Electronically Stabilized Monopod

Description

When you're on a hiking trip with some friends and you want to snap a group photo, you need a drone, a tripod, or a selfie stick. Selfie sticks make you look pretty dumb, so that's out of the question. Drones are pretty expensive and complicated for a simple group photo. And tripods are too bulky to carry on a hiking trip. So why not use a monopod that has some magic at the top that prevents it from falling over. That is the goal of this project.

The technical term for this is a "reaction wheel inverted pendulum". Basically, the motors at the top of the monopod spin up and spin down, creating a torque on the monopod. That torque is used to bring the monopod back to its most stable position, thereby preventing it from falling.

Details

The microcontroller uses the current angle to apply power to the motor using a PD control algorithm (like PID, but without the integral).

Here is a video of a 1-axis prototype. It is 34" tall.

Components

1 × Teensy 3.5 This is the microcontroller that runs the control algorithm.

1 × Invensense MPU6050 Breakout This is the angle sensor for the system.

1 × TI LaunchPad F28069M This is the motor controller logic board. It runs the InstaSPIN motor control system.

2 × TI DRV8305 Boosterpack These are the power boards for the motor controller.

2 × Turnigy Brushless Motor This is a random Turnigy motor from Hobbyking. It has a nominal rating of 200W and 900kV.

Project Logs

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Code and files available
Kyle Bartholomew • 06/16/2017 at 22:52 • 0 comments

I just uploaded all the files related to this project to a Github repository. The Arduino code is simple and well commented, but the InstaSPIN code is pretty messy. So use that with caution. I'm going to put together a quick guide for setting up the InstaSPIN controller, with the adjustments necessary for this project. The documentation that comes with the InstaSPIN system is voluminous and very hard to follow.
The 3D models are also available. They're quite simple and they aren't really suitable for 3D printing, but they are there for reference. I uploaded them in the default Autodesk Inventor format, as well as in the IGES format.

https://github.com/beak90/ReactionWheelPendulum
Single Axis Prototype
Kyle Bartholomew • 06/12/2017 at 00:30 • 0 comments

For the last 6 months or so, I've been working on this project as my Senior Project for my BS in Mechanical Engineering at Cal Poly Pomona. I've created a working prototype that is constrained to 1 axis. It has 608 bearings at the base that run very smoothly to simulate a pin joint. Only having 1 axis made it much easier for me to tune the controller, and it made it cheaper while I experimented with different motor and controller options. I've finally found a setup that works, so I will be creating the full 2-axis system in the next few weeks. I anticipate that it will work similarly to my 1-axis system, but of course only time will tell if that is the case.
In the mean time, check out these videos of my working prototype!
This is a ~17" tall version that I started with:
And here is a taller version that works just about as well. It is 34" tall:
The 34" tall version is approaching the height needed for a useful monopod. My goal is 4 feet tall, but I will probably start with 3 feet for the next prototype, because I am currently maxing out the motor controllers I'm using. It would be pretty easy to increase their peak power by about 50%, which would probably make a 4 foot tall version possible, so I will probably do that right afterwards.

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Electronically Stabilized Monopod

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Single Axis Prototype

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