Predefined-time Attitude Tracking Control for Spacecraft without Velocity Measurement

This paper investigates the attitude tracking control problem of spacecraft under the conditions of external disturbances and inertia uncertainties, in the absence of velocity feedback. By utilizing the spacecrafts attitude information, a model-free adaptive state observer is designed to estimate the spacecrafts attitude and angular velocity within a predefined time. Based on the estimated information, a continuous and non-singular sliding surface as well as an adaptive predefined-time controller are constructed. These designs ensure that the tracking error of the spacecraft ultimately converges to a small neighborhood around the equilibrium point. The effectiveness of the proposed designs is verified through simulations.