In this paper, the authors propose a surge energy recycling converter. The proposed circuit is able to reduce the surge voltage of the secondary side and to recycle the surge energy, in a DC-DC converter stage of a conventional front-end power supply. Thus, the use of the low blocking voltage rectifier elements is possible, and the conduction loss is decreased. Further, the amount of surge energy that is wasted in a snubber circuit is decreased. As a result, the efficiency of the DC-DC converter stage is improved by about 1 percentage point.
This paper proposes a novel mathematical dynamic model to represent steady-state and transient-state characteristics of rotor slot harmonics of an induction motor for sensorless control. Although it is well known that the rotor slot harmonics originate from the mechanical structure of the induction motor, a mathematical model that describes the relationship between stator/rotor currents of the induction motor and the slot harmonics has not yet been proposed. Therefore, in this paper, a three-phase model of the induction motor that depicts the rotor slot harmonics is developed by taking into consideration the magnetomotive force harmonics and the change in the magnetic air gap caused by the rotor slots. Moreover, the validity of the proposed model is verified by comparing the experimental results and the calculated values.
A screw hole is incorrectly molded if the pin on the mold is broken when the plastic is molded by injection molding. Sampling inspection is carried out manually to identify the incorrectly molded screw hole. In the sampling inspection, the incorrectly molded screw hole on the molded plastic frame is rarely overlooked. Therefore, the development of a system for the high-precision identification of the incorrectly molded screw hole is required. The purpose of this study is to develop a screw-hole inspection system that distinguishes between a correctly molded screw hole and an incorrectly molded one. In this paper, a screw-hole inspection system is proposed. There is a need to capture clearly the screw hole on an uneven plastic frame and therefore, a multi-camera system is used. The proposed system consists of several Web cameras with the individual adjustable focus. Moreover, the inspection of the screw holes is performed using an inspection algorithm that is developed for a multi-camera system. When 2548 correctly molded screw holes and 2940 incorrectly molded screw holes were inspected by the proposed system, the inspection success rate was 100.0%. Finally, we have verified its effectiveness by performing an experiment.
Advances in power semiconductor devices have contributed to the realization of high-performance power converters and high-precision motor positioning. However, high-speed switching of power devices lead to a high-frequency leakage current and/or electromagnetic interference (EMI). On the other hand, it has been considered that the leakage current has no relation to motor position control in servo drive systems. This paper analyzes the influence of the high-frequency leakage current on motor positioning and describes its mechanism. Experimental and simulation results show that the high-frequency leakage current may cause variations in the motor position with a frequency that is twice the line frequency.
An increasing number of voltage-driven-type PWM inverters have begun to be used recently for electrical equipment in buildings owing to energy conservation considerations. However, common-mode currents originate from this type of inverters, and problems due to such common-mode currents flowing in grounding systems of buildings have increased with their increased use. While it is necessary to study countermeasures to overcome these problems by considering the entire circuit in question (since common-mode currents flow in the whole circuit including power-supply and grounding systems), there seem to have been very few such studies. In this study, the author constructed a test circuit comprising a PWM inverter, an induction motor, and grounding electrodes, and he studied measures to suppress common-mode currents by using shielded cables and a grounding system. He also studied a method for grounding the shielding of the shielded cables used for the power supply from the inverter to the motor suppressing common-mode currents.
In this paper, to design an EMI filter effectively, a method for insertion loss of an EMI filter connected to a semiconductor power converter is proposed. Conducted EMI noise that flows from the converter should conform to the regulations of an international commission, such as International Electrotechnical Commission (IEC). In order to conform to such regulations, EMI filters have to be connected to power converters. In general, the performance of the EMI filter is evaluated on the basis of the insertion loss of 50Ω measurement system. However, the impedance of the power converters is usually not set to 50Ω. As a result, the EMI filter design is often performed using a trial-and-error method because the noise reduction effect is different from the insertion loss. In this work, for simplicity, a power converter is considered to be a capacitor, instead of a stray capacitor. Then, a method for evaluating the insertion loss of an EMI filter connected to the power converter is proposed. This proposed method is employed using the 50Ω measurement system and the capacitance. The proposed method helps to design the EMI filter because the derived noise reduction effect corresponds to the experimental one.
To produce DC current by using a multiphase reversible chopper, smoothing reactors are needed. When the smoothing reactors are employed, the chopper devise becomes large and heavy if electromagnetic interference is avoided. The reduction in the ripple current by electromagnetic coupling contributes to making the chopper device smaller and lighter. We deduced the relationships among the amplitude of ripple current, duty factor, electromagnetic coupling coefficient. To determine the loss and gain, we introduced the ratio of the amplitude of ripple current in each phase and in total combined of multiphase chopper system to that of the ripple current in one-phase chopper, Aph, Asum respectively. This value indicates the reduction in not only the amplitude of ripple current but also self-inductance. The minimum value of the abovementioned ratio obtained analytically is accurately determined. We led the minimum values and obtained the range which implement to reduce the amplitude of ripple current both each phase and total combined. Finally, we applied an optimal electromagnetic coupling coefficient to the design of onboard reactors of electric railway vehicles.
Recently, the aging of worker and craftsmen is becoming a great issue because of low birthrate and longevity. Further, importing the knowledge of craftsmen to future generations is considered to be important. However, it is difficult to import such knowledge to many people at once. The “motion database” that realizes recording, searching, and reproduction of human motions is considered to be effective in overcoming this problem. In order to construct the motion database, modeling of human motions is needed. In this research, human motions are modeled the basis of a hidden Markov model, and a searching method based on the model is proposed. By using the modeling, it becomes possible to search for a motion in the motion database. This motion database can be applied for skill acquisition.
Redundant multi-degree-of-freedom (MDOF) bilateral system in workspace is expected to be a key technology for the development of next generation robots because of the variety of feasible tasks. Nowadays, four channel bilateral structures based on acceleration control have been introduced to realize both position and force tracking in a bilateral control system. Additionally, torque observers have been implemented to facilitate force feedback without the use of torque/force sensors. However, differences in controller composition between the joint space and workspace are still unclear. In particular, observer designs in both spaces are important for a realization of torque/force sensorless bilateral control. This paper presents a performance evaluation of an MDOF force sensorless bilateral system performed by considering the design space of observers by numerical and experimental analyses.
This paper presents a model-based feedforward compensation approach for the fast and precise positioning of a rotary table system with two drive actuators. In the system, since the interference force between the primary and slave actuators deteriorates the positioning performance in tables, the interference force as well as disturbance force is mathematically modeled to design a model-based feedforward compensation. The model can be adapted by an ordinary least-squares method to provide adaptive properties against disturbance variations. The effectiveness of the proposed approach has been verified by performing a series of numerical simulations and experiments with a prototype.
A fuel cell-EDLC hybrid power system with a multi-port bidirectional DC-DC converter has been recently proposed for extending lifetime of a fuel cell due to smoothing the output current of the fuel cell. This paper studies the performance of the hybrid power system when a fuel cell vehicle drives in the JC08 mode using a simulation model. The simulation results indicate that even if the load current fluctuates, the output current of the fuel cell could be maintained at almost constant values with an assist from the EDLC although small spikes are observed.