Voice coil

A most recent commercial Nano Indenter (Nano Indenter XP (MTS, 2001)) consists of three major components [66] the indenter head, an optical/atomic force microscope, and x-y-z motorized precision table for positioning and transporting the sample between the optical microscopy and indenter (Fig. 28). The load on the indenter is generated using a voice coil in permanent magnet assembly, attached to the top of the indenter column. The displacement of the indenter is measured using a three plate capacitive displacement sensor. At the bottom of the indenter rod, a three-sided... 

Even more powerful are the neodymium—iron—boron magnets that appeared in the mid-1980s (35,36). Magnets derived from the Nd Fe B structure exhibit the highest performances obtained industrially eneigy products are >320 kJ/m3 (>40 x 106 GOe) and coercive fields around 950 kA/m3 (12 kOe). These magnets are in the course of a rapid development, eg, in voice coil motors and the automotive industry. There is a promising forecast for several industrial applications. 

The tool-electrode is mounted on a flexible structure that controls the vertical guidance of the tool. An optical sensor measures the tool displacement. An optional voice-coil motor can be added in order to control the force at which gravity-feed drilling is done. This motor can also be used to add vertical vibrations to the tool to promote the flow of the electrolyte inside the microhole. Rotation can also be included. 

Disk-drive spindle motors and voice coil motors... 

Film Applications Electrical insulation, flexible printed circuits, membrane touch switches, labels, graphics, voice coils, and general industrial applica-tions.l ]... 

Tags and labels of m-aramid paper for in-process bar coding are used where high temperature stability and chemical resistance are required. In loudspeakers, m-aramid sheets are used for voice coil insulation and for the speaker cone itself. Bus bars in lithium ion batteries for portable telephones and computers are insulated with m-aramid paper. Photocopiers and laser printers that operate at high temperatures use cleaning rollers and webs made from m-aramid paper. 

Based on the design concept, an innovative ultraprecision machine tool of perfect noncontact type can be realized, as shown in Fig. 3. The overall machine tool structure is symmetrically designed with respect to vertical nanomotion axis. All the moving structural modules, i.e., an air turbine-driven aerostatic spindle system, a planer nano-motion table system, and a vertical nano-motion system with gravity compensator, are levitated by aerostatic bearings and driven by voice coil motors in a perfect noncontact condition. In consequence, various nonlinear phenomena can be removed from the machine structure and then the error factors caused in the overall machine structure can be successfully minimized. 

Linear Nano-motion System The combination of a servo motor and a ball screw is used in the most popular table feed drive of conventional machine tool. Inversely, linear motors have been recently incorporated into ultraprecisitMi machine tool table drives. The latter characterizes noncontact drive, high speed, high acceleratiOTi, quick response, nanomotion accuracy, backlash-free, etc. Voice coil motors, a kind of linear motors, have high potentials as a fine drive system for ultraprecision machine (Shiimo et al. 2011). In order to realize a stable X-Y nano-moti(Mi table structure, the planar nano-motion system is an effective means (Shinno et al. 2007). 

Sintered magnets based on the Nd2Fei4B phase are the most important material for industrial magnetic applications. The most important applications are voice-coil motors (VCM) for hard disk drives, CD/MD pick-up systems, magnetic resonance imaging (MRI), and more recently motors for the electrical vehicle (EV) (Hirosawa and Kaneko 1998). 

Morimoto et al. (2011). Fiscal year is from April to March. VCM, voice coil motor used in hard disc drives FA, factory automation AC, etc. air-conditioner, electric refrigerators, and electric washing machines AM, automobiles except for the contribution of HEV motors HEV motors, motors used for hybrid and electric vehicles. 

Researchers at LNP Engineering Plastics [29] reported use of a thermally conductive compound to encapsulate voice coil motors (VCM) in hard disc drives. LNP Engineering Plastics Konduit compound is a 55% ceramic-filled, 10% glass-reinforced PPS-based resin with a thermal conductivity of 1 W/mK, which is about three times the conductivity of unfilled PPS. By encapsulating the VCM in the new compound, the device can handle more current, reducing seek time by 29%. 

The driving force experienced by the cone results from the interaction of the current in the voice coil conductor with the magnetic induction in the gap where the voice coil resides. This is an axially directed... 

Aside from the applied force Fa of the voice coil current, the piston experiences a restoring force Fj from the suspension whenever the piston is displaced from its equilibrium position, a frictional force Ff resulting from flexure of the spider and surround whenever the piston is in motion, a restoring force Fj, resulting from compression or rarefaction of the air trapped in the sealed cabinet behind the loudspeaker cone whenever the piston is displaced from its equilibrium position, and a force of radiation F, exerted by the air in front of the piston whenever the piston is moving so as to generate sound waves in the air. Table 1.2 collects aU of these forces and indicates their relationship to the piston velocity which is to be considered the dependent variable in the following analysis. 

In Fig. 1.20 the positive mechanical reactances are symbolized by inductors and negative mechanical reactances are symbolized by capacitors as would be true in the analogous electrical situation. The constant applied force generator is symbolized as a voltage source. Also in Fig. 1.20, Rr is identified as PocSRi 2o>a/c), whereas Kh is identified as poc S /Vq and M, as pocSXi )/o>. Unlike the common electrical situation, however, those elements that stem from radiation phenomena, such as R and M, are themselves frequency dependent. This complication will be dealt with after the model has been more fuUy developed. The circuit of Fig. 1.20, though useful, can only be an intermediate result as it does not involve any of the purely electrical properties of the loudspeaker such as the voice coil resistance or self-inductance. In addition, whenever the voice coil is in motion it has induced in it a back electromotive force (emf) of size Blu that opposes the current in the voice coil. This situation is represented schematically in Fig. 1.21. 

This allows the natural incorporation of the purely electrical aspects of the loudspeaker system, as shown in Fig. 1.26(c). In Fig. 1.26(c) the voltage generator of emfE supplies the normal actualvoice coil current. The electrical impedance as viewed from the vantage point of this generator is the series combination of the voice coil impedance, R + jcoLg, with the impedance presented by the primary of the ideal transformer. This latter impedance is the square of the turns ratio multiplied by the impedance connected to the secondary of the transformer. This product is... 

The construction of a typical ribbon microphone is shown in Fig. 3.32. Basically, the ribbon microphone produces an output signal the same way as the dynamic microphone a conductor moves in a magnetic field inducing a voltage. Instead of a voice coil, the ribbon microphone uses a thin corrugated strip of aluminum foil suspended between the poles of a permanent magnet. The ribbon, which maybe as thin as 0.001 in, acts like a 1/2-tum coil and also serves as the diaphragm. 

FIGURE 3.40 Simulated spherical loud-speaker. The housing is perforated with many small holes. The voice coils are connected 180 out of phase. Source Termaine, H.M. 1973. Audio Cyclopedia, 2nd ed., p. 111. Howard Sams.)... 

Despite their common usage, direct radiators achieve their modern success through the accumulated improvement of many decades of experience with such diverse problems as voice coil heat buildup, diaphragm nodes, enclosure types, and the compHcations of multiple radiator/crossover networks. 

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