An optimized tuned mass damper/harvester device

Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure. Traditionally, this energy is dissipated through the devices as heat. In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated. The energy-dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy. That gives the possibility of controlled damping force whilst generating useful electrical energy. Both analytical and experimental results from an adaptive and a semi-active tuned mass damper/harvester are presented. The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression

Optimum resistive loads for vibration-based electromagnetic energy harvesters with a stiffening nonlinearity

The exploitation of nonlinear behavior in vibration-based energy harvesters has received much attention over the last decade. One key motivation is that the presence of nonlinearities can potentially increase the bandwidth over which the excitation is amplified and therefore the efficiency of the device. In the literature, references to resonating energy harvesters featuring nonlinear oscillators are common. In the majority of the reported studies, the harvester powers purely resistive loads. Given the complex behavior of nonlinear energy harvesters, it is difficult to identify the optimum load for this kind of device. In this paper the aim is to find the optimal load for a nonlinear energy harvester in the case of purely resistive loads. This work considers the analysis of a nonlinear energy harvester with hardening compliance and electromagnetic transduction under the assumption of negligible inductance. It also introduces a methodology based on numerical continuation which can be used to find the optimum load for a fixed sinusoidal excitation. </jats:p

Numerical continuation in a physical experiment: investigation of a nonlinear energy harvester

In this paper, we demonstrate the use of control-based continuation within a physical experiment: a nonlinear energy harvester, which is used to convert vibrational energy into usable electrical energy. By employing the methodology of Sieber et al. (2008, “Experimental Continuation of Periodic Orbits Through a Fold,” Phys. Rev. Lett., 100(24), p. 244101), a branch of periodic orbits is continued through a saddle-node bifurcation and along the associated branch of unstable periodic orbits using a modified time-delay controller. At each step in the continuation, the pseudo-arclength equation is appended to a set of equations that ensure that the controller is noninvasive. The resulting nonlinear system is solved using a quasi-Newton iteration, where each evaluation of the nonlinear system requires changing the excitation parameters of the experiment and measuring the response. We present the continuation results for the energy harvester in a number of different configurations.</jats:p

Synthesising load impedance to frequency-tune an electro-mechanical vibration energy harvester

Energy harvesters based upon resonant mass-spring-damper systems can only generate useful power over a narrow range of excitation frequencies. This is a significant limitation in applications where the vibration source frequency changes over time. In this paper an active electrical load is presented which can overcome the bandwidth limitations by parametrically tuning the overall harvester system. The electrical tuning technique synthesizes an optimum reactive load with high-efficiency switch-mode electronics, which also provides rectification, feeding power harvested into a DC store. The method is shown to be effective at increasing the power frequency bandwidth of resonant type harvesters, and offers the capability of autonomous operation. The theoretical basis for the technique is presented, and verified with experiment results. The paper illustrates the challenges of implementing the power electronic converter for a low quiescent power overhead and in choosing the control architecture and tuning algorithms.</jats:p