A preliminary experimental investigation on the problem of viscous heating of fluid dampers that find applications in the vibration reduction of civil engineering structures is presented in this paper. Time histories ...
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A preliminary experimental investigation on the problem of viscous heating of fluid dampers that find applications in the vibration reduction of civil engineering structures is presented in this paper. Time histories of the temperatures are recorded near the piston head and at the outer surface of a 3-kip fluid damper that undergoes harmonic loading. The experimental results uncover some of the limitations of simple analytical expressions that have been derived in the past based on one-dimensional approximations of the energy balance equation.
Future advanced fixed- and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart microsensors to monitor flight integrity and provide flight control inputs. This paper provides an overview of Ho...
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Future advanced fixed- and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart microsensors to monitor flight integrity and provide flight control inputs. This paper provides an overview of Honeywell's MEMS technologies for aerospace applications of sensing and control. A unique second-generation polysilicon resonant microbeam sensor design is described. It incorporates a micron-level vacuum-encapsulated microbeam to optically sense aerodynamic parameters and to optically excite the sensor pickoff. Optically excited self-resonant microbeams form the basis for a new class of versatile, high-performance, low-cost MEMS sensors that uniquely combine silicon microfabrication technology with optoelectronic technology that can sense dynamic pressure, acceleration forces, acoustic emission (AE), and many other aerospace parameters of interest. Honeywell's recent work in MEMS tuning fork gyros for inertial sensing and a MEMS free-piston engine are also described.
A design method of hybrid damping is proposed here. Values of design parameters of hybrid damping: active control gain, number and location of piezo-elements to be used to passive damping, are determined under equal v...
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A design method of hybrid damping is proposed here. Values of design parameters of hybrid damping: active control gain, number and location of piezo-elements to be used to passive damping, are determined under equal vibration suppression performance condition. Vibration suppression performance is evaluated by using the gain of the accelerance transfer function of the closed loop system in modal space. According to the proposed design method, the equal vibration suppression performance with less active control power is achieved by hybrid damping. Availability of the proposed design method is experimentally demonstrated by using a flexible cantilever beam. The experimental results indicate that hybrid damping is effective comparing with fully active damping from the viewpoint of active control power under the equal vibration suppression performance condition.
This paper reports on the effect of using an analog feedback technique and electrode rotation on the Localized Electrochemical Deposition (LECD) process to enhance the spatial resolution and dimensional control during...
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ISBN:
(纸本)081943910X
This paper reports on the effect of using an analog feedback technique and electrode rotation on the Localized Electrochemical Deposition (LECD) process to enhance the spatial resolution and dimensional control during the growth of nickel micro-columns. Results shown here present the capability of the process for the fabrication of microstructures with high spatial resolution. Experiments were conducted on a specially assembled apparatus where nickel structures were electrodeposited onto Cu cathodes from a nickel sulfamate plating solution, using a non-soluble anode electrode. In the first part of our work, growth of the columns was found to be zero, partial or complete depending on the vertical traverse speed of the microelectrode away from the horizontal copper surface. In this case, dimensional control was limited. Efforts to overcome the said limitation in the second part achieved a constant growth rate with an analog closed-loop feedback control of the process. This improved technique produced columns with more even and controlled dimensions, therefore allowing for better spatial resolution of the structures. This was followed by deposition with electrode rotation, which produced columns with annulus cross-sections, indicating the existence of a uniform hollow core in the columns. This feature and dimensional control in the growth of the columns were not observed when using a stationary electrode - a novel development in the area of LECD and a possibility of fabricating micro-pipes for micro drug-delivery systems.
The near-field earthquake ground motion is characterized by high peak accelerations and velocity pulses with long period components as well as large ground displacements. Such characteristics are responsible for sever...
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The near-field earthquake ground motion is characterized by high peak accelerations and velocity pulses with long period components as well as large ground displacements. Such characteristics are responsible for severe damages to flexible structures. The peak ground acceleration occurs in the form of a shock, rather than a gradual build-up. As a result, passive dampers may not dissipate energies quick enough to prevent a serious damage to structures. Recently, a resetting or switching semi-active stiffness damper (RSASD or SSASD) and a semi-active electromagnetic friction damper (SAEMFD) have been shown to be effective in reducing the structural response due to dynamic loads. In this paper, the performance and effectiveness of these two semi-active hybrid isolation systems are studied extensively for base-isolated buildings subject to near-field earthquakes. Numerical results clearly demonstrate that these two semi-active dampers are effective in protecting the integrity of base-isolated structures during near-field earthquakes.
The proceedings contains 57 papers from the Damage and Fracture Mechanics VI: Computer Aided Assessment and control. The topics discussed include: the bridged external circular crack;numerical analysis of fracture in ...
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The proceedings contains 57 papers from the Damage and Fracture Mechanics VI: Computer Aided Assessment and control. The topics discussed include: the bridged external circular crack;numerical analysis of fracture in smart composite structures;evaluation of fracture parameters for functionally graded materials;a mechanical model for compressed concrete in R/C beams;J-estimation for single-edge-notch tension specimens subjected to fixed-grip loading;stress intensity factor analysis for an interface crack between dissimilar isotropic materials under thermal stress.
The design, manufacture, and testing of a low-cost, flexible, planar composite piezoceramic actuator device will be presented. The actuator uses interdigitated electrodes for poling and subsequent actuation of an inte...
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The design, manufacture, and testing of a low-cost, flexible, planar composite piezoceramic actuator device will be presented. The actuator uses interdigitated electrodes for poling and subsequent actuation of an internal layer of machined piezoceramic fibers. The fiber sheets are formed from monolithic piezoceramic wafers and conventional computer controlled wafer-dicing methods. The fabrication and use of fiber sheets allows precise handling and alignment of piezoceramic fibers during subsequent phases of actuator assembly. Tests show that the actuator is capable of producing large, directional in-plane strains;on order of 2000 parts-per-million under a 4000 V peak-to-peak applied voltage cycle. Preliminary endurance testing indicates that the device is relatively durable, with no reductions in free-strain performance up to 90 million electrical cycles.
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 rou...
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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.
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).
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.
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