Voice coil motors

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... 

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%. 

Whilst all DMAs utilise a voice coil type motor, some are fitted with a force transducer to measure the force transmitted through the sample. This requires a different design of instrument. It is frequently and incorrectly thought that the omission of a force transducer leads to poor modulus accuracy. Provided that the voice coil motor is correctly calibrated and its own contribution to the total stiffness measurement is removed, it does not make any difference, since the force measured by the transducer and the one taken from the motor calibration are both accurate to within better than 1%, which is adequate. Far larger errors occur... 

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... 

As a linear motor, a voice coil may be used. It is a noncontact linear motor consisting of an electromagnetic coil and a pot-shape magnet. The term voice coil originates from its wide use in loud speakers. 

Older TMAs are not fitted with motors, but rely upon a top-loading scalepan for the application of force. In TMA the force is constant for all classic experiments, therefore the manual arrangement is quite satisfactory for this work. In DMAs and more modern TMAs a voice coil type motor is employed. This comprises a light coil and former, connected via fine wires, often made from Litz wire. This assembly is either supported by springs or the drive arrangement is supported by an air bearing. Conceptually it is similar to the design of a loudspeaker. 

The top-loading scalepan TMAs require no calibration. Instruments fitted with the voice coil type motors will require calibration. Most instruments achieve this by applying one or more known masses (which can be accurately measured on a balance cahbrated by traceable standards) and nulling the displacement that occurs. This way the force required to rebalance the applied mass is obtained independently from the displacement measurement. The instrument measuring system will adjust the voltage or current applied to the coil, and when the displacement has been successfully nulled this value is equivalent to the force due to the applied mass. The value of force to current should be linear over the range of operation of the instrument. 

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