Hi I have been thinking about stairs for my next robot (someway off yet) but I have had a few ideas.
What I am thinking of would be heavy, require some good motors and allot of gearing. My plans have the robot at about 4 foot tall.
My plan uses the tri-star wheel design. I can post a few links. but it would require some thinking. http://orionrobots.co.uk/tiki-index.php?page=Tri+Star+Wheels&PHPSESSID=25bb9a0c56fe6befb39f74f7b03536d5
the robot would have 3 wheels (each wheel being a tri-star) the 2 at the back would be driven as a differential drive, but not in the normal one motor per wheel arrangement. instead I intend to use an adder-subtracter gearing systemhttp://orionrobots.co.uk/tiki-index.php?page=Adder+Subtractor+Drive
The front wheel would also be a tri-star, but the drive to the wheels and the drive to the tri-star would be separate, and able to brake independently. The tri-star would have to be able to lock so that it runs free on one wheel of the three, while on flat ground. This is so that the wheel (in fact whole tri-star system) can spin like a caster would. Finally the two back wheels, and the front wheel would have to be connected via a Y shape (where the bottom of the Y is the front wheel and the two points at the top are the back wheels) which can pivot at the center. This would allow the front and back wheels to be brought closer together and further apart for different stairs, and to be able to raise and lower the height of the robot. The main body of the robot would then be attached to a forth and final beam attached Perpendicular to the center of the Y (coming up off the screen). This alows the robot to lean forward and back to ajust balance. This will help allot when coming down steps, as well as being able to push the front wheel out in front.
It sounds complicated, because it is, and I have put much thought in to this. You would have to calculate the size of the robot, based on wheel sizes to deal with stairs.http://www.fas.harvard.edu/~loebinfo/loebinfo/Proportions/stairsdoors.htmlhttp://www.visi.com/~dc/tristar/http://www.visi.com/~dc/tristar/bkground.htm