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 periodic output feedback control technique when there is a failure of a system component to function (say, a sensor or a actuator). The entire structure is modeled in state space form using FEM by dividing the master structure into 8 finite elements and placing the sensor / actuator pair at finite element positions 2, 4, 6 and 8. Robust decentralized POF controllers are designed for the various models of the plant by retaining the first two vibratory modes. The effect of the failure of one of the piezo patch is observed. In this proposed control law, the control inputs to each actuator of the multimodel flexible system is a function of the output of that corresponding sensor, only and the gain matrix has got all off-diagonal terms zero. The designed robust controller provides satisfactory stabilization of the multimodel smart structure system.