An analysis of on-line autonomous Robust tracking Controller based on variable structure Control is presented for an aerospace launch vehicle. Decentralized Sliding-Mode Controller is designed to achieve the decoupled asymptotic tracking of guidance commands upon plant uncertainties and external disturbances. Development and application of the Controller for an aerospace launch vehicle during atmospheric flight in an experimental setting is presented to illustrate the performance of the Control algorithm against wind gust and internal dynamics variations. The proposed Sliding Mode Control is compared to non-linear and time-varying gain scheduled autopilot and its superior performance is illustrated by simulation results. Furthermore, the proposed Sliding-Mode Controller is convenient for implementation.

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 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 the recent Internet advances, congestion Control is considered as an important issue and has spurred a significant amount of research. In this study, second-order Sliding Mode Control is used to adjust the average queue length and maintain the closed-loop system performance. The Control law is obtained in two steps. First, the nonlinear state-space form of the network is extracted based on state variables as the average queue length and congestion window size. Then, the proportional-Integrator-derivative and proportional-derivative Sliding surface are defined according to the tracking error. Also, in order to avoid chattering, the derivative of the Sliding surface is considered and the closed-loop system stability is investigated based on Lyapunov theory. The proposed scheme renders good tracking specifications and closed-loop system Robustness. The simulation results show that the proposed methods outperform proportional integral (PI) and proportional integral derivative (PID) schemes. Also, Robustness to disturbances increases and chattering and transient response degradation are avoided.

This study addresses the design and properties of a Sliding-Mode neural-network Control (SMNNC) system for a nonlinear flexible arm that is driven by a permanent magnet (PM) synchronous servo motor. First, the dynamic Model of a flexible arm system with a tip mass is introduced. When the tip mass of the flexible arm is a rigid body, not only bending vibration but also torsional vibration occurr. In this study, the vibration states of the nonlinear system are assumed to be unmeasurable, i.e., only the actuator position can be acquired to feed into a suitable Control system for stabilizing the vibration states indirectly. Then, a SMNNC scheme without the feedback of the vibration measure is proposed to Control the motor-mechanism coupling system for periodic motion. All adaptive learning algorithms in the SMNNC system are derived in the sense of Lyapunov stability analysis, so that the system-tracking stability can be guaranteed in the closed-loop system. The effectiveness of the proposed Control scheme is verified by both numerical simulation and experimental results.

In spite of improvement of the AC drive systems still the DC drives are widely used in industry. One of the problems associated with Control of DC motor which might cause unsuccessful attempts for designing a proper Controller would be the time-varying nature of DC motors parameters and variables which might be changed while working with the motion systems. In these conditions, the Control systems will not response properly. One of the best suggested solutions to overcome this problem would be the use of Sliding Mode Control (SMC). SMC is not sensitive to parameters changes and yet would have a fair response to the systems variations. However, SMC suffers from some deficiencies including inflexibility in Controller parameters. A Better response can be achieved by SMC in compare with classical methods but it is not the most optimized response. The fair solution can be defined through faster fulfillment of target, less overshoot and more consistency of the system against the changes of the parameters. In this paper, a new fuzzy based method is presented to increase the SMC ability to reach a more convenient solution. Optimized response can be achieved in terms of shorter settling time, less overshoot, and more stability.

This paper investigates the problem of finite-time stabilization of a class of uncertain nonlinear systems and a Controller is proposed based on combination of integral Sliding Mode Control with finite-time state feedback. The proposed Controller consists of two parts. One part rejects matched uncertainties and the other part provides finite time stability. An adaption mechanism is also employed to estimate unknown parameters of the system. The proposed Control law guarantees finite-time convergence of the Sliding variable in the presence of uncertainties and unknown parameters. By elimination of the reaching phase, in which the system states are quite sensitive to any uncertainties or disturbances, the Robustness of the system is guaranteed throughout the entire response. Furthermore, the upper bound of disturbance and uncertainties is not required to be known in advance which makes the suggested Controller more flexible in terms of implementation.

Maneuvering and Controlling the attitude with the highest accuracy, speed and lowest power consumption has always been one of the challenges in the field of spacecraft Control system design. The flexibility of satellites causes a change in the dynamics of the whole system. In this article, the Robust Quasi-Sliding Mode Control (RQSMC) method has been utilized to Control the attitude of the flexible spacecraft in the presence of disturbances. Considering the non-linearity of the equations of the flexible spacecraft, the impossibility of Modeling this system ideally and the inability of mathematical descriptions to fully explain the movement of this flight system, this article uses the RQSMC method as a suitable idea for the attitude Control of the flexible spacecraft. For this purpose, the three-degree-of-freedom Model of the flexible spacecraft including different disturbances in each direction under quaternion kinematics will be presented in the dynamic Modeling section of this article, and then a RQSMC will be designed that also has the ability to Control chattering.  The checking of functional parameters such as energy consumption index, agility index and body angular rates constraints showed that this Controller has a desirable performance in accurate and fast spacecraft orientation.