Exponential Tracking Control of Spacecraft Attitude Dynamics: Explicit Relationship Between Convergence Rate and Input Constraints

This article provides a novel solution for spacecraft attitude control systems with input constraints. It reveals that both the convergence rate and stabilization boundary of the state trajectory are explicitly coupled with the maximum output amplitude of actuators. Specifically, an innovative control framework is introduced to achieve exponential stability of the attitude tracking error dynamics system. Therein, the control variables are augmented using a bounded hyperbolic tangent function, transforming the traditional second-order attitude control system into a higher-order one to circumvent the input constraint issue. The derivation of the controller leverages the backstepping methodology and dynamic surface technology. The properties of the bounded functions ensure that the actual input signals are strictly less than the actuator constraints. Furthermore, the framework incorporates an adaptive estimation method to ascertain the upper limit of external perturbations, thereby ensuring the system's exponential stability despite control input constraints and environmental disturbances. Simulation studies verify the accuracy of the presented findings.