# Simulink models

`simulink.write_model` writes the MATLAB scripts that build a Simulink model of the system. The model has the same structure as the PLECS model, built from basic Simulink blocks (no toolboxes needed):

```{image} ../images/simulink_drive.png
---
target: ../_images/simulink_drive.png
alt: Simulink model of a 5.6-kW PM-SyRM drive
class: only-light
---
```

```{image} ../images/simulink_drive_black.png
---
target: ../_images/simulink_drive_black.png
alt: Simulink model of a 5.6-kW PM-SyRM drive
class: only-dark
---
```

*Simulink model written by `examples/pmsyrm_6kw_gn_fvc_simulink.py`. The output ports `mdl` and `ctrl` give the signals for simulating from Python.*

## Building the model

```python
simulink.write_model("ipmsm.slx", mdl, ctrl, t_stop=1.2)
```

This writes, in the folder of the model:

- `build_ipmsm.m`, which builds the model and saves `ipmsm.slx`;
- `init_ipmsm.m`, which defines the parameters, as in the [PLECS models](plecs.md#parameters);
- the C sources of the blocks of the control system (`sfun_*.c`).

Run the build script in MATLAB. It compiles the blocks of the control system into S-functions, so it needs a C compiler. The model runs the initialization script after loading and at the start of each simulation, so a change in the script takes effect in the next simulation.

## MATLAB Function blocks

Without a C compiler, write the model with MATLAB Function blocks:

```python
simulink.write_model("ipmsm.slx", mdl, ctrl, t_stop=1.2, code="matlab")
```

The blocks then run a MATLAB port of the same control code, and the model contains their code. The results are the same as with the S-functions, to the rounding errors.

## Simulating from Python

With the MATLAB Engine API for Python, `simulink.simulate` builds the model and simulates it:

```python
import numpy as np

t_eval = np.linspace(0, 1.2, 1201)
mdl_signals, ctrl_signals = simulink.simulate("ipmsm.slx", t_eval, mdl, ctrl)
```

## Good to know

- The build script refers to the files of the installed package by a path relative to the folder of the model. If you move the files or update the package, write the model again.
- A compiled S-function stays loaded in MATLAB after its model is closed. Run `clear mex` before rebuilding a model that was open.
- The Simulink models support fewer configurations than the PLECS models, e.g., no dead time or DC-bus dynamics, see [](supported.md).
- The system model does not block the gates, so the gate enable (`ctrl.set_enable`) must be 1. The exported control system still has the input `enable` and runs in standby while it is zero, e.g., when the control code is reused on hardware.