Displacement-maintaining piezoelectric actuator without friction

We propose a displacement-maintaining piezoelectric actuator based on a hysteresis loop and a displacement-voltage loop. Remnant polarization and remnant strain of piezoelectric material depend on maximum applied electric field. By adjusting the peak and valley of the applied voltage, the displacement-voltage loop of piezoelectric material is changed, and our proposed actuator can have different displacement states at zero voltage. In order to verify that this actuator is practical, a commercially available piezoelectric stack using modified lead zirconate-lead titanate is used as a drive unit. Experiments show that the actuator can maintain displacement without friction. Moreover, the relationships between maintainable displacement and the peak and valley of applied voltage are obtained. The actuator can continuously adjust the maintainable displacement with nanometer-level resolution and micron-level stroke. This work provides a method to maintain continuously adjusting displacement at zero voltage without friction, which can be expected to expand the range of application of piezoelectric materials in precision actuators.