I’m sure you’ve heard that it rains a lot here and that we don’t get a lot of sun. So when those brief dry spells happen on a weekend, you pretty much have to mow your lawn right then, lest you find yourself overrun by undergrowth. However, mowing the lawn takes ages and is really boring. So we will be building this open-source lawn mower robot immediately.
Maker Clemens Elflein devised OpenMower after being let down by the current generation of robotic lawnmowers. The only models he could find simply drive themselves in a straight line until they hit a perimeter wire buried in the ground, at which point they turn around a bit and then set off in another straight line. OpenMower is able to localise itself using very precise real-time kinematic (RTK) positioning, meaning it can mow a patch of grass much more efficiently.
Learning the map
OpenMower is so smart it can roam freely between different mapped areas. So if you have a front and a back garden, it can mow one, drive itself round to the other, and start mowing again.
To teach the robot where you want it cut the grass, you first have to drive it around the area using a remote control. Clemens’ dad taught his OpenMower using a standard Xbox controller. He mapped it to mow tightly up against the edges of the patio and to cut a neat circle around the base of a tree.
The robotic gardener starts off cutting the perimeter of your mapped area, then efficiently mows neat lines until it has cut the entire area.
How does it work?
Clemens picked up this off-the-shelf robotic lawn mower for €400. It meant that the main mowing motors and batteries were already in place in a neat waterproof package.
Clemens added Raspberry Pi 4 as the main processor of the OpenMower software. It handles all the big jobs like navigation and localisation. All the real-time tasks are a job for a Raspberry Pi Pico, which hides underneath the RTK GPS board.
Want to build your own smart lawn mower?
What day do you get your garden jobs done? We polled Pi Towers and we’re all Sunday afternooners.