> For the complete documentation index, see [llms.txt](https://infosys.selmotech.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://infosys.selmotech.com/selmo-solution/selmo-solution-en/selmo-documentation-of-the-logic/sdea-model/standards-compliant-system-description-sdea.md). # Standards-compliant system description - SDEA ### 📄 **Standards-compliant system description: Selmo automaton (extended deterministic state machine)** #### 1. **Basic model** The control system is based on an **extended deterministic finite automaton (DFA)** according to the principle of a **Moore machine**. This means: * The control is **state-based**. * All outputs are **defined exclusively by the active state**. * State transitions occur **deterministic**, i.e. uniquely and fully traceable. Each state describes a logically self-contained step in the machine's behavior. *** #### 2. **Functional components of the automaton** The automaton is defined by the 8-tuple: S=(Z,Σ,Γ,δ,λ,z0,B,M) | Symbol | Description | | ------ | --------------------------------------------------------------- | | Z | Finite set of modeled states | | Σ | Input set from sensors, buttons, feedback signals | | Γ | Output set to actuators (e.g. valves, motors) | | δ | State transition function taking inputs and memory into account | | λ | State output function according to Moore | | z0 | start state | | B | Bit control matrix with signal behavior per state and zone | | M | Set of mem-zones (internal state memory) | *** #### 3. **Bit control matrix (system layer)** The bit control matrix defines the behavior of each zone in the respective state: * `0`: No requirement ("Don't care") * `S`: Sequence check → expected action or reaction * `I`: Interlock → safety-relevant monitoring requirement with stop * `M`: Monitoring → safety-relevant monitoring requirement with documentation A transition to the subsequent state is only permitted if: * all `S`-zones are fulfilled * no `I`-zone reports a deviation * no errors exist in higher-level Constantly Monitoring Zones (CMZ) *** #### 4. **Zone structure** Each zone is uniquely typed: * **Input zone**: Monitoring input signals * **Output zone**: Actuation of outputs = actuators without feedback * **In-out zone**: Combination of control and feedback * **Mem zone**: Internal state memory for controlling dependent sequences The zones are connected to the states via a systematic matrix (bit control). This creates a complete behavioral model of the machine. *** #### 5. **Memory function (mem-zones)** Mem-zones serve as internal **memory function**: * They are explicitly set or reset in a state with `S` . * They can be used in transition conditions and logic paths. * Their status is deterministically included in the sequence model. * Used for synchronous sequence control to ensure the sequence occurred or to prevent incorrect state *** #### 6. **Error detection and state monitoring** The system detects **deviating signal states automatically**: * `I`-zones monitor safety-relevant signals → lead to automatic stop with fault diagnosis in case of deviation * `S`-zones display operator guidance in the HMI → state waits actively until all conditions are met * **Error messages are generated automatically**, localized and displayed in the HMI *** #### 7. **Advanced safety functions (standard Selmo)** In addition to the base logic, the following standard functions are integrated in the model: * **CMZ (Constantly Monitoring Zone):** permanent signal monitoring, independent of state * **MXIC (Manual Cross Interlock):** safe release conditions for manual movements in manual operation * **Parameter layer:** modeled, parameterizable values (e.g. times, counts, thresholds) *** #### 8. **Normative classification** The deterministic, formalized structure of the Selmo automaton supports a traceable and risk-minimized machine control in accordance with: * **EN ISO 13849-1 (Safety-related parts of control systems)** * Function monitoring (e.g. interlock, CMZ) * Fault detection and defined reactions * **IEC 61508 / IEC 62061 (Functional safety)** * State modeling for safe control sequences * Determinism, testability and verifiability * **IEC 61131-3 (Programming standard)** * Separation of control (state) and monitoring (bit control) * **Machinery Regulation (EU)** / CE conformity: * Traceable, testable control behavior * Automatically producible documentation through formal modeling *** #### 9. **Advantage of formalization** The complete formal definition enables: * **Automatic code generation** * **Automatic validation and simulation** * **Complete technical documentation** * **Reduction of human programming errors** * **Increased traceability in terms of product liability** --- # Agent Instructions This documentation is published with GitBook. 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