Document Type : Original Article

Authors

• Sevil M. Sadigh ¹
• Narges Talebi Motlagh ¹
• Hossein Behesgti ²
• Sahand Moharrami ¹
• Moharram Shameli ³

¹ Actuators Group, Space Thrusters Institute, Iranian Space Research Center, Tabriz, Iran

² Head of Actuators Group, Space Thrusters Institute, Iranian Space Research Center, Tabriz, Iran

³ Space Thrusters Research Institute, Iranian Space Research Center, Tabriz, Iran

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 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.

Keywords

• Satellite attitude tracking
• sliding mode control
• finite-time convergence
• magnetorquer
• actuator faults

Main Subjects

• Control