I once considered building one, but never got started because my agriculture took a turn away from field cultures towards trees / bushes (cherry and sea-buckthorn). Now, sadly, I’m involved with far more destructive robotics projects than weed-whacking. :( If the RF stops trying to conquer places and drones aren’t needed to oppose that insanity, maybe I’ll get back to peaceful projects.

Some notes:

• imaging: I strongly recommend Raspberry Pi and libcamera, can provide directions and sample code (C++) if anyone needs

• navigation: I considered a tall mast (fishing rod / plastic pipe / other) made rigid with shroud lines and a downlooking camera, information plates with QR or Data Matrix codes embedded in ground (find the information plate by contrast, pass to decoding algo, get reference point coordinates out)

• weed detection: hardest part, I never got there

• weed destruction: sensible options seemed like 1000 W of LED light focused by a Fresnel lens, and pressure spraying with water (at the cost of throwing up mud at the camera)

• motors: I considered extremely slow geared stepper motors with bicycle sprockets and chains, ordinary 4 amp industrial stepper drivers

• wheels: I considered bicycle rear wheels without a freewheeling mechanism*

• steering: I considered bicycle front forks, stepper motors and toothed belt (oversized 3D printer parts)

(* actually, a freewheeling mechanism might be handy to retrieve a broken robot, but then you also need brakes)

Basically, it would have been 2 bikes in parallel, rear wheels driven by steppers, front wheels steered by steppers. No brakes. Tall mast, navigation camera at mast top, instrument camera on a movable arm.