Actuator design

As in most technical fields, actuators are increasingly designed with the help of computers. The actuator and its surrounding are simulated as a mathematical model by means of commercially available software. Such models are fundamental for the simulation of the system response characteristic in each specific case. In this way, it is possible to find out about all the important properties of the system even before the actuator is built, and the actuators relevant parameters can be optimized to achieve the desired values. This designing strategy is exemplified below with an auxiliary mass damper which is able to withdraw kinetic energy from a host vibrating system. 

Such vibration absorbers are used for instance in the automotive and aerospace industries where the vibration inclination of the car bodies or fuselages has to be attenuated. Within the scope of a first rough model the mechanical structure at the place of maximal vibration is described by the effective base mass m which is excited by an unknown disturbing force Fi causing undesirable vibrations (see Fig. 6.9). F is thus a consequence of the interaction between m and the remainder of the mechanical structure which is excited by externally or internally acting forces at other points. The task of the vibration absorber is to displace the auxiliary mass m2 in such a way as to generate a secondary force F2 = m2 a2 that will compensate the primary force Fi and thus counteract the excitation of mass mi. 

When the force F is narrow band, attenuation can be achieved with a passive vibration absorber which has to be tuned to the disturbance fre- 

The principle structure of the active vibration absorber corresponds approximately to the structure of the passive vibration absorber shown in Fig. 6.9 whereby the passive elastic material between mi and m2 has been replaced by a piezoelectric actuator and a displacement amplification system to increase the achievable displacement of m2. The amplification system is given in this example by elastic joints, similar to those illustrated in Fig. 6.9. 

The active compensation of the disturbing force Pi can now be achieved by a suitable feedback of the measured base acceleration ai to the input of the high-voltage source for the piezo actuator. Based on a signal flow diagram, which is always to be developed by the designer, for the functionality of the force compensation will be investigated on the computer with support of an appropriate dynamic simulation and analysis software system, for example MATLAB [4]. 

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The energy within a hydraulic system is of no value until it is converted into work. Typically, this is accomplished by using an actuating device of some type. This actuating device may be a cylinder, which converts the hydraulic energy into linear mechanical force a hydraulic motor, that converts energy into rotational force or a variety of other actuators designed to provide specific work functions. 

Stoeckel, D. Shape-Memory Alloys Prompt New Actuator Designs, Adv. Mat. Proc., 33 (October 1990). 

Pengilly, R. W., Keiner, J. A. The influence of some formulation variables and valve actuator designs on the particle size distributions of aerosol sprays. J Soc Cosmet Chem 28 641-650 (1977). 

Berry, J., Heimbecher, S., Hart, J. L., and Sequeira, J. (2003), Influence of the metering chamber volume and actuator design on the aerodynamic particle size of a metered dose inhaler, Drug. Dev. Ind. Pharm., 29, 865-876. 

Smyth, H., Brace, G, Barbour, T., Gallion, J., Grove, J., and Hickey, A. J. (2006), Spray pattern analysis for metered dose inhalers Effect of actuator design, Pharm. Res., 23, 1591-1596. 

A mouthpiece/actuator designed to both manually actuate the dose-metering valve and deliver the actuated dose into the patient s mouth. 

Because DEs are fabricated from conformable elastomers, they can be shaped into many actuator configurations over a wide range of dimensions. Most actuator designs use the area expansion of the DE film for actuation however, multilayer stacked actuators exist wherein actuation is through a reduction in thickness. Typical designs incorporate support structures to maintain prestrain in the films. 

Other artificial muscle applications have been demonstrated as well. Carpi et al. used helical contractile linear actuators and buckling actuators to actuate eyeballs for use in an android face [258, 268, 269]. Another eyeball actuator has been developed by Liu et al. based on their inflated actuator design their actuator is capable of generating eyeball rotations from —50 to 50 [241]. Kombluh et al. have also reported on a mouth driven by a DE actuator [4]. Biddis and Chau have provided a good review on the challenges and opportunities of DE actuators for upper limb prosthetics [270]. 

For actuators designed to act like an artificial muscle, EAPs were synthesized with at least one embedded electrode. If the material is particularly electroactive, the material would move so quickly that the embedded wire would disengage, causing the actuator to lose its electric impulse (Figs. 4.18 and 4.19). 

F. Vidal, J.F. Popp, C. Plesse, C. Chevrot, and D. Teyssie, Feasibility of conducting semi-interpenetrating networks based on a poly(ethylene oxide) network and poly(3,4-ethylene-dioxythiophene) in actuator design, J. Appl. Polym. Set, 90 (13), 3569-3577 (2003). 

Remote actuated valves must be chosen to match process requirements. Design decisions include materials of construction, valve seat material, valve t q)e, actuator type and controls characteristics. The design must match utility supply levels (air pressure, hydraulic pressure, flow capacity) and tolerances with actuator design to provide the correct torque/thrust to the valve. The torque/thrust must be above breakaway requirements and must be below stress limits of the drive train. With some valves, the ratio of these values may limit the available operating safety factor. 

The primary grouping of actuators by power source and range of motion permit some convenience in defining the actuator. The conversion of power to motion presents a large range of actuator designs. The different designs have distinctly different functional characteristics to consider... 

The design in this case-study prototype device remains an issue for the reversible motion of the liquid. This case-study prototype device could be effectively used for the one shot of liquid in both single-output and multi-output modes on demand. For continuous random switch function, another problem appears if we turn on microchannel X first and desire to next turn on only microchannel Y where X>T. In this continuous switch function, the microchaimel X -f 1) will be also turned on in this case-study prototype device. Anyway, above issues could be resolved via the two-way bubble actuator design [18, 19], which could make the fluid flow backward in the unwanted microchannel. In addition, this microfluidic switch has the potential to be integrated into a wider fluidic network system with stop valves or microflow discretizers which could be used for separation of liquid segments from a continuous source. 

TABLE 8.12 Summary of Stress Generated from Various Actuator Designs... 

FIGURE 11.21 Schematic showing the bilayer actuator design, wherein one layer in the device contracts or expands... 

Choi, H., Jung, K., Ryew, S., Nam, J., Jeon, J., Koo, J. and Tanie, K. (2005a). Biomimetic soft actuator Design, modelling, control and applications, lEEE/ASME Transaction on Mechatronics 10, pp. 581-593. 

This book presents the recent developments in EAP material processing, actuator design, control-oriented modeling, and device and robotic apphca-... 

In contrast to DPIs the basic design of MDI hardware is well described in the literature [23, 24]. Most MDIs apparently have a simpler design than DPIs and a key advantage of MDI systems is their low cost per dose. They are portable, convenient and have widespread acceptance by patients and clinicians. Basically they all have the same operational principle and furthermore all MDIs deliver a constant fine particle dose (independent of the flow rate). Whereas they have a relatively low resistance to airflow and this all makes the inhalation instruction less dependent oti the individual type of MDI. The most relevant differences between types are in the actuator design and medicine formulation (solution or suspension), in which the type of propellant and the presence of co-solvents play an important role because of their influence on the (plume) velocity with which the aerosol is released from the actuator and rate of droplet evaporation. 

Pratt, J. Flatau, A.B. Developement and analysis of a self-sensing magnetostrictive actuator design. Proc. SPIE Smart Structures and Mater. 1917, Albuquerque (1993) pp. 952-961... 

Sheybani R, Meng E (2011) High efficiency wireless electrochemical actuators design, fabrication and characterization by electrochemical impedance spectroscopy. Paper presented at the MEMS 2011, Cancun, 23-27 January 2011... 

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