Identification of continuous-time systems in closed-loop operation subject to simple reference changes

This paper proposes a novel identification method for identification of continuous-time linear time-invariant systems working in closed-loop operation. The main idea is to introduce Laguerre functions into the refined instrumental variable method for continuous-time systems. The identification is based on normal operational data associated with step, ramp, staircase or other types of simple reference changes. The proposed method could handle nonzero initial conditions and is applicable directly to raw data. Its effectiveness is demonstrated through simulation and experimental examples.