• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.292-295
• /
• 2001

This paper describes the implementation of UPS system controlled by the DSP. The digital techniques have been used tn overcome the problems of UPS system controlled by analog control circuits. By developing these systems using the digital technique we could increase the reliability and improve the electrical characteristics. And we designed and developed the system which is able to control UPSs and to monitor errors, statuses and actual values transmitted from UPS through internet. The UPSs also impose high demands on battery life time, reliability and energy-efficiency. These requirements can only be met by employing sophisticated battery management system(BMS). Therefore, a highly accurate, universal and inexpensive measuring system for BMS was developed.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.11
• /
• pp.1006-1011
• /
• 2004

Carbon nanotubes have outstanding properties which make them useful for a number of high-technology applications. Especially, single-walled carbon nanotube (SWNT), working under physical conditions (in aqueous solution) and converting electrical energy into mechanical energy directly, can be a good substitute for artificial muscle. The carbon nanotube structure simulated in this paper is an isotropic cantilever type with an adhesive tape which is sandwiched between two SWNTs. For predicting the geometrical and physical parameters such as deflection, slope, bending moment and induced force with various applied voltages, the analytical model for a 3 layer bimorph nanotube actuator is developed by applying Euler-Bernoulli beam theory. The governing equation and boundary conditions are derived from energy Principles. Also, the brief history of carbon nonotube is overviewed and its properties are compared with other functional materials. Moreover, an electro-mechanical coupling coefficient of the carbon nanotube actuator is discussed to identify the electro-mechanical energy efficiency.

• Coupled systems mechanics
• /
• v.6 no.3
• /
• pp.351-367
• /
• 2017

In this article, the multiphysics response of magneto-electro-elastic (MEE) cantilever beam subjected to thermo-mechanical loading is analysed. The equilibrium equations of the system are obtained with the aid of the principle of total potential energy. The constitutive equations of a MEE material accounting the thermal fields are used for analysis. The corresponding finite element (FE) formulation is derived and model of the beam is generated using an eight noded 3D brick element. The 3D FE formulation developed enables the representation of governing equations in all three axes, achieving accurate results. Also, geometric, constitutive and loading assumptions required to dimensionality reduction can be avoided. Numerical evaluation is performed on the basis of the derived formulation and the influence of various mechanical loading profiles and volume fractions on the direct quantities and stresses is evaluated. In addition, an attempt has been made to compare the individual effect of thermal and mechanical loading with the combined effect. It is believed that the numerical results obtained helps in accurate design and development of sensors and actuators.

• Progress in Superconductivity
• /
• v.13 no.1
• /
• pp.52-57
• /
• 2011

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. The 35 kWh class SFES is composed of a main frame, superconductor bearings, electro-magnetic dampers, a motor/generator, and a composite flywheel. The energy storing capacity of the SFES can be limited by the operational speed range of the system. The operational speed range is limited by many factors, especially the resonant frequency of the main frame and flywheel. In this study, a steel frame has been designed and constructed for a 35 kWh class SFES. All the main parts, their housings, and the flywheel are aligned and assembled on to the main frame. While in operation, the flywheel excites the main frame, as well as all the parts assembled to it, causing the system to vibrate at the rotating speed. If the main frame is excited at its resonant frequency, the system will resonate, which may lead to unstable levitation at the superconductor bearings and electro-magnetic dampers. The main frame for the 35 kWh class SFES has been designed and constructed to improve stiffness for the stable operation of the system within the operational speed range.

• Progress in Superconductivity
• /
• v.14 no.1
• /
• pp.60-65
• /
• 2012

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 35 kWh class SFES module was designed and constructed as part of a 100kWh/1MW class SFES composed of three 35 kWh class SFES modules. The 35 kWh class SFES is composed of a main frame, superconductor bearings, a composite flywheel, a motor/generator, electro-magnetic bearings, and a permanent magnet bearing. The high energy density composite flywheel is levitated by the permanent magnet bearing and superconductor bearings, while being spun by the motor/generator, and the electro-magnetic bearings are activated while passing through the critical speeds. Each of the main components was designed to provide maximum performance within a space-limited compact frame. The 35 kWh class SFES is designed to store 35 kWh, with a 350 kW charge/discharge capacity, in the 8,000 ~ 12,000 rpm operational speed range.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.217-220
• /
• 2001

In the shearing process the burr or rollover must be minimized in order to improve the quality of product. The burr size can be minimized by control of several process parameters. But removal of all burrs are impossible. Most mechanical type deburring methods (vibrating bowls, rotating barrels, shot blasting, for example.) will remove large burrs, other methods use chemical (electro-chemical deburring) or heat (thermal energy deburring). The electro-chemical deburring process removes burrs by the deplating method. Electro-chemical deburring equipment is requires a small capital investment than other methods(mechanical or thermal methods). Electro-chemical deburring method need to many parameters for control such as a time, voltage and concentration of electrolyte. In this paper shows relations of these parameters by experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.132-135
• /
• 2002

In the present study, an electro-mechanical KAFO (knee-ankle-foot orthosis) which satisfies both the stability in stance and the knee flexion in swing was developed and evacuated in eight polio patients. A knee joint control algorithm suitable for polio patients who are lack of the stability in pre-swing was also developed and various control systems and circuits were also designed. In addition, knee flexion angles and knee moments were measured and analyzed for polio patients who used the developed KAFO with the three-dimensional motion analysis system. Energy consumption was also evaluated for the developed KAFO by measuring the movement of the COG (center of gravity) during gait. From the present study, the designed foot switch system successfully determined the gait cycle of polio patients and controlled knee joint of the KAFO, resulting in the passive knee flexion or foot clearance during swing phase. From the three-dimensional gait analysis for polio patients, it was found that the controlled-knee gait with the developed electro-mechanical KAFO showed the knee flexion of 40$^{\circ}$∼45$^{\circ}$ at an appropriate time during swing. Vertical movements of COG in controlled-knee gait (gait with the developed electro-mechanical KAFO) were significantly smaller than those in looked knee gait(gait with the locked knee Joint). and correspondingly controlled-knee gait reduced approximately 40% less energy consumption during horizontal walking gait. More efficient gait patterns could be obtained when various rehabilitation training and therapeutic programs as well as the developed electro-mechanical KAFO were applied for polio patients.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.6
• /
• pp.76-81
• /
• 2011

Fossil fuel, the energy source of internal combustion engine automobiles, is limited in resource and has caused environmental issues for decades. Accordingly, automobile manufacturers from many countries around the world are developing or producing eco-friendly vehicles that utilize alternative sources of energy. These vehicles are equipped with many electronic and electrical components which operate on high voltage and/or large current that were not used in conventional combustion engine automobiles. In this paper, in order to analyze the electro-magnetic interference noise, electric vehicles and fuel cell electric vehicles are tested under the guidelines of KMVSS (Korean Motor Vehicle Safety Standards) as well as under test modes that are not stipulated under the guidelines.

• Structural Engineering and Mechanics
• /
• v.76 no.1
• /
• pp.141-151
• /
• 2020

This manuscript tends to investigate influences of nanoscale and surface energy on a static bending and free vibration of piezoelectric perforated nanobeam structural element, for the first time. Nonlocal differential elasticity theory of Eringen is manipulated to depict the long-range atoms interactions, by imposing length scale parameter. Surface energy dominated in nanoscale structure, is included in the proposed model by using Gurtin-Murdoch model. The coupling effect between nonlocal elasticity and surface energy is included in the proposed model. Constitutive and governing equations of nonlocal-surface perforated Euler-Bernoulli nanobeam are derived by Hamilton's principle. The distribution of electric potential for the piezoelectric nanobeam model is assumed to vary as a combination of a cosine and linear variation, which satisfies the Maxwell's equation. The proposed model is solved numerically by using the finite-element method (FEM). The present model is validated by comparing the obtained results with previously published works. The detailed parametric study is presented to examine effects of the number of holes, perforation size, nonlocal parameter, surface energy, boundary conditions, and external electric voltage on the electro-mechanical behaviors of piezoelectric perforated nanobeams. It is found that the effect of surface stresses becomes more significant as the thickness decreases in the range of nanometers. The effect of number of holes becomes significant in the region 0.2 ≤ α ≤ 0.8. The current model can be used in design of perforated nano-electro-mechanical systems (PNEMS).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.5
• /
• pp.499-505
• /
• 2015

To properly design and assess a piezoelectric vibration energy harvester, it is necessary to consider the application of an efficiency measure of energy conversion. The energy conversion efficiency is defined in this work as the ratio of the electrical output power to the mechanical input power for a piezoelectric vibration energy harvester with an impedance-matched load resistor. While previous research works employed the electrical output power for approximate impedance-matched load resistance, this work derives an efficiency measure considering optimally matched resistance. The modified efficiency measure is validated by comparing it with finite element analysis results for piezoelectric vibration energy harvesters with three different values of the electro-mechanical coupling coefficient. New findings on the characteristics of energy conversion and conversion efficiency are also provided for the two different impedance matching methods.