Published papers

This paper proposes a service-oriented network architecture for next-generation power grids, i.e., smart grids. The proposed architecture includes Ethernet passive optical network (EPON)-based optical access systems and service-oriented routers (SoRs). The SoR function is embedded into any communication nodes for capturing, filtering, storing, selecting, calculating, and redirecting requests in network traffic. The maximum throughput of the developed SoR is 1.12 Gbps, and the size of its packet buffer is approximately 100 MB. To confirm the feasibility of the proposed service-oriented architecture for smart grid communications, the performance of a power grid model is evaluated using MATLAB/Simulink and SimPowerSystems Toolbox. © 2013 IEEE.

© 2017 ACM. Owing to the introduction of an energy-monitoring device called the "smart meter," a large amount of power-demand information regarding private houses is being stored around the world through the development of smart grids. Such electric consumption data include a variety of features related to the structure of the customer's home, as well as their family structure and lifestyle. To capture the meaningful features from the power-demand information, a proper extraction method should be considered such as a discrete Fourier transform (DFT) or discrete cosine transform (DCT). This paper proposes the use of two frequency analysis methods, i.e., DFT and DCT, toward power-demand information. The converted power-demand information is transformed using three expression methods. A power-demand dataset was gathered from more than 100 houses in Yokohama, Japan, over a two-year period. The numbers of feature values in these three expression methods were compared by estimating the floor space of each customer's house with two support vector classification (SVC) values using both linear and RBF kernels. As a result, the proposed expression method performed better than the other two feature expression methods. The mean accuracy of this expression method is better than the other two by 20%, and the highest level of accuracy in terms of the floor-space estimation is greater than 95% when using liner SVC (L2-SVC). The accuracy shows a distribution of 50% to 100% regardless of the number of selected frequencies transformed using a DFT and DCT.

In recent years, the number of IoT devices has been rapidly increasing. Therefore, MQ Telemetry Transport (MQTT) has attracted attention as a lightweight protocol for IoT devices. MQTT employs a publish/subscribe model of communication via a broker, and since the performance of the MQTT broker directly affects the quality of service, various studies have been conducted to improve its performance. Among them, the hardware implementation of MQTT broker has higher performance than software implementations in terms of publish throughput and processing delay. However, there are some problems such as inflexibility and resource limitations. Therefore, we propose a distributed MQTT brokers infrastructure using the hardware broker. In this architecture, the software broker on the cloud and the hardware broker at the edge region work in cooperation to achieve low latency processing at the edge region and software flexibility. The hardware broker operates network transparently, so that end devices communicate with the software broker in the cloud and do not need to be aware of the presence of the hardware broker at the edge region. This enables resource and processing load distribution without affecting end devices. We implemented the network transparent hardware broker in a field-programmable gate array (FPGA) and evaluated it.

In recent years, there has been an increase in the demand for three-dimensional data of geospatial information in various fields, such as automatic driving and disaster prevention. Beyond5G (above 5th generation network), which features wideband, low latency, reliable connection, allows for the easily collection of spatial information of many points and times from camera-equipped vehicles, such as self-driving cars and drones. Spatiotemporal information at any location and at any time can be provided depending on users' requests. However, there are instances where the target point's spatiotemporal information and the request's target time have not been collected. Therefore, appropriate data completion is required to provide this service seamlessly. To create 3D models using photogrammetry, images are required; therefore, multiple videos that captured the streets near our university were prepared and split into frames. Then, those images were stored in our local storage. The information of the recording date, weather, file path to the image, and location (latitude and longitude) were saved to our database per frame. When users request spatiotemporal information, this system commences searching for images that meet the requirements. When the number of matched images are sufficient, the 3D model is created. When it is insufficient, the data are complemented appropriately.

In recent years, there has been an increasing demand for accurate measurement of the spatial dispersion of air temperature in air conditioning control for indoor environments. This spatial dispersion of temperature is caused by the unevenness of air conditioning equipment, local temperature gradients due to human activities, and local heat exchange with outdoor air, all of which hinder the provision of a comfortable environment. This issue requires resolution in various fields, including the agricultural sector, where it can negatively impact crop growth. To address this issue, it is necessary to measure air temperature at multiple points, although the number of sensors that can be installed is typically limited, and the temperature at a single point is typically used as a representation of the temperature in the space. Additionally, heat maps using infrared array sensors can acquire temperature distribution in a narrow area; however, they cannot directly determine air temperature as they only measure the surface temperature of an object. Therefore, we propose a deep learning-based method that utilizes both heat maps acquired from infrared array sensors and air temperature data obtained from environmental sensors to estimate air temperature. We evaluate its effectiveness by varying the experimental environment, the model structure, and the resolution and number of heat maps added as input. Furthermore, we assess the usefulness of utilizing a Graphics Processing Unit (GPU), which is a cost-effective solution that can be installed on low-resolution sensors and edge devices. The outcomes indicate that the proposed model can attain an estimation accuracy of under 1 mean squared error (MSE) in approximately 200 seconds, while also exhibiting practical feasibility for deployment on edge devices, including residential abodes and agricultural premises.

The purpose of this study is to control multiple mobile robots in formation considering the ability of a robot using the "Leader-Following" strategy. There are three features of this study. First, a performance index that shows mobile robot ability is quantified. Specifically, maximum acceleration and maximum velocity of a robot are defined by maximum admissible rotation and maximum continuous torque of a motor. The performance index is quantified from arrival time on the destination using these parameters. Second, a new controller is proposed based on the performance index, so that robots can be controlled according to robot ability. Third, a compliance controller using a virtual repulsion is suggested in this paper, so that each robot can avoid collision. Finally, simulation and experiments are done in a real-time system using RT-Messenger. RT-Messenger allows robots to transmit information regarding their positions to each other in real time. These results shows the validity of the proposed method. © 2004 IEEE.

Perfect classified channel (PCC) was proposed as a hardware-based Layer-1 encryption system that prevents of leakage of packet information and any indication of the existence of packets. PCC can provide high-throughput communication, which is encrypted using AES encryption hardware, while maintaining DC balancing, which is generally managed using the 8B/10B or 64B/66B coding algorithms. In this paper, we propose two methods to classify a framing signal that indicates a boundary between packets, for PCC. These methods facilitate an improved level of security compared with existing communication channels and make PCC more secure. This paper describes the details of the PCC architecture including the hardware costs while also verifying the DC-balance performance of PCC and the confidentiality of framing signals. © 2013 Institute of Electrical Engineers of Japan.

A novel cache-based network processor (NP) architecture that can catch up with next generation 100-Gbps packet-processing throughput by exploiting a nature of network traffic is proposed, and the prototype is evaluated with real network traffic traces. This architecture consists of several small processing units (PUs) and a bit-stream manipulation hardware called a burst-stream path (BSP) that has a special cache mechanism called a process-learning cache (PLC) and a cache-miss handler (CMH). The PLC memorizes a packet-processing method with all table-lookup results, and applies it to subsequent packets that have the same information in their header. To avoid packet-processing blocking, the CMH handles cache-miss packets while registration processing is performed at the PLC. The combination of the PLC and CMH enables most packets to skip the execution at the PUs, which dissipate huge power in conventional NPs. We evaluated an FPGA-based prototype with real core network traffic traces of a WIDE backbone router. From the experimental results, we observed a special case where the packet of minimum size appeared in large quantities, and the cache-based NP was able to achieve 100 throughput with only the 10-throughput PUs due to the existence of very high temporal locality of network traffic. From the whole results, the cache-based NP would be able to achieve 100-Gbps throughput by using 10- to 40-Gbps throughput PUs. The power consumption of the cache-based NP, which consists of 40-Gbps throughput PUs, is estimated to be only 44.7 that of a conventional NP. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.

© 2015 The Authors. Published by Elsevier Ltd. In order to enhance electricity conservation in households, detecting which electric appliances consume high electricity is effective. However, collecting every data of electric appliances needs many devices and it would be high costs. Therefore, data disaggregation from total data to each appliance leads to the reduction of cost and electricity. This paper presents how to disaggregate the consumption of electric appliances from total electricity consumption. In order to disaggregate electricity consumption of electric appliances from total energy consumption, sparse coding has been implemented. However, changes in the use of electric appliances are difficult to express in this method. Therefore, we propose a novel sparse coding method, named, "0-1 sparse coding" to disaggregate which electric appliances were used in the total consumption of electricity. In order to collected sample data for analyzing the methods, we installed smart metering systems in two households. The system collects the data of total electricity consumption and data in the main electric appliances in every 5-minutes. We evaluate two methods, 1) our proposed method, and 2) discriminative sparse coding method. From the results, our proposed method increased the accuracy about 44.8% than the previous method.

Minimally invasive surgery is an important issue from the point of view of patients' Quality of Life (QoL). An endoscopic surgery is one of the minimally invasive surgeries. With the endoscopic surgery, pain could be less. This operation, however, has difficulty, and surgeons have to be well trained. To solve this problem, an endoscopic surgery system based on haptic teleoperation was proposed. The characteristic of the system is position and force information is transmitted bilaterally between master and slave robots. This means that a teleoperation with haptic information can be achieved, and surgeons can perform a telesurgery safely and smoothly. The system, however, does not have enough degrees of freedom for an actual operation. In this paper, a multi degrees of freedom endoscopic robotic system is proposed. This system has 6 degrees of freedom on each master and slave robot. A haptic control system implemented in the proposed system is based on acceleration control. Due to control in acceleration dimension, robust and ideal position and force control are able to be attained simultaneously. The control system requires a short sampling period for attainment of wide bandwidth to transmit keen force sensation. To ensure the short sampling period in a multi degrees of freedom system, this paper proposes the multi degrees of freedom tele-robotic system utilizing FPGA as a controller. Finally the validity of the proposed system is shown by experimental results. ©2007 IEEE.

Technology for teleoperation has been needed in many scenes. Especially in robotic surgery, It is required that to transmit the tactile sensation to the operator. To attain that need, teleoperation method called bilateral has developed. Bilateral means transmit information each other. Environmental information is transmitted both from master to slave and from slave to master in bilateral teleoperation. In bilateral teleoperation, environmental information of master and slave should be exchanged in common coordinates. It is difficult to define a common coordinates in different structured bilateral teleoperation. Mode based control for bilateral teleoperation is proposed in this paper. Coordinates based on geometric mode is used to common coordinates to exchange the environmental information between master robot and slave robot. Geometric environmental mode is quarried by quarry matrix and hypothetical axes bilateral controller based on acceleration control is applied to hypothetical mode motors. Hypothetical mode master motor and mode slave motor are transformed to mode common motor and mode differential motor. Force servo controller is applied to mode common motor and position regulator is applied to mode differential motor. Viability of proposed method is shown in experimental result. ©2005 IEEE.

Dynamic microgrid was proposed in our laboratory in order to utilize distributed power sources effectively. It means that structure of microgrid is varying according to demand fluctuation. To realize the dynamic microgrid, it is indispensable to obtain both energy demand and supply and keeps balance them by using ICT based sensor network. KNIVES (Keio University Network oriented Intelligent and Versatile Energy saving System) is an ICT based supply and demand side management system that supports distributed and cooperative power control. In this study, KNIVES is introduced to actual consumers such as care facility, school and store as a platform of dynamic microgrid. Topology of the microgrid is changeable dynamically, and it is determined to conduct optimized calculation by referring energy consumption data and targeted value set measured from individual groups. This paper describes construction method of the dynamic microgrid and evaluation of feasibility and availability from a standpoint of calculation cost. © 2010 IEEE.

To deal with environmental problems such as global warming and depletion of energy resources, energy conservation measures in the civilian sector and the spread of renewable energy are required strongly. As a next-generation energy system to achieve them, Cluster Energy Management System (CEMS) is beginning to be studied in Japan. CEMS is the energy management system, which cooperates with various dispersed power sources and buildings using information technology. CEMS monitors and adjusts energy supply and demand in real-time to form the best combination of them, and achieves high efficiency energy usage. In this study, the electricity energy measurement system using KNIVES (Keio University Network oriented Intelligent and Versatile Energy saving System) was build in Keio University Shonan Fujisawa Campus (SFC). In addition, it is declared that this system can predict electric power demand based on the past data obtained from itself. © 2010 IEEE.

© 2014 IEEE. Increasing carbon dioxide emissions have given rise to global warming. Therefore, the need to reduce these emissions is being widely discussed. Decreasing energy consumption by efficient energy use is required to directly influence carbon dioxide emissions. Recently, energy consumption in the civilian sector is rising in Japan. To address this problem, the introduction of a Home Energy Management System (HEMS) is effective because it enables the control of power consumption and an economical energy use. Controlled heating, ventilation, and air conditioning (HVAC) is an essential function to be implemented in HEMS. HVAC control systems are now commercial and several HEMS experiments with HVAC control have been conducted in Japan. However, only few experiments have been conducted in cold districts because peak energy consumption predominantly occurs in summer. Nevertheless, from a carbon dioxide emissions reduction viewpoint, in such districts, the use of kerosene fan heaters, which are popular, becomes a dominant source of emissions around the year, but particularly in winter. In this study, we constructed a HEMS at 16 houses in a cold district, with the collecting function of environmental conditions, heating appliances status, the amount electric/oil energy consumption, and with the control function of HVAC systems. In particular, specially designed fully-controlled and monitored kerosene fan heaters are introduced. To confirm the effectiveness of the proposed HEMS, an energy saving experiment was conducted in which the use of kerosene fan heaters was controlled on the basis of the acquired environmental information, without degrading the room comfort. A reduction in carbon dioxide emissions was monitored along with the comfort level. This is the first experiment which integrates kerosene fan heaters into HEMS. This study demonstrated the ability of autonomous heater control to reduce the burden of residents and the usefulness of HEMS in Japan's cold district.

KNIVES is a system for providing balanced power supply and effective demand control. This system controls the power of electric devices over the Internet, due to reduce total power consumption. For the control, KNIVES also considers indoor environmental affinity by using environmental sensors. In this paper, CO2 sensor is implemented on KNIVES terminal and it enables to measure CO2 concentration for assessing indoor vitiation. This paper verifies the effectiveness of this sensor by estimating the number of people. Also, the number of people is one of the parameter for effective control. Existing estimating method for counting the number of people, however, is difficult to install in a existing building. This paper describes the new estimating method for the number of people by CO2 concentration. As a result, this method can accomplish accurate measurement, and it can be applied to various applications for a future demand control. ©2008 IEEE.

© 2016 IEEE. Wireless sensor networks (WSNs) are implemented in various Internet-of-Things applications such as energy management systems. As the applications may involve personal information, they must be protected from attackers attempting to read information or control network devices. Research on WSN security is essential to protect WSNs from attacks. Studies in such research domains propose solutions against the attacks. However, they focus mainly on the security measures rather than on their ease in implementation in WSNs. In this paper, we propose a coordination middleware that provides an environment for constructing updatable WSNs for security. The middleware is based on LINC, a rule-based coordination middleware. The proposed approach allows the development of WSNs and attaches or detaches security modules when required. We implemented three security modules on LINC and on a real network, as case studies. Moreover, we evaluated the implementation costs while comparing the case studies.

© 2014 IEEE. Heating, ventilation, and air conditioning (HVAC) are important factors for a building energy management system (BEMS). Efficient control of the air conditioning (AC) is required to maintain both energy efficiency and human comfort. However, AC control systems are expensive to install in buildings. In this study, a cost-effective AC control system intended for a library is proposed; it is also applicable to other facilities such as offices and meeting spaces. This system uses seating sensors for maintaining both energy efficiency and human comfort. Conventional AC control systems generally use expensive motion sensors or vision sensors as well as temperature and humidity sensors to acquire information on both the location and the comfort of users and to provide location-based control to users. In order to reduce sensor-based cost, the proposed system uses low-cost pressure sensors and maintains both energy efficiency and the comfort level. For detecting seat occupancy and locations, low-cost pressure sensors and low-power communication nodes are attached to chairs and they transmit seating data to the database of a server. A programmable logic controller is used to control the proposed AC system according to the information stored in the database. The system is evaluated using a 10-day experiment conducted at a library in Kurihara City in Miyagi prefecture of Japan. The results of energy efficiency evaluation in this experiment show that the proposed system can reduce electricity consumption by 18.3%. Through measurement of the predicted mean vote values of users of the library, the proposed system is found to be capable of maintaining user comfort.

Energy consumption is continuing to increase, especially the consumption of fossil fuels. It is important, therefore, to make use of our limited energy sources and reduce carbon dioxide emission. Some natural energy resources, such as solar power, have been well studied; however, they require complex systems and introduce energy fluctuations. On the other hand, demand side management (DSM) can also be studied from the consumer's point of view. One of the challenges associated with DSM is reducing the energy consumption of pumps in commercial buildings. Although water cycling systems have been well studied by large water departments, the knowledge is not generally used in most commercial facilities. Therefore, this study aims to control a water circulation pump to reduce energy consumption while maintaining water quality. This approach is applicable to buildings with pools or hot springs that are expensive to operate and maintain. Automation of water circulation systems has been well studied only by water departments. However, general water purification systems can be expensive and are highly complex. For these reasons, this paper constructs a low-cost automatic water management system to reduce management costs. An experiment was conducted to demonstrate an automatic water management system that will effectively cut water management costs using low-cost sensors. We also experimentally obtained some parameters to facilitate automatic water management. Finally, the experimental system was found to reduce electricity consumption by 8%/day and reduce the electric peak by 30%. © 2013 IEEE.

The design reuse methodology, which has been developed at the VCDS Project, is a SoC design methodology to reduce the SoC design time using high level design intellectual properties named as Virtual Cores (VCores). In this paper, we propose the VCore based design methodology to synthesize the SoC architecture from the system level specification. This synthesis methodology generates an initial architecture that consists of a CPU, buses, I/Os peripherals, and RTOS (Real Time Operating System), and makes tradeoffs between hardware and software on assigned software VCores and hardware VCores models to the architecture. The results of an architecture level design experiment using the proposed methodology shows that the partial automation of the communication refinement process, allied with design reuse, accelerates the architecture synthesis, thus reducing the design time required to design an architecture.