Great question!
I made an executive decision when I started to design this robot in a CAD program to give it 3 Degrees Of Freedom (DOF) to reduce cost and decrease error when the robot returns the ball. Error mostly comes from the moving parts. We have 5 moving parts (4 servos and 1 air cylinder).
We talk about our 3DOF here in the Reaction System Video:
Please tell me if you know of a cheap way of getting or creating fast and accurate xyz-axis translation system that can cover the whole table. The thing that makes translation hard is F=ma (Force = mass x acceleration). You need to have a system that can accelerate, decelerate, and stop at particular point in xyz. In addition, there will have to be a feedback loop to tell the response system where the paddle is in real-time for the system to calculate the new response trajectory. The icing on the cake is that the system has to do all of this within a fraction of a second. It is possible but the cost will go up. Please tell me what your thoughts are?
Keep asking questions and giving suggestions. Thanks!
-John Milton