Publications (3)1.36 Total impact
Article: Rolling Motion Control of a Levitated Mover in a Permanent-Magnet-Type Bearingless Linear Motor[show abstract] [hide abstract]
ABSTRACT: A bearingless linear motor(BLLM) has no support elements such as a linear guide or additional linear magnetic bearing. Instead, it levitates a mover by controlling magnetic forces generated between the mover and stators as well as moves it. Its structure is very similar to a both-sided linear motor which is symmetrically combined of a common mover and two stators with permanent magnet arrays. Also the principle for movement is not quite different from that of conventional linear motors. But, to levitate the mover, the amplitudes of phase currents provided to both-side coils are controlled, based on the air gap between mover and stator. In this system, since the coils are divided into two groups in the movement direction and perform the levitation control separately, pitching motion of the mover can be controlled. And lateral translation and yawing motion are stable if the stable levitation were achieved. However, the rolling motion still needs to be stabilized by an additional control. Thus, this paper suggests a method to stabilize the rolling motion by using a pair of small electromagnetic actuators. It includes the actuator design method which is so as not to affect the BLLM performance, and the derivation of the equation of motion for controller design. Some experimental test results show that the rolling motion can be successfully controlled during levitation.IEEE Transactions on Magnetics 07/2010; · 1.36 Impact Factor
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ABSTRACT: Hidden Markov Model (HMM) has been actively studied in speech recognition since 1960s and increasingly used in many other fields. However, its application to mechanical engineering has been very limited. HMM is not only very accurate and robust in analyzing signals but also can be a very powerful method of predicting target system's condition change. In this paper, continuous HMM (CHMM) has been tuned to be used in mechanical signal analysis and applied to diagnose of various mechanical signals including rotor fault signals. The results show HMM's big potential as an intelligent condition monitoring tool based on its accuracy, robustness, and forecasting ability.Journal of Sound and Vibration.
Article: Operating characteristics of the bump foil journal bearings with top foil bending phenomenon and correlation among bump foils[show abstract] [hide abstract]
ABSTRACT: In many previous studies, the experimental results show the ripple traces of the post-test top foil due to the top foil deflection differences between the areas touched with and without bump foil. This phenomenon represents clearly the behaviour of the top foil motion. Therefore the top foil deflecting appearance should be taken into consideration for more reliable estimation of the bump foil bearing behaviour. However inherent top foil bending effect was ignored under assumption to the rigid body able to act only vertically. In this paper, a numerical analysis and its experimental investigation were studied with the intention to abstract the static and dynamic characteristics of the bump foil bearing considering the top foil bending effect and correlation among bumps. The bump and top foil inserted between the journal and the bearing housing have each mechanism as a shock absorber and journal supporter, and each mechanism was analysed using numerical method, respectively. In the case of the top foil, the deflection of that and Coulomb damping generated by relative friction was taken into consideration theoretically. In addition bump foil analysis was executed to be assumed to have a structure that flexible bumps with corrugated shape are connected with each other. This analysis verifies that the stiffness at the fixed end where the friction forces between the bearing housing and bump foil superpose is more than that at the free end. Using this structural analysis, the overall analysis of the bump foil bearing was executed through coupling process. In parallel, the experimental process was carried into execution with the bump foil bearing that L/D is 1. The rotating speed was from 10,000 up to 30,000 rpm and the load was 50 N. By comparing the analysis with the experimental results, the effects of the structural characteristics of bump foil were presented.Tribology International.