Finite State Machines Using Structured Text (ST) in CODESYS V3.5

Finite State Machines Using Structured Text (ST) in CODESYS V3.5

Finite State Machines in Structured Text (ST) in CODESYS V3.5 for Complex Technological Cycles

A practical guide to designing reliable and deterministic control algorithms in ST. Based on IEC 61131-3, ISA-88, and PackML. Covers Moore and Mealy models, hierarchical state machines (HFSM), parallel branching (Fork/Join), Hold/Resume mechanisms, Manual/Step/Auto modes, diagnostics, and tracing.

Who it´s for: PLC programmers, automation engineers, commissioning specialists, students, and teachers.

Inside:

Theory: PLC task cycle, dangers of boolean flags, formal models, transition matrices.

ST practice: ENUM + CASE, three-phase state lifecycle (OnEntry/OnDo/OnExit), watchdog timers, FAULT branch.

Industrial standards: PackML, ISA-88.

Comparison of procedural approach and OOP State pattern.

Practical section:

5 lab projects: positioner, pump station, chemical reactor, sorting conveyor, packaging cell.

3 engineering tasks: cleanroom airlock, weigh-batch mixer, freight lift.

4 typical anti-patterns with analysis and fixes.

Appendices: universal FSM template, SFC→ST mapping table, CODESYS optimization, answers to review questions.

Important: code examples require adaptation and testing. Safety functions must be implemented with certified hardware.

Additional information:

Format: PDF. Language: Russian.