Nonlinear active vibration control using piezoelectric actuators

The ever increasing resolution of metrological and production devices, with required operation ranges below one micron, results in the necessity for isolating the sensor or tool from any external perturbation. For that, it is normally unavoidable the application of active strategies, capable of eliminating the resonance peaks and obtaining good damping results without an important reduction in the stiffness of the system, as it would happen if passive strategies were adopted. Too low stiffness of the system would result in accuracy losses due to large displacements of the device under external perturbations. For the active vibration control strategies at so low displacement ranges, the piezoelectric actuators represent a good option due to both their high movement accuracy and stiffness. Nevertheless, the nonlinear behaviour of these actuators negatively affects the final efficiency of the control strategy if that characteristic is not taken into account. This work proposes a compensator of the nonlinear effects accompanying a vibration control strategy based on the sky-hook control law. The parameters for the compensator can be estimated either off-line or on-line, and in both cases, experimental results show an important improvement with respect to traditional approaches.