GreenGuardian — Autonomous Weed-Spotting Rover

Broadcast herbicide is cheap to deploy and ecologically brutal: over 90% of what a boom sprays lands on soil and healthy crop instead of on the weed, poisoning groundwater and accelerating herbicide resistance. The affordable anti-answer — mechanical weeding rigs — runs into the hundreds of thousands of dollars.

Three drive iterations ended on two independent high-torque rear motors with skid steering (zero-radius turns) driven by a Pico over 2 Mb/s serial. The sensing stack is deliberately two-stage. Stage one: a custom TFLite classifier trained on weed classes (dandelion, crabgrass, blowballs, clover, plantain) runs at 0.25 confidence on a wide 2304×700 strip. Stage two — the part that makes spray land on the weed — an HSV threshold finds the yellow flower's bounding box and normalizes it to image coordinates, so the actuator knows (x,y) precisely, not just "a weed". A magnetometer (HMC5883L) keeps heading so the rover turns 180° at row ends and drives the next row. The Pico firmware pulses the 12 V solenoid for ~0.15 s only when the spray point is centered under the weed.