Model reduction for active vibration control

In active vibration control, the modeling of the mechanical structure is generally done using the finite element method. The model obtained must be reduced to compute the controller. Model reduction must achieve two objectives: the reduced model must keep its initial dynamic behavior in the frequency range of interest; and the influence of neglected dynamics must be minimized to limit the risk of spillover. In this paper, we propose an original criterion for the selection of the controlled dynamics. This criterion has the great advantage to be independent of the placement of actuators and sensors. First, the structure is successively reduced to only one mode. For each one, it is obvious to find the optimal location of one actuator and one sensor. Thus, we obtain as many SISO systems of second order as the number of modes. Then, the Hinfinity norms of these systems are computed and the modes are sorted regarding to their influence in the global response of the system. To show the efficiency of the method, it is applied to an experimental structure: an LQR controller is designed and several tests are performed. A comparison is also done with other classical techniques of reduction.