The actuation principle

The multi-stacked actuator is designed to be directly driven by the Maxwell stress without any strain as mentioned above. Its fundamental principle of operation is shown in Fig. 7.1. When a voltage is applied between the two electrode layers, Maxwell stress is produced and thus, the dielectric elastomer is compressed along the axial direction. The compression of each layer results in the lateral expansion of the actuator because of the incompressibility of the polymer. Consequently, the deformation of the multi-stacked actuator is the summation of the deformations of individual layers and, thus, the total deformation is expressed as follows. 

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The classification of micropumps is somewhat arbitrary. One might distinguish micropumps according to the type of momentum transfer to the solution (mechanical or electrical), but for practical reasons, we choose here to distinguish them by the presence or absence of mechanical valves, this being a generic element of many pumps. A second classification can be made using the actuation principles (see Fig. 5). Various examples of the different pump-types are listed below. 

The actuation principles for the devices listed in the above is so clear that the explanation is not necessary. The metals or the alloys, which are appropriate to the listed devices, are classified into three categories ... 

The actuation principle of IPMCs is based on the electromechanically induced bending. At the same time, in nature, biological muscles utilize... 

To successfully transit cellulose EAPap actuators into these applications, it is crucial to ascertain the actuation principle responsible for the performance parameters. Based on the cellulose structure and our processing of the cellulose-based EAPap, we believe that the actuation is due to a combination of two mechanisms ion migration and piezoelectric effect associated with dipolar orientation. In the remainder of this report, we present experimental evidence of both. 

In the presence of an electric field, the sodium ions surrounded with free water molecules can move to the cathode. Selective ionic and water transport across the polymer under an electric field results in volumetric changes, which in turn lead to bending. When a DC electric field was applied, the cellulose EAPap actuator was bent to the positive electrode, which confirmed the above explanation. The ambient humidity effect on the EAPap actuator performance is further evidence, where ion transport is facilitated when humidity intake is higher. Thus, the actuation principle of cellulose EAPap might be a combination of piezoelectric and ionic migration effects associated with the dipole moment of cellulose material. 

The actuation principle of EAPap actuators was investigated in terms of ion migration and piezoelectric effects. To physically investigate the actuation mechanism, several tests were performed. TSC measurement showed a linear relationship of depolarized current with the applied electric field, indicating dipolar orientation. By comparing XRD spectra before and after electrical activation, the possibility of recrystallization in the cellulose material was observed. Dielectric property measurement indicated a dependence of the dielectric constant on fiber direction. Thus, we conclude that the combination of piezoelectric effect and ionic migration effect might be the actuation principle. 

The core components of a complete microsystem are the integrated sensing, acting or passive micromechanical devices. In most cases, a naked chip manufactured in bulk or surface micromachining is used for the detection of a physical or chemical quantity or some actuation principle, like the dosage of ink droplets in inkjet printheads. A complete microsystem can consist of a complex set of these devices. 

The ISFET-based integrated coulometric sensor-actuator system was introduced in 1985 [154] in order to facilitate in situ calibration of ISFETs. The essential components of a prototype sensor based on this operational principle are shown in Fig. 4.20.B. The system was built by integrating a large noble-metal actuator electrode and a counter-electrode in a piece of silicon. A window in the actuator electrode was etched to receive the gate of the ISFET, which functioned as a pH indicator. The flow-through cell was constructed by sealing a silicon cover with an etched cavity of the chip. The system operation resembles that of a conventional coulometric titration system very closely. The sample was first injected into the cavity and the... 

One important application of pneumatic transmission is in the operation of diaphragm actuators. These are the elements generally employed to drive the spindles of control valves (Section 7.22.3) and, if hard-wired transmission systems are employed, require devices which convert electric current into air pressure or air flowrate, i.e. electropneumatic (E/P) converters. The basic construction of a typical E/P converter is illustrated in Fig. 6.77. A coil is suspended in a magnetic field in such a way that when a current is passed through the coil it rotates. This rotation is sensed by a flapper/nozzle system (Section 7.22.1). The nozzle is supplied with air via a restrictor and its back pressure actuates a pneumatic relay. The output from the latter is applied to the feedback bellows and also acts as output from the E/P converter. Electropneumatic valve positioners employ the same principle of operation. 

Accdg to Ref 3, pp 216—19 229, the original acoustic homing system was called Kranich and the later version Pudel. The Pudel fuze was not sufficiently developed to be used in combat, but the Kranich fuze was. The Kranich consisted of a light diaphragm-actuated mechanism which responded to the sound of airplane propellers at a range of 15 meters. It was constructed on the same principle as the Pudel fuze. It was planned to install the Kranich system on some Rheintochter missiles... 

Unit-dose and bi-dose systems are designed to deliver one or two doses into the nostril(s) (Fig. 9). As compared to multidose pump systems, unit-dose and bi-dose systems are distinguished by a different actuation principle. The dose volume is predetermined by the prefilled glass vial and sealed with a rubber stopper. The glass and rubber are the identical materials used in syringes. The benefit is an optimal protection against environmental influences. Unif-dose and bidose systems can be sterilized, and an aseptic filling procedure justifies the omission of preservatives. 

The clickhaler is based on the same principle a reservoir containing a number of doses releases one after an actuation. 

To handle the complexity of the plant and to still achieve the overall goal, a control hierarchy has been developed and used for many years. This architecture gets the company policy (several weeks time resolution) and refines it to the current action to be applied on any actuator of the plant (ms-sec resolution time). The procedure is to observe the state of the plant through thousands of sensors and evaluate the next action for any resolution time. Implicit, explicit, heuristic and first principles models are used in order to generate the adequate action. The common process control architecture has four control levels. The lower level of the architecture is the basic regulatory control, this control is achieved by single decentralized loops. Most of these loops are controlled by standard PID controllers. The actuating horizon at this level is just one. 

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