Yuta Yamamoto

A novel controller to increase harvested energy from negating vibration-suppression effect

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 high as possible to increase the harvested energy. Our proposed switching controller is designed to intentionally stop the switching action intermittently. We experimentally demonstrate that the proposed control scheme successfully increases the harvested energy. The piezoelectric voltage with the proposed controller is larger than that with the original synchronized switching harvesting on inductor (SSHI) technique, which increases the harvested energy. The stored energy with our controller is up to 5.7 times greater than that with the conventional SSHI control scheme.

Strategy for enhancing the active harvesting of piezoelectric energy

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 adaptive SCVS (ASCVS). The SCVS technique was designed to intentionally skip some of the switching actions of the original synchronized switch harvesting on inductor technique, while the ASCVS technique enables more flexible variation of the number of skipped switching actions. The skipping of the switching actions facilitates the recovery of the vibration amplitude produced by the excitation force, and the developed strategies thus maintain the vibration amplitude at the highest possible level, resulting in increased energy harvest. The results of the experimental implementation of the proposed strategies showed that they enabled the harvesting of as much as 10.5 times the energy harvested by the original synchronized switch harvesting on inductor technique. The ASCVS technique particularly enables flexible enhancement of the harvested energy under various vibration conditions.

Cytochrome c1 in ductal carcinoma in situ of breast associated with proliferation and comedo necrosis

It is well known that comedo necrosis is closely associated with an aggressive phenotype of ductal carcinoma in situ (DCIS) of human breast, but its molecular mechanisms remain largely unclear. Therefore, in this study, we first examined the gene expression profile of comedo DCIS based on microarray data and identified CYC1 as a gene associated with comedo necrosis. Cytochrome c1 (CYC1) is a subunit of complex III in the mitochondrial oxidative phosphorylation that is involved in energy production. However, the significance of CYC1 has not yet been examined in DCIS. We therefore immunolocalized CYC1 in 47 DCIS cases. CYC1 immunoreactivity was detected in 40% of DCIS cases, and the immunohistochemical CYC1 status was significantly associated with tumor size, nuclear grade, comedo necrosis, van Nuys classification, and Ki‐67 labeling index. Subsequent in vitro studies indicated that CYC1 was significantly associated with mitochondrial membrane potential in MCF10DCIS.com DCIS cells. Moreover, CYC1 significantly promoted proliferation activity of MCF10DCIS.com cells and the cells transfected with CYC1 siRNA decreased pro‐apoptotic caspase 3 activity under hypoxic or anoxic conditions. Considering that the center of DCIS is poorly oxygenated, these results indicate that CYC1 plays important roles in cell proliferation and comedo necrosis through the elevated oxidative phosphorylation activity in human DCIS.

An Innovative Controller to Increase Harvested Energy

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 high as possible to increase the harvested energy. Our proposed switching controller is designed to intentionally stop the switching action intermittently. We experimentally demonstrate that the proposed control scheme successfully increases the harvested energy. The piezoelectric voltage with the proposed controller is larger than that with the original synchronized switching harvesting on inductor (SSHI) technique, which increases the harvested energy. The stored energy with our controller is up to 5.7 times greater than that with the conventional SSHI control scheme.

Sensorless Method for Switching Energy Harvester Based on Self-Sensing Approach

Vibration energy harvesting extracts electrical energy from vibrating structures. The past studies of vibration energy harvesting suggest that the efficiency can be improved by switch regulation in the harvesting circuit. The switch-regulation is carried out depending on the motion of the target structure with the use of vibration sensors such as displacement sensor or accelerometer. This paper proposes a new vibration self-sensing method for switching energy harvesters that do not use those vibration sensors. In this method, the voltage of the piezoelectric transducer is measured, and the structural vibrational status is estimated from the measured voltage. The transducer voltage is not smooth and does not maintain the sinusoidal wave even when the structure vibrates in a sinusoidal wave because the switch energy harvesting method inverses the transducer voltage at every period. Thus, we establish a state observer based on a Kalman filter to estimate three state values of the target harvesting system: modal displacement, modal velocity, and electric charge in the transducer.This paper describes the construction processes for the observer. The observed value is the transducer voltage. We also show an electric circuit for measuring the transducer voltage. Finally, we confirm the efficiency of the proposed state observer for switch harvesting with numerical simulations.Copyright

Enhancement of Digital Self-Powered Energy-Harvesting for 2DOF Mixed-Mode Vibrations

The digital self-powered energy harvesting method that we propose is a switching-type vibration energy harvesting method that has a circuit that is functionally integrated with a digital processor. The main feature of the proposed harvester is that the digital processor is driven by energy harvested from vibration. Therefore, other electrical power sources, such as batteries, are not required to power it. The self-powered digital processor automatically changes the states of the harvester circuit using a switching control method. The switching is synchronized with the vibration phase, which is conducive to the effective conversion of vibrational energy. The proposed harvester is programmable and easily implements different types of control schemes based on its various parameters. This study has two objectives regarding the digital self-powered harvesting method. The first objective is to evaluate the power generation performance of the self-powered harvester for multimodal vibrations. Several experiments employing an experimental apparatus with two degrees of freedom (2DOF) are conducted. The second objective is to apply a new switch control scheme to our proposed harvesting method. The scheme is designed for moderate energy harvesting: it intentionally pauses the harvesting action so as to increase the amount of energy generated later. This method is different from the former method of switch control. We confirm the usability of the new control scheme in a digital self-powered system.Copyright

Digital Energy Harvester for Random or Multimodal Structural Vibrations

A digital energy harvester that captures electrical energy from complicated random or multimodal vibrations is proposed. The novel energy harvester is digital, autonomous, and controlled by a self-powered microprocessor. The digital self-powered microprocessor automatically and synchronously changes the circuit components with the vibration phase, and can therefore achieve autonomous harvesting. The multifunctional and self-controlled microprocessor is only driven by the voltage of the piezoelectric transducer, and no external power is required. The harvester exhibits great potential and versatility and is applicable to many machines and devices.Copyright