I and II Packaging Profile
Packaging applications have benefited greatly from the adoption of the Sercos interface in controls and drives. Many packaging machinery manufacturers are shipping machines today that were designed from the ground up using servo technology, in which hundreds of mechanical components have been eliminated, costs have been reduced and flexibility has been maximized.
The Packaging Machinery Working Group of the North American OMAC (Open Modular Architecture Controls) Users Group published a recommendation in November 2001 to use Sercos interface (IEC 61491) as an open drive interface for packaging machines. In this context, the group challenged the Sercos organization to further improve the multi-vendor interoperability of servo controls and drives on the basis of a packaging profile.
The Sercos organizations responded by creating a packaging profile that defines a subset of the Sercos interface parameters that are applicable to packaging machines.
The Sercos interface specifies more than 500 standardized parameters that define the interaction between controls and drives in a vendor-independent manner. The Sercos specification supports the interoperability of controls, drives and I/O devices from different manufacturers on the basis of an open real-time communication system.
However, in practice, issues arise which make the idea of "plug and play" more difficult to implement. Only a subset of all existing parameters is needed for most applications, as some parameters have been designed for very specific use only (i.e., spindle positioning in machine tools), or they deal with optional interfaces (e.g., position feedback value of an external feedback). Thus, not all vendors implement all parameters in every device they produce.
Another issue is that motion control functions can be integrated centrally in the control as well as decentrally in the drives. This depends on the functionality of the servo drives, which may vary from manufacturer to manufacturer. Machine builders have different philosophies and preferences with regard to control architecture. Thus, depending on the drive functions that are used by a control, a different set of Sercos parameters is required.
To keep this complexity manageable and to ensure the highest interoperability of controls and drives, it was decided to implement packaging application-specific profiles as subsets to the Sercos
I and II specification. Existing Sercos function groups and the corresponding parameters have been mapped into profiles for three of the six OMAC-defined application classes. The profiles consist of mandatory and optional parameters for simple servo drives and frequency converters, and also for intelligent drives, which can be commanded by any of position, velocity or torque values. Thus, any servo drive/controllers that implement the pack profile will be interoperable.
The basic Sercos I and II pack profile includes about 15% of the
overall Sercos instruction set, while the extended
pack profile includes about 40%.
It's important to note that the pack profile doesn't restrict drives/controls to only the defined parameters; but it does require that the drive/control implement the defined parameters in the defined manner in order insure compatibility.
You can obtain more details in the Pack Profile specification and a
white paper on the subject.
Example of Mapping Sercos interface Parameters
in Different Profile Types