Control
Sevil M. Sadigh; Narges Talebi Motlagh; Hossein Behesgti; Sahand Moharrami; Moharram Shameli
Abstract
In this paper, an adaptive fault-tolerant control based on modified nonsingular fast terminal sliding mode control is developed for attitude tracking of a satellite with three magnetorquers and one reaction wheel. The proposed approach is designed to be robust in the presence of actuator faults, external ...
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In this paper, an adaptive fault-tolerant control based on modified nonsingular fast terminal sliding mode control is developed for attitude tracking of a satellite with three magnetorquers and one reaction wheel. The proposed approach is designed to be robust in the presence of actuator faults, external disturbances, and inertia uncertainties and preserve the acceptable performance of system. The adaptive law is designed to estimate the upper bound of uncertain expressions, increase the tracking accuracy, and improve the performance of system. This parameter with a coefficient of sliding surface variable are used in the reaching phase of control law to achieve the chattering-free phenomenon. Stability and finite-time convergence of attitude variables is proved by the extended Lyapunov condition. To increase the tracking accuracy and compensate the required torque, a reaction wheel is used as a redundancy. Also, for increasing the control accuracy, the dynamics of this actuator is considered as well as the constraints of magnetorquers and reaction wheel. The simulations are performed and compared with the similar control method under the mentioned conditions to evaluate the performance of the proposed method. The results show the finite-time convergence, increasing the tracking accuracy, smoothing of satellite attitude changes, and generating the chattering-free control signals.
control
Sevil M. Sadigh; Hossein Behesgti
Abstract
In this paper, a passive fault tolerant control method is proposed for the satellite attitude tracking in the presence of external disturbances, the inertia matrix uncertainties, and reaction wheel faults. To achieve this goal, a modified fast terminal sliding model approach is used due to its robustness ...
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In this paper, a passive fault tolerant control method is proposed for the satellite attitude tracking in the presence of external disturbances, the inertia matrix uncertainties, and reaction wheel faults. To achieve this goal, a modified fast terminal sliding model approach is used due to its robustness against the un-modeled uncertainties and being suitable for the nonlinear system model. The sliding surface variable is chosen to avoid singularity, converge to zero in a finite time, and also reduce the Chatting phenomenon. The stability and finite time convergence of the attitude variables are also demonstrated by the extended Lyapunov method. In order to increase the accuracy of the designed controller, the dynamic model of the mentioned actuators is considered. Finally, in order to evaluate the performance of the proposed method, the simulation is performed on a satellite with four reaction wheels under the mentioned conditions. The results show that the proposed method can maintain the stability of the system despite the occurrence of actuator faults, and it makes the state variables converge to the desired trajectories in a finite time and also produce chattering-free control signals.
