📘 Technical manual chapter

Selmo operating and control concept – structure, function and safety

(according to ISO/IEC 82079-1: Information structure for technical instructions)

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.

---

2. Target audience

This document is intended for:

• machine operators and plant operators,

• maintenance personnel and service technicians,

• inspectors, auditors and CE officers,

• integrators and software engineers working with Selmo Studio.

---

3. Overview of the system principle

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

• The control works with states instead of individual commands.

• At any time only one state 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.

---

4. Control architecture

4.1 Structure of the layers

The control system is hierarchically divided into:

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

2. Hardware zones (HWZ) – physical areas with independent control logic (e.g. stations or modules).

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

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

4.2 Sequence Engine

The sequence engine is the process and clock generator. It continuously checks the 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.

---

5. Zone level and behavior

5.1 Definition

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

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

5.3 Operants (Bit-Control)

Each zone has an assigned function in every 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 Selmo Studio in the System Layer defined.

---

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 functions are an integral part of the standard; no additional programming required.

---

7. Operation via the HMI

The user interface shows:

• the active state,

• the active zones with color coding,

• plain-text HMI messages,

• error and diagnostic lists.

Color coding:

• Green = AutoRelease

• Red = Interlock

• Yellow = Warning

• Gray = Manual Mode

---

8. Behavior in case of malfunctions

In case of errors the system reacts automatically:

1. The sequence stops.

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 sequence continues.

This ensures that every fault is clearly localized and handled safely.

---

9. Documentation and traceability

The Selmo model documents itself:

• Every state, every zone and every operand are stored in the system.

• HMI texts and diagnostics are generated automatically.

• Changes are versionable and auditable.

This allows the control to meet the requirements for traceability and CE conformity.

---

10. Summary

The Selmo concept defines a clear, traceable and safe control structure:

• formal state description (deterministic),

• standardized zone logic,

• integrated safety functions,

• automatic diagnostics and documentation.

For operators this means: transparent processes, clear messages, safe operation. For the manufacturer: standards-compliant documentation and uniform quality standard.

---

11. Reference

This concept is based on the Selmo standard according to the development guidelines of Selmo Technology GmbH – Sequence Logic Modelling System.