掲載種別：研究論文（学術雑誌）   出版者・発行元：International Journal of Thermophysics  

The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s1/2·m2·K) to 1253 J·(s1/2·m2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s1/2·m2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surface boulders compared with the thermal diffusion length. Consequently, it was found that the present result is more representative of the thermal diffusivity and thermal inertia of local part of individual Ryugu particles.

DOI： 10.1007/s10765-023-03158-6

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：International Journal of Thermophysics  

We propose a versatile method for measuring the thermophysical properties of composites by means of lock-in thermography (LIT) technique. The method is based on analyzing the thermal response distribution induced by periodic laser heating, which enables simultaneous high-spatial-resolution mapping of the effective out-of-plane thermal diffusivity, thermal conductivity, and volumetric heat capacity over the surface of the material. We validate the method using a reference material and demonstrate its capability in visualizing the effective properties of laminated carbon fiber reinforced plastic and carbon fiber reinforced thermoplastic with discontinuous fibers. The results showed that the LIT-based approach has high reproducibility and sensitivity, which allows observing the effect of fiber orientations on the effective properties. The proposed method will be useful for thermal research in composites, defect detection, and for investigating component geometric arrangement effects on the thermophysical properties.

DOI： 10.1007/s10765-022-03109-7

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Physics Letters  

We demonstrate a versatile measurement method for the thermoelectric figure of merit and related transport properties by means of a multi-harmonic thermal analysis of a thermographic movie. The method is based on the thermal analyses of the charge-current-induced temperature distribution generated by the Peltier effect at the first harmonic and by Joule heating at the second harmonic, measured with an infrared camera. This allows simultaneous estimation of the thermal diffusivity, thermal conductivity, volumetric heat capacity, and Peltier/Seebeck coefficient of conductors without attaching an external heater. The thermal analysis developed here is applicable to a system with the interfacial thermal resistance between the target conductor and reference material. Our method enables the measurements while applying an external magnetic field, opening the way for investigating the magnetic field and/or magnetization dependences of the figures of merit and associated properties for the magneto-thermoelectric effects. We demonstrate the usability of this method by estimating the figures of merit for the Peltier/Seebeck, magneto-Peltier/Seebeck, and Ettingshausen/Nernst effects in a Bi-Sb alloy as a promising material for thermoelectric applications. The multi-harmonic thermal analysis method will, thus, aid in developing highly efficient thermoelectric materials and further investigations of magneto-thermal and magneto-thermoelectric transport properties.

DOI： 10.1063/5.0105282

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Robotica  

Electromagnetic actuation systems (EMA) have excelled themselves in microscale manipulation. Yet, the fastened structure of the current systems tethers the controlled workspace. In this paper, a new electromagnetic actuation principle is investigated. The actuator structure consists of a pair of coaxially movable electromagnets integrated to a robotic manipulator. The pair induces a coaxial homogeneous magnetic field or gradient to control the magnitude of the magnetic torque or force by changing the distance between the electromagnets asymmetrically. The robotic manipulator, on the other hand, transports the pair at five degrees of freedom to manipulate a microrobot in 3D space by closed-loop control with integrated vision feedback system. Numerical analyses are performed to investigate the induced electromagnetic field at the symmetrical/asymmetrical configuration of the coaxial pair. Accordingly, a correlation between the magnitude of the magnetic force and the asymmetric distance is obtained for flexible force control. A proof of concept prototype is constructed to validate the proposed actuation principle and evaluate its performance experimentally. The experimental results verify the numerical analysis and show the system applicability of inducing controlled forces on a micro-object in 2D and 3D workspaces at a velocity range of 65 to 157 μm/s. Moreover, micromanipulation on a helical route is also demonstrated with an absolute error mean from the reference path of 191 μm.

DOI： 10.1017/S0263574722000418

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掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)  

The recent development of wearable interfaces raises the challenge of their thermal management requirements. Motivated by that, a novel flexible loop heat pipe (FLHP) of high heat transfer efficiency to be mounted on wearable devices is presented. Initially, the design of the FLHP is caried out by a constructed thermal analysis model. The FLHP is then formed from PDMS by a developed microfabrication process. A proof of concept FLHP prototype with dimension of 80×45×1.2 mm with high flexibility is obtained. The thermal performance test was conducted at three different heat loads. The results show the FLHP operates successfully with promising potential to be applied on wearable electronics or any other flexible MEMS applications.

DOI： 10.1109/MEMS51782.2021.9375378

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Sensors and Actuators, A: Physical  

Electromagnetic actuation systems have remarkably proved themselves in the field of contactless power transmission systems. Nevertheless, the stationary position of the operated electromagnets or their rotation around a fixed axis resulted in a restrictive and limited versatile workspace. In this paper, a new design of a steel cored solenoidal coil is proposed for a novel microrobot electromagnetic actuator. The new system combines a 6 DOF industrial robotic manipulator with co-axially movable electromagnets. Considering the maximum weight and workspace limitations of the robotic manipulator, seven essential dimensions of the electromagnet were investigated with the aid of a simulation software. A set of parametric studies were carried out in order to optimize the homogeneity of the induced magnetic field at the highest achievable intensity based on Ad hoc method. The results showed that an electromagnet with a square prism core and a large front, induces a more homogeneous and intense magnetic field. Moreover, by shortening the length of the coil and increasing the length of the core, the intensity of the magnetic field significantly increases without much affecting its homogeneity. The electromagnet was fabricated according to the final result of the numerical studies and evaluated by performing experimental measurements on the induced magnetic field. Furthermore, with several programed motions, the performance of the proposed untethered electromagnetic actuation system was demonstrated experimentally.

DOI： 10.1016/j.sna.2018.11.027

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掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)  

This paper describes a macro/micro robot manipulation system consisting of an electromagnet couple and an industrial manipulator. The system has capability of motion 6 Degrees of Freedom (6 DOF) providing the same amount of DOFs to the manipulation of the microrobot. A custom-design mechanism which is attached onto the tip of the industrial manipulator provides the required magnetic field profiles for force and torque generation using coil couple and their ability sliding motion in linear directions. This combination provides reprogrammable working space for the microrobot manipulation. Robot Operating System (ROS) based programming integrates all the subsystem software. Visual feedback assures the real-time microrobot position and orientation data. Close-loop motion control of the microrobot was tested using custom designed constrained paths take part in a plane. Experiment were presented for specific motions of the microrobot to show the microrobot motion abilities. The results are promising which may orient to the applications like micro assembly and micromanipulation.

DOI： 10.1007/978-3-030-26118-4_1

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Colloids and Surfaces A: Physicochemical and Engineering Aspects  

The main purpose of this study is to focus the light for the first time on the recognized re-dispersion ability of the sonicated MWCNTs within low viscous mineral oil. For that, pure MWCNTs, without any special treatment, were dispersed in mineral oil by sonication without using any stabilization method. After full agglomeration, it was realized that agitating, shaking or even blowing compressed air on the agglomerated nanolubricant is able to break down the aggregation of the MWCNTs. Microscopic video is presented to clarify the behavior of the tubes during the re-dispersion process. Quantitatively, particle size distribution (PSD) was employed to evaluate the re-dispersion quality. The viscosity and thermal conductivity of both recently sonicated and re-dispersed samples were also investigated with accurate measurement setups at four different weight concentrations (0.05, 0.1, 0.2 and 0.3 wt.%). It was observed that the sonicated MWCNTs are separated, saturated, lubricated, and surrounded by oil layers, which not only ease its motion within the lubrication oil, but also give them the ability of detaching by applying any slight force. Moreover, the PSD results with the equal values of the viscosity and thermal conductivity, obtained within the uncertainty of the measurements, confirm that the MWCNTs were re-dispersed to the same quality of the recently sonicated ones by just shaking.

DOI： 10.1016/j.colsurfa.2017.10.085

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Key Engineering Materials  

In the presented work, thermal conductivity of CuO and its viscosity at three different weight concentrations were investigated. A two-steps method was deployed in order to sonicate successfully CuO nanolubricants samples at three different weight concentrations (0.2, 0.5, & 1 wt%). The measurements of thermal conductivity were carried out with a lab-made measurement set, which is based on a 3method. The obtained enhancements were 1%, 1.7% and 2.8% for 0.2, 0.5, and 1 wt.%, respectively. Viscosity was also investigated under different temperatures and it was obtained that adding CuO to the mineral oil had a slight effect on its viscosity at lower concentrations. However, the maximum increment at lower temperature for the higher concentration was 13.1%. Based on the enhancement in thermal conductivity and the low increment in viscosity, CuO nanolubricant can be recommended for enhancing the heat transfer characteristic of the refrigeration compressor.

DOI： 10.4028/www.scientific.net/KEM.750.159

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出版者・発行元：Studies in Computational Intelligence  

In this section, a ROS implementation of a system which is utilized for untethered microrobot manipulation is introduced. Untethered microrobot locomotion is an area that is studied globally and magnetic actuation is one of the proven methods for microrobot locomotion. Several types of actuator systems were approved by successful works and became associates in the literature works. These locomotion strategies require real-time and closed-loop control for most of the applications. We developed a custom actuation system using a coaxially aligned electromagnet couple, providing magnetic field for locomotion and the actuator structure was carried by an industrial manipulator, KUKA robot. So that, the complexity of electromagnet current control is divided into simpler sub parts that involve mechanical translation and rotation motions. This structure principle provides the capability of a larger task space. KUKA manipulator and electromagnetic actuator (EMA) as its end-effector form the main system structure. Also, visual feedback is provided by camera systems. Some tasks were distributed to peripheral NVIDIA Jetson TK1 Embedded Development Kits. Here, we focus on the integration of ROS into a microrobot manipulation or alike systems. System components, integration, control, test phases and detailed ROS components are described, an application with the results is presented.

DOI： 10.1007/978-3-030-45956-7_9

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)  

This paper describes a macro/micro robot manipulation system consisting of an electromagnet couple and an industrial manipulator. The system has capability of motion 6 Degrees of Freedom (6 DOF) providing the same amount of DOFs to the manipulation of the microrobot. A custom-design mechanism which is attached onto the tip of the industrial manipulator provides the required magnetic field profiles for force and torque generation using coil couple and their ability sliding motion in linear directions. This combination provides reprogrammable working space for the microrobot manipulation. Robot Operating System (ROS) based programming integrates all the subsystem software. Visual feedback assures the real-time microrobot position and orientation data. Close-loop motion control of the microrobot was tested using custom designed constrained paths take part in a plane. Experiment were presented for specific motions of the microrobot to show the microrobot motion abilities. The results are promising which may orient to the applications like micro assembly and micromanipulation.

DOI： 10.1007/978-3-030-26118-4_1

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：2018 6th International Conference on Control Engineering and Information Technology, CEIT 2018  

A guided microrobot position control methodology is introduced in this paper. Using an electromagnetic actuator (EMA) as an end-effector of a robot manipulator, it is possible to have microrobot follow a correlated path with robot manipulator motion in case when there is no task space feedback from microrobot environment. For this purpose, a concept EMA system with an actuation principle depending on the magnetic field homogeneity and gradient generated by two coaxially aligned electromagnets is introduced. The functionality of developed system is experimentally analyzed for translational and rotational motion tracking cases. It is observed that the correlation between the robot manipulator motion and microrobot motion is nearly 1 in x and y direction.

DOI： 10.1109/CEIT.2018.8751803

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：Mechanisms and Machine Science  

This paper proposes a comparative study in order to investigate the effect of the coil geometry on the intensity and homogeneity of the magnetic field. For this purpose, a solenoid with rectangular prism core and two different coil shapes, cylindrical and cuboid, was modeled. Several finite element numerical studies at different structural design parameters combinations for two different distances between the coils were carried out. The obtained results were evaluated according to the flux intensity and the homogeneity at the center region between the coils. Consequently, it was found that cylindrical coils generate higher flux intensity with more homogeneous magnetic field.

DOI： 10.1007/978-3-319-60702-3_25

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