PLCs and HMI keep the traffic flowing

GE Fanuc PLCs and Cimplicity HMI offering hot-standby redundancy are being used to provide vital traffic control through the 2km Strahov tunnel connecting the Southern and Western districts of Prague.

GE Fanuc PLCs and Cimplicity HMI offering hot-standby redundancy are being used to provide vital traffic control through the 2km Strahov tunnel connecting the Southern and Western districts of Prague.

The Strahov tunnel, together with the Mrazovka tunnel, form part of the inner ring of a new double ring traffic system developed around the heart of Prague.

This layout has been designed to rid the historic centre of the city of traffic congestion and pollution.

The Strahov tunnel cuts through the Strahov hill in the SW of the city.

It provides 2 lanes in each direction (through separate tubes).

Traffic volumes amount to around 12000 cars per day using the tunnel.

Eltodo, a.s., was the supplier of the key elements of the traffic control system.

It manufactures the sophisticated road signage and was responsible for the installation of the traffic sensors and CCTV cameras and monitors, the traffic information systems, the control systems, the energy distribution, the tunnel lighting, etc.

SOS boxes, placed at regular intervals throughout the tunnel, provide immediate communication with the control rooms in cases of emergency.

Other sensors detect pollution levels, air-flow speed, visibility, etc., providing information that can be fed back to vehicle drivers if applicable.

Two control rooms monitor the total system.

The main tunnel traffic control is actually on top of the Strahov tunnel and utilises Cimplicity HMI to provide information on the status of traffic and on all parts of the control network.

The other room is part of the elaborate traffic control system for the whole city.

This is located away from the tunnel and is run by the Prague police.

In each control room are 8 monitors with 2 operators designated to oversee the system.

Manual intervention is possible via the control panel.

At the entrance to the tunnel, traffic is controlled by light signals.

Emergency closure barriers can be lowered if needed.

Sensors at both ends provide feedback to warn of black-ice.

Within the tunnel are variable lane signals, devices for measuring vehicle speed and density and sensors for measuring vehicle height.

In total, 175 road signs providing information to drivers can be altered via the control system.

The signs, manufactured by Eltodo, include fibre-optic displays, static backlit panels and triangular prism based signs which change when rotated.

The control system has been developed around GE Fanuc hardware and software.

Two PC servers running under Cimplicity HMI operate in hot-standby redundancy mode in the Strahov control room with an Ethernet link to a third PC running Cimplicity in the police control room.

A pair of GE Fanuc 90-70 PLCs, which are synchronised in hot-backup redundancy mode, act as the 'central control' for I/O to and from the other PLCs in the system.

Data for a large MIMIC wall is also fed from the 90-70s providing a visual image of the current status of traffic and control systems in the whole tunnel.

The electrical power needed to run the complete control system comes from two alternative sources.

If one fails the other will continue to supply the whole system.

If that fails, the main parts of the system will operate from a UPS backup.

Links to the twelve remote 90-70 PLCs and seventeen 90-30 PLCs are via two GE Fanuc Genius buses, one to each end of the tunnel.

These buses are also in redundant pairs providing a link from either of the data concentrator PLCs.

On one pair of buses a pair of 90-70s operates in hot-standby, controlling 5 further 90-70 PLCs each, via further twinned Genius buses.

These 90-70s control the vital ventilation and air conditioning systems that exhaust and replace the exhaust fumes in the tunnel.

90-30 PLCs control traffic signalling, fire signalling, the SOS booths, lighting and underground heating to minimise the risk of ice, and they also optimise the total power consumption.

They are linked directly by the Genius buses back to the main pair of data concentrator 90-70s.

The 90-30 PLCs themselves are in redundant pairs for the vital control of signalling, SOS boxes and power optimisation.

Ing.

Sedlak, SW manager of Eltodo, explained the benefits that have accrued from the use of GE Fanuc equipment in the control and monitoring system, "The system is extremely robust.

The in-built redundancy has created excellent security and assurance that the system will continue to operate reliably in the unlikely event of a component failure.

The use of the Genius bus has also greatly reduced the wiring time and ensured a simplified backup for the network.".

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