Howdy All. My team is planning on trying out an idea called a "ball-drive" for this year's competition, and i wanted to utilize this forum's engineering expertise, to see if this can somehow be made into a viable drive system, or if this is just a dumb idea that will embarass us at regionals. The thing is designed to work like a mouse-ball, except instead of providing input (like a mouse does) based on the ball's movement, the ball is driven by several wheels (probably small omni-wheels), that rotate it around the X, Y, and Z axes.
The frame will be circular for this application, and will have 5 caster wheels around the edge. The ball itself will be a hollow metal ball coated in either rubber or another grippy material. It ought to look something like the picture attached. (
http://www.chiefdelphi.com/forums/at...tid=3629&stc=1 )
My opinion is that the drive is not the best idea, and here's why:
-The area of contact between the ball and the floor is very small, leading to the problems of:
---movement. If we accelerate too fast, the ball will start slipping, and our traction disappears
---rotation. turning 120 pounds of robot with such a small area of contact (directly in the center) is difficult at best and impossible at worst
---carpets. If the floor of the FIRST arena is made of carpet and the ball of rubber, you get almost no traction at all (because the carpet moves under the ball), which is compounded by the problems listed above. (can be remedied by gratuitous use of velcro)
-The robot won't be able to go up inclines. If the front end is on an incline and the back end on the floor, the ball is off the ground and not providing power.
-If the center of gravity is not directly over the area of contact with the floor, there is more thrust on one side of the COG than the other, which leads to unwanted spin.
The use of a fast, maneuverable robot was usually advantageous in past competitions, and we're shooting for that this year. The team suggested the ball because it has the potential of providing multi-directional thrust and rotation at the same time, like a holonomic drive. But the idea of a single ball is a lot simpler than everything involved in said holonomic drive.
We're talking to professional engineers on what their opinion of the ball-drive is, and considering a lot of the problems and benefits ourselves, but any advice or opinions you guys can contribute will be greatly appreciated!
Thanks!