MAKE Flickr photo pool member mr_tentacle writes –
“A 2-wheeled balancing robot. Balancing robots are also refered to as “Inverted Pendulum” robots, because they work on the same principal as a pendulum. The robot is dynamically unstable, e.g. left alone it will fall down. A gyro and accelerometer located near the axis of rotation (the axles of the drive wheels) provide feedback to the MCU on the robots angle to the vertical and rate of change in the angle. The MCU can then compute the amount of motion needed to move the axis of rotation under the center of gravity, thus keeping the robot standing up.
By making the robot relatively tall putting more weight at the top of the robot the natural period of the pendulum is increased, giving the sensors and computer more time to detect the robot tipping over and apply the necessary corrections.” – Link.
Check out each photo for specific details of the construction.