Wide-Angle Fovea Vision Sensor (WAFVS) system, inspired by the functionality of the human eye, was designed and developed to allow single vision sensors to be used for multiple purposes. The authors think that the WAFVS system is suitable for use in planetary exploring rovers, because one of severe problems in the vision systems of rovers, UAVs and satellites involves the management of payloads. This paper describes the multi-purpose utilization of the WAFVS system, which includes the following tasks: (1) observing the environment displayed to the operator to allow the remote navigation of the rover, (2) recording images of important scenes by changing the view direction of the WAFVS, and (3) monitoring whether the instruments on the rover work correctly. Moreover, this paper includes experiments and discusses a technique to display images to the operator when an eye-tracking device is applied as a target coordinate input device, in order to assist the operator with their tasks. An accuracy index, i.e., a measurement error of a target, is defined in order to evaluate the performance of a combination that incorporates the vision sensor, the coordinate input device, and the image display method.
This paper proposes a new pulse width modulation (PWM) carrier distribution technique for reducing motor electromagnetic noise. The proposed method uses only two carrier frequencies and controls PWM harmonics by the transferring probability of the two carrier frequencies. The proposed method is verified by experiments using 0.8kW PMSM.
Smart timetabling optimization is a cost-effective way to improve the quality of railway service. Partial introduction of rapid trains is one of the effective methods for improving passenger service quality. However, it is difficult to concretely perform smart train scheduling. In this paper, we apply mixed integer programming for minimizing the total travelling time of passengers to obtain optimal train scheduling for the combination of all-station and partially introduced rapid trains. This method requires higher computational time to obtain the optimal solution than other metaheuristic methods; however, the solution guarantees to be an optimal one. We also propose an appropriate method to digitize the OD (Origin Destination)-patterns, i.e., the traffic demand inputs between two stations, which are suitable for the framework of the proposed mixed integer programming method. We apply the method to a case study of a commercial subway and demonstrate the advantages of the proposed train service with the partial introduction of rapid trains.
In digitally controlled circuits for power electronic circuits, sampling data are important because the digital control circuit is operated on the basis of these data. If the sampled values have been affected by switching noise from the power circuit, the control stability of the circuit would be disturbed. This paper proposes a noiseless sampling method that can sample a value without being affected by the switching noise. The synchronous sampling method may be affected by the switching noise depending on the duty ratio of the circuit. The noiseless sampling method does not obtain data immediately after turn-on and turn-off switching. The control circuit can avoid the switching noise by using noiseless sampling, which leads to a disturbance in the control circuit and enhances the robustness of the circuit when applying the multisampling method. Experimental results are presented to verify that the current control of the proposed sampling method is not disturbed by the switching noise even in the absence of a noise filter.
When the load frequency of a modular matrix converter (MMxC) coincides with the source frequency, the capacitor voltages of the modules diverge. In this paper, control of the capacitor voltages under synchronization in positive and negative sequence between load frequency and source frequency is proposed. The effectiveness of the proposed control was verified though simulations and experiments.
This paper deals with a merging section in a personal rapid transit system, and a new control strategy that allows a waiting time limit is proposed as a method to reduce the waiting queue. Vehicles arrive at a merging section from main and sub lines. Since vehicles on the main line have priority, a queue is formed on the sub line in order to avoid the collision of vehicles. Vehicles on the main line need to stop when the waiting time of the last vehicle on the sub line queue exceeds the limit. The relation between the waiting time limit and the behavior of traffic on the main and sub lines (characterized by the mean queue length and queuing delay) is derived explicitly by using a Markov chain model. Moreover, the control strategy for the queuing delay on each line is developed on the basis of the obtained relation. We compare the results obtained by using the present strategy with those obtained by using another strategy. The comparison shows the validity of the present strategy in cases where the probability of vehicle arrival on the sub line is low.
In this research, we investigate magnetic material properties by using numerical analysis taking into account the power semiconductor properties in an inverter circuit. To consider magnetic properties, we use play model and Cauer's equivalent circuit theory for depicting magnetic hysteresis. To consider power semiconductor properties, an inverter circuit analysis taking into account the on-voltage characteristics of a semiconductor is carried out. As a result, on the basis of the numerical analysis, minor loops caused by the on-voltage can be depicted properly and the analyzed iron losses of the magnetic material can almost reproduce the experimental results.
A gradient Si steel sheet, which has high Si content in the surface layer and low Si content in the center of the thickness, shows extremely low iron loss in the high frequency range. In this paper, the magnetic properties of gradient Si steel sheets under compressive stress were investigated. In a 3.5%Si steel sheet, the iron loss under compressive stress increases with increase in compressive stress. On the other hand, a gradient Si steel sheet shows extremely low iron loss under compressive stress. This decrease is due to the residual tensile stress in the surface layer of the gradient Si steel sheet. To evaluate the effect of core materials on the iron loss of the motor, we fabricated IPM (Interior Permanent Magnet) motors using 3%Si steel, 6.5%Si steel, and gradient Si steel sheets. In the motor using a 3%Si steel sheet, the motor loss increases after the heat shrinking. On the other hand, in the motors using 6.5%Si steel and gradient Si steel sheets, the motor loss shows little change after the heat shrinking.
Electro-magnetic interference (EMI) noise radiated from the DC cable of photovoltaic power conditioner systems (PCS) is a serious problem for radio transmission equipment. In order to prevent the interference, the International Special Committee on Radio Interference (CISPR) is discussing to determine a noise regulation value for this issue. To reduce the radiated noise, this paper studies the attenuation characteristics of EMI filters that are connected to both the DC- and the AC-sides of the PCS. In this paper, it is pointed out that the EMI filters do not show their own attenuation characteristic if those are connected to the PCS. In particular, when EMI filters are connected to both the DC- and AC-sides of the PCS, a specific series resonant frequency is observed and deteriorates the attenuation characteristics of both EMI filters. In order to prevent this problem, a design method for EMI filters which can reduce the common-mode EMI noise effectively, is proposed in this paper. Further, the effectiveness of the proposed method is confirmed through experiments.
This paper describes a soft-switching interleaved power factor correction (PFC) converter with a lossless snubber. AC/DC converters require a unity input power factor characteristic with highly efficient operation to prevent the inflow of harmonic current to the power source. The proposed PFC converter improves the input current ripple with interleave control. The converter realizes a high efficiency by the soft-switching operation of all switching devices without a large auxiliary resonant circuit. This paper introduces the soft-switching operation of the converter. In order to confirm the validity of the proposed converter, experiments with a prototype of the PFC converter have been performed. The experimental results indicate that the proposed converter can realize the soft-switching operation of all switching devices, a reduction in the input current ripple, a unity input power factor of 98% or more, a sinusoidal input current, and constant output voltage control. The efficiency of the proposed PFC converter with a lossless snubber is higher than that without the lossless snubber. The results presented in this paper confirm the validity of the proposed converter.
This paper presents a wireless charging system that utilizes an electric double layer capacitor (EDLC) as a power source for an electric assisted bicycle. The proposed system was optimized in terms of miniaturization. First, the minimum energy of the EDLC was evaluated. The results showed that the energy source in the proposed system can be smaller than that in the conventional system when the energy density of the EDLC is improved more than 1.52 times. Second, the coil of the wireless power transmission and the charger were analyzed. Short- and open-type coils of the same size were compared in experiments. The results showed that the short-type coil can be further miniaturized than the open-type coil at the same resonance frequency. Third, the volumes of the EDLC and converter were evaluated. The results showed that the volume of the boost type can be reduced by 30% compared to that of the buck type. Finally, in order to reduce the number of devices in the proposed system, the diode bridge rectifier was replaced with a three-phase inverter. This reduced the number of devices of the proposed system by one-third.
This paper proposes a single-phase AC-AC current source converter with improved current waveforms. The main circuit of the converter is a three-phase bridge circuit that contains a capacitor for the management of instantaneous power with twice the source frequency. Two types of pulse width modulated (PWM) switching patterns are employed to regulate the output power and to obtain the smoothing DC current. The circuit configuration and the PWM operation are demonstrated in the paper. The experiments prove that the converter has sinusoidal voltage and current in both the input and the output.
Our institute has missions to create and support technologies in local industries. Our group is engaged in the development of the in-wheel motor and suspension in OVEC (Okayama Vehicle Engineering Center for the next EV).