Differential type actuator

FIGURE 4.1.28 Structure of a printer head (a), and a differential-type piezoelectric printer-head element (b). A sophisticated monolithic hinge lever mechanism amplihes the actuator displacement by 30 times. 

If we consider an element of linear type actuator and an integrated artificial muscle actuator as shown in Fig. 7, physical model using partial differential equations is too complicated for numerical simulation of mechanical systems with such actuator. 

There are many different types of valve fitted with actuators to form control valves. Valves may be single- or double-ported (Fig. 7.123). With single-ported valves the valve plug is subjected to the total differential force across the valve. Such valves are sensitive to pressure fluctuations and powerful actuator elements are required for large pressure drops. Double-ported valves balance out the pressure differential but it is difficult to obtain complete shut-off. 

Electrothermal or Thermal Actuation Motion is generated by differential thermal expansion in materials such as sDicon or metals, while heat is typically injected into the actuator by means of Joule heat dissipation. Some actuator components expand more than others due to different cross-sections and therefore electrical resistance. Typical microactuator configurations include in-plane bimorph elements (Fig. 2a), out-of-plane bimorph plates, in-plane Chevron, or bent-beam elements (Fig. 2b) [3]. These types of actuators exhibit larger force capabiUties (in mN range), can achieve displacements of 100 pm or less but generally consume a lot of power (hundreds of mW), and have low bandwidth (Hz to KHz). Common methods of fabrication for electrothermal microactuators include surface micromachining... 

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