Selmo operation and control concept (md)

Selmo operating and control concept

Structure, function and safety

(Basis for operating instructions according to ISO/IEC 82079-1)

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1. Purpose of the document

This chapter describes the machine's operating and control concept, whose control system is based on the Selmo method (Sequence Logic Modelling) It serves to explain the logical mode of operation, the safety mechanisms and the interaction between operator, machine and control.

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2. Target audience

This documentation is intended for:

• Machine operators and plant operators

• Maintenance personnel and service technicians

• Inspectors, auditors and CE officers

• Integrators and software engineers who work with Selmo Studio

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3. Overview of the system principle

The machine control follows the principle of deterministic sequence control (Selmo SEQ).

Key features:

• The control works with states instead of individual commands.

• At any time only one state is active.

• Transition to the next state occurs only when all defined conditions are met.

This structure ensures reproducible, traceable and safe behavior of the machine.

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4. Control architecture

4.1 Structure of the layers

The control is hierarchically structured into:

1. Plant (entire system) – describes the logical overall structure of the machine.

2. Hardware zones (HWZ) – physical areas with their own control logic (e.g. stations, modules).

3. Sequences (SEQ) – sequence controls within an HWZ.

4. Zones (Zone Types) – logical function blocks that map real signals or virtual functions.

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4.2 The switching engine (Sequence Engine)

The switching engine is the sequence and clock generator. It continuously checks three core conditions:

Input quantity	Meaning
AR (Auto Release)	Automatic release active
¬I (No Interlock)	no safety violation
ΣS (Sum of Sequence Checks)	all ongoing actions completed

Only when AR = 1 ∧ ¬I ∧ ΣS = 0, the state change occurs. This ensures that the sequence is only continued in a safe state.

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5. Zone level and behavior

5.1 Definition

Zones are standardized switching elements that bundle actions and feedback. They establish the connection between logic and physics.

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5.2 Zone types

Type	Description	Example
IN	Input signal	Start button, sensor
OUT	Output signal	Lamp, valve
IN_OUT	Action + feedback	Cylinder, axis, calculation
MEM	Memory zone	Software status, parameter

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5.3 Operants (Bit-Control)

Each zone has an assigned function in each state.

Operant	Meaning	Effect
S (Sequence Check)	Action active	waiting for feedback
I (Interlock)	Safety monitoring	stops sequence in case of error
M (Monitoring)	Diagnostic monitoring	reports notice without stop
0 (Don’t Care)	inactive	no function in this state

This assignment is defined in the System Layer in Selmo Studio.

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6. Safety functions

The system contains several standardized safety mechanisms:

1. Interlock function – detects safety violations and stops the sequence.

2. PairCheck – monitors contradictory feedback (e.g. cylinder front/back).

3. MXIC (Manual Cross Interlock) – prevents unsafe hand movements.

4. Monitoring (M) – provides diagnostic messages without interrupting the process.

All safety functions are an integral part of the Selmo standard – no additional programming required.

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7. Operation via the HMI

The user interface shows:

• the active state

• active zones with color coding

• plain text HMI messages

• error and diagnostic lists

Color coding:

Color	Meaning
🟩 Green	AutoRelease active
🟥 Red	Interlock
🟨 Yellow	Warning
⚪ Grey	Manual Mode

The HMI also serves as an operating interface, diagnostic tool and documentation view.

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8. Behavior in case of malfunctions

If a zone reports a deviation:

1. The sequence is automatically stopped.

2. The affected zone is marked in red.

3. An error message with cause appears on the HMI.

4. After error correction and release (AR = 1) the control resumes the sequence.

This ensures that no uncontrolled movements occur and that every error can be localized.

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9. Documentation and traceability

The Selmo structure documents itself:

• Every state, every zone and every operant are stored in the model.

• HMI texts and diagnostics are generated automatically.

• Changes are versionable and auditable.

In this way, the control meets the requirements for traceability, CE conformity and quality assurance.

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10. Summary

The Selmo structure defines a clearly traceable and safe control system:

• formal state description (deterministic)

• standardized zone logic

• integrated safety functions

• automatic diagnostics and documentation

Advantages:

• Transparent processes

• Unambiguous error messages

• Safe operation

• Uniform structure for all systems

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11. Reference

This concept is based on the Selmo standard according to the development guidelines of Selmo Technology GmbH – Sequence Logic Modelling System (SEL_SEQ_STD-DE-V3.0)

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Note for documentation editors: This text is the static section of the operating manual. Dynamic parts (state descriptions, HMI lists, sequence flows) are automatically supplemented from the model.