• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.335-340
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• 2008

In this study, novel structured thin ultrasonic rotary motor has been proposed. Ultrasonic motors are based on an elliptical motion on the surface of elastic body. Thin brass plate was used as a cross shaped vibrator and eight ceramic plates were attached on upper side and bottom side of the brass plate. From the thin stator, elliptical displacements of the four contact tips were obtained. To find the optimal size of the stator, motions of the motors were simulated using ATILA by changing length, width and thickness of the ceramics. The stators had commonly three resonance peaks and contact tips of the stator moved on tangential or normal trajectories at these resonance peaks. The maximum displacements at the resonance peaks were compared. As results, maximum displacements of the contact tips were obtained at the length of 16 mm, width of 6 mm and thickness of 0.4 mm. Changes of the resonance frequencies were inversely proportional to the length of ceramic and proportional to the width of ceramic. The motor was fabricated by using the designed stator. And, the characteristics of the motor were compared with the simulated results. When the motor was fabricated with these results, speed fo 935 rpm was obtained by input voltage of 25 Vrms at 93.5 kHz.

• ETRI Journal
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• v.41 no.6
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• pp.838-849
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• 2019

We present a permanent magnet-based spherical wheel motor that can be used in omnidirectional mobility applications. The proposed motor consists of a ball-shaped rotor with a magnetic dipole and a hemispherical shell with circumferential air-core coils attached to the outer surface acting as a stator. Based on the rotational symmetry of the rotor poles and stator coils, we are able to model the rotor poles and stator coils as dipoles. A simple physical model constructed based on a torque model enables fast numerical simulations of motor dynamics. Based on these numerical simulations, we test various control schemes that enable constant-speed rotation along arbitrary axes with small rotational attitude error. Torque analysis reveals that the back electromotive force induced in the coils can be used to construct a control scheme that achieves the desired results. Numerical simulations of trajectories confirm that even without explicit methods for correcting the rotational attitude error, it is possible to drive the motor with a low attitude error (<5°) using the proposed control scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2008-2013
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• 2016

This paper proposes analysis and suppression method for reactive power vibration of the slave motor caused by back-EMF mismatch between the master and the slave motor and stator resistance during middle-low speed operation. The master and slave motors are parallel connected dual SPMSMs(Surface mounted Permanent Magnet Synchronous Motors) fed by a single inverter. To suppress vibration of reactive power, RPC(Reactive Power Compensator) proposed in this paper analyzes flux-axis current vibration of the slave motor that occurs in middle-low speed operation using a mathematical model of the fan motor. And RPC adds vibration components detected from flux-axis current of the slave motor to flux-axis current of the master motor. The results of experiment conducted verify the efficacy of the proposed method.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.2
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• pp.211-216
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• 2018

This paper presents a numerical optimization technique and switching phase control technique aiming at improvement of efficiency of the low voltage BLDC motor. The optimization technique is performed using the generalized sensitivity technique, response surface method(RSM) and sampling minimization technique. In order to minimize current consumption of the BLDC motor, the switching method of the driving device is optimized using RSM with finite element analysis. The ratings of BLDC motor are 50 W, 24 V, 1200 rpm. As optimizing results, the input current is reduced from 2.78 to 2.51 [A] when the switching phase is shifted by -2.65 [DEG_ELC] at the rated driving speed of 1200 [rpm]. It is confirmed that the proposed method reduces the consuming current of the low voltage BLDC motor through switching phase control method using the numerical optimization method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.274-275
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• 2006

A linear ultrasonic motor was designed by a combination of the longitudinal and bending mode. Linear ultrasonic motors are based on an elliptical motion on the surface of elastic body, such as bar or plates. The corresponding eigen-mode of one resonance frequency can be excited twice at the same time with a phase shift of 90 degrees in space and time. That is excite symmetric and anti-symmetric modes. Then it determines the thrust and speed of the motor. Linear ultrasonic motors are investigated experimentally in according to be fabricated a general classification to motor structure and material characteristic. There was the first to simulate as use of finite element analysis ANSYS 9.0. The AL-T2W8-ARM14-LEG18-ANGLE80 motor has a maxim efficiency 17 [%] under the speed 0.14 [m/s], thrust 345 [gf] and preload 280 [gf], operating frequency is 57.6 [kHz].

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.158-165
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• 2004

The DC motor in a vehicle may cause noise and vibration because of high speed revolution, which can make a driver feel uncomfortable. There have been various studies attempting to solve these problems, focusing mostly on the causes of and ways to reduce noise and vibration. It is suggested that the noise in a DC motor may be primarily due to interaction between a brush and a commutator. Brush noise, the most common noise in a DC motor, results from a brush bounced from the surface of the commutator, fluctuation of the friction between the brush and the commutator, and the impact on the brush when passing over slots of the commutator. Based on the noise test, one of the most important design parameters was shown to be the roundness of the commutator. As the DC motor is used, the roundness of the commutator gets bigger with subsequent increase of the level of brush noise and vibration. There must be a threshold in order to prevent the brush noise from getting worse. Using the method of CAE is more efficient than the real test for purposes of looking for various design parameters to maintain the roundness of the commutator. In this study, the design process to reduce the brush noise is presented with the use of a computer model. The design parameters to reduce the brush noise and vibration are proposed by using FEM. The design parameters are used to reduce the noise and vibration of a DC motor and it is verified with the test results on a fan DC motor in a vehicle. This method may be applicable to various DC motor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1173-1179
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• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.373-385
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• 2004

Statement of problem: The microbial adhesion on the surface of materials used in prosthodontics and restorative dentistry significantly influences microbial infection. Purpose: The purpose of this study was to evaluate the effect of how the degree of surface roughness of acrlyic resin affect the adhesion of bacteria. Material and methods: Resins were finished with $50{\mu}m$ and $250{\mu}m$ aluminium oxide particles by using sandblaster, by using stone point, and high polished with $Opa^{(R)}$ and Lace $motor^{(R)}$. The surface of acrylic resin attached by bacteria was directly touched on the surface of BHI agar, which was incubated. Bacteria colonies formed on BHI agar were counted in accordance with the degree of the surface roughness. Results: 1. The viable cell number of Streptococcus mutans increased on the acrylic resins incubated in BHI broth than in PBS. 2. The viable cell number of Streptococcus mutans increased on the acrylic resins incubated without agitation than with agitation, washed three times than six times, and incubated in broth added with 5% sucrose than without sucrose. 3. When Streptococcus mutans incubated in BHI broth, the number of Streptococcus mutans colonies formed on BHI agar was the largest on the acrylic resins finished with $250{\mu}m$ aluminium oxide particle using sandblaster. But when incubated in BHI broth containing sucrose, the number of colonies formed on that was the largest on the acrylic resins high polished using $Opal^{(R)}$ and Lace $motor^{(R)}$. 4. When Streptococcus sanguis was incubated in BHI broth with or without sucrose, the number of Streptococcus mutans colonies formed on BHI agar was the largest on the acrylic resins finished with $250{\mu}m$ aluminium oxide particle using sandblaster. 5. When Actinomyces viscosus was incubated in BHI broth with or without sucrose, the number of Streptococcus mutans colonies formed on BHI agar was the largest on the acrylic resins high polished using $Opal^{(R)}$ and Lace $motor^{(R)}$. Conclusion: These results indicated that when acrylic resins attached by bacteria were touched on the surface of BHI agar, the number of bacterial colonies formed on the agar was dependent on the bacterial species. Also, the result of this study was showed that increase in the surface roughness and the addition of sucrose increased retention of microbial cells.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.2
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• pp.141-147
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• 2015

This paper deals with thermal characteristic analysis of induction motors for machine tool spindle for motion error prediction. Firstly, the inverse design of general induction motors for machine tool spindle has been performed by design principles. Characteristics considering VVVF inverter of induction motors were analyzed. Secondary, power loss and thermal characteristics of induction motors analyzed by equivalent thermal resistance model from Motor-CAD S/W. To develop a second-order fitted power-loss distribution model for the constant-torque operating range of the induction motor, we employed the design of experiment and response surface methodology techniques. Finally, the analysis results were experimentally verified, and the validity of the proposed analysis method was confirmed.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.6
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• pp.453-462
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• 2016

This paper proposes a torque control method for surface mounted permanent magnetic synchronous motor (PMSM) driven by a 2-level voltage source driven inverter, which has fast torque response and small torque ripple. The proposed torque control method follows the finite control set model predictive control (FCS-MPC) strategy. A reference state is derived at each time step for the given time varying torque reference and the cost index is defined so that the tracking error for this reference state should be penalized. The choice of an optimal output voltage vector is made first from the 6 possible active voltage vectors of the 2-level voltage source inverter. Then a modulation factor for the chosen optimal voltage vector is obtained so that the torque ripple can be reduced further. It is shown that the proposed FCS-MPC control method yields fast torque tracking response and small torque ripple through simulation and experiments.