Jung-Moo Seo

Design and Analysis of Slotless Brushless DC Motor

This paper presents a design method for a small-sized slotless brushless dc motor. Distributed hexagonal windings are employed for achieving a high torque density and for ease of manufacture. Numerical approaches with an analytic model are used to analyze the magnetic and output characteristics of the motor. The proposed motor is manufactured, and the empirical results are compared with the results of the simulation.

Analysis of Overhang Effect for a Surface-Mounted Permanent Magnet Machine Using a Lumped Magnetic Circuit Model

This paper presents a magnetic field analysis of a surface-mounted permanent magnet machine with an overhang structure wherein the rotor axial length exceeds that of the stator. A 2-D analytic method using a lumped magnetic circuit model (LMCM) is proposed for more rapid computation of the overhang effect compared with a conventional 3-D or quasi-3-D finite element analysis (FEA). In the LMCM, the effective overhang length is calculated, and a leakage flux generated in the overhang region is estimated. The accuracy and usefulness of the proposed analytic method is confirmed through the 3-D FEA and the experimental results according to the diverse overhang length, the number of slot/pole, and stator core length.

Design of axial flux permanent magnet brushless DC motor for robot joint module

Joint modules for robot system require actuators with high torque and slim topology for easy loading. Axial flux permanent magnet (AFPM) machine with high torque density is proposed and manufactured. Magnetic design is executed by numerical analysis and analytic model. Manufactured motor is tested and verified characteristics. Through the comparison with radial flux BLDC motor, we confirm the output performance is adequate for robot joint module.

A design of slotless BLDC motor for robot using equivalent magnetic circuit model

An analytical model for slotless brushless DC motors having four poles and twelve single coils is presented. To determine a back EMF constant of motor with hexagonal windings, winding forming factor taking into account winding shapes is introduced. The calculated results are verified with FE analysis and manufacturing through an example model, and electromagnetic parameters, such as EMF, motor constant with respect to the winding angles are analyzed.

Development of slotless type brushless DC motors and planetary gear heads for robot

This paper presents the development results for slotless type brushless DC motors and planetary gear heads for service and special purpose robot applications. The designed slotless BLDC motor has a hexagonal winding shape, and the developed motor sizes are 22, 32, and 40mm with the outer diameters. The developed gear heads are planetary type, and the gears are manufactured by the powder injection molding (PIM) method to increase the gear strength and to decrease the backlash. The output performances of the motors and gear heads are tested in various conditions.

Optimal design of piezoelectric transformer for high efficiency and high power density

The characteristics of piezoelectric transformer, such as resonance frequency, matching impedance, electromechanical coupling coefficient and efficiency, were analyzed using the finite element analysis along with the equivalent circuit. The validity of the proposed numerical methods was conformed experimentally. Through all of the verified results, the optimal design for a high efficiency and high power density was determined using the multi-modal optimization algorithm based on an evolution strategy.

Coupled electromagnetic-thermal analysis of a surface-mounted permanent-magnet motor with overhang structure

Overhang effects should be taken into account to predict performances and temperature distributions of a motor with an overhang structure. This paper investigates the electromagnetic and thermal characteristics of a surfaced-mounted permanent-magnet (SPM) motor with overhang. Moreover, the lumped-parameter thermal model (LPTM) considering overhang effects is proposed. Through the proposed LPTM, the computational time for thermal analysis is reduced considerably in comparison with computational fluid dynamics, and the temperature distributions of the motor are precisely predicted. The results calculated in coupled electromagnetic-thermal analysis are verified experimentally with a 100 W, 20-pole/24-slot SPM motor with overhang.

Design of brushless DC motor for variable valve actuation system of gasoline engine

This paper presents driving motor for variable valve actuation (VVA) system of gasoline engine. In order to meet the required specification and improve the performance of the actuating system, brushless DC (BLDC) motor is employed and designed. Ferrite permanent magnet with optimal pole and slot number is applied to reduce cost and increase thermal resistance. Designed motor is manufactured and the output characteristic is compared with that of the conventional DC motor, which verifies the superiority of the proposed BLDC motor.

A Novel Ultrasonic motor using Orthogonal Bimorphs

The main purpose of this paper is to describe a novel ultrasonic motor which is suitable for small information devices. With a bimorph structure having relatively large displacement, applied voltage and frequency could be reduced. From simulated results, such as mode and harmonic analysis, operating frequency and resonance mode are determined. In order to improve the performance of motor, several types of models are analyzed and experimental results are compared with simulated one

Electromagnetic and Thermal Analysis of a Surface-Mounted Permanent-Magnet Motor with Overhang Structure

Recently, overhang structures are increasingly used for various applications requiring high torque and power densities in a limited space such as traction motors of electric vehicles and servo motors of robot arms. In the design stage, overhang effects should be taken into account to predict the performances and the temperature rise of a motor with overhang. However, little research has been conducted on the thermal characteristics and analysis methods for a surface-mounted permanent-magnet (SPM) motor with overhang. To address this problem, the electromagnetic and thermal characteristics of the SPM motors with and without overhang are invested in this paper. Specifically, 3-D finite-element method is used in electromagnetic analysis to accurately calculate electromagnetic losses which are heat sources in thermal analysis. Moreover, the lumped-parameter thermal network (LPTN) which can consider overhang effects rapidly and precisely is proposed as an analytical method. Through the proposed LPTN, the computation time for thermal analysis is reduced considerably in comparison with a computational fluid dynamics method, and the temperature rise of the motors are precisely predicted. The results calculated in electromagnetic and thermal analysis are verified experimentally with 0.3 Nm, 20-pole/24-slot SPM motors adopting natural cooling.