Model-based vibration control requires a mathematical model of target structures to design a controller. Since the control systems are adversely affected by the aging and characteristic variations of the target structures, model-free control has been studied in recent years. However, most of them may lead to complication of the control system and increase of designer's burden. Therefore, model-free vibration control using a virtual structure was developed as a simple and practical control method. This method achieves model-free control by using a 2-DOF system consisting of an actuator and a virtual structure as the target structure. The actuator is an electromagnetic proof-mass actuator modeled as a 1-DOF spring-damper-mass system. In some previous studies, a robust controller was proposed for the stiffness and viscosity uncertainties of the actuator. However, the variation of the mass is not considered in them. So, the adverse effects caused by the variation of the actuator dynamics are not completely suppressed. In this study, we propose a more general controller considering the uncertainty of the mass as well as the damping and stiffness of the actuator via frequency shaping. Specifically, the uncertainty of the system due to their variations is estimated in the frequency domain as an unstructured perturbation. The controller compensating for the uncertainties is developed by H∞ control theory based on the small gain theorem. Finally, it is shown that the proposed controller is more robust against actuator dynamic variations than the conventional model-free controller with virtual structure that does not consider actuator uncertainties.

Active Vibration Control,Model-free Control,Virtual Structure,Actuator Uncertainty,Unstructured Uncertainty