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CONTENTS
Volume 1, Number 1, January 2005
 

Abstract
This paper describes the area of intelligent systems research as funded by the Civil and Mechanical Systems (CMS) Division of the National Science Foundation (NSF). With developments in computer science, information technology, sensing and control the design of typical machines and structures by civil and mechanical engineers is evolving toward intelligent systems that can sense, decide and act. This trend toward electromechanical design is well-established in modern machines (e.g. vehicles, robots, disk drives) and often referred to as mechatronics. More recently intelligent systems design is becoming an important aspect of structures, such as buildings and bridges. We briefly review recent developments in structural control, including the role that NSF has played in their development, and discuss on-going CMS activities in this area. In particular, we highlight the interdisciplinary initiative on Sensors and Sensor Networks and the Network for Earthquake Engineering Simulation (NEES). NEES is a distributed cyberinfrastructure to support earthquake engineering research, and provides the pioneering NEES grid computing environment for simulation, teleoperation, data collection and archiving, etc.

Key Words
Division of Civil and Mechanical Systems, National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230, U.S.A.

Address
intelligent systems; mechatronics; automation; sensors.

Abstract
Simultaneous precision positioning and vibration suppression of a reciprocating flexible manipulator is investigated in this paper. The flexible manipulator is driven by a multifunctional active strut with fuzzy logic controllers. The multifunctional active strut is a combination of a motor assembly and a piezoelectric stack actuator to simultaneously provide precision positioning and wide frequency bandwidth vibration suppression capabilities. First, the multifunctional active strut and the flexible manipulator are introduced, and their dynamic models are derived. A control strategy is then proposed, which includes a position controller and a vibration controller to achieve simultaneous precision positioning and vibration suppression of the flexible manipulator. Next, fuzzy logic control approach is presented to design a fuzzy logic position controller and a fuzzy logic vibration controller. Finally, experiments are conducted for the fuzzy logic controllers and the experimental results are compared with those from a PID control scheme consisting of a PID position controller and a PID vibration control. The comparison indicates that the fuzzy logic controller can easily handle the non-linearity in the strut and provide higher position accuracy and better vibration reduction with less control power consumption.

Key Words
flexible manipulator; motion control; vibration suppression; fuzzy logic control; smart structure

Address
Intelligent and Composite Materials Laboratory, Department of Mechanical Engineering,
University of Hawaii at Manoa, Honolulu, HI 96822, USA

Abstract
In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.

Key Words
damage location; wavelet packet decomposition; model-free method.

Address
Department of Civil Engineering, Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong

Abstract
A ring-shaped lead zirconate titanate (PZT) piezoceramic sensor has been integrated with the Langevin-type piezoceramic driver of an ultrasonic wire-bonding transducer to form a smart transducer for in-situ measurement of three essential bonding parameters: namely, impact force, ultrasonic amplitude and bond time. This sensor has an inner diameter, an outer diameter and a thickness of 12.7 mm, 5.1 mm and 0.6 mm, respectively. It has a specifically designed electrode pattern on the two major surfaces perpendicular to its thickness along which polarization is induced. The process-test results have indicated that the sensor not only is sensitive to excessive impact forces exerted on the devices to be bonded but also can track changes in the ultrasonic amplitude proficiently during bonding. Good correlation between the sensor outputs and the bond quality has been established. This smart transducer has good potential to be used in automatic process-control systems for ultrasonic wire bonding.

Key Words
lead zirconate titanate (PZT); piezoceramic; ring sensor; smart transducer; ultrasonic wire bonder; ultrasonic wire bonding; automatic process control.

Address
Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University,
Hung Hom, Kowloon, Hong Kong

Abstract
This paper introduces a technology for robust and low maintenance cost sensor network capable to detect accelerations below a micro-g in a wide frequency bandwidth (above 1,000 Hz). Sensor networks with such performance are critical for navigation, seismology, acoustic sensing, and for the health monitoring of civil structures. The approach is based on the fabrication of an array of high sensitivity accelerometers, each utilizing Fabry-Perot cavity with wavelength-dependent reflectivity to allow embedded optical detection and serialization. The unique feature of the approach is that no local power source is required for each individual sensor. Instead one global light source is used, providing an input optical signal which propagates through an optical fiber network from sensor-to-sensor. The information from each sensor is embedded onto the transmitted light as an intrinsic wavelength division multiplexed signal. This optical ?ainbow?of data is then assessed providing real-time sensing information from each sensor node in the network. This paper introduces the Fabry-Perot based accelerometer and examines its critical features, including the effects of imperfections and resolution estimates. It then presents serialization techniques for the creation of systems of arrayed sensors and examines the effects of serialization on sensor response. Finally, a fabrication process is proposed to create test structures for the critical components of the device, which are dynamically characterized.

Key Words
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Address
Department of Mechanical and Aerospace Engineering, 4208 Engineering Gateway Building
University of California, Irvine, Irvine, CA 92697-3975, U.S.A

Abstract
This paper summarizes the application of a rational methodology for the structural assessment of older reinforced concrete Tunisian bridges. This methodology is based on ambient vibration measurement of the bridge, identification of the structures modal signature and finite element model updating. The selected case study is the Boujnah bridge of the Tunis-Msaken Highway. This bridge is made of a continuous four-span simply supported reinforced concrete slab without girders resting on elastomeric bearings at each support. Ambient vibration tests were conducted on the bridge using a data acquisition system with nine force-balance accelerometers placed at selected locations of the bridge. The Enhanced Frequency Domain Decomposition technique was applied to extract the dynamic characteristics of the bridge. The finite element model was updated in order to obtain a reasonable correlation between experime ntal and numerical modal properties. For the model updating part of the study, the parameters selected for the updating process include the concrete modulus of elasticity, the elastic bearing stiffness and the foundation spring stiffnesses. The primary objective of the paper is to demonstrate the use of the Enhanced Frequency Domain Decomposition technique combined with model updating to provide data that could be used to assess the structural condition of the selected bridge. The application of the proposed methodology led to a relatively faithful linear elastic model of the bridge in its present condition.

Key Words
ambient vibration testing; output-only modal identification; enhanced frequency domain identification technique; finite element model updating.

Address
1)Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School,
B.P. 743, La Marsa 2078, Tunisia
2)Department of Civil Engineering, University of British Columbia, Vancouver, British Columbia, Canada
3)Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School,

Abstract
Recent technological advancements in materials science, micro fabrication of MEMS (microelectromechanical systems), and bioengineered systems have made the dream of inexpensive, powerful, ubiquitous sensing a readily achievable reality. Examples range from truly smart airframes and self-evaluating buildings and infrastructure for natural hazard mitigation to large-scale weather forecasting and selforganizing energy systems. A common thread running through these, and all other applications of ubiquitous sensing, is the vast amounts of data generated, and a need to have the ubiquitous sensor networks process this data in order to return decisions and information. Sensor networks become a dynamic organism far more powerful and user-friendly than the traditional view of a sensor as a widget, an individual component that needs to be deployed, programmed, and interrogated. Therefore, the convergence of sensor technologies, communications, and computing has the potential to overcome barriers of time, scale, materials and environment. The National Workshop on Future Sensing Systems was held in Lake Tahoe, California, August 26-28, 2002, sponsored by the Sensors Technology Program of the NSF Division of Civil and Mechanical Systems (CMS), with co-sponsorship from DARPA, NIH, DOE, NIST, NASA, AFOSR, ONR, ARO, ARL, and NRL. The scope of this workshop encompassed discussions of research needs, current and emerging technologies, and efficacious partnerships required to develop and implement future sensing systems. The workshop was planned to stimulate synergistic ideas and directions generated by industrial, scientific and government participants, and to start planning a long-term road map for R&D projects related to emerging needs and technologies. Furthermore, this workshop started strategic partnerships among industry, scientific community, and government agencies that are developing innovative and cross-pollinating sensor systems capable of converting raw data into useful information about myriad environments. The workshop was designed to push the community to share and work together, not study the current state of the art. This gathering was not a place for the participants to give formal presentations about their research successes. The participants drove this workshop. The ideas, the concepts, and the research directions outlined in this paper were decided by all the participants. The workshop spawned numerous collaborations, proposals, and plans for future sensor research. It also proved that there are far more commonalities than differences in the challenges faced by a wide variety of researchers from the sensor community at large. Perhaps most importantly though, the workshop helped foster the strategic and targeted growth of that nascent community. The manuscript will first discuss the Workshop and its goals and organization, followed by an exposition of the research needs and directions of future growth in sensor-directed research. The final section discusses some proposed changes to how the research community might better organize to maximize the research output per dollar invested, and deliver more useful results. A list of defined abbreviations used in this paper is given by Appendix 1. Please note that the full word-for-word transcripts of the Workshop, as well as all the presentations, is freely available on-line at Http://www.ce.berkeley.edu/Programs/Geoengineering/sensors/.

Key Words
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Address
1)Center for Information Technology Research in the Interest of Society, University of California, Berkeley, U.S.A
2)School of Engineering and Computer Science, University of Denver, Denver, CO, U.S.A
3)Science Writer, San Francisco, CA, U.S.A


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