Comparing controllers for a flexible link

Many electromechanical systems with resonant modes are difficult to control with just output feedback. A conventional solution is to use proportional control with velocity feedback. In theory, full state feedback should yield better control. However full state feedback may not be economically justifiable or even technically feasible. This paper compares solutions using proportional plus velocity feedback with a combined observer-state feedback controller. A recently introduced approach using a disturbance observer is then shown to be a special case of observer design and in this context also allows a form of proportional plus integral plus derivative control. The controllers are evaluated on an experimental rig which restricts the resonant motion to one rotational dimension.