Implementation and Testing of an Elastic Strain Powered Wireless Sensing System for Energy-Autonomous Applications

Abstract

This paper presents implementation and testing of an elastic strain powered wireless sensing system for energyautonomous applications. The system harvests strain energy from a vibrating structure and convert it into usable electrical energy for powering sensors and a wireless communication node. Typical in-flight vibration frequency and strain levels on the bottom side of the aircraft wing's root were investigated for testing the performance of the system. Major concerns of the implemented system are the amount of harvested power, in the usable range of milliwatts, and the low power consumption energy-flow management for data sensing and transmitting. Such results arise from the use of flexible piezoelectric macrofiber composite (MFC) bonded as energy generator to both an aluminum and a composite substrate, and from the integration of a new Energy-Aware Interface (EAI). The harvested power is between 0.5-12 mW under low and non-resonant vibrations of 2.5-10 Hz and 480-1170 μstrain peak-to-peak. The waiting time between two consecutive transmissions was measured around 0.4 s under 1170 μstrain peak-to-peak excitation at 10 Hz. Such achievement shows strong capability to approach self-powered continuous monitoring. The system has potential of being used to harvest strain energy from the vibrations of aircraft in active service for powering an on-board wireless sensing node for Structural Health Monitoring (SHM).

Strain Energy Harvesting Powered Wireless Sensor System Using Adaptive and Energy-Aware Interface for Enhanced Performance

“…The sizes of storage capacitors used in these studies are also small at less than 2 mF, which can only keep the sensor on for a few hundreds of milliseconds at most [9], [11]. Such a short turn-on time is usually insufficient especially for real-world applications such as structural health monitoring which requires monitoring of low to medium frequency vibrations using an accelerometer.…”

“…The presented systems have common features, which include (1) charging up a storage capacitor using the SEH via a rectifier which is non-adaptive and (2) an energy-aware interface (EAI) that keeps the WSS off so that energy from the SEH can be accumulated in the storage capacitor and only allows the WSS to draw current from the storage capacitor when the stored energy is sufficiently high. The reported EAIs have low current consumption of 1.19 μA [9] or lower [11] but the SEH harvested less than 1 mW [9], [11] even when a peak strain loading of 300 με at 180 Hz was applied because of the non-adaptive interface used.…”

“…PEHs using flexible piezoelectric materials such as polyvinylidene fluoride (PVDF) [6] and macro fiber composite (MFC) [7] are particularly suitable as a strain energy harvester (SEH) because they can be bonded onto host structures of different shapes [7], [8], where the strain experienced by the host structures due to impact or vibration can be directly transferred to and converted by the SEH into electrical energy at off-resonant. The power that can be harvested is proportional to the vibration frequency and has a quadratic relationship with the experienced strain level [9].…”

“…There are only a few whole system integration studies on SEH powered WSS, most notably by Giuliano et al [9] and MicroStrain Inc. [11]. The presented systems have common features, which include (1) charging up a storage capacitor using the SEH via a rectifier which is non-adaptive and (2) an energy-aware interface (EAI) that keeps the WSS off so that energy from the SEH can be accumulated in the storage capacitor and only allows the WSS to draw current from the storage capacitor when the stored energy is sufficiently high.…”

“…This means that (1) there is a mismatch between the energy generated by the harvesters and the energy demanded by the WSNs to perform required tasks, and (2) power delivered to the end devices is extremely low because of the lack of adaptation functionality of the simple interfaces, leading to an extremely low efficient operation. A typical example is that when a peak strain loading of 305 με at Strain Energy Harvesting Powered Wireless Sensor System Using Adaptive and EnergyAware Interface for Enhanced Performance Zheng Jun Chew, Member, IEEE, Tingwen Ruan, and Meiling Zhu, Member, IEEE W > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 2 2.5 Hz was applied, a MFC connected to its optimal resistive load can generate more than 1 mW of power, but when it was connected to a storage capacitor together with a WSS via a rectifier, only around 0.28 mW of power was generated [9]. This is because the simple interface of the rectifier itself is without adaptation functionality to variable vibrations and variable loads, and thus not able to harvest the power generated by the MFC which is subject to variable vibrational conditions and variable connected loads effectively.…”