• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1920-1933
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• 2006

Piezoelectric materials produce an electric field by deformation, and deform when subjected to an electric field. The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices, including electric-mechanical actuators, sensors and structures. In this paper, a hollow sphere composed of a radially polarized spherically anisotropic piezoelectric material, e.g., PZT_5 or (Pb) (CoW) $TiO_3$ under internal or external uniform pressure and a constant potential difference between its inner and outer surfaces or combination of these loadings has been studied. Electrodes attached to the inner and outer surfaces of the sphere induce the potential difference. The governing equilibrium equations in radially polarized form are shown to reduce to a coupled system of second-order ordinary differential equations for the radial displacement and electric potential field. These differential equations are solved analytically for seven different sets of boundary conditions. The stress and the electric potential distributions in the sphere are discussed in detail for two piezoceramics, namely PZT _5 and (Pb) (CoW) $TiO_3$. It is shown that the hoop stresses in hollow sphere composed of these materials can be made virtually uniform across the thickness of the sphere by applying an appropriate set of boundary conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.674-684
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• 2011

More and more elderly and disabled people are using electric scooters instead of electric wheelchairs because of higher mobility. However, people with high levels of impairment or the elderly still have difficulties in driving the electric scooters safely. Semi-autonomous electric scooter system is one of the solutions for the safety: Either manual driving or autonomous driving can be used selectively. In this paper, we implement a semi-autonomous electric scooter system with functions of localization and path following. In order to recognize the pose of electric scooter in outdoor environments, we design an outdoor localization system based on the extended Kalman filter using DGPS (Differential Global Positioning System) and wheel encoders. We added an accelerometer to make the localization system adaptable to road condition. Also we propose a path following algorithm using two arcs with current pose of the electric scooter and a given path in the map. Simulation results are described to show that the proposed algorithms provide the ability to drive an electric scooter semi-autonomously. Finally, we conduct outdoor experiments to reveal the practicality of the proposed system.

• Communications of Mathematical Education
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• v.28 no.3
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• pp.339-352
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• 2014

In this paper we introduce mathematical modellings in teaching and learning differential equations which were adopted by 2009 revised curriculum. The textbook of 'Advanced Mathematics II' published in 2014 with one publisher includes the content of the second order differential equation y"+y=0 by the power series method. This paper discusses the issue of the power series and gives an alternative method to explain problems of differential equation. Also, we found that the textbook of 'Advanced Mathematics II' used the mechanical system not electrical system in solving differential equation problems. Thus this paper suggests a method using an electric circuit in teaching and learning the first order differential equation. Finally we suggest some terminologies in the teaching and learning of differential equations.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.573-575
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• 1997

In this paper, the electronic differential system for electric vehicle using neural network is proposed and its performance is evaluated. The input features of NN are obtained by processing the encoder and potentiometer during driving. The 3 layered NN with back propagation algorithm has been used. Evaluation experiments show that the proposed controller is effective in controlling of unknown nonlinear plants.

• International journal of advanced smart convergence
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• v.11 no.2
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• pp.219-225
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• 2022

Recently, the popularization of personal mobility(PM) has made it possible to see many electric scooters. The energy source of personal transportation used by the general public and the disabled can be seen as environmentally friendly as electricity. Personal transportation means are divided into small electric vehicles because they use electric energy, and they are being treated as new models by automobile manufacturers in each country and spurring development. On the other hand, personal transportation means may cause various types of traffic accidents as they travel between roads and a human walk. In order to prevent such accidents, it is judged that the enactment of laws on the establishment of specifications for electric scooters, which are personal transportation means, and the method of restricting road operation should be given priority. The electric scooter is basically different from the conventional vehicle. The steering shaft of the steering system applied to the electric scooter one to two is possible. 1 to 2 the front-wheel under the steering column is used. It is classified according to the number of wheel installed at the electric scooter is the vehicle body into 2 wheel - electric scooter, and 3 wheel - electric scooter and 4 wheel - electric scooter. In this study, we propose a steering shaft design model that can be applied to an electric scooter, one of personal transportation means. A design model for 1-shaft steering and 2-shafts steering that can be applied to electric scooters is proposed. In addition, we have produced the prototypes for the commercialization of the proposed models, and reviewed the pros and cons of the manufactured prototypes and models.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.751-755
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• 2011

Electric Parking Brake(EPB) is the system operated by electric control actuator. It differs from the mechanical parking brake system which is operated by lever and pedal in need of human power. The EPB system is composed of DC motor, helical and differential epicyclic gear, screw, cables, and sensor. This paper describes about the EPB system mathematically and constructs a modeling of the EPB system using MATLAB/SIMULINK. Especially, SimMechanics library in SIMULINK is used to make each parts of system a module. By made modeling of the friction torque between bolt and nut. Cable tension can be maintained after the motor operating stops.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1718-1720
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• 1997

This paper deals with n rise in electric potential of telecommunication line for electric power system by lightning surges. When $1.2/50{\mu}s$ and $8/20{\mu}s$ impulse voltage and current were applied on telecommunication cable, the voltage waveforms at the end terminal and equipment were measured. The telecommunication lines, which consist of 60 conductors and 3.5km in length, have some surge protectors such as preposition lightning arrester and TVSS. In each case, the rise in electric potential was measured for differential mode and common mode, respectively. Also, the rise in ground potential and the induced voltages were measured and analyzed. As a result, a significant rise in ground potential was observed for lightning surge. It can cause failure or malfunction of telecommunication systems.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.151-153
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• 1993

This paper proposes a novel motor drive system for the electric vehicle. In this paper, four-wheel-direct-drive type electric vehicle system is designed and the theoretical and experimental analysis of the system is investigated. The concept of steering not with steering the wheels but with the difference of the motor torque fives the flexibility of the vehicle design and, allows the omission of the differential gear, transmission gear, and drive axles. Thus the proposed system gives the space between wheels and improves the driver's steering performance.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.05a
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• pp.130-137
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• 1994

As a part of developing engineering simulator for CANDU 6 nuclear power plants, present paper gives the tentative simulation results of reactor and turbine power transients including reactor-follow-turbine operation. One point kinetics equations are used for neutron dynamics, iodine and xenon loads. To calculate time-dependent high and low pressure turbine powers and grid frequency deviation, simple first order differential equations are used. In addition, control logics (reactor regulating system, demand power routine, and unit power regulator) used in the plant's process computers have been referenced.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.274-277
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• 2006

This paper describes a lighting warning system (LWS) which consists of a corona needle electrode, a low noise differential amplifier, an A/D converter, an one-chip microprocessor, a LCD and alarm devices. The corona needle electrode is used to measure electric field intensity caused by thunderclouds on the ground level. To evaluate the sensitivity of the LWS, calibration experiment was carried out using a round-shape parallel plate electrode system. The theoretical and experimental results show that the LWS can measure electric field intensity over 2 [kV/m].