Feedback stabilization of single and multiple rigid-body spacecraft in the presence of actuation failures

The notions of reliable systems and fault-tolerant control law synthesis have received tremendous attention by many researchers in the past two decades. To accommodate the stringent requirements on the reliability and longevity of control systems today, automatic control algorithms have become significantly more complex. In this research, our primary objective is to establish a methodology for the design of fault-tolerant control systems. In particular, we consider the problem of single and multiple spacecraft stabilization in the presence of actuation failures. First, families of explicit nonlinear control laws are derived for stabilization of an underactuated rigid-body spacecraft to the zero equilibrium state using control torques supplied by two pairs of thrusters along its principal axes. Results are obtained for both local and global asymptotic stabilization. Next, a novel approach to the feedback stabilization problem in the context of underactuated systems is introduced. Continuous fail-safe control laws are synthesized for accommodation of arbitrary single-axis actuator failure without switching of controllers or a mechanism to determine the time of failure. Stability results are presented for the case of single-axis actuation failure in addition to the case without failure. For the attitude control problem, we show that an underactuated spacecraft cannot be asymptotically stabilized using continuous pure-state feedback control. Control laws are presented for attitude stabilization without actuation failures. Finally, the failure-accommodative findings are extended to a pair of spacecraft flying in formation. Tracking angular velocity control laws are presented for a leader-follower formation framework in the presence of single-axis actuation failure.