Kanjuro Makihara

A low energy dissipation circuit is proposed to achieve more effective energy harvesting, called 'synchronized switch harvesting on inductor (SSHI)'. The proposed circuit only has two diodes, while the original SSHI circuit has four diodes comprising a diode bridge. It thus reduces the voltage drop during the energy-harvesting process, because the actual diodes have forward voltage regarded as equivalent electrical resistance or energy dissipation. Energy-harvesting experiments demonstrated that

An innovative method of hybrid vibration suppression using piezoelectric materials is proposed. It combines bang‐bang active vibration suppression and energy-recycling semiactive vibration suppression. The piezoelectric materials are electromechanically coupled and convert mechanical energy into electrical energy and vice versa. With this method, a part of the electrical energy needed for suppressing vibration is obtained from the mechanical energy of the vibrating structures and is efficiently

This paper discusses a self-sensing vibration suppression method that measures only the value of the piezoelectric voltage. The method separates the electrical status into two cases concerning electrical current and characterizes each of these to establish a self-sensing system using extended system equations and a Kalman filter. Our self-sensing system can avoid estimation blackout during closed-circuit status and lessen harmful influences from residual modes. Experiments revealed that the self

Aircraft performance can be improved using morphing wing technologies, in which the wing can be deployed and folded under flight conditions, providing a wide flight envelope, good fuel efficiency, and reducing the space required to store the aircraft. Because the deployment of the wing is a nonlinear-coupled motion comprising large rigid body motion and large elastic deformation, a nonlinear folding-wing model is required to perform the necessary time-domain deployment simulation, while a linear

This paper presents an extensive investigation on the LR-switching method (also called the energy-recycling semi-active method). Compared with the energy-dissipative R-switching method, the LR-switching method has been shown to have significantly better vibration suppression performance. However, certain essential issues affecting a system employing the LR-switching method remained to be dealt with. In particular, we had to clarify its vibration suppression mechanism from the viewpoint of mechan

A novel self-sensing method using piezoelectric actuators for semi-active vibration suppression is proposed and investigated. By using extended system equations, this self-sensing method can be implemented with a Kalman filter instead of the conventional bridge circuit technique. The method separates electrical status into two cases concerning electrical current, and characterizes each of these to establish the self-sensing system. This method is applicable to multiple-degree-of-freedom structur

A momentum-wheel installed to provide attitude-control torque actually produces undesirable force or torque disturbances owing to wheel imbalance and imperfection of the ball-bearings. To improve the pointing performance of observation satellites, a vibration isolator is used to isolate observation devices from these disturbances. This paper compares three types of semi-active isolators that consist of a piezoelectric material and a switch-controlled passive circuit. Since this isolation is impl

This paper proposes an innovative energy-harvesting controller to increase energy harvested from vibrations. Energy harvesting is a process that removes mechanical energy from a vibrating structure, which necessarily results in damping. The damping associated with piezoelectric energy harvesting suppresses the amplitude of mechanical vibration and reduces the harvested energy. To address this critical problem, we devise an energy-harvesting controller that maintains the vibration amplitude as hi

We present stability investigations on vibration cancelling employing three different types of variable-stiffness actuators. A two-mass system is considered, with a base mass attached to the ground and a top mass connected to the base mass. The top mass is subject to self-excitation forces. The stiffness of an actuator connecting the base mass and the ground may change with time, according to a predetermined control frequency, for cancelling vibrations. Numerical simulation is employed as the ba

We enhanced the bang-bang vibration control by using an electrical resonance mechanism. The bang-bang method is used in many engineering applications because of its simplified hardware configuration in which a constant-voltage supplier is shared by multiple actuators. However, its control performance is restricted, because the supplied voltage is constant and the sharp modulation of the control input induces chattering, which wastes a significant amount of energy. Our approach to overcome these

A novel invention, a digital self-powered autonomous system, is proposed to achieve sophisticated vibration suppression dealing with multimodal vibrations. This vibration suppressor can be used ubiquitously at any site because it does not require an external power supply or a central control authority. The digital approach enables the system to be programmed, and thus, it affords some versatility with regard to control schemes. The proposed system is a vast improvement over conventional analog-a

This article proposes new methods for enhancing the active harvest of piezoelectric energy using the synchronized switch harvesting on inductor (SSHI) technique. It was experimentally confirmed that the energy harvested by the original synchronized switch harvesting on inductor technique was decreased by the suppression of the vibration amplitude, and this critical problem was solved by developing new control strategies, namely, switch harvesting considering vibration suppression (SCVS) and adap

Abstract This study aims to increase the amount of electrical energy harvested from a piezoelectric vibration energy harvester under unloaded and high-load resistance conditions. Although increased piezoelectric charge due to the synchronized switch harvesting on inductor (SSHI) strategy damps mechanical vibrations, the mechanical vibration amplitude of a mechanical element in a harvester is assumed to be constant for most discussions regarding the active harvester with SSHI strategy. However, t