My December article was entitled "Digital Twin". Why cover the same ground again?
In the ever-evolving world of industrial automation, things can change quickly. In the case of terminology that is introduced to industry without clear definition, the same applies to digital twin.
My latest revelation came from a discussion with Lisa Seacat DeLuca, who leads the incubation and incorporation of the digital twins at a major participant in the industry. Until this discussion, I and members of the Industry 4.0 Lexicon team have been searching for the attributes that define what a digital twin is. After talking to Lisa, the perception of what a digital twin means may be much broader than we thought and may require a different approach.
We in the process industries have different usage cases than software providers may typically encounter, so differences in terminology may be inevitable. If you ask a papermaker what a pump or a valve is, the description will be a lot bigger with a lot more functionality than what you may get from the local hardware store. However, since much of the terminology we use in Industry 4.0 originated outside of industry, in order to do a thorough job, we need to go to the original source. Digital providers may be one of those sources.
What surprised me most from my discussion with Lisa is that her company has the following definition for digital twin: "A digital representation of a physical thing." That's it. The attributes are that it is digital and represents a physical thing. I asked Lisa if I pull 6 months of data for 50 tags from a Kamyr digester and save that file on a disk, is that a digital twin. She said yes; a dataset is a digital twin.
I think most of us would find it surprising that datasets that we have generated from the beginning of Industry 3.0 meet the expectation of the new and cool digital twin that is a buzzword today. Essentially, the term is so broad that it applies to darn near anything we have been doing for 50 years.
In further discussion with Lisa, there was refinement of digital twin into 3 states of operation:
OFFLINE: A digital twin that is not in any state of operation, such as a dataset sitting on disk storage
IDLE: Digital data is being used in runtime, but it is not connected to a live process, such as a simulation system
ONLINE: Digital data is being used in runtime and is connected to a live process, such as an HMI in a DCS/SCADA
This seems sensible; however, the wording can be problematic. In industry we typically refer to a simulation system as offline. If you have a hot spare DCS/SCADA system that has IO tiebacks or high-fidelity models to simulate the process, we consider this an offline system. In the 3 states listed above, it would be considered idle.
All 3 of these states have examples that have been with us since Industry 3.0. If we want to know which digital twins are new in Industry 4.0, it would appear to be a subset of those in the online state. Here are some names for digital twins of this kind such as:
Maintenance & Part Twin
The bottom line is that the term digital twin is new but actual digital twins are not new, and you can't know what a digital twin is without much further inquiry into its state and application.
For our Industry 4.0 Lexicon committee, I do not want our scope to be infinite. Ideally, I want us to get our first draft done before we get too deep into summer. Therefore, our definition of the term digital twin may be simply to adopt this broad definition: "A digital representation of a physical thing." This may be unsatisfactory, since we want to facilitate common understanding and clearer communication. However, we may be well served to admit that this term cannot be further defined and to warn industry to put further scrutiny into its interpretation.
Don't be surprised if I revisit previous topics in the future. My first article in this newsletter was posted in January 2019. A lot has changed since then. We are in an ever-evolving world.