We have been studying a wearable sensor network composed of an original event-driven sensing system and multiple sensors for human motion detection. To detect human behaviors in detail, multi-point detection with high time resolution and suppression of data congestion is required. For achieving such a sensing system, this paper proposes a PID-type (Proportional-Integral-Derivative) data volume control function that variably increases and decreases data volume of each sensor node in response to large motions, continuous motions, and sudden motions of human. Basic verification using a loading stage and application verification using a wearable sensor glove showed that the sum of proportional, integral, and derivative values of sensor data changes in response to large motion, continuous motion, and sudden motion, and that the date volume changes during sensing. The effectiveness of the PID-type data volume control function was demonstrated.
ABSTRACT This paper attempted to relate muscle fatigue, muscle action potential (EMG: Electromyogram), metabolic activity generated in the body, and vital signs such as respiration and heart rate by using a Bayesian network (BN), considering that they are caused by interrelated stochastic transitions. The BN was constructed based on EMG, heart rate, respiratory rate, and subjective muscle fatigue obtained from four male subjects in their 20s who performed three sets of arm curl‐like exercises for 4, 5, and 6 kg loads, respectively. As a result of providing each node of the constructed BN with known evidence, the posterior probability in the node representing subjective muscle fatigue changed as expected. Thus, the results suggest that the BN can represent the relationship between biologically relevant signals and muscle fatigue, including uncertainty. Modeling with this method has the potential to estimate muscle fatigue without requiring expertise in EMG interpretation.
ABSTRACT This study examines an optimal operation model for a smart grid composed of multiple microgrids to promote renewable energy use in Japan. In Japan, about 70% of electricity is still supplied by fossil fuel power, while renewables account for only 18% despite a 36%–38% target for 2030. Using demand and photovoltaic data from Setagaya Ward, we construct a system model with factory/office and residential microgrids and formulate a mathematical optimization model that considers power interchange, batteries, and heat storage. Numerical experiments based on several case studies show the effectiveness of smart grid operation designed according to the proposed model in promoting renewable energy utilization and reducing total generation cost. In particular, the results show that increasing photovoltaic capacity, increasing the number of microgrids, and considering heat demand are all effective measures. However, these benefits depend on the season. Future work should extend the system model to account for seasonal variability and associated investment costs.
ABSTRACT A feedback control system containing non‐linearity can have plural steady states. One of the steady states must be the desired steady state, and the others can be undesired one. In this paper, the steady state analysis of the proposed feedback phase control system for antenna beamforming is described. The analysis shows that there are three groups of equilibrium points. One of them is a group of the desired steady state points, and the others are groups of unstable equilibrium points. An unstable equilibrium point is like a ball on a hilltop, and a small stimulus drops the ball down. The feedback control system is for radio receivers, and thermal noise takes a roll of the small stimulus. Therefore, the system cannot stay at the unstable equilibrium point and moves to the desired steady state.
This paper addresses the short battery lifespan of wireless mouse rings by introducing the picoRing mouse. We develop a near-field sensitive inductive telemetry, which allows a ring coil to send its data to a nearby wristband coil in an ultra-low-power way. This approach drastically extends the ring's operation time from a few hours to over 200 h on a 27 mAh battery.
