Hyeong Joon Ahn

Development of a radial active magnetic bearing for high speed turbo-machinery motors

A radial active magnetic bearing system for a high speed turbo-machinery induction motor is presented. In this application, a massive rotor is required in order to make up high power and speed. So radial active magnet bearing should be designed to support this rotor mass. Precise analysis of a radial active magnetic bearing is presented from the point of view of electromagnets design. From the controller design point of view, the radial active magnetic bearing can be thought as a combination of two independent magnetic suspensions, each of which is made up of a differential magnetic actuator. Magnetic suspension system is open-loop unstable. So some control techniques like feedback stabilization with proportional-derivative (PD) controls are required in order to make the closed-loop system stable. In practical applications like high speed rotating machine, the proportional-derivative (PD) controls are compensated by 2n derivative control which reshapes the high-frequency end of the stiffness and damping of the system. In magnetic suspension system, massive rotor can act like static disturbance, which makes the center of the rotor out of the center of rotation. So an integral control algorithm is also required. Finally for the developed active radial bearing in turbo-machinery motor, the proportional-derivative-2n derivative-integral (PIDD) control algorithms are implemented with real-time simulator, and the test results are presented

Multi-Physical Analysis of Eddy Current Damper (ECD) for Reaction Force Compensation Device

This paper present multi-physical transient analysis of eddy current damper (ECD) for reaction force compensation device. A reaction force compensation mechanism with a movable magnet track and an ECD (or conductor plate) is developed. Lumped model of the ECD is derived and effects of both the location and width of the conductor plate are discussed. Multi-physical transient analysis of ECD is analyzed using commercial finite element software, which is compared with the lumped parameter analysis.

Hall sensor array for measuring displacement of a 2D magnet array

There are numerous cases where sensing signal is corrupted by harmonic components or a desired harmonic component is hidden in other harmonic signals. Therefore, various studies have been done in filtering or estimation algorithm to filter or extract harmonic signal. This paper presents sensor array for filtering of harmonic signals. First, 1D sensor array is introduced to filter n harmonic components. Then, 1D array is extended to 2D sensor array to filter out 2D harmonic signals. Finally, hall sensor array is built to measure displacement of a 2D magnet array and its performance is verified with experiments.