Partial decoupling of non-minimum phase processes with bounds on the remaining coupling

Partial (triangular) decoupling of MIMO systems has been considered in the literature as a way of relaxing the design limitations introduced by diagonal decoupling in non-minimum phase processes. The former strategy allows decoupling a variable of interest without affecting it with non-minimum phase dynamics. However, when right-half plane (RHP) zeros are mainly aligned with this variable, pushing the effect of the RHP zeros to other outputs comes at the cost of great interactions in those variables. This article presents a method to delimit these interactions without degrading significantly the decoupled variable response. To this end, the algorithm shapes the reference signal by means of an auxiliary sliding mode loop.