Linear actuator

Explosive Actuator, Linear. A self-contained power transmitting device designed to convert chemical energy into controlled mechanical force in the form of linear mechanical movement. It is comprised essentially of a piston, propellant chge, electrical bridge wire and contacts enclosed in a housing (Ref 38b, pp 3-4, Actuator, Explosive, Linear)... 

A custom pressure cuff support was used to simulate cardiovascular activity in the brachial artery (Figs. 4 and 5). A stationary support (Fig.4, left) contains a halfcylinder made of PVC plastic that is attached across two beams. The mobile support consists of a horizontal half-cylinder mounted to the carriage of the linear actuator. Linear displacement of the mobile support creates a proportional change in the cuff s air pressure. 

Since the electric impedance and the output of a dielectric elastomer transducer are related to the deformation of the polymer film, it follows that these transducers could also be used to detect strain. For example, a linear actuator could be designed such that film capacitance is directly related to the amount of actuator linear motion. Rosenthal [10] discusses the use of dielectric elastomers as a sensor. 

SHce lip actuators Linear displacement actuators with a spacing of between 75 mm and 150 mm deflect the slice hp of the headbox nozzle. 

Pinch The industrial equivalent of controlling flow bv pinching a soda straw is the pinch valve, Mves of this tvpe use fabric-reinforced elastomer sleeves that completely isolate the process fluid from the metal parts in the valve. The valve is actuated bv applying air pressure directly to the outside of the sleeve, causing it to contract or pinch. Another method is to pinch the sleeve with a linear actuator with a specially attached foot. Pinch valves are used extensively for corrosive material service and erosive sliirrv senice. This type of valve is used in applications with pressure drops up to 10 bar (145 psi),... 

Any bi-niclal combination, having large differences in their coefficients of linear expansion, such as a bimetal of brass and steel is used for sueh applications. One end of a strip is fixed and the other is left free for natural movement. When heated, brass expands more than the steel and bends towards the steel as shown, giving the desired movement to actuate a tripping lever. 

Mechanical force can be more easily controlled using fluid power. The simple use of valves and rotary or linear actuators control speed, direction and force. The simplicity of hydraulic and pneumatic components greatly increases their reliability. In addition, components and overall system size are typically much smaller than comparable electrical transmission devices. 

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. 

One of the outstanding features of fluid power systems is that force, generated by the power supply, controlled and directed by suitable valving, and transported by lines, can be converted with ease to almost any kind of mechanical motion. Either linear or rotary motion can be obtained by using a suitable actuating device. 

An actuating cylinder is a device that converts fluid power into linear, or straight-line, force and motion. Since linear motion is back-and-forth motion along a straight line, this type of actuator is sometimes referred to as a reciprocating, or linear motor. The cylinder consists of a ram, or piston, operating within a cylindrical bore. Actuating cylinders may be installed so that the cylinder is anchored to a stationary stmcture and the ram or piston is attached to the mechanism to be operated, or the piston can be anchored and the cylinder attached to the movable mechanism. 

Mine Clearing Equipment. Devices used to actuate land mines without damage to personnel or equipment. Expl devices are typified by a group of linear shaped prefabricated structural sections, filled with composition expls, with a nose section and a towing and pushing attachment, designed for assembly into a device to be propelled by any standard tank. 

Dielectric elastomers are insulating, mbber-Uke structures, capable of undergoing reversible length change to a large extent and produce usable works. A dielectric elastomer actuator (DEA) works like an electrical motor by virtue of linear motion rather than rotation. 

Another type of linear configuration known as bow-tie is shown in Figure 10.10. The actuator is constmcted using dielectric elastomer film having the shape of a bow-tie with two compliant electrodes configured on its two surfaces. Application of the electric field results in planar actuation which because of the bow-tie shape is translated into linear motion. Typical applications of these types of actuators comprise a hexapod robot, to mimic the motion of insects like walking, to manufacture various animated devices like face, eyes, skin, etc., or the design of micro-air vehicle/omithopter. 

S. Rbimback. Linear Control of Systems with Actuator Constraints. PhD thesis. Division of Automatic Control, Lulea University of Technology, May 1993. 

As a specific example to study the characteristics of the controller, the problem involving four modes of longitudinal oscillations is considered herein. The natural radian frequency of the fundamental mode, normalized with respect to 7ra/L, is taken to be unity. The nominal linear parameters Dni and Eni in Eq. (22.12) are taken from [1], representing a typical situation encountered in several practical combustion chambers. An integrated research project comprising laser-based experimental diagnostics and comprehensive numerical simulation is currently conducted to provide direct insight into the combustion dynamics in a laboratory dump combustor [27]. Included as part of the results are the system and actuator parameters under feedback actions, which can... 

After Little s proposal, many researchers have pursued such an exciting system in vain. Even metallic behavior was rarely seen in doped organic polymers, gels, and actuators. As mentioned in Sect. 3.4.4, MCso with linearly polymerized Ceo" exhibited one-dimensional (M = Rb, Cs) or three-dimensional (M = K) metallic behavior [144]. Recently a doped poly aniline was reported to exhibit a metallic temperature dependence for a crystalline polymer chemical oxidation of monomers grew crystallite polyaniline [329] early doping studies on polypyrrole (PFg) and poly(3,4-ethylene-dioxythiophene)X (X = PFg, BF4, and CF3SO3) prepared by electrooxidation at low temperatures also showed a metallic temperature dependence below 10-20 K (Scheme 16) [330, 331]. 

Fig. 12.3. STM with a double-action lever. Various parts are shown in (a) (A) The macor block onto which the x, y piezo bars (horizontal) and the z piezo bar (vertical) are mounted, (B) the microscope base plate, (C) carriage rod, actuated by a linear feedthrough and a lead screw, (D) stop, (E) ball bushing assembly, (F) lever, (G) sample and sample holder, (H) catch, the pivot point for coarse motion, (I) foot, the pivot point for fine motion, and (J) the probe tip assembly, (b) Shows the STM in coarse motion. Using the catch as the pivot point, the sample can be removed away from the tip. (c) Shows the STM in fine motion. Using the foot as the pivot point, the linear motion of the carriage rod is reduced by a large factor. (After Demuth et al., 1986a.)...

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