Spacecraft attitude tracking control based on nonlinear H _∞, control

This paper addresses the problem of attitude tracking controller design of a rigid spacecraft, whose nonlinear equations of motion is considered directly without linearization. The Modified Rodrigues Parameters (MRP) is used as kinematic variables, which allows principal angle rotations up to 360°. By applying nonlinear H_∞ control theory, we design an attitude tracking controller which guarantees a prescribed L₂ gain performance for the closed-loop system. That is, the L₂ gain from exogenous disturbance to performance output is less than a scalar. To the best of our knowledge, this approach represents the first solution to the attitude tracking control problem for MRP representation. Numerical simulations are eventually included, and the results show that the derived nonlinear H_∞ controller ensures global asymptotical stability and disturbance attenuation capacity of the closed-loop tracking error system.