Cyber-Physical Codesign of Wireless Structural Control System

Structural control systems play a critical role in protecting civil infrastructure from natural hazards such as earthquakes and extreme winds. Utilizing wireless sensors for sensing, communication and control, wireless structural control systems provide an attractive alternative for structural vibration mitigation. Although wireless control systems have advantages of flexible installation, rapid deployment and low maintenance cost, there are unique challenges associated with them, such as wireless network induced time delay and potential data loss. These challenges need to be considered jointly from both the network (cyber) and control (physical) perspectives. This research aims to develop a framework facilitating cyber-physical codesign of wireless control system. The challenges of wireless structural control are addressed through: (1) a numerical simulation tool to realistically model the complexities of wireless structural control systems, (2) a codesign approach for designing wireless control system, (3) a sensor platform to experimentally evaluate wireless control performance, (4) an estimation method to compensate for the data loss and sensor failure, and (5) a framework for fault tolerance study of wireless control system withreal-time hybrid simulation. The results of this work not only provide codesign tools to evaluate and validate wireless control design, but also the codesign strategies to implement on real-world structures for wireless structural control

Enhancing the collaboration of earthquake engineering research infrastructures

Towards stronger international collaboration of earthquake engineering research infrastructures International collaboration and mobility of researchers is a means for maximising the efficiency of use of research infrastructures. The European infrastructures are committed to widen joint research and access to their facilities. This is relevant to European framework for research and innovation, the single market and the competitiveness of the construction industry.JRC.G.4-European laboratory for structural assessmen

Performance of the CGS six DOF Shaking Table on the Harmonic Signal Reproduction

Shaking table testing continues to play an important role in earthquake engineering research. It has been recognized as a powerful testing method to evaluate structural components and systems under realistic dynamic loads. Although it represents a very attractive experimental procedure, many technical challenges, which require attention and consideration, still remain. High fidelity in signal reproduction is the focus of the work presented in this paper. The main objective of this paper is to investigate the capabilities of adaptive control techniques based on Amplitude Phase Control (APC) and Adaptive Harmonic Cancellation (AHC) on the harmonic signal tracking performance of the shaking table. A series of 232 sinusoidal command waveforms with various frequencies and amplitudes were conducted on the shaking table of the laboratory of the National Earthquake Engineering Applied Research Center (CGS, Algeria). Experimental results are reported and recommendations on the use of these adaptive control techniques are discussed

Response of high-strength steel reinforced concrete structures to simulated earthquakes

In reinforced concrete (RC) structures expected to resist earthquake demands, substituting smaller amounts of high-strength steel for conventional steel reinforcement can help reduce reinforcement congestion and placement costs while keeping strength unchanged. Provided cross-sectional dimensions remain unchanged, reducing the amount of longitudinal steel in a member will result in a member with similar initial stiffness but lower post-cracking stiffness. Nominal strength can be kept nearly the same if this reduction in the amount of steel is accompanied by a corresponding increase in the strength of the steel. The topic of this investigation is whether two frames with the same initial stiffness and nominal strength, but different post-cracking stiffnesses, reach comparable peak drift during a given ground motion. This is a question about drift demand, not drift capacity. The impact of changes in steel strength on drift capacity has been examined by others and is not the subject of this study. Four nominally identical reinforced concrete frames were tested on a unidirectional earthquake simulator. In two frames, conventional reinforcing steel was used in the columns at a reinforcement ratio of 1.8%. In the other two frames, high-strength reinforcing steel was used in the columns at a reinforcement ratio of 0.8%. Each frame was subjected to one of two series (or sequences) of five ground motions. The first four motions were of either increasing intensity (series 1) or decreasing intensity (series 2). The last motion was the strongest used in this study, and had a peak ground acceleration of 1 g, a peak ground velocity of 11 in./sec, and a peak ground displacement of 1.3 in. Comparisons of frames with different post-cracking stiffness, and comparisons of similar frames subjected to different ground motion sequences supported the hypothesis that the dominant factor driving peak drift is initial period calculated using gross cross-sectional properties. To examine further the idea that initial period drives peak drift in RC structures subjected to earthquake demands, a dataset was compiled using results from more than 160 dynamic tests of RC structures and the measured responses of 3 instrumented RC buildings. This dataset was used to evaluate an expression proposed by Sozen (2003) indicating that peak drift is directly proportional to the product of peak ground velocity and initial period (calculated from gross cross-sectional properties). Comparisons of measured-to-estimated peak drift revealed that, for ground motions with PGV/PGA \u3e 0.03 sec, the studied expression produced reasonable and safe estimates of peak drift. Ground motions outside this range have been used in laboratory tests but are unlikely to occur frequently in the field. All the evidence examined suggest that peak drift caused by earthquake demands is proportional to initial period. It follows that replacing conventional steel reinforcing bars with fewer or smaller bars of higher strength is unlikely to result in consistent increases in drift demand, provided the cross-sectional dimensions remain unchanged

The influence of model and measurement uncertainties on damage detection of experimental structures through recursive algorithms

In this work, we developed a framework for identifying frame-type structures regarding the measurement uncertainty and the uncertainty involved in inherent and structural parameters. The identification process is illustrated and examined on a one-eight-scale four-story moment-resisting steel frame under seismic excitation using two well-known recursive schemes: the Extended Kalman filter (EKF) and Unscented Kalman Filter (UKF) methods. The nonlinear system equations were assessed by applying a first-order instantaneous linearization approach through the EKF method. In contrast, the UKF algorithm employs several sample points to estimate moments of random variables’ nonlinear transformations. A nonlinear transformation is applied to distribute sample points to derive the precise mean and covariance up to the second order of any nonlinearity. Accordingly, it is theoretically expected that the UKF algorithm is more capable of identifying the nonlinear systems and determining the unknown parameters than the EKF algorithm. The capability of the EKF and UKF algorithms was assessed by considering a 4-story moment-resisting steel frame with several inherent uncertainties, including the material behavior model, boundary conditions, and constraints. In addition to these uncertainties, the combination of acceleration and displacement responses of different structural levels is employed to evaluate the capability of the algorithms. The information entropy measure is used to investigate further the uncertainty of a group of established model parameters. As highlighted, a good agreement is observed between the results using the information entropy measure criterion and those using the UKF and EKF algorithms. The results illustrate that using the responses of fewer levels placed in the proper positions may lead to improved outcomes than those of more improperly positioned levels

Multi-UAV Integrated Internet of Things System for Generating Safe Map in Post-Disaster

芝浦工業大学2019年

Semi-active structural control systems with nonlinear actuator dynamics: Design, stability analysis, and experimental verification.

The dissertation presents the development and experimental validation of control laws that provide stable closed-loop behavior and good performance for semi-active control systems with nonlinear actuator dynamics. In particular, the work treats variable orifice hydraulic semi-active actuators installed on a structure subjected to seismic motions. A new dynamic model is developed for the variable-orifice hydraulic semi-active actuator that treats laminar, turbulent and transition flow. A quickest descent Lyapunov method is used to develop the semi-active control law. The resulting controller provides stability for semi-active systems with actuator dynamics that satisfy two general conditions. These conditions cover a wide variety of semi-active devices. This solution to the stability problem and is one of the major results of this dissertation.The response characteristics of the quickest descent Lyapunov controller are also demonstrated experimentally. A test structure outfitted with a variable orifice semi-active actuator is excited using a uniaxial electro-hydraulic seismic motion simulator. The experimental work demonstrates that the quickest descent control design technique is a valuable tool for designing stable semi-active control laws that exhibit good performance against realistic seismic inputs.After treating the stability problem, the performance of the quickest descent controller is investigated for bounded disturbance inputs. A theorem is provided to establish a ball of ultimate boundedness (stable attractor) based on the upper bound of the disturbances. Simulation results using a variety of disturbance inputs are provided to demonstrate the effectiveness of the quickest descent control law. The results indicate that the guaranteed performance (i.e., bound of the stable attractor) is too conservative by two orders of magnitude for the best performing controller. This opens up a new problem for future researchers on how to construct less conservative performance bounds.Semi-active control is a promising technology for reducing undesirable vibrations in structures. To determine closed loop stability and performance for such systems, past efforts have utilized linear control synthesis and analysis techniques, neglecting any nonlinear actuator dynamics. An open problem in the literature is establishing the stability of semi-active control systems with nonlinear actuator dynamics. The main focus of this dissertation is on that open stability problem

Dynamic Excitation for Geotechnical Centrifuge Modelling

The method of physical modeling in the centrifuge is growing in acceptance in the U.S.A. following many years of use in U.S.S.R., Denmark, England, Norway, France and Japan. Simulation of dynamic events (machine vibration, wave forces, and earthquake) in modeling in the centrifuge has important applications, especially on the large national Geotechical Centrifuge being constructed at NASA-ARC. The most difficult problem is that of earthquake simulation. Several schemes for light weight shakers have been proposed in a Workshop on Dynamic Excitation for Geotechnical Centrifuge Model Testing held in August, 1979. More recently, a scheme has been presented which utilizes traveling waves generated through a diaphragm at the side of the container which has many promising advantages and does not negate the work done in shaker development, but improves their utilization

Potential utilization of the NASA/George C. Marshall Space Flight Center in earthquake engineering research

Earthquake engineering research capabilities of the National Aeronautics and Space Administration (NASA) facilities at George C. Marshall Space Flight Center (MSFC), Alabama, were evaluated. The results indicate that the NASA/MSFC facilities and supporting capabilities offer unique opportunities for conducting earthquake engineering research. Specific features that are particularly attractive for large scale static and dynamic testing of natural and man-made structures include the following: large physical dimensions of buildings and test bays; high loading capacity; wide range and large number of test equipment and instrumentation devices; multichannel data acquisition and processing systems; technical expertise for conducting large-scale static and dynamic testing; sophisticated techniques for systems dynamics analysis, simulation, and control; and capability for managing large-size and technologically complex programs. Potential uses of the facilities for near and long term test programs to supplement current earthquake research activities are suggested