In this paper, a new scheme is presented for controlling the structural vibrations, excited by the external dynamic effects such as the earthquake and etc. The proposed method is an active control technique which is compatible with the structural dynamic behavior. In the other words, the proposed active control method is formulated based on the structural dynamics theories. This approach could be used for designing a control mechanism with multi actuators and multi sensors. For this purpose, the actuator’s forces vector is added to the dynamic equilibrium equations of the motion. The vector of the actuator’s forces is independent of the natural dynamic equilibrium equations of system and the elements of this vector are determined based on the active control strategy. This paper presents an innovate concept to formulate the external control forces which are applied to the main structure by the actuators. For calculating the control forces, each actuator force is modeled as an equivalent viscous damper. If there is m actuator attached to the structure, m actuator force should be determined in the control process. Based on the proposed technique, each actuator force is considered as a viscous force, added to the dynamic equations of motion. Therefore, there is m unknown force in the control system. These m unknown parameters should be calculated at each instant time of the control process which leads to reduce the structural vibration. For determining these m unknown actuator forces, m additional equations is required. Here, the critical damping concept of the structural dynamics theory is utilized to prepare the required equations. For this purpose, the actuator forces are determined so that several lower vibration modes are damped critically. In the other words, m actuator force is calculated if the m initial vibration’s modes are in the critical conditions. By creating critical damping condition for m initial vibration’s mode, a set of m simultaneous equations is achieved. In each time instance of the control process, the m actuator forces are determined by solving this set of simultaneous equations. As a result, the proposed control mechanism is formulated by a simple mathematical formulation. On the other hand, the proposed method does not depend on the type of the dynamic load and it could be applied to control each structure with multi degrees of freedom. It should be noted that running these process in the case of multi actuator is the main originality of this paper. In the other words, a similar control procedure is performed for a system with single actuator. For numerical verification of the proposed method, some criterions such as the maximum displacement are evaluated in a five-story shear building which is excited by the seismic load i.e. the Elcentro Earthquake. This study shows that the proposed active control method has sufficient accuracy and suitable efficiency for decreasing the structural vibrations. According to the numerical results, the maximum drift in the upper floor of this five-story shear building is reduced by 55%. By increasing the number of actuators, the control process with higher efficiency is achieved.

This paper studies on active control of structures subjected to near field earthquakes. In order to evaluation of effects of earthquakes with different frequencies three steel structures of 4, 8 and 15 floors with different natural period have been desined using ETABS software based on allowable stress method then opensees software have been used for three dimentional modeling of structures. Considering the impact and frequency content complexity of new field earthquakes, these structures subseetes to new field earthquakes. The different softwares have been used to verify of structures modelling. In order to evaluation of frequency content of earthquake, all of records scaled to 0.6 g then applied to structures. Different dynamic analysis conducted using eleven near field earthquake records and then the results compared to non-controled model to indicate the effect of active tendons.

This article investigates the problem of simultaneous attitude and vibration control of a flexible spacecraft to perform high precision attitude maneuvers and reduce vibrations caused by the flexible panel excitations in the presence of external disturbances, system uncertainties, and actuator faults. Adaptive integral sliding mode control is used in conjunction with an attitude actuator fault iterative learning observer (based on sliding mode) to develop an active fault tolerant algorithm considering rigid-flexible body dynamic interactions. The discontinuous structure of fault-tolerant control led to discontinuous commands in the control signal, resulting in chattering. This issue was resolved by introducing an adaptive rule for the sliding surface. Furthermore, the utilization of the sign function in the iterative learning observer for estimating actuator faults has not only enhanced its robustness to external disturbances through a straightforward design, but has also led to a decrease in computing workload. The strain rate feedback control algorithm has been employed with the use of piezoelectric sensor/actuator patches to minimize residual vibrations caused by rigid-flexible body dynamic interactions and the effect of attitude actuator faults. Lyapunov's law ensures finite-time overall system stability even with fully coupled rigid-flexible nonlinear dynamics. Numerical simulations demonstrate the performance and advantages of the proposed system compared to other conventional approaches.

Based on a discrete dynamic contour model, a method for segmentation of brain structures like thalamus and red nucleus from magnetic resonance images (MRI) is developed. A new method for solving common problems in extracting the discontinuous boundary of a structure from a low contrast image is presented. External and internal forces deform the dynamic contour model. Internal forces are obtained from local geometry of the contour, which consist of vertices and edges, connecting adjacent vertices. The image data and desired image features such as image energy are utilized to obtain external forces. The problem of low contrast image data and unclear edges in the image energy is overcome by the proposed algorithm that uses several methods like thresholding, unsupervised clustering methods such as fuzzy C-means (FCM), edge-finding filters like Prewitt, and morphological operations. We also present a method for generating an initial contour for the model from the image data automatically. Evaluation and validation of the methods are conducted by comparing radiologist and automatic segmentation results. The average of the similarity between segmentation results is 0.8 for the left and right thalami indicating excellent performance of the new method. Additional noise and intensity inhomogeneity changed the evaluation results slightly illustrating the robustness of the proposed method to the image noise and intensity inhomogeneity.

In this paper a new approach to formulation of active control of structures based on energy concepts and use of Linear Quadratic Regulator (LQR) has been proposed. The suggested method eliminates the trial and error procedure in finding appropriate gain matrices in active control of structures. In this method the gain matrix is obtained by considering the energy of the structure and it remains constant for all types of earthquake input.To show the efficiency of the proposed method, a three-story building with two active tendons in the first and third floors is considered. The proposed gain selection and other techniques reported in the literature for LQR controllers have been used to compare the response of the structure for three accelerograms. A comparison of the displacements and control forces shows that although the maximum displacement in the proposed method is negligibly more than classical LQR methods, but the control forces are considerably less than the classical methods. Comparison of the results for an earthquake with various levels of scaling also shows that the proposed method is not sensitive to the intensity of input earthquake.

In this paper, a semi-active multivariable adaptive controller is designed for a framed structure under a seismic disturbance using a filtered-x NLMS optimizer. Actuator and large power supply are not required, since just some valves and a battery-size power supply are sufficient for controlling the amount of hydraulic fluid flow through the by-pass on off-orifice channel in an energy dissipating system ,which consists of a piston attached to L-shaped wind bracing of the building and a cylinder attached to the upper floor. It is assumed that only a rough finite element model of the structure is available. In addition, in order to search for optimal non-classical viscous damp r coefficients, acting as calibration measures for the corresponding orifice size of the by-pass cannels of dissipation systems, the adaptive controller parameters are estimated by Normalized last-Mean-Squares strategy. The simulation results demonstrate that even though the controllability offered by this system does not equal that of an active counterpart, it is almost as effective. Considering low-power requirement for the pro-pose system appears more attractive and practical in real structures.