Exact constraint design of bridge-type displacement flexure amplifier

Bridge-type amplifiers are commonly used to increase the effective actuation stroke of piezoelectric stack actuators owing to their compact size. However, the traditional bridge-type amplifier has an unconstrained degree-of-freedom, which yields large parasitic motions when subject to offset loads and induces dynamic performance losses related to underconstrained resonance. This work presents an exact constraint design (ECD) of bridge-type amplifier, in which a semi-bridge is introduced for both the lower bridge and the upper bridge on the basis of the traditional bridge-type amplifier. A holistic theoretical model is established for the whole bridge-type amplifier without reducing it to a half or even a quarter by taking advantage of structural symmetry. The model is generalized so that it can be used for modeling the traditional, the compound and the ECD amplifiers. Based on the model, three different bridge-type amplifiers considering manufacturing errors are modeled and compared, and the results show that the ECD amplifier is more precise in achieving desired motion and more robust against manufacturing imperfections. All the results are verified by those of the finite element models.