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.

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.

Structural control against earthquakes is becoming increasingly important. The linearquadratic optimal control algorithm is proposed here to design active control system for buildings against earthquake excitations. Full-state feedback system has been adopted. active Tuned Mass Damper is used as the control mechanism. The efficiency of the designed system has been verified against El-Centro earthquake. active control gives 35% more reduction in vibration of the structure than passive control. Mass of the damper has appreciable effects on response parameters than its stiffness. A flexible damper proves to be more effective, but at the cost of actuating forces required. Performance of system is found to be optimum, when mass-damper is tuned to fundamental frequency of the structure. Stability of the structure is also enhanced by active control system. A SDOF building is presented to illustrate the study.

In this paper, equation of motion of three axis attitude dynamic of flexible spacecraft is derived using combination of finite element method and Euler equation. Flexible appendages are modeled by beam elements. Goal of control is target attitude of spacecraft from initial state to desired attitude and suppression of vibration that induced inflexible appendages. So a combination of back stepping and sliding mode control method used for three-axis attitude maneuver of flexible spacecraft and for suppressing vibration of flexible appendage used from active vibration control method by PZT actuator. control law for vibration control is based on LQG method.

In this paper a numerical investigation of installation of actuator in a toggle configuration for decreasing of active control forces in engineering structures has been carried out. During the past two decades, researchers have been focused to prevent the vibration of tall building from strong earthquakes. For achieving this purpose, they applied either massive conventional bracing or passive energy dissipation dampers. Subsequently, they developed active control systems in structures to resist against the high seismic loads. However, this later method eventuates installing massive actuators in building which are not only very costly and uneconomically but also needs large electricity power. In this research, using by known earthquakes, investigation of the effects of the toggle configuration on actuator forces has been performed numerically. For numerical investigation, active tendon control system was selected as a comparison. The numerical investigation shows significant reduction in actuator forces through using toggle configuration. Finally, comparing results through the numerical processe express high matching that relies on mitigation of control forces in the toggled active model.

In active Structural control using the Pole assignment method, determination of suitable values for the eigenvalues of closed-loop control system is very important and the maximum responses of the controlled structure is very sensitive to it. Here, this problem is formulated as an optimization problem using the exterior penalty function method and a new algorithm is suggested for it. The results of study for several numerical examples, reveals the efficiency of the new algorithm compared to the previous ones.

In this paper, control of forced vibration amplitude of a rotating FGM conical shell is studied using FGPM patches. Four piezoelectric patches are placed inner and outer of the shell. In order to obtain the system dynamic equations, the energy method and the classical plate theory are used and simply supported boundary conditions are considered. Each system variable is considered as an expression by separation of variables with variable-time coefficients. Subsequently by substitution the considered responses in the energy functions and finally using the Lagrange equation, the governing equations of the system are obtained. Natural frequencies are compared with the result of previous researches in the case of non-rotating and rotating shell. Also to control vibration, velocity feedback is used so that sensor voltage, which is dependent on the surface, thickness, and location of each sensor, is calculated and used in the actuator voltage. In the following section, control of the system is done for first mode and then convergent system, which in both cases, Closed-loop system well dampens amplitude of forced vibrations.

The active vibration control of a smart cantilever rotary beam, using dual sensor and actuator piezoelectric patches stuck on the outer surface of the beam, is studied. Motion equations are discretized by finite element method with 6 and 9 DOF elements for parts without piezoelectric patches and with them, respectively. Several types of controllers such as LQR, LQG and rate feedback controller are employed to actively control vibrations of the beam. Simulation results exhibit a better performance in terms of settling time for the LQR controller due to all states’ feedback; while rate controller is only relying on the sensor patches for feedback which is convenient in terms of cost. Also, the effect of the number of piezoelectric patches is studied.