EFFECTS OF PIEZCERAMIC ACTUATOR IN QUASISTATIC USE

Abstract

In the field of smart structures, piezoceramic actuators are wildly used for vibration reduction and acoustic manipulation of structures. Those applications typically run at frequencies between 10 Hz and 10k Hz. Prominent examples are the piezoceramic actuators implemented in helicopter rotor blades to twist them dynamically for higher harmonic control (HHC) or individual blade control (IBC). Once the actuators are implemented it would be a great benefit to also use them to statically change the blade twist (higher twist for take-off and landing - for higher lift; lower twist for high speed forward flight - for reduced drag). Staying with this example it can be found that sensing the twist displacement is not an easy task at all (see [1, 2]), so it would be most desirable, to use open loop control. In order to do that, the transfer function has to be known accurately. Unfortunately measurements show that the amplitudes for such very low frequencies behavior behave strongly non linear. This paper presents experimental results investigating the influence of the frequency on the amplitude - especially going for frequencies in the lower mHz region. A variety of piezoceramic actuators has been investigated: from stacks to patch type, d33 as well as d31 effect actuators. A second focus of this paper is the reaction of piezoceramic actuators on the application of a constant DC voltage. The drift that occurs has to be taken into consideration. A third focus of this paper is the dependency of a displacement output of such an actuator at a constant applied DC voltage on the voltages that the actuator had seen before. This topic is of special mportance for aerodynamically effective surfaces that are driven by piezoceramic actuators and should be analyzed (generation of polars) in static conditions.