To make a two degree of freedom arm capable of speeds needed to play air hockey, how should the arm be controlled? I'm wondering about speed vs accuracy.
The following image is from a project involving a 2DOF drawing arm:
For this air hockey project, the general mechanics of that arm seem appropriate. it can move the "hand" around a 2D plane. I also like how both motors are at the base of the arm, instead of having the 2nd motor at the elbow (which adds weight to the arm and slows it).
However, the drawing robot is slow.
I understand that in general, steppers are 'slow'.
But, steppers have accurate positioning, which is very important in a game of air hockey. I also know that the steppers can be geared-up, but then they lose torque. The steppers would need to handle the inertia of quick, back-and-forth arm movement.
I've used small servos for other projects, but the accuracy was poor. Most don't have a way to read the angle externally, and those that do, have noisy signals. I'm not sure how strong the hobby servos are, and if they can be accurate enough for this project. I understand that using digital servos improve dead band issues.
DC motors with external feedback:
The only other method I can think of for controlling the arm would be to use DC motors with sensors like as rotary encoders. I think I would need an absolute rotary encoder. But they seem to be around \$50-$1000, which is a bit much for a solution I'm not sure will even work out. Perhaps there are cheaper solutions to motor angle measurement. I could just use a potentiometer, but then I'm worried about noise again.
It's worth noting that I don't know of any easy or affordable way to design my own drivetrain. All I have is a drill, and I don't know how I would mount shafts/bearings and such, even if the gears themselves were affordable.
This means that if I need to gear-up or down, I don't think I can unless it's cheap and involves simple tools.
So for the arm: DC motors with external feedback, servos, steppers, something else?...
Which method would be the best in terms of speed, and which for accuracy? I'm wondering which would cost less as well, but I understand that is a grey area.
I'm leaning towards servos out of simplicity. I'm may try digital servos with ball-bearings, in the hope they that will move quick enough, but be strong enough to handle the inertia of the arm.
(Note that a 2DOF arm is desired, and not something else like a 3D-printer x-y belt system.)