Chattering-free Fault-tolerant Attitude Control with Fast Fixed-time Convergence for Flexible Spacecraft
- PDF / 1,653,604 Bytes
- 10 Pages / 594.77 x 793.026 pts Page_size
- 88 Downloads / 193 Views
ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
Chattering-free Fault-tolerant Attitude Control with Fast Fixed-time Convergence for Flexible Spacecraft Seyed Majid Esmaeilzadeh*, Mehdi Golestani, and Saleh Mobayen Abstract: This paper is mainly dedicated to the challenging issue of fixed-time attitude control for a flexible spacecraft in the presence of actuator faults, external disturbances and coupling effect of flexible modes. The attitude controller is developed by employing a fixed-time nonsingular terminal sliding mode under which the convergence time is bounded and independent of the initial states. This robust attitude controller is able to provide superior properties such as fast fixed-time attitude manoeuvring with high pointing accuracy, singularity avoidance and chattering free. More specifically, a new reaching law is employed to provide convergence rate improvement as well as chattering alleviating simultaneously. The actuator fault problem is also considered and the attitude control is achieved even when the actuators experience severe faults. The proposed controller ensures that the closed-loop attitude system is stable in the sense of fixed-time stability concept. Furthermore, since the upper bound of external disturbances and flexible vibrations acting on the spacecraft is not available, an adaptation mechanism is presented. Numerical simulations demonstrate that the proposed controller is able to successfully accomplish attitude control with high attitude pointing accuracy and stability in spite of the actuator faults, flexible structures vibrations and external disturbances. Keywords: Attitude control, chattering reduction, fault-tolerant control, fixed-time stability, flexible spacecraft.
1.
INTRODUCTION
Rapid and high-accurate attitude stabilization for spacecraft is regarded as an advanced technology for numerous tasks including earth observation and formation flying. From a practical point of view, there are multiple disturbances which give rise to some difficulties in enhancing pointing accuracy. On one hand, considerable nonlinearity of the spacecraft dynamics and the inertia matrix uncertainty as well as unknown environmental disturbance have negative influence on the attitude control performance. On the other hand, modern spacecraft are developed with large flexible structures including solar arrays and large antennas. This, in turn, reduces the spacecraft rigidity and the spacecraft is no longer rigid. Since there is a strong coupling between the rigid hub and flexible appendages, attitude manoeuvre can excite flexible appendages’ vibration which may seriously deteriorate pointing accuracy and even lead to the system instability. Considering all these factors brings about challenges to rapid manoeuvring performance [1]. Despite numerous robust attitude controls for space-
craft, the asymptotic convergence is just guaranteed. The spacecraft attitude system is ensured to be stable only after infinity time. Nevertheless, the fast manoeuvring is of crucial importance for
Data Loading...
