Engineering
SDK & Integration
An inspection result that never reaches the line controller or the quality record is not an inspection.
Direct answer
How does a vision system integrate with a PLC and plant systems?
The vision system receives a trigger from a photo-eye, encoder or PLC output, returns a verdict over discrete I/O or a fieldbus protocol such as EtherNet/IP, Modbus TCP or PROFINET within the reject window, and writes a structured result record — timestamp, identifiers, per-check values, verdict and image reference — to a database or MES for traceability.
Acquisition layer
- Standards-based acquisition (GenICam-class GigE Vision / USB3 Vision devices) so hardware is replaceable.
- Custom interface and secondary-development work where a project requires it, including SDK-level camera control.
- Deterministic buffering with explicit behavior on overrun — dropped frames must be counted, never silent.
Result schema (illustrative)
- inspection_id
- UUID for the inspection event
- ts
- ISO-8601 timestamp with timezone
- station / recipe
- Station ID and active recipe + revision
- checks[]
- name, type, measured value, tolerance, verdict
- verdict
- pass | fail | no-read, with reason code
- image_ref
- Path or object key for the retained image
- model_version
- Populated when a learned model produced the verdict
Controls handshake
- Define worst-case decision time and the line's behavior on timeout before writing code.
- Fail-safe defaults: decide explicitly whether timeout means reject or pass, and document it.
- Heartbeat and health signals so the PLC knows the inspection is alive, not just quiet.
- Recipe changes driven by the PLC/MES work order rather than a manual selection at the HMI.
Fig. — Acquisition, inspection, controls and record layers
01 · Field I/O
- Part sensor / encoder
- Strobe controller
- Reject actuator
- Stack light / E-stop
02 · Acquisition
- Camera SDK / GenICam
- Hardware trigger
- Frame buffer + timestamp
03 · Inspection
- VSA Inspect pipeline
- Recipe + tolerance set
- Verdict arbitration
04 · Controls
- PLC handshake (digital / Ethernet)
- Heartbeat + fail-safe
- Reject confirmation
05 · Records
- Retained image store
- Quality record / MES
- Audit export
trigger → acquire → inspect → verdict (PASS / FAIL / NO READ) → PLC + reject → retained image & quality record
Data retention
Image retention is a storage and policy question: retain all fails plus a rolling sample of passes is a common compromise. Retention windows should be set by audit requirements, then costed, before commissioning.
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