• Title, Summary, Keyword: structural control

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Suboptimal control strategy in structural control implementation

  • Xu, J.Y.;Li, Q.S.;Li, G.Q.;Wu, J.R.;Tang, J.
    • Structural Engineering and Mechanics
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    • v.19 no.1
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    • pp.107-121
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    • 2005
  • The suboptimal control rule is introduced in structural control implementation as an alternative over the optimal control because the optimal control may require large amount of processing time when applied to complex structural control problems. It is well known that any time delay in structural control implementation will cause un-synchronized application of the control forces, which not only reduce the effectiveness of an active control system, but also cause instability of the control system. The effect of time delay on the displacement and acceleration responses of building structures is studied when the suboptimal control rule is adopted. Two examples are given to show the effectiveness of the suboptimal control rule. It is shown through the examples that the present method is easy in implementation and high in efficiency and it can significantly reduce the time delay in structural control implementation without significant loss of performance.

Optimal Structural Design for Flexible Space Structure with Control System Based on LMI

  • Park, Jung-Hyen;Cho, Kyeum-Rae
    • Journal of Mechanical Science and Technology
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    • v.16 no.1
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    • pp.75-82
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    • 2002
  • A simultaneous optimal design problem of structural and control systems is discussed by taking a 3-D truss structure as an object. We use descriptor forms for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. We consider a minimum weight design problem for structural system and disturbance suppression problem for the control system. The structural objective function is the structural weight and the control objective function is $H_{\infty}$ norm from the disturbance input to the controlled output in the closed-loop system. The design variables are cross sectional areas of the truss members. The conditions for the existence of controller are expressed in terms of linear matrix inequalities (LMI) By minimizing the linear sum of the normalized structural objective function and control objective function, it is possible to make optimal design by which the balance of the structural weight and the control performance is taken. We showed in this paper the validity of simultaneous optimal design of structural and control systems.

Decentralized energy market-based structural control

  • Lynch, Jerome Peter;Law, Kincho H.
    • Structural Engineering and Mechanics
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    • v.17 no.3_4
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    • pp.557-572
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    • 2004
  • Control systems are used to limit structural lateral deflections during large external loads such as winds and earthquakes. Most recently, the semi-active control approach has grown in popularity due to inexpensive control devices that consume little power. As a result, recently designed control systems have employed many semi-active control devices for the control of a structure. In the future, it is envisioned that structural control systems will be large-scale systems defined by high actuation and sensor densities. Decentralized control approaches have been used to control large-scale systems that are too complex for a traditional centralized approach, such as linear quadratic regulation (LQR). This paper describes the derivation of energy market-based control (EMBC), a decentralized approach that models the structural control system as a competitive marketplace. The interaction of free-market buyers and sellers result in an optimal allocation of limited control system resources such as control energy. The Kajima-Shizuoka Building and a 20-story benchmark structure are selected as illustrative examples to be used for comparison of the EMBC and centralized LQR approaches.

A semi-active acceleration-based control for seismically excited civil structures including control input impulses

  • Chase, J. Geoffrey;Barroso, Luciana R.;Hunt, Stephen
    • Structural Engineering and Mechanics
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    • v.18 no.3
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    • pp.287-301
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    • 2004
  • Structural acceleration regulation is a means of managing structural response energy and enhancing the performance of civil structures undergoing large seismic events. A quadratic output regulator that minimizes a measure including the total structural acceleration energy is developed and tested on a realistic non-linear, semi-active structural control case study. Suites of large scaled earthquakes are used to statistically quantify the impact of this type of control in terms of changes in the statistical distribution of controlled structural response. This approach includes the impulses due to control inputs and is shown to be more effective than a typical displacement focused control approach, by providing equivalent or better performance in terms of displacement and hysteretic energy reductions, while also significantly reducing peak story accelerations and the associated damage and occupant injury. For earthquake engineers faced with the dilemma of balancing displacement and acceleration demands this control approach can significantly reduce that concern, reducing structural damage and improving occupant safety.

Feedback control strategies for active control of noise inside a 3-D vibro-acoustic cavity

  • Bagha, Ashok K.;Modak, Subodh V.
    • Smart Structures and Systems
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    • v.20 no.3
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    • pp.273-283
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    • 2017
  • This paper presents and compares three feedback control strategies for active control of noise inside a 3-D vibro-acoustic cavity. These are a) control strategy based on direct output feedback (DOFB) b) control strategy based on linear quadratic regulator (LQR) to reduce structural vibrations and c) LQR control strategy with a weighting scheme based on structural-acoustic coupling coefficients. The first two strategies are indirect control strategies in which noise reduction is achieved through active vibration control (AVC), termed as AVC-DOFB and AVC-LQR respectively. The third direct strategy is based on active structural-acoustic control (ASAC). This strategy is an LQR based optimal control strategy in which the coupling between the various structural and the acoustic modes is used to design the controller. The strategy is termed as ASAC-LQR. A numerical model of a 3-D rectangular box cavity with a flexible plate (glued with piezoelectric patches) and with other five surfaces treated rigid is developed using finite element (FE) method. A single pair of collocated piezoelectric patches is used for sensing the vibrations and applying control forces on the structure. A comparison of frequency response function (FRF) of structural nodal acceleration, acoustic nodal pressure, and piezoelectric actuation voltage is carried out. It is found that the AVC-DOFB control strategy gives equal importance to all the modes. The AVC-LQR control strategy tries to consume the control effort to damp all the structural modes. It is seen that the ASAC-LQR control strategy utilizes the control effort more intelligently by adding higher damping to those structural modes that matter more for reducing the interior noise.

Simultaneous Optimal Design of Control-Structure Systems for 2-D Truss Structure (2차원 트러스 구조물에 대한 제어/구조 시스템의 동시최적설계)

  • Park, Jung-Hyen;Kim, Soon-Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.7 no.10
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    • pp.812-818
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    • 2001
  • This paper proposes an optimum design method of structural and control systems, taking a 2-D truss structure as an example. The structure is supposed to be subjected to initial static loads and disturbances. For the structure, a FEM model is formed, and using modal transformation, the equation of motion is transformed into that of modal coordinates in order to reduce the D.O.F. of the FEM model. The structure is controlled by an output feedback $H^$\infty$$ controller to suppress the effect of the disturbances. The design variables of the simultaneous optimal design of control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H^$\infty$$ norm, that is, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been carried out. Through the consideration of structural weight and $H^$\infty$$ norm, an advantage of the simultaneous optimum design of structural and control systems is shown. Moreover, while the optimized performance index of control is almost kept, we can acquire better design of structural strength.

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Decentralized civil structural control using real-time wireless sensing and embedded computing

  • Wang, Yang;Swartz, R. Andrew;Lynch, Jerome P.;Law, Kincho H.;Lu, Kung-Chun;Loh, Chin-Hsiung
    • Smart Structures and Systems
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    • v.3 no.3
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    • pp.321-340
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    • 2007
  • Structural control technologies have attracted great interest from the earthquake engineering community over the last few decades as an effective method of reducing undesired structural responses. Traditional structural control systems employ large quantities of cables to connect structural sensors, actuators, and controllers into one integrated system. To reduce the high-costs associated with labor-intensive installations, wireless communication can serve as an alternative real-time communication link between the nodes of a control system. A prototype wireless structural sensing and control system has been physically implemented and its performance verified in large-scale shake table tests. This paper introduces the design of this prototype system and investigates the feasibility of employing decentralized and partially decentralized control strategies to mitigate the challenge of communication latencies associated with wireless sensor networks. Closed-loop feedback control algorithms are embedded within the wireless sensor prototypes allowing them to serve as controllers in the control system. To validate the embedment of control algorithms, a 3-story half-scale steel structure is employed with magnetorheological (MR) dampers installed on each floor. Both numerical simulation and experimental results show that decentralized control solutions can be very effective in attaining the optimal performance of the wireless control system.

Stochastic optimal control of coupled structures

  • Ying, Z.G.;Ni, Y.Q.;Ko, J.M.
    • Structural Engineering and Mechanics
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    • v.15 no.6
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    • pp.669-683
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    • 2003
  • The stochastic optimal nonlinear control of coupled adjacent building structures is studied based on the stochastic dynamical programming principle and the stochastic averaging method. The coupled structures with control devices under random seismic excitation are first condensed to form a reduced-order structural model for the control analysis. The stochastic averaging method is applied to the reduced model to yield stochastic differential equations for structural modal energies as controlled diffusion processes. Then a dynamical programming equation for the energy processes is established based on the stochastic dynamical programming principle, and solved to determine the optimal nonlinear control law. The seismic response mitigation of the coupled structures is achieved through the structural energy control and the dimension of the optimal control problem is reduced. The seismic excitation spectrum is taken into account according to the stochastic dynamical programming principle. Finally, the nonlinear controlled structural response is predicted by using the stochastic averaging method and compared with the uncontrolled structural response to evaluate the control efficacy. Numerical results are given to demonstrate the response mitigation capabilities of the proposed stochastic optimal control method for coupled adjacent building structures.

Beam structural system moving forces active vibration control using a combined innovative control approach

  • Lee, Ming-Hui
    • Smart Structures and Systems
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    • v.12 no.2
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    • pp.121-136
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    • 2013
  • This study proposes an innovative control approach to suppress the responses of a beam structural system under moving forces. The proposed control algorithm is a synthesis of the adaptive input estimation method (AIEM) and linear quadratic Gaussian (LQG) controller. Using the synthesis algorithm the moving forces can be estimated using AIEM while the LQG controller offers proper control forces to effectively suppress the beam structural system responses. Active control numerical simulations of the beam structural system are performed to evaluate the feasibility and effectiveness of the proposed control technique. The numerical simulation results show that the proposed method has more robust active control performance than the conventional LQG method.

Structure-Control Combined Design with Structure Intensity

  • Park, Jung-Hyen;Kim, Soon-Ho
    • International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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    • v.6 no.1
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    • pp.60-68
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    • 2003
  • This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

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