We carry out a technological examination for improving the positional detection accuracy of position tracking. In this paper, we focus on positional detection technology that uses a scale in which slits are carved at a certain constant period. We develop phase modulation signal generation technology that removes a signal of two frequencies of a one-signal detection track. We report on the detection principle and the results of the principle verification experiment.
Monitoring data under various conditions are obtained from railway facilities. These data are utilized to obtain the real-time conditions and to detect a malfunction using a threshold; however, they are rarely utilized to predict future conditions. Therefore, we have been trying to develop an actual prediction method to support appropriate maintenance work for an electric point machine by focusing on the locking-error position data that were stored in the monitoring system of an electric point machine. In this paper, a short-term prediction method is proposed to calculate the locking-error position for the next day. This paper also shows the validation results of the proposed method and the practical use of our method.
Although an electric railway is an ecological transportation system, there are some obstacles when an electric railway is installed: the high cost for installation and the detrimental effect on the environment. A contactless power transfer system (CPT system) is a solid solution for these obstacles. However, a CPT system for a railway application needs to have a high capacity and a tolerance to the misalignment of the coils. In this paper, inductive power transfer theory, which is able to transfer a greater amount of energy than the electromagnetic resonance method, is chosen, and its tolerance to the misalignment is our focus. The authors measure various core shapes, and their coupling coefficients, leakage inductances, and excitation inductances according to the misalignment are obtained with a finite element method (FEM) analysis. By using these parameters, the transmitted power and efficiency are calculated by two equivalent circuits: the S/S circuit and the S/P circuit. Finally, by comparing the parameters and transmitted power of each core shape and circuit, the authors show that the circular core can transfer 100kW of energy for a misalignment of 300mm.
Time delay deteriorates bilateral control performance. Although many time delay compensation methods have been proposed, there is no clear index for selecting which compensation method should be used. Furthermore, such indices become even more necessary in systems with multiple degrees-of-freedom, as performance requirements differ for each functional mode according to the human sense that is evaluated. Therefore, in this paper, an indexing and design method for functional modes using sensory evaluation to select appropriate compensation methods is proposed. The experimental results demonstrate the validity of this proposal.
In recent years, the number of vehicles with automatic gap control (AGC) (e.g., adaptive cruise control) has increased with the development of vehicle control technology. AGC mainly helps to ease driver fatigue on highways. Vehicles equipped with AGC can maintain an appropriate distance between two vehicles. Therefore, the traffic flow can be improved by AGC equipped vehicles. In this research, we develop a traffic flow model that considers AGC equipped vehicles, and is based on the Nagel-Schreckenberg model, which is a probabilistic cellular automaton model. The Nagel-Schreckenberg model can reproduce the basic features of traffic flow. On analyzing the mathematical model for the traffic including AGC equipped vehicles, we can obtain analytical solutions of the traffic flow and the average velocity.
The modular multilevel cascade converter (MMCC) family has been attracting attention from power electronics and power system engineers because it has been showing considerable promise as one of the next-generation high-power high-voltage/medium-voltage power converters. This paper provides an intensive discussion on power-flow analysis of three MMCC members with star configuration, focusing on dc-mean-voltage balance/regulation and ac-voltage mitigation control of all the floating dc capacitors. Most existing analysis methods are based on single-phase circuits, which make it difficult to derive capacitor voltage regulation/mitigation methods relying only on circulating currents and zero-sequence voltage. The power-flow analysis and regulation/mitigation methods developed in this paper are characterized by applying the αβ0 coordinate transformation(s). The validity of the power analysis and the regulation/mitigation method is confirmed by simulation using the PSCAD/EMTDC software package.
Wireless power transfer using a metallic tube with an axial slit was attempted to demonstrate the wireless power transfer using magnetic resonance coupling to the diagnostics infrastructure. The transmission efficiency with variable distance was measured using the transmission and receiver resonators in the tube. Besides, the transmission and receiver resonators were respectively set outside and inside the tube. These experiments are carried out in the computational study using FDTD method.
This paper presents an experimental discussion on modular multilevel cascade converters based on double-star chopper cells (MMCC-DSCC). Hereinafter, a single MMCC-DSCC is referred to simply as a “DSCC”. A couple of DSCCs are used to form a front-to-front (FTF) system capable of dc voltage matching and galvanic isolation between two dc grids. The FTF system can be considered as a dc-ac-dc power conversion system including an ac-link high-power transformer. The higher the ac-link frequency, the smaller and lighter are the ac-link transformer and dc capacitors. When the so-called “phase-shifted-carrier PWM” is applied to the DSCC, theoretical analysis and computer simulation have confirmed that a ratio of the carrier frequency with respect to the ac-link frequency can be reduced to 5/2. This paper designs, constructs, and tests a 400-Vdc 10-kW downscaled FTF system with a carrier frequency of 450Hz and an ac-link frequency of 180Hz, where their ratio is 5/2. Experimental waveforms obtained from the downscaled system are compared with simulated ones obtained from a software package, PSCAD/EMTDC, under the same operating and circuit conditions. They agree well each other not only under steady states but also under transient states.
This paper presents a design procedure for output current and damping controls of a matrix converter to suppress the LC filter resonance and to improve the transient current response. With a conventional design method that provides preference to stability, the damping control leads to a large output current overshoot and a large error of the cut-off frequency of the output current control between the desired and the actual values. Thus, in order to obtain a desired transient response with maintaining a stable operation, this paper describes a modified control block diagram in which a reference filter is added to suppress the output current overshoot. In addition, a design flowchart using Bode diagrams is also presented to reduce the error of the cut-off frequency of the output current control and to ensure a desired gain margin. From the experimental results, it is verified that the damping control designed with the proposed method suppresses the filter resonance. As a result, the damping control reduces the input current THD (total harmonic distortion) by 52.3% compared to the result without the damping control. In addition, the proposed design method reduces the output current overshoot of 67.6% and an error between the desired and the obtained cut-off frequencies to less than 1/6 compared with the conventional method because of the proposed reference filter and the design flowchart. Finally, the effects of discretization and a voltage-type commutation sequence for the cut-off frequency of the output current control are analyzed.
In this paper, the effectiveness of maximum power point tracking (MPPT) control is evaluated. A photovoltaic panel is set on the roof of a building and on a car moving on a city road. Then, the static characteristics of the panel are recorded by a high-speed measurement system. Perturbation-and-observation controllers with various sampling frequencies and various perturbation voltages are simulatively evaluated by applying the recorded data. In the simulation study of the roof application, a low-speed MPPT controller, or a conventional controller is appropriate. However, in the simulation study of the car application, an extremely high sampling frequency of MPPT controllers achieves better MPPT efficiency because these controllers capture the rapidly changing optimum voltage appropriately.