Hyeong-Joon Ahn

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This paper proposes a novel method to estimate the position of suspended body that hovers due to the electromagnetic force. The position information of the suspended body can be extracted from the coil currents, which contain the high frequency components due to the injected high frequency voltage without any additional hardware. The control of coil(More)
A new cylindrical capacitive sensor (CCS) design for the displacement measurement of precision active magnetic bearing (AMB) spindle is presented in this paper. This research is motivated by the problem that the existing 4-segment CCS is still sensitive to the third harmonic component of the geometric errors of a rotor. The procedure of designing a new CCS(More)
The high frequency signal injection method in the sensorless position control of active magnetic bearings (AMB), has some merits such in that there is no steady-state error in the estimated position and can control the amplitude of the signals used for position estimation. In this paper, a method to inject a high frequency signal and to process the signal(More)
In this paper, we proposed a new measuring method of the speed-dependent tool tip compliance of a high-speed machine tool spindle using an AMB (active magnetic bearing). Single sine wave current excitation is injected through the AMB, and the displacement and force responses are measured with a CCS (cylindrical capacitance sensor) and a dynamometer,(More)
In this paper, we develop a new EMV (electro mechanical valve) system using PM/EM (permanent magnet / electro magnet) hybrid EMA (electro magnetic actuator) and achieve the soft landing and the fast transition of the system using a simple PID control. Against the existing EMA using only the EM, the proposed actuator has several advantages like the PM biased(More)
In this paper, the superconducting fault current limiter (SFCL) using magnetic coupling of two coils with mechanical switch, which the extra driving coil to drive it unlike the previous hybrid SFCL was not required, was suggested. The operational principle of the suggested SFCL using magnetic coupling of two coils with the mechanical switch is basically the(More)