Feasibility of Active Material Vibration Suppression in a Large Stroke Flexure Hinge

Flexure mechanisms are widely used in precision applications. The finite support stiffness results in parasitic resonance frequencies, typically with low damping, that can be detrimental for positioning performance. Moreover, these resonances may vary over the workspace for mechanisms with moderate or large deflection. In this paper we consider a model of a large stroke flexure hinge that requires accurate end-effector positioning. The feasibility of damping the parasitic resonances using active material is investigated. It is shown that, by placing piezoelectric patches at suitable locations on the flexures, the problematic parasitic resonances can be sensed and actuated. Using modal decoupling the vibration modes are separated, whereafter positive position feedback control is used to suppress the vibration modes. By changing the controller resonance frequency as a function of the nominal deformation, vibration suppression over the entire workspace is achieved. The improved damping in the mechanism is shown using transient simulations.