Smart structures: Part I—Active and semi-active control

In this paper we review essential aspects in- volved in the design of an active vibration control system. We present a generic procedure to the design process and give selective examples from the literature on relevant ma- terial. Together with examples of their applications, various topics are briefly introduced, such as structure modeling, model reduction, feedback control, feedforward control, con- trollability and observability, spillover, eigenstructure assign- ment (pole placement), coordinate coupling control, robust control, optimal control, state observers (estimators), intelli- gent structure and controller, adaptive control, active con- trol effects on the system, time delay, actuator-structure interaction, and optimal placement of actuators.

Active Structural Vibration Control: A Review

Summary
A newly developed, completely contactless structural health monitoring system framework based on the use of regular cameras and computer vision techniques is introduced for obtaining displacements and vibrations of structures, which are critical responses for performance-based design and evaluation of structures. To provide contactless and practical monitoring, the current vision-based displacement measurement methods are improved by eliminating the physical target attachment. This is achieved by means of utilizing imaging key-points as virtual targets. As a result, pixel-based displacements of a monitored structural location are determined by using an improved detection and match key-points algorithm, in which false matches are identified and discarded almost completely. To transform pixel-based displacements to engineering units, a practical camera calibration method is developed because calibration standard on a physical target no longer exists. Moreover, a framework for evaluating the accuracy of vision-based displacement measurements is established for the first time, which, in return, provides users with the most crucial information of a measurement. The proposed framework along with a conventional sensor network and a data acquisition system are applied and verified on a real-life stadium during football games for structural assessment. The results obtained by the new method are successfully validated with the data acquired from sensors such as linear variable differential transformers and accelerometers. Because the proposed method does not require any type of sensor and target attachment, common field works such as sensor installation, wiring, maintaining conventional data acquisition systems are not required. This advantage enables an inexpensive and practical way for structural assessment, especially for real-life structures. Copyright © 2016 John Wiley & Sons, Ltd.

Completely contactless structural health monitoring of real‐life structures using cameras and computer vision

Vibration serviceability of stadia structures subjected to dynamic crowd loads: A literature review

Semi-active vibration absorber based on real-time controlled MR damper

Large floor vibration amplitudes can produce disruption and reduced efficiency in employees, and in more extreme cases can result in complete abandonment of a structure for its intended use. The implementation of active control to reduce vibration levels in lightweight floor systems is explored in this paper. A velocity feedback scheme has been developed in which an electromagnetic proof-mass actuator is used to impart control forces on a floor system, thus, reducing the amplitudes of the floor motion. The development, analysis, and experimental verification are discussed for the successful implementation of this control application. A full-scale experimental test floor was designed, constructed, and modeled analytically for this study. Both analytical and experimental results for the floor response to transient excitation show an increase in damping from approximately 2.5% to 40%. Experimental results for walking excitation show a reduction of peak velocity amplitudes to 12% of amplitudes recorded for th...

Active control approach for reducing floor vibrations

The research presented in this paper resolves several measurement issues pertaining to the experimental modal analysis of lightweight steel floor systems. This investigation represents a first step toward collecting more extensive data on the dynamic behavior of steel floor systems. These data can then be used to improve design and analysis procedures for assessing the vibration serviceability of a floor system before construction. Some of the issues investigated herein are the selection considerations for the data acquisition system and transducers, the appropriate type and placement of excitation, and fast Fourier transform processing considerations.

Dynamic Measurements of In-Place Steel Floors to Assess Vibration Performance

This paper reviews research, conducted by the authors over the last decade, pertaining to the control of ex- cessive floor vibration using active and passive devices. The active device studied uses a proof-mass actuator to deliver the control force to the floor system. Effectiveness and stabil- ity characteristics for a single-input/single-output (SISO) con- trol scheme, using velocity feedback, are explored. The SISO system is shown to increase damping to 40% of critical on an experimental floor when amplitudes remain in the linear range. When implemented on two in-place floors, at least a 70% reduction in vibration amplitudes due to walking was ob- served. Next, the benefits of expanding to a practical single- input/multi-output (SIMO) control system are identified. Ad- ditionally, techniques to optimize the SIMO scheme are presented. Because of the stability characteristics of the controlled system, the improvement noted for the SIMO scheme is most dramatic for floors with fundamental frequen- cies near the natural frequency of the actuator. I na2H zfloor example, a SIMO control scheme provided seven times more reduction than that of the SISO system. The passive device research focuses on the experimental implementation of tuned mass dampers (TMDs) to control floor vibration. Two different configurations are explored. The uniqueness of the first device is that liquid filled bladders are used to provide an economical damping mechanism. When implemented on an office floor, a significant improvement of walking vibration lev- els was observed. Satisfaction with the repair was noted from the occupants. The second device utilizes a configuration that has great flexibility in the field, thus allowing for more eco- nomical mass production. Using two TMDs, a significant re- duction of response was noted for the 5 and 6 Hz modes. Research to improve these active and passive strategies continues and will be reported as significant results are achieved.

Controlling Floor Vibration with Active and Passive Devices

Excessive floor vibration due to walking is an important serviceability condition to be considered in building design. This paper presents several case studies of problem floors. The case studies include complaints about office, classroom, and retail spaces where vibration levels were found disturbing. In each of these cases, the cause of the vibration was due to people walking around the space. These case studies are presented to reinforce the existence of this problem, to describe nonstructural factors that affect the behavior of floors, and to provide new data to the design and research communities.

Linda M. Hanagan

Papers

Active control approach for reducing floor vibrations

Dynamic Measurements of In-Place Steel Floors to Assess Vibration Performance

Controlling Floor Vibration with Active and Passive Devices

Walking-Induced Floor Vibration Case Studies

Experimental Implementation of Active Control to Reduce Annoying Floor Vibrations