SATURN: SIL2-Certified Fail-safe Remote I/O System Architecture for Trains

Leroy Automation

LEROY AUTOMATION, a leading manufacturer of on-board automation systems for train control and management systems (TCMS), partnered with CLEARSY, a specialist in railway safety-critical systems, to develop and market SATURN, a cutting-edge SIL2/SIL4 fail-safe controller and remote I/O platform for train control, propulsion and rail signalling system architectures.

SATURN is a commercial-off-the-shelf (COTS) platform offering a cost-effective solution to accelerate ‘time-to-market’ and to boost transit rail car projects without incurring the elevated costs and high risks of an Independent Safety Assessment (ISA) process.

The SATURN platform is a product portfolio built on a generic concept. It supports mixed heterogeneous configurations of SIL0, SIL2, and SIL4 modules on the same unique copper cable or fibre optic-based communication network. SATURN allows system engineers to design fully integrated, efficient, and cost effective I/O management systems for train operations with both safety-critical and non-safety-critical equipment on the same data network. The SATURN platform can be expanded by adding self-contained or custom I/O modules to match any on-board application requirements. It is based on an innovative state-of-the-art dual, redundant ring communication network, and an open safety protocol fully compliant with EN 50159-2 standard.

"The SATURN concept is inherently flexible and we invite our customers to design and integrate their own SATURN-compliant I/O modules without any limits!" says Thierry Servat, managing director of CLEARSY.

Each SIL2 SATURN module and the full SATURN platform have been independently tested and certified to meet the rigorous SIL2 requirements of the EN 50129:2003 standard, and the SSIL2 requirements of the EN 50128:2011 standard. These certifications have been performed by CERTIFER, a world leader in independent expertise of rail and guided transportation products and systems. Examination certificates along with their appendices, issued by CERTIFER, are available and can be consulted upon request.

The SATURN platform is available as a size-3U rack-mountable solution or as a standalone distributed, modular, and scalable system.

It is extremely reliable, and it supports redundancy mechanisms to implement highly available remote I/O system architectures. "Moreover, the SATURN platform delivers unmatched performance with one millisecond time-cycle", comments David Rambaud, technical project leader at Leroy Automation.

The following certified SATURN modules are available off-the-shelf:

  • The SIL2 gateway module which supervises the system, and acts as a dual 10/100T-BASE Ethernet-based communication gateway. It also supports the implementation of logical algorithms and Boolean tasks
  • The two SI2 and SO2 remote I/O modules which respectively feature 4 SIL2 digital inputs, and 4 SIL2 relay outputs
  • The SIO0 remote I/O module which features 4 SIL0 static outputs and 12 SIL0 channels, each configurable as a digital input or output
  • The powerful 72Vdc power supply module which is compliant with DC-direct train battery voltage line, without the need of any DC-DC converters. Its main function is to power all the modules connected to the SATURN system

The SATURN product line also integrates real-time diagnostics that can be utilised as interpretative data for predictive maintenance activities.

SIL4 modules are currently undergoing certification testing, and will soon be integrated into the SATURN solution product line.

Typical rail applications include on-board train control and monitoring systems (TCMS) for light-rail transit (LRT), passenger trains including subway, commuter, inter-city and high-speed rail; computer-based train control (CBTC) for automated driverless metros, as well as wayside signaling equipment such as automated platform screen doors (PSD).

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