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1
Waghmare, Manisha V., Suhasini N. Madhekar, and Vasant A. Matsagar. "Influence of Nonlinear Fluid Viscous Dampers on Seismic Response of RC Elevated Storage Tanks." Civil Engineering Journal 6 (December 9, 2020): 98–118. http://dx.doi.org/10.28991/cej-2020-sp(emce)-09.
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The numerical investigation on the seismic response of RC elevated liquid storage tanks installed with viscous dampers is presented. A discrete two-mass model for the liquid and multi-degree of freedom system for staging, installed with the dampers are developed for Reinforced Concrete (RC) elevated liquid storage tanks. The elevated tank is assessed for seismic response reduction when provided with Linear Viscous Damper (LVD) and Nonlinear Viscous Damper (NLVD), installed in the staging. The RC elevated liquid storage tanks are analyzed for two levels of liquid containment in the tank, 100% and 25% of the tank capacity. Three Configurations of placements of dampers viz. dampers at alternate levels (Configuration I and Configuration II) and dampers at all the panels of the staging of the tank (Configuration III) are considered. To study the effect of peak ground acceleration, eight real earthquake time histories with accelerations varying from 0.1 g to 0.93 g are considered. The nonlinearity in the viscous damper is modified by taking force proportional to various velocity exponents. It is found that the nonlinear viscous dampers with lower damping constant result in a comparable reduction in the response of RC elevated liquid storage tank, to that of linear viscous dampers with higher damping constant. A lower damping constant signifies compact the size of the damper. Doi: 10.28991/cej-2020-SP(EMCE)-09 Full Text: PDF
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TROMBETTI, TOMASO, and STEFANO SILVESTRI. "ADDED VISCOUS DAMPERS IN SHEAR-TYPE STRUCTURES: THE EFFECTIVENESS OF MASS PROPORTIONAL DAMPING." Journal of Earthquake Engineering 8, no. 2 (March 2004): 275–313. http://dx.doi.org/10.1080/13632460409350490.
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Adhar Bagus, Muhammad, Azizan As’arry, Hesham Ahmed Abdul Mutaleb Abas, Abdul Aziz Hairuddin, and Mohd Khair Hassan. "Vibration control of FSAE quarter car suspension test rig using magnetorheological damper." Indonesian Journal of Electrical Engineering and Computer Science 17, no. 3 (March 1, 2020): 1281. http://dx.doi.org/10.11591/ijeecs.v17.i3.pp1281-1288.
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Recently MRF damper -which has a significant controllable damping force - used frequently in many active and semi-active suspension systems. However, MRF damper needs controller to estimate the desired force to dissipate the occurred vibration instantaneously. PID controller is one of the effective feedback controllers which shows robustness and simplicity in control MRF dampers, but still the parameters of the PID controller under study to find out the optimum values. This study focused on the vibration control using Magneto-rheological (MR) damper on a FSAE quarter car suspension test rig to study and obtain the optimum running condition. The test rig was designed, modified and then tested using a P-controller integrated with MR damper, unbalance mass used as disturbance and analyzed using LABVIEW software in time and frequency domains. The natural frequency obtained was 2.2 Hz were similar to the actual FSAE car natural frequency. Based on the acceleration against time graph with different proportional gain value the optimal value for proportional gain, Kp was 1. Hence, the experiment work could be used as the initial stage to study and develop a robust controller to suppress vibration on a car.
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Pawlak, Zdzisław M., and Roman Lewandowski. "The Effectiveness of the Passive Damping System Combining the Viscoelastic Dampers and Inerters." International Journal of Structural Stability and Dynamics 20, no. 12 (October 14, 2020): 2050140. http://dx.doi.org/10.1142/s0219455420501400.
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Passive damping systems are energy dissipating devices that are used in building constructions to reduce excessive vibration caused by wind or earthquakes. Recently, the use of inerters, devices using the inertia of the rotating mass, as a passive damping system has become more and more popular. Inerter, regardless of the construction, generates a resistance force that is proportional to the relative acceleration at the terminal ends of the device. The purpose of this study is to evaluate the effectiveness of the viscoelastic (VE) dampers in combination with the inerter. For the derived equations of motion of structures with VE dampers and inerters, the Laplace transformation is applied, which leads to a nonlinear eigenproblem. The solution to the eigenproblem is obtained using the continuation method, also known as the homotopy or as the path following method. It was found that for some cases of inerter connection with ve damper, there are some additional solutions in relation to the degrees of freedom of the structure. Furthermore, the dynamic characteristics of the structure associated with the above-mentioned additional eigenvalue are strongly dependent on the equivalent inerter mass. Damping efficiency is tested by determining changes in the system’s dynamic characteristics: natural frequencies, non-dimensional damping ratios and displacement transfer functions. The presented approach allows determining the appropriate parameters of the inerter and VE damper and their appropriate location on the structures that correspond to the most effective damping. The obtained numerical results confirm the effectiveness of the proposed approach.
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Szary, Marek L., and Peter Weber. "The Study of Behavior of Vibrating Systems Controllable by Devices with Rheological Fluid." Archives of Acoustics 38, no. 2 (June 1, 2013): 217–22. http://dx.doi.org/10.2478/aoa-2013-0026.
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Abstract The nonlinear mathematical model of behavior of controllable viscosity fluid (CVF) under applied external field is presented. A large family of these fluids is commonly used to control responding forces of dampers in vibration control applications. The responding force of a damper with CVF has two components. The first one - uncontrollable - is proportional to the viscosity of a base fluid and velocity of its motion, the second one, which is controllable, depends on the strength of the applied external field. Both are involved in the process of dissipation of unwanted energy from the vibrating systems. An equivalent damping factor based on the principle of energy dissipated during one cycle of damper work under a constant strength external field was calculated. When mass or stiffness is variable the equivalent damping factor can be set accordingly by adjusting the strength of external field to have vibrating damped system purposely/continuously working in the critical or other chosen state. This paper also presents cases of applying periodically changing strengths of an external field synchronized with cycles of periodical motion of the vibrating system to continuously control the damping force within each cycle.
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KOSTANTAKOPOULOS, T. G., and G. T. MICHALTSOS. "MODELING AND ANALYSIS OF A PLATE ON ELASTIC FOUNDATION SUBJECTED TO LANDING AIRPLANES' FORCES." International Journal of Structural Stability and Dynamics 10, no. 01 (March 2010): 37–54. http://dx.doi.org/10.1142/s0219455410003373.
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This paper deals with the problem of the dynamic behavior of a plate on elastic foundation under the action of forces produced by a landing airplane. A partially plastic impact is postulated for the contact between the airplane and the plate. The Winkler model is used to simulate the ground's elastic behavior, by which the foundation reaction is proportional to the plate deflection, along with dampers for energy dissipation. Two models are used for the airplane, i.e. a simplified mass-load model and a mass-dashpot-spring model, and their influences on the dynamic response of the plate are evaluated. Moreover, various parameters concerning the salient features of the airplane and its landing on the plate are studied with conclusions drawn. The efficiency of the methodology proposed herein was demonstrated in the numerical study.
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Trombetti, T., and S. Silvestri. "Novel schemes for inserting seismic dampers in shear-type systems based upon the mass proportional component of the Rayleigh damping matrix." Journal of Sound and Vibration 302, no. 3 (May 2007): 486–526. http://dx.doi.org/10.1016/j.jsv.2006.11.030.
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Kayabekir, Aylin Ece, Gebrail Bekdaş, Sinan Melih Nigdeli, and Zong Woo Geem. "Optimum Design of PID Controlled Active Tuned Mass Damper via Modified Harmony Search." Applied Sciences 10, no. 8 (April 24, 2020): 2976. http://dx.doi.org/10.3390/app10082976.
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In this study, the music-inspired Harmony Search (HS) algorithm is modified for the optimization of active tuned mass dampers (ATMDs). The modification of HS includes the consideration of the best solution with a defined probability and updating of algorithm parameters such as harmony memory, considering rate and pitch adjusting rate. The design variables include all the mechanical properties of ATMD, such as the mass, stiffness and damping coefficient, and the active controller parameters of the proposed proportional–integral–derivative (PID) type controllers. In the optimization process, the analysis of an ATMD implemented structure is done using the generated Matlab Simulink block diagram. The PID controllers were optimized for velocity feedback control, and the objective of the optimization is the minimization of the top story displacement by using the limitation of the stroke capacity of ATMD. The optimum results are presented for different cases of the stroke capacity limit of ATMD. According to the results, the method is effective in reducing the maximum displacement of the structure by 53.71%, while a passive TMD can only reduce it by 31.22%.
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Venanzi, Ilaria, and Filippo Ubertini. "Free Vibration Response of a Frame Structural Model Controlled by a Nonlinear Active Mass Driver System." Advances in Civil Engineering 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/745814.
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Active control devices, such as active mass dampers, are mainly employed for the reduction of wind-induced vibrations in high-rise buildings, with the final aim of satisfying vibration serviceability limit state requirements and of meeting appropriate comfort criteria. When such active devices, normally operating under wind loads associated with short return periods, are subjected to seismic events, they can experience large amplitude vibrations and exceed stroke limits. This may lead to a reduced performance of the control system that can even worsen the performance of the whole structure. In this paper, a nonlinear control strategy based on a modified direct velocity feedback algorithm is proposed for handling stroke limits of an active mass driver (AMD) system. In particular, a suitable nonlinear braking term proportional to the relative AMD velocity is included in the control law in order to slowdown the device in the proximity of the stroke limits. Experimental and numerical free vibration tests are carried out on a scaled-down five-story frame structure equipped with an AMD to demonstrate the effectiveness of the proposed control strategy.
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Hathout, J. P., and A. El-Shafei. "PI Control of HSFDs for Active Control of Rotor-Bearing Systems." Journal of Engineering for Gas Turbines and Power 119, no. 3 (July 1, 1997): 658–67. http://dx.doi.org/10.1115/1.2817035.
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This paper describes the proportional integral (PI) control of hybrid squeeze film dampers (HSFDS) for active control of rotor vibrations. Recently it was shown that the automatically controlled HSFD based on feedback of rotor speed can be a very efficient device for active control of rotor vibration when passing through critical speeds. Although considerable effort has been put into the study of steady-state vibration control, there are few methods in the literature applicable to transient vibration control of rotor-bearing systems. Rotating machinery may experience dangerously high dynamic loading due to the sudden mass unbalance that could be associated with blade loss. Transient run-up and coast down through critical speeds when starting up or shutting down rotating machinery induces excessive bearing loads at criticals. In this paper, PI control is proposed as a regulator for the HSFD system to attenuate transient vibration for both sudden unbalance and transient runup through critical speeds. A complete mathematical model of this closed-loop system is simulated on a digital computer. Results show an overall enhanced behavior for the closed-loop rotor system. Gain scheduling of both the integral gain and the reference input is incorporated into the closed-loop system with the PI regulator and results in an enhanced behavior of the controlled system.
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Konar, Tanmoy, and Aparna Dey Ghosh. "Adaptation of a Deep Liquid-Containing Tank into an Effective Structural Vibration Control Device by a Submerged Cylindrical Pendulum Appendage." International Journal of Structural Stability and Dynamics 21, no. 06 (March 17, 2021): 2150078. http://dx.doi.org/10.1142/s0219455421500784.
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Due to a high proportion of impulsive liquid mass and low inherent damping, liquid-containing deep tanks, such as conventional overhead water tanks, are generally not considered for design as tuned liquid dampers (TLDs) for passive vibration control of structures under lateral excitation. This paper presents a novel concept to convert deep tanks into effective vibration control systems through the incorporation of a submerged cylindrical pendulum appendage (CPA). The CPA is placed in the impulsive liquid zone of the tank and its oscillating frequency is tuned to the dominant frequency of the primary structure. When laterally excited, the primary structure transfers vibrational energy to the CPA, thereby setting it into oscillation. The motion of the CPA is opposed by the drag exerted by the surrounding liquid on it, which leads to dissipation of the vibrational energy. This particular design utilizes impulsive liquid mass in the energy dissipation mechanism, while allowing fluctuation in the liquid level in the upper region of the tank, thereby fulfilling the functional requirements of the tank. In this paper, the mathematical model and working principle of the deep tank with CPA (DT-CPA) damper are developed. The equations of motion of a two degree-of-freedom (2-DOF) structure-damper system are derived. The design of the DT-CPA damper is illustrated considering an example structure and the performance of the damper is examined by subjecting the structure-damper system to pre-recorded seismic base excitations. The sensitivity of the performance of the proposed damper to tuning ratio is further studied. Results indicate that the DT-CPA damper is effective in controlling structural vibrations and its performance is comparable to that of a conventional tuned mass damper (TMD) and even slightly superior to that of a conventional TLD system of the shallow tank configuration. The proposed concept thus holds potential for the utilization of deep tanks as energy dissipation devices with minimal interference to their usual functionality.
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Elmer, K. F., and C. R. Gentle. "A parsimonious model for the proportional control valve." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 215, no. 11 (November 1, 2001): 1357–63. http://dx.doi.org/10.1243/0954406011524739.
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A generic non-linear dynamic model of a direct-acting electrohydraulic proportional solenoid valve is presented. The valve consists of two subsystems—a spool assembly and one or two unidirectional proportional solenoids. These two subsystems are modelled separately. The solenoid is modelled as a non-linear resistor-inductor combination, with inductance parameters that change with current. An innovative modelling method has been used to represent these components. The spool assembly is modelled as a mass-spring-damper system. The inertia and the damping effects of the solenoid armature are incorporated in the spool model. The model accurately and reliably predicts both the dynamic and steady state responses of the valve to voltage inputs. Simulated results are presented, which agree well with experimental results.
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Gürgöze, M. "Application of Some Results on Proportionally Damped Systems to a Uniform N-mass Oscillator." International Journal of Mechanical Engineering Education 31, no. 1 (January 2003): 76–85. http://dx.doi.org/10.7227/ijmee.31.1.5.
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A study published some years ago [1] investigated how linear damping affected the eigenvalues of proportionally damped systems, and the results were presented graphically. The necessary conditions for the system to be overdamped or underdamped were given with the help of simple formulae. After a brief summary of the previous work, these methods are applied to a uniform oscillator. With the aid of this simple system, it has been observed that students can comprehend the various types of proportional damping better, and be able to visualize them more easily.
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Sitnikov, D. V., and A. A. Burian. "The active dynamic vibration damper in non-stationary operation of a vibroactive unit." Omsk Scientific Bulletin, no. 178 (2021): 13–17. http://dx.doi.org/10.25206/1813-8225-2021-178-13-17.
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The paper considers a vibration isolation system, in which a force is applied to the moving mass of the active dynamic vibration damper by an actuator in proportion to the measured value of the base response. The amplitude-frequency and impulse characteristics are plotted depending on the parameters of the system, assuming the actuator without distortion generates the force proportional to the base response. It is shown that the considered vibration isolation system is quite effective in the low-frequency region, including in the resonance region of the passive system, both in stationary and nonstationary modes of vibroactive forces
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Guclu, R., and A. Sertbas. "Evaluation of Sliding Mode and Proportional-Integral-Derivative Controlled Structures with an Active Mass Damper." Journal of Vibration and Control 11, no. 3 (March 2005): 397–406. http://dx.doi.org/10.1177/1077546305051202.
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In this paper, both a sliding mode controller (SMC) and proportional-integral-derivative (PID) controller are designed for a multi-degrees-of-freedom structure, which has an active mass damper (AMD) to suppress earthquakeor wind-induced vibration. Since the model might have uncertainties and/or parameter changes, a SMC has been included because of its robust character and performance. The structural system has five degrees of freedom and has been simulated against an initial displacement of the first floor. At the end of the paper, we present the time histories of the first floor, top floor, and AMD displacements, the control voltage and frequency response of the uncontrolled, PID controlled, and sliding mode controlled structures, and we discuss the results.
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Vaughan, N. D., and J. B. Gamble. "The Modeling and Simulation of a Proportional Solenoid Valve." Journal of Dynamic Systems, Measurement, and Control 118, no. 1 (March 1, 1996): 120–25. http://dx.doi.org/10.1115/1.2801131.
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A nonlinear dynamic model of a high speed direct acting solenoid valve is presented. The valve consists of two subsystems; a proportional solenoid and a spool assembly. These two subsystems are modeled separately. The solenoid is modeled as a nonlinear resistor/inductor combination, with inductance parameters that change with displacement and current. Empirical curve fitting techniques are used to model the magnetic characteristics of the solenoid, enabling both current and magnetic flux to be simulated. The spool assembly is modeled as a spring/mass/damper system. The inertia and damping effects of the armature are incorporated in the spool model. The solenoid model is used to estimate the spool force in order to obtain a suitable damping coefficient value. The model accurately predicts both the dynamic and steady-state response of the valve to voltage inputs. Simulated voltage, current, and displacement results are presented, which agree well with experimental results.
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Kurniawan, Edi. "Analysis and Simulation of Proportional Derivative and Proportional Integral Derivative Control Systems Using Xcos Scilab." Journal of Technomaterials Physics 3, no. 1 (February 26, 2021): 36–44. http://dx.doi.org/10.32734/jotp.v3i1.5544.
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PID (Proportional Integral Derivative) control is a popular control in the industry and aims to improve the performance of a system. This control has controlling parameters, namely Kp, Ki, and Kd which will have a control effect on the overall system response. In this research, P, PD, and PID control simulations with the transfer function of the mass-damper spring as a plant using Xcos Scilab. The method used is the trial and error method by setting and varying the values of the control constants Kp, Ki, and Kd to produce the desired system response. The value adjustment of system control parameters is carried out with several variations, namely Kp control variation, Kp variation to constant Kd, Kd variation to constant Kp, Kp variation to Ki, constant Kd, variation of Ki to Kp, constant Kd and variation of Kd to Kp, Ki constant. The second method is automatic tuning which is done through mathematical calculations to obtain PID control constants, namely Zieglar Nichols PID tuning with the oscillation method. From the system simulation results, the best parameter is obtained through the Zieglar Nichols PID tuning process based on the results of the transient response analysis, namely when the proportional gain value (Kp) is 50. The system performance characteristics produced in the tuning process are 3.994 seconds of settling time at 2.36 seconds research time. resulting in a maximum overshoot value of 3.6% and a peaktime value of 3.994 seconds
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Badr, Munaf Fathi, Ekhlas Hameed Karam, and Noor Mohammaed Mjeed. "Control design of damper mass spring system based on backstepping controller scheme." International Review of Applied Sciences and Engineering 11, no. 2 (August 2020): 181–87. http://dx.doi.org/10.1556/1848.2020.20049.
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AbstractThe objective of this paper is to present a proposed control model for the electromechanical damper mass spring system including the backstepping technique in comparison with the conventional proportional–derivative–integral (PID) controller unit to realize the best performance of the control systems. The suggested approach demanded the construction in laboratory arrangement of damper mass spring system which linked with electrical position sensor, and the theoretical work involved the derivation of the required mathematical equations in order to formulate the simulation models in Matlab software package. The obtained results show that the backstepping control technique provides the better performance associated with stable control system especially with increasing the value of selected mechanical load.
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Qin, Jin Qi. "Seismic Response Analysis on Non-Proportional Damped System by Using Perturbation Technique." Advanced Materials Research 639-640 (January 2013): 917–21. http://dx.doi.org/10.4028/www.scientific.net/amr.639-640.917.
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A simple method for seismic response analysis on multi-degree-of-freedom (MDOF) system with non-proportional damping is proposed. Based on the real modal theory, transforming the system from physical coordinates to modal coordinates, the damping matrix is a relatively small amount compared with the mass matrix and the stiffness matrix, so the damping matrix may be denoted as a small amount. The approximate analytical solution of the non-proportional damped system can be obtained by using the perturbation technique which can be used as a reference of seismic response analysis of complicated structures.
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Chen, Zhao, Kikuchi Junya, Ikenaga Masahiro, Ikago Kohju, and Inoue Norio. "Viscoelastically Supported Viscous Mass Damper Incorporated into a Seismic Isolation System." Journal of Earthquake and Tsunami 10, no. 03 (September 2016): 1640009. http://dx.doi.org/10.1142/s1793431116400091.
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This work discusses the application of a two-node apparent mass device, designated as an inerter, which generates inertial resistance forces proportional to relative accelerations between its two nodes, to seismic isolated civil structures. This study employs a viscous mass damper (VMD) consisting of an inerter and a viscous element in parallel arrangement. Although the use of a VMD is effective in reducing relative responses, previous studies have experienced excessive floor response accelerations because the inerter directly transmits ground accelerations to the superstructure. This work examines the acceleration reduction effect of a viscoelastic element arranged in series to the VMD for filtering out the higher frequency components of the ground motion accelerations.
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An, Feng-chen, Qiong-guan Xiao, Shuai Li, and Hong-jun Li. "Mesoscale Modelling of Bond Behavior at FRP-Concrete under Mode II Loading: Effect of Rayleigh Damping." International Journal of Polymer Science 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6053181.
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The paper mainly focuses on the study of the effects of Rayleigh damping in the simulations of FRP-concrete bonded joints, thereby proposing an approach to determine the value of its appropriate Rayleigh damping. Specifically, the element tests under Mode I and Mode II fracture modes were first carried out to investigate the effects of the mass proportional Rayleigh damping and the stiffness proportional Rayleigh damping. An FRP-concrete bonded joint is then employed to further investigate the effects of Rayleigh damping on the simulation results under Mode II fracture mode. It is shown that low-frequency vibrations are produced in the simulations of the specimens loaded by Mode I loading and could be damped by the mass proportional Rayleigh damping, while high-frequency vibrations are produced in the simulations of the specimens loaded by Mode II loading and could only be damped by the stiffness proportional Rayleigh damping. It also shows that the stiffness proportional damping is essential to damp out the oscillations in such simulations, thereby improving the convergence. In addition, the procedure proposed in this paper can lead to a proper interval for the value of the stiffness proportional Rayleigh damping, beyond which an unreasonable simulation result may be obtained.
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Sullivan, Timothy J. "Direct Displacement-Based Design of a RC wall-steel EBF dual system with added dampers." Bulletin of the New Zealand Society for Earthquake Engineering 42, no. 3 (September 30, 2009): 167–78. http://dx.doi.org/10.5459/bnzsee.42.3.167-178.
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An innovative application of Direct Displacement-Based Design (DBD) is presented for a modern 8-storey dual system structure consisting of interior concrete walls in parallel to a number of large steel eccentrically braced frames, fitted with visco-elastic dampers at link positions. The innovative DBD methodology lets the designer directly control the forces in the structure by choosing strength proportions at the start of the design procedure. The strength proportions are used to establish the displaced shape at peak response and thereby establish the equivalent single-degree-of-freedom system design displacement, mass and effective height. A new simplified formulation for the equivalent viscous damping of systems possessing viscous dampers is proposed which also utilises the strength proportions chosen by the designer at the start of the process. The DBD approach developed is relatively quick to use, enabling the seismic design of the 8-storey case study structure to be undertaken without the development of a computer model. To verify the ability of the design method, non-linear time-history analyses are undertaken using a suite of spectrum-compatible accelerograms. These analyses demonstrate that the design solution successfully achieves the design objectives to limit building deformations, and therefore damage.
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Sullivan, Timothy J. "Direct Displacement-Based Design of a RC wall-steel EBF dual system with added dampers." Bulletin of the New Zealand Society for Earthquake Engineering 44, no. 3 (September 30, 2011): 167–78. http://dx.doi.org/10.5459/bnzsee.44.3.167-178.
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An innovative application of Direct Displacement-Based Design (DBD) is presented for a modern 8-storey dual system structure consisting of interior concrete walls in parallel to a number of large steel eccentrically braced frames, fitted with visco-elastic dampers at link positions. The innovative DBD methodology lets the designer directly control the forces in the structure by choosing strength proportions at the start of the design procedure. The strength proportions are used to establish the displaced shape at peak response and thereby establish the equivalent single-degree-of-freedom system design displacement, mass and effective height. A new simplified formulation for the equivalent viscous damping of systems possessing viscous dampers is proposed which also utilises the strength proportions chosen by the designer at the start of the process. The DBD approach developed is relatively quick to use, enabling the seismic design of the 8-storey case study structure to be undertaken without the development of a computer model. To verify the ability of the design method, non-linear time-history analyses are undertaken using a suite of spectrum-compatible accelerograms. These analyses demonstrate that the design solution successfully achieves the design objectives to limit building deformations, and therefore damage.
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Minas, C., and D. J. Inman. "Matching Finite Element Models to Modal Data." Journal of Vibration and Acoustics 112, no. 1 (January 1, 1990): 84–92. http://dx.doi.org/10.1115/1.2930103.
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A technique is proposed which systematically adjusts a finite element model of a structure to produce an updated model in agreement with measured modal results. The approach suggested here is to consider the desired perturbations in stiffness and damping matrices as gain matrices in a feedback control algorithm designed to perform eigenstructure assignment. The improved stiffness and damping matrices combined with the analytical mass matrix, more closely predict the modal test results. The technique is applicable to undamped, proportionally damped, as well as non-proportionally damped models. The proposed method assumes that the analytical mass, damping and stiffness matrices are known and that vibration test data is available in the form of natural frequencies, damping ratios, and mode shapes.
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Karnopp, D. "Analytical Results for Optimum Actively Damped Suspensions Under Random Excitation." Journal of Vibration and Acoustics 111, no. 3 (July 1, 1989): 278–82. http://dx.doi.org/10.1115/1.3269853.
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A single degree-of-freedom system under white noise base velocity excitation is optimized using analytical expressions for mean square response quantities. In addition to a parallel spring and passive damper combination, a force generator is assumed to provide an active damping force proportional to the isolated mass absolute velocity. Several optimal and sub-optimal boundary curves are found and the corresponding optimal parameters are also presented. The results show trends which may be useful in designing variable parameter and semiactive vehicle suspensions.
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Djedoui, Nassim, Abdelhafid Ounis, and Mahdi Abdeddaim. "Active Vibration Control for Base-Isolated Structures Using a PID Controller against Earthquakes." International Journal of Engineering Research in Africa 26 (October 2016): 99–110. http://dx.doi.org/10.4028/www.scientific.net/jera.26.99.
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In this paper, a closed loop control approach for controlling the vibration of buildings under earthquake excitations is introduced. An active hybrid control combining base isolation and active tuned mass damper (AMD) installed on the lowest floor of a base-isolated frame building is investigated. The Active control force is controlled by the mean of a proportional–integral–derivative (PID) controller, incorporated with a negative feedback error closed loop. The difference between the base displacement and equilibrium position of the structure is used to evaluate the error and feed the PID controller. A simulation is carried out on a six degrees of freedom base-isolated frame structure using MATLAB. The performances of the proposed active hybrid control system are tested under El Centro, Northridge, and Loma Pietra earthquakes.Compared results with base-isolated structure and base-isolated structure equipped with a passive and active tuned mass damper (TMD)/ (ATMD) showed that the active hybrid control system is more efficient. A reduction of 70% in base displacement, velocity and 15% in base acceleration is obtained.
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Bang, Sookyuk, and Soyoung Ahn. "Analysis and Control of Heterogeneous Connected and Autonomous Vehicles using a Spring-Mass-Damper System." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 8 (June 20, 2020): 309–18. http://dx.doi.org/10.1177/0361198120927696.
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This study analyzes the behavior of heterogeneous connected and autonomous vehicles (CAVs) and proposes the best vehicle sequence for optimal platoon throughput and platoon formation. A spring-mass-damper (SMD) system is adopted for control of CAVs, and the control parameters are formulated in relation to the physical capabilities of vehicles. To gain insight, we consider three types of vehicle: passenger cars, mini-vans, and heavy-duty vehicles. For each type, we investigate the maximum platoon throughput and the clustering time, defined as the time to reach the target equilibrium state. We further investigate different sequences of vehicle types in a platoon to identify the optimal vehicle order that maximizes the throughput and minimizes clustering time. Findings suggest that the highest performance vehicle (in relation to acceleration capability) should be placed as the leader of a platoon and that the number of passenger cars behind heavy vehicles (e.g., semi-trailers) should be minimized in the platoon. In addition, we examine how the proportions of lower performance vehicles affect throughput and clustering times. The result suggests that the higher the proportions, the lower the throughput and the longer the clustering time. The lowest performance vehicle had the greatest effect.
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Aguilar-Ibáñez, Carlos Fernando, Oscar Octavio Gutiérrez-Frías, Juan Carlos Martínez-García, Rubén Garrido-Moctezuma, and Bernardo Gómez-González. "Lyapunov-Based PD Linear Control of the Oscillatory Behavior of a Nonlinear Mechanical System: The Inverted Physical Pendulum with Moving Mass Case." Mathematical Problems in Engineering 2010 (2010): 1–12. http://dx.doi.org/10.1155/2010/162875.
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This paper concerns active vibration damping of a frictionless physical inverted pendulum with a radially moving mass. The motion of the inverted pendulum is restricted to an admissible set. The proposed Proportional Derivative linear controller damps the inverted pendulum (which is anchored by a torsion spring to keep it in a stable upright position), exerting a force on the radially moving mass. The controller design procedure, which follows a traditional Lyapunov-based approach, tailors the energy behavior of the system described in Euler-Lagrange terms.
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Yanabe, S., S. Kaneko, Y. Kanemitsu, N. Tomi, and K. Sugiyama. "Rotor Vibration Due to Collision With Annular Guard During Passage Through Critical Speed." Journal of Vibration and Acoustics 120, no. 2 (April 1, 1998): 544–50. http://dx.doi.org/10.1115/1.2893863.
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This paper deals with a nonstationary vibration of a rotor due to its collision with a guard during passage through a critical speed. An unbalanced rigid rotor supported by springs and dampers is accelerated at a constant angular acceleration and collides with an annular guard supported by springs and dampers. This dynamic process is calculated by the Runge-Kutta method, and effects of system-parameters on the process are discussed. The collision phenomenon is analyzed through two different theories. In the collision theory, the law of conservation of momentum and the coefficient of restitution are used in order to obtain rotor and guard velocities after collision. The impulse of the force induced by collision is assumed to be equal to the momentum change before and after collision. In the contact force theory, the contact force is assumed to be proportional to the overlapped displacement of the two bodies. Few differences are observed between the calculated responses based on the two theories. In some cases, the rotor executes a diverging backward whirl due to the friction force that occurs during collision with the guard and can not pass through the critical speed. The criteria maps for nonoccurrence of the backward whirl are shown.
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Soong, M. F., Rahizar Ramli, and Wan Nor Liza Wan Mahadi. "Ride Evaluation of Vehicle Suspension Employing Non-Linear Inerter." Applied Mechanics and Materials 471 (December 2013): 9–13. http://dx.doi.org/10.4028/www.scientific.net/amm.471.9.
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Inerter is a recent element in suspension systems with the property that the generated force is proportional to the relative acceleration between its two terminals, which is similar to the way a spring reacts to relative displacement and a damper to relative velocity. This paper presents the analysis of a non-linear inerter working in parallel to passive spring and damper of a vehicle suspension to evaluate its effect on vehicles ride. The non-linear inerter was theoretically capable of switching between on and off states depending on whether or not the suspension deflection was beyond a specified free play. In the study, this behavior was represented mathematically as control law which depended on the relative displacement between the sprung and unsprung masses. A mathematical quarter vehicle model incorporating the non-linear inerter was simulated in MATLAB/Simulink to determine the vehicle responses due to road input in the form of step profile for different combinations of free play and inerters on-state proportionality constant called the inertance. Results showed improvements in vehicle ride comfort, as demonstrated by the lower root-mean-squared sprung mass accelerations compared to the ordinary passive suspension with only spring and damper. Additionally, implementation of non-linear inerter gave lower percentage overshoot to step input, indicating better transient response than ordinary passive suspension.
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Abdullah, Bahaa-Aldin R., Mohsin N. . Hamzah, and Ammar S. Merza. "E CONTROL AND EXPERIMENTAL EVALUATION ON A QUARTER-CAR TEST RIG." IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING 20, no. 2 (June 28, 2020): 143–52. http://dx.doi.org/10.32852/iqjfmme.v20i2.494.
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In this paper a quarter-vehicle full-scale suspension test rig was designed and manufactured,the suspension is considered semi-active as the electrohydraulic (EH) damper used is fullycontrolled. This gives an indoor-based simulation tool which is important for vehicle testing;.This reduces the cost significantly with accurate results, especially when designing a newsuspension system. The aim of the current work was to build a new quarter-vehicle test rigwith expandable capabilities for diverse design objectives, also may be used for academicpurposes. The control objective was achieved by using dynamic characteristics of theelectrohydraulic (EH) damper to suppress the oscillation of the sprung mass due to roadirregularities. The test rig was constructed using a Genesis G80 (2016) suspension system.Finally, the simulation results demonstrated that the proposed controller used be able toefficiently regulate the chassis vertical oscillation under these irregularities. The experimentalresults for the quarter-car model showed good results between experimental and simulatedresults, where the proportion of conformity about 95%
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Abdullah, Bahaa-Aldin R., Mohsin N. . Hamzah, and Ammar S. . Merza. "E CONTROL AND EXPERIMENTAL EVALUATION ON A QUARTER-CAR TEST RIG." IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING 20, no. 2 (June 28, 2020): 143–52. http://dx.doi.org/10.32852/iqjfmme.v20i2.495.
Full textAbstract:
In this paper a quarter-vehicle full-scale suspension test rig was designed and manufactured,the suspension is considered semi-active as the electrohydraulic (EH) damper used is fullycontrolled. This gives an indoor-based simulation tool which is important for vehicle testing;.This reduces the cost significantly with accurate results, especially when designing a newsuspension system. The aim of the current work was to build a new quarter-vehicle test rigwith expandable capabilities for diverse design objectives, also may be used for academicpurposes. The control objective was achieved by using dynamic characteristics of theelectrohydraulic (EH) damper to suppress the oscillation of the sprung mass due to roadirregularities. The test rig was constructed using a Genesis G80 (2016) suspension system.Finally, the simulation results demonstrated that the proposed controller used be able toefficiently regulate the chassis vertical oscillation under these irregularities. The experimentalresults for the quarter-car model showed good results between experimental and simulatedresults, where the proportion of conformity about 95%.
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Jain, Saransh, Shubham Saboo, Catalin Iulian Pruncu, and Deepak Rajendra Unune. "Performance Investigation of Integrated Model of Quarter Car Semi-Active Seat Suspension with Human Model." Applied Sciences 10, no. 9 (May 2, 2020): 3185. http://dx.doi.org/10.3390/app10093185.
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In this paper, an integrated model of a semi-active seat suspension with a human model over a quarter is presented. The proposed eight-degrees of freedom (8-DOF) integrated model consists of 2-DOF for the quarter car model, 2-DOF for the semi-active seat suspension and 4-DOF for the human model. A magneto-rheological (MR) damper is implemented for the seat suspension. The fuzzy logic-based self-tuning (FLST) proportional–integral–derivative (PID) controller allows to regulate the controlled force on the basis of sprung mass velocity error and its derivative as input. The controlled force is tracked by the Heaviside step function which determines the supply voltage for the MR damper. The performance of the proposed integrated model is analysed, in-terms of human head accelerations, for several road profiles and at different speeds. The performance of the semi-active seat suspension is compared with the traditional passive seat suspension to validate the effectiveness of the proposed integrated model with a semi-active seat suspension. The simulation results show that the semi-active seat suspension improves the ride comfort significantly by reducing the head acceleration effectively compared to the passive seat suspension.
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Kaouk, Mohamed, David C. Zimmerman, and Todd W. Simmermacher. "Assessment of Damage Affecting All Structural Properties Using Experimental Modal Parameters." Journal of Vibration and Acoustics 122, no. 4 (May 1, 2000): 456–63. http://dx.doi.org/10.1115/1.1310328.
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Recently, the authors proposed computationally attractive algorithms to determine the location and extent of structural damage for undamped and damped structures assuming damage results in a localized change in a subset (not full set) of the property matrices (mass, stiffness and damping matrices). The algorithms make use of a finite element model and a subset of measured eigenvalues and eigenvectors. The developed theories approach the damage location and extent problem in a decoupled fashion. First, a theory is developed to determine the location of structural damage. With location determined, a damage extent theory is then developed. The damage extent algorithm is a minimum rank perturbation, which is consistent with the effects of many classes of structural damage on a finite element model. In this work, the concept of the Minimum Rank Perturbation Theory (MRPT) is adopted to simultaneously determine the damage extent of all property matrices of undamped and proportionally damped structures. Note that the property matrices are the mass, stiffness and damping matrices. Illustrative examples are presented to show the performance of the proposed theory. [S0739-3717(00)01904-8]
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Yan, Yao, and Jian Xu. "Stability Analysis of a Transverse Cylindrical Grinding Process." Advanced Materials Research 479-481 (February 2012): 1190–93. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.1190.
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The stability of a transverse cylindrical grinding process is investigated in this paper. The workpiece is considered as a rotating damped hinged-hinged Euler-Bernoulli beam and the grinding wheel a rotating damped spring mass system moving along the workpiece. Called regenerative force, the contact force between the workpiece and the wheel is a functional equation related to both the current and previous relative positions between the workpiece and the wheel since the regeneration exists on the surfaces of both the workpiece and the wheel. The two distinct time delays presented in the regenerative force model are inversely proportional to the rotation speeds of the workpiece and the wheel respectively. For grinding stability analysis, the regenerative effects are considered as the key factors in inducing chatter vibrations in the grinding process. The grinding stability is numerically analyzed since two distinct delays being involved in the model makes the analytical analysis extremely difficult. Finally, the grinding stability analysis is verified by numerical simulation.
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Chen, Chieh-Li, Her-Terng Yau, and Yunhua Li. "Subharmonic and Chaotic Motions of a Hybrid Squeeze-Film Damper-Mounted Rigid Rotor With Active Control." Journal of Vibration and Acoustics 124, no. 2 (March 26, 2002): 198–208. http://dx.doi.org/10.1115/1.1448318.
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The hybrid squeeze-film damper bearing with active control is proposed in this paper. The pressure distribution and the dynamics of a rigid rotor supported by such bearing are studied. A PD (proportional-plus-derivative) controller is used to stabilize the rotor-bearing system. Numerical results show that, due to the nonlinear factors of oil film force, the trajectory of the rotor demonstrates a complex dynamics with rotational speed ratio s. Poincare´ maps, bifurcation diagrams, and power spectra are used to analyze the behavior of the rotor trajectory in the horizontal and vertical directions under different operating conditions. The maximum Lyapunov exponent and fractal dimension concepts are used to determine if the system is in a state of chaotic motion. Numerical results show that the maximum Lyapunov exponent of this system is positive and the dimension of the rotor trajectory is fractal at the nondimensional speed ratio s=3.0, which indicate that the rotor trajectory is chaotic under such operation condition. In order to avoid the nonsynchronous chaotic vibrations, an increased proportional gain is applied to control this system. It is shown that the rotor trajectory will leave chaotic motion to periodic motion in the steady state under control action.
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Weber, Felix, Peter Huber, Fredrik Borchsenius, and Christian Braun. "Performance of TMDI for Tall Building Damping." Actuators 9, no. 4 (December 15, 2020): 139. http://dx.doi.org/10.3390/act9040139.
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This study investigates the vibration reduction of tall wind-excited buildings using a tuned mass damper (TMD) with an inerter (TMDI). The performance of the TMDI is computed as a function of the floor to which the inerter is grounded as this parameter strongly influences the vibration reduction of the building and for the case when the inerter is grounded to the earth whereby the absolute acceleration of the corresponding inerter terminal is zero. Simulations are made for broadband and harmonic excitations of the first three bending modes, and the conventional TMD is used as a benchmark. It is found that the inerter performs best when grounded to the earth because, then, the inerter force is in proportion to the absolute acceleration of only the pendulum mass, but not to the relative acceleration of the two inerter terminals, which is demonstrated by the mass matrix. However, if the inerter is grounded to a floor below the pendulum mass, the TMDI only outperforms the TMD if the inerter is grounded to a floor within approximately the first third of the building’s height. For the most realistic case, where the inerter is grounded to a floor in the vicinity of the pendulum mass, the TMDI performs far worse than the classical TMD.
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Rasa, Ahmad Yamin, and Mehmet Hamit Özyazıcıoğlu. "Determination of the exact mode frequencies of multi-storey structures by state-space method and a comparison with mode superposition method." Challenge Journal of Structural Mechanics 7, no. 1 (March 12, 2021): 1. http://dx.doi.org/10.20528/cjsmec.2021.01.001.
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A comparative research has been carried out for obtaining the time-consuming exact solution (state-space) and approximate solution (mode superposition) of transient and steady-state vibrations of linearly damped linear frame buildings. In the mode superposition method, the proportional damping matrix has been constructed by different approaches such as modal combination of mass and stiffness matrixes (Rayleigh) and disregarding the off-diagonal elements of the non-classical damping matrix, while in the state-space method the non-proportional damping matrix is constructed in exact situation. These observations are individually investigated, which the most suitable parameter to render the approximate results as close as possible to the exact results. Harmonic forces are applied on the different storeys of three and five storey frame buildings, and the responses are displayed in comparative tables and figures. The maximum responses are calculated by square root of sum of the squares (SRSS) method. A MATLAB code is generated and the equations of exact and approximate methods are solved.
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Etedali, Sadegh, and Saeed Tavakoli. "PD/PID Controller Design for Seismic Control of High-Rise Buildings Using Multi-Objective Optimization: A Comparative Study with LQR Controller." Journal of Earthquake and Tsunami 11, no. 03 (August 14, 2017): 1750009. http://dx.doi.org/10.1142/s1793431117500099.
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This paper developed multi-objective optimization design of proportional–derivative (PD) and proportional–integral–derivative (PID) controllers for seismic control of high-rise buildings. The case study is an 11-story realistic building equipped with active tuned mass damper (ATMD). Four earthquakes and nine performance indices are taken into account to assess the performance of the controllers. To create a good trade-off between the performance and robustness of the closed-loop structural system, a non-dominated sorting genetic algorithm, NSGA-II, is employed. To evaluate the degree of robustness of the controllers, four structural models with uncertainties in the nominal model of the structure is considered. For comparison purposes, a linear quadratic regulator (LQR) controller is also designed in the numerical simulations. Simulation results show that the proposed PD and PID controllers significantly perform better than the LQR in reduction of structural responses. Also, it is shown that the LQR does not provide a good performance in strong earthquakes. However, PD and PID controllers are able to significantly reduce structural responses. Moreover, it is shown that the PID has a better performance than the PD. The results also show that the proposed controllers are capable of maintaining a desired performance in the presence of modeling errors. They also have several advantages over modern controllers in terms of simplicity and reduction of required sensors and computational resources in tall buildings.
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Iipponen, Juho, and Leo Donner. "Simple Analytic Solutions for a Convectively Driven Walker Circulation and Their Relevance to Observations." Journal of the Atmospheric Sciences 78, no. 1 (January 2021): 299–311. http://dx.doi.org/10.1175/jas-d-20-0014.1.
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AbstractWe present a linear equation for the Walker circulation streamfunction and find its analytic solutions given specified convective heating. In a linear Boussinesq fluid with Rayleigh damping and Newtonian cooling, the streamfunction obeys a Poisson’s equation, forced by gradients in the meridionally averaged diabatic heating and Coriolis force. For an idealized convective heating distribution, analytic solutions for the streamfunction can be found through an analogy with electrostatics. We use these solutions to study the response of the Walker circulation strength (mass transport) to changes in the vertical and zonal scales of convective heating. Robust responses are obtained that depend on how the total convective heating of the atmosphere responds to changing scale. If the total heating remains unchanged, increasing the zonal scale or the vertical scale always leads to a weaker circulation. Conversely, if the total heating grows in proportion to the spatial scale, the circulation becomes stronger with increasing scale. These conclusions are shown to be consistent with a three-dimensional numerical model. Moreover, they are useful in describing the observed seasonal and interannual (ENSO) variability of the Indo-Pacific Walker circulation. On both time scales, the overturning becomes weaker with increasing zonal scale of the convective region, reminiscent of our solutions where we do not vary the total convective heating. Reanalysis data also indicate that the zonal circulation is quite strongly damped, thus yielding a result that the circulation strength is directly proportional to the warm-pool spatial-mean precipitation.
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Mamat, Normaisharah, Fitri Yakub, Sheikh Ahmad Zaki Shaikh Salim, and Mohamed Sukri Mat Ali. "Performance Comparison of Controllers for Suppressing the Structural Building Vibration." Indonesian Journal of Electrical Engineering and Computer Science 10, no. 2 (May 1, 2018): 537. http://dx.doi.org/10.11591/ijeecs.v10.i2.pp537-544.
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<span lang="EN-US">This paper presents the modelling and simulation of controllers for controlling the position of two degree of freedom (2 DOF) mass spring damper system. Proportional integral (PI), fuzzy logic controller (FLC) and sliding mode controller (SMC) are design to minimize the vibration of the system that represent as building structure towards earthquake. A structural building is simulate based on real earthquake occur in El Centro on May 1940. The algorithm for building structure, actuator and controller is derived. Matlab/Simulink is used to analyze the performance of controllers towards the vibration building structure. At the end of the study the time response for two story building for uncontrolled and controlled system is present. Besides, the result for limitation voltage for each controller is also analyse to determine the maximum voltage consume for the system. The simulation results show the comparison of the controllers’ performance in suppressing the building vibration. From performance analysis, SMC provides better performance compared to PI and FLC based on structural vibration reduction.</span>
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Starek, L., and D. J. Inman. "A Symmetric Inverse Vibration Problem for Nonproportional Underdamped Systems." Journal of Applied Mechanics 64, no. 3 (September 1, 1997): 601–5. http://dx.doi.org/10.1115/1.2788935.
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This paper considers a symmetric inverse vibration problem for linear vibrating systems described by a vector differential equation with constant coefficient matrices and nonproportional damping. The inverse problem of interest here is that of determining real symmetric, coefficient matrices assumed to represent the mass normalized velocity and position coefficient matrices, given a set of specified complex eigenvalues and eigenvectors. The approach presented here gives an alternative solution to a symmetric inverse vibration problem presented by Starek and Inman (1992) and extends these results to include noncommuting (or commuting) coefficient matrices which preserve eigenvalues, eigenvectors, and definiteness. Furthermore, if the eigenvalues are all complex conjugate pairs (underdamped case) with negative real parts, the inverse procedure described here results in symmetric positive definite coefficient matrices. The new results give conditions which allow the construction of mass normalized damping and stiffness matrices based on given eigenvalues and eigenvectors for the case that each mode of the system is underdamped. The result provides an algorithm for determining a nonproportional (or proportional) damped system which will have symmetric coefficient matrices and the specified spectral and modal data.
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Olgac, N., and M. Hosek. "Active Vibration Absorption Using Delayed Resonator With Relative Position Measurement." Journal of Vibration and Acoustics 119, no. 1 (January 1, 1997): 131–36. http://dx.doi.org/10.1115/1.2889680.
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A novel active vibration absorption technique, the Delayed Resonator, has been introduced recently as a unique way of suppressing undesired oscillations. It suggests a control force on a mass-spring-damper absorber in the form of a proportional position feedback with a time delay. Its strengths consist of extremely simple implementation of the control algorithm, total vibration suppression of the primary structure against a harmonic force excitation and full effectiveness of the absorber in a semi-infinite range of disturbance frequency, achieved by real-time tuning. All this development work was done using the absolute displacements of the absorber in the feedback. These measurements, however, may be difficult to obtain and for some applications impossible. This paper deals with the operating and design repercussions caused by the substituting of an easier measurement: the relative motion of the absorber with respect to the primary structure. Although the proposition sounds like a trivial extension to the prior work it gives rise to important concerns such as system stability. Theoretical foundations for the Delayed Resonator (DR) are briefly recapitulated and its implementation on a single-degree-of-freedom primary structure disturbed by a harmonic force is discussed utilizing both absolute and relative position measurement of absorber mass. Methods for stability range analysis and transient behavior are presented as design tools. Properties observed for the same system with these two different feedbacks are compared. Another important advantage of the relative position feature is is to decouple the operation of the absorber from the primary structure entirely.
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Abbasi, Saad, Karam Kallu, and Min Lee. "Efficient Control of a Non-Linear System Using a Modified Sliding Mode Control." Applied Sciences 9, no. 7 (March 27, 2019): 1284. http://dx.doi.org/10.3390/app9071284.
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Trajectory tracking is an essential requirement in robot manipulator movement and localization applications. It is a current research topic of interest, and several researchers have proposed different schemes to achieve the task accurately. This research proposes efficient control of a hydraulic non-linear robot manipulator using a modified sliding mode control, named proportional derivative sliding mode control with sliding perturbation observer (PDSMCSPO), to overcome parameter uncertainties and non-linearity. The proposed new control strategy achieves higher accuracy and better time convergence than the previous one. A positive derivative gain, which has a value less than one, is multiplied with the velocity error term of the sliding surface. The proposed control (PDSMCSPO) also achieves robustness. Results show that by introducing the derivative gain, the chattering from the system has been reduced more than classical sliding mode control (SMC). The reason is that during reaching phase this small gain multiplies with the perturbation and minimizes the effect of perturbation on the system. A smaller value of switching gain K is required as compared to SMC, and the transfer function between sliding surface and perturbation in proportional derivative sliding mode control (PDSMC)has low pass filter characteristics. The proposed PDSMCSPO has a faster response than previous sliding mode control with sliding perturbation observer (SMCSPO), and the output and sliding surface convergence to the desired value is much quicker than conventional logic. Some other characteristics such as error in the output are small because of more attenuation of the perturbation signal. Simulation and experimental results are presented for a link between the hydraulic robot manipulator and the mass damper system.
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Zhang, Xiayang, Haoquan Liang, and Meijuan Zhao. "Fundamental solution and its validation by numerical inverse Laplace transformation and FEM for a damped Timoshenko beam subjected to impact and moving loads." Journal of Vibration and Control 25, no. 3 (August 12, 2018): 593–611. http://dx.doi.org/10.1177/1077546318790867.
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This paper, taking the clamped boundary condition as an example, develops Su and Ma's fundamental solutions of the dynamic responses of a Timoshenko beam subjected to impact load. Based on that, a further extension regarding the general moving load case is also established. Kelvin–Voigt damping, whether proportionally or nonproportionally damped, is incorporated into the model, making it more comprehensive than the model of Su and Ma. Numerical inverse Laplace transformation is introduced to obtain the time-domain solution, where Durbin's formula and the corresponding convergence criteria are utilized in numerical experiments. Further, the real modal superposition method is applied at an analytical level to validate the numerical results by applying a proportionally damped condition. Total comparisons are made between the methods by sufficient case studies. The dynamic responses with and without damping effect are computed with wider slenderness to verify the correctness and effectiveness of the numerical results. Furthermore, parametric studies regarding the damping coefficients are performed to explore the nonproportional damping effect. The results show that the structural damping has significant influences on the dynamic behaviors and is especially stronger at small slender ratios. As the damping decreases the inherent frequencies and excites the low-frequency modal components more actively, a resonant phenomenon appears in high slenderness case when the beam experiences a low-speed moving load. Additionally, the computations in the moving load case indicate that the algorithm convergence is preferable when the number of grids exceeds 1000.
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Andrianov, Alexander A., Artem Starodubtsev, and Yasser Elmahalawy. "Quantum Analysis of BTZ Black Hole Formation Due to the Collapse of a Dust Shell." Universe 6, no. 11 (October 30, 2020): 201. http://dx.doi.org/10.3390/universe6110201.
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We perform Hamiltonian reduction of a model in which 2 + 1 dimensional gravity with negative cosmological constant is coupled to a cylindrically symmetric dust shell. The resulting action contains only a finite number of degrees of freedom. The phase space consists of two copies of ADS2—both coordinate and momentum space are curved. Different regions in the Penrose diagram can be identified with different patches of ADS2 momentum space. Quantization in the momentum representation becomes particularly simple in the vicinity of the horizon, where one can neglect momentum non-commutativity. In this region, we calculate the spectrum of the shell radius. This spectrum turns out to be continuous outside the horizon and becomes discrete inside the horizon with eigenvalue spacing proportional to the square root of the black hole mass. We also calculate numerically quantum transition amplitudes between different regions of the Penrose diagram in the vicinity of the horizon. This calculation shows a possibility of quantum tunneling of the shell into classically forbidden regions of the Penrose diagram, although with an exponentially damped rate away from the horizon.
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Theuns, Tom. "Connecting cosmological accretion to strong Ly α absorbers." Monthly Notices of the Royal Astronomical Society 500, no. 2 (November 5, 2020): 2741–56. http://dx.doi.org/10.1093/mnras/staa3412.
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ABSTRACT We present an analytical model for the cosmological accretion of gas on to dark matter haloes, based on a similarity solution applicable to spherical systems. Performing simplified radiative transfer, we compute how the accreting gas turns increasingly neutral as it self-shields from the ionizing background, and obtain the column density, $N_{\rm H\,{\small I}}$, as a function of impact parameter. The resulting column-density distribution function (CDDF) is in excellent agreement with observations. The analytical expression elucidates (1) why haloes over a large range in mass contribute about equally to the CDDF as well as (2) why the CDDF evolves so little with redshift in the range z = 2–5. We show that the model also predicts reasonable damped Lyman-αabsorber(DLA) line widths (v90), bias, and molecular fractions. Integrating over the CDDF yields the mass density in neutral gas, $\Omega _{\rm H\,{\small I}}$, which agrees well with observations. $\Omega _{\rm H\,{\small I}}(z)$ is nearly constant even though the accretion rate on to haloes evolves. We show that this occurs because the fraction of time that the inflowing gas is neutral depends on the dynamical time of the halo, which is inversely proportional to the accretion rate. Encapsulating results from cosmological simulations, the simple model shows that most Lyman-limit systems and DLAs are associated with the cosmological accretion of gas on to haloes.
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Liu, Mingjun, Jin Huang, and Mingyue Liu. "Multiple-model switching control for vibration suppression of planar membrane structures." Advances in Mechanical Engineering 11, no. 10 (October 2019): 168781401988377. http://dx.doi.org/10.1177/1687814019883771.
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Membrane space structures have received widespread attention because of their small packaging volume and low mass. However, because membranes are very flexible and lightly damped, vibration suppression in membrane structures is very difficult. The objective of this study was to solve this problem. The first part of this article describes the influence of wrinkling in a membrane structure on the structure’s vibration characteristics. On this basis, the vibration deformations of a wrinkled square membrane structure were derived from the dynamic equations, and the correctness of this vibration model was verified by numerical simulation and experiment. A multi-model system is proposed to simulate the dynamic response of a membrane structure under different boundary conditions. In combination with the drive system, a multi-model switching control method based on adaptive and proportional–integral–derivative control is proposed. Under the initial disturbance, when the vibration amplitude dropped below 0.01 mm, the vibration duration was reduced to 2.96 s, compared with the duration of 12.37 s without control. The duration was shortened by approximately 39.7%, compared with the duration of 4.91 s achieved by the traditional proportional–integral–derivative control method, and by approximately 15.9% compared with the 3.52 s achieved by the out-plane control method. When there were multiple disturbances and the proposed method was used, the boundary displacement loadings did not increase when a certain value was exceeded. This prevented the breaking of the membrane by overstretching and provides a theoretical foundation for setting the initial pre-stress values.
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Romps, David M. "Weak Pressure Gradient Approximation and Its Analytical Solutions." Journal of the Atmospheric Sciences 69, no. 9 (September 1, 2012): 2835–45. http://dx.doi.org/10.1175/jas-d-11-0336.1.
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Abstract A weak pressure gradient (WPG) approximation is introduced for parameterizing supradomain-scale (SDS) dynamics, and this method is compared to the relaxed form of the weak temperature gradient (WTG) approximation in the context of 3D, linearized, damped, Boussinesq equations. It is found that neither method is able to capture the two different time scales present in the full 3D equations. Nevertheless, WPG is argued to have several advantages over WTG. First, WPG correctly predicts the magnitude of the steady-state buoyancy anomalies generated by an applied heating, but WTG underestimates these buoyancy anomalies. It is conjectured that this underestimation may short-circuit the natural feedbacks between convective mass fluxes and local temperature anomalies. Second, WPG correctly predicts the adiabatic lifting of air below an initial buoyancy perturbation; WTG is unable to capture this nonlocal effect. It is hypothesized that this may be relevant to moist convection, where adiabatic lifting can reduce convective inhibition. Third, WPG agrees with the full 3D equations on the counterintuitive fact that an isolated heating applied to a column of Boussinesq fluid leads to a steady ascent with zero column-integrated buoyancy. This falsifies the premise of the relaxed form of WTG, which assumes that vertical velocity is proportional to buoyancy.
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He, Jiang, Lin-Ming Dou, Wu Cai, Zhen-Lei Li, and Yan-Lu Ding. "In Situ Test Study of Characteristics of Coal Mining Dynamic Load." Shock and Vibration 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/121053.
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Combination of coal mining dynamic load and high static stress can easily induce such dynamic disasters as rock burst, coal and gas outburst, roof fall, and water inrush. In order to obtain the characteristic parameters of mining dynamic load and dynamic mechanism of coal and rock, the stress wave theory is applied to derive the relation of mining dynamic load strain rate and stress wave parameters. The in situ test was applied to study the stress wave propagation law of coal mine dynamic load by using the SOS microseismic monitoring system. An evaluation method for mining dynamic load strain rate was proposed, and the statistical evaluation was carried out for the range of strain rate. The research results show that the loading strain rate of mining dynamic load is in direct proportion to the seismic frequency of coal-rock mass and particle peak vibration velocity and is in inverse proportion to wave velocity. The high-frequency component damps faster than the low-frequency component in the shockwave propagating process; and the peak particle vibration velocity has a power functional relationship with the transmitting distance. The loading strain rate of mining dynamic load is generally less than class 10−1/s.