Twitch is a small RC vehicle. I built is as a study in an unusual drive train, and also as a very expensive toy. The vehicle is quite close to a clone of Shane Colton’s project Twitch Jr., which itself was inspired by a FIRST Robotics team’s bot Twitch. So I guess that makes mine the third generation.
So, beyond being a box with four wheels that moves, what is Twitch? Two critical features make this thing fun to drive: 1) Omniwheels, allowing the wheels to slide sideways without skidding, 2) A motor and wheel configuration that allows the wheel direction to swing from front-to-back to side-to-side. The black boxes in the animation below are high-torque servos that drive the pivoting of the wheel and motor assemblies
Showing the motion of the linkages
The result is a control system that I’ll call ‘holonom-ish.’ It doesn’t exactly have a degree of control for every degree of freedom (x,y and theta), but it doesn’t have the same problems with manoeuvres like parallel parking that a conventional 4wd vehicle does. As a result it’s very manoeuvrable and extremely fun to drive.
Video from my in-progress robot shows how silly and fun to drive it is.This is my first just-for-fun robot, and it was built without access to a machine shop. Accordingly, I kept the design as simple as I could and borrowed ideas wherever possible. I’ll go over the robot’s fabrication, and construction in the following pages.
The robot in its current form
Curious parties can download the [bill of materials](./Final BOM.pdf) and all of the CAD files and go build your own!.