 Speaker | 65 - Static Thrust Analysis of a Voice Coil Motor | Module:TR | 2013-01-28 | Linear actuators are used in machine tools because of their high-speed performance, high acceleration and deceleration, and accurate positioning. There are coreless types of linear actuators, as well. They generally have a smaller thrust force than core linear actuators, but they do not produce cogging, so they only have a small amount of thrust variation. Because of this property, they are used in fields where high-accuracy positioning is necessary, like with head drives of packaging machines or the slight movements of precision stages.
Static thrust variations at the translation position of the actuator have an effect on determining the position accurately. The static thrust is determined by the amount of current, so its current characteristics need to be obtained.
This Application Note explains how to obtain the current characteristics and the translation position characteristics of the static thrust in a voice coil motor, which is a type of coreless linear actuator.
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 | 9 - Sound Pressure Analysis of a Loudspeaker UP! | Module:DS,TR | 2013-04-26 | A loudspeaker produces sound when the voice coil makes the vibrator vibrate. The general requirement of the loudspeaker is to produce uniform sound over a wide range of the frequencies.
Lorentz force is generated in the coil when the magnetic field of a permanent magnet acts on the current flowing through the voice coil, and produces sound by making the vibrator vibrate. In order to evaluate the sound with good accuracy, it is necessary to handle the resonance phenomenon between the Lorentz force and the speaker's eigenmode properly. The eigenmode and Lorentz force distribution change depending on the place where the core and coil are wound, so high accuracy calculations need to be carried out using the finite element method (FEM).
This Application Note presents how the frequency characteristics of sound pressure can be obtained using the constant Lorenz force on the voice coil, regardless of the frequency.
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