Digital Twin Series · Level 3 · PLC and controls
Virtual Commissioning of Machines
Can we test the whole control system on a virtual machine, before the real one exists?
Virtual commissioning uses a virtual model of the machine (mechanics, I/O and controls) to test and validate the complete automation system before the real machine is built or delivered. The same control code that will run on the real machine runs against the virtual one, so you find and fix errors early, which reduces commissioning time and risk. The cycle is design, simulate, test, validate, deploy. Below is a working virtual palletizing cell: start it, break it, and watch the test scorecard fill.
These are examples of tools in each role, not a recommendation. Which ones suit you depends on your PLC and robot brands, your budget and your model detail.
What you are looking at: a small PLC program (a sequence of states) controls a virtual conveyor, gripper and a robot. Boxes arrive on the conveyor, the sensor S1 stops the belt, the robot picks the box, places it on the pallet and returns. Six boxes fill the pallet. The guard door and the E-stop are safety inputs that stop everything. Press Start, then try the faults: a sensor that fails, a jam, a gripper with no vacuum. The scorecard ticks off each test as the program responds correctly. This is a teaching model, not a real safety program: real safety functions use certified safety hardware and are verified separately.
| Part of the system | Virtual (now) | Real machine (later) |
|---|
The point is the middle row group: the PLC program, the robot program and the HMI are the real thing in both columns. Only the machine around them is replaced by a model. Part 4 of this series compares software, processor and hardware in the loop in detail.
A scenario, not a prediction. The saving is the on-site commissioning time, times the share of it spent on software and control errors, times the share of those errors that the virtual model catches. Reports differ widely: one source says nearly two thirds of commissioning time goes on fixing software errors, and case studies report on-site commissioning time cut by about 70 to 75 percent and engineering time by as much as 30 percent. Another points out that fixing an issue during commissioning can cost up to 100 times more than fixing it in design. Your numbers depend on how complete the model is.
| Aspect | Virtual commissioning | Traditional commissioning |
|---|
Track the same numbers on a project with and without virtual commissioning, so the result is yours and not a vendor figure. Also track cycle time, safety compliance and how well the mechanical, electrical and controls teams worked together.
Figures are indicative and the virtual cell is a simplified teaching model. Validate your own control code and safety functions on your own equipment.