Observation of zero creep in piezoelectric actuators

Abstract.Piezoelectric actuators are frequently used nowadays in a wide variety of positioning devices. Although very suitable for small displacements in the range of nm to several hundreds of μm, the actuators always suffer from hysteresis and creep between the input voltage and resulting displacements. In scanning applications, the input voltage is often used as an indicator of the induced displacement. This procedure can result in a large position error depending on the amount of hysteresis and creep. In order to describe and control hysteretic systems various models for hysteresis have been published but little is known about relaxation and creep in piezo materials. In this paper we present detailed studies of the hysteretic behavior and piezo relaxation and creep. We have identified certain locations on the hysteresis loop that exhibit zero creep. From this observation, a more fundamental relation between the amount of creep and the local slope of the hysteresis loop and the virgin curve is presented. This observation could be useful in both open-loop and closed-loop position control, since it allows quantification of the creep. Futhermore, the experimentally observed relation between the creep and the hysteresis suggests a reduction of the creep for non-hysteretic transfers. First measurements on a system with reduced hysteresis support this hypothesis.