# 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.
