The Selmo overall model

The fundamental structural principle

Selmo describes a machine not as code, but as a hierarchically constructed behavior model.

The structure is clearly layered:

Plant └─ Hardware Zone └─ Sequence └─ Zone

These levels are:

• clearly separated from each other

• each uniquely responsible

• intentionally kept simple

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Plant

The Plant represents the entire machine or plant.

It is:

• the top structural level

• holder of global states

• place for plant-wide monitoring (e.g. CMZ)

The Plant describes no sequence. It forms the frameworkin which all other elements exist.

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hardware zone

A hardware zone encapsulates a real plant section.

It is responsible for:

• modes of operation (Manual / Automatic)

• automatic enablement

• start and stop logic

• higher-level responses to errors

The hardware zone:

• contains multiple sequences

• knows no process logic

• does not decide what happens, but whether is allowed to happen

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Sequence

A Sequence is a functional process responsibility.

It describes:

• a self-contained process

• as a deterministic state machine

• with clearly defined start and end behavior

Typical examples:

• Clamp

• Machine

• Inspect

• Release

One task → one sequence.

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Zone

A Zone provides the Connection to real technology .

It:

• encapsulates signals

• gives them meaning

• is uniquely diagnosable

Zones are:

• always part of a sequence

• carriers of monitoring and safety

• the smallest meaning-bearing unit in the model

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Layer

Each sequence is layered across multiple Layer .

These layers deliberately separate different aspects:

Logic layer

• describes the process

• states and transitions

• no technology

system layer

• links states with zones

• defines expected behavior

• implements bit-control

Parameter layer

• contains times, positions, repetitions

• no logic, no states

Layers separate thinking from implementation and prevent mixing of responsibilities.

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Interaction of the elements

All elements together form a complete picture:

• The Plant defines the overall framework

• The hardware zone regulates operation and authorization

• The Sequence describes the process

• The Zone ties down technology

• The Layer structure the description

Thus machine behavior is:

• explicitly described

• assessable at any time

• fully traceable

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Classification

This chapter is intentionally overview-like.

The following chapters:

• delve into each level individually

• explain behavior, monitoring and operation in detail

The overall model is the map. The next chapters explain the individual places.