Direct multivariable MRAC design without gain symmetry conditions

This note presents a novel multi-input-multi-output (MIMO) direct MRAC design for plants of arbitrary (vector) relative degree without imposing symmetry conditions related to the high frequency gain (HFG) matrix. In contrast to the previously proposed solutions based on the HFG matrix factorization, the control law is similar to the conventional MIMO-MRAC adaptation law and does not involve additional parametrization. Both the continuous-time and discrete-time are considered in the new proposed approach.