Baggage handling system uses redundant Profibus DP

Italy's Marco Polo Airport, in Venice, was recently the subject of a EUR110million investment to create a new, high-efficiency hub for air travel across North-East Europe. Some 10 per cent of this investment was accounted for by the airport's high-availability automated system for baggage handling and security monitoring, within which redundant Profibus DP industrial fieldbus networks have played a major role.

Designed to cope with 6.5million passengers per year and 4000 pieces of luggage per hour, the airport's automation extends across 62 check-in points, four first- and second-level X-ray machines, two third-level X-ray machines, 23 pushers, six bays for handling and reconciling luggage, seven piers for arrivals, and five carousels for luggage claims. In total there are approximately 550 geared motors and over 3000 metres of conveyor belts.

At the heart of the control and command system are four fault-tolerant servers and 16 Siemens Simatic S7-400H high-availability PLCs. Two redundant PLCs in a hot-standby configuration operate each zone of the control system via fibre-optic cables. In addition, two redundant Siemens CP 443-1 communications processor cards connect the control system to an Ethernet network.

Network architecture

Four Profibus DP lines run from each pair of PLCs: two of these are connected redundantly to Siemens Simatic ET 200M remote modular I/O (input/output) stations by means of two Profibus IM 153-2 interfaces for each node; the other two lines are connected redundantly via two RS485 repeaters to Siemens TD17 text displays mounted on electrical cabinets within the relevant automation zone for viewing by the baggage handlers.

Each ET 200M I/O module runs both digital and serial signals via a Siemens CP 341 point-to-point communications module to the X-ray baggage control systems and ATR (automatic target recognition) bar code scanners that read the baggage tags. Siemens CP 342-2 AS-Interface Master cards enable the ET 200M modules to run a number of AS-Interface sub-networks for the direct connection of local sensors and actuators - including photocells, proximity switches, pushbuttons, indicator lamps, and motor starters.

After passengers have checked-in, their luggage is conveyed to the handling system located on the ground floor. Once inside the separate restricted-access area, luggage is subjected to rigorous automated and manual security controls. Following security clearance, the luggage passes through the ATR scanner-read system and each piece of luggage is directed to the appropriate pier for the flight on which it is to be loaded.

Indeed, in a seamless process that takes only a fraction of a second, luggage bar code labels are read, the information is transmitted to the control system, the data is matched to a flight and the automated system responds to direct the luggage to the appropriate pier. Once at the pier - but before being loading onto trolleys and transported to the respective aircraft - an operation known as 'reconciling' takes place, wherein the luggage bar code labels are scanned manually to ensure that each passenger on the aircraft has his or her luggage and that there is no unaccompanied luggage.

High-performance redundancy and distributed automation together ensure high availability and cost-efficient diagnostics, which is very important in view of the extreme complexity of the overall baggage handling and security system.

Thanks to the redundant PLCs and Profibus DP networks, Marco Polo Airport has benefited from a complex yet highly dependable automation system that helps it to operate extremely efficiently.