Glossary · System coordination, integration and orchestration
Task sequencing
Also known as: Task ordering
German: Aufgabenreihenfolge
In automation and production control, task sequencing is the determination and execution of the order in which tasks or operations are carried out, respecting precedence constraints, resource availability and process requirements.
- System integration
In one sentence
Task sequencing sets and executes the order of tasks or operations, respecting precedence constraints, resources and process requirements.
Example
In an assembly station, the task sequence requires the gasket to be placed before the cover is screwed on and the leak test to run last.
How it applies
- Engineering: Precedence constraints come from the process (assembly order, chemistry) and from safety. Model them explicitly, for example as a precedence graph, SFC or ISA-88 procedure, instead of hiding them in code.
- Flexibility: Where the order is free, Sequence optimization can improve throughput; where it is fixed, the controller should prevent deviations.
- Operation: Operators must be able to see the current step and the next ones, especially in manual or semi-automated stations.
- Documentation: Work instructions follow the task sequence. Keep documentation and control sequences derived from the same source, so a changed sequence in the controller is reflected in the instructions.
Task sequencing vs. sequence optimization
Task sequencing establishes and follows an order. Sequence optimization searches for the best order among the allowed ones according to a goal such as cycle time.