The goal is to design and build a robot lawn mower and see just how good one can make it. We can send a robot to Mars and it works autonomously for years. Electric cars can travel fast with no driver and avoid objects, but the current range of robot mowers are, in comparison, simply quite crude. This is quite understandable as they need to be simple to avoid complex setting up and maintenance which would render then uneconomic.
With that in mind I will attempt to design and build a robot mower using the range of tools and inexpensive hardware available.
The Start
I had a defunct strimmer from which I salvaged the motor. I thought to attach some blades which had predrilled holes in them.
I drilled one of the holes to make it larger for a 4mm bolt. This was difficult but managed it in the end. I attached the blade to the salvaged strimmer motor and mounted in a wooden frame on wheels and gave it a go using a 12 volt supply. The results were not good.
The rotor was very unbalanced and shook itself free from the carefully designed clamp I made. The blade had no free movement as the hole was too tight a fit for the bolt. Then I found this on Amazon
That just looked like what I needed so I got one and built it into a prototype frame.
Next – Driving the wheels
Managed to get a stepper motor working using a pi. I had the code saved here – https://wiki.twig.tk/index.php/The_code_to_control_a_stepper_motor
It did need a bit of wire swapping (from the pi to the LM293N driver board) to get them in the right order.
The next task is to duplicate this setup for both wheels and combine the code
Update – Major problem, the stepper motors do not have enough power to drive the wheels. This is a major problem and requires a significant redesign. To this end larger stepper motors with a 5:1 gearbox were purchased