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

Abstract

Abstract-This paper presents a wireless sensor system (WSS) powered by a strain energy harvester (SEH) through the introduction of an adaptive and energy-aware interface for enhanced performance under variable vibration conditions. The interface is realized by an adaptive power management module (PMM) for maximum power transfer under different loading conditions and an energy-aware interface (EAI) which manages the energy flow from the storage capacitor to the WSS for dealing with the mismatch between energy demanded and energy harvested. The focus is to realize high harvested power and high efficiency of the system under variable vibration conditions, and an aircraft wing structure is taken as a study scenario. The SEH powered WSS was tested under different peak-to-peak strain loadings from 300 to 600 µε and vibrational frequencies from 2 to 10 Hz to verify the system performance on energy generation and distribution, system efficiency, and capability of powering a custom-developed WSS. Comparative studies of using different circuit configurations with and without the interface were also performed to verify the advantages of the introduced interface. Experimental results showed that under the applied loading of 600 µε at 10 Hz, the SEH generates 0.5 mW of power without the interface while having around 670 % increase to 3.38 mW with the interface, which highlights the value of the interface. The implemented system has an overall efficiency of 70 to 80 %, a long active time of more than 1 s, and duty cycle of up to 11.85 % for vibration measurement under all the tested conditions. Index Terms-adaptive power management, energy-aware interface, piezoelectric energy harvesting, strain energy harvester, wireless sensor node.

Threshold Voltage Control to Improve Energy Utilization Efficiency of a Power Management Circuit for Energy Harvesting Applications

“…A macro fiber composite (MFC) was used as the energy harvester [4]. A cyclic peak-to-peak strain loading of 500 µε with the frequency of 10 Hz was applied onto the MFC by using an Instron testing machine.…”

“…The EFCIs can be low-dropout (LDO) regulators [8], DC-DC converters [9] or any custom-designed circuitries [3,7,10] with two threshold voltages to turn-on and turn-off the WSNs, respectively. The threshold voltages are usually set based on the operating voltage range of the WSNs [3,4,7]. The power converters are usually set to maintain their output voltage at a fixed value and are used to charge up the energy storage capacitor towards the preset value [2,4,7].…”

“…The threshold voltages are usually set based on the operating voltage range of the WSNs [3,4,7]. The power converters are usually set to maintain their output voltage at a fixed value and are used to charge up the energy storage capacitor towards the preset value [2,4,7]. It should be noted that power converters usually have low efficiency when their output power is low [11,12].…”

“…Therefore, a power management circuit (PMC) is required to manage the energy from the energy harvesters and provide electrical energy in a usable form to the WSNs. The harvested energy is usually stored in an energy storage device such as a capacitor and is released to the WSNs once the capacitor voltage reaches a specific threshold voltage, as controlled by an energy flow control interface (EFCI) [3,4]. Although tremendous progress has been achieved in improving the performances of the PMCs by including features such as maximum power point tracking [5], power extraction [6], very low start-up voltage and low power consumption [7], no investigation has been done on the energy flow control interface to improve the energy utilization efficiency.…”

“…Block diagram of: (a) Common architecture of PMC where the optional circuit can be a rectifier; (b) Circuit used in the experiment where the EFCI is an energy-aware interface (EAI)[4].…”