• Journal of Magnetics
• /
• v.15 no.1
• /
• pp.36-39
• /
• 2010

The multi-degrees of freedom surface permanent-magnet motor (Multi-D.O.F. SPM) has several degrees of freedom operations that are defined as the "roll", "yaw", and "pitch". Normally, the torque that is generated to rotate a rotor includes ripples. The analysis of the torque ripples is important for improving motor performance. In terms of the electric analysis, torque ripple occurs as a result of many factors, including the rotor and stator structures, the distribution of the air-gap flux density, and the waveform of the current in the coils. In particular, the torque ripple is an important factor in the stable operation of the Multi-D.O.F. SPM. Therefore, in this work, the torque ripple was analyzed using various types of magnetization for the permanent magnet. An improved model was proposed for the Multi-D.O.F. SPM based on this analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.341-345
• /
• 1996

Many mechanical and electrocal systems use the number of motors to make multi degree of freedom motion. One method to reduce the number of motors is suggested by using the 3 D.O.F. motor. The 3 D.O.F. motor has advantages such as downsize, weight reduction, and simplification of the existing 3 D.O.F. systems. In this study, a mathematical model for the 3 D.O.F. motor is suggested and the dynamic equation is derived to analyze the 3 D.O.F. motion. Generallinear control methods are very hard to get the good performance because of the nonlinear terms of each degree of each degree of freedom. To control the motion properly, the nonlinear terms are decoupled using a feedback control law. Nonlinear feedback control law which can arrage the poles arbitrarily is derived. The effects of the gains are examined through computer simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.627-628
• /
• 2012

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.6
• /
• pp.202-214
• /
• 1997

In automotive industries, one of major issues is the shifting shock, which is brought out when two clutches are engaged in an automatic transmission. The engagement and disengagement if two clutches means the variation of the D.O.F(degree of freedom) of system. Therefore to analyze the shifting performance, the variation of D.O.F should be considered in detail. Generally, the programs for analyzing the shifting transients have been developed as the problem-dependent codes because the artificial maris were usually used to indicate the change of shifting phase. To develop a software applicable to a general mechanism of transmissions, a self-determining algorithm of D.O.F must be applied. Through the experiences for the last several years, a generalized analysis software of shifting mechanism(so called by POTAS-MSM Version 2.0) has been developed. In this study, some major ideas of the software and the concept for the analysis of shifting characteristics are presented. In addition to that, this paper shows how to self -determine D.O.F of he multi-slipping systems using the stick-slip criterion on a single slipping mechanism. By using this software, the shifting characteristics of a vehicle are analyzed and compared with the experimental results.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.5
• /
• pp.65-73
• /
• 2001

In this paper, a mobile system using multi-wheel steering and driving mechanism is proposed to maximize maneuverability of the wheeled mobile system. Among various possible configurations, the two-wheel steering and driving systems, which is minimal in structural requirement, is proposed to reduce the complexity in actual design and difficulties in control. The system possesses three or four degrees of freedom depending on the orientations of two wheels, one or two for driving and two for steering, which implies that the system's mobility is always less than three DOF. The proposed system, nonetheless, can exactly emulate characteristics of the omnidirectional motion as long as the planned path is smooth i.e., the curvature changes continuously while velocity is not zero. Efficient kinematic and dynamic control algorithms are proposed for position and orientation control of the proposed wheeled mobile system.

• Journal of Institute of Convergence Technology
• /
• v.1 no.1
• /
• pp.18-23
• /
• 2011

Shaping an input command through considering the resonant modes of multi degrees of freedom system, it is possible to realize the wanted motion, without exciting the uncontrollable modes of the flexible system. But, an increase of modes to be considered brings inevitably about the time delay due to an excessive rising time. On the purpose of reducing the rising time, only the interesting and dominant modes can be considered to determine the timing pulses of input shaper. In this paper, an effect of shaper by the partial modes is analysed for a specific system and the input shapers by the partial modes are analysed for three d.o.f damped system, using Matlab simulation.

• Proceedings of the KIEE Conference
• /
• 2008.10c
• /
• pp.6-8
• /
• 2008

Electrical machineries have been developed as following with various and high technical application in these days. Especially the robot is integrated system including mechanical structure, electronic control, and electrical technology. The robot system is not compact and has not natural motion like human, although the technology of robot has been developing continuously. The spherical wheel motor is useful electric machine for using robot joint as operation of 3-degrees of freedom. In this paper, a permanent magnet spherical wheel motor is introduced and performance characteristics are analyzed for improving of operation stability.

• Journal of computational fluids engineering
• /
• v.10 no.2
• /
• pp.38-47
• /
• 2005

Substructuring methods are often used in finite element structural analyses. In this study a multi-level substructuring(MLSS) algorithm is developed and proposed as a possible candidate for finite element fluid solvers. The present algorithm consists of four stages such as a gathering, a condensing, a solving and a scattering stage. At each level, a predetermined number of elements are gathered and condensed to form an element of higher level. At the highest level, each sub-domain consists of only one super-element. Thus, the inversion process of a stiffness matrix associated with internal degrees of freedom of each sub-domain has been replaced by a sequential static condensation of gathered element matrices. The global algebraic system arising from the assembly of each sub-domain matrices is solved using a well-known iterative solver such as the conjugare gradient(CG) or the conjugate gradient squared(CGS) method. A time comparison with CG has been performed on a 2-D Poisson problem. With one domain the computing time by MLSS is comparable with that by CG up to about 260,000 d.o.f. For 263,169 d.o.f using 8 x 8 sub-domains, the time by MLSS is reduced to a value less than $30\%$ of that by CG. The lid-driven cavity problem has been solved for Re = 3200 using the element interpolation degree(Deg.) up to cubic. in this case, preconditioning techniques usually accompanied by iterative solvers are not needed. Finite element formulation for the incompressible flow has been stabilized by a modified residual procedure proposed by Ilinca et al.[9].

• Journal of Ocean Engineering and Technology
• /
• v.25 no.6
• /
• pp.116-122
• /
• 2011

A realtime simulator using an explicit integration method is introduced to improve the solving performance for the dynamic analysis of a wheeled vehicle. Because a full vehicle system has many parts, the development of a numerical technique for multiple d.o.f. and ground contacts has been required to achieve a realtime dynamics analysis. This study proposes an efficient realtime solving technique that considers the wheeled vehicle dynamics behavior with full degrees of freedom and wheel contact with soft ground such as sand or undersea ground. A combat vehicle was developed to verify this method, and its dynamics results are compared with commercial programs using implicit integration methods. The combat vehicle consists of a chassis, double wishbone type front and rear suspension, and drive train. Some cases of vehicle dynamics analysis are carried out to verify the realtime ratio.