2014 년도 한국철도학회 춘계학술대회 논문집 KSR2014S190

Research on Position Detecting Method for High-Speed Train with Coreless

Linear Synchronous Motor

손연*†, 이창영*, 한영재*

Yan Sun*†, Chang Young Lee*, Young Jae Han*

Abstract One successful application of coreless LSM (Linear Synchronous Motor) is Japanese Maglev system at the Yamanashi Test Line. Position detection of Yamanashi Test Line was realized by inductive radio system which consists of onboard receiving antenna and cross inductive cable. By analyzing amplitude and phase variation of inductive electromotive force from receiving antenna, position and speed information could be determined. However, coreless LSM is proposed for wheel-on-rail system in this paper not for suspension system. We are going to introduce a novel SM (Superconducting Magnet) coreless LSM, which will provide propulsion force for wheel-on-rail high speed train. Inductive cross-loop cable could also be applied for this proposed system, but considerations should be taken due to effects of tracks and complicated electromagnetic field. Keywords : Coreless LSM, Position detecting method, high speed train

1. Introduction

Construction and maintenance cost is a big issue for high speed maglev train. So some researchers are

showing interests to develop a hybrid system combining advantages of both conventional wheel-on-rail

system and Maglev propulsion system. This hybrid type system is based on wheel-rail method, but it

enables to overcome the speed limitation by adhesion because it is operated by a non-contact method

using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility

with the conventional railway systems. A novel SM (Superconducting Magnet) coreless LSM (Linear

Synchronous Motor) system, which will provide propulsion force for wheel-on-rail high speed train is

proposed. Design models of coreless-typed LSM with various distributed and concentrated windings for

600 km/h very high speed train were discussed [1]. As an indispensable subsystem, position detection

system is very important for operation control of this hybrid system, because traction system of high

speed train needs precise location and speed information to carry out the operation tasks with safety and

reliability. This paper will focus on position detecting method for high speed train with coreless LSM.

The rest of this paper is organized as follows, section 2 will introduce positioning method for transrapid

and our proposed hybrid system, in section 3, considerations of positioning method for hybrid system are

discussed, and conclusions are made in the final part.

†교신저자: 과학기술연합대학원대학교 철도시스템공학(sunyan@krri.re.kr)

* 한국철도기술연구원, 초고속자기부상철도연구단

2. Positioning method for transrapid and hybrid system

Many researches have been done to study positioning method for Germany suspension system-

Transrapid. To get precise position data, absolute positioning and relative positioning are required.

Relative positioning is used to get high-accuracy position data and absolute positioning is used to

eliminate cumulated errors from relative position signals. Both absolute positioning and relative

positioning are needed for coreless LSM propelled hybrid rail-on-wheel system, however hybrid system

need different positioning method from tranrapid due to different configurations.

2.1 Positioing method for transrapid

2.1.1 Absolute positioning: location reference flag reading [2]

(a) Location reference flags on guideway (b) Location reference flag with binary code “1011”

Fig. 1 Location reference flag of Transrapid

(a) Hardware structure of the reference flag-reader (b) Layout of the transmitting/receiving coils

Fig.2 Location reference flag-reader

2.1.2 Relative positioning: long stator tooth-slot reading [3]

Fig.3 Transrapid configuration

(a) Sensor configuration and coil arrangement (b) Signal processing principle

Fig.4 Long stator tooth-slot reader

2.2 Positioning method for hybrid system

ERTMS/ECTS (European Rail Traffic Management System/European Train Control System) is the

standard for rail traffic control. Eurobalises implemented on the track acting as positioning markers, and

odometer estimates the train position. Each Eurobalise shall transit information securely between the track

and on-board system. Eurobalise only communicates with train when the train passes over it, and it is also

used for resetting odometer [4]. Eurobalises realized absolute positioning and odometer realized relative

positioning according to the standard.

Fig.5 Position system based on inductive loop cable [5]

Considering compatibility with conventional rail-on-wheel train, Eurobalise is also applicable for

hybrid system. Relative positioning can refer to Japanese Maglev train positioning system, which consists

of inductive cross loop cable and onboard antenna. Inductive loop cable with fixed shape is laid along the

rails and receiving antenna is installed at the bottom of the train. High frequency alternating current is

injected into cross cable as excitation, and magnetic field with opposite direction is produced by adjacent

rings. According to Faraday’s law of electromagnetic induction, an inductive electromotive force is

produced between both ends of the coils. When the train operates along the rail, speed and position

information can be determined by amplitude and phase change of inductive electromotive force [5].

3. Considerations of positioning method for hybrid system

Compared with Japanese maglev system, proposed hybrid system has different configurations.

Propulsion coils of Japan system are installed on both sides of the U shaped track and inductive loop

cable is laid on the track surface, while LSM coil used for propulsion is installed on the track. So, we

need to consider complicated magnetic field around track. Metal sleepers and metal bogie would affect

magnetic field so as to affect electromotive force used to derive position information. Simulation is done

to verify magnetic flux density changes due to existence of metal materials.

Fig.6 Hybrid system configuration [1]

For any kind of material, both magnetization and eddy current effects exist. Compared with the vacuum

magnetic field distribution, the first major impact is an enhancement of the spatial magnetic field, while

the second is to weaken it. In addition, the eddy current effect is related with the frequency of the

magnetic field [5]. Aluminum, stainless steel and iron bulks are taken as metal sleepers to make

simulation under the same conditions.

Table 1 Property of metal materials

Metal Materials Relative Permeability Conductivity (s/m)

Aluminum 1.000021 3.8x107

Stainless Steel 1 1.1 x106

Iron 4000 1.03 x107

Equivalent model of inductive loop coil is shown in Fig.7 (a), and 3D simulation model is made to

according to equivalent loop coil.

(a) Equivalent model of inductive loop coil [5] (b) Simulation model with coil and metal bulk

Fig.7 Simulation model

0.00 0.25 0.50 0.75 1.00 1.25 1.50Distance [meter]

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

Mag

_B

Maxwell3DDesign4XY Plot 1 ANSOFT

Curve InfoMag_B

Setup1 : LastAdaptiveFreq='2MHz' Phase='0deg'

0.00 0.25 0.50 0.75 1.00 1.25 1.50Distance [meter]

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

Mag

_B

Maxwell3DDesign3XY Plot 1 ANSOFT

Curve InfoMag_B

Setup1 : LastAdaptiveFreq='2MHz' Phase='0deg'

0.00 0.25 0.50 0.75 1.00 1.25 1.50Distance [meter]

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

Mag

_B

Maxwell3DDesign3XY Plot 1 ANSOFT

Curve InfoMag_B

Setup1 : LastAdaptiveFreq='2MHz' Phase='0deg'

0.00 0.25 0.50 0.75 1.00 1.25 1.50Distance [meter]

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

Mag

_B

Maxwell3DDesign3XY Plot 1 ANSOFT

Curve InfoMag_B

Setup1 : LastAdaptiveFreq='2MHz' Phase='0deg'

Magnetic flux density along coil extension line affected by different metal material is shown in Fig.8.

Due to high permeability, iron bulk enhanced magnetic field distribution, while eddy current effect of

aluminum and stainless steel bulk weaken the magnetic field distribution. So we need to design a

receiving coil that can get less effect because of metal bulks. Future study will discuss coil design.

(a) No metal bulk (b) Iron bulk

(c) Aluminum bulk (d) Stainless steel bulk

Fig.8 Magnetic field affected by different metal materials

4. Conclusions

Position detection method is discussed for hybrid coreless LSM system in this paper. According to system

analysis and comparison with high speed maglev of transrapid and Japanese maglev system, eurobalise is a

good candidate for absolute detection and inductive loop cable is applicable for relative detection. Due to

complicated magnetic field, metal bulks around positioning system would affect magnetic field distribution

so as to affect electromotive force used to derive position information. Simulation verified considerations of

metal bulks and future study will design receiving coil that get less effect by metal bulks.

References

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Structure of Linear Synchronous Motor for 600km/h Very High Speed Train, Proceedings-International

Symposium on Linear Drives for Industry Applications.

[2] Cunyuan Qian, Zhengzhi Han and Weida Xie (2007) Research on Absolute positioning system for

high-speed maglev train, Proceedings of the 2007 IEEE International Conference on Mechatronics and

Automation, pp.922-926

[3] Song Xue *, Zhiqiang Long, Ning He and Wensen Chang (2012) A high precision position sensor

design and its signal processing algorithm for maglev train, Sensors, pp.5225-5245

[4] Dhahbi, S, Abbas-Turki, A. ; Hayat, S. ; El Moudni, A. (2011) Study of the high-speed trains

positioning system: European signaling system ERTMS/ETCS, 2011 4th International Conference on

Logistics (LOGISTIQUA), pp. 468-473

[5] Dai C1, Dou F, Song X, Long Z.(2012) Analysis and design of a speed and position system for maglev

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