Glossary · Automation fundamentals, platforms and components
Petri net
Also known as: Petri nets, Place/transition net
German: Petrinetze
In systems engineering and automation, a Petri net is a mathematical and graphical modeling language for discrete, concurrent systems, made of places, transitions, directed arcs and tokens. A transition fires when all its input places hold enough tokens, moving tokens to its output places.
- Automation components
- Standards
In one sentence
A Petri net models discrete, concurrent systems with places, transitions and tokens, making parallelism, synchronization and deadlocks analyzable.
Example
Engineers model two robots sharing one transfer station as a Petri net and prove that the station can never be occupied by both at once.
How it applies
- Engineering: Petri nets are used to analyze sequences with shared resources: reachability, deadlock freedom and boundedness can be checked formally before any code exists. GRAFCET and SFC (sequential function chart) are related in spirit: steps resemble places, and a Transition (SFC) resembles a Petri net transition.
- Verification: Formal analysis complements testing; it shows properties for all reachable states of the model, not only the tested ones. The model must still be validated against the real machine.
- Documentation: When a Petri net is part of the design evidence, keep it under version control with the code it describes and explain the notation briefly for readers who know only state diagrams.
Petri net vs. state machine
A State model has exactly one active state at a time (per region). A Petri net can hold tokens in several places at once, so it expresses Parallelism and resource sharing directly.