Wouldn’t it be nice to lie in the sun and have a robotic mower mow the lawn (and do the boring work)? Well, at least this is the aim (among other aspects as learning more about designing such systems) of this project…

A) Mechanics

• Two wheels of a seed vehicle
• Two office chair front wheels
• Two DC motors motors (12V, 40W) with gear (23:1)

B) Mowing unit

• DC motor from a 18V battery lawn trimmer

C) Controller

• Microcontroller board ATMEGA168 (myAVR, 50 EUR) for reading the sensors and controlling the motors (two rear motors).

D) Sensors

• Three Sharp IR sensors to detect near obstacles
• RGB color sensor to detect non-lawn/lawn areas (no need to build a virtual fence in your garden!)
• Bumper with three micro switches

E) All other parts

• A wooden board (38 x 53 cm) for assembly of everything
• Two gel-lead batteries (2 x 12V, 10Ah)

F) First version (without mowing unit), without sensors

Click here to see video (9 MB) which shows this mower prototype in action (indoor) 🙂
G) Second version – now with sensors and mowing unit!

The color sensor is working – the RGB color value is measured periodically and then converted into HSV (hue/saturation/value) color model. A first test with real lawn shows it can detect areas with a green color very precisely. For testing the algorithm, the first goal was to keep the robot on the blue piece of carpet – it successfully stayed on there, even after ‘mowing’ for 30 minutes!