Adaptive Compensation of Hysteretic and Creep Non-linearities in Solid-state Actuators

Solid-state actuators based on active materials allow high operating frequencies with nearly unlimited displacement resolution. Their hysteretic characteristics cause a non-linear and ambivalent relationship between the electrical control quantity and the mechanical output quantity during large-signal operation. This behavior can highly restrict the usability of solid-state actuators and is therefore not wanted. In the following, a novel method based on the so-called Prandtl-Ishlinskii approach is presented, which allows extensive compensation of the hysteretic and creep non-linearities during actuator operation. With continuously measured control and output quantities it is possible to compensate not only the non-linearities but also the influence of slowly changing external disturbances such as temperature, mechanical pre-stress, aging, and fatigue of the material. The fast variations due to the force response of the surrounded mechanical structure cannot be considered here. This influence has to be directly introduced into the transducer model. Finally, the capability of this adaptive compensation method is shown in an example involving a two-axis piezoelectric positioning system.