Setting Up SIMATIC/SIMOTION Hardware-in-the-Loop with SIMIT

Overview: Hardware-in-the-Loop vs Software-in-the-Loop for SIMATIC and SIMOTION

Hardware-in-the-Loop (HiL) is a virtual commissioning technique where a real programmable logic controller (PLC) executes the user program against a simulated plant, while software-in-the-loop (SiL) executes the entire controller virtually on a PC. Siemens documents both flows in entry 109758739 – "Application Example: SIMATIC/SIMOTION Virtual Commissioning with Hardware in the Loop". The reference example uses a real SIMOTION D controller and a SIMIT Unit as the only physical hardware; all other devices (drives, I/O, mechatronic components) are simulated inside SIMIT and the Mechatronics Concept Designer (MCD).

The same flow applies to a SIMATIC S7-1500 or S7-1200 controller. Siemens does not ship a TIA Portal reference project for HiL with SIMATIC; the recommended path for SIMATIC users is PLCSIM Advanced combined with SiL. This reference consolidates the published procedure, the underlying component contracts, and field-proven commissioning checks into a single engineering document.

HiL Architecture and Component Topology

The published HiL topology couples a real controller, a real SIMIT Unit, and virtual models running on engineering workstations. The signal flow is shown below.

Key contracts between blocks:

• Real controller ↔ SIMIT Unit: standard PROFINET or PROFIBUS DP. The SIMIT Unit terminates the fieldbus and exchanges I/O images with the SIMIT runtime on the engineering PC.
• SIMIT ↔ MCD: Functional Mock-up Unit (FMU 2.0) export from NX MCD loaded as a SIMIT-coupled model, or shared-memory coupling through the SIMIT MCD plugin.
• SIMIT runtime: simulates SINAMICS drives, SIMATIC I/O, third-party PROFINET devices, and software PLCs that act as slaves to the real controller.

Prerequisites: Software, Firmware, and Licensing

Match the installed component versions to those validated by Siemens for entry 109758739. A mismatch in the SIMIT version is the single most common source of coupling errors.

Step-by-Step: HiL Commissioning with SIMOTION D and SIMIT Unit

The procedure mirrors the published example. Each step lists the engineering tool, the action, and the verification check.

Step 1 – Wire the SIMIT Unit to the controller

1. Mount the SIMIT Unit (6AT8007-1AA10-0AA0) on a DIN rail next to the SIMOTION D rack.
2. Connect X1 (PROFINET channel 1) of the SIMIT Unit to PROFINET port X150 of the SIMOTION D using a Cat-6 / Cat-7 patch cord, both ends terminated in TIA standard pinout (green pair on pins 3/6).
3. Connect X2 (PROFINET channel 2) of the SIMIT Unit to the engineering PC; assign this NIC a static IP in the 192.168.0.0/16 range, separate from the controller subnet.
4. Apply 24 V DC (range 19.2–28.8 V) to terminals L+ / M on the SIMIT Unit. The RDY LED transitions from green flashing to solid green within 30 s.

Step 2 – Assign IP addresses in SCOUT / TIA Portal

Configure three IP subnets. Document the assignments in the project configuration report so commissioning engineers can re-create the bench.

Step 3 – Build the SIMIT virtual plant

1. Start SIMIT and create a new project. The project folder is the runtime container for all virtual components and the coupling configuration.
2. Import the GSDML file of the SINAMICS drives and the SIMOTION D into the SIMIT device library. The GSDML version must match the firmware; mismatches produce diagnostic code SF (red LED) on the SIMIT Unit.
3. Drop the SINAMICS S120 template, the SIMOTION D IO template, and the MCD coupling template onto the PROFINET subnet.
4. Bind the I/O addresses: in SCOUT, assign the SINAMICS telegram 105 to logical address 256..271; in SIMIT, map the same telegram to the SIMIT-side SINAMICS instance.
5. For MCD: in NX, select File → Export → Functional Mock-up Unit, set type to Co-Simulation 2.0, and tick SIMIT Compatible. Save the FMU and load it into the SIMIT project through the MCD coupling component.

Step 4 – Configure coupling in SIMIT

Open the SIMIT coupling editor and bind the SIMIT Unit X1 to the SIMIT runtime:

1. Couplings → PROFINET: select the SIMIT Unit from the discovered devices (the SIMIT Unit advertises itself with vendor ID 0x002A and device ID 0x0501). Set the watchdog time to 3000 ms for commissioning; lower to 200 ms only after stability is proven.
2. Couplings → MCD: point to the exported FMU file. The default step size is 1 ms; for kinematic models containing continuous collision detection, raise to 4 ms to keep the SIMIT cycle time below 80% of the PROFINET update time.
3. Compile the SIMIT project. The compiler reports unused tags as warnings; missing signals abort the compile and write the affected address in the build log.

Step 5 – Download the user program to the real controller

1. In SCOUT, connect online to the SIMOTION D over PROFINET (X150). Perform a full download (HW Config + user program + technology packages).
2. Set the CPU to RUN. The SIMOTION D issues PROFINET AR (Application Relationship) to the SIMIT Unit; the SIMIT Unit logs the AR establishment in its web interface (https://192.168.0.20).
3. Open the SIMIT online view. All simulated devices must show the green "connected" icon within 5 s of the controller going to RUN.

Step 6 – Execute tests and record results

1. Use SCOUT trace or TIA Portal trace to record real signals on the real controller. The trace timestamp is the controller clock – do not rely on SIMIT-side time for sequence validation.
2. For reproducible tests, drive the MCD model from a SIMIT test sequencer (.seq file). Sequences support WaitUntil, SetTag, CompareTag, and LogMessage primitives.
3. Export the trace as CSV for diff comparison against the FAT (Factory Acceptance Test) protocol.

Alternative: HiL with SIMATIC S7-1500

Siemens does not publish a TIA Portal reference project for SIMATIC HiL. The official guidance is to switch to SiL with PLCSIM Advanced when the goal is controller code validation. If a real SIMATIC CPU must be exercised against a virtual plant, the configuration is structurally identical to the SIMOTION flow above:

1. Install the same SIMIT version, the same SIMIT Unit, and the same Virtual Commissioning license.
2. In TIA Portal, configure the S7-1500 PROFINET interface identically – same IP, same device name, same I/O addresses.
3. Compile and download the S7-1500 user program. The PROFINET AR terminates at the SIMIT Unit; from the S7-1500 perspective the SIMIT Unit appears as a real PROFINET IO device.
4. Validate that no GSDML version skew exists. The S7-1500 PROFINET stack rejects an AR whose GSDML major version differs from what the project expects; this surfaces as SF on the controller and a PROFINET IO controller diagnostic entry Channel diagnosis - Error appears 1: Channel-specific diagnostics, channel 0.

Alternative: SiL with PLCSIM Advanced

For pure controller code validation, the recommended path is PLCSIM Advanced V2.0 SP1 or later. PLCSIM Advanced virtualises the S7-1500 / ET 200SP CPU and exposes a TCP-based API (default port 102 for ISO-on-TCP) so SIMIT can couple to the virtual instance.

1. Install PLCSIM Advanced and start the PLCSIM Advanced Manager. Create a virtual instance with the same article number as the target CPU (e.g. 6ES7516-3AN02-0AB0 for 1516-3 PN/DP).
2. Set the instance to Power on with the option Enable OPC UA server if OPC UA coupling to SIMIT is desired.
3. In TIA Portal, set the PG/PC interface to PLCSIM Advanced TCP/IP and download the project. The download transport runs over the local TCP socket, not PROFINET.
4. In SIMIT, use the PLCSIM coupling instead of the PROFINET coupling. The PLCSIM coupling transfers tag values via shared memory; cycle times are typically 10–50 ms, sufficient for PLC code but not for high-dynamic drive commissioning.

Verification Checklist

Run this checklist after the first RUN transition and again before each test sequence release. Any failed item blocks the next milestone.

Troubleshooting Matrix

Most HiL bench failures fall into one of the categories below. Use the table as a triage guide; the controller-side diagnostic buffer and the SIMIT Unit web interface provide the corroborating evidence.

Performance Sizing and Cycle Time Math

The HiL bench is real-time only inside bounded windows. Use the formulas below to size the bench before commissioning.

PROFINET IRT update time t_PN is set in TIA Portal / SCOUT under PROFINET interface → Real-time settings → Send clock. Default is 1 ms.

SIMIT cycle time t_SIMIT should be a submultiple of t_PN:

The SIMIT Unit buffers one PROFINET cycle. The maximum tolerable coupling latency is:

where t_MCD is the MCD solver step. For a 1 ms PROFINET cycle, 0.5 ms SIMIT cycle, and 4 ms MCD step:

This satisfies the SINAMICS S120 PROFINET watchdog default of 12 ms. If a tighter drive cycle is required, lower t_MCD by simplifying the MCD kinematic chain (fewer collision bodies, lower mesh density).

Migration Notes: From SiL to HiL

Migrating an existing PLCSIM Advanced SiL bench to a real-controller HiL bench requires three changes:

1. Replace the PLCSIM coupling in SIMIT with the PROFINET coupling pointing at the SIMIT Unit X1.
2. Download the project to the real controller instead of the virtual instance. The user program and tag list remain unchanged.
3. Update the FAT test protocol to indicate that the bench is now HiL – the trace timestamps are wall-clock from the controller, not from the SIMIT runtime, and the trace CSV header must be updated accordingly.

FAQ