An overview on the LQG/LTR method using the delta operator

The main design features behind the linear quadratic Gaussian method with loop transfer recovery (LQG/LTR) using the delta operator formulation are discussed. The latter allows treating the continuous as well as the discrete time cases in a unified framework, while ensuring the numerical robustness of the underlying control algorithm. It is shown that all the discrete time results smoothly converge to their continuous time counterpart as the sampling period tends to zero. The benefits, as well as the shortcomings, of the considered methodology are pointed out. In particular, the stability robustness and the poor rejection of the output disturbances are mentioned