This paper studies the semi-active control of a novel configuration of tuned mass damper (TMD) using a modified clipped optimal control strategy, with the intention to harvest the vibration energy and control the vibration at the same time. One of the authors recently proposed and optimized the so called series TMD, in which multiple auxiliary masses and absorbers are connected to the primary system in series. It has been proven that it is more effective and robust than other types of TMDs with the same mass ratio such as parallel multiple TMDs, multi-degree-of-freedom (DOF) TMDs and three- or four-element TMDs. In this paper, by replacing the viscous damping element between the two auxiliary masses of series TMD system with an electromagnetic transducer, we implement the semi-active series TMD by controlling the current flow through the transducer in a semi-active way, which also means that the electromagnetic motor works in the driven mode and acts as a electricity generator. The proposed control strategy is a combination of LQG and clipped control. LQG control with acceleration feedback is first designed and then a modified clipped control is used to realize it in a semi-active manner with a practical maximum force or damping limitations. Numerical simulations are carried out based on a tall building with semi-active series TMD under random and harmonic excitations, in comparison with the active and passive strategies. The results show that the proposed semi-active series TMD is very effective to control the vibration while harvesting large amount energy from the vibration of buildings.
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