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.

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.

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.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

When designing new civil, mechanical or aerospace systems that will experience dynamic excitation in their operating environment, it is desirable to quantify the predicted performance of a proposed design in terms of the reliability that it will achieve the specified design objectives. In view of the uncertainties about the modeling of systems and about the future dynamic excitation the system will experience, the design team can specify a set of possible dynamic inputs and a set of possible models of the system and then choose probability distributions over these sets to model the uncertainties. One can then evaluate the ‘ failure probability’ of the design that measures how likely the system will achieve the desired performance over its operational lifetime, based on available information and the probability models chosen to represent the missing information. Because of the uncertainty inherent in engineering structures, consistent probabilistic stability/performance measures are essential to accurately assessing and comparing the robustness of structural control systems. Several reliability estimation methods, procedures and algorithms with various capabilities, accuracy and efficiency have been suggested in the past. A quantitative comparison of these approaches is considered to be most instrumental and useful for the engineering community. An approach is presented herein for calculating such probabilistic measures for a controlled structure. Subset Simulation method is shown to be appropriate for the required calculations. The original version of Subset Simulation, SubSim/MCMC, employs a Markov chain Monte Carlo (MCMC) method to simulate samples conditional on intermediate failure events it is a general method that is applicable to all the benchmark problems. The concepts are illustrated through several examples of seismically excited structures with active protective systems. The results show that the original version of Subset Simulation based on the Metropolis– Hasting algorithm is robust and efficient in estimating the probability of failure of structural systems with complex failure regions, large numbers of random variables, and small probabilities of failure. and applicable to all problems.

This paper presents a new control methodology for active power filters that provide an adaptive online harmonic estimation with partial and selective harmonic reduction schemes, which has been implemented within an integrated controller. The proposed approach is to provide partial and selective reduction of those individual harmonics which exceed the recommended levels as set by regulatory bodies reduces the rating of active power filters thus leading to cost savings. This approach contrasts with existing techniques in which the objective is to reduce all possible harmonic components to zero. Performance evaluation of the proposed technique for harmonic estimation for time-varying non-linear load is carried out when the simulation and experimental results show that the proposed control strategy provides a new alternative for harmonic reduction in power system.

It is aimed to minimize the structure response against the earth vibration by the use of the open loop control system. In such a control, only one predicting neural network is utilized, which estimates only the earth vibration. The neural network is instructed by some recorded acceleration data, and it is able to predict the acceleration variation for the subsequent step. The control force is equal to the product of the mass of each story to its next step acceleration. This control system leads to the approximate minimum response. Moreover, to guarantee the system stability, a linear controller is added to the system. The resulted mixed control system can assure the system stability and also has better performance. Finally, the effect of the structural mass variation on the control system is investigated. The findings show that the effect of the structural mass variation on the mixed control system is smaller than the one by the predicting neural network.

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.

The reliability of vibration control systems is influenced by uncertainties in dynamic parameters of structure, the characteristics of controller, and external excitations. When designing controllers for structures with unspecified or unavailable specifications, identification methods for estimating dynamic parameters and controller design offer a practical solution. However, controllers based on identification methods are subject to two main sources of error: modeling inaccuracies and identification errors. By comparing the performance of controllers designed using identification methods with those based on assumed models, it is possible to evaluate the impact of identification accuracy on control effectiveness. This approach minimizes the negative effects of uncertainties in structural parameters while reducing the costs associated with intelligentization. In this study, uncertainties considered in structural parameters and external excitations. Initially, a primary control system was designed, and the structure was identified using the stochastic subspace identification based on recorded responses. Subsequently, a secondary controller was designed based on identification. The failure function was defined as maximum difference in displacement response of the upper story of structure between two controllers. Using this metric, the reliability of control system was estimated. The results showed that the identification-based controller achieved a success rate of 99.75% compared to original controller. However, the statistical distributions of the performance indexes for the identification-based controller exhibited a lower mean and higher standard deviation than those of assumed-model-based controller. This improvement is likely influenced by the lower accuracy and higher estimated damping ratios of the identified structures, which contribute to increased reliability of identification-based controller.