Improving step responses by pole placement using reduced-order observers

This paper presents the results in the investigation of using reduced-order observers in satisfying step response requirements. The reduced-order observers are used to generate the unavailable states that are used in the method of pole placement for meeting the step response requirements. The step response requirements under consideration in this paper are percent overshoot, 2% settling time, and zero steady-state error. It is observed that if the initial conditions of the reduced-order observer are not close to those of the unavailable states, the use of the reduced-order observer state variables in pole placement will result in step responses not meeting the desired performance criteria. Further, there is no improvement of the performance criteria by pushing the reduced-order observer poles deep into the left half plane even though this will make the states of the reduced-order observer converge more rapidly to the unavailable states.