Keep It Between the Navigational Beacons

Ah, the sweet anticipation of summer! We eagerly await its arrival, dreaming of long sunny days, the distant songs of the ice cream truck echoing through the neighborhood, and the delightful feeling of warm sand between our toes. Yet, as we welcome the sun's embrace, there is also something that looms over us like a dark rain cloud: the start of the dreaded lawn mowing season.

Mowing the lawn may be considered an unpleasant chore by many, especially when performed in the scorching summer heat. However, this task pales in comparison to the demanding work of clearing weeds in agriculture. While homeowners may grumble about maintaining their lawns, farmers face the arduous challenge of eradicating invasive weeds that threaten their crops and livelihoods. Unlike the relatively small lawns we maintain, agricultural fields can stretch for acres, making the weed-clearing process a labor-intensive and backbreaking endeavor.

A software engineer named Yuta Suito that lives in the mountains of Japan is very familiar with the problem of clearing weeds. The mountainous region he lives in is dotted with rice terraces that must be frequently weeded under the scorching summer sun. To further complicate matters, there has been a mass exodus of younger individuals in rural areas of Japan to major cities, like Tokyo. That leaves this physically exhausting work to an older population of farmers that is less capable of carrying out the work as the years go by.

Without help, these terraced rice fields are likely to disappear from Japan in the near future. Suito does not want to see that happen, so he designed and built a low-cost robot that can autonomously clear weeds. This may not be the first robotic mower, but existing solutions generally do not meet the needs of the aging farmers of Japan. For them, laying guide wires to limit the range of the mower might be too much to ask. And even using a smartphone to control the device could be out of the question.

A simple, push-button solution is needed, and that is what Suito created with his robotic mower called Roktrack that cost about $330 in parts to build. The mower can plow through tough terrain with a pair of tank treads and eccentric front wheels that can help it to climb over obstacles in its path, obliterating weeds and grass in its way with a pair of spinning blades. And for operation, all a user needs to do is set up a few pylons to mark the area to be weeded, then flip the power switch on.

Roktrack captures images with a forward-facing camera and processes them with a YOLOv8 object detection algorithm running on a Raspberry Pi 3 A+ single-board computer. It detects bright red pylons, and determines how far away from them it is by calculating their height (they will appear taller as the robot draws nearer to them). When it gets to the proper distance, it will then turn and move toward the next pylon, and the process continues as it traces out a rectangular pattern. On each pass, that rectangle gets smaller and smaller until the entire area marked by the pylons has been weeded.

The robot is powered by a LiFePO4 battery and is equipped with solar panels to keep it running every day with minimal effort by the user. It was well-engineered to make it durable and ready to use in real-world settings. Roktrack is rain-proof and has protection against condensation forming on the internal components. It also has some useful safety features — the object detection algorithm can also detect people, and when they are spotted, the mower will shut itself off.

Roktrack can clear large areas, but it is not especially fast. This is not necessarily a problem, because one can start the system up and walk away while it works. But to accommodate clearing larger fields, Suito is presently experimenting with a multi-node setup, in which mowers work together, using their sensing equipment to avoid colliding with one another.

While Roktrack was built with simplicity of use in mind, there are also some more advanced features for the power user. A companion smartphone app, for example, can remotely control the mower and show its progress. The app also has the ability to show what areas need attention through the use of satellite imagery.

Suito is exploring a number of opportunities to commercialize his technology, so in the future, we may see these autonomous mowers clearing fields and lawns around the world.