Dynamic Powers-Based Nonsingular Practical Fixed-Time Tracking Control for Rigid Spacecraft via Modified Rodrigues Parameters

In this paper, the fixed-time attitude tracking control for spacecraft is investigated. By introducing dynamic powers, a novel terminal sliding function and a novel nonsingular fixed-time practical tracking control law are developed. In particular, the dynamic powers in the developed sliding function and control law are constructed by the modified Rodrigues parameters (MRPs) and the sliding mode variable, respectively. An important feature of the proposed dynamic powers-based sliding function is that it does not introduce negative powers into the control law. Moreover, it is proven that the attitude tracking error converges into a small adjustable neighborhood of the origin in a fixed time. Finally, a numerical simulation is conducted to verify the proposed theoretical results.