Process synchronisation using 2.45 GHz RFID By Staffan Gunnarsson , TagMaster AB, Sweden Scope

Automatic identification makes it easier to synchronise the supply-, manufacturing- and distribution chain, resulting in less capital tie up in materials, improved planning flexibility, less work force need and fewer faults. This article gives a brief summary of what is state of the art in high frequency tag systems, makes a comparison with other contactless identification technologies and gives a number of application examples.

Introduction to 2.45 GHz RFID

2.45 GHz systems are characterised by directional reading, long reading range, high passage speed, good immunity to electromagnetic interference (EMI) and very high tolerance to dirt.

Although the price of 2.45 GHz RFID has dropped dramatically, they are still more expensive than low frequency RFID (125 kHz, 13,56 MHz) and optical systems (e.g. bar code systems). Low frequency is used when a short range is acceptable and the environment is without EMI. Bar codes are used when the tag has to be very cheap and the objects are small and clean. A small market also exists for infrared ("TV remote control") systems. A rule of thumb is to use 2.45 GHz when the range is >1 meter, or when the passage speed is more than 1 m/s.

2.45 GHz RFID provides the best alternative when large and valuable objects like trucks, cars, palettes, car bodies, containers, train wagons etc. are to be identified, especially if the object speed is high and the environment is dirty. Automatic registration combined with access- and exit control at factories, ship terminals, distribution centres, airports etc. are examples where the systems are used. The investment often pays off in less than a year.

State of the art in 2.45 GHz RFID

New 2.45 GHz RFID systems are certified for use in all industrialised countries in Europe, Americas and Asia. They read at up to 6 m range and at passage speeds up to 400 km/hour. They can read several tags simultaneously and use multichannel technology to allow for an in practice unlimited number of readers in each installation area without interference problem.

Thanks to the improved communications infrastructure in a modern society, with widespread LAN, Internet connections etc., little or no data need to be stored in the tags. This lowers the system cost significantly and improves the managing system’s control and monitoring ability.

2.45 GHz tags can be programmable or read-only. Programmable tags make it possible to bring the freight data (article codes, quantities e.t.c.) with the object for stand-alone applications that operate independently of wide geographical area data networks. Network cost is however dropping these days, and freight companies now often use read-only tags with readers directly connected to the Internet/Intranet.

Both read-write and read-only solutions give the mentioned benefits, and it is up to the user to decide which solution best solves his problem. Like in PC’s, there is a trend towards application programmable and intelligent units implemented with database and modern protocols like TCP/IP (e.g. for Internet connection), further lowering the system cost.

Contactless identification technologies

The table illustrates a comparison of the possibilities with different remote identification technologies. It should be noted that all manufacturers do not provide every function.

How to use 2.45 GHz RFID

High frequency systems at 2.45 GHz is the best choice when a long reading range and high passage speed is needed in combination with a moderate cost for the data carriers. 2.45 GHz works excellent in dirty environments, with freedom to choose between read-write an read-only data carriers, and the reader and tag multiplicity give very high installation flexibility.

Applications range from manufacturing to distribution/logistics and access control for people and vehicles. 2.45 GHz RFID also provides excellent opportunities to design RFID systems with advanced characteristics. Some systems can even detect non-tagged objects!

Synchronisation; the automotive industry

Feeder lines to car factories. In order to increase their competitiveness, car manufacturers buy in advanced system components and sub-systems such as dashboards, seats, engines etc. from large and specialised factories. These highly advanced factories usually serve a large region, and the products therefore require long-distance transportation to the car plant. Since the products exist in many versions, often take as long time to manufacture as the car and usually are bulky and therefore hard to store, they need to arrive to exactly the right place and at exactly the right time.

With tags on the trucks, a 2.45 GHz RFID system can automatically report the arrival at the factory’s entrance, give access by opening the barrier and direct the driver to the right unloading point via one or more displays. The automatic guidance is appreciated since car factories are often huge and difficult to navigate. As a complement, an e-mail could have been automatically sent to the logistics system when the truck was identified at the exit of the specialised factory.

Main lines of car factories. The most automated section of many car factories is the welding shop and the paint shop, where sheets of steel automatically become painted car bodies ready to receive the previously mentioned engines, seats, dashboards etc. Since the welding and painting represent an first manufacturing phases, it is extra important that each individual car body is made exactly as ordered by the customer. It is difficult to change color afterwards.

With long range 2.45 GHz tags attached directly on the car bodies to control robots along the line, no problem exists to keep a perfect synchronisation, even when the manufacturing object is shifted between different conveyors, palettes and other carriers along the line.

If a short range tag would have been used instead, it would have been necessary to place it on the carrier instead of on the car. A complex registering system would then have been needed to analyse how each car is shuffled on or off palette and other carriers, a problem that is especially pronounced in view of rework and replanning.

Distribution of the car. It is a big task to manage the transportation from the factory car park to the dealer, perhaps in another part of the world. Using the same tag as in the assembly line, e.g. placed in the windshield, the car can automatically be registered when it is picked up from the factory car park, when it is loaded on the ship and when it arrives at in the receiving harbour.

It will arrive to the dealer exactly as expected, thanks to readers reporting each movement via an ‘Internet e-mail like’ system. The car company can plan well ahead, and the end customer can be sure that his/her car arrives on time and with the right options.

Synchronisation; other examples

Distribution centres. There are many ways 2.45 GHz RFID can be serve in distribution and retail. One example is in food distribution centres where the dispatch manager gets information each time a truck enters, to organise a new load and assign a load gate in the terminal building while the truck is cleaned after the previous run. Once the dispatch manager has ‘clicked’ the right new load, load gate and truck together, a display is lit to guide the truck driver to the right loading point.The RFID system can also be used for registration at the exit of that the load has been shipped. Barriers at the exit also prevent theft of trucks with valuable load, sometimes a major problem in distribution centres.

Unmanned factories, such as for concrete, asphalt and other bulk materials. The process industry often operates with little staff and around the hour. By automatic ID and weighing of the vehicles at plant entry and exit, a fully unmanned customer debiting is possible. This method is often used in e.g. in concrete and asphalt plants. Thanks to automatic identification, a display at the entrance can also here guide the driver to the right loading point, thereby avoiding queues and eliminating the risk that the wrong grade of material is loaded into the truck. When exiting, automatic correlation of the identity and weight difference of the truck also provides the necessary information for automatic billing.

Garbage centres. When consumables are about to reach the end destination, i.e. the waste dump, 2.45 GHz identification has proven to be valuable. Due to environmental restrictions, most waste dumps serve a very large area covering many different communities. To organise the debiting of each community in relation to how much waste that is delivered to the dump, long range ID of the garbage trucks when they enter provides an automatic debiting tool. As with the concrete trucks, the system can also be used to direct the drivers to certain locations at the dump to avoid queues. In sites where the waste is burned for energy, the truck ID also provides clearing of the energy value according to the load delivered.

Container handling . Automatic identification is needed when the transportation object, such as containers, will be out of reach for a long time e.g. when shipped by sea or air. It is for instance a challenge to organise the harbour’s container storage so that no container is missing when the ship is to be loaded. The trucks with containers has to be registered in on arrival, the containers cleared for customs and are then to be stored until they are loaded onto the ship. Huge cranes lift the containers from the trucks and place them a defined x-y-z position on the container pile. This way the containers are stored in the right order for the next step, i.e. lifting onto the ship.

A harbour handles many containers per year, and manual operations need to be minimised to eliminate mistakes. This is further emphasised by that the harbour is responsible towards road transportation companies, customs, the freight company and different service companies.

2.45 GHz RFID provides a cost efficient solution to the problem. There is no more any need to stop the truck for manual registration, since the 2.45 GHz tag can be automatically read and validated at the entrance barrier, custom’s weighing bridge and crane loading points. If the tag is in a sliding holder, it can also be brought out of the truck to make sure that the driver is at the safe area when the container lifting operation is to take place. The 2.45 GHz ID system can all the time monitor that he stays in the safe area through continuously reading the card.

Using 2.45 GHz identification, the containers are this way efficiently brought to the right storage position, well organised for fast and correct loading onto ships.

Associated use; access control in industrial areas

Harbours, airports and other industrial areas is visited by many vehicles each day, and vehicles belonging to the harbour’s employees, shipping/distribution- and service companies can also get convenient access if they use a 2.45 GHz card in the windshield. If a system with multiple card reading is used, cards can be permanently glued to the inside of the windshield identifies the car, while at the same time personal cards are used to also identify the people in the car.

With a reading range of up to 6 metres, access through gates is efficient and convenient. With a 2.45 GHz card fixed to the inside of the windshield, there is no need to painstakingly open a side window and stretch out to present a card for a prox- or swipe reader that controls the barrier. Nor can the system be tampered with by exchange of cards, since the long range card is perfectly read even when permanently fixed to the inside of the vehicle’s windshield.