• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.7
• /
• pp.899-903
• /
• 2013

A self-bearing is an electric machine that achieves both rotational actuation and magnetic levitation using a single magnetic structure. To be able to stably levitate the rotor in a self-bearing, one needs to have an inverse of the force-current model. However, the force-current model in a self-bearing motor is typically not square. Furthermore, the elements of the matrix vary with respect to the rotational angle, resulting in singularities of the pseudo-inverse at various angles. In this paper, we propose a new force-current model that eliminates the singularities by adding a constraint in coil currents. This constraint eliminates the flux density in the stator core so that the saturation problem in the previous study is avoided. By implementing this force-current model, we are able to implement a levitation controller for a toroidally-wound self-bearing BLDC motor. The model inversion and levitation are validated experimentally.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.5
• /
• pp.373-379
• /
• 2016

Hydraulic forces on a vessel are changed according to the depth/draft ratio (h/d) during berthing or towing in a lateral direction. It is well known that lateral current force coefficient is dependent on the kinds of vessel in question. However, not much research exists about the characteristics of general ships, except for oil tankers, as suggested by the Oil Companies International Marine Forum (OCIMF). In this paper, lateral current coefficient related to h/d is analyzed in comparison with theoretical values and experiments with a 93m passenger ship. The estimated total resistance on the ship was 14.0 tons under an h/d of 1.6 with a lateral current force coefficient of 1.9. This was found to be similar to the measured value of 13.8 tons on the towing line in actual experiments. Resistances on the ship under an h/d of 3.0 was calculated to be 19.9 tons with a lateral current force coefficient of 1.3. Therefore, the lateral current force coefficient was expected to be 1.3 under an h/d of 3.0, in experiments measured value 20.0 tons. And the discharging currents did not affect the towing force if the towing line was over 30 m, since the towing resistance showed a similar tendency for changes in line length from 30 m to 60 m.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.889-901
• /
• 2021

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.

• Proceedings of the KIEE Conference
• /
• 2003.10b
• /
• pp.137-140
• /
• 2003

To the optimization design of molded case circuit breakers(MCCBs), it is necessary and important to calculate the electro-dynamic repulsion force acting on the movable conductor. With 3-D finite element nonlinear analysis, according to the equations among current-magnetic field-repulsion force and taking into account the ferromagnet, contact bridge model is introduced to simulate the current constriction between contacts, so Lorentz and Holm force acting on the movable conductor and contact, respectively, can be integrated to calculate. Coupled with circuit equations, the opening time of movable contact also can be obtained using iteration with the restriction of contact force. Simulation and experiment for repulsion forte and opening time of five different configuration models have been investigated. The results indicate that the proposed method is effective and capable of evaluating new design of contact systems in MCCBs.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.04a
• /
• pp.66-72
• /
• 2000

Commercial eddy current dynamometers control the torque of ratating body (poer supply machine) with the field coil current being operated as a braking force. In this paper, we studied about the relation between the field coil current and the torque load of eddy current dynamometer. By the torque measuring analysis of eddy current dynamometer, it is linear relation between the brake force measured from the torque meter (e.g. load cell, strain gage or spring balance etc.) which is installed at the case of dynamometer and the multiply of shaft rpm by the square of field coil current (N$\times$Ia2). To prove the relation, it was experimented and showed that the torque operated by the rotating body can be measured with the shaft rpm and the field coil current of eddy current dynamometer. This result shows a possibility that eddy current dynamometer can measures the torque of rotating body without special torque measuring devices.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.11
• /
• pp.1145-1153
• /
• 2011

EMB (Electro-Mechanical Brake) systems can provide improved braking and stability functions such as ABS, EBD, TCS, ESC, BA, ACC, etc. For the implementation of the EMB systems, reliable and robust fault detection algorithm is required. In this study, a model-based fault detection algorithm is designed based on the analytical redundancy method in order to monitor current and force sensor faults in EMB systems. A state-space model for the EMB is derived including faulty signals. The fault diagnosis algorithm is constructed using the analytical redundancy method. Observer is designed for the EMB and the fault detectability condition is examined based on the residual analysis. The performance of the proposed model-based fault detection algorithm is verified in simulations. The effectiveness of the proposed algorithm is demonstrated in various faulty cases.

• Transactions of Materials Processing
• /
• v.19 no.1
• /
• pp.38-43
• /
• 2010

Electromagnetic forming (EMF) method is one of high-velocity forming processes, which uses electromagnetic Lorentz force. Advantages of this forming technique are summarized as improvement of formability, reduction in wrinkling, non-contact forming and applications of various forming process. In this study, the EMF apparatus is developed. It is designed to be stored in 10 capacitors connected in parallel, each with a capacitance of $50{\mu}F$ and maximum working voltage of 5kV. The system has capacitance of $500{\mu}F$ and maximum stored energy of 6.25kJ. And EMF experiments are carried out to verify the feasibility of the EMF apparatus, which has enough forming force from the results of EMF experiment. In addition, peak current carrying a forming coil is predicted from theoretical background, and verified the predicted value compared with experimental value using the current measurement equipment. Consequently, EMF apparatus developed in this study can be applied to various EMF researches for commercialization.

• Proceedings of the KSR Conference
• /
• 2001.10a
• /
• pp.147-155
• /
• 2001

A data acquisition and signal processing system for evaluating the current collection system is developed, and subsequently applied to the measurement and analysis of the contact force in the current collection system of the proposed Korean High Speed Railway. The measurement of the contact force is based on an algorithm that employs the relationship between the contact force, the strain due to the bending moment and the panhead inertia. For the contact forces in the frequency range of less that 50Hz, the panhead can the modeled as a rigid body in the inertia calculation. For higher frequencies however, the bending vibration modes of the panhead need to be accounted for as well.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.690-694
• /
• 1996

In order to regulate the cutting force at a desired level during peripheral end milling processes, a feedrate override Adaptive Control Constant system was developed. This paper presents an explicit pole-assignment PI-control law through spindle motor current monitoring and its application to cutting force regulation for feedrate optimization. An experimental set-up is constructed for the commercial CNC machining center without any major changes of the structure. A data transfer system is constructed with standard interface between an IBM compatible PC and a CNC of the machining center. Experimental results show the validity of the system.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.91-93
• /
• 1998

This paper describes the braking performance of the eddy current brake for high speed trains according to the number of poles. The eddy current brake systems have to be equipped with the maximum braking force and deceleration in the given volume or mass, high braking force rate, as small normal forces as possible and stable construction. The parameters, such as the number of poles, electric ampere turns, slot width have influence on the braking force characteristics. In this paper, the effect of braking performance from the variation of the number poles is calculated by using FEM, the number of the pole which makes the maximum braking force is proposed.