A novel kind of active resonator absorber and the simulation on its control effort

Abstract

In this research, the advantages and limitations of an adaptive-passive vibration absorber (APVA) are analyzed in detail. Based on the analysis, a novel kind of active vibration absorber is proposed. It can be considered as the integration of APVA and active resonator absorber (ARA), so their advantages are inherited. Its control effort is theoretically analyzed. The results show that it needs much smaller control force than ARA.

Introduction

Dynamic vibration absorbers (DVA) have been successfully used to attenuate the vibration of many structures. The DVA usually consists of a mass attached to the structure to be controlled through a spring-damper system. It can be tuned to suppress vibration at single frequency harmonic excitation. The principal drawback of tonally tuned absorbers is that they require very low absorber damping to achieve good performance, which causes the effective bandwidth to be quite small. When the excitation frequency is unsteady or varying, traditional DVAs will become ineffective and potentially increase the base vibration.

In recent years, semi-active and active–passive vibration absorbers have been proposed to suppress harmonic excitations with time-varying frequency [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. A semi-active vibration absorber achieves vibration control by changing its dynamic parameters, such as the stiffness or damping. Some advantages of semi-active control are that it requires less power, costs less, and has reduced complexity versus active systems, while being nearly as effective. Semi-active vibration absorbers can be separated into several types: variable stiffness through mechanical mechanisms [1], [7], [10], [14], [15] or using controllable new materials [5], [9], [12], [20], variable inductor connected in series with the piezoelectric patch for piezoelectric absorbers [8], [16], [17], [18], [19]. A lot of adaptive vibration absorbers with variable stiffness have been proposed and verified experimentally and shown that these devices can effectively suppress the vibration of the primary structure. However, when the exciting frequency deviates from the resonant frequency of the primary structure, the effect of vibration absorber reduces obviously [7], [8]. Furthermore, semi-active vibration absorber behaves as a passive one when its stiffness or damping is fixed, so it is not suitable for multi-frequency or broad-band excitation. In addition, these semi-active implementations have had difficulty in achieving fast and accurate tuning [16]. Active–passive vibration absorber is the integration of a passive vibration absorber (PVA) with a force actuator. Active control allows for the direct control of the absorber's transmitted force as well as modifying the dynamic properties of the device. This is achieved using the force actuator that essentially modifies the effective stiffness and damping of the absorber. As a result of the direct control of the absorber's transmitted force, the absorber can suppress the vibration of multi-frequency or broad-band excitation and tune rapidly with high accuracy. The active absorbers with different actuators and control laws have been investigated and implemented [2], [3], [4], [6], [11], [13]. It has advantages such as large bandwidth, high vibration reduction level and fine robustness. But it needs large power requirement.

As active–passive absorber, the delayed resonator and active resonator absorber (ARA) have been investigated by many researchers [3], [6], [11]. Both of them consist of a proportional position or acceleration feedback and the only difference between them lies in that the feedback of the delayed resonator has a time delay. The reason they are called as resonator is that resonance is created in these absorbers by using the feedback control to place the dominant characteristic roots of absorber subsection on imaginary axis. In fact, these devices are similar to auto-tuning un-damping vibration absorbers, whereas the performance is realized only by the active force. Although they are effective for wide band frequency excitation, they still need large control effort. In this paper, a novel implementation of tunable vibration absorber is proposed. It is called an adaptive active resonator absorber (AARA). The AARA consists of two parts. The first part is an adaptive-passive vibration absorber (APVA) with variable stiffness, which can be adaptively tuned to the correct frequency. The second part is an actuator which provides control force to cancel the damping force applied on the absorber, hence leading to resonance. Once the AARA becomes resonant, it create the perfect vibration absorption at given frequency. The concept of the AARA is similar to the adaptive active–passive piezoelectric absorber [16], [17], [18], [19], but the proposed absorber is spring-mass system which has quite different properties such as its configuration, system equation and applied field. The adaptive active–passive piezoelectric absorber is limited to vibration control of structure with elastic deformation, whereas the proposed absorber has no limitation and can also be applied to vibration reduction of rigid body or structure with no elastic deformation. In Section 2, the advantages and limitations of an APVA are analyzed in detail. In Section 3, the principle of the AARA is introduced. The control effort of AARA and ARA are theoretically analyzed in Section 4.