Jet, a Fast Line-Following Robot
I’ve long admired Steve Hassenplug’s line-following robots for their graceful movements.
The first time I saw one of his robots was at the ChiBots Spring 2002 contest. I was finishing up a reasonably-fast trial run when Steve (who I hadn’t met before that) asked if he could try a couple of practice laps. I smiled to myself when I saw it was “just a LEGO robot”.
But, within seconds of Steve’s LEGO Lightning taking off, my attitude changed and a small crowd formed to admire its speed. After watching for a couple of laps (which didn’t take very long), my robot and I quietly backed away.
Steve’s LEGO Lightning achieved 73.8 cm/s that day. His robot was more than twice the speed of the next fastest competitor (me at 34 cm/s).
In the ChiBots Fall 2004 contest, Steve outdid himself. The course consisted of 10 straight tiles (12 inch long line) and 12 turn tiles (9.4245 inch long line) for a total of 233.1 inches or 592.07 centimeters. Steve’s Ben Hur robot took only 21.48 seconds to complete three laps, which calculates to a linear speed of:
(592.07 cm * 3 laps) / 21.48 seconds = 82.7 cm/s.A significant feature of Steve’s designs is his steering mechanism. Some people mistakenly believe it is Ackerman steering, but it actually is differential steering with the majority of the mass (brain, batteries) being carried along like a cart.
The response is quick since the steering consists only of a compact group of motors and sensors — low mass, low torque. It’s efficient and auto-smoothing, as the robot doesn’t struggle with changing the direction of the majority of the mass while sweeping the sensors back and forth trying to center over the line.