Ball based self-balancing machines. Again, these started to appear around 2007. A selection of examples, with dates are given below. There are many others.
May 10, 2007
I love this one, the “Leango”. This is the earliest human rideable ball based scooter I can find.
2010
University project robot on ball balancing glasses of water
2010
Honda U3-X not quite a ball, more a driven omniwheel
2012
Robot PhD thesis
2016
Robot on a ball – balances very well.
2016
University project robot on a ball.
2017
University project with a human rider.
Another video of this one.
Nick Thatcher’s TALON machine from 2018 when it won a UK design prize:
Link: https://innovate-design.co.uk/news/new-designers-show-2018-winners-wow-innovate/#
2021
A very tall office robot.
2023
University project with a human rider.
2024
Lego Mindstorms robot on a ball.
What if you want to make your own?
Some good places to start, with links:
https://github.com/algarv/Ball_Balancing_Robot
https://www.instructables.com/How-to-make-a-Ball-Balancing-Robot/
https://techknowtone.co.uk/Projects/P/BallBot/ballbot.html