ODrive-Simulink - A custom Simulink block with Python

This approach uses Python with the module $odrive$ as backend and the method from the self-created script is called by Matlab Simulink. This project is for the ODrive V3 and can be downloaded under the MIT License at https://github.com/ChristianSchindler/ODrive-Simulink. More details on the implementations are available in the code.

Why this Approach?

The advantage of Python for this project is that the Python model $odrive$ is designed by ODrive Robotics Inc and is also actively managed and updated. Furthermore, a thorough documentation for ODrive is provided. Another advantage is that we can directly also implement the configuration work for the projects from the last semester.

Setup

Python

You have to install the module $odrive$ with pip install odrive for this project. In the Python controller, you have to set the $GEAR_RATIO$ at the beginning of the script (Default = 1 or no gears available).

Matlab

Necessary packages: Simulink Steps to activate Python :

• make sure that Python 3.8 is installed (MATLAB doesn't support any more recent version).

• find where the Python library is located. The path should be : /usr/lib/x86_64-linux-gnu/libpython3.8.so. Import the folder in MATLAB path.

• run following command in MATLAB command shell : pyenv('Version', "/usr/bin/python3.8")

Simulink

You have to change the Scopes to the expected behaviour of your motor (Change y-access scaling).

Usage Guide

Axis States

We decided to use buttons in Simulink to set the axis stat. For this, it is only necessary to $Callback Buttons$. Inside we only have to call the Python functions.


Motor Information's

At all times you can use this information (category: output-name <unity>):

• Axis State: current_state <String>

• Position: pos <turn> (0 $\widehat{=}$ 0°; 0.25 $\widehat{=}$ 90°; 1 $\widehat{=}$ 360° $\widehat{=}$ 0° and one revolutions $\neq$ 0)

• Velocity: vel <turn/s>

• Torque: torque <torque in Nm>


Motor Control

For controlling the motor, there are several ways. In this project 3 of them are implemented (category (File): input-name <unity>):

• Position ($poscontroll.slx$): i_pos <turn> (0 $\widehat{=}$ 0°; 0.25 $\widehat{=}$ 90°; 1 $\widehat{=}$ 360° $\widehat{=}$ 0° and one revolutions $\neq$ 0)

• Torque ($torquecontroll.slx$): torque <Nm>

For each of them, there is an example module.

Additional Functions

There is an additional button 'Set new Starting Point' to set the current position as starting Point (pos $=$ 0).

Developer Guide

Add Additional Fetcher

• Add method to Python script ($controller.py$)

• restart Matlab

• test in Matlab with py.controller.FUNCTION_NAME(VARIABLE)

• For Callback Button: create a button and copy the code from $3.$

• For MATLAB Function: Create Function and include the method call and coder.extrinsic ('py.controller.FUNCTION_NAME')