Present study aims to develop a high-speed photoelasticity with a high-speed polarization camera for evaluating the stress loading on a pressure-sensitive gel by fingertip movements. Prior to this, normal stress loading and phase retardation field on the pressure-sensitive gel were measured with the calibration experiment system combining a stress loading device and the high-speed photoelasticity. The stress-optic coefficient indicating the performance of pressure-sensitive gels was calculated from the data. For the calculation of stress-optic coefficient, we performed the phase unwrapping process to remove the effect of phase wrapping on the visualization data of phase retardation field. It was experimentally confirmed that the trend in the stress-optic law was satisfied. In addition, the temporal evolution of shear stress loading by fingertip movement such as rubbing and tapping on the pressure-sensitive gel was also visualized by the high-speed photoelasticity. As a result, it was suggested that our method has a high degree of accuracy, enabling to measure slight time variation of shear stress at a level too small to be recognized by the subject performing the fingertip movements.

Autonomous flight control systems have become an important technology for safety flight. The control problem of autonomous flight aircraft is challenging due to the nonlinearity and uncertain disturbances such as the external forces generated by the air flow. Model predictive control is a kind of optimal feedback control in which the control performance over a finite future is optimized and its performance index has a moving initial time. The objective of this study is to propose an Nonlinear Model Predictive Control with Disturbance Estimation for Aircraft under Unknown Disturbances using Steering Angle Manipulation. The effectiveness of the proposed method is verified by numerical simulations.

Model-Based Development (MBD) has been widely adopted as an efficient product development methodology in the industrial world. A hierarchical-type control structure has been proposed as the control system architecture for products developed through MBD. In this control system, a compensator is introduced to mitigate the degradation of control performance caused by disturbances and model errors present in actual plants. This paper proposes a compensator design method based on Generalized Minimum Variance Control (GMVC). The proposed method is designed to suppress the influence of equation errors in the plant, which are represented by the CARIMA model. Additionally, the nominalization characteristics of the proposed method are discussed. The effectiveness of the proposed method is verified through numerical simulations, and its practicality is demonstrated through experiments using a slider-crank system applying the hierarchical-type control structure incorporating the proposed compensator.

An air suspension is one of the fundamental components of a vibration isolator that utilizes a stiffness caused by compressibility of air and damping effect caused by viscosity of air. In this study, we propose a method for estimating mass, center of gravity and moment of inertia of a supported object on the vibration isolator using state quantities of air suspensions and validate the proposed method by experiments. Previous research has shown that to obtain optimal vibration characteristics in a multi-degree-of-freedom vibration isolator supported by multiple air suspensions, it is necessary to set the damping coefficient of each air suspension according to the moment of inertia around a horizontal axis passing through the center of gravity. Therefore, it is necessary to estimate the characteristics of the supported object to derive and set the optimum damping coefficient, which varies according to them. The mass and the center of gravity can be estimated from static condition of the air suspensions. The moment of inertia can be estimated from the natural frequency of the vibration system. However, the damping coefficient of the vibration isolator is generally large since its vibration isolation characteristics should be optimize. For this reason, it is difficult to measure the natural frequency from the transient response of the supported object on the vibration isolator. Therefore, in this study, targeting a 2-DOF system, which is the simplest structure in which the moment of inertia affects the vibration characteristics, we clarify a method to estimate the moment of inertia using air suspensions, which can reduce the damping coefficient as much as possible only when estimating the characteristics of the supported object, and verify the method through experiments. The experimental results showed that the estimation error of the mass is 4% at maximum and the center of gravity is 3% at maximum. The estimation error of the moment of inertia is 24% at maximum regardless of the center of gravity of the supported object.

This study presentsan advanced mathematical model for predicting the in-plane natural frequencies of circular rings with rectangular cross-sections, a critical factor in vibration control. Building on Hoppe’s predictive formula for in-plane vibrations of rings, which has been extensively applied in fields such as mechanical and structural engineering, the proposed model integrates curved beam theory with experimental validation to enhance accuracy. The research compares the proposed model with conventional methods designed for thin-walled and thick-walled rings. Relative errors between theoretical predictions and FEM simulations are quantified. For both thin-walled and thick-walled rings, relative errors in natural frequency predictions increase as the mode number and the ratio of wall thickness to ring radius increase. Across different mode numbers and thickness-to-radius ratios, the conventional methods exhibited relative errors of 10% to 40%, depending on the specific parameters. The proposed model, based on curved beam theory, demonstrated an improvement in accuracy, predicting in-plane natural frequencies with a relative error of approximately 5% for a wall thickness of about 20% of the metal ring’s radius. This advancement provides a more reliable method for predicting the in-plane vibrations of circular rings, crucial for addressing engineering challenges across multiple disciplines.

In high-rise buildings, elevator ropes, which are flexible long objects, continue to vibrate with very large amplitude for a long period of time during an earthquake. The elevator cannot be restarted unless this vibration is reduced. However, it is difficult to determine the amplitude in a dark and long elevator shaft, and it is necessary to wait a long time, which is empirically sufficient. Thus, this study provides a real-time estimation of the elevator rope vibration. In previous research, real-time estimation is performed by installing multiple sensors in the elevator shaft. In contrast, this paper proposes the estimation method by a sensor installed near the traction sheave in the machine room. The sensor obtains real-time information about the angle near the end of the rope. The information is passed through a bandpass filter that passes only each natural frequency component of the elevator rope, and the shape of the rope is estimated. The method does not require a detailed model of the elevator rope, but the natural frequencies and the length of the rope. The proposed method can estimate the lateral vibration of a 200 m long rope excited by an earthquake with an error of only about 10%.

This paper proposes a method to monitor cutting force with high accuracy by combining multiple sensor signals based on a model approach. The cutting force cannot be accurately monitored by using only acceleration sensors mounted on the tool spindle because the static displacement of the tool spindle is not measured effectively. Thus, the proposed monitoring method effectively uses information on table motion to estimate the spindle's static displacement. Specifically, the relative table displacement is defined as the relative displacement between the motor encoder and the linear scale reads, from which the estimated cutting force is calculated for estimating the static displacement. Based on this, the method monitors the cutting force more accurately from the model on the tool spindle stiffness. The proposed method was evaluated in milling with the changes of cutting loads and directions. As a result, we achieved high accuracy in cutting force monitoring in milling with end mills. The experimental results confirmed that it is possible to improve the accuracy of cutting condition monitoring by using the encoder signals on the work table.

The purpose of this study was to develop a virtual space acoustic system to identify the sound source localization ability specific to blind soccer players. Using stereophonic technology, the sound source can be generated at an arbitrary position in the virtual space, and a virtual space acoustic system was developed to simulate the acoustic experience on a blind soccer court by simply putting on headphones. Comparison between the system and a real space showed that the spatial resolution of the sound sources that can be reproduced by the system is approximately-0.120 m<x<0.124 m for the front-back component and -0.103 m<y<0.118 m for the left-right component. The system can also be used to simulate the voice of a blind soccer player. Using this system, we measured the sound source localization ability specific to blind soccer players. In the single-task test, the correct response rate was 67.4 % for the experienced players and 57.9 % for the inexperienced players, indicating that the experienced players had a significantly higher correct response rate. In addition, the experienced group had significantly higher percentages of correct responses for all sound sources in the double- and triple-task examinations. The percentage of correct responses decreased significantly with each additional task for the inexperienced participants, while there was no significant difference between the single and double tasks for the experienced participants. Therefore, sound source localization ability for multiple sound sources is considered to be important in blind soccer. The VR acoustic system we have developed allows users to visualize areas of difficulty, such as sound source type, distance, and direction, and to train sound source localization skills appropriate to the individual.

The relaxation strength Δε_m (m: dielectric relaxation number) regarding heparin volume in blood has been extracted by relaxation time distribution (RTD) analysis implementing in electrical impedance spectroscopy (EIS) for the online and non-invasive monitoring of heparin volume in blood extracorporeal circulation. Extracorporeal circulation experiment was performed under conditions where heparin volume in blood varied over time due to metabolism and heparin administration. By applying the RTD analysis with m as an unknown parameter, the Δε_m were extracted from dielectric spectra of circulating blood which were measured by an impedance sensor located at a local section in extracorporeal circuit. As a result, four Δε_m (m=1, 2, 3 and 4) were extracted by RTD analysis. Among the extracted Δε_m, the variation of Δε₃ was in good agreement with heparin volume in blood which was indirectly estimated from the activated clotting time (ACT). By comparing the variations of Δε₃ and the variation of ACT, the Δε₃ reflects the dielectric relaxation due to heparin-induced aggregation of blood cells and heparin complex with other plasma macromolecules. Therefore, the Δε₃ has been shown to be one of the most important measurement indexes for the online and non-invasive monitoring of heparin volume in blood extracorporeal circulation.

At present, running safety in railway vehicles against flange-climb derailment is evaluated based on derailment quotient. This approach is preferred because measuring contact forces between wheel and rail is relatively easier than measuring the contact condition, and the dynamic condition of the contact forces can theoretically determine whether the wheel climbs the rail or not. However, in recent years, methods for grasping the contact condition have been studied, which is expected to lead to future evaluations of running safety that consider the contact condition. On the premise of this background, this study proposes a new evaluation method for the running safety against flange-climb derailment in railway vehicles, focusing on the contact conditions between wheel and rail. The method utilizes two key variables: the lateral contact position and the normalized transverse creepage, defined as the ratio of transverse creepage to wheelset angle of attack. Through vehicle dynamics simulations under various running conditions, the relationship between these variables and the running safety was investigated. Results show that the transit domains for loci of these variables differ significantly between derailment and non-derailment cases. The study also reveals that wheel lateral acceleration plays a crucial role in determining derailment occurrence. This research provides fundamental insights for developing advanced safety assessment techniques in railway operations, considering detailed wheel-rail contact dynamics.

eVTOL is anticipated to be a new mode of passenger transportation, with battery-powered systems frequently being considered due to their simple architecture, ease of maintenance, and zero in-flight emissions. However, technical limitations of batteries impose constraints on mission profiles, making the selection of the most suitable power source crucial for each application. This study focuses on passenger transport use cases for eVTOL and proposes an approach to identify the optimal power source between two candidates: battery system and series hybrid system. The proposed procedure offers significant value in the early stages of eVTOL development by enabling the identification of optimal power source specifications and the early detection of gaps between planned and required specifications. This proactive approach facilitates discussions among stakeholders regarding project assumptions, requirements, and priorities, creating opportunities for alignment. Consequently, the method is expected to save development time and reduce rework, contributing to a more efficient development process. The analysis considered various scenarios involving different annual number of passengers, route distances, and Sustainable Aviation Fuel (SAF) mixing ratios, using this procedure. Our findings suggest that without the use of SAF, the battery system covered 43% of the 23 scenarios as an optimal power source. Meanwhile, when the SAF mixing ratio reached 50%, the series hybrid system was identified as the optimal and more versatile power source in 70% of scenarios.