• Journal of Institute of Control, Robotics and Systems
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• v.7 no.3
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• pp.209-217
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• 2001

In this paper, we propose a linear quadratic regulator(LQR) controller design for the active suspension using evolution strategy(ES) and neural network. We can improve the inherent suspension problem, the trade-off between ride quality and suspension travel by selecting appropriate weight in the LQR-objective function. Since any definite rules for selecting weights do not exist, we replace the designers trial-and-error method with ES that is an optimization algorithm. Using the ES, we can find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle. The relationship between the frequencies and proper control gains are generalized by use of the neural networks. When the vehicle is driven, the trained neural network is activated and provides the proper gains for operating frequencies. And we adopted double sky-hook control to protect car component when passing large bump. Effectiveness of our design has been shown compared to the conventional sky-hook controller through simulation studies.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.500-506
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• 2005

The development of tilting train has been required for speed-up on the conventional electric railroad due to the characteristic of Korean railroad with a lot of curve track. The study and development of a tilting system and a tilting bogie which have a different mechanism with high speed train will play a important role for enhancement of technology for Korean railway. The study for tilting pantograph mechanism to decrease the displacement between a catenary and a center of pantograph happened when the carbody is tilted in order to maintain the ride comfort and stability m a curving track is proceeding with the development of tilting train. In this paper, we introduce the design concept for the tilting mechanism of pantograph and the role and characteristics for several devices adopted in the tilting mechanism of pantograph. Through the kinematic analysis of tilting mechanism, we will obtain and calculate the optimal tilting angular velocity and acceleration in order to keep the contact behavior of a pantograph and a catenary according to tilting of a carbody.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.8-16
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• 2012

Fixed speed wind turbine generators system that uses induction generator as a wind generator has the stability problem similar to a synchronous generator. On the other hand, doubly fed induction generator (DFIG) has the flexibility to control its real and reactive powers independently while being operated in variable speed mode. This paper focuses on a scheme where IG is stabilized by using DFIG during grid fault. In that case, DFIG will be heavily stressed and a remedy should be found out to protect the frequency converter as well as to allow the independent control of real and reactive powers without loosing the synchronism. For that purpose, a crowbar protection switch or DC-link protecting device can be considered. This paper presents a comparative study between two protective schemes, a crowbar circuit connected across the rotor of the DFIG and a protective device connected in the DC-link circuit of the frequency converter. Simulation analysis by using PSCAD/EMTDC shows that both schemes could effectively protect the DFIG, but the latter scheme is superior to the former, because of less circuitry involved.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.715-723
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• 2018

The energy storage system consists of batteries, power conditioning system and energy management system. If ESS is installed and operated in the field, SAT(Site Acceptance Test) of ESS is being essentially required for the safety and performance of ESS. Furthermore, in order to more accurately and reliably validate the performance of the ESS in advanced countries, it has been required to perform not only performance testing by H/W equipments but also performance verification by S/W tool. Therefore, this paper proposes the modeling of portable test equipment in order to evaluate the performance and reliability of ESS by using the PSCAD/EMTDC S/W. And also, the prototype of 30[kW] scaled portable test equipments is implemented based on the S/W modeling. From the results of various simulations and testings such as power quality, LVRT and anti-islanding tests, it is confirmed that 30[kW] scaled portable test equipment is useful for SAT of ESS, because the simulation results of PSCAD/EMTDC are identical to them of 30[kW] test equipment at the same test conditions.

• Journal of Power Electronics
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• v.13 no.6
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• pp.1032-1041
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• 2013

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power systems under unbalanced grid conditions. Three different control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions and torque pulsation. The control algorithm having a zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by the control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive powers. A combination of these two control algorithms depending on the operating requirements and the depth of the grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions leading to high performance DFIG wind turbine systems.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1304-1312
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• 2005

The ride and noise characteristics of a vehicle are significantly affected by the vibration transferred to the body through the chassis mounting points in the engine and suspension. It is known that body attachment stiffness is an important factor of idle noise and road noise for NVH performance improvement. The body attachment stiffness serves as a route design aimed at isolating the vibration generated inside the car due to the exciting force of the engine or road. The test result of the body attachment stiffness is shown in the FRF curve data; the stiffness level and sensitive frequency band are recorded by the data distribution. The stiffness data is used for analyzing the parts that fail to meet the target stiffness at a pertinent frequency band. The analysis shows that the target frequency band is between 200 and 500 Hz. As a result of the comparison in a mounted suspension, the analysis data is comparable to the test data. From these results, there is a general agreement between the predicted and measured responses. This procedure makes it possible to find the weak points before a proto car is produced, and to suggest proper design guidelines in order to improve the stiffness of the body structure.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.711-719
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• 2019

At present, wind power is the fastest growing technology in the world. The domestic market depends heavily on imports for wind tower lift. so it manage through the overseas maker. The lift manufacture, establishment and maintenance utility is increasing, localization development of one wind tower lift is necessary with domestic fundamental base technique. In this paper, we will study the components necessary for the development of onshore offshore wind tower elevators, which are currently dependent on total imports, in line with the high growth of the wind market and the enlargement of the wind power generators. First of all, endless winders and cabins, which are the core components of the offshore wind tower lift, were examined for the components that affect the structural safety. Structural analysis was performed on Sheave, which is responsible for most of the lift lifting loads, and Block Stop, a safety device that prevents the cabin from falling in an emergency. The structural suitability was evaluated by comparing with the safety factor. In addition, the on-board control panel combines the control panel of the elevator and the drive motor driving the endless winder for efficient control of the offshore wind tower lift. The addition of features improves ride comfort at departure.

• Journal of English Language & Literature
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• v.64 no.4
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• pp.651-672
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• 2018

Death of a Salesman is centered on Willy Loman trying to achieve the American dream and taking his family along for the ride. This paper explores the meaning of his suicide in the work through the Adorno's theory on the individual's reification and commodity by an exchange value in the capitalism and argues that Bourdieu's capital classification shows the cause of his tragic decision. Reification refers to "the structural process whereby the commodity form permeates life in capitalist society." and Adorno called the reification of consciousness an epiphenomenon. The social-psychological level in Adorno's diagnosis serves to demonstrate the effectiveness and pervasiveness of late capitalist exploitation. According to Bourdieu, cultural capital can exist three forms: in the embodied state, in the objectifed state and in the instituionalized state. He states embodied capital is argued to be the most significant influence; however unlike other forms of capital (social, economic, etc.) obtaining embodied capital is largely out of the individuals' control as it is developed from birth. In conclusion, I suggest Death of a Salesman can be interpreted as a text criticizing the internalization of the subject, which is the result of the self-destructive mechanism of the subject in the logic of modern subject formation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.38-45
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• 2020

A magnetically levitating capsule train, which runs inside the sub-vacuum tube, can reach ultra-fast speeds by dramatically reducing the aerodynamic drag and friction. The capsule train uses the superconductor electrodynamic suspension (SC-EDS) method for levitation. The SC-EDS method has advantages, such as a large levitation gap and free of gap control, which could reduce the infra-construction cost. On the other hand, disadvantages, such as the large variation of the levitation-guidance gap and small damping characteristics in levitation-guidance force, could degrade the running stability and ride comfort of the capsule train. In this study, a dynamic analytical model of a capsule train based on the SC-EDS was developed to analyze the running dynamic characteristics. First, as important factors in the capsule train dynamics, the levitation and guidance stiffness in the SC-EDS system were derived, which depend non-linearly on the velocity and gap variation. A 3D dynamic analysis model for capsule trains was developed based on the derived stiffness. Through the developed model, the effects of the different running speeds on the ride comfort were analyzed. The effects of a disturbance from infrastructure, such as the curve radius, tube sag, and connection joint difference, on the running stability of the capsule train, were also analyzed.

• Journal of Korea Multimedia Society
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• v.23 no.8
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• pp.1099-1107
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• 2020

The need for customized services providing real-time subway information through mobile devices for the blind using subway as their primary transportation method is becoming more essential. Therefore, this study is aimed at developing a mobile service to provide real-time subway information by displaying with braille and utilizing Dot Watch. The process of real-time subway information guidance mobile service is as follows: the route confirmation stage, the ride waiting & judgment stage, the on-the-go stage, and lastly, the off-road phase & wrong path state. The service provides real-time appropriate information to the visually impaired people for each situation. It receives subway information through API provided by Seoul Metropolitan Government and ODSay API. The service is developed and coded with in Java using Android Studio, and the communicating method with Dot Watch was done using Bluetooth. The usability evaluation was conducted in terms of efficiency, effectiveness, and satisfaction. The evaluation methods mentioned above were carried out by testees, and feedback was given. They assessed that the information provided was useful but still unstable to use the system. It is expected that actual usability will increase if our study is supplemented using voice output function.