March 16th, 2022—
Omni wheels are fantastic because they let a vehicle drive forward, backward, left, right, and rotate — all without a steering mechanism. There are only two catches: all four omni wheels must be driven and omni wheels don’t handle rough terrain or obstacles well. Tank tracks are perfect for rough terrain, so James Bruton thought to combine the two concepts. To test this idea, he built an Arduino-controlled robot with a triangle of tank tracks.
This robot has three tank tracks, each of which is driven by a simple geared DC motor. Burton arranged those in a triangle formation, so each track is at a 60 degree angle to the other two tracks. Normally, an arrangement like this would be a disaster, as it couldn’t drive in any direction without dragging at least one of the tracks. But Bruton lined all of the tracks with small wheels, which have axes of rotation perpendicular to the track motor axles. Those wheels rotate freely, so the vehicle can move without resistance — even when that movement is perpendicular to one of the tracks.
Movement requires the coordination of all three track motors in order to vector the motor speed. Bruton used an Arduino Mega 2560 board for the job, because it has plenty of pins available to control the motor drivers via PWM. It also had pins to spare for an SPI connection to an nRF24L01 radio transceiver, which receives commands from Bruton’s general purpose robot remote control.
The robot drove quite well on smooth carpet and is able to maneuver in a manner similar to what you’d see with standard omni wheels. Unfortunately, it wasn’t able to handle obstacles. The tracks were too smooth to get traction on an obstacle and constructing them from a grippy material would have kept them from sliding when necessary. While the robot didn’t accomplish Bruton’s goal, it is still interesting to see in action and is a thoughtful exploration of alternative drive types.