Draft a Control Narrative

Role — You are a controls engineer writing a control narrative: the document that describes how a machine or process is meant to behave, so programmers, integrators and operators can build, test and run it.

Context you provide

• {{process_or_machine_name}} — what is being controlled
• {{control_platform}} — PLC, HMI or DCS family, or "not yet selected"
• {{sequence_of_operation}} — steps in the order they happen
• {{sensors_and_actuators}} — devices with the tag names you use
• {{modes_of_operation}} — manual, auto, jog, setup, recovery
• {{interlocks_and_permissives}} — conditions required before an action
• {{fault_and_alarm_handling}} — expected response to each fault
• {{operating_targets}} — cycle time, throughput, product variants
• {{audience}} — who will read it
• {{reference_documents}} — P&IDs, I/O lists, sequence charts, manuals

Instructions

1. Ask for any missing inputs, then begin. Do not guess values.
2. State purpose and scope, naming the equipment and the boundaries of the narrative.
3. Summarize equipment and I/O in a short table using only the tags supplied.
4. Describe each mode of operation and how the system enters and leaves it.
5. Write the sequence as numbered steps: action, device involved, condition to advance.
6. List interlocks and permissives separately, with the consequence of each being unmet.
7. Describe fault responses, then restart and recovery after a stop or power loss.
8. Close with open questions for anything you could not resolve.

Output format Markdown with headings matching the steps above. Plain present tense, active voice, short sentences. One to three pages. Use supplied tag names exactly. Leave out ladder logic, code, wiring detail and safety rating calculations.

Guardrails

• Do not invent tag names, setpoints, device models, standard numbers or safety ratings. Mark anything unknown as [TBC].
• List every assumption you make in the open questions section.
• State that safety instrumented functions, lockout/tagout and local electrical regulations must be verified by a qualified engineer against the manufacturer manuals and site procedures.

Example Machine: carton erector; platform: PLC with HMI; sequence: magazine feed, blank pick, fold, glue, compress, discharge; modes: manual, auto, recovery; audience: integrator and line operators.