Harvesting energy from ambient energy sources has received much recent attention as an alternative • Investigate the effect of the SSDCI circuit on an aeroelastic energy harvester in terms of energy power source for remote, stand-alone systems. In contrast to batteries, energy harvesters have a longer extraction performance and aerodynamic behavior lifetime and lower environmental impact [1]. Piezoelectric materials in particular have been a promising • Analytically and experimentally model the relationship between energy extraction efficiency and (1) means for vibration energy harvesting because of their high power density and mechanical simplicity the timing of the switch closing and (2) the length of time the switch is closed [2]. • Design and implement a self-powered SSDCI system • Determine under what operating conditions the SSDCI circuit becomes less energy efficient due to the energy consumption of its additional circuit components

Ambient Piezo Energy Energy Power Control Sensor Energy Harvester Storage Conditioning Intelligence

Actuator Overall Energy Harvesting System Model Mechanical displacement The energy harvesting device is just one component of an overall energy harvesting system. Energy One of the biggest challenges with the Pulse to close switch harvesting devices extract ambient energy from sources like wind or solar. This extracted energy is then synchronized switching technique is stored in a supercapacitor or similar element for later use. Before this stored energy can be used to performing real-time peak detection of the power a sensor or actuator, it must be conditioned so that the voltage and current is regulated. vibration cycle. For an aeroelastic energy Furthermore, in order to control the activity of a sensor or actuator, a microcontroller is generally harvester, both the frequency and amplitude of needed. motion are variable and therefore the peak detector must be robust. Vibration cycle vs. switch pulse timing Traditional piezoelectric energy harvesting devices focus on extracting wind energy from a vibrating host structure. In contrast, aeroelastic energy We have achieved a real-time peak detector circuit by using a laser vibrometer, operational amplifier (op harvesters focus on harvesting energy from flowing fluids, such as amp), and comparator. The laser vibrometer translates the energy harvester’s vibration cycle into a wind. Therefore aeroelastic energy harvesters involve a three-way synchronized sinusoidal voltage wave. This voltage sine wave is then differentiated and fed into a coupling of structural, electrical, and fluid dynamics. comparator which detects the zero-crossings of the differentiated signal, corresponding to the peaks of the original vibration cycle. The output of the comparator is fed into a microcontroller, which is able to Aeroelastic energy harvester generate a controllable pulse that closes the switch.

Laser Differentiating Pulse to Energy harvesting circuits traditionally store energy by continuously charging a storage element, like a Comparator Microcontroller close switch capacitor. Other energy harvesting circuits utilize a controllable switch in order to maximize the energy Vibrometer Op Amp extraction efficiency. Instead of continuously charging a storage element with the energy stored in the Peak detector and pulse trigger schematic piezoelectric capacitance every vibration cycle, synchronized switching techniques use a switch in the energy harvesting circuit that is closed for a short time interval when the system displacement is at its Future work includes: peak. Thus, the switch is open for the majority of the vibration cycle and only closed for a short time • Coupling the peak detector and pulse trigger circuit to the SSDCI circuit during peak displacement. The synchronized switching and discharging to a storage capacitor through • Experimentally quantifying the increase in energy extraction of the synchronized switching an inductor (SSDCI) technique is one type of synchronized switching circuit. The SSDCI technique has technique over the continuous extraction method been shown to charge a storage capacitor over five times faster than the direct, continuous charging • Experimentally investigate changes to the amplitude and frequency of the flutter limit cycle technique [3].

[1] Lefeuvre, E., Badel, A., Richard, C., Guyomar, D., 2005, “Piezoelectric Energy Harvesting Device Optimization by Synchronous Electric Charge Piezoelectric circuit Piezoelectric circuit Extraction.” Journal of Intelligent Material Systems and Structures 16:865-876. equivalent equivalent [2] Anton, S., Sodano, H., 2007, “A review of power harvesting using piezoelectric materials (2003-2006).” Smart Materials and Structures 16:R1-R21. [3] Wu, W.J., Wickenheiser, A.M., Reissman, T., Garcia, E., 2009, “Modeling and experimental verification of synchronized discharging techniques for Continuous charging circuit schematic [3] SSDCI circuit schematic [3] boosting power harvesting from piezoelectric transducers.” Smart Materials and Structures 18:1-14.