A tunable magneto-rheological fluid-filled beam-like vibration absorber

Abstract

Tuned vibration absorbers (TVAs) are often used to suppress unwanted vibrations. If the excitation frequency is time harmonic but the frequency changes with time, it is desirable to retune the TVA so that the natural frequency of the TVA always coincides with the excitation frequency. One way of achieving this is to adjust the stiffness of the TVA. The key challenge is to change the stiffness quickly in real time. In this paper a magneto-rheological (MR) fluid in its pre-yield state is used as the core of a three-layer beam-like TVA. The shear stiffness of the MR fluid is adjusted by varying the magnetic field to which it is exposed by changing the current supplied to the electromagnets. Hence the stiffness of the TVA can be varied. The vibration characteristics of the TVA as a function of the magnetic field strength are predicted using a finite element model together with an empirical model for the shear modulus of the MR fluid and a model for the magnetic field applied to the fluid. An MR fluid-filled TVA was manufactured and tested to validate the predictions. This TVA design allows the natural frequency to be changed by about 40%.

Phase based stiffness tuning algorithm for a magnetorheological elastomer dynamic vibration absorber

“…where V a and A a are the absolute velocity and the absolute acceleration of the DVA mass respectively; V p and A p are the absolute velocity and the absolute acceleration of the primary system respectively. From equation (8), the following equation (9) holds.…”

“…Velocity signal control for the phase based stiffness tuning: (a) displacement response of the primary system; (b) natural frequency of the MRE DVA.suppressed quickly. Similar results could be obtained when the excitation frequency was changed to 20 Hz at a time of 35 s. Therefore, with the help of the phase based stiffness tuning algorithm, the MRE DVA can track the excitation frequency quickly and suppress the vibration of the primary system.According to equations(8) and(9), the phase difference can be obtained from acceleration signals, velocity signals or displacement signals. Which one is chosen depends on which signals are the easiest to obtain compared to the other two in engineering applications.…”

Interval Type-2 Fuzzy Vibration Control of Multiple-degree-of-freedom Structure Using Shape-memory-material Absorber

“…Among all ATVA designs, smart materials are usually used as the controllable actuator for changing the vibration behavior of the main structure. (12)(13)(14) Some ATVA designs incorporate the SMA structural member to achieve vibration control; however, the problem of transformation nonlinearity due to hysteresis is usually encountered. The exact cause is that the forward and backward martensitic transformations occur along different actuation routes for most SMAs.…”

A tuned vibration absorber constituted of shape memory alloy wires for vibration reduction of platform structures: design and implementation

“…The adjustable characteristic can be realized by altering the equivalent stiffness which directly influences the natural frequency. Since conventional materials such as steel, copper and aluminium with fixed physical properties cannot meet the requirement of adjustable nature, intelligent materials with different kinds of adjustable material properties were introduced to design or applied to the TVA in previous literatures, such as viscoelastic solids [6,7], shape memory alloys (SMAs) [8][9][10][11], ferromagnetic shape memory materials [12], piezoelectric materials [13,14], electro-rheological fluid [15,16], magnetorheological fluid [17][18][19] and shape memory polymer [20] etc. However, most designs only employ single tuned frequency in vibration reduction.…”