• Proceedings of the KSR Conference
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• 2000.05a
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• pp.626-633
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• 2000

An air spring which is a part of the railroad vehicle suspension system is used to reduce and absorb the vibration and the noise. Main components of the air spying are a cord reinforced rubber bellows, a upper plate, a lower plate and a stopper rubber spring. The characteristics of the air spring which are the load capacity, the vertical and the horizontal stiffness are depended on the configuration of rubber bellows, the angle of cord and the mechanical properties of cord. The computer simulation using commercial finite element analysis codes are executed to predict and evaluate the load capacity and the stiffness. The appropriate shape and cord angle of the air suing are selected to adjust the required performance of the air spring. Several samples of the air spring are manufectured and experimented. It is shown that the results by computer simulation are in close agreement with the test results.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1838-1844
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• 2011

In this paper, the propulsion control of a high-speed maglev train is studied. Electromagnetic suspension is used to levitate the vehicle, and linear synchronous motors (LSM) are used for propulsion. In general, a low-speed maglev train uses a linear induction motor (LIM) for propulsion that is operated under 300[km/h] due to the power-collecting and end-effect problem of LIM. In case of the high-speed maglev train over 500[km/h], a linear synchronous motor (LSM) is more suitable than LIM because of a high-efficiency and high-output properties. An optical barcode positioning system is used to obtain the absolute position of the vehicle due to its wide working distance and ease of installation. However, because the vehicle is working completely contactless, the position measured on the vehicle has to be transmitted to the ground for propulsion control via wireless communication. For this purpose, Bluetooth is used and communication hardware is designed. A propulsion controller using a digital signal processor (DSP) in the ground receives the delayed position information, calculates the required currents, and controls the stator currents through inverters. The performance of the implemented propulsion control is analyzed with a small maglev train which was manufactured for experiments, and the applicability of the high-speed maglev train will be explored.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.307-317
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• 2012

The LRT(light rail transit) system, which has medium transport capacity between subway and bus is an advanced transportation system. It has many benefits like chap construction and operational cost down through driverless and flexible route planning. The rubber tired AGT(K-AGT) is a kind of LRT, which has rubber wheels and side guides. The side guides has many advantages, but brings vibration and noise problems from the friction between the guide rail and the wheels. This is the major source for the of passengers' discomfort. The purpose of this paper is to analyze dynamic characteries and running stability of the rubber tired AGT localization bogie if the AGT's speed is increased from 70 km/h to 80 km/h. The current design parameters of bogie suspension, as it is designed, was examined to satisfy the comfort index of the railway vehicle in performance test.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.427-434
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• 2011

This paper is focused on application of recursive least squares method to estimate rail irregularities from the acceleration measurement on an axle-box or a bogie for the rail condition monitoring with in-service high-speed trains. Generally, the rail condition was monitored by a special railway inspection vehicle but the monitoring method needs an expensive measurement system. A monitoring method using accelerometers on an axle-box or a bogie was already proposed in the previous study, and the displacement was successfully estimated from the acceleration data by using Kalman and frequency selective band-pass filters. However, it was found that the displacement included not only the rail irregularities but also phase delay of the applied filters, and effect of suspension of the bogie and conicity of the wheel. To identify the rail irregularities from the estimated displacement, a compensation filter method is proposed. The compensation filters are derived by using recursive least squares method with the estimated displacement as input and the measured rail irregularity as output. The estimated rail irregularities are compared with the true rail irregularity data from the rail inspection system. From the comparison, the proposed method is a useful tool for the measurement of lateral and vertical rail irregularity.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.303-310
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• 2011

This paper is focused on development of models for measuring lateral and vertical track irregularities from corresponding accelerometers of an in-service high-speed train. Generally, the track irregularity was measured by a special railway inspection vehicle or system with contact or non-contact sensors. However, the sensors are very expensive and vulnerable to a harsh environment. Displacement estimation from an inertial measurement unit and its wave-band filtering was already developed in the previous study, and it was found that their results included not only the track irregularities but also other information such as phase delay of the applied filters, and suspension and conicity of the wheel. To identify the track irregularities from those results, a compensation filtering method was proposed. Each directional compensation filter was derived by using a system identification method with the estimated directional displacement as input and the corresponding track irregularities as output. In this paper, they are integrated into a model for each direction and applied to the measured lateral and vertical acceleration data from the axle-box and bogie of an in-service high-speed train. Their results are compared with the data from the track geometry measurement system. From the comparison, the proposed models are a useful tool for the measurement of the track irregularities using accelerometers of in-service high-speed trains.

• Proceedings of the KSR Conference
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• 2003.10a
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• pp.125-130
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• 2003

Korean High Speed Train (KHST) designed to operate at 350km/h has been tested on high speed line in JungBu site since it was developed in 2002. The dynamic performances of railway vehicle are generally stability, safety and ride comfort. The stability performance of KHST was proved that it is stable at 400Km/h through Roller Rig test. The safety and ride comfort need to be predicted the capability of it at 350km/h by the on-line test because KHST is testing at 300km/h up to now. Therefor, in this paper, the safety and ride comfort at 350km/h are predicted the performance using the acceleration results at 300kw/h and these results show that the KHST's dynamic performances are very good. Also, it illustrate the two cases occurred the abnormal vibration of KHST during some on-line tests. The first case is that the variation of vertical acceleration of wheel is analyzed when an abrasion occur on wheel. The second case is that the lateral acceleration of wheel, bogie and body are analyzed when the KHST is unstable at high speed. The occurrences of these special phenomena were due to the some faults of the suspension and braking systems and the faults were improved. In present, it is testing with safety.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.193-199
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• 2016

Since the variations of electromagnetic suspension forces of maglev trains have close relations with the acceleration of the levitated bodies, it is basic to control the levitation forces using the measured acceleration of vehicles. In this study, an airgap control algorithm based on acceleration feedback is applied to maglev trains and a dynamic analysis method is developed considering maglev train-guideway interaction. Using the developed method, dynamic behaviors of a maglev train-guideway interaction system are investigated. It is observed from the analysis that the current design guidelines can be satisfied when the proposed airgap control algorithm is employed. Using the contorl algorithm, the current guidelines can be improved and economical maglev railway guideway structures can be designed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.555-560
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• 2003

Korean High Speed Train(KHST) has been tested on the high speed test line in Osung site of Korea High Speed Rail Construction Authority (KHRC). since it was developed as G7 Project Plan In 2002. This paper introduces the dynamic test devices in KHST and shows the comparison between the results of test and theoretical computing results which derive from the new model for KHST dynamic behavior. Previous computer simulation model for KHST was developed to review wether the vehicle system was satisfied with the dynamic performance requirements during the design procedure. But It should be applied the results of the parts test for suspension elements in order to compare between the results of computation and real test. Using VAMPIRE Program made by AEA Technology in UK. the new model also was modified. This paper shows that the static wheel loads calculated from new model is similar to test results. For test on high speed line, we prepared the test devices for evaluating the dynamic performances. which was consisted of the accelerometers( based on Kisler Co.) and the data aquisition systems (based on National instrument Co.), and test program coded by LabView 6i program. These lest devices and programs are flexible to extension the channels for adding sensors and connect to the ethernet network. The acceleration of car bodies, bogie frames and axle boxes were compared between the results of computation and test at 150km/. This paper shows that the results of test were high in high frequency band range but similar frequency band range. It might be considered that these differences were caused by the test which did not performed at constant speed for comparison analysis. Also. It will be able to understand the differences and make better results through a lot of tests planed in future.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.944-949
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• 2017

Recently, the demand of maglev systems in the manufacturing industry for LCD and OLED display panels, which are required to be very clean and possess vacuum systems, has been increasing due to their characteristics such as being non-contact, noise free and eco-friendly. However, it is still a challenge to simultaneously control both the propulsion and levitation for their interactive effect difficult to be exactly measured. In this paper, we proposed a new tuning method for controlling the magnetic levitation force robustly against the levitation disturbance caused by a propulsion system, based on LQ servo optimal control. The disturbance torque of the LSM propulsion system is calculated through FEM analysis in such a way that the LQ servo controller is determined in order to minimize the effect of the disturbance. The robust performance of the proposed LQ servo control method for the in-track type magnetic levitation systems is demonstrated via simulations and experiments.

• Wind and Structures
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• v.20 no.2
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• pp.213-236
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• 2015

For high-speed railways (HSR) in wind prone regions, wind barriers are often installed on bridges to ensure the running safety of trains. This paper analyzes the effect of wind barriers on the running safety of a high-speed train to cross winds when it passes on a bridge. Two simply-supported (S-S) PC bridges in China, one with 32 m box beams and the other with 16 m trough beams, are selected to perform the dynamic analyses. The bridges are modeled by 3-D finite elements and each vehicle in a train by a multi-rigid-body system connected with suspension springs and dashpots. The wind excitations on the train vehicles and the bridges are numerically simulated, using the static tri-component coefficients obtained from a wind tunnel test, taking into account the effects of wind barriers, train speed and the spatial correlation with wind forces on the deck. The whole histories of a train passing over the two bridges under strong cross winds are simulated and compared, considering variations of wind velocities, train speeds and without or with wind barriers. The threshold curves of wind velocity for train running safety on the two bridges are compared, from which the windbreak effect of the wind barrier are evaluated, based on which a beam structure with better performance is recommended.