Papers - NOZAKI, Takahiro

ANEMONE: a framework for three-dimensional simulations of solid-state electroaerodynamic propulsion systems

H Shibata, S Shimizu, T Nozaki

Computer Physics Communications, 109749 315 2025.10

ISSN  00104655

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Solid-state electro-aerodynamic propulsion systems are devices that utilize atmospheric pressure corona discharge and have been actively researched in recent years as a means of achieving silent drones. However, these systems contain multiple, widely disparate time and spatial scales. Therefore, the governing equations of the systems, a three-component plasma fluid model that considers the presence of electrons, positive ions, and negative ions, constitute a stiff non-linear system of partial differential equations, challenging to solve. Here, we have developed an ANEMONE simulator capable of numerically estimating the corona inception voltage and energy conversion efficiency in three-dimensional solid-state electro-aerodynamic propulsion systems. Specifically, on the basis of the governing equations, we adopted the method of characteristics and the perturbation method to obtain the sub-problems. Furthermore, we have successfully obtained the integral equations, making the sub-problems easier to solve. Finally, we validated the prediction results based on the theoretical results in a previous study. Remarkably, ANEMONE is the first simulator in the world which predicted the two representative performance (i.e., the corona inception voltage and energy conversion efficiency) of fully three-dimensional propulsion systems. Program summary: Program Title: ANEMONE CPC Library link to program files: https://doi.org/10.17632/2sxsg2pmyp.1 Licensing provisions: MIT Programming language: C++ Nature of problem: Solid-state electro-aerodynamic propulsion system [1] ionizes the ambient air and can propel silent drones. For the rapid-prototyping of the system, it is important to utilize numerical simulation, but the spatial and temporal scales of the system are diverse; hence, the corresponding governing equations (e.g. the three-component plasma fluid model which can simultaneously consider electrons, positive and negative ions) are too stiff to solve. For example, the overall spatial scale of the system is the order of meters, while the scale of the electrodes is the order of micrometers. Moreover, the ions move between electrodes in the order of milliseconds, while the Maxwell dielectric relaxation time scale is in the order of nanoseconds. Solution method: For the issue of the spatial scales, we adopt a three-dimensional hierarchical Cartesian grid method together with the adaptive mesh refinement method. Moreover, this leads fully automatic mesh generation and ensures the grid convergence. For the issue of the temporal scales, we adopt the perturbation method [2] combined with the method of characteristics. This can decompose the original problem into many subproblems easy to solve. References: [1] Haofeng Xu, et al., Flight of an aeroplane with solid-state propulsion, Nature 563 (7732) (2018) 532–535. [2] Hisaichi Shibata, et al., Performance prediction of electrohydrodynamic thrusters by the perturbation method, Phys. Plasmas 23 (5) (2016).

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On the integral form of a three-component plasma fluid model

H Shibata, T Nozaki

Physics of Plasmas 32 (6) 32 ( 6 )  2025.06

ISSN  1070664X

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Solid-state propulsion is a near-silent plasma thruster that can be mounted on drones. It generates thrust by inducing corona discharge between asymmetric electrodes, which ionizes the surrounding air and accelerates it as a plasma jet. For rapid societal implementation, numerical analysis is crucial and numerous studies have addressed this aspect. However, high-thrust solid-state propulsion systems, such as MSD (multistage ducted thrusters), exhibit complex plasma flows in which both positive and negative corona discharges occur simultaneously. Therefore, MSD analysis requires the adoption of a plasma three-component model that simultaneously accounts for electrons, positive ions, and negative ions. However, because this model involves phenomena with disparate time and spatial scales, it requires substantial computational costs. In this study, different from previous research, we attempt to reduce computational cost and enhance numerical stability by first transforming the partial differential equations representing the three-component model into ordinary differential equations using the method of characteristics and then expressing those in integral form through manual calculation. The derived integral solution was validated by comparing it with experimental results from negative corona discharge within a coaxial cylinder electrode and point-to-plate electrodes and negative corona discharge around a single-stage thruster, confirming that the simulation's predictive accuracy is reliable.

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Thrust Control with Switching in Electrodynamic Propulsion Systems with Corona Discharge

S Yashita, H Katagiri, T Kitamura, T Nozaki

2025 IEEE International Conference on Mechatronics (ICM), 1-6  2025

ISSN  2837-1143

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Electroaerodynamics (EAD) is one phenomenon that manipulates gas with high voltage. Corona discharge is a typical example and is known to produce thrust quietly without moving parts. Therefore, it is expected to be utilized in various ways, such as a thrust source of drones. As thrust with corona discharge depends on the applied voltage, it is necessary to manipulate the applied voltage for thrust control. However, large-scale systems require several tens of kV, and there is little adequate research on these systems. Thus, an adequate switching method is essential, and it is also crucial to elucidate the effect of switching on thrust. Hence, this study conducted thrust control with corona discharge and analyzed the influence of switching on thrust. Specifically, a resistor is connected in series to the electrode, and a switching element is connected in parallel with the resistor. The proposed method stabilizes and limits the voltage applied to the switching element and effectively controls the thrust and the voltage applied to the electrode. Two experiments were conducted to reveal the electrical characteristics of the electrode in corona discharge and confirm the effectiveness of the proposal. The first experiment showed the potential of switching for the electrode with corona discharge on the collector side. Moreover, the second experiment demonstrated that the proposed switching method worked properly, and thrust can be controlled by changing the duty ratio of switching. The achievements of this study are expected to control levitation systems EAD, such as corona discharge, and realize stable control.

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Positioning Control for Voice Coil Motor Using Unbalanced Multilevel Inverter Topology

G Takei, H Obara, R Haneda, T Nozaki

2025 IEEE International Conference on Mechatronics (ICM), 1-6  2025

ISSN  2837-1143

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This article proposes a new multi-level inverter (MLI) based on flying capacitor inverter (FCI), with focused on high-precision positioning control for a voice coil motor (VCM). Multi-level inverters (MLIs) have the characteristic that increasing the number of output voltage levels reduces the output voltage error. However, as the number of levels increases, the number of circuit elements increases, and the circuit becomes more complex. In addition, the output voltage amplitude for each level is constant in conventional inverters. As a result, such as high-precision positioning control of VCM, designing an appropriate inverter for a reference wave that contains a large amount of low-voltage components increases the number of circuit elements. Therefore, this paper proposes a MLI with two unbalanced dc-input voltages, referred to as unbalanced MLIs (UMLIs) hereinafter. This topology uses two different dc-input voltages, and it is possible to reduce the output voltage level in extremely low-voltage range compared to other voltage levels. Simulation results when the high-precision positioning control of the VCM confirm that the proposed UMLIs improves the control performance compared to the conventional FCIs with equal number of output voltage levels and uniform level widths.

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Investigation of Relationship between Electrode Integration Method and Force-to-Volume Ratio in Force Generation System Using Corona Discharge

H Katagiri, S Yashita, T Kitamura, T Nozaki

2025 IEEE International Conference on Mechatronics (ICM), 1-6  2025

ISSN  2837-1143

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A force generation mechanism utilizing corona discharge has the advantages of being lightweight, compact, and having no moving parts. The general structure of an electrode used to generate corona discharge is a wire on the high-voltage side and a flat plate on the ground side. To gain greater force generated by corona discharge, it is necessary to install and integrate a large number of electrodes. However, if a large number of electrodes are integrated, the required volume will increase. Therefore, a method of integrating the electrodes to increase the force-to-volume ratio is needed. Therefore, this paper comprehensively examines the two-dimensional arrangement of electrodes on the ground side and investigates the relationship with the force-to-volume ratio. Specifically, the force-to-volume ratio was investigated when the ground side was made of hollow hexagons, squares, or triangles compared to the wire-plate electrode. Also, since it is known that the force is more significant when needles are used on the high-voltage side rather than wires, the high-voltage side was made into a needle for electrodes with hollow polygons. The experimental results show that the force-to-volume ratios of the needle-hollow polygon electrodes were larger when the applied voltage was low, around 20 kV, and that of the wire-plate electrode was larger when the applied voltage was higher than 30 kV. These results show the relationship between the method of integrating the electrodes and the force-to-volume ratio, which was unknown in corona discharge. They can be used as a reference in the design of actuators.

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Performance prediction of fully three-dimensional solid-state propulsion systems by eigenvalue problem decomposition

H Shibata, T Nozaki

arXiv e-prints, arXiv: 2503.17910  2025

Control Stiffness-Based Motion Reproduction for Environmental Impedance Variation

A Takakura, T Nozaki

2025 IEEE International Conference on Mechatronics (ICM), 1-6  2025

ISSN  2837-1143

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Motion generation technology contributes to the automation of the robots, especially in the industrial field. Imitation learning and motion reproduction system (MRS) are one of the motion generation methods that widely applied. However, machine learning-based methods require a large amount of data and are weak against extrapolation. Although MRS has merit in terms of the data number, it is weak regarding environmental variation. In particular, the environmental impedance variation have occurred, both position and force tracking are impossible. As several conventional studies have been done to reduce only position or force tracking errors, they can not adapt force or position priority tasks, respectively. Therefore, this paper proposes a novel compensation law based on designed control stiffness using the hybrid angle. The validity of this proposal is confirmed by simulation. This paper contributes to the MRS expansion of the environmental impedance variation with consideration of the task's priority physical value.

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ANEMONE: a fully three-dimensional solid-state electro-aerodynamic propulsion system simulator

H Shibata, S Shimizu, T Nozaki

arXiv preprint arXiv:2503.17910  2025

Consideration of Micro-Macro 4-channel Bilateral Control Scheme Using Piezoelectric Actuator

S Kozu, T Nozaki

2025 IEEE International Conference on Mechatronics (ICM), 1-6  2025

ISSN  2837-1143

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In micro-manipulations such as cell manipulation, if the operator can feel the tactile sensation of the object, those operations are expected to be more efficient. Scale bilateral control, in which micro-manipulation is performed remotely and position and force information is transmitted bidirectionally between the two systems, could be one of the solutions for tactile transmission. In this control, the use of a linear motor as a human-operating system and a stacked piezoelectric actuator as a micro-manipulating system has been proposed. In this context, a linear motor is an inertial system, and a piezoelectric actuator is a stiff system. However, the control scheme and theory of bilateral control have been established only for inertial systems. In previous studies, piezoelectric actuators were modeled as inertial systems, and the construction of bilateral control systems according to the scheme of inertial systems was attempted. This paper attempts to construct bilateral control by modeling piezoelectric actuators as a second-order linear system close to the actuator's physical properties. Experiments revealed that the proposed bilateral control scheme performs well as the conventional scheme. This study contributes to constructing bilateral control between two systems with different structures.

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Force/Tactile Sensation for Contact Task

K Ohnishi, T Nozaki, Y Saito, H Asai, T Kitamura

Emotional Engineering, Vol. 10: Emotional Engineering as a Culture for 22nd …  2025

Development of a Support Vector Machine-based Automated Facial Le Fort I Osteotomy Robot

K Niwa, K Yane, Y Saito, K Hashikawa, T Nozaki

 2025

Simultaneous two-axis position estimation of receiver coil using different radii of transmitter coils in WPT

Y Tomioka, T Nozaki

IECON 2024-50th Annual Conference of the IEEE Industrial Electronics Society …  2024

ISSN  21624704

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Wireless power transmission (WPT) is a major technology and is mainly used in transmitting power to small electronic devices. WPT is also expected to be used for larger, higher-power devices such as EVs. One of the problems with the use of WPT is the loss of efficiency due to the misalignment of the transmitter and receiver coils. Previous studies focus on circuital methods to prevent efficiency loss such as impedance matching or frequency tuning. However, these methods do not solve the coil misalignment itself. The purpose of this paper is to propose a two-axis position estimation method in order to eliminate the misalignment. The two axes mean the parallel and vertical directions of the coils. Knowing coil position information in two axes will contribute significantly to position adjustment between coils, compared to the case of only one axis position information. This paper also verified the accuracy of the proposed method experimentally.

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Robot command upgrade by integration of position and force information from multiple motion reproduction results

K Yane, T Nozaki

IECON 2024-50th Annual Conference of the IEEE Industrial Electronics Society …  2024

ISSN  21624704

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Motion reproduction is a motion generation method in robotics characterized by the small amount of required data and its adaptability to environmental variations. However, completing the task is difficult when the environmental position variation is significant. Therefore, the proposed method generates motion data that is adaptive to environmental fluctuations by performing motion reproduction, with data integrating the position and velocity responses when motion reproduction is performed and the original force response. In simulations, it successfully made contact with the environment even when the distance to the environment was varied. In other words, the proposed method can create motions such that the task succeeded using the failed reproduction data.

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Probing Signal Injection for Compatible Realization of Operationality and Impedance Identification

A Takakura, K Yane, T Nozaki

IECON 2024-50th Annual Conference of the IEEE Industrial Electronics Society …  2024

ISSN  21624704

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Environmental recognition has an important role in tele-operation. It contributes to the stabilization of complex interactions of robots with the environment. Previous studies have focused on the vision-based method. However, subject dynamics, expressed as stiffness or viscosity, can not be obtained from visual information. One method to determine this is to apply a probing signal to the system and satisfy persistent excitation (PE). However, it comes with the disadvantage of deteriorating operationality for the vibration. Thus, this paper proposed a probing signal compensation method for a 4ch bilateral control system by using a band-pass filter (BPF). Therefore, dynamics identification was accomplished with sufficient PE derived from the probing signal. While on the leader device, oscillations were suppressed and operationality was guaranteed. The proposal contributes to compatible environmental recognition and operationality indemnification for tele-operation systems.

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Experimental Validation of Admittance-based Bilateral Teleoperation Preventing Position Drift Using Position-controlled Industrial Manipulators

I Kotani, T Nozaki

IECON 2024-50th Annual Conference of the IEEE Industrial Electronics Society …  2024

ISSN  21624704

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Bilateral teleoperation is a key technology that enables to perform contact-rich tasks remotely. Bilateral teleoperation using commercial industrial manipulators has practical advantages, however, industrial manipulators have low backdrivability and no torque control, so admittance-based force control is required. 2ch admittance-based bilateral teleoperation has been proposed that is compatible with industrial manipulators. However, the conventional 2ch admittance-based type does not take into account the discrepancy of admittance control period and communication period between the leader and the follower that bring out position drift. In this paper, 4ch admittance-based bilateral teleoperation that prevents position drift is proposed, and a comparison between three constructs of admittance-based teleoperation using position-controlled industrial manipulator is conducted through experiments using commercial industrial manipulators Yaskawa GP7 and HC10DTP.

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Control for 2-DOF electroaerodynamic levitation systems considering discharge characteristics

S Yashita, H Katagiri, K Yane, T Kitamura, H Tsubata, T Nozaki

IECON 2024-50th Annual Conference of the IEEE Industrial Electronics Society …  2024

ISSN  21624704

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Electroaerodynamics (EAD) is a phenomenon that generates a gas motion by applying high voltage between electrodes. One method of creating thrust with EAD is the use of the corona discharge, which is a self-sustaining discharge. Since it does not require any moving parts, the corona discharge produces thrust robustly and quietly. Therefore, this thrust system is expected to be utilized as the thrust source for drones. However, since the relationship between thrust and applied voltage is nonlinear, dealing with this problem in control is indispensable. Although some studies have been conducted on control methods with the corona discharge, few have been performed on multidegrees of freedom (DOF) control based on theoretical modeling, which is essential for achieving attitude control during flight. Thus, this paper proposes a control system based on theoretical modeling to realize 2-DOF height and angle control. This study utilizes the idea of differential mode and voltage range limitations and introduces a disturbance observer (DOB) to construct a control system. Two simulations are conducted to verify the effectiveness of the proposal. The first simulation shows that the proposal can follow the command value with small errors, indicating the possibility of multi-DOF control. The second simulation revealed that the proposal significantly suppressed attitude change under disturbance and contributed to improved responsiveness.

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Vertical Adjustment Method with Mechanical Power Factor Feedback

T Shimada, K Yane, I Kotani, S Kozu, T Nozaki

2024 IEEE 33rd International Symposium on Industrial Electronics (ISIE), 1-6  2024

ISSN  21635137

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There are some dangerous situations under tunnel construction. Since humans fill small halls on the surface of a tunnel with explosives by their hands, they always work with risks of injury or death due to accidents of unexpected explosions or collapses of tunnels. In order to proceed with construction, remote control robots that take the place of their work have been developed. Although they made construction safer for humans, the operation of remote control robots is difficult. This paper proposes a method to adjust the angle vertically by using mechanical power factor feedback. When the robot's arm hits the target object, it estimates an angle deviation by mechanical power. The mechanical power factor is an analogy to power factor in electronics, which is proposed to estimate an angle deviation easily instead of using an angle sensor. It makes it possible not only to evaluate a performance of robots but also estimate an angle deviation for the vertical adjustment. Thus, the proposal has advantages in terms of focusing on the mechanical power factor. By conducting simulations, the results of the estimation of angle deviation were verified.

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Realization of Scaled Admittance Bilateral Control with Different Inertias Using Piezoelectric Actuator

S Kozu, I Kotani, K Seki, N Motoi, T Nozaki

2024 IEEE International Conference on Advanced Intelligent Mechatronics (AIM …    1103 - 1108 2024

ISSN  21596247

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In micro-manipulations such as cell manipulation, it is desirable for the operator to feel the haptic sensation of the object. Bilateral control can remotely transmit position and force information between leader and follower systems. In this control, the use of a linear motor as a leader and a stacked piezoelectric actuator as a follower has been proposed to achieve micro-scale operation. There is a lot that needs to be clarified about bilateral control when the structure differs between leader and follower systems. In conventional scaled 4channel (4ch) bilateral control, a theory of oblique coordinate control has been proposed that considers differences in the inertia of leader and follower systems. However, when a piezoelectric actuator is used, the control scheme differs from using two linear motors with different inertias because the structures of the leader and follower systems are entirely different. Another method is scaled admittance bilateral control. However, the control design when structures and inertias of the two systems are different has not yet been clarified. In this paper, a scaled admittance bilateral control using a piezoelectric actuator and a linear motor is constructed. Experiments confirm that the realized scaled admittance bilateral control has the equivalent position and force tracking performances as the conventional scaled 4ch bilateral control using a piezoelectric actuator. Furthermore, the designed scaled admittance bilateral control is more robust to fluctuations in the nominal inertia of the piezoelectric actuator than the conventional scaled 4 ch bilateral control.

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Motion Reproduction of Loading Explosive with Compensation for Variations in Position and Direction of Hole by Image Processing

M Horikoshi, I Kotani, T Nozaki

2024 IEEE International Conference on Advanced Intelligent Mechatronics (AIM …    1151 - 1156 2024

ISSN  21596247

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Mountain tunnel excavation has two problems, which are a shortage of skilled engineers and frequent industrial accidents. Automation of mountain tunnel excavation is progressing to solve these problems. However, loading explosives in mountain tunnel excavation is difficult to automate because this task requires a sense of force. Motion reproduction is an expected method to automate the process of loading explosives that takes the sense of force into account. It uses bilateral control to save and reproduce motions and has the advantage of being able to reproduce forces and teach human skills to manipulators. On the other hand, motion reproduction cannot succeed in saved tasks when the relative position of the loading hole and manipulator or the direction of the loading hole changes from the saving phase. Therefore, this paper proposes a method to compensate for variations in relative position and direction by image processing based on depth information in motion reproduction for automation of loading explosives. Experiments showed the effectiveness of the proposed method through the successful reproduction of the insertion motion despite variations in relative position and direction.

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Effect of Coil Size on Efficiency of Wireless Power Transfer with Magnetic Field Resonant by Halbach Array

T Oba, Y Tomioka, T Nozaki

2024 IEEE International Conference on Advanced Intelligent Mechatronics (AIM …    1050 - 1055 2024

ISSN  21596247

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In recent years, wireless power transfer (WPT) has become popular from the viewpoint of easy charging. Among them, magnetic field resonance WPT is being researched and developed due to its high efficiency. However, there are magnetic fluxes that cannot be used for power supply and are leaking out in magnetic field resonance WPT. Therefore, this paper applies a special magnet arrangement, a Halbach array, for transmission coils. The Halbach array transmission coils can concentrate the magnetic fluxes on one side. This feature allows the magnetic fluxes to be concentrated to increase the amount of magnetic fluxes chained to the receiving coil. It has a significant effect on efficiency. Since the size of the transmission and receiving coils also affects efficiency, this paper changes the size of the coils and analyzes its effect on efficiency. The efficiency of the Halbach array transmission coils will be confirmed by comparison with conventional transmission coils.

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