Traditionally, Field Device Technology (FDT) had been associated largely with process automation and process field devices, but this is no longer the case. Suppliers in the factory automation space are now adopting FDT because they find it affords them the technical flexibility needed to deal with the wide range of product configurations their customers demand.
Factory equipment suppliers and machine builders, even major ones, must comply with the system specifications demanded by end user manufacturers. As a result, they must deliver their products to support one of many different combinations of factory automation system and fieldbus. We at ARC spoke with one major equipment supplier that now uses FDT to increase product flexibility without adding permutations to its product design.
As the owner-operators, end user manufacturers (such as global automotive companies) create the specifications for their factory production systems. Their specification decisions flow “up” the value chain, while the products that equip the factory flow in the opposite direction. This complicates matters for the equipment and device suppliers further up the chain who must serve a large number of end user customers, each with its own specifications. One major technical challenge they face is to customize their equipment as demanded by each end user without creating a large number of product permutations that would be prohibitively expensive to develop, maintain and support.
Sandwiched between
Equipment suppliers must usually support user-chosen factory automation systems as well as user-chosen factory fieldbus technologies. End users usually prefer to standardize on one automation platform and as few fieldbuses as possible. This greatly simplifies the end user’s operating and maintenance tasks over the operating life of the equipment, but the machine builders can find themselves sandwiched between their customer’s automation and fieldbus choices. This places a premium on a supplier’s ability to be flexible. Complex machines will likely contain one or more embedded controllers supporting proprietary machine features. So the machine builder must integrate its own embedded control technology with whatever else the end user specifies.
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FDT, the IEC 62453 standard, is a software interface specification for interoperability between field devices and automation systems. Its design basis is such that FDT-enabled applications within the automation system can manage field devices regardless of the device’s manufacturer and regardless of the fieldbus protocol employed.
This flexibility is achieved by equipping each device with a unique software element called a Device Type Manager (DTM). FDT-enabled applications called “FDT Frame Applications” contain a fully defined interface to DTMs, providing interoperability between any pair of Frame Applications and DTMs. Frame Applications typically operate in a Microsoft environment.
The scope of the FDT interface includes more than operating data communication. DTMs can be used over the device’s entire life cycle. Functions for device parameterization, messaging, health monitoring, interactive functions, and online help can be integrated into a DTM. Effective implementations can provide support from commissioning to repair.
Implementation example
ARC Advisory Group interviewed one large (over $1 billion annual revenue) global supplier of factory equipment that has begun embedding FDT into its equipment controllers. The supplier asked to remain anonymous. The supplier’s decision to use FDT was driven by its customer’s demand to support several different programmable logic controllers (PLCs) for factory automation and over six different fieldbuses to the various devices that are used with their equipment.
The supplier’s FDT implementation presents fieldbus-independent process data both to its controller and to higher-level automation systems. The company has embedded FDT into its controller to such a degree that the end user does not see it.
Asked to summarize their experience, company representatives said that the move to introduce FDT into their controllers was difficult, but they felt the difficulty was worthwhile, reporting, “It has great benefits whenever you face a wide range of fieldbus protocols."
>> Harry Forbes, [email protected], is senior analyst at ARC Advisory Group in Dedham, Mass.
