Sensor-Less Approach of Self-Contained Harvester Based on Vibration State Estimation

Abstract

Vibration energy harvesting extracts electrical energy from vibrating structures. To improve the harvesting efficiency for the electrical energy, some methods were proposed that implements switches to the harvesting circuit and regulates them for controlling the structural vibrations. Self-contained SSHI harvester we proposed was one of them. Those vibration controlling harvesting methods need to measure the vibration state because the switch regulation is based on the vibration state. In our previous studies to develop the self-contained SSHI harvester, we attached a piezoelectric sensor to the vibrating structure in addition to the piezoelectric transducer. Piezoelectric transducer is used for generating electrical energy, and piezoelectric sensor is used for measuring structural displacement. When we install the harvesting device to existing structures, the mounting of those two elements is troublesome. Thus, this paper proposes a sensor-less vibration observation method that measures the voltage of piezoelectric transducer. We develop three observers depending on the three state of harvesting circuits. The observers work alternately and estimate the state values gradually. Using this observation method, the controller of switching energy harvesting can obtain the information of modal displacement, modal velocity, and piezoelectric charge. This paper presents the construction of those three observers, and numerical simulation of them. The simulation reveals that the vibration state can be detected with the proposed observation method by measuring the piezoelectric voltage. It suggests the sensor-less harvesting device can be constructed with this method.