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To increase semiconductor production yield and meet the growing global demand, air bearings offering higher processing speeds and reduced friction losses have been proposed as an ideal solution. However, due to the non-contact support characteristic of air bearings, challenges such as shaft displacement caused by processing resistance inevitably arise. As an engineering requirement, the shaft must restrict lateral deflection to within 30 μm under transverse force. In our previous research, a compensation system using a nozzle–flapper mechanism as a displacement sensor was proposed to address shaft displacement. The effectiveness of the nozzle–flapper system in measuring shaft displacement was validated at rotational speeds up to 20,000 rpm. Furthermore, the compensation system’s ability to maintain the shaft’s initial position under a 5 N external force was verified in related collaborative research. In this study, building upon prior work, we further analyze the system characteristics of the cylindrical nozzle–flapper. This includes modeling the geometric space formed by the specific shape of the cylindrical flapper and nozzle and proposing an airflow hypothesis based on this geometry. The hypothesis is incorporated into the theoretical model of a standard nozzle–flapper system, resulting in an optimized theoretical method applicable to cylindrical configurations. Experimental results validating the effectiveness of the proposed model are also presented.

The objective of this study is to introduce and assess a computational tool designed to facilitate product development via sensory scores, which serve as a quantifiable representation of human sensory experiences. In the context of designing ride comfort performance, the specialized terminology—either technical or sensory—often served as a barrier to comprehension among the diverse set of specialists constituting the multidisciplinary team. In a previous study by the authors introduced a tool that incorporated a model of sensory performance, utilizing sensory scores as universally comprehensible metrics. However, the tool had yet to be appraised by a genuine cross-functional team. In this study, the tool underwent evaluation through a user-testing process involving twenty-five cross-functional team members engaged in the conceptual design phase at an automotive manufacturing company. Five different suspension systems were examined, including a wheel rotational speed-driven damper system developed by the authors. To evaluate the best performance of each suspension systems, sensory scores served as the objective function. Design parameters were obtained by an improved particle swarm optimization (PSO) algorithm. The assessment procedure included participants experiencing simulated vibrations through a ride simulator. This was followed by the participants’ subjective evaluations of the vibrations and structured interviews aimed at ascertaining the tool’s advantages. The results revealed that 92% of participants responded the tool would be beneficial for their work. Moreover, a new sensory performance model was then constructed, incorporating principal components derived from combined vibration data and weights determined by the collected sensory scores for four distinct feature groups.

The trend in vehicle electrification has been increasing. However, the mass of the electric vehicle increases with the battery size. Consequently, the ride and handling performance may be insufficient to meet user expectations. This study aims to provide the value of the dynamic performance of electric vehicles. In a previous study, we proposed a skyhook damping system that is driven by the wheel rotation speed signals. However, there was a problem of the feeling of a stiff ride when applying the skyhook algorithm with a slow signal communication cycle. In this paper, we clarified the causes of an incorrect damping coefficient switching timing, which excites the higher-order mode of the suspension system through a numerical analysis. As a solution, we proposed a minimal control strategy that can achieve both body damping (1–2 Hz) and isolation (3–6 Hz) through its smooth damping switching function under the limitation of a slow communication cycle of 20 ms. The performance of the proposed algorithm showed a significant improvement based on a numerical analysis and vehicle tests. As a limitation of the proposed algorithm, it has a fixed point near the sprung resonance frequency, a recommended treatment for which is discussed herein.

The aim of this study is to achieve the target transient posture of a vehicle according to the user’s steering operation. The target behavior was hypothesized to be a roll mode in the diving pitch, even during steering inputs on rough surfaces, in order to improve subjective evaluation. As a result of organizing the issues of feedforward control (FF) and feedback control (FB), we hypothesized that it would be appropriate to follow the ideal posture. The model following damping control (MFDC) was newly proposed by the authors as a solution to a control algorithm based on model-following control. The feature employs skyhook control (SH), which follows the deviation between the behavior of the reference model, which generates a target behavior with no input from the road surface, and the actual behavior of the vehicle. Numerical analyses were performed to verify the followability of the target behavior and the effect of roll damping performance. As a result of conducting actual vehicle experiments under driving conditions involving road surface input during steering, the MFDC was found to reduce the roll rate with respect to the steering angle by −6.4 dB compared to SH only.

High-aspect-ratio (HAR) rectangular jets have attracted attention in automobile air conditioning (A/C) systems and turbulent jet applications owing to their excellent air delivery and mixing and attractive interior design. Active flow control (AFC) of rectangular jets using plasma actuators (PAs) has proven to be a promising technique because the actuator is simple, has low energy consumption, and can create flow features without interference. This research aims to understand the interaction between PAs and flow from a HAR rectangular nozzle using hot-wire anemometry, particle image velocimetry, and theoretical studies. Understanding how PAs affect the flow is beneficial for designing air vents to fit automobile A/C systems and various engineering applications by recreating the flow features with other AFC techniques and actuators. The combination of periodic excitation and vectoring effects transfers the flow’s mean energy to organized structures—known as spanwise vortexes—as large as 6 mm. The interaction between these coherent structures and the dissipative environment compresses the vortexes, resulting in the flow converging on the spanwise–streamwise (X–Z) plane and diverging on the transverse–streamwise (X–Y) plane. HAR rectangular jet flow features controlled by PAs can be predicted for specific cases by calculating the Strouhal number based on PA operating parameters.

The turbulence jet centerline velocity and temperature decay intensely along the centerline flow direction. Thus, improving it could benefit engineering applications, such as air conditioners. However, active flow control techniques with high-aspect-ratio jets, especially for controlling the temperature, have not been widely investigated. This paper presents the velocity and temperature performance of a high-aspect-ratio rectangular jet controlled by two dielectric barrier discharge plasma actuators located on the longer sides of the nozzle and controlled by high-voltage and high-frequency pulse-width modulation sinusoidal waves. The scanning method was used to cover 362 cases as combinations of working parameters (modular frequency vs. duty vs. phase difference) for the velocity and temperature performances of the jets. Results show that plasma actuators can control both velocity and temperature distribution with minor input power compared with the rectangular jet’s kinetic energy and heat flux. The velocity increased up to 4% and decreased to 11%, measured at the interest position where x/h = 70 on the centerline. There were a 5% increase and a 4% decrease compared to the temperature-based case. Distinctive velocity and temperature distributions were observed under noteworthy cases, indicating the potential of the actuator to create various flow features without installing new hardware on the flow.

In this study, we conducted water hammer experiments in the tube which was periodically supported by various numbers of clamps, named periodic structure, initiated by a projectile impact. The parts of the polycarbonate (PC) tube supported by 1-7 steel clamps make the tube stiffer and heavier than the original PC tube and are expected to cause a filtering effect of the frontal frequency components in the water hammer. According to our experimental observations, we confirmed that higher frequency components more than 1 kHz in the wave front were attenuated and the peak strains in circumferential direction of the tube were decreased 20% from the original PC tube. Moreover, we conducted numerical simulations of the water hammer wave similar to the experimental setup. Numerical results also revealed that frontal peak is attenuated 22% through periodic structure.

Our study focuses on the response of a water-filled polycarbonate tube under axial impact loading to the presence of a single large suspended particle. The particles, composed of steel, aluminum, and polycarbonate, were individually suspended by elastic string along the centerline of the tube. The impact of a free-fall piston initiated pressure waves in the water, called water hammer, and stress waves in the tube, especially at the level of the particle. Hoop strains were measured as impact responses; their distribution indicated that the maximum strains occurred around the particle. These maximum strains are narrowly confined and independent of particle composition. From measurements, hoop strain above the level of the particle become larger with increasing particle mass. We propose a theoretical model that assumes the particle to be a rigid body, and estimate tube responses from the change in area due to the particle’s presence rather than a dependence on particle material. With similar conditions as in experiments, numerical simulations, performed using the software AUTODYN, revealed that the particle motion initiated a reflected pressure wave and created another pressure wave underneath the particle. The transients propagating around the particle are independent of particle material, but composition does affect the attenuation of the reflected pressure wave above the particle.

A new experimental device was developed to observe and measure dynamical generations of supercritical CO2 in a chamber. Temperature and pressure were measured locally by thin thermocouple and pressure transducer. The Rayleigh scattering in the chamber was visualized by a high-speed video camera. Heating of the liquid CO2 was conducted by a ceramic heater from the upper or the lower side of the chamber. In the case of heating from the upper side, temperature profile was stable and generates scCO2 slowly within a few seconds. On the other hand, in the case of heating from the lower side, scCO2 was created faster within a second but natural convection and turbulence were observed. Numerical simulations of the scCO2 creation in a chamber were also performed using the COMSOL Multiphysics with a program package for themophysical properties of CO2 called the PROPATH. It showed that scCO2 creation in the heating from the upper side was stable due to the gas-like properties of the scCO2 near the heater. In the case of heating from the lower side, density distribution depended on temperature distribution firstly but after natural convection grows, flow in the chamber became disturbed and the density distribution depended not only on temperature distribution but also on the density fluctuation caused by the convection vortexes. Same tendency was observed in experimental results.