The authors have proposed Vapor Pressure Deficit (VPD) control methods for a solar-light-type plant factory (greenhouse) with a fog-cooling system. In particular, a proportional feedback controller with a variable gain is adopted in an actual system. In the system, however, there is some dead time—was experimentally confirmed by vision-based observation—which brings vibration to the value of VPD. This paper proposes a VPD control considering the dead time of the fog generation by using a communication disturbance observer with a high pass filter (HPF-CDOB). The stability of the whole control system is verified by the small gain theorem. The effectiveness of the proposed control method was demonstrated via experiments. In the experimental result during the high-temperature phase, the proposed method achieves a 81% reduction of the average error and a 20% reduction of the standard deviation in comparison with the conventional method.

A necessary and sufficient condition for linear time-varying (LTV) systems to be exponentially stable has been given based on differential Lyapunov inequalities (DLIs). The exponential stability of an LTV system is guaranteed if the DLI for the system has a solution, however, few systematic methods have been reported for finding a solution of DLIs. We focus on a class of periodic LTV systems and propose a sufficient condition to find solutions of DLIs for the class by using linear matrix inequalities (LMIs). Some examples show the effectiveness of the proposed analysis method.

Vibration power generation utilizing environmental vibrations to generate electricity has been attracting attention as a sustainable independent power source for such as wireless sensors placed under vibration. For efficient power generation, the resonant frequency of the vibration power generation device must be automatically adjusted to the environmental vibrations. To achieve it, the author's group proposes a method of installing a variable capacitance in the device and adjusting its capacitance by extremum seeking control. In the case of damped vibration applied, even if the amplitude and frequency of the vibration vary randomly if their distributions can be regarded as stationary and identical, an effective extremum seeking control method and its effectiveness are demonstrated using experiments.

In this paper, we propose a TOF-based high-resolution ranging method for asynchronous nodes in wireless sensor networks. Localization of sensor nodes is often required in wireless sensor networks to utilize measured data. TOF-based localization method is considered to be desirable since TOF of RF signal is hardly affected by surrounding conditions and no additional hardware is necessary. However, it is difficult to measure TOF with enough resolution because the speed of RF signal is too fast. Although measurement resolution can be improved by operating measurement devise with high frequency clock, it is not practical since high frequency operation leads to high power consumption and high cost. In previous research, high resolution measurement method using vernier effect, which is the principle of vernier caliper, has been proposed so that enough resolution can be achieved even when using low frequency clock. As a problem of the method, however, transmitting clock and receiving clock can't be isolated because they are assumed to be synchronized. If these clocks are put on same node, round-trip TOF has to be measured instead of one-way TOF. In that case, however, there are several problems such as uncertainty of reflecting time and self-interference, which makes it difficult to put the method to practical use. Then, we improve the method to realize TOF measurement between asynchronous nodes. When asynchronous clocks are used, measurement result is affected by phase difference and period difference. Main works of this research are formulating measurement error due to those asynchronous differences and proposing a way to negate the error. In addition, some experiments have been conducted to verify the proposed method. As a result of the experiments, it is confirmed that high-resolution TOF measurement between isolated nodes can be realized.

Autonomous robots are expected to perform minute tasks that require skill for humans. In order for robots to achieve autonomous tasks, multiple sensory information processing and feedback strategies are indispensable. This study focuses on eggshell cutting task strategy that supports the exposure of eggshell membranes by a robot that handles micro drill. We propose the task strategy that robot performs discrete and continuous cutting on eggshell and the failure detection when the eggshell membrane is damaged. Finally, we show the experimental results of the autonomous eggshell cutting tasks by robot and the human-assisted eggshell peeling and eggshell membrane exposure. Besides, we consider when to stop the cutting task so as not to break the eggshell membrane.

I surveyed of the actual conditions of robot users' cleaning for their robots for proposing a cleaning method that can be continued daily. As a result, I confirmed that it is important for manufacturers to provide a cleaning method.