• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.57-64
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• 2000

In order to regulate cutting torque in milling, monitoring system should be set to a certain threshold. Radial immersion ratio is an important factor to determine the threshold and should be estimated in process for automatic regulation. In this paper, on-line estimation of the radial immersion ratio using spindle motor current in face milling is presented. When a tooth finishes sweeping, a sudden drop of cutting torque occurs. This torque drop is equal to the cutting torque acting on a single tooth at the swept angle of cut and can be acquired from cutting torque signals. Average cutting torque per revolution can also be calculated from cutting torque signals. The ratio of cutting torque acting on a single tooth at the swept angle of cut to the average cutting torque per revolution is a function of the swept angle of cut and the number of teeth. Using the magnitude of this ratio, the radial immersion ratio is estimated. Identical algorithm is adopted to estimate the immersion ratio based on the spindle motor current measurement. The experiments performed under different cutting conditions show that the radial immersion ratio can be estimated within 10% error range by the proposed method using spindle motor current. Varying immersion ratio is also estimated well using the presented algorithm.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.222-229
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• 1999

In order to regulate cutting torque in milling, monitoring system should be set to a certain threshold. Radial immersion ratio is an important factor to determine the threshold and should be estimated in process for automatic regulation. In this paper, on-line estimation of the radial immersion ration using spindle motor current in face milling is presented. When a tooth finishes sweeping, a sudden drop of cutting torque occurs. This torque drop is equal to cutting torque acting on a single tooth at the swept angle of cut and can be acquired form cutting torque signals. Average cutting torque per revolution can also be calculate form cutting torque signals. The ratio of cutting torque acting on a single tooth at the swept angle of cut to the average cutting torque per revolution is a function of the swept angle of cut and the number of teeth. Using the magnitude of this ratio, the radial immersion ratio is estimated. Identical algorithm is adopted to estimate the immersion ratio based on the spindle motor current measurement. The experiments performed under different cutting conditions show that the radial immersion ratio can be estimated within 10% error range by the proposed method using spindle motor current.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1223-1231
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• 2018

The direct torque control (DTC) scheme features a simple structure thanks to stator flux-oriented control. It has the advantage of robustness against motor parameters variation since only the stator resistance is involved in the control scheme. On the other hand, the disadvantage of DTC is large torque ripple. To reduce the torque ripple, many studies on DTC-space vector modulation (DTC-SVM) schemes, which modulate the duty ratio with a fixed switching cycle, have been proposed. However, there is the difficulty in obtaining the duty ratio for DTC-SVM. Hence, this paper proposes a new duty ratio selection and stator flux calculation methods for reducing torque ripple. Simulations and experiments were carried out to determine the validity of the proposed method. The proposed scheme has simplified the duty ratio command and achieved the same control performance as the conventional duty ratio modulation method without using the information of motor parameters.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.690-695
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• 2004

The present study is an investigation on the characteristics of heavy load toque converter by experimental process. To get the dynamic performance, the dynamometer was used with a parameters of speed, torque, oil pressure and oil flux, etc. The torque converter was tested for various input speed, output oil pressure and input oil flow rate. All experiments were investigated in case that the speed ratio is increased. The torque ratio and capacity factor was in inverse proportion to speed. Engine revolution had a more effects at region of low speed ratio. But, the opposite phenomena were represented increase of efficiency. In result of this experiments, the characteristics of torque converter were not influenced by oil pressure and oil flux.

• Journal of Korean Physical Therapy Science
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• v.8 no.2
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• pp.967-976
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• 2001

The purpose of the present study was to the investigate the effect of aging in men and women on muscle strength of knee extensor and flexors by using the cybex 6000 isokinetic dynamometer. A total of 100 volunteers participated in this study and were divided into five groups according to their chronological age as follows: 20s, 30s, 40s, 50s, 60s, 10 men and 10 women in each decade respectively. Isokinetic ($60^{\circ}{\cdot}s-l$) knee extensor and flexor peak torque, peak torque to body weight ratio, opposing muscles(flexor/extensor) peak torque ratio, deficit of peak torque between dominant and non-dominant were measured. The results obtained were as follows: 1) In men, While the aged increased. the peak torque of the knee flexor and extensor statistically sig nificant decreased in the dominant and non-dominant side. 2) In women, Statistically significant difference of knee extensor peak torque was found as the aged increased in the dominant and non-dominant side, but significant difference of knee flexor peak torque did not that. 3) In men, No significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the non-dominant side, but statistically significant difference in the peak torque of knee flexor to body weight weight ratio was found as the aged increased in the dominant side. 4) In women. No significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the dominant side, but statistically significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the non-dominant side. 5) In men and women, While the aged increased, statistically significant difference was found the dominant and non-dominant side in the peak torque of knee extensor to body weight ratio. 6) Peak torque of hamstring to quadriceps ratio of dominant and non-dominant side in men and women were not significantly different as the age increases. 7) Mean deficit of peak torque between dominant and non-dominant side in men and women were not significantly different as the age increases. From these results we conclude a proper exercise program is need before 50s decade to preserve in muscle strength of knee flexors and extensors.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.2
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• pp.81-87
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• 2005

The torque characteristics of permanent magnet(PM) motor is varied according to magnet width. In this paper, the design method of magnet and magnetic circuit is proposed in order to improve the torque of Interior Permanent Magnet Synchronous Motor(IPMSM). This paper presents the effects of pole arc ratio and salient pole ratio on the torque and torque ripple in the IPMSM with concentrated winding.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.9
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• pp.454-459
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• 2003

Conventional integral-slot design in permanent magnet(PM) motor tends to have a high cogging torque and large end turns, which contribute to copper losses. The fractional-slot design is effective compared to integral-slot design in the cogging torque and electromotive force(EMF) waveform. The effectiveness of fractional slot can be maximized by selecting optimal pole to slot ratio. This paper presents the effect of pole to slot ratio on the cogging torque and EMF waveform in the PM motor with fractional-slot. The effectiveness of the proposed designs has been confirmed by comparing waveform of EMF. cogging torque and torque ripple between conventional and new models.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.102-109
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• 2013

In this paper, a new torque predictive control method of interior permanent magnet synchronous motor is developed based on an extended rotor flux. Also, a duty ratio prediction method is proposed and allows the duty ratio of the active stator voltage vector to be continuously calculated. The proposed method makes it possible to relatively reduce the torque ripple under the steady state as well as to remain the good dynamic response in the transient state. With the duty ratio prediction method, the magnitude and time interval of the active stator voltage vector applied can be continuously controlled against the varying operation conditions. This paper shows a comparative study among the switching table direct torque control(DTC), the SVM-DTC, conventional torque predictive control, and the proposed torque predictive control. Simulation results show validity and effectiveness of this work.

• The KSFM Journal of Fluid Machinery
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• v.9 no.5 s.38
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• pp.36-41
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• 2006

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.3
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• pp.81-88
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• 1993

This report describes the experimental research on the flow phenomena of the aq uaous polymer solution within the Cuette flow of the concentric, cylinders type with a wide circular gap. We have investigated the phenomena of the fluid flow through torque measuring in the system that the inner cylinder is stationary and the outer one is rotating. Geometrical parameters of the system are the gap ratio of t/R$_{0}$=0.2 and Aspect ratio of l/t=100. The torque increases considerably in about 420-480RPM, So, it is considered a turbulent transition boundary, the higher plymer concentration is, the lower torque value is and the higher transition Reynolds number is. In each of the polymer concentration, the unstable boundary of torque, that is, idiosyncrasies of torque is observed around 220-280RPM. and the boundary is looked upon as a resonant vibration which is caused by the inner cylinder and tortional vibration of torque sensor.r.