The partial loop transfer recovery for servosystems

A design method of servosystems using the partial LTR (Loop Transfer Recovery) technique is proposed for nonminimum phase plants including finite unstable zeros and output delay. We focus our attention on the feedback property achieved at the plant output side. First, for a factorized plant model, we construct an optimal tracking system with an integral controller that feeds back only the minimum phase state vector. For the output feedback case, we construct a controller that includes a Kalman filter and an optimal prediction for the minimum phase state vector. The transfer function matrix in the right matrix-fraction of the servosystem with the MEF (Minimum-phase Estimate Feedback) integral controller and multiplicative decompositions of the sensitivity matrix at the plant output side are given. Then an application of the partial LTR technique to servosystems is discussed. The feedback property achieved at the plant output side is given with an explicit expression of the sensitivity matrix. Finally, a numerical example is presented to illustrate the feedback property.