Ho-Joon Lee

A Performance Study on a Permanent Magnet Spherical Motor

To realize the multi-Degree-of-Freedom (multi-DOF) movement, researches on spherical motor have been conducted in many countries. The Spherical motor has a 3-DOF, whose shaft can not only rotate as rotary motor but also tilt in the 2-DOF space. Researches on spherical motor will greatly contribute to 3-DOF systems, because spherical motor can reduce the size and weight of 3-DOF systems. This paper studies a new type of spherical motor that has rotating coils and tilting coils. Also, the current function depending on shaft angles is proposed. Finally, the torque is calculated corresponding to different shaft angles and rotating speeds. Moreover, these performances are validated via experiments.

An Analytic Analysis of the Multi-Degree-of-Freedom Actuator

This paper discusses the analysis and simulation method and the test method for a two-degree-of-freedom (2-DOF) actuator torque. The previous studies on the analysis of 2-DOF motors tilting torque were carried out only by finite element method (FEM), not by analytic method. This paper describes the operating principles of and the processes of inducing a tilting torque and a holding torque both of which exist only in special purpose electric machines. This allowed us to establish a design process. By overcoming the limits of the 3-D FEM, this paper introduced the 2-D model analysis by considering a real coil shape. Finally, this paper manufactured and tested the 2-DOF actuator to verify the introduced analytic analysis method.

Newly proposed hybrid type mutli-DOF operation motor for multi-copter UAV systems

Previous researches have been conducted on the multi-degree of freedom operation motor, a new mechanism for power conversion out of the existing motor from early in 2000. Various types of structure have been suggested to operate more than two-degree of freedom (DOF) from one point of action and control methods have been studied appropriately for each structure. This led to overall improvement in interpreting the multi-degree of freedom for drive motor and the ability to interpret the operating characteristics, but few applications have been development practically. On the other hand, UAV systems like a multi-copter and drone, which is the biggest issue recently, are considered to be the field of applications that can maximize the effects if applying the multi-degree operation motor being studied now. This paper investigates the generic technology and suggests a new hybrid type multi-degree of freedom operation motor with increased tilting torque, improved practicality, and easy control in the commercialization stage that requires more than two-degree of freedom for application to the driving motor. In other words, rotational driving and tilting driving were separated electromagnetically to improve manufacturability and ease control and the characteristics of various tilting operating actuators were discovered for increasing the tilting torque. Finally, such a suggested hybrid type multi-degree of freedom operation motor was designed, manufactured, and tested to verify its performance. At the same time, the necessity of multi-degree of freedom operation motor in the multi-copter system, a field of application expected was discovered and the system modeling was conducted.

Improvements of Performance of Multi-DOF Spherical Motor by Double Air-gap Feature

As the need of electric motor is increased rapidly throughout our society, the various application fields are created and the service market called robot gets expanded as well as the existing industrial market. Out of those, the joint systems such as humanoid that is servo actuator for position control or all fields which require multi-degree of freedom (multi-DOF) require the development of innovative actuator. It is multi-DOF spherical motor that can replace the existing system in multi-DOF operating system. But, multi-DOF spherical motor that has been researched up to date is at the stage which is insufficient in performance or mechanical practicality yet. Thus, first of all the research results and limitation of the previously-researched guide frame-type spherical motors were analyzed and then the feature of double air-gap spherical motor which was devised to complement that was studied. The double air-gap multi-DOF spherical motor is very suitable spherical motor for system applying which requires the multi-DOF operation due to its simple structure that does not require other guide frame as well as performance improvement due to its special shape which has two air-gaps. So, the validity of the study was verified by designing and producing it with 3D-FEM through the exclusive jig for multi-DOF spherical motor.

High-Speed BLDC Motor Design for Suction Fan and Impact on the Loss caused by Core Welding

This paper deals with the effects of welding, which is done to fix the stator stack, on a motor in case of fabricating a prototype motor that is manufactured in a small quantity. In the case of a small motor, the stator is designed and fabricated with the segmented core as a way to raise the fill factor of winding wire to the utmost within a limited size. In case of fabrication by welding both inside and outside of the stator in order to fix the segmented-core stator, the effects of stack are ignored, and the eddy current loss occurs. This paper performed the no-load test on an IPM-type BLDC motor for driving the suction fan of a vacuum cleaner, which was manufactured by using a segmented-core stator. As a result of the test, it was found that input power more than expected was supplied. To analyze the effects of welding by using the finite element analysis method and verify them experimentally, a stator was re-manufactured by bonding, and input power supplied during the no-load test was compared.

Improve of Efficiency of Multi D.O.F Spherical Motor Through the Reduction of Eddy Current Loss

The Multi D.O.F spherical motor can drive rotating as well as tilting three degree of freedom with one motor. Existing three degree of freedom to drive with three motors that are connected by gears and belts, that will be too large size and big loss at gears and belts. So Reducing system size and improving efficient is using the Multi D.O.F spherical motor in three degree of freedom systems. For this reason, efficiency of Multi D.O.F spherical motor is one of the important performance indiccators. In this paper presented that how to improve the efficiency of the Multi D.O.F spherical motor. The fist of method is using the stator iron core`s material with high permeability and resistivity for reducing the eddy current loss. However, it was the disadvatages of motor-making and economic. So author propose the resonable method of reducing the eddy current loss in the stator iron core. That is using the rotor with double-air gap.

Analysis Torque Characteristics and Improved Efficiency of Permanent Magnet Multi-D.O.F. Spherical Motor

Abstract - A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robots arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.Key Words : Multi-D.O.F., Spherical motor, Soft magnetic composite, Torque characteristic, Permanent magnet motor*정 회 원 : 한양대 공대 전기공학과 박사과정** 정 회 원 : 동국대 공대 전자전기공학부 교수***정 회 원 : 한양대 공대 전기공학과 석박사 통합과정§ 정 회 원 : (주)삼성전자 선임연구원§§ 정 회 원 : 동양미래대 공대 전기시스템과 전임강사† 교신저자, 시니어회원 : 한양대 전기공학과 교수E-mail : julee@hanyang.ac.kr접수일자 : 2011년 9월 18일 최종완료 : 2011년 12월 9일