Selmo – Evidence for formal safety, documentation and standards compliance

Purpose of the document

This documentation clearly and verifiably demonstrates that the application of the Selmo standard in the modeling, control and documentation of machines:

• transparently documented and assessed complete function description enables,

• the monitoring of safety-relevant processes in a structured way,

• and thereby a legally and standards-compliant implementation is supported.

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1. Documentability and traceability

Selmo describes every machine model-based, in a clear structure:

PLANT
└── HWZ (hardware zones)
    └── SEQ (sequences)
        └── Zones (input / output / in-out / mem)

Every state, every signal assignment and every safety function is derivable from the model. This automatically produces:

• a complete signal directory (IO ↔ Zone ↔ Function),

• a modeled sequence logic (states, transitions, conditions),

• a documented safety structure (CMZ, interlock, MXIC),

• a verifiable restart behavior (reset, synchronization),

• a change log (Model_ChangeLog.csv).

This documentation is machine-readable, version-secure, and revision-capable.

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2. Formal safety of the functional logic

The model structure ensures that:

• every Zone has a documented behavior in every state (0, S, i),

• Interlocks lead to immediate reaction upon violation,

• CMZ signals are continuously monitored,

• MXIC releases allow manual operation only under safe conditions,

• every step is explained by modeled state transitions is explainable.

The Selmo model replaces free PLC logic with:

• deterministic state machines,

• fully described signal behaviors,

• model-based diagnostics and error display,

• automatically derivable restart conditions.

As a result, every action, reaction, restriction or diagnosis is explainable and verifiable.

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3. Monitoring and self-check

During operation the model automatically checks:

element	effect in case of deviation
i (interlock)	automatic stop, red HMI indication
S (sequence check)	waiting state with clear operator guidance
CMZ	immediate lock (SEQ, HWZ or PLANT)
MXIC	prevention of manual movement with explanation

Every violation is displayed in the HMI, localized and documented – including text and background color. Operator, commissioning engineer and inspector can recognize at any time:

• What the model expects

• Whether the real system meets the state

• Whether a safety violation exists

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4. Standards and legal compliance

The application of the Selmo standard meets the requirements of the following standards and guidelines:

Standard / regulation	Fulfillment by Selmo
ISO 12100	Modeled operating modes, reset behavior, state management
EN ISO 13849-1/2	Structured safety behavior (CMZ, MXIC, interlock)
IEC 62061	Verifiable safety functions in sequence structure
IEC 61508	Functional safety through deterministic model behavior
IEC 61131-3	Generated code fully standard-compliant (ST / GVL / FB)
Machinery Regulation (EU)	Technical documentation and diagnostic behavior model-driven
Product liability law	Derivability of all functions from verified models

Thus Selmo is not only a programming technology – but a safety-oriented behavior model, which is automatically linked with CE-relevant evidence.

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5. Legal and audit security

By applying the Selmo model:

• a traceable functional logic is created,

• every safety-relevant function is verifiable by model technique,

• a complete technical documentation is automatically generated,

• an independent third party can analyze the function, reaction and limits of the system.

These properties secure: ✅ the legal certainty for manufacturers, ✅ the transparency for customers / operators, ✅ the acceptance assurance with authorities / auditors.

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Conclusion

The Selmo method is more than a modeling approach – it is a formalized structure for safe, documented, traceable machine control. It makes control systems:

• understandable,

• testable,

• maintainable,

• legally compliant,

• and future-proof.

📌 Compliance with the Selmo structure is an active contribution to risk reduction, quality assurance and compliance with applicable legal regulations.