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Structural health monitoring incorporates sensing, data management, and statistical modeling to measure the performance of a host structure. Sensing systems play a lead role in this paradigm by performing actuation, data acquisition, and communication in order to enable the implementation of a health monitoring strategy. In many applications power provision can become a limiting factor, as the conventional strategy for wireless networks is a battery. Even batteries require replacement, as their power capacity often does not exceed the intended long-term sensing requirements of their host structures.
Energy harvesting has emerged as a potential class of powering solutions for remote sensing applications. The energy harvesting process can be described in three stages: 1) energy transduction (supply), 2) power conditioning and management (storage), and 3) sensing and communications (demand). Conventional examples of energy harvesting strategies would be photovoltaic cells (solar energy), linear resonators / inertial generators (vibration energy), and thermoelectric generators (thermal energy), to name a few.
Our initial research primarily focused on novel approaches to energy harvesting by exploiting failure modes that have potential to generate significant amounts of energy. An example of this is the corrosion-based energy harvester pictured in Figure 2. This design extracts energy from the electrochemical process of corrosion by using seawater as an electrolyte to drive the galvanic process. Seawater and oxygen diffuse through the concrete shell to the electrodes made of carbon and magnesium whereby the chloride ions present in the seawater begin to strip free surface electrons from the magnesium (anode). The electrons migrate to a lower potential at the carbon rod (cathode) resulting in a process that emulates a common battery. The output power generated by this design serves two sensing purposes: 1) the fact that power is being generated is a rudimentary form of corrosion detection, and 2) the energy harvested can be used to power sensing electronics mounted to the host structure.
Our current research involves the the investigation of adaptive bistable mechanical oscillators for broadband vibration energy harvesting. Several studies over the past few years have highlighted the advantages of bistable oscillators over conventional linear resonators for applications of vibration energy harvesting. These advantages, while promising, have garnered increased attention to the study of nonlinear oscillators for broadband energy harvesting schemes. The approach we are taking involves real-time control of the boundary conditions that enable the bistable oscillation regime in order to increase the nonlinear resonant frequency bandwidth of the energy harvesting device. In short, the goal of this initiative is to develop a control strategy that generates a net-positive energy capture relative to the current state-of-the-art resonant energy harvesting platforms.