To control sensorless type Brushless DC (BLDC) motors, various back Electromotive Force (EMF) detecting methods have been widely used. In this research, a Finite Elements Method (FEM) model of an 8 pole 12 slot BLDC motor and two kinds of phase-voltage sensing back EMF detecting electrical circuits are coupled to achieve improved and more reliable analysis results. Through this coupled analysis, it becomes possible to analyze the characteristics of the motor and how the electrical circuit affects the motor at the same time. This makes it possible to design high performance embedded motor controllers in the future. An experimental evaluation of the coupled analysis results was also implemented to verify the coupled analysis.
A lock-in amplifier was proposed for capacitive sensor applications. This amplifier was based on a general-purpose microcontroller and had only a charge amplifier as analog circuits. All the other functions of lock-in amplifier except for the charge amplifier were implemented with firmware and the internal resources of the microcontroller. A rectangular signal, generated by the microcontroller, was used in a sensor-driving signal instead of a conventional sinusoidal signal. This makes it possible that the phase comparison circuit in the lockin amplifier is made with analog-to-digital converter, a timer and an interrupt controller. Using the oversampling method and the rectangular driving signal, we can make it easy to implement the peak detection function with software and sample the peak-to-peak signal at charge amplifier output. A charge amplifier was proposed to cancel out the base capacitance existing in capacitive sensors structurally. The experimental results show that the lock-in amplifier operating in the supply voltage of 3.0 V cancels out the base capacitance and has good linearity. Received: Aug. 13, 2013, Revised: Nov. 20, 2013, Accepted: Nov. 28, 2013 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/ licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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