We consider the performance of a vibration based energy harvester with realistic topologies for the electrical
circuit, including power conditioning through a rectifier. Specifically we apply a novel perturbation approach to
describe the time-varying power harvested in the system, including a rectifier in the circuitry. This approach
considers the full electromechanical coupling between the mechanical and electrical components, including the
amplitude and phase of the mechanical response. The resulting analysis is able to describe the behavior of the
system as the mechanical response is detuned from resonance by the electrical load. In addition, the charging of the circuit over time is also captured by the analysis. Finally, the analytical results are compared against the numerical simulations of the original equations of motion to verify the analytical approach.
Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape
memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature
constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to
develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature
shape memory alloys (HTSMAs) is Ni19.5Ti50.5Pd25Pt5. Recent work has shown that this material is capable
of being used in operating environments of up to 250°C. This material has been shown to have very useful actuation
capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based
on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy,
such as springs. Thus, characterization of Ni19.5Ti50.5Pd25Pt5 springs, including their mechanical response and how
variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or
training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the
benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design
considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter
engine.
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