One of the longer term projects I'm working on is an autonomous robotic system, it will be using the Raspberry Pi as the main 'brains' of the system along with a homebrew motor controller board to deal directly with the electro-mechanical components.
I had originally planned to print up the majority of the parts for the base platform (one of the main reasons I bought the printer in the first place) but that is turning out to be far more complex than I had originally planned. Things that I thought would be fairly simple (choosing suitable motors, servos and gearing systems) turned out to be more complex especially with my lack of experience in this area. Those choices then flow through to the physical design of the platform which leads to a morass of inter-dependencies to wade through and very little actual progress being made.
I was discussing this last week with a work colleague (who has had a lot more experience with these type of projects than I have) and he suggested starting with a pre-made base that is known to work and just concentrating on the electronic and software components of the project to get something that basically works. This will help build my experience, let me escape from design decision hell (by imposing external constraints) and, most importantly, let the project move forward.
To that end I went looking for something to start with and came across this kit which seems to be a good match to what I want to do in a very simple format. The size is right, large enough to fit the Raspberry Pi and a small support board (although fitting the battery packs on may make it look a little awkward), movement is achieved by two bidirectional motors (the tracks simply drag across the floor while turning) and the motor gearing, drive wheels and tracks are all included.
I went and bought on of them on Friday so I could do some simple testing. The main base is made of simple plastic components that I can modify (or completely replace if needed) and it works well on almost any flat surface, including carpet and navigating over rugs so indoor operation shouldn't be a problem. All the motors and battery components already have pin sockets on them so there is minimal work required to be able to interface it into my custom controller board instead of the provided one.