I built a system that has 4 rods with a block attached at the end that rotates in a circle and stops every 1/4 revolution of a cycle. It then starts back up after a certain amount of time. What I noticed here is that everytime my motor stops and starts, I get a lot of shaking in the blocks and rods, which is impacting the performance. Should I use a different kind of motor? Stepper, AC, DC? Or is there something else I can do to dampen these vibrations? Currently using an AC induction motor.
This could have several different causes; more data is needed to identify which one is causing your problem.
the start-or-stop cycling could be kicking the weighted rods into oscillation like the tines of a tuning fork.
your motor driver board could be erroring out at slow speeds and feeding chopped power to the motor.
your drive board could be putting the motor and its position encoder into an oscillating condition when the shaft speed is zero or nearly so because you are not implementing any endpoint shutdown routine in your control algorithm.
you could be eliciting a torque oscillation where the drive shaft torsional elasticity is reacting against the rotary inertia of the weighted-arm wheel assembly.