ESTIMATION OF PHASE CONSTRAINED MIMO TRANSFER FUNCTIONS WITH APPLICATION TO FLEXIBLE STRUCTURES WITH MIXED COLLOCATED AND NON-COLLOCATED ACTUATORS AND SENSORS

A computational scheme is proposed to estimate a state-space representation of MIMO transfer functions from frequency response measurements. The approach can constrain the phase curve of selected elements of the transfer function matrix to certain regions. Poles of the system are determined using a frequency domain subspace approach. The phase constraint is enforced by an LMI formulation based on the positive real lemma when the zeros of the system are estimated. The successful application of the algorithm to measurements from a cantilever beam with three collocated piezoelectric actuator/sensor pairs is demonstrated.