Multilayer actuator

For the co-extrusion of multilayer actuators, Yoon at. al. used a binder system consisting of ethylene ethyl acrylate, acrylic resin, mineral oil, polyethylene glycol and stearic acid. After sintering the resulting multilayer actuator was composed of 40 active PZN-PZT and PZN-PZT/Ag layers. The thicknesses of the PZN-PZT and the PZN-PZT/ Ag layers were 200 and 70 pm, respectively. 

Each PZT stack (Noliac, Denmark) had an overall size of 5mm x 5mm x ISnun and was composed of 8 active plates (modules) and 2 inactive endplates. Each individual active plate (5mm x 5mm x 2mm) was a multilayer actuator with an inter-digital electrode (IDE) configuration that included 30 PZT layers each 67 pm thick. The 5mm x 2mm surfaces of the active plates were coated with silver that served as an external electrode. These silver-coated plates were interconnected with a bus wire in a zigzag pattern. The rated voltage and capacitance of PZT stack were 200 V and 0.76 pF, respectively,... 

A. Heinzmann, E. Hennig, B. Kolle, D. Kopsch, S. Richter, H. Schwotzer, and E. Wehrsdorfer, Properties of PZT multilayer actuators, Actuator 2002. 

B. Andersen, E. Ringgaard, and L. S. Nielsen, Static and dynamic performance of stacked multilayer actuators based on hard and soft PZT, Actuator 2000, 7th International Conference on New Actuators, 19-21 June 2000, Bremen, Germany. 

FIGURE 4.1.21 3D positioning multilayer actuator. Notice that the x- andy-stacks are using shear mode with the spontaneous polarization perpendicular to the applied electric field direction. 

Figure 4.1.32 shows a walking piezomotor with four multilayer actuators [54]. The two shorter actuators function as clamps and the longer two provide the movement by an inchworm mechanism. 

Ueha proposed a two-vibration-mode coupled type (Fig. 4.1.38), that is, a torsional Langevin vibrator was combined with three multilayer actuators to generate larger longitudinal and transverse surface displacements of the stator, as well as to control their phase difference [62]. The phase change can change the rotation direction. 

Piezoelectric actuators are more and more often used for their accuracy and fast response. They are used in industrial applications together with a dedicated driver and a control loop. Optical applications were the first to use piezoelectric multilayer actuators. The past years have seen the development of adaptronic applications in machine tools and large scale application in automotive (gazole injectors) systems. 

Partially electroded ferroelectric devices that are heated to enhance dipole alignment under the influence of an electric field develop differential strains at the electrode edge. Strain incompatibilities at the electrode boundary can result in stresses large enough to initiate cracks from nearby flaws. Similarly, multilayer actuators, which... 

FIGURE 3.45 Multilayer actuators (a) may have many hundreds of active layers and (b) produce tens of millimeters displacement with several hundred volt drive. The response is distinctly different for piezoelecttic and electrosttictive materials. 

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