Control of flexural waves on a beam using a self-tuning vibration absorber
Control of flexural waves on a beam using a self-tuning vibration absorber
This thesis concerns the control of bending waves in beams using a self-tuning vibration absorber. An adaptive-passive vibration absorber, whose natural frequency is tuned automatically by adjusting the stiffness of the absorber, is developed and implemented.
The transmission and reflection of waves at an absorber attached to a beam are considered. The absorber may be located in the farfield or the nearfield of a point force and it can be positioned to control both the downstream-transmitted power and that reflected upstream. Analytical and numerical investigations are presented. If the absorber is located in the nearfield of the point force, the power transmitted past the absorber depends on four independent tuning parameters: the natural frequency of the absorber, the mass ratio, the damping of the absorber and the distance between the absorber and the point force. If the incident nearfield wave is insignificant, then this distance becomes unimportant in determining the optimal characteristics of the absorber for the control of vibration transmission. It is found that the absorber typically acts as a notch filter, controlling transmission over a narrow range of frequencies.
The case of a tunable absorber is then considered. The stiffness of such an absorber can be changed, thus affecting the tuned frequency. Two variable stiffness absorbers are designed. The stiffness of both change with temperature and electrical heating is used to change the absorber characteristics. The first absorber uses shape memory alloy as the variable stiffness element, while the second absorber employs thermoset plastics.
A closed-loop control system is developed using an appropriate error function to control the transmitted waves in real-time. The error function is found by combining the outputs of two sensors attached to the beam, one on each side of the absorber. The error function indicates the degree of mistune and whether the absorber’s stiffness needs to increase or decrease to minimise the magnitude of the transmitted power. Numerical simulations are presented. These show the effectiveness of the control system, employing the error function and an adaptive absorber, in varying the stiffness of the absorber towards the optimum value.
University of Southampton
El-Khatib, Hassan M
5c1d9a06-2f23-40c8-9ea3-ab20b5d6b5de
2005
El-Khatib, Hassan M
5c1d9a06-2f23-40c8-9ea3-ab20b5d6b5de
El-Khatib, Hassan M
(2005)
Control of flexural waves on a beam using a self-tuning vibration absorber.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis concerns the control of bending waves in beams using a self-tuning vibration absorber. An adaptive-passive vibration absorber, whose natural frequency is tuned automatically by adjusting the stiffness of the absorber, is developed and implemented.
The transmission and reflection of waves at an absorber attached to a beam are considered. The absorber may be located in the farfield or the nearfield of a point force and it can be positioned to control both the downstream-transmitted power and that reflected upstream. Analytical and numerical investigations are presented. If the absorber is located in the nearfield of the point force, the power transmitted past the absorber depends on four independent tuning parameters: the natural frequency of the absorber, the mass ratio, the damping of the absorber and the distance between the absorber and the point force. If the incident nearfield wave is insignificant, then this distance becomes unimportant in determining the optimal characteristics of the absorber for the control of vibration transmission. It is found that the absorber typically acts as a notch filter, controlling transmission over a narrow range of frequencies.
The case of a tunable absorber is then considered. The stiffness of such an absorber can be changed, thus affecting the tuned frequency. Two variable stiffness absorbers are designed. The stiffness of both change with temperature and electrical heating is used to change the absorber characteristics. The first absorber uses shape memory alloy as the variable stiffness element, while the second absorber employs thermoset plastics.
A closed-loop control system is developed using an appropriate error function to control the transmitted waves in real-time. The error function is found by combining the outputs of two sensors attached to the beam, one on each side of the absorber. The error function indicates the degree of mistune and whether the absorber’s stiffness needs to increase or decrease to minimise the magnitude of the transmitted power. Numerical simulations are presented. These show the effectiveness of the control system, employing the error function and an adaptive absorber, in varying the stiffness of the absorber towards the optimum value.
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Published date: 2005
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Local EPrints ID: 465566
URI: http://eprints.soton.ac.uk/id/eprint/465566
PURE UUID: 2129e387-46e0-4884-933e-2ce6e6e2a4f9
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Date deposited: 05 Jul 2022 01:49
Last modified: 16 Mar 2024 20:15
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Author:
Hassan M El-Khatib
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