Piezoelectric stack actuator

Fig. 9. Structure of the 3-way microvalve using the piezoelectric stack actuator [26]...

Fig. 17. Structure of the micropump using piezoelectric stack actuator [6]...

Chaplya, P.M., Mitrovic, M., Carman, G.P., and Straub, F.K. (2006) Durability properties of piezoelectric stack actuators under combined electromechanical loading./. Appl. Phys., 100, 124111. 

Fig. 8.19. Piezoelectric stack actuator driven mechanisms for rotor blade leading...

Fig. 6.16. Piezoelectric stack translator, a Structure, b electromechanical equivalent circuit and amplitude responses of the actuator and sensor transfer behaviour in small signal operation (derived from [5])...

Shape memory actuators offer a lot of advantages, but there are also some quite serious drawbacks. When comparing SM actuators with other actuator principles (such as piezoelectric stacks or solenoids), it should be taken into consideration that research for improved shape memory materials is relatively young. With shape memory alloys and actuators slowly gaining commercial importance it is expected that in the next few years new SM alloys will emerge that have higher transition temperatures and good effect stability [85,86]. 

The self-sensing solid-state actuator concept illustrated in Fig. 6.139b was implemented into a commercially available positioning system driven by a low-voltage piezoelectric stack transducer [332,360]. 

Fig. 1.41. Micropositioning assembly in the MIM tunneling experiment. In an aluminum block (1), two gold electrode.s (2) are contained. The right electrode is attached to a pair of membranes (3), and actuated by a stack of piezoelectric plates (4). The left electrode is actuated by a differential screw (5) for coarse positioning. The entire assembly is enclosed in a thermostat and then a vacuum chamber. (After Teague, 1978.)...

To generate large pressure, a stack structure of many piezoelectric plates and metal electrodes is used. Pressures greater than 350 kgf/cm2 are obtained. The maximum stroke is, however, small. The stroke to length of the actuator is smaller than 10 3. A high applied voltage of over 100 V and a small current are features of this actuator. 

An example of a smart material is one developed by Toyota. The multilayer piezoelectric ceramic inside an automobile shock absorber has about five layers for sensing road vibrations. The multilayer stacks positioned near each wheel of the auto also have about 100 layers that act as the actuator, all part of the same ceramic. After analyzing the vibrational signals, a voltage is fed back to the actuator stack, and a response occurs by pushing on the hydraulic system of the auto to cancel the vibration. 

Fig. 2 Schematic illustration of the principal types of membrane actuations in micropump, (a) Thin-film piezoelectric actuation, (b) stack piezoelectric actuator, (c) parallel plate electrodes for electrostatic actuation, (d) thermopneumatic actuation using thermal expansion of a secondary working fluid...

Piazza G, Pisano AP (2007) Two-port stacked piezoelectric aluminum nitride contour-mode resonant MEMS. Sens Actuators A 136 638-645... 

The engine industry is pursuing the use of bipolar electric loading to enhance the mechanical actuation of piezo or PZT stacks or actuators for fuel injection. Theoretically, a reverse electric field at a limited level can introduce beneficial depolarization and increase the number of switchable domains. Hence, a greater piezoelectric response of a stack can be promoted. This is mainly based on tests of singlelayer PZT and limited work on several commercial PZT stacks However, the fatigue performance of PZT stacks under the bipolar electric loading mode, specifically semi-bipolar mode, is essentially uncharacterized. 

A dot-matrix printer is the first widely commercialized product using ceramic actuators. Each character formed by such a printer is composed of a 24 x 24 dot matrix. A printing ribbon is subsequently impacted by a multiwire array. A sketch of the printer head appears in Figure 4.1.28a [51]. The printing element is composed of a multilayer piezoelectric device, in which 100 thin ceramic sheets 100 xm in thickness are stacked, together with a sophisticated magnihca-tion mechanism (Fig. 4.1.28b). The magnihcation unit is based on a monolithic... 

The shape configuration of the mechanical actuator is important because it determines the ampUtude and the direction of the movement. Conventional shapes (like planar, tube or roll) are not able to induce linear contraction as can be found in muscles. One of the possibilities is to use a stack-like configuration inspired by piezoelectric technology. It consists of a multilayer stmcture of a planar actuator. When high voltage is applied, the entire device contraction is the sum of each layer thickness compression (Carpi et al., 2005). 

The high voltage stack translator is the work horse of piezo actuators. Furthermore, it lends itself to explaining the construction and properties of piezoelectric actuators. 

Figure 6.28 Teflon stack microreactor with integrated piezoelectric actuator and experimental setup. (Reproduced from Ref [24e] with permission of the Royal Society of Chemistry.)...

Although the expansion of piezoelectric crystals is small, the force they can exert is large and, when stacked together, they can serve as linear actuators. Also they can provide very small movements with extreme precision which makes them ideal for positioning atomic force microscopes. 

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