arXiv subjects

Takahiro Nozaki

Publications and source records attributed to Takahiro Nozaki.

4 recordsLinked to original sources

arXiv2025

On the numerical simulations of electric field-enhanced solid-state electro-aerodynamic thrusters enabled with an insulated electrode

A solid-state electro-aerodynamic propulsion system applies a high electric potential difference between two electrodes to ionize air within the resulting electric field, accelerating the ions to generate thrust. Previously, the so-called ``decoupled thrusters'' have been proposed, in which ion generation and acceleration are spatially decoupled. Here, we argue that such decoupling is infeasible from the perspective of electric field lines if the diffusion effects are ignored, and consequently the driving method (e.g., dielectric barrier discharge) for the additional electrodes can be improved. Specifically, the use of auxiliary electrodes that do not discharge but induce ionization and attachment can be appropriate. This concept was named the electric field-enhanced solid-state electro-aerodynamic propulsion system. Furthermore, through numerical simulations, this concept showed improvement in thrust density while maintaining the thrust-to-power ratio.

physics.plasm-ph↗

arXiv2025

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

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 of fully three-dimensional propulsion systems.

physics.plasm-ph↗

arXiv2020

Stability and Robustness of the Disturbance Observer-based Motion Control Systems in Discrete-Time Domain

This paper analyses the robust stability and performance of the Disturbance Observer- (DOb-) based digital motion control systems in discrete-time domain. It is shown that the phase margin and the robustness of the digital motion controller can be directly adjusted by tuning the nominal plant model and the bandwidth of the observer. However, they have upper and lower bounds due to robust stability and performance constraints as well as noise-sensitivity. The constraints on the design parameters of the DOb change when the digital motion controller is synthesised by measuring different states of a servo system. For example, the bandwidth of the DOb is limited by noise-sensitivity and waterbed effect when velocity and position measurements are employed in the digital robust motion controller synthesis. The robustness constraint due to the waterbed effect is removed when the DOb is implemented by acceleration measurement. The design constraints on the nominal plant model and the bandwidth of the observer are analytically derived by employing the generalised Bode Integral Theorem in discrete-time. The proposed design constraints allow one to systematically synthesise a high-performance DOb-based digital robust motion controller. Experimental results are given to verify the proposed analysis and synthesis methods.

eess.SY↗

arXiv2019

A Stability Analysis for the Acceleration-based Robust Position Control of Robot Manipulators via Disturbance Observer

This paper proposes a new nonlinear stability analysis for the acceleration-based robust position control of robot manipulators by using Disturbance Observer (DOb). It is shown that if the nominal inertia matrix is properly tuned in the design of DOb, then the position error asymptotically goes to zero in regulation control and is uniformly ultimately bounded in trajectory tracking control. As the bandwidth of DOb and the nominal inertia matrix are increased, the bound of error shrinks, i.e., the robust stability and performance of the position control system are improved. However, neither the bandwidth of DOb nor the nominal inertia matrix can be freely increased due to practical design constraints, e.g., the robust position controller becomes more noise sensitive when they are increased. The proposed stability analysis provides insights regarding the dynamic behavior of DOb-based robust motion control systems. It is theoretically and experimentally proved that non-diagonal elements of the nominal inertia matrix are useful to improve the stability and adjust the trade-off between the robustness and noise sensitivity. The validity of the proposal is verified by simulation and experimental results.

eess.SY↗