Shirley J. Dyke

Modeling and Control of Magnetorheological Dampers for Seismic Response Reduction

Control of civil engineering structures for earthquake hazard mitigation represents a relatively new area of research that is growing rapidly. Control systems for these structures have unique requirements and constraints. For example, during a severe seismic event, the external power to a structure may be severed, rendering control schemes relying on large external power supplies ineffective. Magnetorheological (MR) dampers are a new class of devices that mesh well with the requirements and constraints of seismic applications, including having very low power requirements. This paper proposes a clipped-optimal control strategy based on acceleration feedback for controlling MR dampers to reduce structural responses due to seismic loads. A numerical example, employing a newly developed model that accurately portrays the salient characteristics of the MR dampers, is presented to illustrate the effectiveness of the approach.

An experimental study of MR dampers for seismic protection

In this paper, the efficacy of magnetorheological (MR) dampers for seismic response reduction is examined. To investigate the performance of the MR damper, a series of experiments was conducted in which the MR damper is used in conjunction with a recently developed clipped-optimal control strategy to control a three-story test structure subjected to a one-dimensional ground excitation. The ability of the MR damper to reduce both peak responses, in a series of earthquake tests, and rms responses, in a series of broadband excitation tests, is shown. Additionally, because semi-active control systems are nonlinear, a variety of disturbance amplitudes are considered to investigate the performance of this control system over a variety of loading conditions. For each case, the results for three clipped-optimal control designs are presented and compared to the performance of two passive systems. The results indicate that the MR damper is quite effective for structural response reduction over a wide class of seismic excitations.

Seismic Response Reduction Using Magnetorheological Dampers

Abstract Control of civil engineering structures for earthquake hazard mitigation represents a relatively new area of research that is growing rapidly. Control systems for these structures have unique requirements and constraints. For example, during a severe seismic event, the external power to a structure may be severed, rendering control schemes relying on large external power supplies ineffective. Magnetorheological (MR) dampers are a new class of devices that mesh well with the requirements and constraints of seismic applications, including having very low power requirements. This paper proposes a clipped-optimal control strategy for controlling MR dampers to reduce structural responses due to seismic loads. A numerical example, employing a newly developed model that accurately portrays the salient characteristics of the MR dampers, is presented to illustrate the effectiveness of the approach.

Cyber-Physical Codesign of Distributed Structural Health Monitoring with Wireless Sensor Networks

Our deteriorating civil infrastructure faces the critical challenge of long-term structural health monitoring for damage detection and localization. In contrast to existing research that often separates the designs of wireless sensor networks and structural engineering algorithms, this paper proposes a cyber-physical codesign approach to structural health monitoring based on wireless sensor networks. Our approach closely integrates 1) flexibility-based damage localization methods that allow a tradeoff between the number of sensors and the resolution of damage localization, and 2) an energy-efficient, multilevel computing architecture specifically designed to leverage the multiresolution feature of the flexibility-based approach. The proposed approach has been implemented on the Intel Imote2 platform. Experiments on a simulated truss structure and a real full-scale truss structure demonstrate the systems efficacy in damage localization and energy efficiency.

Benchmark problems in structural control: Part I - Active Mass Driver system

This paper presents the overview and problem definition for a benchmark structural control problem. The structure considered—chosen because of the widespread interest in this class of systems—is a scale model of a three-storey building employing an active mass driver. A model for this structural system, including the actuator and sensors, has been developed directly from experimentally obtained data and will form the basis for the benchmark study. Control constraints and evaluation criteria are presented for the design problem. A simulation program has been developed and made available to facilitate comparison of the efficiency and merit of various control strategies. A sample control design is given to illustrate some of the design challenges.

A holistic approach to decentralized structural damage localization using wireless sensor networks

Wireless sensor networks (WSNs) have become an increasingly compelling platform for structural health monitoring (SHM) applications, since they can be installed relatively inexpensively onto existing infrastructure. Existing approaches to SHM in WSNs typically address computing system issues or structural engineering techniques, but not both in conjunction. In this paper, we propose a holistic approach to SHM that integrates a decentralized computing architecture with the damage localization assurance criterion algorithm. In contrast to centralized approaches that require transporting large amounts of sensor data to a base station, our system pushes the execution of portions of the damage localization algorithm onto the sensor nodes, reducing communication costs by an order of magnitude in exchange for moderate additional processing on each sensor. We present a prototype implementation of this system built using the TinyOS operating system running on the Intel Imote2 sensor network platform. Experiments conducted using two different physical structures demonstrate our systems ability to accurately localize structural damage. We also demonstrate that our decentralized approach reduces latency by 64.8% and energy consumption by 69.5% compared to a typical centralized solution, achieving a projected lifetime of 191 days using three standard AAA batteries. Our work demonstrates the advantages of a holistic approach to cyber-physical systems that closely integrates the design of computing systems and physical engineering techniques.

Benchmark problems in structural control: part II—active tendon system

In a companion paper (Spencer et al.), an overview and problem definition was presented for a well-defined benchmark structural control problem for a model building configured with an Active Mass Driver (AMD). A second benchmark problem is posed here based on a high-fidelity analytical model of a three-storey, tendon-controlled structure at the National Center for Earthquake Engineering Research (NCEER). The purpose of formulating this problem is to provide another setting in which to evaluate the relative effectiveness and implementability of various structural control algorithms. To achieve a high level of realism, an evaluation model is presented in the problem definition which is derived directly from experimental data obtained for the structure. This model accurately represents the behaviour of the laboratory structure and fully incorporates actuator/sensor dynamics. As in the companion paper, the evaluation model will be considered as the real structural system. In general, controllers that are successfully implemented on the evaluation model can be expected to perform similarly in the laboratory setting. Several evaluation criteria are given, along with the associated control design constraints.

Vision‐Based Automated Crack Detection for Bridge Inspection

The visual inspection of bridges demands long inspection time and also makes it difficult to access all areas of the bridge. This paper presents a visual-based crack detection technique for the automatic inspection of bridges. The technique collects images from an aerial camera to identify the presence of damage to the structure. The images are captured without controlling angles or positioning of cameras so there is no need for calibration. This allows the extracting of images of damage sensitive areas from different angles to increase detection of damage and decrease false-positive errors. The images can detect cracks regardless of the size or the possibility of not being visible. The effectiveness of this technique can be used to successfully detect cracks near bolts.

A Holistic Approach to Decentralized Structural Damage Localization Using Wireless Sensor Networks

Wireless sensor networks (WSNs) have become an increasingly compelling platform for structural health monitoring (SHM) applications, since they can be installed relatively inexpensively onto existing infrastructure. Existing approaches to SHM in WSNs typically address computing system issues or structural engineering techniques, but not both in conjunction. In this paper, we propose a holistic approach to SHM that integrates a decentralized computing architecture with the damage localization assurance criterion algorithm. In contrast to centralized approaches that require transporting large amounts of sensor data to a base station, our system pushes the execution of portions of the damage localization algorithm onto the sensor nodes, reducing communication costs by an order of magnitude in exchange for moderate additional processing on each sensor. We present a prototype implementation of this system built using the TinyOS operating system running on the Intel Imote2 sensor network platform. Experiments conducted using two different physical structures demonstrate our systems ability to accurately localize structural damage. We also demonstrate that our decentralized approach reduces latency by 64.8% and energy consumption by 69.5% compared to a typical centralized solution, achieving a projected lifetime of 191 days using three standard AAA batteries. Our work demonstrates the advantages of a holistic approach to cyber-physical systems that closely integrates the design of computing systems and physical engineering techniques.

Modeling and identification of a shear mode magnetorheological damper

Magnetotheological (MR) dampers have emerged recently as potential devices for vibration mitigation and semi-active control in smart structures and vehicle applications. These devices are highly nonlinear and thus accurate models of these devices are important for effective simulation and control system design. In the current literature, the Bouc–Wen model is coupled with linear elements to describe these MR devices both in simulation and control. In this paper, we propose the friction Dahl model to characterize the dynamics of a shear mode MR damper. This leads to a reinterpretation of the MR damper behavior as a frictional device whose friction parameters change with the voltage. An identification technique for this new model is proposed and tested numerically using an experimentally obtained model. A good match has been observed between the model obtained from experiments and the Dahl based model of the MR device.