Recent development of a smartstructures module and its successful integration with a multidisciplinary design optimization software ASTROS and an Aeroservoelasticity (ASE) module is presented. A modeled F-16 wing usi...
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Recent development of a smartstructures module and its successful integration with a multidisciplinary design optimization software ASTROS and an Aeroservoelasticity (ASE) module is presented. A modeled F-16 wing using piezoelectric (PZT) actuators was used as an example to demonstrate the integrated software capability to design a flutter suppression system. For an active control design, neural network based robust controller will be used for this study. A smartstructures module is developed by modifying the existing thermal loads module in ASTROS in order to include the effects of the induced strain due to piezoelectric (PZT) actuation. The thermal-PZT equivalence model enables the modifications of the thermal stress module to accommodate the smartstructures module in ASTROS. ZONA developed the control surface (CS) / PZT equivalence model principle, which ensures the interchangeability between the CS force input and the PZT force input to the ASE modules in ASTROS. The results show that the neural net based controller can increase the flutter speed.
Arrays of sensors and actuators designed to provide robust broadband feedback control with high performance and limited modeling are the subject of this paper. The reconfigurable array technique proposed here enables ...
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Arrays of sensors and actuators designed to provide robust broadband feedback control with high performance and limited modeling are the subject of this paper. The reconfigurable array technique proposed here enables the design of reduced-order controllers for complex structures and offers the potential to improve closed-loop robustness and to broaden the region of good performance even as the plant changes. The weighted summation of sensor signals senses the modes that are relevant to performance while rejecting the remaining modes; therefore reducing the required complexity of the controller. These weights are obtained from the minimization of a cost function and under certain assumptions; it can be shown that a single optimum solution exists. The use of reconfigurable arrays is motivated by the need to control the vibration of complex structures. A thirty element collocated actuator and sensor array was bonded to a cylinder section. Array weights were computed and successfully applied to isolate target modes. Different methods of computing the weights are implemented and compared. The deleterious effects of spatial aliasing and the performance as a function of the array size are experimentally explored.
An overview of different manufacturing processes available for the fabrication of active laminates and sandwich structures with integrated piezoelectric actuators as the active control elements is presented. The so-ca...
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An overview of different manufacturing processes available for the fabrication of active laminates and sandwich structures with integrated piezoelectric actuators as the active control elements is presented. The so-called in situ fabrication for active laminates is described in more detail with respect to the fabrication of composite structures made of electric conducting and electric insulating fibre reinforced composites. In addition, active composite structures build with the in situ fabrication method introduced are presented.
The optimal control algorithm is one of the feasible feedback algorithms for vibration suppression of flexible structures. One of the commonly encountered problems of the optimal control implementation is the spillove...
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The optimal control algorithm is one of the feasible feedback algorithms for vibration suppression of flexible structures. One of the commonly encountered problems of the optimal control implementation is the spillover problem. The spillover generally occurs when modeling a continuous structure that has infinite number of resonance modes as a nominal model with finite modes for controller design. This paper presents a design of an optimal controller that is low order and can prevent the spillover problem when the unmodeled resonance modes perturb the feedback control loop. For low order controller design, this paper proposes modal Hankel singular values (MHSV) for efficient nominal model reduction. Low order controller can be derived from the reduced nominal model. For design of more stable controller, this paper applies frequency dependant weight functions to the cost function. The weight functions prevent the spillover by making optimal controller not to excite the resonance modes that are not included in nominal model. The optimal controller is derived the nominal model. This weight function approach optimizes the control performance and control stability by smoothening the discrepancy between the weights on the modeled modes to be controlled and unmodeled modes to be stabilized. A finite element model is exploited to develop the controller and to test its control performance and stability against high resonance mode spillover.
This paper is to present a numerical program of dynamic control for suppressing external disturbance to variable thickness beam-plates with sensors and actuators of piezoelectric layers on/in the structures using the ...
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This paper is to present a numerical program of dynamic control for suppressing external disturbance to variable thickness beam-plates with sensors and actuators of piezoelectric layers on/in the structures using the scaling function transform of the Daubechies wavelet theory for approximation of functions. After the generalized Gaussian integral is applied to the scaling function transform, an explicit expression of identification of deflection configuration of the structures is expressed by the electric charge/current signals measured from the piezoelectric sensors. When a control law of negative feedback of the identified deflection and velocity signals is employed, the wavelet Galerkin method or wavelet weighted residual method is used to determine control voltage applied on the piezoelectric actuators. Due to that the scaling function transform is like a low-pass filter which can automatically filter out high-order signals of vibration or disturbance from the measurement and the controller employed here, this control approach does not lead to the undesired phenomenon of control instability that is often generated in a control system and caused by the spilling over of high-order signals from measurement and controller if no special technique is used in the control system. Some numerical simulations are carried out to show the efficiency of the proposed approach.
A rigorous multi-objective optimization procedure, is developed to address the integrated structures/control design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatment. T...
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A rigorous multi-objective optimization procedure, is developed to address the integrated structures/control design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatment. The Kresselmeier-Steinhauser function approach is used to formulate this multidisciplinary problem. The goal is to control vibration without incorporating a weight penalty. Objective functions and constraints include damping ratios, structural weight and natural frequencies. Design variables include the ply stacking sequence, dimensions and placement of segmented ACL. The optimal designs show improved plate vibratory characteristics and reduced structural weight. The results of the multi-objective optimization problem are compared to those of a single objective optimization with vibration control as the objective. Results establish the necessity for developing the integrated structures/controls optimization procedure.
An analytical method is given for the determination of the eigenfunctions and eigenfrequencies for one-dimensional structural vibration problems in the presence of patch sensors and patch actuators. The method is base...
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An analytical method is given for the determination of the eigenfunctions and eigenfrequencies for one-dimensional structural vibration problems in the presence of patch sensors and patch actuators. The method is based on converting the differential equation formulation of the problem to an integral equation formulation. The conversion is accomplished by introducing an explicit Green's function. The Green's function consists of two parts, one taking account of the stiffness and the other taking account of the control moments induced by the distributed actuators. The control moments involve piezoelectric constants and feedback voltages made up of gains times the sensor signals. Obtaining the eigenvalues and eigenfunctions of this integral equation gives the solution to the piezo-control problem.
This paper describes an active control system for reducing the vibration of a pair of meshing gears caused by the variation of meshing stiffness. A gear meshing model is developed and used to determine the magnitude o...
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This paper describes an active control system for reducing the vibration of a pair of meshing gears caused by the variation of meshing stiffness. A gear meshing model is developed and used to determine the magnitude of the secondary force required to cancel gear vibration and this is shown to be related to the modulation index of meshing stiffness. Possible configurations of actuators and sensors to implement the control scheme are proposed and some experimental results are presented.
Soil-structure interaction (SSI) has gained significant recognition of importance in the control of seismically excited structures in the past ten years. In this paper, recent developments of the SSI effect on the per...
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Soil-structure interaction (SSI) has gained significant recognition of importance in the control of seismically excited structures in the past ten years. In this paper, recent developments of the SSI effect on the performance of passive, semi-active and active control strategy are summarized in general. It is followed by a short presentation on the seismic effectiveness of tuned mass dampers, variable stiffness devices and active control systems in reducing the maximum response of structures with the intent of comparing the SSI effect on various devices and control systems. Numerical studies on a 3- and a 12-story frame structure resting on a viscoelastic half space indicated that SSI tends to defeat the effectiveness of control systems. This defeat is primarily because the damping of a soil-structure system increases and the structure vibrates more like a rigid body as the soil material softens. Since nearly all devices made of smartmaterials either passively or actively respond to the structural deformation, their performance is likely to degrade for flexible-base structures.
A systematic method is presented for optimal integration of smart (active) materials based actuators into the structure of robot manipulators for the purpose of minimizing the high harmonic components of the required ...
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A systematic method is presented for optimal integration of smart (active) materials based actuators into the structure of robot manipulators for the purpose of minimizing the high harmonic components of the required actuating torques (forces). The approach is based on the Trajectory Pattern Method (TPM). With properly synthesized low harmonic motion trajectories and by minimizing the high harmonic components of the required actuating torques with properly sized and placed smart actuators, such computer controlled machines can operate at higher speeds, greater tracking precision and minimal vibration and control problems.
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