Design of a large deflection compliant mechanism with active material for vibration suppression

The control bandwidth of a flexure mechanism is typically limited by parasitic resonance frequencies with low structural damping. Such resonances can be suppressed by including active material in the mechanism, which is used to dissipate energy at specified frequencies. The active material is typically placed in areas with high strain, in order to obtain the highest possible coupling and therefore dissipation. However, due to the low ultimate strain of some common active materials, the included active material will limit the deflection of the mechanism. In this work we introduce a design method that improves the closed-loop performance of a low pivot shift cross hinge mechanism by including active material in the leaf springs, without sacrificing the achievable deflection of the mechanism. The coupling between the active material and a selected undesired parasitic frequency is maximised by placing the material in locations with high modal strain. At the same time, the piezoelectric patches are only included in regions where the strain due to the nominal deflection is limited, such that the maximum deflection of ± 15 degrees is maintained. Using the patches as sensors and actuators, positive position feedback control is applied. Using simulations, it is shown that a selected resonance peak can be decreased by 16.3 dB for the considered mechanism, enabling 88% higher bandwidth.