SimInTech to Python

Integrate SimInTech models into Python by running the project from a script and exchanging data through files. Below is a quick start guide and a working example.

Quick start

1. Prepare a SimInTech project (.prt/.xprt) with the following blocks:
2. reading the input signal from a file (e.g., sit_in_1.dat),
3. writing the output signal to a file (e.g., sit_out_1.dat).
4. Find the path to the SimInTech executable mmain.exe (usually C:\\SimInTech64\\bin\\mmain.exe).
5. Generate the input signal in Python and save it to sit_in_1.dat.
6. Run the SimInTech project from Python: mmain.exe <path_to_project> /run /exitonstop.
7. Read the output file in Python and plot the results.

Supported platform

The examples below are designed for Windows, since SimInTech is a Windows application.

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Full Python example

from __future__ import annotations
import subprocess
from pathlib import Path
import numpy as np
import matplotlib.pyplot as plt

from tensoraerospace.utils import generate_time_period, convert_tp_to_sec_tp
from tensoraerospace.signals.standard import unit_step


def run_simintech(sit_bin: Path, project: Path, extra_args: list[str] | None = None, timeout_sec: int | None = 120) -> None:
    """Run a SimInTech project with the /run /exitonstop flags.

    - sit_bin: path to mmain.exe
    - project: path to .prt/.xprt
    - extra_args: additional command-line arguments
    - timeout_sec: timeout for completion, in seconds
    """
    args = [str(sit_bin), str(project), "/run", "/exitonstop"]
    if extra_args:
        args.extend(extra_args)

    completed = subprocess.run(
        args,
        check=False,           # we will show a clear error below
        capture_output=True,   # capture stdout/stderr in case of errors
        text=True,
        timeout=timeout_sec,
        shell=False,
    )

    if completed.returncode != 0:
        raise RuntimeError(
            "SimInTech exited with an error "
            f"(code {completed.returncode}).\nSTDOUT:\n{completed.stdout}\nSTDERR:\n{completed.stderr}"
        )


if __name__ == "__main__":
    # Paths: adjust for your installation/project
    sit_bin = Path(r"C:\\SimInTech64\\bin\\mmain.exe")
    project = Path(r".\\lsu2.xprt")  # project in the current folder

    # Generate input signal: 1 deg step at t0=0.5 s, dt=0.01 s
    dt = 0.01
    tp = generate_time_period(tn=100, dt=dt)                 # discrete ticks
    tps = convert_tp_to_sec_tp(tp, dt=dt)                     # time in seconds

    # unit_step returns an array of values (in radians when output_rad=True)
    # Form the shape [channels, time] -- here one channel
    ref = unit_step(degree=1, tp=tp, time_step=0.5, output_rad=True)
    reference_signals = np.reshape(ref, (1, -1))

    # Write the input file. SimInTech often expects values line-by-line/component-wise.
    # Check the format of your project. In the simplest case -- a single column of values.
    in_file = Path("sit_in_1.dat")
    np.savetxt(in_file, reference_signals.ravel(), fmt="%.6f")

    # Run the simulation
    run_simintech(sit_bin=sit_bin, project=project)

    # Read the result (configure the output file path and format in the SimInTech project)
    out_file = Path("sit_out_1.dat")
    if out_file.exists():
        y = np.loadtxt(out_file, dtype=float)

        # Plot the result
        plt.plot(tps, y[: len(tps)])
        plt.xlabel("t, [s]")
        plt.ylabel("y, [units]")
        plt.grid(True, alpha=0.3)
        plt.show()
    else:
        print(f"Warning: output file {out_file} not found. Check the SimInTech project settings.")

Explanation of key lines

• run_simintech(...) uses subprocess.run without shell=True and with arguments as a list -- this is more reliable and safer.
• The /run and /exitonstop flags start the simulation and close the GUI after successful completion.
• Input/output via *.dat: use numpy.savetxt/numpy.loadtxt for a simple text format. For multiple channels, organize columns.
• The modules generate_time_period, convert_tp_to_sec_tp, and unit_step are part of TensorAeroSpace and simplify the creation of test signals.

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Alternative: running from PowerShell

"C:\\SimInTech64\\bin\\mmain.exe" \
  "C:\\tensoraerospace\\aerospacemodel\\simintechModel\\lsu2.xprt" \
  /run /exitonstop

Quotes are required if the path contains spaces.

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Common issues and solutions

• SimInTech does not start from Python:
• Check the correctness of the path to mmain.exe.
• Make sure the .xprt project file exists and is accessible.
• Run the script from "PowerShell (x64)".
• The process exits with a nonzero code and empty output:
• Open the project manually and check the file input/output blocks.
• Compare the format of sit_in_1.dat with what the project expects (number of columns, delimiter, encoding). For binary format, use numpy.tofile/fromfile.
• Output file is not created:
• Make sure the write path is correct and the directory exists.
• Check directory access permissions.

Data format

The specific file format (*.dat) depends on the settings of your SimInTech project. If the format does not match, update the read/write logic in Python.

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Checklist

• [ ] The path to mmain.exe is correct (or accessible via an environment variable/shortcut)
• [ ] The .prt/.xprt project opens manually and runs correctly
• [ ] Input reading and output writing blocks are configured for files
• [ ] Python generates the input file in the required format
• [ ] Launching via subprocess.run completes without errors and the output file is readable