Multivariable robust optimal PID controller design for a non-minimum phase boiler system using loop transfer recovery technique

LQG/Loop Transfer Recovery (LQG/LTR) technique based on Kalman filter as observer, has some difficulties in facing with non-minimum phase systems. The main problem is that the observer becomes unstable when the compensator recovers the target loop asymptotically. In this paper, we propose an optimal robust recoverable target loops for a boiler system. Using asymptotic time-scale eigenstructure assignment ATEA algorithm a stable observer is designed that makes the target loop recovered. Then, the controller is reduced to a PID controller for experimental purposes. Recoverability of target loop under controller reduction has been analyzed. Numerical results of two controllers are given in time and frequency domain. Comparing with a similar work based on loop-shaping H^infin approach, LQG/LTR controller shows improvements in energy consumption and time responses.