OPC Unified Architecture (OPC UA)

The organization of an ecosystem in three tiers can also be found in other domains. For example, a significant part of the industry 4.0 domain is shifting towards the OPC Unified Architecture (OPC UA). OPC UA is a standard for machine-to-machine communication comprising communication infrastructure and information models for semantic data exchange. OPC UA is standardizing connectivity of industrial devices and enables the interoperability among products of different vendors. It does not yet address the next level of interoperability which we call “composability”.

The OPC UA ecosystem is in its structures exactly conformant to the explicated tiers of the RobMoSys ecosystem approach. The OPC foundation is the driver in tier 1, the companion specifications belong to tier 2 and finally there are the users at tier 3. The strong point about OPC UA is that it is driven by industry in a joint effort and that they successfully manage the ramp up of an ecosystem along these tiers.

A direct comparison of the RobMoSys Ecosystem with OPC UA is given in the figure below.

As prominent example for domain models (companion specifications), VDMA is working on companion specifications for vision and robotics. Companion specifications sometimes contain additional concepts that have evolved in a particular domain, but that are generally applicable. For example, the companion specification for vision foresees a generic state automaton for components with component-specific sub-states—a very similar concept to the RobMoSys component life-cycle and communication pattern "state pattern". In the long-run, they may be adopted by OPC UA itself, thus move from Tier 2 to Tier 3. This movement of structures describes the evolvement of an ecosystem and also has been identified for RobMoSys (see wiki page on „Tier 1 in detail“). OPC UA is actively postulating the creation of companion specifications by providing support and guidance.

OPC UA eases device integration thanks to an overall methodology (Tier 1) and domain-specific standards (composition Tier 2). Device suppliers now can adopt the Tier 2 standards and gain compatibility with users that expect these standards. OPC UA, however, does not specifically aim for composition and is, in fact, less suitable for composition of software components. It misses adequate abstractions and concepts (e.g. such as RobMoSys communication patterns). However, composability starts being addressed in OPC UA as it can be observed in recent developments that are on the way to introduce the concept of skills.

OPC UA can also be used as an underlying communication infrastructure below the RobMoSys structures. In the context of composition, the challenge with OPC UA is to introduce additional structures that enable composition. This is done by, for example, the RobMoSys communication patterns. This is where the German national BMWi/PAiCE Project “Service Robot Network” (SeRoNet) is adopting parts of the RobMoSys composition structures and provides a mapping to OPC UA. Thereby, SeRoNet can fully benefit from composition as introduced by RobMoSys but also manages the seamless integration with the traditional OPC UA world, for example to use OPC UA powered devices.

In general, the industry 4.0 world based on OPC UA has a fully conformant way of thinking with respect to the overall RobMoSys world. Thus, there is a very good chance to communicate the RobMoSys contributions to that domain and thereby link the robotics domain with the automation domain. While OPC UA and its companion specifications at the moment are at the level of integration with a roadmap towards the next levels which we call composability, RobMoSys already now proposes solutions to address composability. Due to the very same ecosystem structures, there is a very good chance to enable adoption of the RobMoSys outcomes within the industry driven OPC UA automation domain. For RobMoSys, the strength of OPC UA is that it provides standardized and uniform ways to access all kinds of devices like sensors, actuators, machineries, cloud services etc. RobMoSys puts its focus on the software composition for most complex sensori-motor systems which then can get networked with industry 4.0 environments via OPC UA.

See also


other_approaches:opc-ua · Last modified: 2019/05/20 10:47