Research continues in exploring active control techniques to calm resonant floor vibrations. In this research, an electromagnetic proof-mass actuator is used to deliver the control force in a single-input/multi-output...
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Research continues in exploring active control techniques to calm resonant floor vibrations. In this research, an electromagnetic proof-mass actuator is used to deliver the control force in a single-input/multi-output control strategy. With the intent of improving the stability characteristics and the effectiveness of the SISO controller, the relative actuator mass displacement and the actuator mass velocity are added to the floor velocity output used in prior research by the author. Three separate performance indices are developed and implemented to illustrate their particular usefulness in designing an output feedback scheme for controlling pedestrian induced floor motion. The multi-output scheme has been shown analytically to further reduce steady-state acceleration amplitudes by a factor of 7 over the single-output scheme.
Current applications in active vibration control mainly use piezoceramic actuators (PZT). With the aim of improving vibration absorption, electrostrictive actuators have been elaborated. These electrostrictive ceramic...
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Current applications in active vibration control mainly use piezoceramic actuators (PZT). With the aim of improving vibration absorption, electrostrictive actuators have been elaborated. These electrostrictive ceramics show very attractive properties for active vibration control applications. Yet, their non linear electromechanical behavior tempers these numerous advantages and considerably complicate their use. In usual active vibration control applications, dynamic electric fields with varying magnitudes and frequencies are applied to the ceramic. Earlier measurements, performed at ONERA, show that the ceramic behavior is strongly sensitive to operating parameters (electric field magnitude and excitation frequency, and surrounding temperature). It is demonstrated in this article that this sensitivity can, in fact, be reduced to a sensitivity of the material to its own temperature. Indeed, a significant heating of electrostrictive ceramics occurs when they are subjected to a sinusoidal electric field. This heating turns out to be, itself, dependent on operating parameters. An experimental electric model of stressfree electrostrictive patches is presented, which is then used to develop constitutive relations of these materials. A simplified, dynamical, electromechanical coupled model of distributed electrostrictive patches bonded on a generic thin plate host structure is finally briefly discussed.
Experimental and analytical investigations conducted into active control of longitudinal and flexural waves transmitted through a cylindrical gearbox strut are presented in this article. The development of an experime...
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Experimental and analytical investigations conducted into active control of longitudinal and flexural waves transmitted through a cylindrical gearbox strut are presented in this article. The development of an experimental model of a finite length active cylindrical strut instrumented with sensors, piezoelectric, and magnetostrictive actuators is described. The strut is included in an experimental arrangement where vibratory loads are applied along the strut's longitudinal and transverse directions while it is subjected to an axial static loading. Modal analysis studies are carried out in the frequency range of 10 Hz to 5 kHz with a finite element model of the cylindrical strut and the experimental model. During wave transmission through the strut, coupling between different types of modes is predicted by analysis and observed in the experiments. Actuator and sensor systems issues are discussed with relevance for control of vibrations transmitted through helicopter gearbox struts.
In the present study, the fuzzy control of vibration is investigated for a hybrid smart composite beam actuated by piezoceramics and electro-rheological fluids (ERFs) actuators. A carbon fiber reinforced plastics cant...
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In the present study, the fuzzy control of vibration is investigated for a hybrid smart composite beam actuated by piezoceramics and electro-rheological fluids (ERFs) actuators. A carbon fiber reinforced plastics cantilevered beam containing ERF with bonded piezoceramics is vibrated under forced sinusoidal external excitation. A fuzzy model of the controlled element containing two actuators is formed because the application of a linear control theory to the vibration control is difficult due to intense nonlinearity in the ERF actuator. The parameters of the fuzzy model are identified by using a hybrid neuro-fuzzy system. The fuzzy controller for vibration suppression of the composite beam designed is based on the fuzzy model by using modern control theory. The effect of the vibration control system with a fuzzy controller is verified by simulation and experiment.
Coupling adjacent buildings with supplemental damping devices is a developing method of mitigating structural responses due to wind and seismic excitations. The concept is to allow structures, vibrating at different f...
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ISBN:
(纸本)0819436038
Coupling adjacent buildings with supplemental damping devices is a developing method of mitigating structural responses due to wind and seismic excitations. The concept is to allow structures, vibrating at different frequencies, to exert control forces upon one another to reduce the overall responses of the system. Previous studies have identified optimal coupled building configurations and have introduced passive, active and "smart" damping control strategies. This paper will focus on the application of "smart" dampers as coupling link devices to produce control forces between three tall buildings. smart dampers are semi-active dampers capable of changing their dynamic characteristics in real-time to allow for a variety of control forces to be produced without requiring significant energy. A clipped optimal control strategy is employed for the smart dampers that can provide increased performance, over a comparable passive control strategy, during moderately severe seismic events.
In this paper, a method based on finite element technique is developed for the design of sensor/actuator system of the active vibration control of shell structure. To prevent the adverse effect of spillover, distribut...
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In this paper, a method based on finite element technique is developed for the design of sensor/actuator system of the active vibration control of shell structure. To prevent the adverse effect of spillover, distributed modal sensor/actuator system is established using PVDF film. Although shell structure is three-dimensional structure, the PVDF sensor/actuator system can be treated as two-dimensional. The electrode patterns and lamination angle of PVDF sensor/actuator are optimized to design the modal sensor/actuator system. Finite element programs are developed to consider curved structures having PVDF modal sensor/actuator. The nine-node shell element with five nodal degree of freedoms is used for finite element discretization. Electrode patterns and lamination angles of PVDF sensor/actuator are optimized using genetic algorithm. Sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. Modal sensor/actuator for the first and second modes of singly curved cantilevered shell structure are designed using above mentioned methods. For the demonstration, numerical simulation of the closed loop system is performed. Discrete LQG method is used as a control law.
Conventionally electroded surface-bonded piezoceramic elements are incapable of controlling torsional motions because the in-plane isotropic actuation strain is orthogonal to the surface shear strain pattern associate...
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Conventionally electroded surface-bonded piezoceramic elements are incapable of controlling torsional motions because the in-plane isotropic actuation strain is orthogonal to the surface shear strain pattern associated with torsional deformations. For devices with in-plane orthotropic properties, however, such as those with interdigital electrodes (IDE), sensing and controlling torsion is possible, allowing damping by passive or active means. An electromechanical model is developed for orthotropic piezoceramic devices bonded to the surfaces of beams or tubes in torsion; expressions for mechanical compliance, actuator authority, electromechanical coupling, and passively attainable damping for the combined system are derived in terms of geometric and material parameters and orientations. Optimization of the actuator orientation and geometry is addressed, with specific attention to the width, spacing, and angle of interdigital electrodes. Experimentally determined damping ratios are presented for torsional IDE piezoceramic devices with passive shunts, along with considerations for future improvements.
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 us...
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ISBN:
(纸本)0819436038
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.
This paper presents a semi-active seat suspension with a magneto-rheological (MR) fluid damper, which is applicable to commercial vehicles such as a large size of truck. A cylindrical MR seat damper is designed and ma...
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This paper presents a semi-active seat suspension with a magneto-rheological (MR) fluid damper, which is applicable to commercial vehicles such as a large size of truck. A cylindrical MR seat damper is designed and manufactured by incorporating Bingham model of MR fluid. After evaluating field-dependent damping characteristics, the controllability of the damping force is experimentally demonstrated in time domain by implementing PID controller. A semi-active seat suspension system is then constructed and its governing equation of motion is derived. A skyhook control scheme is formulated in order to reduce vibration level at the driver's seat. The controlled responses such as acceleration transmissibility are evaluated in frequency domain. In addition, performance characteristics of a full-car model installed with the proposed MR seat suspension are evaluated via hardware-in-the-loop simulation (HILS).
A high-speed traversing mechanism using two electro-rheological clutches is described. An application of the traversing mechanism is in winding filaments onto bobbins. The traverse speed is 5 m/s; the required turn ro...
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A high-speed traversing mechanism using two electro-rheological clutches is described. An application of the traversing mechanism is in winding filaments onto bobbins. The traverse speed is 5 m/s; the required turn round period is 10 to 20 milli-seconds; the traverse length is 250 mm; the turn round position must be controllable and repeatable within ± 1 mm; and the traverse requires to be controlled to shape the resulting bobbin. These combined criteria of high speed and controllability makes the use of electro-rheological fluids an attractive proposition. The paper considers the optimisation of the traversing mechanism; both geometric and fluid parameters are considered. The limiting performance of the mechanism is detailed together with the effects on the precision of the mechanism. The paper also outlines control aspects of the mechanism and uses this to indicate important areas for consideration in the future development of electro-rheological fluids.
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