Optimal Vibration Control and Energy Scavenging Using Collocated Nonlinear Energy Sinks and Piezoelectric Elements

This paper presents an optimal design for a system comprising multiple nonlinear energy sinks (NESs) and piezoelectric-based vibration energy harvesters attached to a free–free beam under shock excitation. The energy harvesters are used for scavenging vibration energy dissipated by the NESs. Grounded and ungrounded configurations are examined, and the systems parameters are optimized globally to maximize the dissipated energy by the NESs. The performance of the system was optimized using a dynamic optimization approach. Compared to the system with only one NES, using multiple NESs resulted in a more effective realization of nonlinear energy pumping particularly in the ungrounded configuration. Having multiple piezoelectic elements also increased the harvested energy in the grounded configuration relative to the system with only one piezoelectric element.

Study on Nonlinear Energy Pumping of the Vibration System with Cubic Damping Absorber

The nonlinear energy pumping in a two-degree-of-freedom system comprising a damped linear oscillator coupled to cubic damping absorber is studied. It is verified that the nonlinear pumping energy can be performed by cubic damping absorber besides cubic stiffness absorber. The resonance capture is verified by time-frequency analysis (Hilbert Transform). The energy pumping efficiency is put forward for quantitative analysis, and the optimal parameters of system are obtained. The amplitude of main oscillator can be attenuated in a very short duration. The result may be significative for engineering implementation.

Study on Dynamics of a Nonlinear Damping Absorber Coupled to the Linear System

The dynamics of a two degree-of-freedom (DOF) system consisting of a linear system coupled with a quadratic damping vibration absorber is studied. The nonlinear energy pumping phenomenon is verified by simulation and analyzed by Hilbert Transform. Performance of the quadratic damping absorber that is able to absorb vibration over a broad range of frequency (nonlinear energy sink, NES) is studied, and the results are compared with that of the classical linear vibration absorber. The relationship between parameters and performance of the absorber is analyzed, that is significant for engineering application.

On an Active Control for a Structurally Nonlinear Mechanical System, Taking Into Account an Energy Pumping

The purpose of this work is to investigate the control of the oscillations and the suppression of vibrations in damped and coupled oscillators. In this sense, we look into the potential of using a nonlinear energy sink in combination with an optimal linear control for nonlinear system to suppress structure vibrations under an impact load. As a result, we obtain that the nonlinear energy pumping (a one-way passive and almost irreversible energy flow from a linear main system to a nonlinear attachment that acts as a nonlinear energy sink) can be enhanced with the help of appropriate active control. The numerical results show the effectiveness of the approach presented here.

Virtual Reality Simulation of Active Car Suspension System

This paper presents the design of a Nonlinear Energy Sink (NES) controller and its application to active sus-pension systems in the Virtual Reality Environment. In this en-vironment, the design engineers are immersed in an audio-visually coupled tele-operated environment whereby direct in-teraction with and control of the design process is achieved in real time. In this manner, the behavior of synthetic models of the full car can be monitored by literally walking around the car and adjusting the design parameters of the suspension as needed to ensure optimal performance while satisfying design and operational requirements. The control actuators which provide forces equivalent to nonlinear stiffness and damping elements are attached to the vehicle in order to actively isolate it from road excitation. The effect of the parameters of the NES controller on the vehicle performance is studied both in the frequency and time domain. The effectiveness of the NES controller is validated by numeri-cal simulation. The robustness of the nonlinear energy pumping process is studied by varying the magnitude of road excitation. The simulation results in the Virtual Reality Environment show that under certain conditions, the nonlinear energy pumping can be induced and significant vibration isolation can be achieved. The performance of vehicle including the ride com-fort and road holding capability can be improved significantly. When the magnitude of road excitation is increased, the capaci-ty of the NES to absorb energy from the main system is also enhanced. This is very important to achieve vibration isolation objectives. The virtual reality simulation results also show that the nonlinear NES controller performs better than the classical LQR controller particularly as the road condition becomes worst.

SHOCK ISOLATION THROUGH PASSIVE ENERGY PUMPING CAUSED BY NONSMOOTH NONLINEARITIES

We investigate shock isolation designs based on nonlinear energy pumping caused by nonsmooth stiffness elements. In particular, we numerically study the shock isolation properties of a primary linear system of two coupled nonconservative oscillators with weakly coupled attachments possessing clearance nonlinearities. Under shock excitation the nonlinear attachments (termed nonlinear energy sinks — NESs) can be designed to absorb a significant portion of the input energy, thus enhancing the shock isolation performance of the primary system. In contrast to the classical linear vibration absorber whose operation is restricted to narrowband frequency ranges, the NESs are capable of efficiently absorbing energies caused by transient broadband disturbances, a feature that facilitates their implementation in practical applications. Moreover, the nonsmooth nonlinearities considered in this work are easily implementable since they are realized by means of linear stiffness elements.

Steady-State Dynamics of Smooth and Non-Smooth Systems With Strong Nonlinearities

The nonlinear energy sinks (NESs) with strong essential stiffness nonlinearities have been shown to result in vibration isolation in the studied system. In comparison, we also studied the steady-state dynamic response of a system with its smooth high-order odd nonlinearity replaced with the best fitted nonsmooth “clearance nonlinearity”. The analysis was based on the complexification technique and the separation of the dynamic terms into the “slow-varying” and the “fast-varying” components. We found that the steady-state behavior of a system with the non-smooth NES resembles that of the system with the smooth high-order nonlinearity, preserving the nonlinear energy-pumping feature. This finding paves the way for constructing practical NESs and applying them to practical vibration-isolation problems.

Shock Isolation Through Passive Energy Pumping in a System With Piecewise Linear Stiffnesses

We investigate shock isolation designs based on nonlinear energy pumping caused by piecewise stiffness elements. In particular, we numerically study the shock isolation properties of a primary linear system of two coupled non-conservative oscillators with weakly coupled attachments possessing clearance nonlinearities. Under shock excitation the nonlinear attachments (termed nonlinear energy sinks – NESs) can be designed to absorb a significant portion of the input energy, thus enhancing the shock isolation performance of the primary system. In contrast to the classical linear vibration absorber whose operation is restricted to narrowband frequency ranges, the NESs are capable of efficiently absorbing energies caused by transient broadband disturbances, a feature that facilitates their implementation in practical applications. Moreover, the non-smooth nonlinearities considered in this work are easily implementable since they are realized by means of linear stiffness elements.