PIDDYBOT – A Self Balancing Teaching Tool

We’re sure that most Hackaday readers are already familiar with the inverted pendulum system, which basically consists of a pendulum having its center of mass above its pivot point. Most applications (like the one we are going to describe) limit the pendulum to 1 degree of freedom by affixing the pole (or circuit board here) to an axis of rotation. The overall system is therefore inherently unstable and must be actively balanced in order to remain upright.

[Sean] created the piddybot, a tiny balancing robot aimed to teach the basics of PID control by trying to get the robot to stand still. More interestingly, the Proportional / Integral / Derivative values can directly be adjusted using the three on-board potentiometers. This will allow users to get the feel of each parameter’s impact on the robot behavior. The piddybot is based around the Arduino nano, a custom PCB, 2x 26:1 geared motors, one 1A dual motor driver board, a six degrees of freedom Inertial Measurement Unit, 2 batteries and finally a 3D printed body. You can check out a video of the robot in action after the break.

This project stems from a non-PID self balancer which [Sean] hacked together in September.

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Building a Ball-Balancing Robot

robotBallBalance

If you want a different kind of feedback systems challenge, ditch the Segway-style robots and build one that can balance on a ball. UFactory is a startup in Shenzhen, and this impressive little guy is a way of showing their skills applied to the classic inverted pendulum. At nearly 18 inches tall and weighing just over six pounds, the robot boasts a number of features beyond an accelerometer and gyroscope: it has both a WiFi module and a camera, and can be controlled via a homemade remote control or a Kinect.

The build uses plastic omni-directional wheels attached to 3 brushed dc motors, which attach to the base of the robot with custom-made aluminum brackets. The UFactory gang constructed the robot’s body out of three acrylic discs, which hold the electronics directly above the wheels. The brain seems to be an STM32 microcontroller that connects up to the motors and to the sensors.

You won’t find the code on their Instructable yet, but according to the comments they have plans to make the entire project open source. If you’re desperate for more details, the UFactory team seems willing to provide source code and other information via email. Make sure you see the video after the break, particularly the end where they demonstrate interference and carrying loads. This isn’t the first ball pendulum we’ve seen; take a trip down memory lane with the BallP ball balancing robot from 2010.

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Self-stabilizing autonomous bicycle

For [Gunnar]‘s diploma thesis, he wanted to build an autonomous bicycle. There’s an obvious problem with this idea, though: how, exactly does a robotic bicycle stand upright? His solution to balancing the bicycle was a reaction wheel that keeps the bicycle upright at all times.

A bicycle is basically an inverted pendulum; something we’ve seen controlled in a number of projects. To balance his driver-less bike, [Gunnar] used a stabilizing wheel and an IMU to make sure the bicycle is always in the upright position. The bike measure the tilt and angular velocity of itself, along with the speed of the stabilizing wheel. To correct a tilt to the left, the stabilizing wheel spins clockwise, and corrects a rightward tilt by spinning counterclockwise.

While [Gunnar]‘s solution of a bike wheel used as a gyroscope is clever – it uses common bicycle wheel, hugely reducing costs if someone wants to replicate this project – there’s not a whole lot of ground clearance. The size of the stabilizing wheel could probably be reduced by replacing the 7.4 kg steel wheel with a Tungsten, Osmium, or Lead disk, possibly becoming so small it could fit inside the frame. Still, though, a very nice build that is sure to turn a few heads.

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