MS13.1: Energy Transfer and Harvesting in Nonlinear Systems

This study presents a small-scale hybrid test setup for the investigation of various vibration control strategies to limit the motion of wind-turbine generators during the installation phase. The control strategy is incorporated virtually (i.e., the response of the additional degrees of freedom is simulated virtually) and is applied on the physical structure by means of an electromagnetic actuator. A Nonlinear Energy Sink (NES) is investigated as a passive control strategy. Preliminary results show that the NES leads to a vibration reduction, but it is much less efficient than a previously proposed active mitigation strategy. The hybrid test setup described in this work can serve as a preliminary experimental investigation into the optimum vibration mitigation strategy for different applications.

Modern computers are powerful devices that have given impetus to our abilities to make discoveries in many fields of science and technology. With their ubiquitous use, the amount of energy they consume is on the rise. Current electronic computers consume energies that are orders of magnitude higher than the theoretical predicted cost, given by the Landauer Limit. The Landauer limit states that the minimum energy required to erase a bit, an operation essential for irreversible computation, at a given temperature, depends on the entropy change that occurs in the erasure. Recent experiments have verified the Landauer Limit using time-dependent potentials. This approach does not take into account the energy required to break the detailed balance and establish an arrow of time for the erasure. In this work, a theoretical nanomechanical system, that does an autonomous bit erasure, is presented and the energy cost for the bit erasure and breaking detailed balance are discussed. The system consists of two coupled nonlinear mechanical oscillators, a bistable buckled beam that acts as the “bit” and a heavy mass, here called the “power clock”, that provides energy and sets the time scale for the erasure. The system is studied using the framework of stochastic thermodynamics. The simulation results show that the system can do a bit erasure using 250 kT of energy (1 kT = 4.1 x 10^-21 J) compared to the 3900 kT of energy used to do a logical operation in modern electronic computers.

The dynamics of a linear oscillator undergoing high-frictional impact is investigated. The system is a core model of brake pads or rotor-stator in contact. First, a practical mathematical model for the impact is derived, exploiting Newton's coefficient of restitution, conservation of the angular momentum, and the Coulomb friction model. This leads to an apparent coefficient of restitution, which can be larger than one, implying that the impact can generate energy. This phenomenon can trigger self-excited oscillations. Then, a bifurcation analysis is performed, leading to the definition of a critical parameter value, separating global and local stability regions of non-impacting solutions. Finally, the effect of the addition of a harmonic excitation is analyzed, which leads to more involved dynamical phenomena.

This article studies a hybrid nonlinear vibration absorber. It consists of a passive part (a Nonlinear Energy Sink) and an active part (electromagnetic transducer). This work aims to tune the internal properties of the NES in real time, such that the activation threshold and effective energy pumping mechanism are maintained under varying operating conditions. To this end, numerical tools are developed for the design of suitable control laws which are then validated on a structure with varying parameters.