[Alan Anderson]

Is sending 0.2 to the motor enough to raise it? Your Kp constant doesn't look nearly large enough to control an arm against gravity, and I don't see an I term to overcome the steady-state error you'll have.

Start by increasing Kp until it oscillates, then dial it back just enough to stop the oscillations. If that doesn't keep the arm where you want it to be, consider adding I to what's now just a P controller.