Active Vibration Isolation Using an Electrical Damper or an Electrical Dynamic Absorber

Abstract

Abstract-This paper describes a theoretical and experimental study to show how an electrical damper or an electrical dynamic absorber, implemented using an electromagnetic actuator and an accelerometer, can control vibration transmission through a vibration isolator. The electrical damper is realized by feeding back the equipment velocity to the actuator with constant gain. The electrical dynamic absorber is realized by feeding back the equipment acceleration through a second-order low-pass filter. Because it is found that the plant on a flexible base is asymptotically similar to that on a rigid base, the optimal parameters of the control filter are determined analytically, independent of the base dynamics. Experimental results show that the electrical dynamic absorber has a similar performance to the electrical damper. The maximum reduction in transmitted vibration achieved was about 38 dB for both methods. It is also shown that the electrical dynamic absorber is more robust to undesirable dynamics outside the control bandwidth. Another advantage of the electrical dynamic absorber is that it does not require an integrator to transform acceleration into velocity.Index Terms-Acceleration-position feedback (APF), direct velocity feedback (DVFB), electrical damper, electrical dynamic absorber, vibration control.

An overview of the development of intelligent materials and active vibration isolation systems for vehicles

“…A kind of active passive micro vibration isolation system and its vibration transfer rate curve in the frequency domain [5] are shown in Figure 1 and Figure 2. Of these: passive stiffness is used to suppress medium and high frequency vibration disturbances, and primary dynamics is used to isolate low frequency vibration disturbances [6][7][8].…”

“…Figure 2. Vibration Transmission Velocity Curve.Of these: passive stiffness is used to suppress medium and high frequency vibration disturbances, and primary dynamics is used to isolate low frequency vibration disturbances[6][7][8].…”

Optimal and robust modal control of a flexible structure using an active dynamic vibration absorber

“…This block diagram is more precisely presented in figure 1(b) by expanding the terms inside h, where K a and K s are respectively the amplification gains for the actuator and the sensor, T act and T sen are respectively the sensitivities of the actuator and the sensor, P(jω) is the electromechanical plant, K d is the gain of the (digital or analog) electrical controller C(jω), and LPF denotes an optional anti-aliasing lowpass filter in the case of digital implementation. The devices K a , K s , T act , T sen , and LPF are usually frequency-dependent with time delays [3,11] but this dependence is omitted here for brevity of notation. The plant response after control is given by…”

“…An alternative modal controller, called the active dynamic vibration absorber (ADVA) [11], is employed in this paper to reduce a particular single vibration mode of a flexible structure selectively or multiple modes simultaneously. Dynamic vibration absorbers are well-known classical passive vibration control devices [12], and both mechanical [13] and piezoelectrical forms [14] have been used for many years.…”

“…In principle the ADVA also uses the mechanism of the passive dynamic vibration absorber such that it works effectively as a skyhook damper around the resonance region of a particular TM and less effectively otherwise. Unlike DVFB and PPF, the ADVA is thus very sensitive to the dynamics of the TM only, and is less sensitive to lower and higher order modes [11]. A simple analytical method is presented in this paper to design a modal control filter that is optimal in that it maximally flattens the mobility frequency response of the TM (i.e., modal velocity response to a generalized force) as well as robust in that it works within a prescribed maximum control spillover of 2 dB at all frequencies.…”