~/projects/calvin
An autonomous robot built for UBC Engineering Physics' annual competition: it follows tape, reads infrared beacons, grabs "agents" with a crane and claw, and ziplines them home, all as a finite state machine on an Arduino-based TINAH board.
$ render article.mdx
Search posts, research, projects and tags, or jump to a page.
CALVIN was built by three of us for the University of British Columbia Engineering Physics robot competition. The course changes every year; ours asked the robot to follow a taped path, stop at alarmed gates and read an infrared beacon, circle a platform to collect toys we called "agents," and finally load them into a bag and send it down a zipline back to the start. All of it autonomous, with no remote control.
CALVIN runs as a finite state machine on a TINAH board, an Arduino variant with an onboard LCD and tuning knobs. Each task on the course is a state, and the robot moves through them in order:
The beacons emitted either a 1 kHz or a 10 kHz infrared sine wave, and CALVIN had to tell them apart from a distance and at an angle. Instead of chasing an absolute threshold, we built two analog band-pass filters, one tuned to each frequency, and simply compared their outputs. When the robot turned or backed away both signals dropped together, but the correct one stayed proportionally larger, so the comparison held up even as the absolute voltages changed.
The chassis, crane, arm, and claw were laser-cut from hardboard and acrylic and actuated by servos, with elastic-band mounts so a failed servo could be swapped without cutting anything apart. Two custom H-bridges (zener diodes and MOSFETs, with PWM speed control) drove the wheel motors at around 16.5 volts, well past what the microcontroller could source on its own.