As I mentioned one of my projects this summer is to convert an electric lawnmower to a robot. Not only does this project appeal to me because of my laziness and not wanting to mow my own lawn but it allows for the creation of a platform which I can use for future developments. I started to dig into this project a bit over the past week and now have 2 different directions which I am considering.
1) A simple mechanical drive where I power the rear wheels and have casters on the front. This use of differential steering will be sufficient for my needs, but it doesn’t have that flare which makes a project stand out. On the other hand doing something simple (KISS FTW) may take the time required to finish the project more achievable.
2) My next thought is a mechanically more sophisticated system of using mecanum wheels on the robot. Mecanum wheels are ones that allow for holonomic movement(movement in any direction) You can read more about them here http://en.wikipedia.org/wiki/Mecanum_wheel One of issues with mecanum wheels is that they need to ensure contact with the ground at all time to work, which is why they are traditionally used in systems which roll on flat floors such as forktrucks. In the uneven ground of a yard or offroad the robot would require a suspension system, which is where the complexity begins. Normally suspensions are straight forward because their only requirement is to keep traction and keeping close to the ground is not a factor like it is when mowing the lawn. In the research I have done so far I have yet to find any off-road mecanum robots, in fact the closest I found is a concept for a mars surface vehicle. If I do go this route I plan on using the mecanum wheels from Andymark, as they offer 6inch, 8inch, and 10inch options with different modular hubs, which will make the challenge the implementation of the system not re-inventing the wheel.
This is the first paint style sketch of what I am thinking about if I decide to go down the mecanum path. Obviously the largest challenge is to keep the blade at a constant height so that I still have a good cut quality in addition to a autonomous robot cutting it.