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 and all of the CAD files and go build your own!.