By Xiang-Yang Lu
Maker Clemens Elflein got the idea for his design from the place he lives, as it rains a lot, making it hard to mow the grass, while sunny days are too precious to be spent on mowing. Because of these, Elflein devised a smart lawn mower that can drive itself and get the job done.
Interior design of OpenMower
Elflein started with YardForce Classic 500, a regular lawn mower for €400 and modified it by embedding a Raspberry Pi 4 and a Raspberry Pi Pico. The RPi 4 is responsible for positioning and navigation, while the Pi Pico controls real-time positioning of the mower. Next, Elflein built a remote control using a standard Xbox controller.
After that, Elflein taught his father to control the lawn mower through the controller. As the mower went around the whole yard, the mower can now drive and mow the mapped areas through memory and learning.
In fact, there have been automatic robotic lawnmowers long before Elflein’s design, but they were all running around randomly. For this reason, Elflein decided to develop an automatic mower that is smart and efficient. Since Elflein shares the software and hardware of his modification, the design ended up becoming a new open project called OpenMower. Yet, the cost of modification was a bit high, with the minimum cost of a basic lawn mower around €400, while the cheapest one still costs €350. Hence, Elflein recommends that any enthusiast consult him on Discord before starting, and he will be glad to share his experience and advice, so that the risk of failure can be lowered.
The modifications basically include replacing the motherboard in the original mower with a self-made circuit board, which is a carrier board, to be more specific. The board was used to connect RPi 4, Pi Pico, electronic module boards that control the mower speed, and those for positioning.
For speed, three sets of electronic speed controller (ESC) designed for brushless DC (BLDC) motors were used, while an ArduSimple GPS RTK board was used for positioning.
Since the original circuit board was not used, certain functions needed to be rebuilt on the new board, such as monitor of battery charging state and low power saving mode. In terms of software, path planning is functional, while obstacle avoidance still needs improvement, and a screen there also needs to be display for work progress.
Conclusion
iRobot once launched Looj, a robot for cleaning fallen leaves on eaves and gutters. There was also Verro for cleaning swimming pools. These are all designs targeting at addressing labor-intensive household chores and saving manpower and trouble in foreign families. Some designs are modifications made based on existing automation equipment, so that they can be more autonomous to handle tasks.
