Engineering Notes Backstepping Control Design with Actuator Torque Bound for Spacecraft Attitude Maneuver

BACKSTEPPING is a popular nonlinear control design technique [1,2]. It hinges on using a part of the system states as virtual controls to control the other states. Generating a family of globally asymptotically stabilizing control laws is the main advantage of this method that can be exploited for addressing robustness issues and solving adaptive problems. The term backstepping refers to the recursive nature of the control design procedure in which a control law and a control Lyapunov function are recursively constructed to guarantee stability. Backstepping has been considered for the spacecraft slew maneuvers [3,4]. The cascaded structure of spacecraft kinematics and dynamics makes the integrator backstepping a preferred approach for the spacecraft attitude maneuver problem, resulting in smooth feedback controls [5]. However, the typical control actuators used for this problem (such as reaction wheels, control moment gyros, or thrusters) have an upper bound on the control torque they can exert onto the system and the simple or conventional backstepping control method may result in excessive control input beyond that saturation bound. The issue has been addressed in the literature using other control methodologies such as nonlinear proportional–integral–derivative control [6], Lyapunovoptimal control [7] and variable structure control [8–11]. In this work, we design a nonlinear backstepping attitude controller using the inverse tangent-based tracking function [4] and a family of augmented Lyapunov functions [12]. Using this control law, we derive an analytical upper bound of the control torque norm. The bound is effectively used to tune the control parameters so that, for the given settling time specification, the upper bound of the control input is minimized. The performance of the proposed controller has shown improvements in minimizing the peak control torque and the settling time. The rest of the Note is organized as follows: First, the kinematics and dynamics of rigid spacecraft are summarized. Second, the details of the design procedure for the proposed controller and the analytical bounds for the control torque components are given. Third, the efficacy of the proposed scheme is demonstrated by the numerical simulations for the cases of attitude stabilization and tracking both. Finally, the conclusions are presented.