| Excited by a harmonic disturbance, the primary structure will vibrate at the frequency of the driving force in the steady state. Traditionally, a passive absorber will be resorted to largely suppress this vibration in the event of the constant exciting frequency and the low damping in the system; however, when the driving frequency is shifting and/or there exists a high damping, it becomes impossible to bring the steady-state vibrations to rest or even to a desired small value only using a passive vibration absorber; instead, the semi-active or active vibration absorbers have been studied for decades, aiming to achieve better results in vibration suppression.; The first part of the thesis presents a newly-designed semi-active electromagnetic vibration absorber (EMVA), whose stiffness is on-line tunable. This facilitates the vibration suppression of the primary system excited by a harmonic force with a variable frequency.; The second part of the thesis provides a new perspective on the design of a time-delayed active vibration absorber. This control system features one output feedback. The close relationship between the time-delayed active vibration absorber and the traditional PD controller is revisited with an assistance of a vector interpretation. (Abstract shortened by UMI.)... |
