Experiments and analysis for a controlled mechanical absorber considering delay effect

It is well known that a traditional passive absorber is highly effective within a narrow frequency band. To solve this problem, a time-delayed absorber is utilized to suppress the vibration of the primary system when the passive absorber loses efficiency. A controllable mechanical device is designed and constructed to implement the time-delayed feedback control. The time delay mainly comes from signal acquiring and processing, computing and applying the control force. Such delay is inherent and non-ignorable. To begin with, a mathematical model with the inherent delay is proposed to provide an analytical fundamental. Then, the value of the inherent time delay is identified by the hammer test. Experimental and numerical results show that reasonable feedback gains can significantly improve the absorber׳s effectiveness when the excitation frequency is close to the second resonant frequency of the new coupled system. This research provides instructive ideas to the application of the time-delayed absorber in practical engineering.