Active vibration control

About: Active vibration control is a research topic. Over the lifetime, 6770 publications have been published within this topic receiving 76599 citations. The topic is also known as: active vibration damping.

Damped vibration isolation system

Abstract: An improved vibration isolation system utilizes a damped elastic structure loaded to approach a point of elastic instability to reduce the stiffness of the structure and to increase the damping. The system provides very low amplification at system resonant frequencies and effectively isolates at higher frequencies.

Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing

Abstract: Dynamic excitation from the gears generates vibration modes in the gearbox which causes radiation of unwanted structure-borne noise To reduce the noise as well as the vibration, the stiffened plate construction is frequently used for the housing, where the rib stiffener layout is the key to this design In this paper, the most effective position of stiffeners in order to reduce the vibration and noise radiation is searched and discussed The analysis considers first a plate fixed at edges and excited at its center, and then a simplified rectangular gearbox excited at the shaft bearing locations The housing of a simplified single-stage gearbox is modeled by triangular finite shell elements It is excited by a set of harmonic forces which are applied at the bearing positions The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm The vibration energy is adopted as the objective function to be minimized for the design for low vibration On the other hand, the radiated sound power is the objective function for low noise Although the noise is caused by the vibration, the optimum stiffener layout to realize low noise is not always identical to the layout that yields low vibration because of the difference in radiation efficiency This is numerically clarified first from the viewpoint of the vibration mode of a plate In the case of the design for the gearbox housing concerned, the vibration mode which causes the difference in radiation efficiency is not presented Consequently, the optimum stiffener is placed along the line from the point of excitation to a fixed point, which reduces the vibration deflection of the faces with bearings as well as the in-plane displacement of the bearings

Active Vibration Control of Gradient Coils to Reduce Acoustic Noise of MRI Systems

Abstract: Lorentz-force-induced vibrations in MRI systems cause significant acoustic noise levels during scanning, the main acoustic noise source being the vibrating gradient coil. In this paper, a novel active vibration control technique is presented to reduce vibrations of the gradient coil, and hence, achieve a reduction of acoustic noise during scanning. The active vibration control technique uses seismic masses that are actuated by means of piezo actuators to create forces on the gradient coil counteracting its vibrations. Using four seismic mass actuators, a vibration reduction of 3-8 dB at resonance frequencies is achieved, giving an overall vibration reduction of 3 dB for a typical field gradient (FE)-echo planar imaging (EPI) gradient sequence, as substantiated by measurements. Using eight actuators, an overall vibration reduction of 5 dB is predicted for this sequence.

Multi-mode vibration damping device and method using negative capacitance shunt circuits

Abstract: A novel multi-mode vibration damper is invented by using a pair of piezoelectric patches connected with negative capacitance shunt circuit units. A piezoelectric material connected with a series resistor-negative capacitor branch circuit is capable of suppressing the vibration and/or noise amplitudes in the low frequency range. The other piezoelectric material connected with a parallel resistor-negative capacitor circuit is for suppressing the vibration and/or noise amplitudes in the high frequency range. By combining two negative capacitance shunt circuit units, a multi-mode vibration damper is capable of suppressing the whole structure modes simultaneously. In order to describe the characteristic behaviors of a multi-mode vibration damper, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of a shunt damper is also described as considering a shunt voltage generated by the shunt impedance. The example results show that the multi-mode vibration damper reduces the vibration amplitudes of the vibrating system significantly across a broadband frequency range.