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Evaluation of a real-time hybrid simulation system for performance evaluation of structures with rate dependent devices subjected to seismic loading

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ENGINEERING STRUCTURES 2012年 35卷 71-82页

作者： Chen, Cheng Ricles, James M. Karavasilis, Theodore L. Chae, Yunbyeong Sause, Richard ATLSS Engn Res Ctr Bethlehem PA 18015 USA San Francisco State Univ Sch Engn San Francisco CA 94132 USA Univ Warwick Sch Engn Coventry CV4 7AL W Midlands England

Real-time hybrid simulation is a viable experiment technique to evaluate the performance of structural systems subjected to earthquake loads. This paper presents details of the real-time hybrid simulation system developed at Lehigh University, including the hydraulic actuators, the IT control architecture, an integration algorithm and actuator delay compensation. An explicit integration algorithm provides a robust and accurate solution to the equations of motion while an adaptive inverse compensation method ensures the accurate application of the command displacements to experimental substructure(s) by servo-hydraulic actuators. Experiments of a steel moment resisting frame with magneto-rheological fluid dampers in passive-on mode were conducted using the real-time hybrid simulation system to evaluate the ability for the simulation method to evaluate the nonlinear seismic response of steel frame systems with dampers that are intended to enhance the response of the structure. The comparison with numerical simulation results demonstrates that the real-time hybrid simulation system produces accurate and reliable experimental results and therefore shows great potential for structural performance evaluation in earthquake engineering research. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Real-time Hybrid simulation integration algorithm Compensation

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Analytical modeling of sensor quantization in strapdown inertial navigation error equations

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2002年第5期25卷 833-842页

作者： Savage, PG Strapdown Assoc Inc Maple Plain MN 55359 USA

Although generally not considered a major contributor to system inaccuracy, inertial sensor quantization error, if not properly modeled, can lead to erroneously large estimates of its impact on inertial navigation system performance. Analytical methods are described for modeling inertial sensor quantization in strapdown inertial system error parameter propagation and measurement equations. Error propagation equations are derived in classical differential error state dynamic and discrete difference format. It is shown how the attitude, velocity, and sensor error parameters in these equations must be modified to enable proper sensor quantization error modeling as white noise and to account for differences in attitude, velocity, and position update frequencies. The discrete difference error equation form is used to develop values for attitude/velocity measurement noise covariances and for spectral densities of white quantization noise terms in the differential error propagation equations. A general discussion is included of how quantization white noise spectral densities should be computed for the differential error propagation equations for compatibility with two-speed attitude, velocity, and position updating algorithms. Validity limits for white noise modeling approximations and methods for reducing quantization noise are discussed. Numerical examples are provided.

关键词： Inertial Sensor Strapdown Inertial Navigation System White Noise Spectral Density Aeronautical Engineering Aerospace Industry Accelerometer Earth Strapdown System integration algorithm

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Trajectory optimization for air-to-surface missiles with imaging radars

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2002年第5期25卷 876-887页

作者： Farooq, A Limebeer, DJN MBDA UK Ltd Seeker Div Borehamwood WD6 1RX Herts England Univ London Imperial Coll Sci Technol & Med Dept Elect & Elect Engn London SW7 2BT England

The use of trajectory optimization techniques is presented for the terminal guidance of an air-to-surface missile using a Doppler beam sharpening (DBS) radar seeker. The terminal guidance problem is characterized by a stealthy terrain-following phase that is followed by a climb and dive onto the target (a "bunt" trajectory). The imaging properties of DBS radars impose additional azimuth plane constraints on the trajectory that have to be incorporated into the optimization process. The various mission phases are interrelated, and the performance objectives come into conflict with the hardware constraints. The trajectory optimizer is used to generate offline open-loop controls that satisfy the various mission requirements. Numerical examples are used to illustrate the method and its efficacy.

关键词： Trajectory Optimization Air to Surface Missiles Synthetic Aperture Radar Target Acquisition Roll Control Numerical Optimization Sequential Quadratic Programming Closed Loop Autopilot integration algorithm

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Tuning of coning algorithms to gyro data frequency response characteristics

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2001年第4期24卷 641-647页

作者： Mark, JG Tazartes, DA Litton Guidance & Control Syst Woodland Hills CA 91367 USA

Substantial efforts have gone into the development of sophisticated algorithms that reduce system drift errors in the presence of coning motion. Present-day algorithms form high-order coning correction terms using multiple incremental angle outputs from the gyros. These algorithms assume a hat transfer function for the processing of the incremental angle outputs and are structured to yield very high-order responses. However, these algorithms do not address the issue of nonideal gyro frequency response or of filtered gyro data. Many gyros exhibit complex frequency responses and violate the assumptions used in deriving the previously developed coning algorithms. The mismatch between the assumed and actual frequency response of the gyro data leads to degradation of performance in a coning environment as well as amplification of pseudoconing errors. A method of deriving algorithms that are tailored to the frequency response of the particular type of gyros used is presented. These algorithms can be designed to arbitrarily high order and can also supply an extremely sharp high-frequency cutoff to minimize pseudo-coning errors. Additionally, this method can be used to design coning algorithms that are tuned to deliberately filtered gyro data. The technique developed equally applies to mechanical, fiber-optic, and other types of gyros.

关键词： Frequency Response Functions Quaternions Laser Gyroscopes integration algorithm Taylor Series Strapdown Inertial Navigation System Navigation Performance Strapdown System Angular Motion

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Vibrations of an Axially Moving Beam with Deployment or Retraction

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AIAA JOURNAL 2013年第3期51卷 686-696页

作者： Park, Sungpil Yoo, Hong Hee Chung, Jintai Hanyang Univ Dept Mech Engn Ansan 425791 Kyeonggi Do South Korea Hanyang Univ Sch Mech Engn Seoul 133791 South Korea

The longitudinal and transverse vibrations of an axially moving beam are analyzed when the beam has deploying or retracting motion. Comparing the previous studies in which only the transverse displacement is considered, the present study simultaneously considers the longitudinal and transverse displacements when deriving the equations of motion. To include a nonlinear effect, the nonlinear von Karman strain theory is adopted. The derived equation of longitudinal motion is linear and uncoupled with the transverse motion, whereas the equation of transverse motion is nonlinear and coupled with the longitudinal motion. After computing numerical solutions from the equations, the longitudinal and transverse vibrations are analyzed with regard to the moving speed and acceleration of the beam. In addition, the present nonlinear analysis of a moving beam is compared with a previous linear analysis for the variations of the moving acceleration, moving speed, and Young's modulus. The linear and nonlinear vibration analyses result in considerably different dynamic responses when the moving acceleration is large or when Young's modulus is small.

关键词： Longitudinal Vibrations Young's Modulus Dynamic Response Computing Finite Element Analysis Euler Bernoulli Beam Theory Galerkin Method Beam (Structures) Kinetic Energy integration algorithm

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Computations of axisymmetric plug-nozzle flowfields: Flow structures and thrust performance

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JOURNAL OF PROPULSION AND POWER 2002年第2期18卷 254-260页

作者： Ito, T Fujii, K Hayashi, AK Univ Tokyo Dept Aeronaut & Astronaut Bunkyo Ku Tokyo 1138654 Japan Inst Space & Astronaut Sci Kanagawa 2298510 Japan Aoyama Gakuin Univ Dept Engn Mech Tokyo 1578527 Japan

Plug-nozzle flowfields are analyzed by the numerical simulations. The method of characteristics is used to design the plug contour, and several types of plug nozzles are considered by truncating the length of the nozzle at different positions. Plug-nozzles' altitude-compensating features are confirmed by the computed results, and the base pressure turns out to play an important role to maintain the thrust performance of the nozzle for high-truncation configurations. The altitude clearly influences the base-pressure distributions under the assumption that the chamber pressure is constant during the ascent. The computed thrust difference between the contoured and the conical nozzle linearly increased as a function of the pressure ratio. The thrust performance of the contoured plug nozzle is estimated to be about 5-6% higher than the conical plug nozzle. Various conditions of external flows over the plug nozzle are also imposed, and the result shows that the external flow does not influence the pressure distribution on the nozzle surface for the pressure ratios higher than the designed point.

关键词： Contoured Plug Nozzle Mach Number Numerical Simulation Chamber Pressure Oblique Shock Wave Baldwin Lomax Turbulence Model Primitive Variable Navier Stokes Equations integration algorithm Propulsion System

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TEMPORAL AND ACOUSTIC ACCURACY OF AN IMPLICIT UPWIND METHOD FOR DUCTED FLOWS

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AIAA JOURNAL 1991年第11期29卷 1860-1867页

作者： RIDDER, JP BEDDINI, RA University of Illinois at Urbana-Champaign Urbana Illinois 61801

An implicit, time-accurate method for ducted-flow aeroacoustics is presented. The method is unfactored, using line Gauss-Seidel relaxation and multiple axial sweeps for convergence of each time step. First- or higher-order upwind spatial differencing is accomplished using either a modified form of van Leer's flux vector splitting or Roe's flux difference splitting on the inviscid terms of the governing equations. A general time integration algorithm is employed, which encompasses several schemes including the Euler implicit method used for the current work. Results are presented from three numerical tests with comparisons being made to both theory and experiment. These spatial and temporal accuracy tests show excellent tracking of the acoustic wave speed using Roe's flux difference splitting. The method is further seen to reflect waves properly as demonstrated by comparison of computed pressure amplitudes and acoustic mode shapes with experimental data. Additionally, no low mean-flow Mach number convergence limitation is observed. No Courant number stability restriction is displayed, as accurate results are obtained utilizing Courant numbers of order 10(2) for these tests.

关键词： Explicit Methods Aerodynamics integration algorithm Aeroacoustics Axisymmetric Flow Crank Nicolson Method Navier Stokes Equations Conservation of Mass Boundary Layer Analysis Aspect Ratio

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Space-marching method on unstructured grid for supersonic flows with embedded subsonic regions

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AIAA JOURNAL 1997年第8期35卷 1280-1285页

作者： Nakahashi, K Saitoh, E Tohoku University Sendai 980-77 Japan

A space-marching algorithm on an unstructured grid to solve supersonic flows that may contain embedded subsonic regions is proposed. The method employs a domain-marching algorithm in which a bandlike computational subdomain is marched in the hyperbolic direction starting from the upstream boundary of the flowfield. A masking procedure is employed where the outside of the selected domain is masked during the flux computations to minimize the overall arithmetic operations. The unmasked domain is integrated in time to get a locally converged solution. If embedded subsonic regions are present, the unmasked region is enlarged to cover the entire subsonic regions surrounded by supersonic points. The method is applied to calculations of a fully supersonic flow in a scramjet and a supersonic flow with embedded subsonic regions around a blunt-nose body. It is demonstrated that the computational work can be reduced by as much as a factor of 10 as compared to conventional, time-marching unstructured grid methods.

关键词： Unstructured Grid Supersonic Flow Scramjet Primitive Variable Freestream Mach Number integration algorithm Angle of Attack Computing Supersonic Speed Total Energy

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Comparative studies of vibration control effects between structures with particle dampers and tuned liquid dampers using substructure shake table testing methods

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SOIL DYNAMICS AND EARTHQUAKE ENGINEERING 2019年 121卷 421-435页

作者： Fu, Bo Jiang, Huanjun Wu, Tao Changan Univ Sch Civil Engn Xian 710061 Shaanxi Peoples R China Tongji Univ Coll Civil Engn Shanghai 200092 Peoples R China

This paper compares the vibration control performance of particle dampers (PDs) and tuned liquid dampers (TLDs) by using the up-to-date substructure shake table testing (SSTT) method. In implementing the SSTT, three representative model-based integration algorithms, whose algorithmic parameters are functions of the complete model of the structure system to enable unconditional stability to be achieved within the framework of an explicit formulation, are adopted. The experimental procedures of the SSTT methods using the three integration algorithms are presented. The SSTT system of the single-degree-of-freedom (SDOF) structures with PDs/TLDs is constructed and verified by comparing the experimental results of the SSTTs and the corresponding complete structure shake table tests. The vibration reduction effects of PDs and TLDs with the same mass ratio are investigated and compared by conducting a series of SSTTs of the SDOF systems with such devices under the excitation of ground motion. The influences of mass ratio, damping ratio and structural frequency on control efficiency of PDs and TLDs are studied. The results from the parametric analyses demonstrate that all the aforementioned factors have significant impacts on the vibration control performance of both dampers. Most experimental results indicate that the PDs have better vibration control performance than the counterpart TLDs.

关键词： Substructure shake table testing Particle damper Tuned liquid damper Vibration control integration algorithm

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Geometric integrators for multiplicative viscoplasticity: Analysis of error accumulation

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2010年第9-12期199卷 700-711页

作者： Shutov, A. V. Kreissig, R. Tech Univ Chemnitz Inst Mech & Thermodynam D-09111 Chemnitz Germany

The inelastic incompressibility is a typical feature of metal plasticity/viscoplasticity. Over the last decade, there has been a great amount of research related to construction of numerical integration algorithms which exactly preserve this property. In this paper we examine, both numerically and mathematically, the excellent accuracy and convergence characteristics of such integrators. In order to simplify the considerations, we consider strain-driven processes without hardening effects. In terms of a classical model of multiplicative viscoplasticity, we illustrate the notion of exponential stability of the exact solution. We show that this property enables the construction of effective and stable numerical algorithms, if the incompressibility is exactly satisfied. On the other hand, if the incompressibility constraint is violated, spurious degrees of freedom are introduced. In general, this results in the loss of the exponential stability and a dramatic deterioration of convergence of numerical methods. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Viscoplasticity Finite strains Contractivity Exponential stability Inelastic incompressibility integration algorithm Error accumulation

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