Building Reaction Wheels With Python And LEGO
Reaction wheels are useful things; typically used by satellites to keep themselves oriented the right way up in space. Turning the reaction wheel creates an equal and opposite torque in the spacecraft; allowing it to point and rotate itself accurately. The same technique also works here on Earth; and Brick Experiment Channel decided to build one out of LEGO to control an inverted pendulum.
The initial design using a small LEGO wheel on an inverted pendulum was only able to work reliably over a 4-degree angle from the vertical. Upgrading the wheel to a larger, heavier one enabled the wheel to instead work over a 28-degree range instead.
A MPU9250 inertial measurement unit was pressed into service for control of the reaction wheel; fitted to the base of the pendulum and read by a Raspberry Pi. The Pi takes accelerometer and gyroscope readings; and then controls the motor on the pendulum with a PID controller to keep the inverted pendulum upright.
The video goes into a great deal of detail on what it takes to make the pendulum run smoothly. From changes to the control coefficients to measuring the motor’s back EMF; Brick Experiment Channel demonstrates everything required to make the pendulum robust to outside perturbances.
The inverted pendulum is a great way to learn about control theory, as we’ve seen time and again.
Read more: https://hackaday.com/2022/04/27/building-reaction-wheels-with-python-and-lego/
