Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

K.H.P. Hemmen The Intelligent Conveyor Belt
Masters thesis, Report 2005.TL.6973, Transport Engineering and Logistics.

The subject of this research project is the intelligent conveyor belt with integrated RFID. This research assignment is issued by Ammeraal Beltech. This is a conveyor belt company of belts for light and medium heavy applications.

RFID, short for radio frequency identification, is a way to identify an object by data transfer using radio waves. This data transfer takes place between an electronic reading device and an electronic data carrier, the transponder. They can communicate wireless because of the use of electromagnetic (radio) waves. The RFID system consists of a transponder (or tag) attached to the object that is to be identified and a reader. Both the transponder and the reader use an antenna to be able to communicate with each other. The antenna of the reader is large because it must create an energy field to power the transponder and it also has to receive the weak signal of the transponder. The components of the transponder are very small.

The operation of a common RFID system is as follows: The reader develops an energy field (electromagnetic field) through its antenna. This field excites energy (voltage) in the transponders antenna. This energy is used to operate the transponder, which is sending back its data through its antenna. This signal is received by the reader and processed further. The reader powers and operates the transponder.
The transponder is an important item in a RFID system, because this is the device that is placed on or in the product. With many different products and different environments, the transponder often has to fulfill specific requirements and this asks for different transponder designs. Areas of use differ from animal identification to pallet tracking to automatic toll collecting. Because of this, RFID uses four different radio frequencies: LF, HF, UHF and microwave.
A RFID transponder is read only, write once/read many or rewriteable. The transponder can be passive or active. In the passive type, all the power for the operation of the transponder is delivered by the (electromagnetic) field generated by the reader. To enlarge the read range there are active transponders, which use a battery. This battery powers the microchip and/or delivers the power for sending data to the reader.

The reader's main functions are to activate the transponder and structure the communication sequence with the transponder. The reader enables contactless data transfer between the application software and the transponder. The reader can be stationary or handheld.

Standardization is important in the worldwide application of RFID. Frequency bands must be determined globally. Governments and institutes already designated the frequency bands available for RFID. The HF and microwave frequencies are worldwide but the LF and especially the UHF range differ per region. Organizations are trying to agree to one UHF frequency band.
Not only the frequencies must be standardized, but also the power level of the signal must be determined. It differs per region per frequency range and the organizations are trying to straighten that out. Standard organizations (such as ISO) designed standards concerning topics such as communication protocols, field strength and interference. Besides the hardware, the software must be developed. Organizations like GS1 (EAN) are developing a uniform code that can be used in the FMCG (fast moving consumer goods) sector: the EPC (electronic product code). The EPC is an agreement about a code system like the barcode system and also involves transponder type, frequency, etc.

Besides RFID, there are other automatic identification methods, such as optical ID (barcode), magnetic ID (cards), smart cards and biometrical (fingerprint). While RFID can compete with all techniques, for instance in the access/security field, a comparison with the barcode (optical ID) is the most interesting. It is important to notice that RFID can offer more than the barcode. Although the barcode is a very efficient way to identify an object, it can't do more than identifying. RFID, on the other hand, can do more. For instance due to the larger data capacity, much more information of the object can be stored. Also, the possible combination of sensors can deliver even more information, for instance temperature tracking.

The RFID technology exists already for decades, but in the last few years there were many technological developments. Components got smaller and more efficient, read ranges and data capacities were expanded. Improvements and innovations will continue in the future. From a very small microprocessor to printed antennas and all polymer transponders. A different approach in developing RFID is to make the RFID transponder intelligent and communicate with each other.

While RFID still isn't a full-grown technology, it is being used for quite some time. The most common applications nowadays: Access and security, transport and logistics, tracking and tracing and authentification. The main goal of the applications for Ammeraal Beltech is to enlarge the reliability of its products by structuring and controlling operations, such as maintenance (checks) or monitoring of belts, with RFID. Interesting are identification of the belt and maintenance/monitoring with the intelligent belt.

If a RFID transponder is integrated in the belt, every bit of necessary information about the belt can be written to it and read from it any time, even while it is running. This can be in the form of a unique code that is linked to product information in a database. It means that all information can be on-site and directly available and not somewhere in the administration. In this manner data is collect more efficient, which can reduce labor time and errors.
RFID is the selected technique because RFID is small enough to be integrated in the belt so it is protected from the environment. It is clean what is necessary in food applications. It is operated wirelessly, which simplifies reading and reading can be done while the belt is running. RFID also has the possibility to write to the transponder. Barcode, for instance, must be on the surface because of the line of sight that is necessary to read it. This means it is vulnerable to the environment and can get damaged or dirty.

A belt with an integrated transponder can be used for more than identification only. The possibility to write to the transponder can be used in maintenance applications. Each time the belt is serviced or checked, it can be written to the transponder. With this information it is not only possible to know the last service but also a history of the maintenance is available. From this history, the behavior of the belt can be analyzed. One step further in maintenance is to have the belt signaling the operator that it needs service (for instance tensioning). The belt monitors its own performance and gives a warning signal whenever there is something wrong. Failure of the belt conveyor can be caused either by the installation the belt runs on (drive) or by the belt itself. Preventing failure of the belt is the responsibility of the user but also an opportunity for AB. When the belt is installed and in use, maintenance (monitoring) is important in order to maintain a good performing belt and to prevent failure. This can be done by measuring and monitoring tension and slip.
However, measuring conditions inside the belt is very complicated because of the environment with constant stressing and bending. Because of this, accurate measuring is almost impossible. In stead, measurements can be taken outside the belt, but this is also immediately outside the territory of Ammeraal Beltech. However, the measurements, although inaccurate, can indicate changes in the belt. If the measured values (i.e. tension, temperature) are outside a certain range, then something is happening to the belt and a warning signal can be given: Check the belt for possible bad performance. In this way the reliability of the system can be increased and sudden failures can be decreased.

With the transponder integrated in the belt, the transponder and the belt influence each others behavior. Since the transponder is relatively small and sensitive, the belt and environment will have much more influence on the transponder than the other way around. Therefore the most important subjects are: stress (varying normal stress, bending), temperature (welding, process) and chemical interaction (adhesion, reactions).
The belt is only affected by the transponder because some belt material is replaced with material with different behavior. This can in the worst case lead to delamination or surface wear (there where the transponder is placed). For these reasons it is always best to have the transponder as small as possible. On the other hand, the movements of the belt put serious stress on the integrated transponder. With this in mind, there are actually two options: Since all transponders, at least up to this date, consist of a fragile microchip and copper or aluminium antenna, which cannot withstand constant bending and large strain, first of all, it is best to try the very stiff transponder approach. When a flexible, strainable transponder is available or developed, that can withstand the stresses in the belt, then finally that is the best compromise. The transponder to select for integration should be passive and electronically operated. Currently, there are two usable transponder types: Although the UHF transponder is not full-grown yet, its performance is much better than the LF transponder (range, speed). But since the belt is a difficult environment for the delicate electronics, it is best to select a very tough transponder. It is possible to encapsulate the UHF transponder but then it will be too large to be integrated in the belt. Data transfer speed becomes important when a large quantity of data needs to be exchanged with a running belt. For identification only, with a unique code linked to information in a database, the data speed is not very important (LF should be fast enough). Together with durability and current availability, the LF transponder is the best choice for now. This transponder type is very tough and the only disadvantage is the estimated short read range and slow read speed.

Future developments can make the UHF transponder smaller or flexible and more suitable to be integrated in the belt. This would offer possibilities to store the data directly on the transponder and UHF is also more capable to be combined with sensors. Still, it is strongly advised to make the transponder stiff to withstand the stressing or completely flexible with an other antenna material than copper or aluminum.

A practical test proves that with the currently available transponder types, it is possible with LF to identify the belt. Both the belt and the transponder remain undamaged. Downside is the very short read range (1-2 cm) and the restricted thinness of the belt. HF is not suitable with the copper or aluminum antenna and too large when encased (>4mm). The standard UHF/microwave transponder is to be tested with a handheld reader but with a copper or aluminum antenna, it is also suspected to break due to bending and stressing.

The costs of the transponders are important because in a normal (barcode replacing) application, thousands of transponders are used. In this case where a transponder is integrated in the belt only the cost of one transponder is added to the cost of the belt (which is a fraction). But besides the transponder, there is also the need for a reader. Readers can be expensive, especially when they are used in this particular application at Ammeraal Beltech. The reader is periodically used to identify the belt and if it is used for one or a few belts only then the identification of a belt with RFID is an expensive solution. The case where identification of belts is interesting is in the large users, for example an airport. In this case there are hundreds of belts where the costs of one or a few readers are divided over. On top of that the reader will be used more frequently and this justifies the cost of the reader.

It is concluded that identification with Lf is possible but the performance is very limited and too restricted for in field use. Since HF is unsuitable because of the shape, the UHF transponder is the best choice performance-wise and with this transponder a combination with sensor(data) is possible. Handheld UHF readers are expected soon (2006). For the physical layout of the transponder there are two possibilities: fully flexible (follow the belt's movements) or fully stiff (withstand the belt's movements). Recommended is the flexible option because the antenna is still relatively large (making it stiff results in a large transponder) and this option will influence the belt the least. The antenna design can be a next step in the development of the intelligent belt, followed by the development or selection of tension and temperature sensors and the design of an interface with the transponder.

With the current state of RFID it is not recommended to produce the intelligent belt. The right transponder is not available yet and the belting market is not asking for a belt with integrated technique. Ammeraal Beltech is not risking much by waiting a few years to let RFID proove itself and let the proper transponder being developed. In the mean time real customers and applications for the intelligent belt can be found. When the right transponder is available on the market is hard to predict, since the RFID market is mainly focussed on logistical applications (excluding constant bending applications), but it will take a few years.

Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2005.10.03; , TU Delft / 3mE / TT / LT.