Real-time control of both stiffness and damping in an active vibration neutralizer

Abstract

Recent improvements to the vibration neutralizer have involved the incorporation of a variable-stiffness device so that the natural frequency can be adjusted. The device can then track an excitation frequency that is varying slowly with time. This paper describes a neutralizer where both damping and stiffness in the neutralizer are adjustable, so that the performance of the device can be improved in addition to its tracking capability. An experimental investigation is described in which the feasibility of real-time control of both stiffness and damping properties was assessed. A fuzzy controller was designed to adjust the resonance frequency of a beamlike neutralizer by changing its geometry, and to adjust the gain in a velocity feedback loop to reduce the damping in the device. The dot product of the complex velocity vectors of the neutralizer and host structure was used as an indicator of the tuning error. Damping was controlled by a fuzzy rule base, which used the rms level of neutralizer and host structure velocities as errors. Significant improvements in the vibration attenuation of a host structure were achieved compared with a passive neutralizer.

Some Recent Developments in Adaptive Tuned Vibration Absorbers/Neutralisers

“…This had the advantage of having low damping and hence could potentially be more effective than the design described by Longbottom et al [7]. This design was modified by Brennan [3], and developed by Kidner and Brennan [11][12][13] with a system to control both stiffness and damping. This device involved a change in shape to control the stiffness, but the actuation mechanism was relatively slow to operate.…”

“…(1) 13cm absorber mass where d is the thickness of an individual beam and h < d. It can be seen that this design is attractive in that only a relatively small movement is required to achieve a reasonable change in natural frequency. Kidner and Brennan [12,13], modified this design using two perspex beams that were connected by tape at the ends and were allowed to bend in the centre as shown in Fig. 2.…”

<title>Survey of state-of-the-art vibration isolation research and technology for space applications</title>

“…Kidner and Brennan used a fuzzy controller to vary both stiffness and damping of a vibration absorber, allowing both improved performance and tuning of the absorber. 117 Jalili explored a combined semi-active/active combination where the semi-active system is tuned, the active system is changed adaptively, or both systems are changed together. 118 Finally, Jalili has also considered semi-active control for vibration isolation for a 1DOF system.…”

Active-Adaptive Vibration Absorbers and its Vibration Attenuation Performance

“…To solve this problem, much attention has been concentrated on the combination of ATVA and AVA. Kidner and Brennan [6] designed an active vibration neutralizer to control stiffness and damping in real time. It used the piezoelectric elements as the active element to control the damping.…”