• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.4
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• pp.409-416
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• 2007

A momentum type actuator produces force and torque disturbances as well as its designed control torque. These disturbances are ones of the largest disturbance sources inside the spacecraft, which deteriorate the pointing stability of the high precision spacecraft. The measurement and analysis of actuator disturbances are therefore imperative for such a spacecraft, and thus a three dimensional torque measurement table has been developed for that purpose. The data acquired from the measurement table are processed in the frequency domain and displayed in the power spectral density(PSD). Through this process, disturbance model parameters are obtained and used for the attitude stability simulation. The process has been adopted for the disturbance measurement of the reaction wheel, and the validity of measurements and parameter identification procedure is verified.

• Journal of Industrial Technology
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• v.18
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• pp.289-293
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• 1998

In a independent joint servo control of robots, the performance of the control is influenced greatly by the joint interaction torques including Coriolis and centrifugal forces. These act as disturbance torques to the control system. As the speed of the robot increases, the effect of this disturbance torque increase, and makes the high speed - high precision control more difficult to achieve. In this paper, a solution to the optimal path placement problem is presented that minimizes the joint disturbance torque during a straight line motion. The proposed method is illustrated using computer simulation. The proposed solution method can be applied to the class of robots that are controlled by independent joint servo control, which includes the vast majority of industrial robots.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.8
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• pp.358-363
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• 2005

This paper presents the reasonable design parameters of a switched reluctance motor to drive a hybrid electric vehicle by using the equivalent magnetic circuit method. The designed motor can be redesigned by using finite element analysis as a variation of the parameter for the purpose of improving performance. This paper shows that a flat-topped current of a phase can be made from a change of the lamination stack length for high average torque and a lower torque ripple. The change of current falling time as a variation of turn-off angle was shown by finite element analysis. The core loss and copper loss were described. The torque of the redesigned motor is suitable for low and high speed ranges to drive a HEV. which is verified by the speed-torque curve.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.321-326
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• 2005

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications, due to their excellent power to weight ratio. The paper is proposed maximum torque control of IPMSM for high speed drive. The control method is applicable over the entire speed range and considered the limits of the inverter's current and voltage rated value. For each control mode, a condition that determines the optimal d-axis current $^i{_d}$ for maximum torque operation is derived. The proposed control algorithm is applied to IPMSM drive system for high speed drive, the operating characteristics controlled by maximum torque control are examined in detail by experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.181-183
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• 2000

Ultrasonic Motors of Wind-Mill type(diameter in 11.35mm, thickness in 2.8mm, and 1.44g weight) using Piezoelectric Ceramics have been developed. In recent study, Maximum torque in 100$V_{max}$, 105.8kHz was 7.2 ${\mu}$N$.$m, and bidirectional revolution using single-phase AC was presented. However, it is difficult to use because of small torque. Thus, in present study, new type of Wind -Mill Type Ultrasonic Motor of was designed as stator' structure was changed

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.125-127
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• 2001

Switched reluctance motor (SRM) has some advantages such as low cost, high torque density etc. However SRM has inevitably high torque ripple due to the double salient structure. To apply SRM to industrial field, we have to minimize torque ripple, which is the weak-Point of SRM. This paper presents optimal design process of SRM using numerical method such as 2D finite element method (FEM) and 3D equivalent magnetic circuit network method (EMCNM). The electrical and geometrical design parameters have been adopted as 2D design variables. The overhang structure of rotor has been also adopted as 3D design variable. From this work, we can obtain the optimal design, which minimize the torque ripple and maximize energy conversion loop.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.122-125
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• 2005

A novel torque ripple reduction scheme of single-phase SRM with high power factor is presented. The proposed SRM drive has one additional active switches in the conventional asymmetric inverter. In order to get a higher power factor, the source current is controlled sinusoidal, And additional excitation current is added from charge capacitor due to torque ripple reduction. The switching period of source and charged voltage is controlled properly to get unity power factor and torque ripple reduction. The characteristics and validity of the proposed scheme is discussed with some simulation results.

• Journal of Magnetics
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• v.20 no.1
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• pp.91-96
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• 2015

As many researchers are relentlessly trying to improve the power generation schemes from the power grid, to meet the constantly increasing electricity demand. In this paper, the results of a finite element analysis are carried out to study on a design optimization of an asymmetric air-gap structure in 3-phase Permanent Magnet Brushless DC Motors. To achieve a high efficiency for a 3-phase PM BLDC motor, the asymmetric air-gap structure is proposed considering the rotation direction of a motor. Generally, a single-phase BLDC motor is applied asymmetric air-gap structure for starting. This is because the asymmetric air-gap structure causes reluctance variation so the motor can utilize reluctance torque toward a rotation direction. In this paper, the asymmetric air-gap is applied to 3-phase BLDC SPM motor so it utilizes reluctance torque with alignment torque. A proposed model is designed by 2-D FE analysis and the results are verified by experimental test.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.139-145
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• 1996

Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.243-246
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• 2003

This paper presents a new motor design well suited for an advanced exercise bike. The advanced exercise bike setup high demands for performance and physical dimensions, which is high torque, wide speed range and a diameter/length ratio around 5. These requirements makes the new motor design called an E-core Transverse Flu Machine (ETFM) vev interesting because the segmented design of the stator and rotor poles enables high diameter without increasing the flux-path and since the ETFM is similar to the switched reluctance motor, high torque and wide speed range is possible. The design of the ETFM can be peformed using a developed design program, which is also introduced in the paper. A prototype of the exercise bike with the ETFM and a classical H-bridge converter with analog current control is constructed for verification of the concept.