• Journal of Power Electronics
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• v.11 no.4
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• pp.520-526
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• 2011

This paper presents a balanced soft-chopping circuit and a modified PI controller for a high speed 4/2 Switched Reluctance Motor (SRM) with a 16 pulse per revolution encoder. The proposed balanced soft-chopping circuit can supply double the switching frequency in the fixed switching frequency of power devices to reduce current ripple. The modified PI controller uses maximum voltage, back-emf voltage and PI control modes to overcome the over-shoot current due to the time delay effect of current sensing. The maximum voltage mode can supply a fast excitation current with consideration of the hardware time delay. Then the back-emf voltage mode can suppress the current over-shoot with consideration of the feedback signal delay. Finally, the PI control mode can adjust the phase current to a desired value with a fast switching frequency due to the proposed balanced soft-chopping technology.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.889-894
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• 1997

A miniaturized wind-mill type ultrasonic motor which has diameter in 12.7 mm and thickness in 2.0mm using PMN-PZT piezoelectric ceramics was fabricated. The wind-mill type ultrasonic motors has only three plate and of two wind-mill shape slotted metal endcaps a rotor whose end is hollowed out so that its periphery fits with the shape of the stator and a bearing to guide the rotor. A Finite Element Analysis was carried out to obtain the endcaps behavior under a radial displacement change of piezoelectric disk and to optimize the structure of the number of slots. Increasing the applied voltage the revolution speed of ultrasonic motors was increased. The maximum speed of 700 rpm and the maximum torque of 0.22 nN·m of the wind-mill type ultrasonic motors were obtained.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.238-244
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• 2004

This research conducted milling tests to study effects of cutting environment conditions of ball end milts on the characteristics of high speed milling cutting process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semidry cutting using botanical oil coolant by the MQL(Minimum Quantity Lubricant) device were conducted. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that MQL spray cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than dry cutting did.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.10
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• pp.3482-3497
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• 2021

Artificial intelligence has emerged as the core of the 4th industrial revolution, and large amounts of data processing, such as big data technology and rapid data analysis, are inevitable. The most fundamental and universal data interpretation technique is an analysis of information through regression, which is also the basis of machine learning. Ridge regression is a technique of regression that decreases sensitivity to unique or outlier information. The time-consuming calculation portion of the matrix computation, however, basically includes the introduction of an inverse matrix. As the size of the matrix expands, the matrix solution method becomes a major challenge. In this paper, a new algorithm is introduced to enhance the speed of ridge regression estimator calculation through series expansion and computation recycle without adopting an inverse matrix in the calculation process or other factorization methods. In addition, the performances of the proposed algorithm and the existing algorithm were compared according to the matrix size. Overall, excellent speed-up of the proposed algorithm with good accuracy was demonstrated.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.925-931
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• 2016

The BLDC motor is used widely in industry due to its controllability and freedom from maintenance because there is no mechanical brush in the BLDC motor. Furthermore, it is suitable for high-speed applications, such as compressors and air blowers. For instance, for a compressor with a small impeller due to miniaturizing, the BLDC motor has to rotate at a very high speed to maintain the compression ratio of the compressor. Typically, to reach an ultra-high speed, airfoil bearings must be used in place of ball bearings because of their friction. Unfortunately, the characteristics of airfoil bearings change drastically depending on the revolution speed. In this paper, a BLDC motor with airfoil bearings is controlled with a PID controller. To analyze and determine the PID coefficients, the relay-feedback method is used. Additionally, for adaptive control, a fuzzy logic controller is used. Furthermore, the auto-tuning and self-tuning techniques are combined to control the BLDC motor. The proposed method is able to control the airfoil-bearing BLDC motor efficiently.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.22-24
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• 1996

Small size DC motor control method for portable drug delivery system has been developed to be used for the actuator of insulins pump. The control method gives the controllabilities both in high speed(40-50 revolution per second(rps)) DC motor drive and also in low speed(0.5-1rps). In low speed mode DC motor is controlled to act like stepping motor and in high speed to optimize power consumption. To control both mode modified bang bang control is suggested. Using this method small size DC motor(spec.) speed is controlled from 0.2 rps to 50 rps. Experimental setup is developed using micro-processor(PIC16C73, Micro Chips co., USA), motor turns checking circuitry, small size DC motor for pager(SM1012, Samhong co., Korea) and gear box. Results from experiment meet need for vailable load condition which is require for portable drug delivery system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.152-158
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• 2012

A newly developed attachment type high-speed spindle can be easily attached to the conventional CNC machining center to allow high-speed machining with low investment costs. This study has focused on the application of a conventional CNC machining center equipped with an attachment type high-speed spindle. A specimen of plastic mold material has been machined to compare the cutting effectiveness of the high-speed machining center and the conventional machining center with the attachment type high-speed spindle respectively. The rotational accuracy of the spindles are measured by a transmission optic measurement system and the surface roughness of the workpiece in accordance with revolution speed(rpm) of the spindle are investigated respectively. As the experimental results, it was shown that the surface roughness of the machined workpiece was $3.42{\mu}mR_{max}$, $0.46{\mu}mR_a$ in the case of attachment type spindle and $1.81{\mu}mR_{max}$, $0.275{\mu}mR_a$ in the case of the high-speed machining center. Moreover, the mean rotational accuracy was $7.57{\mu}m$ in the case of the attachment type spindle and $7.39{\mu}m$ in the case of the high-speed machining center.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.427-430
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• 2003

Nano drive control of five phase stepping motors is developed based on computational intelligence technology and it enables to drive into 5 million equiangular parts per revolution with keeping normal speed and torques. The experimental results of realizing high resolution/accuracy with low vibration and decreasing both heat loss and electric power consumption are mentioned.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.33-38
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• 2000

In process of tube spinning far shock absorber on vehicles, the selection of feed rate and rounding radius of forming roller and revolution speed of tube and forming roller, forming gap between die and forming roller are very important factors to obtain the optimal process result. In this paper, rigid-plastic FEM and UBET analysis are applied to verify effect of each factors by forming load. We can obtain the optimal conditions to prevent defects during processing.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.57-62
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• 1993

To increase the fuel economy, a reduction of friction loss is important in engines. Experimental investigations have been required for reducing the friction loss of crankshaft bearings. Hydraulic cylinder, and servo control ler system which modified the applied load, and test rig for the observation of the characteristics of engine crankshaft bearings were designed and fabricated. Experiment is performed. Friction torque, journal locus and circumferential temperature variations of crankshaft bearings were measured with appling load, revolution speed, and oil inlet temperature, etc.