Last year's efforts resulted in a tractor mounted weeding machine which worked reasonably well except for the fact that it was not accurate enough and sometimes ended up destroying the leeks as well as the weeds. The video below shows the results:
Since then I have been exploring CNC, GPS and GPRS technology and feel 97.2% confident that I can create a roving weeding machine that can also perform other tasks such as cultivating (digging) and mowing with the right attachments. Think 'Moon buggy' or the 'Mars Rover' and that will be what I'm aiming for. Actually, there is already an open source project for the CNC part - the Farm Bot.
The machine will carry it's own electric generator running on gas/diesel and be propelled forwards/backwards/sideways with stepper motors/servos. Coloured markers, detected by an object recognition system, will be placed in the soil to create grids for the Weedinator to work within as GPS is not accurate to the scale of 1 mm which will be necessary to avoid killing the crops. GPS will be used to navigate to particular fields or seed beds.
As time goes on a more intelligent object recognition system will be incorporated to detect individual weeds:
The flame thrower will be mounted on a normal CNC frame with 3 axis of movement and the nozzle itself will be shrouded by metal sheet to prevent damage to the crops themselves. Individual weeds could be zapped by a small gas powered butane torch as used by a chef when making crème brulee.
This may seem like a very ambitious project, but the actual chances of achieving success are quite high. Much of it depends on the quality of the code written for reading the GPS data and transforming that into real-time steering and motion. It all just seems like great fun to me!
Programming new coordinates into the Weedinator via the cell phone network is not going to be difficult as much of the task of handling GPRS data has already been covered in my weather station project.
There is a risk that as the project evolves we will run out of programming space or computing power on the MCU ...... So ....... Just add another one and get them talking to each other via the I2C bus, which I also had up and running on the weather station project, although my code for this communication does now seem a little bit 'clunky'.
The greatest 'risk' is due to the cost involved in buying all the components - the GPS system is expensive and it currently requires 12 stepper motors just for the steering, suspension and wheel drives. Each stepper motor needs it's own controller which, although homemade, are still a bit pricey. When I say risk, I'm really referring to 'How useful is this thing actually going to be when it's finished?' Yes, there's a very good chance that we can build it and it will work, but how well will it work? For example, it might be incredibly slow.
Current overall chances of success = 85%.