Displacement amplification and differential actuation in piezo driven nanopositioners

[Display omitted] •Amplifies displacements of PZT stacks by a factor of 12 along horizontal axes.•Amplified output displacement is bilateral in differential actuation (DA) mode.•Output travel range is doubled w.r.t. to non-differential actuation modes.•DA improves linearity of input-voltage-output-displacement characteristics.•DA makes hysteresis curve symmetrical w.r.t. the ideal non-hysteresis line.•Total harmonic distortion of output displacement is considerably reduces by DA.•Small cross-coupling at output stage versus largely misaligned input displacements. We study a novel piezo-driven nanopositioning mechanism in the horizontal plane. For each horizontal axis, we employ two externally leverage mechanisms with flexure hinges to provide bilateral displacement of the output stage as well as amplified displacement with respect to strokes of two piezo stack actuator. The bilateral amplified motion is achieved by differential actuation of the PZT stack pair of each axis. We also designed a housing structure for the nanopositioner with holes and trenches for safe and neat wiring. It also provides proper installation on the optical table and allows incorporation of auxiliary parts to hold and and align capacitive displacement sensors for precise measurements. We designed wedge mechanisms that together with the housing and the nanopositioner structure allow proper alignment of PZT stacks during installation as well as preloading them. Experiments were carried out to identify the ranges of displacements for the output stage as well as the inputs of the leverage mechanism, using Laser-Doppler-Vibrometry and capacitive sensors. We also developed a simple rigid-link-ideal-hinge kinematic model for the leverage mechanism, which was consistent with the experimental results under no external load conditions. However, due to the external loads and elasticity, large deviations exist between the experimental results and the predicted values by the model. The discrepancy revealed a non-reciprocal property of the individual leverage mechanism and the need to employ more accurate flexure hinge models. Experiments show that the proposed nanopositioner amplifies the input stroke of the PZT stacks by a factor around 12 in the differential actuation mode. Compared to the conventional non-differential actuation modes, the differential one provides almost twice stroke for the output stage as well as more linear input–output characteristics. In addition, the proposed structure