In order for the Okinawan economy to grow independently, creating new businesses is essential. This will require the cultivation of technologies to form the seeds of those businesses, as well as the training of technicians and researchers.
To promote the creation of new businesses and innovations that are “unique to Okinawa”, the Institute of Electrical Engineers of Japan set up a cooperative research committee for Okinawa-style robot-embedded/sustainable systems.
We proposed the concept of Okinawa-style robot-embedded systems. To realize this concept, we organized technical meetings and promoted research on this topic. At present, our research is focused on the development of ① integrated drone navigation and autonomous flight systems for aerial inspection and surveillance of infrastructure objects, ② K-Skill, ③ the applications to the agricultural sector of the Internet of Things (IoT), and ④ Okinawa-style applications of renewable energy. Our promotions are presently ongoing.
Okinawa has many islands, and the installation of photovoltaics (PVs) is accelerating. This paper focuses on the compensation of power fluctuation in PVs by the use of variable speed control of waterworks pumps for weak island grids. A simple model of a waterworks pump system is proposed to calculate power consumption, water flow and pressure from the power converter input frequency, and the efficacy of the model is verified by field tests. The model is based on hydraulics, and its constants fit the test results. Ramp response tests and PV power fluctuation compensation tests are conducted to evaluate the transient characteristics of power consumption control. The ramp response test results show that power consumption differs from its command value by a few seconds because of the pressure surge caused by the pipes. The latter tests show that control of power consumption compensates for most of the PV power fluctuation under the test conditions.
It is important that students practice experimental skills, and for this visualization of experimental skills and evaluation of achievement are necessary. The metrics of the experiment and curriculum of each college are specified to facilitate evaluation of the achievement of experimental skills, thus promoting effective technological education. It is possible to clarify the metrics and visualize student skills. Indicating the achievement and effect of student technical education will then make it possible to improve student skills. Here, we propose to use the experimental evaluation sheets and experimental skill sheet to clarify the metrics of the experiment and indicate the achievement level. The introduction of evaluation of experimental skills has educational effects. First, the features of the educational content have been presented. The metrics and objectives in the experiment of each technical college will be systematically collected. As a result, the content and operation of education will be clarified. We will then visualize the experimental skills of students. Toward this end, we formulated five-level evaluation criteria for the elements of experimental basis, theory, measurement, analysis and report. We evaluate the experimental skills using these criteria. As a result, the outcome is visualization, we can expect through which we expect the skills of the students to improve be able to guide more students. Finally, for improving education, the skills sheet will be linked to the review of the curriculum and educational improvement.
The NW (Needleman-Wunsch) algorithm is a method of sequence alignment in bioinformatics. The NW algorithm can be applied for global sequence alignment, which is a way of arranging the sequences of DNA to identify regions of similarity. However, the NW algorithm requires a huge number of calculations compared with the SW (Smith-Waterman) algorithm. Many studies have focused on analyzing the output of multiple sequences quickly in three dimensions. However, such methods cannot obtain similarities for whole sequences. In this article, we extend the NW algorithm to three dimensions. The proposed method is expected to provide a fast analysis of high precision data sequences.
IDS is used to detect virus patterns by packets in the network. The virus patterns are generally expressed as regular expression. The matching hardware for regular expressions has been extensively studied. However, the look-ahead and back referece approaches have not been studied very much. By using the matching method for the look-ahead pattern that has been already suggested, the matching result is added to memory. Therefore, the memory increases as look-ahead patterns increases. Moreover, the operating frequency becomes lower than that of conventional matching hardware. In this article, we propose an improved method of regular expression matching hardware for the look-ahead pattern. Using the proposed method, we show a decrese in memory and an improvement in the operating frequency.
Recently, the Y-00 protocol has been developed as a defense against cryptanalysis. The Y-00 protocol has a high affinity with existing public communication networks and has also been shown to achive a large-capacity transmission. In this article, we aim to improve Key DSR, which is part of the functionality of Y-00. We propose a new model of Key DSR, and a discussion of the efficiency of the new model is presented. Finally, we show that the proposed method can contribute to the composition of a safety design approach for Y-00 encryption.
In nearby special support schools, the practice of driving a motorized wheelchair using a joystick has been conducted for physically disabled children. However, physically disabled children require support and adjustment of the equipment corresponding to their disabilities because it is difficult to operate a joystick in a specific direction owing to their disabilities. In this study, we develop a joystick-type controller that can be automatically adjusted to the reaction angle suitable for the actual conditions of physically disabled children. Moreover, we conduct a quantitative evaluation of upper limb motion when operating the joystick-type controller that we developed to examine the effectiveness of the proposed method. The evaluation results confirm an effective improvement in the operability when the acquired reaction angle is suitable for the actual conditions of the user by the proposed method.
In this paper, we propose a smart security camera system for the automated detection of snatching incidents in crowds. Although half of all snatching incidents happened in the presence of other people and witnesses exist, this has not been considered in previous studies. Thus, SAMC (snatching action model in crowds) is presented in this paper for the automated detection of snatching incidents in crowded areas. Certain characteristics of motion are determined from video streams, and using a nonlinear support vector machine the system automatically classifies the situation of the video streams into criminal or non-criminal scenes. We consider many types of scenarios to perform experiments regarding snatching incidents in crowds. The experimental results show that the system can effectively detect snatching incidents with an accuracy of 96.87%.
This paper describes the development of a 3-D object recognition system of a flying drone system for emergency rescue and investigation. In this system, a neural network and new features for 3-D object recognition are key techniques for object recognition from a free viewpoint. Some appearance based characteristics are determined from captured images, and the system uses a neural network to automatically classify automobiles. The proposed system shows that several kinds of automobiles can be recognized from a bird's-eye view. Experimental results showed that the system can effectively recognize four kinds of vehicle objects with high accuracy.
In this paper, we propose an intelligent security camera system for the automated detection of snatching incidents on streets during the night. Although over a half of all snatching incidents occur at night, this has not been considered in previous studies. Thus, an intelligent security camera system using a deep neural network and SAM (snatching action model) is presented in this paper, for the automated detection of snatching incidents at night. Certain characteristics of motion are determined from video streams, and using a deep neural network the system automatically classifies the situations in the video streams into criminal or non-criminal scenes. We consider many types of scenarios to perform experiments regarding snatching incidents on streets at night. The experimental results show that the system can effectively detect snatching incidents with an accuracy of 96.66%.
In this paper, we propose an intelligent security camera system for automated detection of snatching incidents in which a bicycle is used. In addition, the effectiveness of the Basic Snatching Action Model (BSAM) and Gabor features for automated detection of snatching incidents is presented. The localization of moving objects in a video stream and human behavior estimation are the key techniques applied in the proposed system. Gabor features are determined from video streams and, using a majority rule network (MRN) composed of various artificial intelligence (AI) systems, the video streams are automatically classified into criminal or non-criminal scenes. In our experiments, we considered some scenarios of snatching incidents in which the perpetrator uses a bicycle. The experimental results show that the proposed system can effectively detect criminal scenes with high accuracy.
In this study, we developed a magnetic levitation system using a Hall element displacement sensor with neural network for science and technology education. The sensor configured with three Hall elements was devised in order to measure displacement from an electromagnet to a levitated object with a permanent magnet. Use of the Hall element displacement sensor achieves a lower-cost magnetic levitation system. Furthermore, three-layered feedforward neural network was utilized in order to improve the precision of the Hall element displacement sensor. Finally, operation verification of the developed magnetic levitation system was conducted by designing state feedback regulator with observer.
This paper describes the successful development of an integrated drone navigation system for aerial inspection and surveillance of infrastructure objects that features outbound and inbound GPS-based autonomous flight, machine learning of starting point and end point images of the destination structure, and a surface image gyro that detects images between the starting point and the end point. Traditional drone navigation research has focused on discrete autonomous flight technologies such as GPS navigation and non-GPS video SLAM. Thinking in terms of actual autonomous flights of drones, this study adopts a comprehensive approach that encompasses the entire trip to a destination from the departure of the drone up to its return.
In a DC power supply system with a constant power load (CPL) and LC filter, the input voltage may oscillate because of the interaction between the output impedance of the LC filter and input negative impedance of the CPL. This paper proposes a control method for the oscillation that uses a bidirectional DC-DC chopper and a power storage capacitor in order to reduce the energy loss for oscillation suppression. In the method, the four variables of voltages and currents in the LC filter and bidirectional DC-DC chopper are feedbacked to suppress the oscillation. To reduce the number of sensors, the minimum order state observer was adopted. The effectiveness of the proposed method was demonstrated in both simulations and experiments.
This paper presents an intensive discussion on a long-distance high-voltage direct-current (HVDC) transmission system that combines two modular multilevel cascade converters based on double-star chopper cells (MMCC-DSCC) with dc power cables. Hereinafter, a single MMCC-DSCC is referred to as a DSCC converter or just as a DSCC for the sake of simplicity. The HVDC transmission system is required to provide low-voltage-ride-through (LVRT) capability to enhance transmission system availability. This paper proposes a new LVRT method without any direct information exchange between the two DSCC converters. The validity of the method is verified, using simulated waveforms from the software package of “PSCAD/EMTDC” and experimental waveforms from a three-phase 200-V, 400-Vdc, 10-kW, 50-Hz downscaled HVDC system with a set of 300-meter-long dc power cables.
In general, a boost converter requires a high current because of applications such as HEVs. It is well known that the multiphase method is downsizing approach for a smoothing capacitor. Additionally, with the transformer-linked method, it is possible to miniaturize the inductor with high currents and realize a light weight and compact performance. The switching boost converter has three current modes: the continuous current mode, critical current mode, and discontinuous current mode. Moreover, the discontinuous current mode is the most complicated of all of the modes. For this reason, the control design is carried out to avoid the discontinuous current mode. However the discontinuous current mode is unavoidable when the load rapidly changes. In this paper, the discontinuous current mode in a two-phase boost chopper circuit with a transformer-linked inductor is analyzed. In addition, we carry out a comparative study of the proposed circuit and conventional circuits.
In a previous paper, we developed a new magnet-free motor that has concentrated stator windings and rotor coils with a pair of diodes. The advantage of this motor is that rotor currents can be generated by utilizing changes in the magnetic fields. However, sufficient rotor currents and torque cannot be generated at low speeds, because the rate of change in the magnetic fields becomes too small. Therefore, we developed a method to amplify the rotor currents and torque at low speeds. This method increases the changes in the magnetic field by intentionally superimposing time harmonics over the stator currents. A prototype motor was designed and fabricated, and the method was applied to the motor. This paper presents a mechanism for inducing currents in the rotor coils using the changes in the time harmonics of the stator currents. Using experimental data, we evaluate the increase in torque at low speeds.
This paper discusses the influences of common source inductance in power converter circuits. Common source inductance is the source-side inductance inside a power module, and it shares common circuit parameters with both the gate drive and power circuit. Therefore, common source inductance will influence the switching characteristics of the module. No paper has yet addressed the relationship between common source inductance and switching characteristics such as surge voltage and switching loss. In order to improve the switching characteristics during turn-off operations, this paper presents a design procedure with respect to common source inductance. In addition, experimental results rated at 500V, 40A are shown.
In a previous study, we obtained the general solution for resonant inductive coupling by mixing factors of eigenstates, and we derived power transmission and power reception formulas for inductive coupling coils. Numerical calculation results in the time and frequency domains always satisfy energy conservation requirements. We thus obtained a number of interesting results. However the expression of the general solution is too complicated to predict the behavior of the solution. Therefore, in this study, we will obtain an understandable expression of the general solution by restricting mixing factors to real numbers. This restriction is identical to the “Homologous Time Constants” condition, which states that time constants of the primary circuit and secondary circuit must be equal.
Magnetic resonant coupling is one of the conditions for electromagnetic induction using a circuit topology. On the other hand, the relation between the main magnetic flux and the near magnetic field has not been sufficiently discussed in the discussion of the circuit topology, even though the main magnetic flux is used for energy transfer in wireless power transfer. The full explanation of the contribution of the main magnetic flux was not proposed with regard to a comparison between the magnetic resonant coupling and the other topologies. Therefore, in this paper, a series of explanations from the main magnetic flux to circuit topologies is presented, and the mechanism of magnetic resonant coupling is proposed with regard to circuit theory and electromagnetism. The proposed theory is validated through an electromagnetic field analysis and experiment.
This paper proposes a new and simple torque-sensorless torque control method for permanent-magnet synchronous motors (PMSMs) with nonsinusoidal Back EMF. The method suppresses the sixth and/or 12th harmonic torque ripples caused by the back EMF in a feedforward manner even at high speeds; it consists of two subordinate methods for compensation command generation and command-tracking current control. The first subordinate method generates compensation current commands to cancel the torque ripples based on a mathematical model of PMSMs. The second controls the stator current to track a current command containing both fundamental and compensatory components. In conjunction with the current control, a dedicated disturbance observer that employs a digital speed-varying band-pass filter as a disturbance filter is also proposed. The effectiveness and usefulness of the proposed method were verified through extensive experiments.
Our research focuses on the control of various mechatronics systems. The walking robot with bi-articular muscles, electric tiller and electric ship are useful for our future life. For development of these mechatronic systems, our laboratory proposes the control methods and mechanical structures.