A hybrid railway traction system with fuel cells (FCs) and electric double layer-capacitors (EDLCs) is discussed in this paper. This system can save FC costs and absorb the regenerative energy. A method for designing FCs and EDLCs on the basis of the output power and capacitance, respectively, has not been reported, even though their design is one of the most important technical issues encountered in the design of hybrid railway vehicles. Such design method is presented along with a train load profile and an energy management strategy. The design results obtained using the proposed method are verified by performing numerical simulations of a running train. These results reveal that the proposed method for designing the EDLCs and FCs on the basis of the capacitance and power, respectively, and by using a method for controlling the EDLC voltage is sufficiently effective in designing efficient EDLCs and FCs of hybrid railway traction systems.
Some level-crossing control methods have been proposed as a subsystem of the Communications-Based Train Control (CBTC) system. In this method, the warning starts according to the forecasted time when a train reaches the level crossing; the forecasted time is calculated on the basis of the speed and detected position of the train. Therefore, we have analytically clarified the quantitative relations among the train's position at the start of warning, train-running speed, and maximum train speed, which have not yet been shown. In this paper, we propose a speed-control method for reducing the warning time according to the train-speed characteristics in the train level-crossing control for the CBTC system. In addition, this method has been proposed for reducing the warning time when a train comes from the opposite direction according to the conventional level-crossing control. Therefore, we also propose the application of the speed-control method to the case when a train comes from the opposite direction. In addition, we show the effect of the reduction in the warning time by applying this method for speed control without train delay.
Rigid conductor lines are used in many subways, because the use of such conductor lines reduces the risk of accidents and because less space is required for their installation. However, as the unevenness of the sliding surface of the rigid conductor lines significantly influences the fluctuations in the contact force between pantographs and contact lines, it is necessary to decrease the unevenness at the construction as well as the maintenance stages. In order to investigate the installation accuracy of overhead rigid conductor lines, we have developed a device that accurately and continuously measures the unevenness of the sliding surface. By using this measuring device, we have confirmed that the unevenness of the sliding surface depends on various factors such as the sag between the support points, the deformation of the aluminum base or the conductive rail in the case of a long wavelength, the slight sagging unevenness between the bolts of the long ear, the undulating wear etc. This paper describes the actual unevenness conditions and the technical methods for decreasing the unevenness of the sliding surface of overhead rigid conductor lines.
Experts working for railway schedule planners still have to devote considerable time and effort for creating rolling stock allocation plans. In this paper, we propose a semiautomatic planning method for creating these plans. Our scheduler is able to interactively deal with flexible constraint-expression inputs and to output easy-to-understand failure messages. Owing to these useful features, the scheduler can provide results that are comparable to those obtained by experts and are obtained faster than before.
Examination methods that involve a slide between contact wires and contact strips are methods that simulate the actual current-collecting phenomena encountered in the railway field. However, the influence of a breaking arc on the mass and surface of contact materials cannot be clarified by these methods, because the mass change includes the wear and arc erosion that occur during the methods. This paper tries to clarify these problems by using a breaking arc that is generated without using a wire to begin an arc discharge. The breaking arc is generated in this way to resemble the phenomena of arc generation in the railway field.
Whenever there is a disruption in areas with a high frequency of train operations, the delays of trains propagate and train passengers have to suffer inconvenience. A rescheduling of the train operations is then conducted by train dispatchers to revert to the original operational plan. The task is quite difficult and a severe burden for the dispatchers because of a variety of options for reverting to the original plan, the necessity for a swift action, and the absence of a proper evaluation criterion. Consequently, a computer-aided rescheduling-support system is required. In this paper, we present a mathematical programming approach for train rescheduling, focusing on minimizing the passengers' arrival delay at their destinations. We simultaneously model the train operations and passenger flow on the basis of mixed integer programming (MIP), and we obtain an optimal rescheduling plan in reasonable time in the case of a small disruption.
Diesel engine lithium-ion battery hybrid vehicles are gaining attention because the energy consumption during their operation and exhaust emission can be reduced considerably. However, designing a reasonably accurate method for the engine power and battery energy has not yet been proposed, though the above mentioned type of traction system can help in realizing an environment-friendly railway vehicle. In this paper, a design method for the battery capacity (energy) and engine output is proposed in the case of a control strategy in which the sum of the kinetic energy of the vehicle and the battery energy is maintained constant. The proposed method is verified by the velocity/state of charge of the battery charts obtained in the experimental tests. The proposed design method can be used to develop the environment-friendly railway traction systems for non electrified lines.
In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an eddy current will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the eddy current loss is extremely important. This study examined ground coils in which both the eddy current loss and temperature increase were small. Furthermore, quantitative comparison for the eddy current loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low eddy current loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.
The Hokuriku Shinkansen line (from TAKASAKI to KANAZAWA) is driven by an AC traction system. A special feature of the line is its division into 50Hz and 60Hz power frequency sections. Each subsystem, such as a train traction system or signalling system, can function at the two power frequencies. However, the carrier frequencies of the track circuit for the existing “DS-ATC” (Digital communication & control for Shinkansen Automatic Train Control device) are tuned for electromagnetic compatibility with the harmonics of the 50Hz power frequency. Firstly, the track circuit frequencies were chosen. Secondly, the track circuit was designed. The accuracy of the track circuit constants and of the wayside cable characteristics was confirmed through direct measurements and from distribution diagrams of the absolute values of the signal voltage, current, and phase measured through experiments. Thirdly, the behavior of the devices was recorded over two months under the field conditions for operation in the Shinkansen section composed of insulated track circuits. All the parameters such as the shunting resistance, response time of train control, and signal amplitude and its fluctuation that indicate the maximum controllable field conditions for operation in the Shinkansen section track circuit length, SN ratio, BER (bit error rate), and interference with frequencies of existing signalling devices were confirmed to be suitable for the required conditions. Subsequently, the accuracy of the obtained data and the suitability of the method for designing the track circuit of an actual section were examined.
With an increase in the maximum speed of Shinkansen trains, it becomes imperative to resolve aerodynamic and aeroacoustic problems related to pantographs. Hence, some methods based on flow control have been studied to improve the aerodynamic and aeroacoustic characteristics. In this study, the authors attempted to control the flow around a pantograph by using synthetic jets. The results of numerical and experimental tests indicate that the synthetic jets can stabilize the flow around the bluff-shaped pantograph head, thus resulting in a reduction in aerodynamic noise.
With growing concerns over our environment, more and more people in automakers, governments and customers think that the electric drive becomes more attractive research. Since electric motors play an important role in both EVs and HEVs, it is a pressing need for researchers to develop advanced electric machines. As one of the candidates, permanent magnet flux switching machine (PMFSM) with additional coil excitation has several attractive features compared to interior permanent magnet synchronous machines (IPMSM) conventionally employed in HEV. The variable flux control capability and robust rotor structure make this machine becoming more attractive to apply for high speed motor drive system coupled with reduction gear. This paper presents an investigation into design possibility of 6-slot 5-pole PMFSM with hybrid excitation for traction drives in HEVs. An improved design is examined to gain a better performance in its maximum torque and power production. The final designed machine enables to keep much power density compared to existing IPMSM installed on the commercial SUV-HEV.
This paper presents asymmetric circuit models and an inductance parameter measurement method for Permanent Magnet Linear Synchronous Motors (PMLSMs). The reason why the tested PMLSM with surface permanent magnet structure exhibits both asymmetry and salient pole natures is investigated. Asymmetric circuit models considering the saliency and inductance harmonic effects are discussed for PMLSM fed by three-phase three-wire power source systems. All fundamental and harmonic inductance parameters are easily determined by a standstill test using a single-phase commercial source. Experimental and simulation results on a single-sided PMLSM with a 3-phase, 4-pole and 14-slot mover demonstrate the validity of the proposed method.
This paper presents one of the embedding methods for a genetic algorithm (GA) in the three-dimensional finite element method (3-D FEM). We use a shell script to automate the preprocesses of the 3-D FEM and to perform the genetic operation for the GA. In this paper, a surface permanent-magnet synchronous motor (SPMSM) was selected as a simple model for optimizing the shape. The capability of this method was confirmed by decreasing the cogging torque. Moreover, the evaluation of GA was performed by distributing the analytical model to several PCs for parallel processing, and the computing time was thus shortened.
This paper presents an experimental discussion on a 6-kW, full-bridge, zero-voltage switching bidirectional isolated dc/dc converter for a 53.2-V, 2-kWh Li-ion battery energy storage system. The combination of high-frequency switching devices, 600-V/200-A IGBTs and 100-V/500-A MOSFETs with a high-frequency transformer reduces the weight and physical size of the bidirectional isolated dc/dc converter. The dc voltage on the high-voltage side of the converter is controlled in a range of 300V to 355V as the battery voltage on the low-voltage side varies from 50V to 59V. Experimental verification of bidirectional power flow into (battery charging) or out of (battery discharging) the Li-ion battery bank is also presented. The maximal efficiency of the dc/dc converter is measured to be 98.1% during charging and 98.2% during discharging, excluding the gate drive loss and control circuit loss.
In this paper, a novel method for automatic identification of a surgical operation and on-line recognition of the singularity of the identified surgical operation is proposed. Suturing is divided into six operations. The features of the operation are extracted from the measurements of the movement of the forceps, and then, on the basis of the threshold criteria for the six operations, a surgical operation is identified as one of the six operations. Next, the features of any singularity of operation are extracted from operator's surface electromyogram signals, and the identified surgical operation is classified as either normal or singular using a self-organizing map. Using the built laparoscopic-surgery simulator with two forceps, the identification of each surgical operation and the distinction of the singularity of the identified surgical operation were carried out for a specific surgical operation, namely, insertion of a needle during suturing. Each surgical operation in suturing could be identified with more than 80% accuracy, and the singularity of the surgical operation of insertion could be distinguished with approximately 80% accuracy on an average. The experimental results showed the effectiveness of the proposed method.
This paper describes characteristics of a multiphase boost chopper on the basis of the difference between its phase number and operation mode. First, this paper presents a theoretical analysis of an input current ripple in a multiphase boost chopper controlled with CCM and DCM. For analysing CCM, the input current ripple in an n-phase boost chopper is expressed by a general formula using a duty ratio. This expression clarifiers integrally the relations between the phase number and input current ripple. The current ripple in CCM is highly reduced than that in DCM for the tested four-phase boost chopper. Furthermore, this paper presents a comparison between the converter efficiency and step response of a four-phase boost chopper controlled in CCM or DCM. The efficiency in CCM is higher than in DCM by 0.5[%]. The phase number affects the step response characteristics in CCM. However, the phase number does not affect the step response characteristics in DCM.
Short-circuit faults of winding due to the deterioration in the insulation is one of the most probable faults in motor drive systems. An easy and effective fault diagnosis method has been strongly required to assure operation with high reliability. This paper proposes a novel method for diagnosing both short-circuit faults and insulation deterioration in windings. This method involves an impulse voltage test and probabilistic process for gauging the probability of fault occurrence by considering the distributions of features depending on the condition of the winding. In this paper, first, we discuss the results of several impulse tests on the winding. Second, two features that represent the characteristics corresponding to the condition of the winding are induced, and their feature distributions are determined. Third, we introduce the probability that can be used to diagnose the condition of the winding. The average and standard deviation of both features are calculated. By using the calculated values and features observed in a target winding to be examined, the fault probability is computed. Finally, the usefulness of the proposed diagnosis method is verified by performing experiments involving the use of faulty and deteriorated windings.
A DC-electrified railway system that is fed by diode rectifiers at a substation is unable to return the electric power to an AC grid. Accordingly, the braking cars have to restrict regenerative braking power when the power consumption of the powering cars is not sufficient. However, the characteristics of a DC-electrified railway system, including the powering cars, is not known, and a mathematical model for designing a controller has not been established yet. Hence, the object of this study is to obtain the mathematical model for an analytical design method of the regenerative braking control system. In the first part of this paper, the static characteristics of this system are presented to show the position of the equilibrium point. The linearization of this system at the equilibrium point is then performed to describe the dynamic characteristics of the system. An analytical design method is then proposed on the basis of these characteristics. The proposed design method is verified by experimental tests with a 1kW class miniature model, and numerical simulations.
Recently, global warming and the problem with successfully incorporating environmental safeguards have promoted the need for a more power-efficient motor. Therefore, as a driving source, permanent magnet synchronous motor (PMSM) with concentrated winding is widely used as the important device for a variety of fields. However, a PMSM with concentrated winding generates more vibrations than that with distributed winding because of a radial electromagnetic force. This paper describes the influence of a new skewed rotor on the characteristics of a concentrated winding PMSM. We investigated the influence by using a three-dimensional finite element analysis (3-D FEM) and several measurements. In addition, we presented that the proposed rotor is effective in reducing the radial electromagnetic force without decreasing the motor efficiency.
Recently laminated bus bars are being used in power electronics circuits to realize low inductance. When high-speed switching is required, an electromagnetic induced noise is generated because the pulse current generates a magnetic field in the neighborhood of the power circuits. In this research, the induced noise is verified from the relationship between the noise current and the line impedance of bus bars by the difference of the inverter circuit structure. Furthermore, the induced noise that is related to the circuit structure and common- or normal-mode currents in the circuit operation is discussed by considering the experiments and equivalent circuit simulations.
A calculation method of DC-link voltage variation of PWM rectifier-inverter system at a stepwise change in output power is proposed. The results of the calculation are confirmed by experiment. In addition, when the capacitance of DC-link is reduced, the parameters that have significant influence on the DC-link voltage variation are extracted.
The temperature control of the environmental examination device has loss of the energy consumption to cool it while warming it. This paper proposed a tempareture control system method with energy saving for the enviromental examination device without using cooling in consideration of temperature characteristics.
Sodium borohydride (NaBH4) is attractive as fuel for fuel cell electric vehicle because of its high energy density. Hydrogen reactor, which generates hydrogen gas by hydrolysis of NaBH4, has been proposed. This letter verified that 100W fuel cell was able to generate electric power appropriately by hydrogen gas generated from the hydrogen reactor.