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, in order to CONTROL the relative motion for spacecraft formation flying, an OPTIMAL SLIDING MODE CONTROLler is presented. This CONTROLler is designed based on the linearized equations of relative motion in circular orbit and applied to nonlinear system that is subjected to external disturbance. Firstly OPTIMAL CONTROLler is designed based on linear quadratic (LQ) method, and then integral SLIDING MODE CONTROL technique is used to robustify the CONTROLler. It is assumed that spacecrafts move in low-earth orbits and J2 perturbation is considered as external disturbance. Using Lyapunov second method, the stability of the closed-loop system is guaranteed. The performance of the proposed CONTROLler in tracking the desired trajectory is compared to SLIDING MODE CONTROLler and simulation results show the effective performance of the proposed CONTROLler.

This paper presents an OPTIMAL robust adaptive technique for CONTROLling a certain class of uncertain nonlinear affine systems‎. ‎The proposed approach combines SLIDING MODE CONTROL‎, ‎a linear quadratic regulator for OPTIMALity, and gradient descent as an adaptive CONTROLler‎. ‎ The convergence of the SLIDING MODE CONTROL process is proven using two theorems based on the Lyapunov function. Simulation results for pendulum and inverted pendulum systems demonstrate that the proposed method outperforms both the linear quadratic regulator technique and ‎the‎ ‎SLIDING‎ ‎MODE‎ ‎CONTROL regarding reduced chattering and improved reaching time‎.

In this paper, a new guidance law is designed for missile against maneuvering target by integrating OPTIMAL CONTROL SDRE technique and SLIDING-MODE CONTROL. Due to the fact that autopilot dynamic has a very important role in success or unsuccess of engagement in terminal phase, and it can make delay in guidance commands execution, this dynamic is taken into account in state equations. The robustness of the designed guidance law against disturbances is proved by the second method of Lyapunov. The proposed guidance law does not need accurate target maneuver profile and just need the maximum value of the target maneuver. Coefficients in proposed guidance law are obtained using genetic algorithm. For investigating effectiveness of proposed guidance law, by considering different scenarios, three-dimensional missile-target engagement is simulated. Then results are compared with conventional augmented proportional navigation guidance (APNG) law. Simulation results show that the proposed guidance law has high robustness against target maneuver disturbances and also one can compromise between convergence speed, intercept time and CONTROL effort.

MODEling and CONTROL of Unmanned Aerial Vehicle is undoubtedly one of the most active areas in the field of CONTROL engineering. The characteristics of aerial vehicles such as nonlinear dynamics, time variability and the structural and parametric uncertainties make flight CONTROL issue relatively a complex and important subject in their design. One of the widely used methods in this area is SLIDING MODE CONTROL technique. This paper proposes the design, the simulation, and the analysis of two CONTROLlers namely PID and SLIDING MODE in order to OPTIMALly CONTROL the pitch angle of an unmanned aircraft. Initially, in order to dynamically MODEl the system, an appropriate mathematical MODEl is presented to describe the longitudinal motion of aircraft. Subsequently, a robust SLIDING MODE CONTROLler is designed using particle swarm optimization (PSO) algorithm to CONTROL the pitch angle of an aircraft against the uncertainties and the external disturbances. The OPTIMAL parameters are determined by minimizing both the CONTROL signal and tracking error. Then, the performance quality of the proposed method was compared with the results of the OPTIMAL PID CONTROLler in terms of transient response characteristics. Finally, simulation results indicated that the proposed SLIDING MODE CONTROLler can reduce the overshoot of system response and yield more robust performance than PID for the CONTROL of pitch angle.

External disturbances and internal uncertainties with an unknown range, as well as the connection between the human body and robot, are major problems in CONTROL and stability of exoskeleton robots. In order to deal with disturbances and uncertainties with the known range of the system, the SLIDING MODE CONTROLler is used as a robust approach. The chattering phenomenon is one of the drawbacks of SLIDING MODE CONTROLler, which boundary layer is employed to reduce the effects of this phenomenon. In this case, not only the chattering phenomenon is not completely eliminated, but the robust characteristics of the CONTROLler are mitigated. In this paper, in order to cope with the disturbances and uncertainties with unknown range, and guard against chattering as a key ingredient of excessive energy consumption and convergence rate reduction, OPTIMAL adaptive high-order super twisting SLIDING MODE CONTROL has been applied. The dynamic MODEl of a lower limb exoskeleton robot is extracted using the Lagrange method in which four actuators on the hip and knee joints of the left and right legs are considered. To achieve OPTIMAL performance, CONTROLler parameters are determined using Harmony Search algorithm by minimizing an objective function consisting of ITAE and CONTROL signal rate. The proposed CONTROLler performance is compared with OPTIMAL adaptive supper twisting SLIDING MODE and OPTIMAL SLIDING MODE CONTROLlers which shows the superiority of the OPTIMAL adaptive high-order SLIDING MODE CONTROLler rather than other designed CONTROLlers.