During the last decades, much attention has been devoted to vibration reduction problems using intelligent materials. This has raised industrial interest for the application of intelligent materials to reduce noise and vibration in civil structures, machine tools, automobiles, trains, and aerospace. In an early design stage, the real-world structures can be simulated and modeled with Finite Element (FE) analysis. The control system can also be simulated and the performance of the controller can be assessed. Deterministic approaches are unable to take into account all the variabilities that characterize control systems with integrated smart materials. In order to meet all targets on performance, safety and customer demands, a new methodology based on reliability analysis and design optimization is required. To ensure the efficiency and the high performance of a structure with integrated intelligent materials, several variables must be taken into account: i.e. thickness of the structures, boundary conditions, dimensions, material properties. In this paper a FE model of an active panel, representing a simplified model of an automotive firewall, is presented. The panel, if excited with a force, vibrates. This vibration is controlled with a second force, the controlling force. The exciting force bases on a disturbance source (i.e. a shaker), the second force represents the actions of an inertia) mass actuator. By implementing a control strategy (a PID-algorithm has been chosen), it is possible to drive the controlling force in order to reduce the vibrations of the plate In order to asses the efficiency of the control system, small changes in the thickness of the plate (due to the manufacturing process) have been taken in consideration. A reliable methodology to assess the effect of the variability is herein illustrated. This work opens the way to a more complex study of the firewall where the exciting and controlling forces are replaced with integrated piezo actuators and sensors.