Automated Weed Spraying Drone Needs No Human Intervention

Battling weeds can be expensive, labor intensive and use large amounts of chemicals. To help make this easier [NathanBuilds] has developed  V2 of his open-source drone weed spraying system, complete with automated battery swaps, herbicide refills, and an AI vision system for weed identification.

The drone has a 3D printed frame, doubling as a chemical reservoir. V1 used a off-the-shelf frame, with separate tank. Surprisingly, it doesn’t look like [Nathan] had issues with leaks between the layer lines. For autonomous missions, it uses ArduPilot running on a PixHawk, coupled with RTK GPS for cm-level accuracy and a LiDAR altimeter. [Nathan] demonstrated the system in a field where he is trying to eradicate invasive blackberry bushes while minimizing the effect on the native prairie grass. He uses a custom image classification model running on a Raspberry Pi Zero, which only switches on the sprayers when it sees blackberry bushes in the frame. The Raspberry Pi Global Shutter camera is used to get blur-free images.

At just 305×305 mm (1×1 ft), the drone has limited herbicide capacity, and we expect the flights to be fairly short. For the automated pit stops, the drone lands on a 6×8 ft pad, where a motorized capture system pulls the drone into the reload bay. Here a linear actuator pushes a new battery into the side of the drone while pushing the spend battery one out the other side. The battery unit is a normal LiPo battery in 3D-printed frame. The terminal are connected to copper wire and tape contacts on the outside the battery unit, which connect to matching contacts in the drone and charging receptacles. This means the battery can easily short if it touches a metal surface, but a minor redesign could solve this quickly. There are revolving receptacles on either side of the reload bay, which immediately start charging the battery when ejected from the drone.

Developing a fully integrated system like this is no small task, and it shows a lot of potential. It might look a little rough around the edges, but [Nathan] has released all the design files and detailed video tutorials for all the subsystems, so it’s ready for refinement.

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A New Open-Source Farming Robot Takes Shape

The world of automated farming may be an unglamorous one to those not invested in its attractions, but like the robots themselves that quietly get on in the background with tending crops, those who follow that path spend many seasons refining their designs. The Acorn is a newly-open-sourced robot from Twisted Fields, a Californian research farm, and it provides a fascinating look at the progress of a farming robot design from germination onwards.

The Acorn is not a CNC gantry for small intensive gardens in the manner of designs such as the Farmbot, instead it’s an autonomous solar-powered rover intended for larger farms which will cruise the fields continuously tending to the plants in its patch. It’s a work in progress, so what we see is the completed rover with the tools and machine vision to follow. It pursues the course of a low-cost lightweight platform, an aluminium chassis surmounted by the solar panel, with mountain bike front fork derived wheels at each corner. It has four wheel drive and four wheel steering, meaning that it can traverse the roughest of farmland. We can see its progress since a 2019 prototype, and while it seems as slow as the seasons themselves to mature, we can see that the final version could be a significantly useful machine on a small farm.

It’s not the first autonomous farming robot we’ve seen over the years, as for example this slightly more robust Australian model. We’re guessing that this is the direction autonomous farming is likely to take, with the more traditional tractor-based machinery projected by some manufacturers taking on repetitive loading and hauling roles.

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