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Control Force (control + force)

Distribution by Scientific Domains

Engineering	100%

Selected Abstracts

Probabilistic Approach for Nonlinear Modal Control of MDOF Structures Subjected to Multiple Excitations

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2005
Kyung-Won Min
For the modal control of the MDOF structure, a new eigenvalue assignment algorithm that modifies the dynamic characteristics of only the specific mode is proposed. For the probabilistic evaluation of the proposed nonlinear modal control, the joint probability density function (PDF) of the equivalent nonlinearly controlled single-degree-of-freedom (SDOF) system is obtained by the solution of the reduced Fokker,Planck equation for the equivalent nonlinear system. To overcome the difficulty in the application of the joint PDF to the MDOF structure controlled by the hybrid mass damper (HMD) system and subjected to multiple excitations, the equivalent damping ratio is proposed. The results of the analysis indicate that the proposed nonlinear modal control strategy is effective for the control of MDOF structures requiring a significantly smaller peak control force than the linear quadratic Gaussian (LQG) controller to produce a similar control performance level. [source]

Seismic control of smart base isolated buildings with new semiactive variable damper

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2007
S. Nagarajaiah
Abstract A new semiactive independently variable damper, SAIVD, is developed and shown to be effective in achieving response reductions in smart base isolated buildings in near fault earthquakes. The semiactive device consists of four linear visco-elastic elements, commonly known as Kelvin,Voigt elements, arranged in a rhombus configuration. The magnitude of force in the semiactive device can be adjusted smoothly in real-time by varying the angle of the visco-elastic elements of the device or the aspect ratio of the rhombus configuration. Such a device is essentially linear, simple to construct, and does not present the difficulties commonly associated with modelling and analysing nonlinear devices (e.g. friction devices). The smooth semiactive force variation eliminates the disadvantages associated with rapid switching devices. Experimental results are presented to verify the proposed analytical model of the device. A H, control algorithm is implemented in order to reduce the response of base isolated buildings with variable damping semiactive control systems in near fault earthquakes. The central idea of the control algorithm is to design a H, controller for the structural system that serves as an aid in the determination of the optimum control force in the semiactive device. The relative performance of the SAIVD device is compared to a variable friction device, recently developed by the authors in a separate study, and several key aspects of performance are discussed regarding the use of the two devices for reducing the responses of smart base isolated buildings in near fault earthquakes. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Improved design of sliding mode control for civil structures with saturation problem

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2004
Sang-Hyun Lee
Abstract A systematic and improved design procedure for sliding mode control (SMC) of seismically excited civil structures with saturation problem is provided in this paper. In order to restrict the control force to a certain level, a procedure for determining the upper limits of the control forces for single or multiple control units is proposed based on the design response spectrum of external loads. Further, an efficient procedure using the LQR method for determining sliding surfaces appropriate for different controller types is provided through the parametric evaluation of the dynamic characteristics of sliding surfaces in terms of SMC controller performance. Finally, a systematic design procedure for SMC required to achieve a given performance level is provided and its effectiveness is verified by applying it to multi-degree-of-freedom (MDOF) systems. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003
Part 2: analysis
Abstract The experimental results of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion have been presented and discussed in the companion paper. Based on the identified dynamic properties of both the building and the platform, this paper first establishes an analytical model for hybrid control of the building-platform system subject to ground motion in terms of the absolute co-ordinate to facilitate the absolute velocity feedback control strategy used in the experiment. The traffic-induced ground motion used in the experiment is then employed as input to the analytical model to compute the dynamic response of the building-platform system. The computed results are compared with the measured results, and the comparison is found to be satisfactory. Based on the verified analytical model, coupling effects between the building and platform are then investigated. A parametric study is finally conducted to further assess the performance of both passive and hybrid platforms at microvibration level. The analytical study shows that the dynamic interaction between the building and platform should be taken into consideration. The hybrid control is effective in reducing both velocity response and drift of the platform/high-tech equipment at microvibration level with reasonable control force. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Rider's net moment estimation using control force of motion system for bicycle simulator

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 11 2004
Jae-Cheol Shin
One of the challenging problems with bicycle simulators is to deal with the virtual bicycle dynamics that is coupled with rider's motion. For the virtual bicycle dynamics calculation and the real time simulation, it is necessary to identify the control inputs from the rider as well as the virtual environments. The steering, pedaling, and braking torques can be easily measured by using torque sensors and the virtual environments can be generated and provided by a visual system. However, direct measurement of the rider's net moment that significantly affects the bicycle motion is not practical. In this work, it is shown that six control forces of the Stewart platform-based motion system can be used for effective estimation of the rider's net moment, incorporated with the sliding mode controller with perturbation estimation. © 2004 Wiley Periodicals, Inc. [source]

Optimal multi-interval control of a cantilever beam by a recursive control algorithm

OPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 4 2009
Chun-Hung Lin
Abstract The optimal-distributed control of a transversely vibrating cantilever beam is studied with the objective of minimizing the deflection and velocity in a given period of time with the minimum possible expenditure of force. The beam undergoes transient vibrations and is subject to given displacement and velocity initial conditions. The control is exercised by means of a transversely distributed force referred to as the control force. In the present study, a multi-interval optimal control method is developed with the application of a maximum principle. The method consists of dividing the control duration into several intervals and using the maximum principle to obtain the optimality conditions at each interval. The explicit solutions for a cantilever beam are obtained by a recursive algorithm that takes the final conditions of the last interval as the initial conditions of the next interval. The formulation and the method of solution are suitable and convenient for digital computation. Numerical results are given, which compare the deflections, velocities and the control force under the optimal multi-interval control with those under the optimal single-interval control. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Experimental verification of a wireless sensing and control system for structural control using MR dampers

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2007
Chin-Hsiung Loh
Abstract The performance aspects of a wireless ,active' sensor, including the reliability of the wireless communication channel for real-time data delivery and its application to feedback structural control, are explored in this study. First, the control of magnetorheological (MR) dampers using wireless sensors is examined. Second, the application of the MR-damper to actively control a half-scale three-storey steel building excited at its base by shaking table is studied using a wireless control system assembled from wireless active sensors. With an MR damper installed on each floor (three dampers total), structural responses during seismic excitation are measured by the system's wireless active sensors and wirelessly communicated to each other; upon receipt of response data, the wireless sensor interfaced to each MR damper calculates a desired control action using an LQG controller implemented in the wireless sensor's computational core. In this system, the wireless active sensor is responsible for the reception of response data, determination of optimal control forces, and the issuing of command signals to the MR damper. Various control solutions are formulated in this study and embedded in the wireless control system including centralized and decentralized control algorithms. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Improved design of sliding mode control for civil structures with saturation problem

Closed-form solution for seismic response of adjacent buildings with linear quadratic Gaussian controllers

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2002
Y. L. Xu
Abstract Closed-form solution for seismic response of adjacent buildings connected by hydraulic actuators with linear quadratic Gaussian (LQG) controllers is presented in this paper. The equations of motion of actively controlled adjacent buildings against earthquake are first established. The complex modal superposition method is then used to determine dynamic characteristics, including modal damping ratio, of actively controlled adjacent buildings. The closed-form solution for seismic response of the system is finally derived in terms of the complex dynamic characteristics, the pseudo-excitation method and the residue theorem. By using the closed-form solution, extensive parametric studies can be carried out for the system of many degrees of freedom. The beneficial parameters of LQG controllers for achieving the maximum response reduction of both buildings using reasonable control forces can be identified. The effectiveness of LQG controllers for this particular application is evaluated in this study. The results show that for the adjacent buildings of different dynamic properties, if the parameters of LQG controllers are selected appropriately, the modal damping ratios of the system can be significantly increased and the seismic responses of both buildings can be considerably reduced. Copyright © 2001 John Wiley & Sons, Ltd. [source]