Digital commissioning lets engineers test a warehouse automation system before the real equipment is fully built. A digital twin of conveyors, scanners, storage racks, shuttles, sensors, and actuators is connected to the same PLC logic that will run the physical system. This matters because errors in material flow, timing, and safety interlocks can be found early, when changes are cheaper and safer.
In logistics, even small control problems can cause jams, missed scans, downtime, and delayed orders.
Key Facts
- PLC scan cycle time is the time needed to read inputs, execute logic, and update outputs.
- Throughput = units processed / time, such as packages per hour.
- Cycle time per item = total operating time / number of completed items.
- Availability = uptime / (uptime + downtime).
- OEE = availability x performance x quality.
- A digital twin links simulated physics and material flow to real control logic using signals such as sensors, motors, actuators, and faults.
Vocabulary
- Digital commissioning
- Digital commissioning is the process of testing and validating automation controls using simulation before running the real machine or system.
- PLC
- A programmable logic controller is an industrial computer that reads input signals, runs control logic, and commands outputs such as motors and valves.
- Digital twin
- A digital twin is a virtual model of a real system that behaves like the physical system and can exchange data with control software.
- AS/RS
- An automated storage and retrieval system uses controlled machines such as shuttles, cranes, or lifts to store and retrieve items from racks.
- Interlock
- An interlock is a control rule that prevents an action unless required safety or process conditions are satisfied.
Common Mistakes to Avoid
- Treating the simulation as only a 3D animation is wrong because useful digital commissioning must include signals, timing, control logic, faults, and material flow behavior.
- Ignoring PLC scan time is wrong because fast sensor events or short packages may be missed if the logic updates too slowly for the conveyor speed.
- Testing only normal operation is wrong because warehouse systems must also handle jams, blocked sensors, emergency stops, scanner failures, and full buffer zones.
- Assuming higher conveyor speed always increases throughput is wrong because bottlenecks at scanners, diverters, lifts, or AS/RS aisles can limit the whole system.
Practice Questions
- 1 A conveyor processes 720 packages in 2 hours. Calculate the throughput in packages per hour and the average time per package in seconds.
- 2 A PLC has a scan time of 20 ms. A photoelectric sensor is blocked by a package for 120 ms as it passes. How many PLC scans occur during the blocked signal?
- 3 A simulated warehouse shows packages accumulating before a barcode scanner even though the upstream conveyor is running correctly. Explain two possible causes and describe how digital commissioning could help test them before installation.