Adaptive length SMA pendulum smart tuned mass damper performance in the presence of real time primary system stiffness change

Michael T. Contreras , Dharma Theja Reddy Pasala , Satish Nagarajaiah

Abstract

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

Key Words

smart tuned mass damper; adaptive passive tuned mass damper; tuned vibration absorbers; shape memory alloy; adaptive length pendulum; observer based structural health monitoring

Address

Michael T. Contreras — Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Dharma Theja Reddy Pasala — Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA
Satish Nagarajaiah — Department of Civil and Environmental Engineering and Mechanical Engineering and Material science, Rice University, Houston, TX 77005, USA

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