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CONTENTS
Volume 11, Number 6, June 2013
 

Abstract
This paper evaluates the closed loop performance of the reaching law based discrete sliding mode controller with multisensor data fusion (MSDF) in real time, by controlling the first two vibrating modes of a piezo actuated structure. The vibration is measured using two homogeneous piezo sensors. The states estimated from sensors output are fused. Four fusion algorithms are considered, whose output is used to control the structural vibration. The controller is designed using a model identified through linear Recursive Least Square (RLS) method, based on ARX model. Improved vibration suppression is achieved with fused data as compared to single sensor. The experimental evaluation of the closed loop performance of sliding mode controller with data fusion applied to piezo actuated structure is the contribution in this work.

Key Words
data fusion; sliding mode controller; piezoelectric; smart structure; estimation; structural vibration

Address
J. Arunshankar : Department of Instrumentation and Control Systems Engineering, PSG College of Technology,
Coimbatore, India
M. Umapathy : Department of Instrumentation and Control Engineering, National Institute of Technology,
Tiruchirappalli, India
B. Bandhopadhyay : Systems and Control Engineering, Indian Institute of Technology Bombay, Mumbai, India

Abstract
Identification of damage has become an evolving area of research over the last few decades with increasing the need of online health monitoring of the large structures. The visual damage detection can be impractical, expensive and ineffective in case of large structures, e.g., offshore platforms, offshore pipelines, multi-storied buildings and bridges. Damage in a system causes a change in the dynamic properties of the system. The structural damage is typically a local phenomenon, which tends to be captured by higher frequency signals. Most of vibration-based damage detection methods require modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties such as natural frequencies and mode shapes are not such good sensitive indication of structural damage. Identification of damaged jacket type offshore platform members, based on wavelet packet transform is presented in this paper. The jacket platform is excited by simple wave load. Response of actual jacket needs to be measured. Dynamic signals are measured by finite element analysis result. It is assumed that this is actual response of the platform measured in the field. The dynamic signals first decomposed into wavelet packet components. Then eliminating some of the component signals (eliminate approximation component of wavelet packet decomposition), component energies of remained signal (detail components) are calculated and used for damage assessment. This method is called Detail Signal Energy Rate Index (DSERI). The results show that reduced wavelet packet component energies are good candidate indices which are sensitive to structural damage. These component energies can be used for damage assessment including identifying damage occurrence and are applicable for finding damages\' location.

Key Words
damage detection; jacket platform; wavelet transform; wavelet packet transform

Address
Sajad Shahverdi and Mohammad Ali Lotfollahi-Yaghin : Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Behrouz Asgarian: Civil Engineering Department, K.N. Toosi University of Technology, Tehran, Iran

Abstract
The paper deals with the design of a device for sound reproduction to be fixed to a supporting surface. The device is made up of two different types of acoustic actuators based on different technologies. This allows to reproduce sound in the range of frequencies from 20 Hz to 20 kHz. The generation of sound at high frequencies is demanded to a magnetostrictive actuator, while a more traditional magnetodynamics actuator is used to generate sound at low frequencies. The coupling between these two actuators leads to a device having small overall dimensions and high performance.

Key Words
acoustic actuator; magnetostrictive actuator; magnetodynamics actuator; sound reproduction; loudspeaker

Address
Francesco Braghin, Francesco Castelli-Dezza, Simone Cinquemani and Ferruccio Resta : Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, Milan, 20156, Italy

Abstract
This paper investigates application of a control algorithm called model predictive sliding mode control (MPSMC) to active vibration suppression of a cantilevered aluminum beam. MPSMC is a relatively new control algorithm where model predictive control is employed to enhance sliding mode control by enforcing the system to reach the sliding surface in an optimal manner. In previous studies, it was shown that MPSMC can be applied to reduce hysteretic effects of piezoelectric actuators in dynamic displacement tracking applications. In the current study, a cantilevered beam with unknown mass distribution is selected as an experimental test bed in order to verify the robustness of MPSMC in active vibration control applications. Experimental results show that MPSMC can reduce vibration of an aluminum cantilevered beam at least by 29% regardless of modified mass distribution.

Key Words
active vibration control; piezoceramic actuator; 1D piezoelectric bimorph structure; model predictive sliding mode control

Address
Byeongil Kim : Powertrain CAE Team, Research & Development Division, Hyundai-Kia Motors 772-1, Jangduk-Dong, Hwaseong-Si, Gyeonggi-Do, Republic of Korea
Gregory N. Washington : The Henry Samueli School of Engineering, University of California, Irvine 5200 Engineering Hall, Irvine CA 92697, USA
Hwan-Sik Yoon: 3Department of Mechanical Engineering, The University of Alabama, Box 870276, Tuscaloosa, AL 35487, USA

Abstract
The Jiangyin Bridge is a suspension bridge with a main span of 1385 m over the Yangtze River in Jiangsu Province, China. Being the first bridge with a main span exceeding 1 km in Chinese mainland, it had been instrumented with a structural health monitoring (SHM) system when completed in 1999. After operation for several years, it was found with malfunction in sensors and data acquisition units, and insufficient sensors to provide necessary information for structural health evaluation. This study reports the SHM system upgrade project on the Jiangyin Bridge. Although implementations of SHM system have been reported worldwide, few studies are available on the upgrade of SHM system so far. Recognizing this, the upgrade of original SHM system for the bridge is first discussed in detail. Especially, lessons learned from the original SHM system are applied to the design of upgraded SHM system right away. Then, performance assessment of the bridge, including: (i) characterization of temperature profiles and effects; (ii) recognition of wind characteristics and effects; and (iii) identification of modal properties, is carried out by making use of the long-term monitoring data obtained from the upgraded SHM system. Emphasis is placed on the verification of design assumptions and prediction of bridge behavior or extreme responses. The results may provide the baseline for structural health evaluation.

Key Words
structural health monitoring; performance assessment; environmental effect; system upgrade; long-span bridge

Address
H.F. Zhou : College of Architecture and Civil Engineering, Wenzhou University, Wenzhou, China
Y.Q. Ni and J.M. Ko : Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong


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