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Abstract: Appealing to the principle of vertical residence and stemming the horizontal expansion of the city, the Tehran Milad Tower is being built on 35000 sm3 site with the total area of 220000 sm3. With a height of over 170m, this 56-story concrete building is in the final stages of construction and would be the highest residential building of Iran. Since Tehran is located in a high-risk earthquake zone, all of its structures must be designed for seismic loads. In this building, the lateral loads are carried with three main shear walls, which are located in an angle of 120 degrees and the gravity loads are transferred from the concrete slabs to the secondary shear walls. Since the introduction of Tuned Mass Dampers (TMD) by Frahm in 1909, as a passive control system, numerous investigations have been carried out to examine the effect of these devices in reducing seismic response of the structures. The objective of incorporating a TMD into a structures is to reduce the energy dissipation demand on the primary structural members subjected to external forces. This reduction is accomplished by transferring some of the structural vibration energy to the TMD and dissipating the energy at the damper of TMD. The purpose of this paper is to design and evaluate the effectiveness of TMD for response reduction of the Tehran tower under seismic excitations. A lumped mass model of the building was provided with 112 translational and 56 rotational degrees of freedom using solid and shell elements. Time history analyses were performed to calculate the response of the structure subjected to some earthquake records. The same procedure was followed for the models with attached TMD. The control effectiveness of TMD was evaluated by comparing the tower's responses with those of the towers without control device. Furthermore, multiple tuned mass dampers are suggested as a solution for insufficiency of TMD.

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Vibration control of large flexible structures in new dynamic systems has significantly encountered with many challenges. In this area, there are several approaches of vibration control implemented on complicated dynamic systems in which the change of vibrational characteristics with the time of process leads to performance violation. In this paper, regarding the estimation of undesired vibration frequency of a flexible structure, input control of the dynamic system is reconstructed. In this regards, the input of the dynamic system is made to minimize the magnitude of the vibration. This strategy in which the control input is constructed by means of undesired vibration frequencies is similar to use of anti-viruses in medicinal approaches. The proposed control strategy is implemented on yaw channel of a flexible sounding rocket in order to reduce the destructive effects of bending vibration. The system responses show the effects of the vibration on the yaw channel of the system are significantly decreased.

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Gears are one of the important sources of vibrations and noise in industrial rotating machinery and power transmission systems. In order to design and develop an optimal and quiet geared power transmission system, this paper presents the design of an active vibration control for gear-bearing system. A dynamic model of the geared system is presented, where some undesired parameters in the design such as manufacturing errors, teeth deformations, mounting errors as well as external excitations resulting from distributions of applied torque are included. An active control system is presents in order to control and attenuate the disturbance impress on the system vibrations. The idea behind the design of this control system is to reduce vibration transmissibility by the introduction of the excitation forces in the bearing. The controller is investigated and designed by using feedback control and based on the H-infinity control approach. It can be presented as an optimization problem. To solve this optimization problem, Particle swarm optimization (PSO) algorithm is used, which is one of the optimization methods available among artificial intelligence. The simulation results are performed to investigate performance of the control system.

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In this paper, in order to reduce a landing gear vibration two adaptive control systems are designed considering the landing and taxi phases. For this purpose, 6 degree of freedom equations of motion of the landing gear and the related transfer functions are extracted. A reduced order model of the overall transfer functions are given as a result of complicated dynamic model. A Lyapunov based model reference adaptive control is designed to absorb the vibration of front wheel of the landing gear at touchdown. In addition, a minimum variance adaptive controller is designed and implemented on the system to reject the band level disturbances during the taxi phase. The band disturbances are modeled as a colored Gaussian noise and the system parameters as well as noise characteristics are estimated using extended least square approach. Both control systems are investigated to assess the best performance. Numerical simulations of the system in Matlab/Simulink environment show the preferences and satisfactory performances of the proposed vibration control systems. These results are calculated against various inputs including model reference adaptive control and minimum variance approaches

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In this paper, an intelligent robust controller is proposed for a class of nonlinear systems in presence of uncertainties and bounded external disturbances. The proposed method is based on a combination of terminal sliding mode control and adaptive neuro-fuzzy inference system with bee’s algorithm training. For this purpose, a sliding surface is firstly designed based on terminal sliding control method. This sliding surface is considered as input for the intelligent controller which is an adaptive neuro-fuzzy inference system and using it, terminal sliding mode control law without the switching part is approximated. In the proposed method, an intelligent bee’s algorithm is also used for updating the weights of the adaptive neuro-fuzzy inference system. Compared with fast terminal sliding mode control, the proposed controller provides advantages such as robustness against uncertainty and disturbance, simplicity of controller structure, higher convergence speed compared with similar conventional methods and chattering-free control effort. The method is applied to an atomic force microscope for nano manipulation. The simulation results show the robustness and effectiveness of the proposed method.

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Unbalance mass and imperfect bearings are the main sources of vibration in rotor dynamics systems. One way to decline and control of a rotor vibration is the use of magnetic absorbers. The magnetic absorber is used to control the position of the rotor and reduce its vibration. In this study, by applying the dynamic absorber system force and creating two new natural frequencies, the magnetic absorber brings the system out of the resonance. Moreover, in order to decrease the vibration amplitude, two different types of dynamics absorbers are designed in which they are checked by the magnetic absorber in a specific range of rotational frequency. In magnetic absorber controller system, the continuous force which is applied to the main system by mass absorber is restored in sixteen levels discontinuously. It is seen that the vibration amplitude is reduced 13% in the area of natural frequency in comparison to the magnetic absorber with discontinuous force. In this paper, two different mass ratios are considered for each one of the two absorber systems. It is observed that in the case of dynamic absorbers with higher mass ratio, rotor vibration amplitude and the maximum force amplitude of the dynamic absorber system decrease. This issue can increase the accuracy of magnetic absorber system in the renewal of the dynamic absorber system force and reduce consumption electrical energy of the control system as well.

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Tall buildings, due to their significant flexibility in horizontal direction, exhibit very limited inherent damping. As such, their resonance or near-resonance excitations induced by wind loads may result in lateral structural response values that exceed the serviceability limit states of the structure. A mass damper when attached on a tall building can significantly mitigate the near-resonance lateral response of the structure. Tuned liquid column dampers (TLCDs) which consist of one or more U-shaped vessels with partially-filled water are known as a common type of mass dampers. In the conventional type of these dampers, an orifice is located at the horizontal portion of the vessel to dissipate the energy of the oscillating liquid within the damper. In the new type of these dampers, the orifice is replaced by a coated steel ball that is immersed in water at the horizontal portion of the vessel to dissipate the oscillating energy of the liquid within the damper. The latter damper is termed as tuned liquid column ball damper (TLCBD). In this paper the performance of a set of different TLCDs and TLCBDs in response mitigation of a tall building (of 75-stories) under harmonic wind loads have been investigated. A large set of time history analysis runs have been performed to study the role of different damper design parameters on the lateral response of the tall building. The design parameters investigated in this paper include geometrical and mass properties of the liquid dampers, inherent damping of structure, and the frequency of input excitation. The outcome of analysis runs has been compared to highlight the cons and pros of TLCDs and TLCBDs in wind-response mitigation of the building. Results of this study indicate that both damper-types are effective in response mitigation of the original structure. The peak roof displacement is decreased by 50% to 88% as a result of using the liquid dampers in the structure. Given the mass and geometrical properties of dampers, the performance of TLCBDs will be superior to that of TLCDs in response mitigation of tall buildings. Based on the analyses conducted in this paper the attenuation of building deformations in a system equipped by a TLCBD is 5% to 25% larger than the case where the same system is equipped by a TLCD. However, the performance of TLCBDs is more sensitive to the frequency of input excitations. An increase in the mass of the damper, in both TLCD and TLCBD systems, results in an increased response mitigation. For instance, when the mass ratio of damper is increased from 1% to 5%, the peak lateral displacement of structure, depending on the type and geometry of damper, is further decreased by 30% to 50%. The length of the horizontal portion of the U-shaped vessel of the damper was found also to be significantly influencing the response mitigation efficiency of damper in both TLCD and TLCBD systems. When the length of the horizontal portion of the damper is increased from 0.5 to 0.9, the roof displacements experience approximately 30% to 40% further reduction.

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Boring operations due to the large length to diameter ratio and the high flexibility of tool are prone to self-excited (chatter) vibration. This vibration may cause poor surface quality, low dimensional accuracy and tool breakage. In practice, chatter is the main limitation on production rate. The main reason of chatter phenomenon is the dynamic interaction between cutting process and structure of machine tool. By increasing the length of the cutting tool, the vibration tendency in the tool’s structure increases. Improving dynamic stiffness of the tool is the most effective solution for decreasing vibration and increasing chatter stability. For increasing the stability of the tool in long overhang boring operations, passive and active vibration control has been proposed and implemented. In active control methods, vibrations can be effectively damped over a various cutting conditions. The aim of this research is to enhance chatter stability of an industrial boring bar by increasing the dynamic stiffness. A VCA actuator is used for active vibration control. The designed setup can effectively suppress undesirable vibrations in the radial direction. First, modal parameters of the boring bar are determined by experimental modal analysis. Then, the transfer function of the actuator-tool setup is identified with the sweep frequency excitation. In the following, the direct velocity feedback is successfully implemented in the vibration control loop. The results of cutting tests indicate that the actuator has a great performance in suppressing vibrations and increasing the dynamic stiffness. Hence, the developed method can significantly increase chatter stability of boring operations.

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One of the most important constraints on manufacturing productivity is the machining vibrations. This vibrations may cause increase in machining costs, lower accuracy of products and decrease tool life. The effective solution for increasing cutting process stability and vibration suppression is to improve structural dynamic stiffness. There has been presented different techniques for enhancing dynamic stiffness of structures using passive and active vibration control methods. Although passive vibration control methods are always stable, they exhibit limited performance. In active control methods, vibrations can be effectively damped over a various conditions. The aim of this research is to enhance the dynamic stiffness of an industrial boring bar by using active damping. Cutting process mainly exposed to parameter perturbations and unknown external disturbances, therefore, designing an active vibration control system for cutting process is a challenging problem. In this research an extended state observer based control strategy was proposed that can overcome these uncertainties. The proposed strategy was implemented into an active vibration control system for a boring bar. Moreover, the direct velocity feedback is successfully implemented in the vibration control loop. The results of impact tests indicate that the control algorithms have a great performance in suppressing vibrations and increasing the structural dynamic stiffness. Voltage impact results show that ADRC controller spends less control effort than direct velocity feedback controller.

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In this research, control of vibration in multilayered cylindrical panel with piezoelectric patch, under dynamic load is investigated, for the first time. The finite element method is used to solve the dynamic equations of the structure, which is based on first-order shear deformation theory, and equivalent single layer models with different rotations for the substrate and the piezoelectric patch is developed. The governing equations are obtained by using the Hamilton’s principle of virtual work, are discretized over the mid-plane, by using eight node shell element, leading into the matrix system of equations. The maximum controllability criterion is used for finding the optimal size and location of piezo-patch. According to the used control law, the applied voltage on the piezo-patch is proportional to the radial velocity component at the point, where the sensor is installed. In order to evaluate the performance of the formulation and finite element model, the natural frequencies obtained for the substrate laminated panel are compared with those in the literature. Then, having the dynamics of the optimal system, the frequency response for open and closed loop controls are studied. Finally, the effects of controller gain values and dimensions of panel and patch on the time response and damping rate of vibrations are illustrated.

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Damages caused by the impact of adjacent structures in past major earthquakes have shown the importance of structural control systems to reduce the seismic risk of the impact of structures. Connecting energy dissipation devices to adjacent buildings is a practical and effective approach to prevent collisions as well as reduce the seismic responses of structures, and this issue has been an active research field in recent years. One of the semi-active control methods is the use of MR dampers. These dampers use a magnetic fluid that produces large damping forces in a piston-cylinder system that can be controlled instantly by changing the applied voltage to the damper. The Bouc-wen model has been used to take advantage of the unique properties of MR damper as well as to consider its inherent nonlinear behavior. In this study, to evaluate the performance of MR dampers using a fuzzy control system, three- and nine-story standard structures under seismic excitation of two near-field earthquakes including Kobe (1995) and Northridge (1994) and two far-field earthquakes including El centro (1940) and Kern county (1952) with maximum accelerations of 0.1g to 1g are investigated.
The MR damper is connected to the third floor level of the two structures and can produce a controlled force equivalent to 1000 kN. The fuzzy system is designed based on the displacement of the third floor of two structures to reduce the risk of collision of structures as well as reduce seismic responses. the benchmark buildings have been modeled in OpenSees and the fuzzy control system was implemented in MATLAB software. The displacement responses of the third floor of structures are considered as the input value of the fuzzy system and the required voltage of MR damper is considered as the output value of the fuzzy system. In addition, triangular membership functions have been used to determine the degree of membership of input values.
 In general, the control system designed under far-field earthquakes has shown better performance in reducing the responses of two structures compared to near-field earthquakes. According to the results obtained from the dynamical analysis, the fuzzy system used under far-field earthquakes compared to near-field earthquakes and based on evaluation criteria of J1 (maximum roof displacement), J2 (maximum roof acceleration), J3 (maximum Base shear) and J4 (maximum relative displacement of floors) in three-story building 17.35, 4.94, 3.58, 12.17% and in nine-story building 7.93, 7.05, 0.67, 9.13%  showed better performance, respectively. Also, according to the evaluation criterion of J5, which is related to the minimum required gap between two buildings, the fuzzy system used under far-field earthquakes has shown 9.71% better performance than near-field earthquakes.