• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1541-1543
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• 2013

This paper presents a spherical motor which can control in multi-degree of freedom operation. The spherical motor has been researched by many types of structure. Thhis paper shows a spherical shaped airgap and surfaced permanent magnets. Especially, The motor consists of dual rotor cores. Unlike a cylindrical motor, the spherical motor design can be considered with azimuth direction on spherical coordinates. Therefore the permanent magnet surfaced on the rotor need to be designed optimally in order to generate a sinusoidal magnetic flux density in the airgap. This paper presents results of optimal design for reducing torque ripple of the multi-degree of freedom spherical motor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.33-39
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• 2003

The stiffness of multi-articulated industrial robots is very weak, because their structure is an articulated type with some links and joints. Thus it is known that cutting processes for metals are not accepted in machine shop well, but they have a lot of merits for cutting processes, for example, drilling, tapping, and engraving etc, because of the characteristics of their high degree of freedom. The temptation of cutting aluminium was carried out to investigate the feasibility and the limitations or constraints for cutting metals on them. First the mode shapes of 6 degree of freedom welding robot were taken and analysed, and next the cutting processes were practically carried out on it. The results of study were found out to show the feasibility of cutting processes at drilling under 6mm of tool diameter, as well as to have some limitations and constraints, for examples, feed rate, depth of cut and cutting force etc.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.377-378
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• 2002

In many dynamic systems, unwanted vibrations which may arise during operation of machines are costly in terms of reduction of performance and service life. Sometimes these risky oscillations endanger equipment and personnel. When hydraulic telescopic booms taken large mass are driven at slow speeds between the two pads, unstable oscillations occur through the stick-slip at the sliding parts and become more severe and saw-toothed. This paper supposes few models for the telescopic boom in the multi-degree of freedom system, and attempts a theoretical approach for the numerical analysis in its stick-slip condition, It was verified that this theoretical approach has an effect on estimate of stick-slip in the one-degree as well as multi-degree of freedom system.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.230-233
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• 1999

This paper is concerned with the design method of a de-centralized linear control system and its application to vibration control of multi degree of freedom structures. The method is based on the partial model matching on frequency domain by minimizing the relative model error functions between the diagonal elements of the open loop transfer function matrix of the control system and these of the reference model. The method is examined and evaluated by both simulation and experiment of a multi degree of freedom structure(MDFS).

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.415-419
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• 2000

Multi-degree-of-freedom (MDOF) displacement measurement Is needed In many application fields: precision machine control, precision assembly, vibration analysis, and so on. This paper presents a new MDOF displacement measurement method using a laser diode (LD), two position-sensitive detectors (PSDs), and a conventional diffraction grating. It utilizes typical features of a diffraction grating to obtain the information of MDOF displacement. MDOF displacement is calculated from the independent coordinate values of the diffracted ray spots on the PSDs. Forward and inverse kinematic problems were solved to compute the MDOF displacement of a rigid body. Experimental results show maximum absolute errors of less than ${\pm}10$ micrometers in translation and ${\pm}30$ arcsecs in rotation.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.18-24
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• 2000

As ship's propulsion shafting system has been complicated, many linear methods that have been used until now are not sufficient enough to produce proper solutions and these solutions are ofter unreasonable. So we need to solve nonlinear systems, and many methods for solving nonlinear vibration system have been developed. In this study, the propulsion shafting system was modeled with Duffing's nonlinear vibration system and multi-degree-of-freedom, and analyzed by using Quasi-Newton method. And for the purpose of confirming the reliability of the calculating results for nonlinear forced torsional vibration of the propulsion shafting system, the nonlinear calculated results were compared with the linear calculated ones for ship's propulsion shafting system. In the result, for analysis of the forced torsional vibration of the propulsion systems with nonlinear elements, the modified Newton's method is confirmed reasonable.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.643-650
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• 2014

A chaotic vibration isolation system is designed according to the chaotic vibration theory in this paper. The strong nonlinearity is generated by the system. Line spectra in the radiated noise maybe easily detected caused by marine vessels. It is Important to reduce the line spectra by improving the acoustic stealth of marine vessels. A multi-degree-freedom (MDF) nonlinear vibration isolation system (NVIS) system is setup by the experiment and finite element method. The model is established with finite element method. The results show that the behavior of the device gradually varies from period bifurcation into chaotic state and the line spectrum is changed from single spectral structure into broadband spectral structure. It is concluded that chaotic vibration isolation is preferable contrasted on line spectra isolation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.50-56
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• 2012

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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.280-289
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• 2005

A single degree of freedom system and transmissibility are key concepts in many problems of vibration isolation. In order to apply this approach, however, several assumptions must be satisfied, which are often not realistic. For examples, in practical systems, vibration transmissions at multi-point with multi-degree of freedom(translational and rotational DOF) take place and mobilities or impedances of receiver structures cannot be ignored any more especially over high frequency range. Therefore, a multi-dimensional treatment is required for accurate estimation of dynamic behavior of the system. In this paper, an approach using vibrational power flow is introduced to deal with analysis of multi-dimensional vibration isolation system in a more practical way and in aspects of vibration isolations and vibration path analysis. Procedures of this approach and some results of research for vibrational power path analysis with rotational terms included are presented. Difficulties in this method are also discussed.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.12-18
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• 2006

A three-degree of freedom model of intake system was contrived and investigated in various ways for the purpose of the amelioration of the volumetric efficiency in a low and transient engine speed for a multi cylinder diesel engine. The basic concept beyond this model started from the theory that each degree of freedom model has volumetric efficiency peak as many as its number of the degree of freedom. The volumetric efficiency affects significantly to the engine performance; torque characteristics, fuel economy and emission level. For commercial vehicles and stationary engines, the engine is designed so as to produce their best performance near the normal engine speeds, thus the low engine speed area has a tendency of poor volumetric efficiency. The aim of this study was highlighted on the amelioration of volumetric efficiency of low engine speed area in a multi cylinder diesel engine matched with an additional Helmholtz resonator. By the use of VIS(variable induction system) volumetric efficiency at low engine speed range was significantly improved. The availability of control by combination of VIS and CIS(conventional induction system) will be proposed as a variable induction system that would be an appropriate model for amelioration of the volumetric efficiency at low engine speed.