, enhanced safety beyond traditional Automatic Train Protection, and a reduction in operating costs over the railway lifecycle.

WRSL’s RBC for ERTMS Level 2 is a SIL4 system implemented in Ada. For the front-end systems design, WRSL drew heavily on the model-driven capabilities of Artisan Studio, the collaborative modeling environment for complex, mission and safety-critical embedded systems and software from Artisan Software Tools. Artisan Studio was used to specify the system requirements of the RBC in a definitive UML model that would drive the software implementation. However, the all-important back-end SIL4 validation process remained a rather complex and somewhat time-consuming manual process.

“Early in the validation process it was clear that, although very thorough and efficient, the manual process would benefit significantly from automation,” said Tony Smith, R&D Validation Manager for WRSL. “With four distinct activities in the validation process – flowchart diagram generation, flowchart path analysis, the generation of test cases and report production for test case runs - the manual approach naturally incurred a large time overhead. It also introduced potential risk from human error. The manual process lacked flexibility. It was effectively intolerant to changes made to the original model as even the most innocuous design change could impact any of the validation test cases resulting in a massive validation task.”

In seeking to automate the SIL4 validation process for the RBC, WRSL looked to its positive experience with Artisan Studio in defining the original UML model. “Automation was all about using the UML model to its best effect from a validation perspective,” continued Tony Smith. “With getting on for 100 Object Sequence and State Diagrams in the model, resulting in the need for around 450 test cases to validate close on 2000 potential paths, Artisan Studio’s OLE interface was the key to automating the validation process.”

Automatic production of flowchart information for validation use has not only eliminated human error but also the time overhead incurred in the previous manual process. Rather than validation engineers having to manually analyze data previously encapsulated in Excel spreadsheets, the validator is presented with the information in an easy-to-interpret visual format that provides graphical classification of paths and automatically detects incompatibilities, saving both time and money in development of validation tests. In addition, the use of Artisan Studio allows the Westinghouse Rail Systems team to enforce project wide development policy as the OLE interface allows a separate tool to interrogate the UML model for design errors by comparing diagrams to the design standard that exists for Object Sequence Diagrams.

“Time saving to speed development of test cases was the prime motivation for automating the SIL4 validation process for the RBC,” commented Tony Smith. “Having successfully used Artisan Studio for the model development, it only seemed natural to extend its use to automating the validation process. As such, it has resulted in an immediate reduction in validation costs by delivering a staggering 70% reduction in validation effort needed, by eliminating both the manual translation of the model to a flow chart and the potential for error.”

“WRSL’s decision to extend the use of Artisan Studio from requirements specification to system validation is a positive demonstration of our vision of enabling large and often geographically dispersed teams of analysts, systems and software engineers to Work as OneTM, modeling systems and software for the complete project lifecycle from conception to implementation and ongoing support,” said James B. Gambrell, CEO of Artisan Software Tools. “The use of Artisan Studio to drive the automated SIL4 validation process for the RBC has given WRSL the ability to better manage design changes and future product versions from the perspective of compliance. With automation, once the process is proven, validation is all about repetition. The automated process makes WRSL far more responsive to change and gives them the confidence that the impact of change is being fully tested. Now, even the subtlest of design changes to improve RBC performance can be handled with relative ease.”