Our robot has two different articulated arms moving up and down, and a majority of the weight on them is far from the live axles. We are using a PID loop to keep the arms in a stable position, but we are looking for ways to make the actual movement more smooth. Right now they jerk around.
They are both powered by encoded motors.
I wanted to ask how other teams get such smooth movement with their manipulators
*1) Counterbalance the weight of the arms with springs or gas shocks or surgical tubing.
Add more speed reduction between the motors and the arm.
Use motion control profile instead of step commands to control your motors.
My team’s robot has an arm also, it weighs roughly 35 pounds, and with majority of the weight towards the end, a mentor of ours tested it and we couldn’t belive the force required to lift the arm. We have a low bar robot so the position isn’t the best for the actuator. We put 180 pounds of force between our actuators to lift our arm! So we added torsion springs on each side to take roughly 15 pounds off. I believe this is 15 pounds from the end, so that 180 will be a lot less. You could do that too.
I = m * r^2 
the longer your arm is the more force will be required to lift it. Our arm has dual mini cims running at quite a high gear ratio (used to be 1000:1 before we decided that was too much$