An adaptive-passive retuning device for a pendulum tuned mass damper considering mass uncertainty and optimum frequency

A tuned mass damper (TMD) is one of the most used structural control devices. However, a traditional TMD has the disadvantage of high sensitivity to frequency deviation and difficulty adjusting the frequency. The optimal frequency for a TMD is dependent on the structural dominant frequency and the TMD mass ratio. Nevertheless, the actual structural modal mass is difficult to obtain, and the presence of a TMD may interfere with identification of the natural structural frequency. Aiming to control wind-induced vibration, an adaptive-passive retuning device is developed for a pendulum TMD called an adaptive-passive variable pendulum TMD (APVP-TMD). When it is time to adjust the pendulum, the mass will first be locked, and the structural frequency in this case is identified through wavelet transformation by an acceleration sensor and a microcontroller. It is found that this is actually the optimal frequency for the TMD. Then, a stepper motor will adjust the length of the pendulum under the guidance of the microcontroller. The effectiveness of APVP-TMD is verified through both discrete and continuous models. For the discrete model, a single-degree-of-freedom primary structure coupled with an APVP-TMD is presented as an experiment with analysis comparison, and a five-degree-of-freedom primary structure coupled with an APVP-TMD is proposed as a numerical simulation. For the continuous model, a wind-sensitive concrete chimney is controlled by an APVP-TMD as a case study. The results all show that the APVP-TMD can identify the optimal frequency and retune itself effectively, and the retuned TMD has better vibration control than the mistuned one.