Jong-Boo Han

Coupled vibration analysis of Maglev vehicle-guideway while standing still or moving at low speeds

Dynamic instability, that is, resonance, may occur on an electromagnetic suspension-type Maglev that runs over the elevated guideway, particularly at very low speeds, due to the flexibility of the guideway. An analysis of the dynamic interaction between the vehicle and guideway is required at the design stage to investigate such instability, setting slender guideway in design direction for reducing construction costs. In addition, it is essential to design an effective control algorithm to solve the problem of instability. In this article, a more detailed model for the dynamic interaction of vehicle/guideway is proposed. The proposed model incorporates a 3D full vehicle model based on virtual prototyping, flexible guideway by a modal superposition method and levitation electromagnets including feedback controller into an integrated model. By applying the proposed model to an urban Maglev vehicle newly developed for commercial application, an analysis of the instability phenomenon and an investigation of air gap control performance are carried out through a simulation.

Study on Running Safety of EMS-Type Maglev Vehicle Traveling over a Switching System

The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder , the articulation angle, the length between two centers of a fixed girder at its ends , and the number of girders. On the basis of the effects of the considered design variables , we establish an optimized design of a switch with improved safety. † Corresponding Author, lee_jm@kimm.re.kr,ready2go@cnu.ac.kr C 2014 The Korean Society of Mechanical Engineers 한종부 · 이종민 · 한형석 · 김성수 · 양석조 · 김기정 1310 레일과 접촉 없이 안전하게 노선을 변경할 수 있 는 기능을 제공해야 한다. 특히, U-형 전자석을 이 용하여 부상력과 안내력을 동시에 생성 하는 도시 형 상전도 흡인식 자기부상열차에 있어서는 분기 기 주행 시 안전성에 대한 검토가 필요하다. 이 방식에서는 안내력을 능동적으로 제어하지 않기 때문에 작은 곡률 반경을 갖는 분기기 통과시 전 자석의 횡공극이 과도하게 발생하여 가이드레일과 기계적 접촉을 일으킬 수 있기 때문이다. 관절형 분기기의 경우 Fig. 1 과 같이 곡선선형을 생성할 때 3∼4 개의 직선거더가 인접한 상대거더와 일정 한 각도를 이루어 굴절되며 선형을 생성한다. 그 렇기 때문에 거더 길이, 굴절각의 각도, 각도완화 조절장치구간의 길이에 따라서 전자석의 횡공극이 영향을 받는다. 그러므로 이러한 설계변수에 대한 주행안전성의 영향을 분석하여 경제적이면서도 안 전한 주행이 가능하도록 설계에 반영할 필요가 있 다. 분기기 통과시 차량의 주행안전성 해석에 대 한 연구는 국내외적으로 아직 사례가 발견되지 않 는다. 본 논문에서는 Fig. 2 와 같이 개발 중인 관절식 분기기의 주행안전성 향상을 위하여 주 설계 변수 의 주행안전성에의 영향을 분석하는데 목적이 있 다. 기존 연구와 달리 전체차량 다물체 동역학 해 석모델의 적용이 제안된다. Fig. 1 3 way segmented switch aligned at turn out Fig. 2 Segmented switch under construction 특히, 전체차량 해석 모델은 3 차원 해석 모델로 개발되어 상세한 동 특성 시뮬레이션이 가능한 장 점을 갖는다. 제안된 모델을 이용하여 분기기 통 과시의 주행안전성 척도 중의 하나의 횡공극 시뮬 레이션이 이루어진다. 거더 길이, 굴절각의 각도, 각도완화조절장치구간의 길이의 영향 분석이 이루 어진다. 이러한 매개변수연구 결과를 바탕으로 분 기기 통과시 차량의 안전성 향상을 위한 분기기 설계 방향이 제시된다.

Design and Validation of a Slender Guideway for Maglev Vehicle by Simulation and Experiment

ABSTRACT Normally, Maglev (magnetic levitation) vehicles run on elevated guideways. The elevated guideway must satisfy various load conditions of the vehicle, and has to be designed to ensure ride quality, while ensuring that the levitation stability of the vehicle is not affected by the deflection of the guideway. However, because the elevated guideways of Maglev vehicles in South Korea and other countries fabricated so far have been based on over-conservative design criteria, the size of the structures has increased. Further, from the cost perspective, they are unfavourable when compared with other light rail transits such as monorail, rubber wheel, and steel wheel automatic guided transit. Therefore, a slender guideway that does have an adverse effect on the levitation stability of the vehicle is required through optimisation of design criteria. In this study, to predict the effect of various design parameters of the guideway on the dynamic behaviour of the vehicle, simulations were carried out using a dynamics model similar to the actual vehicle and guideway, and a limiting value of deflection ratio of the slender guideway to ensure levitation control is proposed. A guideway that meets the requirement as per the proposed limit for deflection ratio was designed and fabricated, and through a driving test of the vehicle, the validity of the slender guideway was verified. From the results, it was confirmed that although some increase in airgap and cabin acceleration was observed with the proposed slender guideway when compared with the conventional guideway, there was no notable adverse effect on the levitation stability and ride quality of the vehicle. Therefore, it can be inferred that the results of this study will become the basis for establishing design criteria for slender guideways of Maglev vehicles in future.

Study on the Levitation Stability of Maglev Vehicle considering the Vibration of Steel Switch Track

Generally, in the train area, switch tracks have required high reliability because this system is directly associated with derailment. Especially, switch tracks of Maglev vehicles must be moved in terms of the whole geometric characteristics, in which the bogies are encased in the switch track. For this reason, switch track was constructed with steel lighter than concrete girders. But, the steel switch track was weak because of structural vibration as well as structural deformation. Therefore, it is important to predict the levitation stability when a vehicle passes over flexible switch track. The aims of this paper are to develop a coupled dynamic model to describe the relationship between a Maglev vehicle and switch track and to predict the levitation stability. In order to develop the coupled dynamic model, a three dimensional vehicle model was developed based on multibody dynamics; a switch model was made using the modal superposition method. And, the developed model was verified using comparison measured data.

Lateral Vibration Reduction of a Maglev Train Using U-shaped Electromagnets

For an electromagnetic suspension (EMS)-type urban Maglev train using U-shaped electromagnets, both the vertical and the lateral air gaps for levitation are maintained only by the electromagnet. The train can run over curved rails without active lateral air gap control because the U-shaped electromagnet simultaneously produces both a levitation force and a guidance force, which is dependent on the levitation force. Owing to the passive control of the lateral air gap, the lateral vibration could exceed the limits of the lateral air gap and acceleration. In this study, dynamic analysis of a Maglev train is carried out, and the effectiveness of a lateral damper for vibration reduction is investigated. To more accurately predict the lateral vibration, a Maglev vehicle multibody model including air-sparing, guideway irregularities, electromagnets, and their controls is developed.

Dynamic analysis of Maglev conveyor using an EM-PM hybrid suspension

Modeling and simulation based on virtual prototyping has been widely used in industry to decrease the cost of development. However, the application of virtual prototyping to Maglev conveyors has not been done, because the modeling and simulation technology of the Maglev conveyor based on virtual prototyping is not well established. Therefore, a dynamic model of the Maglev conveyor for carrying LCD glass cassette was developed to predict and improve levitation stability. The mechanical components, joints, and force elements are represented by multibody dynamic modeling techniques. The electromagnets and their control systems are also included in the mechanical model. With the coupled model, the dynamic responses are predicted and analyzed. In addition, the effects of the levitation control algorithm on stability are also simulated.

Characteristics of vibration in magnetically levitated trains subjected to crosswind

An electromagnetic suspension system-type (EMS-type) magnetically levitated vehicle (Maglev) maintains the airgap between the guiderail and the electromagnet by controlling the electric current through the levitation controller and runs with the help of a linear induction motor. ECOBEE, an EMS-type Maglev, is designed for the purpose of urban transit and must run on a curved guideway with a small radius of curvature. However, while the EMS-type Maglev controls the vertical airgap using the levitation force of the electromagnet, in the case of the lateral direction, a guidance force, which is determined by the levitation force through the intensity of lateral displacement, passively controls the lateral displacement. However, when an excessive lateral displacement is triggered by a disturbance that is greater than the guidance force, an antiaberration skid comes into contact with the rail. Therefore, the Maglev running on a curve with a small radius should maintain the airgap without touching the rail when turning directions on a curved rail, while the vibrations of the vehicle caused by external factors, such as entering the circular curve from the transition curve, or a crosswind, can affect the levitation stability. Therefore, in order to secure the levitation stability of the electromagnet while also improving the curving performance of the vehicle, inserting a lateral damper between the cabin and the bogie has been suggested. In the present study, by using an integrated model of the Maglev system developed by multibody dynamics, the influence of a crosswind as the train runs along a curve and the effect of the lateral damper were analyzed.

Study on the Remote Controllability of Vision Based Unmanned Vehicle Using Virtual Unmanned Vehicle Driving Simulator

In this paper, we proposed an image shaking index to evaluate the remote controllability of vision based unmanned vehicles. To analyze the usefulness of the proposed image-shaking index, we perform subjective tests using a virtual unmanned vehicle driving simulator. The developed driving simulator consists of a real-time multibody dynamic software of the unmanned vehicle, a motion simulator, and a driver console. We perform dynamic simulations to obtain the motion of the unmanned vehicle running on the various road surfaces such as ISO roughness level A~E roads. The motion of the vehicle body is reflected in the motion simulator. Then, to enable remote control operation, we offer to operators the image data that was measured using the camera sensor on the simulator. We verify the usefulness of the proposed image-shaking index compared with subjective index provided by operators. † Corresponding Author, sookim@cnu.ac.kr C 2016 The Korean Society of Mechanical Engineers

Levitation Control Simulation of a Maglev Vehicle Considering Guideway Flexibility

In magnetic levitation vehicles, the clearance between the magnet and track should be maintained within an allowable range through a feedback control loop. The flexibility of the guideway would introduce additional modes in the overall suspension system, resulting in dynamic interaction between the guideway vibration and the electromagnetic suspension control system. This dynamic interaction can be a serious problem, particularly at very low speeds or standstill, and may cause airgap instability. To optimize the overall system dynamics, an integrated dynamic model including mechanical and electrical parts and a flexible guideway as well as a control loop was developed. With the proposed model, airgap simulations at standstill were performed while varying the control gains, specifically with the aim of understanding the effects of gains of the PID controller on the airgap variation. The findings may be used to achieve a stable levitation controller design.

Effect of Highly Pressurized Hydrogen Gas on Tensile Properties of a Low-Alloy Steel Used for Manufacturing CNG Storage Vessels

SNG (synthetic natural gas or substitute natural gas) could contribute greatly toward energy security. In addition, HCNG (or H2CNG) is expected to be used as a fuel gas for internal combustion engines and home appliances because it has extremely low emissions and high thermal efficiency. However, the hydrogen contained in SNG or HCNG can deteriorate the mechanical properties of the materials used in existing natural gas infrastructure. Therefore, it is necessary to investigate the effect of hydrogen on the mechanical properties of such materials so that SNG or HCNG can be transported and distributed safely and reliably. In this study, the effect of highly pressurized hydrogen gas on the tensile properties of a low-alloy steel used for manufacturing CNG storage vessels was investigated using the so-called hollow tensile specimen technique.