We have studied stimulated Brillouin scattering in single-mode optical fibers as a sensor for both temperature and strain. Shape Memory alloy Nitinol is also studied for enhancement of active sensing and control in st...
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We have studied stimulated Brillouin scattering in single-mode optical fibers as a sensor for both temperature and strain. Shape Memory alloy Nitinol is also studied for enhancement of active sensing and control in structures. We have introduced the hybrid sBs amplifier/oscillator scheme, in which the short fiber amplifier performs sensing and the long oscillator fiber provides the required signal. The sensing fiber can be coated with SMA thin film for ruggedness, increased sBs sensitivity to temperature and strain, and memory or trainability. The oscillator/amplifier scheme also serves as a building block in the design of optical threshold logic circuits, optical computation, and more sophisticated sensing schemes. Such sensing schemes can be highly competitive with those based on fiber Bragg grating. The incorporation of SMA thin films provides memory capability to all these applications.
Genetic algorithms will be used for the optimization of feedback gains and controller placement for discrete building structures. The optimal design and placement of controllers at discrete locations is an important p...
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Genetic algorithms will be used for the optimization of feedback gains and controller placement for discrete building structures. The optimal design and placement of controllers at discrete locations is an important problem that will have impact on the control of civil engineering structures. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Became of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a nonlinear constrained mixed integer problem that can be very difficult to solve. Using genetic algorithms in conjunction with gradient based optimization techniques will allow for the simultaneous placement and design of an effective structural control system. The introduction of genetic-based algorithms should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem.
The paper reviews recent achievements in the application of smart-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed wing aircraft. A brief review of the induced-strain actuat...
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The paper reviews recent achievements in the application of smart-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed wing aircraft. A brief review of the induced-strain actuation principles and capabilities is done first. Attention is then focused on the smart rotor blade applications. Induced twist, active blade tip, and active blade flap are presented, with emphasis on experimental results. The fixed wing aircraft applications are considered next. Experiments of active flutter control, buffet suppression, gust load alleviation, and sonic fatigue reduction are discussed. Conclusions and directions for further work are presented at the end of the paper.
In the present study, the vibration control of a hybrid smart composite beam actuated by both electro-rheological fluids (ERFs) and piezoceramic actuators is investigated. A carbon fiber reinforced plastics beam, incl...
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In the present study, the vibration control of a hybrid smart composite beam actuated by both electro-rheological fluids (ERFs) and piezoceramic actuators is investigated. A carbon fiber reinforced plastics beam, including interleaved ERF and bonded piezoceramics, is prepared and tested under sinusoidal external excitations. Four kinds of feedback control strategies for both ERF and piezoceramic actuators are adopted in order to suppress the deflection at the free end of the cantilevered composite beam. The optimum combination of these control strategies for two types of actuators is discussed when the two actuators operate simultaneously.
It is now well known that smart fluids (electrorheological (ER) and magnetorheological (MR)) can form the basis of controllable vibration damping devices. With both types of fluid, however, the force/velocity characte...
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It is now well known that smart fluids (electrorheological (ER) and magnetorheological (MR)) can form the basis of controllable vibration damping devices. With both types of fluid, however, the force/velocity characteristic of the resulting damper is significantly non-linear, possessing the general form associated with a Bingham plastic. In a previous paper the authors showed that by using a linear feedback control strategy it is possible to produce the equivalent of a viscous damper with a continuously variable damping coefficient. In the present paper the authors illustrate an extension of the technique, by showing how the shape of the force/velocity characteristic can be controlled through feedback control. This is achieved by using a polynomial function to generate a set point based upon the damper velocity. The response is investigated for polynomial functions of zero, 1st and 2nd order. It is shown how the damper can accurately track higher order polynomial shaping functions, whilst the zero order function is particularly useful in illustrating the dynamics of the closed-loop system.
smart structural systems require the electronic control systems which are integrated into the structures to be small, light weight and power-efficient. The field programmable gate array (FPGA) is a good platform to im...
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smart structural systems require the electronic control systems which are integrated into the structures to be small, light weight and power-efficient. The field programmable gate array (FPGA) is a good platform to implement such controllers. In our previous work, FPGA-based digital controllers were built and tested on a simple structural system. In order to implement multivariable controllers, the hardware resources for FPGA-based architecture need to be further reduced. Distributed arithmetic (DA) has long been proven to be a very efficient means to mechanize computations that are dominated by inner products involving constant multiplicand. The computational requirements of the smart structural controllers match this type very well. In this paper various DA structure controllers are designed and results are compared with multiply-and-accumulate structure controllers. Single- and multi-variable controllers are implemented and tested on a cantilevered beam.
This paper presents a strategy for active damping of cable structures, using active tendons. The first part of the paper summarizes the theoretical background: the control law is briefly presented together with the ma...
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This paper presents a strategy for active damping of cable structures, using active tendons. The first part of the paper summarizes the theoretical background: the control law is briefly presented together with the main results of an approximate linear theory which allows to predict the closed-loop poles with a root locus technique. The second part of the paper reports on experimental results obtained with two test structures: the first one is a small size mock-up representative of a cable-stayed bridge during the construction phase. The control of the parametric vibration of passive cables due to deck vibration is demonstrated. The second one is a 30 m long mock-up built on the reaction wall of the ELSA test facility at the JRC Ispra (Italy); this test structure is used to demonstrate the practical implementation of the control strategy with hydraulic actuators.
Recently, significant progress has been made in the synthesis of intelligent structures incorporating shape memory alloys (SR IA) [1, 2]. These structures are primarily employed to control the static and elastodynamic...
Recently, significant progress has been made in the synthesis of intelligent structures incorporating shape memory alloys (SR IA) [1, 2]. These structures are primarily employed to control the static and elastodynamic responses of distributed parameter systems including light space structures. It is well recognized that the SMA actuator produces relatively large control forces, but exhibits slow response time compared to other actuating: smartmaterials such as piezoceramics. Therefore, it is necessary to take into account the dynamic bandwidth of the SMA actuator in the system model in order to accurately evaluate vibration control performance of flexible structures. The goal of this work is to demonstrate the effectiveness of the dynamic bandwidth of the actuator on the vibration suppression capability in a dosed-loop control system. The present work presents a sliding mode control for vibration of a flexible structure with the dynamics of SMA actuator. This is an extension of the previous work [2] in which the actuator dynamic was not considered. The dynamic behavior of the employed SMA actuator is experimentally identified and incorporated with the governing equation of motion of a flexible structure. A sliding mode controller (SMC) for vibration suppression is then designed by treating frequency and damping deviations as uncertain parameters. The controller is experimentally realized and vibration control responses are presented in the time domain.
This paper presents control characteristics of a semi-active magneto-rheological (MR) fluid damper for a passenger vehicle. A cylindrical MR damper is devised and its governing equation is derived. After verifying tha...
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This paper presents control characteristics of a semi-active magneto-rheological (MR) fluid damper for a passenger vehicle. A cylindrical MR damper is devised and its governing equation is derived. After verifying that the damping force of the MR damper can be continuously tuned by the intensity of the magnetic field, PID controller is employed to achieve the desired damping force. The proposed MR damper is then applied to a full-car model and performance characteristics of the full-car such as vertical acceleration of the body are evaluated via hardware-in-the-loop-simulations(HILS).
This paper presents a novel float-encoded genetic algorithm and applies it to the optimal control of flexible smartstructures bonded with piezoelectric actuators and sensors. A performance function is initially devel...
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This paper presents a novel float-encoded genetic algorithm and applies it to the optimal control of flexible smartstructures bonded with piezoelectric actuators and sensors. A performance function is initially developed, based on the maximization of dissipation energy due to a control action. Then, according to this characteristic, a float-encoded genetic algorithm is presented which is capable of solving this optimization problem reliably and efficiently. The optimization algorithm that is developed for the control of flexible systems allows an integrated determination of actuator and sensor locations and feedback gains. The paper demonstrates the suitability of the proposed technique through its application to three standard benchmark test functions and a collocated cantilever beam.
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