Digital Twin as a conceptual model

3.2 Digital Twin as behavior model

This chapter clarifies, what a "Digital Twin" means in the context of Selmo — and what explicitly not.

It creates a clear conceptual basis so that the Selmo model is correctly classified.

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The term "Digital Twin" — a need for clarification

The term "Digital Twin" is used today for very different things:

• 3D visualizations

• simulations

• virtual commissioning

• marketing representations

• data replicas of real machines

This multiplicity of meanings leads to misunderstandings.

Selmo uses the term deliberately restricted and precisely defined.

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What the Digital Twin is in Selmo

In Selmo the Digital Twin is:

A digital representation of the expected machine behavior.

Specifically this means:

• the twin describes states

• it describes expectations

• it describes monitoring

• it describes reactions to deviations

The Digital Twin in Selmo is:

• formal

• deterministically

• be verifiable

• explainable

It describes not the machine, but its correct behavior.

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What the Digital Twin in Selmo is not

The Selmo Digital Twin is not:

• a 3D model

• a physical simulation

• a virtual test system

• a substitute for real commissioning

• a marketing artifact

It does not replace:

• no mechanical design

• no safety analysis

• no validation of the real technology

Selmo models behavior, not geometry or physics.

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Relationship between reality and model

The Selmo Digital Twin has a clear relationship to the real machine:

• The real machine executes

• The Digital Twin describes what is correct

The twin:

• defines target states

• defines allowed transitions

• defines valid conditions

The real machine:

• is measured against it

• is monitored against it

• is diagnosed against it

Deviation means: Reality deviates from the modeled behavior.

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Digital Twin and determinism

Since the Digital Twin is modeled formally:

• there is a unique state at every point in time

• expectations are explicitly described

• reactions are defined

This means:

• no interpretation-dependent behavior

• no implicit assumptions

• no situation-dependent logic

The Digital Twin is deterministic — otherwise it would not be verifiable.

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Digital Twin as a basis for operation and diagnosis

The Digital Twin is the basis for:

• Process control

• state management

• model-based diagnosis

• consistent HMI display

• automatic documentation

HMI and diagnosis show:

• not "what is happening right now"

• but how reality relates to the model

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Distinction from simulation and virtual commissioning

Simulations answer:

• What happens if...?

The Selmo Digital Twin answers:

• What may happen?

• What is expected?

• What is correct behavior?

Both can complement each other, but are not the same.

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Role of the Digital Twin in the overall Selmo approach

The classification is clear:

PTF ↓ Digital Twin (behavior model) ↓ Selmo model (formalized) ↓ Real machine

The Digital Twin:

• originates from analysis (PTF)

• is formally described in the Selmo model

• remains valid during operation

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Summary

The Digital Twin in Selmo is:

• a formal behavior model

• not a simulation or visualization concept

• Basis for monitoring, diagnosis and responsibility

Selmo does not use the Digital Twin to show the machine — but to make it explainable.