What is virtual commissioning?
Virtual commissioning is the practice of testing control software for PLCs, robots and HMIs against a simulated model of the machine or plant, so that errors are found and fixed before physical commissioning begins. The controller behaves as if it were driving a real installation, while sensors, actuators, conveyors and process behaviour all come from a simulation model. Engineers can therefore test in the office while the machine is still being assembled in the workshop. German practitioners call it virtuelle Inbetriebnahme (VIBN).
🧠 How does virtual commissioning work?
Every virtual commissioning set-up has three parts:
- The control system — the actual PLC program, robot program and HMI screens, exactly as they will later run in the plant
- The plant model — a simulation of mechanics, sensors, drives and material flow, often a 3D model built from CAD data
- The coupling — the exchange of inputs and outputs between controller and model, via a software bus, OPC UA or an emulated fieldbus
The model reacts to controller outputs (motor on, valve open) and returns the matching inputs (limit switch reached, level rising). Sequences, interlocks, fault handling and HMI operation can thus be tested without a real product or a real machine. The model is an early form of a digital twin.
🔧 Which test levels exist: MIL, SIL and HIL?
The VDI/VDE 3693 guideline and most tools distinguish test configurations by how many “real” components sit in the loop:
| Level | Controller | Plant | Typical use |
|---|---|---|---|
| MIL (model-in-the-loop) | Model of the control logic | Simulation model | Checking concepts and algorithms early in design |
| SIL (software-in-the-loop) | Real PLC program on a virtual PLC, e.g. S7-PLCSIM Advanced or a soft PLC | Simulation model | The bulk of software testing, on a laptop or server |
| HIL (hardware-in-the-loop) | Real PLC hardware with real fieldbus | Real-time simulation model | Timing, fieldbus configuration and safety PLC behaviour |
Siemens S7-PLCSIM Advanced, for example, emulates S7-1500 CPUs with up to 16 instances per PC, communicates over an internal softbus or TCP/IP and offers an API that lets a simulation tool synchronise virtual time. In HIL the model must run deterministically in step with the controller’s cycle time; specialised systems reach cycles from 1 ms.
🛠️ Which tools are used for virtual commissioning?
| Vendor | Tool | Strength |
|---|---|---|
| Siemens | NX Mechatronics Concept Designer (MCD) | Physics-based 3D machine model linked to TIA Portal |
| Siemens | Tecnomatix Process Simulate | Robot cells and offline robot programming |
| Siemens | SIMIT | Process industry, signal and device simulation, operator training |
| Rockwell Automation | Emulate3D (acquired in 2019) | Material flow, logistics, Logix emulation |
| Beckhoff | TwinCAT 3 EtherCAT Simulation (TE1111) | Emulating EtherCAT slaves on a simulation PC |
| ISG | ISG-virtuos | Vendor-neutral, real-time MIL/SIL/HIL |
| Visual Components (KUKA) | Visual Components | Factory layout, robots from many brands |
| Mitsubishi Electric | MELSOFT Gemini | 3D simulation linked to GX Works3 |
For exchanging simulation models between tools, the open FMI standard (Functional Mock-up Interface) from the Modelica Association matters. A model is packaged as an FMU and can be loaded into another environment for co-simulation. FMI 3.0 was released in May 2022; FMI as a whole is supported by more than 170 tools.
🎯 What are the benefits of virtual commissioning?
- Shorter on-site commissioning — in one documented material-handling project, on-site time fell to a quarter of the planned time; other studies report 15 to 25 per cent shorter total installation time and up to half the on-site man-hours
- Earlier bug detection — a sequence error costs minutes in the office and hours on site with an installation team waiting
- Safe testing of edge cases — an emergency stop mid-cycle, a failed sensor or a jammed product can be repeated in simulation without risk
- Parallel engineering — software and mechanics are developed at the same time rather than one after the other
- Training — operators and maintenance technicians practise on the HMI before the machine even exists
Virtual commissioning does not replace functional safety validation on the real machine: safety functions must always be verified physically.
🔄 How does virtual commissioning relate to FAT and SAT?
Virtual commissioning moves testing earlier in the project. A virtual FAT lets the customer accept the control software against the model well before the machine is built. The physical FAT at the machine builder and the SAT on site then become shorter, because the software has largely been debugged already.
In the process industry the same idea has been common for decades as the operator training simulator (OTS): a dynamic process model connected to the DCS, on which operators rehearse start-ups, shutdowns and upsets. The difference lies in the model: machine building focuses on kinematics and material flow, process plants on mass balances, pressure, temperature and reaction kinetics.
📐 How detailed should the simulation model be?
| Fidelity level | What is simulated | Suitable for |
|---|---|---|
| Signal level | I/O is simply looped back (output on → input on after x ms) | I/O checks, simple sequences |
| Device level | Behaviour of cylinders, motors, variable-speed drives and valves | Fault handling, interlocks, diagnostics |
| Physics / 3D level | Kinematics, collisions, gravity, product flow | Robot paths, cycle time, conveyor logic |
| Process level | Dynamic mass and energy balances | OTS, control loops, start-up procedures |
The rule of thumb is as simple as possible, as detailed as necessary. An over-rich model costs more modelling time than it saves during commissioning.
🏭 Step by step: virtual commissioning of a packaging machine
- Define the scope — choose which modules (infeed, filling, capping, labelling) and which test cases will be tested virtually
- Build the model — import the CAD data, add kinematics, sensors and product flow; reuse component models from a library
- Map the I/O — connect the symbols from the PLC project one-to-one to the model, preferably generated from the I/O list
- SIL test — run the PLC program on a virtual PLC and test manual mode, automatic mode, format changeovers and faults
- Include the HMI — connect the real HMI runtime and walk through alarms and operating flow with the customer
- HIL test — use the real PLC and fieldbus to check timing and drive configuration
- Virtual FAT — the customer accepts the software against the model; deviations go into the issue log
- Maintain the model — keep it current for later modifications; in brownfield retrofits, a virtual test beforehand is especially valuable because downtime is expensive
🔐 Why does security matter in virtual commissioning?
Simulation models and engineering data are sensitive assets. A complete model contains the machine design, the control logic, I/O lists and often IP addresses and network configuration: a blueprint for competitors and attackers alike. HIL set-ups also sometimes connect real controllers to office networks. Points to watch:
- Restrict access to projects and manage models in version control with logging
- Separate networks — keep simulation PCs and engineering stations off the production network unless managed
- Protect integrity — the software loaded into the real PLC after the virtual test must demonstrably be the same version that was tested
- Share with suppliers through controlled environments rather than e-mail or USB sticks
❓ Frequently asked questions
What is the difference between virtual commissioning and a digital twin?
Virtual commissioning is an application: testing control software against a simulation model before the physical start-up. A digital twin is broader and follows an asset throughout its life cycle, often fed with live data. The model built for virtual commissioning is frequently the starting point of a digital twin.
Which guideline describes virtual commissioning?
The German guideline VDI/VDE 3693 describes virtual commissioning. Part 1 (2016, revised in 2025) defines terms, model types and test configurations, while Part 2 (2018) explains how a company introduces virtual commissioning step by step. The open FMI standard is used for exchanging simulation models between tools.
What is PLCSIM Advanced?
S7-PLCSIM Advanced is Siemens software that emulates an S7-1500 PLC on a Windows PC. The real PLC program from TIA Portal runs on it and exchanges data through an API, softbus or TCP/IP with simulation tools such as NX MCD, Process Simulate or SIMIT. That makes PLCSIM Advanced the standard basis for software-in-the-loop virtual commissioning in Siemens projects.
How much time does virtual commissioning save?
The savings from virtual commissioning vary widely by project. In one documented case, on-site time fell to a quarter of the plan; other studies cite 15 to 25 per cent shorter installation time or half the on-site man-hours. Against that stands the effort of building the model, which pays off most for repeatable machines and complex plants.
Is virtual commissioning worthwhile for small machines?
For small, simple machines, virtual commissioning at signal level is often sufficient and quick to set up. A full 3D model only pays off for complex sequences, robots or series-built machines where the model is reused. Libraries of standard components lower the barrier considerably.
Does virtual commissioning replace the FAT?
No, virtual commissioning does not replace the FAT, but it makes it shorter and more predictable. Mechanics, wiring and safety functions still have to be tested on the real machine. A virtual FAT can, however, bring most of the software acceptance forward.
📌 In summary
Virtual commissioning tests PLC, robot and HMI software against a simulation model, making the real start-up shorter, safer and more predictable. Choose the fidelity level and the MIL, SIL or HIL set-up that fits the project, and treat the model as sensitive engineering property.