Simulink to Python

Integrate Simulink models into Python via dynamic libraries using Embedded Coder and ctypes.

Quick start

1. In Simulink, enable Embedded Coder and set the System target file to ert_shrlib.tlc.
2. Build the model (Ctrl+B) -- source files and MODEL_NAME.mk will appear.
3. Build the library:

make -f MODEL_NAME.mk

1. In Python, load the library and call initialize -> step -> terminate.

Tip: keep the libraries next to the model (e.g., simulinkModel/<model_name>) to avoid depending on the current working directory.

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Cross-platform library loading

WindowsLinuxmacOS

import ctypes
from pathlib import Path

path = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/b747/b747_model_win64.dll")
lib = ctypes.WinDLL(str(path))

import ctypes
from pathlib import Path

path = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/b747/b747_model_glnxa64.so")
lib = ctypes.CDLL(str(path))

import ctypes
from pathlib import Path

path = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/b747/b747_model_maci64.dylib")
lib = ctypes.CDLL(str(path))

Or use a universal function:

import sys
import ctypes
from pathlib import Path


def load_simulink_lib(folder: str | Path, basename: str) -> ctypes.CDLL:
    """Load a *.dll/*.so/*.dylib taking the platform and typical MATLAB suffixes into account.

    folder   -- directory containing the library
    basename -- base name (e.g., 'b747_model', 'f16_model')
    """
    folder = Path(folder)
    is_win = sys.platform.startswith("win")
    is_mac = sys.platform == "darwin"

    ext = "dll" if is_win else ("dylib" if is_mac else "so")

    # Typical name variants generated by Embedded Coder
    candidates = [
        f"{basename}.{ext}",           # model.dll / model.so / model.dylib
        f"{basename}_win64.dll",
        f"{basename}_glnxa64.so",
        f"{basename}_maci64.dylib",
    ]

    for name in candidates:
        path = folder / name
        if path.exists():
            return ctypes.WinDLL(str(path)) if is_win else ctypes.CDLL(str(path))

    raise FileNotFoundError(
        f"Library not found for {basename} in {folder} (tried: {', '.join(candidates)})"
    )

Data types

The types real32_T, ExtY_T, ExtY_T_r are located in tensoraerospace/aerospacemodel/utils/rtwtypes.py and correspond to the structures/types generated by the model.

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C/C++ code generation (Embedded Coder)

To integrate Simulink models into Python you need the Simulink add-on -- Embedded Coder.

1. Open the model settings in Simulink and select Code Generation -> System target file: ert_shrlib.tlc.

1. Build the model with the keyboard shortcut Ctrl+B (or the Build model menu). A folder with the generated code and a make file with the .mk extension will appear in the model directory.
2. Build the dynamic library with the command:

make -f MODEL_NAME.mk

This will produce a dynamic library: .dll on Windows, .so on Linux, .dylib on macOS.

Windows

The build may require MSVC tools (Developer Command Prompt) or MinGW/MSYS. Make sure the compiler and make/nmake are available in PATH.

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Creating a controlled plant in Simulink

To create a controlled plant in Simulink, add the following blocks:

• Simulink/Continuous/State-Space
• Simulink/Sources/Digital Clock
• Simulink/Commonly Used Blocks/In1
• Simulink/Commonly Used Blocks/Out1

Then:

1. Rename the In1/Out1 blocks to meaningful names.
2. In the State-Space block, set the parameters (you can use a MATLAB Script for convenience).

1. Example MATLAB script for running the model:

flag = 1;

% Initialize parameters
[A, B, C, D] = b747_model(flag);

init = [0, -0.0, -0.0, 0];
ref_signal = -0.10;

% Simulation start/end time and step
t_s = 0;
t_e = 500;
dt  = 0.1;

% Run the Simulink model
simOut = sim('aircraft_sim.slx');

y = simOut.get('yout');

u     = y.getElement(1).Values.Data;
w     = y.getElement(2).Values.Data;
q     = y.getElement(3).Values.Data;
theta = y.getElement(4).Values.Data;
t     = y.getElement(5).Values.Data;

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Integration with Python (ctypes)

Integration is done through a dynamic library compiled from the model. The library typically contains three functions:

• MODEL_NAME_initialize -- model initialization
• MODEL_NAME_step -- compute the next step (step size equals dt specified in the MATLAB script)
• MODEL_NAME_terminate -- release resources

For type matching, use ctypes and type converters from tensoraerospace: tensoraerospace/aerospacemodel/utils/rtwtypes.py.

Example: Boeing 747

import matplotlib.pyplot as plt
from pathlib import Path
from tensoraerospace.aerospacemodel.utils.rtwtypes import real32_T, ExtY_T

# Load the library
b747_folder = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/b747")
b747 = load_simulink_lib(b747_folder, "b747_model")

# Entry points
b747_initialize = b747.b747_model_initialize
b747_step       = b747.b747_model_step
b747_terminate  = b747.b747_model_terminate

# Parameters/inputs (example: unit input as real32_T)
ref_signal = real32_T.in_dll(b747, "b747_model_U")  # depends on the input structure of the specific model

# Output structure
b747_Y = ExtY_T.in_dll(b747, "b747_model_Y")

# Simulation loop
b747_initialize()

time, u, w, q, theta = [], [], [], [], []
for _ in range(int(2100)):
    b747_step()
    time.append(float(b747_Y.time))
    u.append(float(b747_Y.u))
    w.append(float(b747_Y.w))
    q.append(float(b747_Y.q))
    theta.append(float(b747_Y.theta))

b747_terminate()

# Visualization
plt.plot(time, u)
plt.xlabel('t, [s]')
plt.ylabel('u, [m/s]')
plt.show()

Plot examples:

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Example: F-16

import matplotlib.pyplot as plt
from pathlib import Path
from tensoraerospace.aerospacemodel.utils.rtwtypes import real32_T, ExtY_T

f16_folder = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/f16")
f16 = load_simulink_lib(f16_folder, "f16_model")

f16_initialize = f16.f16_model_initialize
f16_step       = f16.f16_model_step
f16_terminate  = f16.f16_model_terminate

ref_signal = real32_T.in_dll(f16, "f16_model_U")
f16_Y = ExtY_T.in_dll(f16, "f16_model_Y")

f16_initialize()

time, u, w, q, theta = [], [], [], [], []
for _ in range(int(2100)):
    f16_step()
    time.append(float(f16_Y.time))
    u.append(float(f16_Y.u))
    w.append(float(f16_Y.w))
    q.append(float(f16_Y.q))
    theta.append(float(f16_Y.theta))

f16_terminate()

plt.plot(time, u)
plt.xlabel('t, [s]')
plt.ylabel('u, [m/s]')
plt.show()

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Example: ELV (launch vehicle)

import matplotlib.pyplot as plt
from pathlib import Path
from tensoraerospace.aerospacemodel.utils.rtwtypes import real32_T, ExtY_T_r

elv_folder = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/elv")
elv = load_simulink_lib(elv_folder, "elv_model")

elv_initialize = elv.elv_model_initialize
elv_step       = elv.elv_model_step
elv_terminate  = elv.elv_model_terminate

ref_signal = real32_T.in_dll(elv, "elv_model_U")
elv_Y = ExtY_T_r.in_dll(elv, "elv_model_Y")

elv_initialize()

time, w, q, theta = [], [], [], []
for _ in range(int(20)):
    elv_step()
    time.append(float(elv_Y.time))
    w.append(float(elv_Y.w))
    q.append(float(elv_Y.q))
    theta.append(float(elv_Y.theta))

elv_terminate()

plt.plot(time, w)
plt.xlabel('t, [s]')
plt.ylabel('w, [rad/s]')
plt.show()

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Example: Typical Rocket

import matplotlib.pyplot as plt
from pathlib import Path
from tensoraerospace.aerospacemodel.utils.rtwtypes import real32_T, ExtY_T

rocket_folder = Path("../tensoraerospace/aerospacemodel/model/simulinkModel/rocket")
rocket = load_simulink_lib(rocket_folder, "rocket_model")

rocket_initialize = rocket.rocket_model_initialize
rocket_step       = rocket.rocket_model_step
rocket_terminate  = rocket.rocket_model_terminate

ref_signal = real32_T.in_dll(rocket, "rocket_model_U")
rocket_Y = ExtY_T.in_dll(rocket, "rocket_model_Y")

rocket_initialize()

time, u, w, q, theta = [], [], [], [], []
for _ in range(int(2100)):
    rocket_step()
    time.append(float(rocket_Y.time))
    u.append(float(rocket_Y.u))
    w.append(float(rocket_Y.w))
    q.append(float(rocket_Y.q))
    theta.append(float(rocket_Y.theta))

rocket_terminate()

plt.plot(time, u)
plt.xlabel('t, [s]')
plt.ylabel('u, [m/s]')
plt.show()

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Common issues and solutions

• "Library not found ...": check the file name, platform suffix (_win64.dll, _glnxa64.so, _maci64.dylib), and path.
• "undefined symbol / entry point not found": use the correct function names (<model>_initialize/step/terminate).
• Windows: run the build from Developer Command Prompt for VS or install MinGW/MSYS. Check PATH (cl, nmake or gcc, make).
• Linux/macOS: make sure LD_LIBRARY_PATH/DYLD_LIBRARY_PATH includes the library directory, or use an absolute path when loading.

# Linux
export LD_LIBRARY_PATH=$(pwd):$LD_LIBRARY_PATH
# macOS
export DYLD_LIBRARY_PATH=$(pwd):$DYLD_LIBRARY_PATH

Type compatibility

The fields of the *_Y and *_U structures must match those generated by your model. If the names or composition differ, update the Python references.

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Checklist for your models

• [ ] ert_shrlib.tlc is enabled and the .mk file is built
• [ ] The library has been successfully compiled (.dll/.so/.dylib)
• [ ] The function names <model>_initialize/step/terminate are known
• [ ] The types and names of the global variables *_U, *_Y are identified
• [ ] The Python script loads the library and runs the step loop

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Useful information

• The types real32_T, ExtY_T, ExtY_T_r are defined in tensoraerospace/aerospacemodel/utils/rtwtypes.py.
• The names of the global input/output variables in the library (*_U, *_Y) depend on the generated code and may differ between models.
• See also: "Your Simulink models in Python" -- your_sim.md in this section.