Top PDF Hierarchical semi-active control of base-isolated structures using a new inverse model of magnetorheological dampers

Hierarchical semi-active control of base-isolated structures using a new inverse model of magnetorheological dampers

Hierarchical semi-active control of base-isolated structures using a new inverse model of magnetorheological dampers

Magnetorheological (MR) dampers have received special attention as semi-active devices for mitigation of structural vibrations. Because of the inherent nonlinearity of these devices, it is difficult to obtain a rea- sonable mathematical inverse model. This paper is concerned with two related concepts. On one hand, it presents a new inverse model of MR dampers based on the normalized Bouc–Wen model. On the other hand, it considers a hybrid seismic control system for building structures, which combines a class of pas- sive nonlinear base isolator with a semi-active control system. In this application, the MR damper is used as a semi-active device in which the voltage is updated by a feedback control loop. The management of MR dampers is performed in a hierarchical way according to the desired control force, the actual force of the dampers and its capacity to react. The control is applied to a numerical three-dimensional benchmark problem which is used by the structural control community as a state-of-the-art model for numerical experiments of seismic control attenuation. The performance indices show that the proposed semi-active controller behaves satisfactorily.
Show more

14 Read more

Semi-Active Control of Structures Using a Neuro-Inverse Model of MR Dampers

Semi-Active Control of Structures Using a Neuro-Inverse Model of MR Dampers

The training is carried out upon the generated data using the Levenberg-Marquardt algorithm [12], which is encoded in Neural Networks Toolbox in MAT- LAB [13] under the `trainlm' routine. Finally, testing and validation of the trained network is investigated using a few sets of new data for a 30 s period. Figure 5 shows the training testing and validation velocity, forces and voltage records used in constructing the NIMR model. Additionally, Figure 5 compares the forces computed by the MR damper model based on the generated random voltage to the forces computed by the MR damper model based on the predicted voltages by NIMR. Moreover, the predicted voltage record from the NIMR is compared to the randomly generated targets and presented in Figure 5. It is clear that, in general, the predicted voltages are reasonably close to the target voltages. The near perfect match in the training region indicates that the NIMR model is well trained. Henceforth, the NIMR model will be used to compute the required voltage for a specic force and velocity. This will alleviate problems resulting when using a control algorithm that computes only the optimal control forces.
Show more

8 Read more

Semi-active control of base-isolated structures using a new inverse model of MR dampers

Semi-active control of base-isolated structures using a new inverse model of MR dampers

In this paper we rstly discuss a new inverse model for MR dampers which are represented using the normalized Bouc-Wen model [1], [6]. Then, using this inverse model, we consider a hybrid seismic control system for building structures, which combines a set of passive base isolators with a semi-active control system. Because the force gener- ated in the MR dampers is dependent on the local responses of the structural system, the desired control force cannot always be produced by the devices. Only the control voltage can be directly controlled to increase or decrease the force produced by the devices. The desired control force is based on an active controller presented in [18] which has shown sufcient compatibility with the inherent characteristics of MR dampers. In general, in the semi-active control strategies presented in the literature, for instance [10], [11], [20], [27], they managed a single MR damper per oor or, in the case of multiple MR dampers, they receive the same command voltage. In this work, a new practical method has also been dened to compute the command voltage of each MR damper independently according to the desired control force. The management of these MR dampers is based on a hierarchical strategy: we rst compare the total damping force generated in the MR dampers with respect to the desired control force and then we decide what dampers need to apply more damping force and the corresponding command voltage. The whole method is simulated by considering a three- dimensional smart base-isolated benchmark building [16] where the MR dampers are used as supplemental damping devices. This benchmark problem is a new generation of benchmark studies by the American Society of Civil Engi- neering (ASCE) Structural Control Committee, that offers a carefully modeled real-world structure in which different control strategies can be implemented and compared. The performance indices demonstrate that the proposed semi- active method can effectively suppress structural vibration caused by earthquake loading and can provide a desirable effect on structural performance.
Show more

6 Read more

Design Optimization of MagneShock Magnetorheological Shock Absorbers and Development of Fuzzy Logic Control Algorithms for Semi-Active Vehicle Suspensions

Design Optimization of MagneShock Magnetorheological Shock Absorbers and Development of Fuzzy Logic Control Algorithms for Semi-Active Vehicle Suspensions

theoretically important, “skyhook” damping can only be mimicked in practical applications, leading to a variety of alternate control strategies developed to achieve similar results [2,3,6,16,18,19,22,14,27,51,38,45,50]. These algorithms frequently exhibit significant improvements in vehicle ride quality (often quantified in terms of the RMS sprung-mass acceleration) and handling performance (often quantified as reduced fluctuations in tire-road contact forces). Although “skyhook” damping considers only the vertical (bump) vehicle response, additional rigid body responses (pitch and roll) and suspension travel requirements have been studied in significant detail [6,49]. Modern control approaches, including linear quadratic regulators [2,22,45,51] and pole placement algorithms [18], along with intelligent control techniques [6] have been extensively researched for active suspension applications.
Show more

103 Read more

Controlling structures by inverse adaptive neuro fuzzy inference system and MR dampers

Controlling structures by inverse adaptive neuro fuzzy inference system and MR dampers

Effectiveness of the proposed controller is dependent on defining a correlation between response of structure and control signals. Here, ANFIS calculates control force based on current and previous time steps of acceleration feedback. Acceleration is selected for feedback control because accelerometers are durable measuring devices with a small power requirement which are widely available and relatively inexpensive (Schurter & Roschke 2001[22]). Three controllers are used for first, second and third story of the 3-story, and a controller is used for 76-story building. To actuate the structure for generating data, control force is generated randomly using band limited white Gaussian noise. Acceleration due to this force is calculated considering nonlinear material behavior described by Ohtori et al. (2004)[17] and briefly presented in this paper for 3- story and linear behavior for 76-story building.
Show more

13 Read more

Hardware-in-the-loop simulation of magnetorheological dampers for vehicle suspension systems

Hardware-in-the-loop simulation of magnetorheological dampers for vehicle suspension systems

based directly upon the frequency response of the system. An alternative approach is to compare the direction to the actual force, and so – as expected – RMS value of one performance indicator against the performance of the semi-active force generator another, as a function of a control parameter. This is deteriorates. Nonetheless, when the desired force is known as a conflict diagram [9], and the optimal a dissipative one, the force tracking accuracy is very system will have its operating point closest to the good as before. Furthermore, it was found that an origin where all of the performance indicators have energy input was only required for 20 per cent of the been minimized.
Show more

15 Read more

Semi-active damping using a hybrid control approach

Semi-active damping using a hybrid control approach

Universities of Leeds, Sheffield and York http://eprints.whiterose.ac.uk/ This is an author produced version of a paper published in Journal of Intelligent Material Systems and Structure[r]

30 Read more

Study of Alloy Springs with Magnetorheological Dampers for Vibration Isolator Device

Study of Alloy Springs with Magnetorheological Dampers for Vibration Isolator Device

Vibrat ion is a factor that must be controlled during the manufacturing process; variation in workpiece dime n- sions often results in inaccuracies due to v ibration. This study adopted a spring and electro magnetic -repulsion and magnetorheological da mper that can absorb the energy of e xte rnal vibrat ions and deduced the influential vibrat ion factors. ANSYS was e mp loyed to determine the energy that could be absorbed by the vibration isolation device under mach ine vibrat ion, and the Taguchi method of quality engineering was used to design the structure of the device (metal spring, wire dia meter, and materia l). The usabil ity of the product was e xa mined for applicat ion in computer nume rica l control and tradit ional machines. The considered parameters of the magnetorheological fluid were density, coefficient of elasticity, and Poisson’s ratio. The results indicated that sprin g wire diameter exerted the strongest effect on the device’s performance and that the electrical current provided to the damper could be buffered .
Show more

6 Read more

Seismic Vibration Control of Buildings using Viscoelastic Dampers and Base Isolation System

Seismic Vibration Control of Buildings using Viscoelastic Dampers and Base Isolation System

x t is obtained by filtering a white noise process acting at the bed rock through a linear filter which represents the surface ground. This is the well-known Kanai– Tajimi stochastic process [Tajimi 1960] which is able to characterize the input frequency content for a wide range of practical situations. The process of excitation at the base can be described as:

9 Read more

Group Method of Data Handling for Modeling Magnetorheological Dampers

Group Method of Data Handling for Modeling Magnetorheological Dampers

In this section we compare the results obtained using the three proposed methods described above (GMDH, two- tier GMDH, and GMDH with stepwise regression) with two previously published techniques. These two model- ing techniques are neural networks (NN) and adaptive neurofuzzy inference systems (ANFIS) [11,12,19]. The results using ANFIS are taken from [12] since the same dataset has been used in our work. Nonetheless, for NN we have reproduced the results since previous work [11] used a different dataset. The NN architecture that we used is feed-forward network with 11 neurons in the in- put layer, 22 neurons in the hidden layer and one neuron in the output layer. Network training is done via back- propagation.
Show more

10 Read more

Comparing Semi Active Control of Bridge via Variable Stiffness and Damping Systems and MR Dampers

Comparing Semi Active Control of Bridge via Variable Stiffness and Damping Systems and MR Dampers

A type of three-span continues concrete bridge as a target used in this study. This continues box Girder Bridge having a total length of 340m with the main span of 160m and two end spans of 90m and the cross sectional details are shown in Fig 4. This continues bridge was modeled using 30 MPa ultimate strength concreate and 190 MN weight of the girder. The maximum allowable displacement is 0.3m this continuous bridge model without controller is used as a model for evaluating the control system. By placing damper devices between the girder and the pier as shown in Fig 5, the damper force generated due to the piston movement will be adjusted independently for each damper based on the control algorithm which is discussed below.
Show more

14 Read more

Semi-active Control of Building Structures using Variable Stiffness Device and Fuzzy Logic

Semi-active Control of Building Structures using Variable Stiffness Device and Fuzzy Logic

In the present study, semi-active control devices with variable stiffness are utilized to modify the stiffness and the natural vibration characteristics of the structure to which they are attached. Such systems have been investigated for seismic response control by Kobori et al. [10], Nemir et al. [16], Loh and Ma [17], Yamada and Kobori [18], Yang et al. [19] and Nagarajaiah [20]. The variable stiffness devices are engaged/ released so as to include or not include the stiffness of the bracing system of the structure, respectively. The device is composed of a balanced (double-acting piston rod) hydraulic cylinder with a normally closed solenoid control valve inserted in the tube connecting the two cylinder chambers. The solenoid valve can either be on or off, thus opening or closing the fluid flow path through the tube, respectively. When the valve is closed, the fluid cannot flow and effectively locks the beam to the braces below. In contrast, when the valve is open the fluid flows freely and disengages the beam/brace connection (Figure 1). The operation of each device consumes approx. 20 W of power. The system may be regarded as fail-safe in the sense that the interruption of power causes the variable stiffness devices to automatically engage which increasing the stiffness of the structure [4, 21].
Show more

14 Read more

RECOMMENDATIONS FOR THE DESIGN AND CONSTRUCTION OF BASE ISOLATED STRUCTURES

RECOMMENDATIONS FOR THE DESIGN AND CONSTRUCTION OF BASE ISOLATED STRUCTURES

In particular, structures whose lateral strength is provided by shear walls which carry a comparatively small proportion of the total gravity load (Fig. 12) may rock despite their ap[r]

22 Read more

Analysis of the explicit model predictive control for semi-active suspension

Analysis of the explicit model predictive control for semi-active suspension

Explicit model predictive control (MPC) enhances applica- tion of MPC to areas where the fast online computation of the control signal is crucial, such as in aircraft or vehicle con- trol. Explicit MPC controllers consist of several a ffine feed- back gains, each of them valid over a polyhedral region of the state space. In this paper the optimal control of the quarter car semi-active suspension is studied. After a detailed theoret- ical introduction to the modeling, clipped LQ control and ex- plicit MPC, the article demonstrates that there may exist regions where constrained MPC/explicit MPC has no feasible solution. To overcome this problem the use of soft constraints and com- bined clipped LQ /MPC methods are suggested. The paper also shows that the clipped optimal LQ solution equals to the MPC with horizon N = 1 for the whole union of explicit MPC re- gions. We study the explicit MPC of the semi-active suspen- sion with actual discrete time observer connected to the explicit MPC in order to increase its practical applicability. The con- troller requires only measurement of the suspension deflection. Performance of the derived controller is evaluated through sim- ulations where shock tests and white noise velocity disturbances are applied to a real quarter car vertical model. Comparing MPC and the clipped LQ approach, no essential improvement was detected in the control behavior.
Show more

18 Read more

SEISMIC ANALYSIS OF FIXED BASED AND BASE ISOLATED STRUCTURES

SEISMIC ANALYSIS OF FIXED BASED AND BASE ISOLATED STRUCTURES

Many structures constructed with utmost techniques which have undergone severe damages due to Earth quakes lead to enormous loss of life and property. This emerging problem all over the world made engineers to develop innovative systems onEarth Quake Resistant Systems. The major criterion of a structure is to enhance the structural safety economically against severe damages caused due to natural calamities such as Earth quakes.

12 Read more

Seismic resistant design of base isolated multistorey structures

Seismic resistant design of base isolated multistorey structures

where Wi is a portion of the total weight W located at level i. This equation describes the vertical distribution of lateral force based on an assumed uniform distribution of seismic acceleration over the height of the superstructure. A similar assumption had been proposed by Skinner and McVerryl3.4) as discussed in Section 3.2.1. The only difference lies on the specific limitation set for the two approaches. Skinner and McVerry applied the assumption for isolated structures with a fundamental period (on fixed-base) not greater than 0.5 sees, whereas SEAONC required that the fixed- base fundamental period should not be greater than 20% of the "effective period". It shoul be noted, however, that the same effective fundamental period can be obtained for short period structures mounted on a BI system with either thin or fat hysteresis loops. As will be shown later in Chapter 4, structures on a BI system with thin history analized loops have a uniform shear force distribution as predicted by Eq. 3.28. However if the structure has a fat loop BI system, this equation may lead to severely underestimated storey shears, especially in the upper storeys.
Show more

316 Read more

SSHLDA: A Semi Supervised Hierarchical Topic Model

SSHLDA: A Semi Supervised Hierarchical Topic Model

Supervised hierarchical topic modeling and unsupervised hierarchical topic modeling are usually used to obtain hierarchical topics, such as hLLDA and hLDA. Supervised hierarchi- cal topic modeling makes heavy use of the in- formation from observed hierarchical labels, but cannot explore new topics; while unsu- pervised hierarchical topic modeling is able to detect automatically new topics in the data space, but does not make use of any informa- tion from hierarchical labels. In this paper, we propose a semi-supervised hierarchical topic model which aims to explore new topics auto- matically in the data space while incorporating the information from observed hierarchical la- bels into the modeling process, called Semi- Supervised Hierarchical Latent Dirichlet Al- location (SSHLDA). We also prove that hLDA and hLLDA are special cases of SSHLDA. We conduct experiments on Yahoo! Answers and ODP datasets, and assess the performance in terms of perplexity and clustering. The ex- perimental results show that predictive ability of SSHLDA is better than that of baselines, and SSHLDA can also achieve significant im- provement over baselines for clustering on the FScore measure.
Show more

10 Read more

Analysis and control of semi-active suspension system for  a quarter car model

Analysis and control of semi-active suspension system for a quarter car model

Comparison of body acceleration is shown in Table 2, it is seen that, ANFIS is giving an experience of least body acceleration, thus making a ride more comfort for the passenger as compared to the suspension system, which is getting external power source by PID controller and Neural Network. The choice of controller also depends on the use and cost efficiency of the suspension system, external power source can be preferred by any control strategy as each controller provides very less acceleration, but when precision is required as in case of sports vehicles, the controller which provides least body acceleration should be preferred.
Show more

6 Read more

Smart double panel with decentralised active dampers for control of sound transmission

Smart double panel with decentralised active dampers for control of sound transmission

These problems are traditionally solved by passive means. For example, the resonance effect can be reduced by increasing the damping using dissipative treatments. Alternatively, the response of the structure can be influenced by changing mass and stiffness properties of the structures in order to avoid excitation of the most efficient radiating modes [1]. Finally, special designs can be used, such as double panel construction. For example, a typical passenger compartment of a civil transport aircraft is equipped with an additional inner shell of non-metallic, lightweight material. Thus a thin air cavity is formed between the inner and the outer skin. The cavity is suitable for placing of high density fibreglass blankets, for the improvement of both acoustical and thermal insulation. In contrast to a single skin vibroacoustic system, the sound power transmission ratio of such a double panel decreases steeply above the mass-air-mass resonant frequency where the sound transmission is governed by mass law [2]. If the dissipating material is placed in the cavity, it can increase the damping levels of the system, and it is successful for high frequency noise attenuation. However, in passenger transport vehicles noise sources tend to be effective in a broad frequency band. Thus they excite the structure at low frequencies below the cut off where the mass law starts governing the transmission of sound and below the frequencies at which the dissipating material treatments are effective. For example, the source which mainly contributes to the interior noise of a jet aircraft during the cruising regime is the turbulent boundary layer (TBL). Under typical cruise conditions, the excitation spectrum generated by TBL pressure fluctuations is significant between 100 Hz and 2000 Hz [3]. Since the dissipating material (high density fibreglass blankets) is only effective at higher frequencies, the sound at lower frequencies is efficiently transmitted through the double fuselage skin and causes the noise in the cabin [3].
Show more

84 Read more

Evaluation of the Vertical Distribution of Base Shear Force in Base-Isolated Structures

Evaluation of the Vertical Distribution of Base Shear Force in Base-Isolated Structures

Since the introduction of the newly proposed seismic analysis provisions for base-isolated structures, various investigations have been carried out to eval- uate the proposed guidelines. In an intensive study, Kircher and Lashkari investigated the validity of the SEAONC86 static analysis procedure [9]. They con- sidered a rigid superstructure located on a grid of 45 isolators with 13 dierent bilinear hysteretic behaviors. The isolation system properties covered an entire range of interest in seismic isolation i.e., eective periods of 1 to 4 seconds and eective damping ratios from 6% to 39% of critical damping. The parametric study was carried out using a comprehensive collection of 29 pairs of properly scaled horizontal earthquake accelerograms. In general, the study conrmed that the recommended displacement by the static analysis procedure for isolation systems is reasonable. This study ignored superstructure exibility, bi-directional interaction in the base-isolation systems and the fact that the bilinear hysteretic models did not strictly apply to frictional systems, since they all had a yield displacement of 0.5 inches. The eect of bi-directional
Show more

12 Read more

Show all 10000 documents...

Related subjects