Active vibration control is an important problem in structures. One of the ways to tackle this problem is to make the structure smart, adaptive and self-controlling. The main objective of active vibration control is to reduce the vibration of a system by automatic modification of the system's structural response. This work features the modeling and design of a robust decentralized controller for a smart flexible system using a periodic output feedback control technique when there is a failure of a system component to function (say, an actuator). The entire structure is modeled in state space form using the finite element method and Euler-Bernoulli theory principles by dividing the master structure into eight finite elements and placing the piezoelectric sensor/actuators as collocated pairs at finite element positions 2, 4, 6 and 8, thus giving rise to a multi-input multi-output plant. Robust decentralized periodic output feedback controllers are designed for the various models of the plant, retaining the first two vibratory modes and considering one actuator failure at a time. The effect of failure of one of the piezopatches on the system is observed. In this control law, the control input to each actuator of the multimodel flexible system is a function of the output of that corresponding sensor only and the gain matrix has all off-diagonal terms zero. The designed robust decentralized periodic output feedback controller provides satisfactory stabilization of the multimodel smart structure system. © 2005 IOP Publishing Ltd.