There's two types of weeding, the most common is the huge quantities of seedlings that come up in new soil. That's dizzyingly easy for a human, and it's not too difficult for a robot. It's too repetitive for a human. The difficult types of weeds are those that have to be drilled, because humans don't have drills and mapping ability.

Drilling soil using an auger is actually a back and forth movement using just one vector on a single motor. The arm has at least 1 force sensor in the tool piece.