Time-optimal attitude maneuver for underactuated spacecraft based on Pseudospectral method

The time-optimal attitude maneuver problem of a rigid spacecraft with only two control torques along its principal axes is studied using Radau Pseudospectral Method (RPM). The asymmetric and symmetric spacecraft have been considered in particular. First, we establish the attitude dynamical models of asymmetric and symmetric spacecraft with two controls, and use (w, z) parameter to describe the attitude motion. Second, according to the general optimal control problem like Bloza form, the maneuver time minimum as the performance index is selected to be optimized, simultaneously considered the control inputs and angular velocities boundary in the practical application of engineering. Finally, the optimal maneuver problem is discretized based on the Radau Pseudospectral Method and then converted into a nonlinear programming problem. Simulations for asymmetric and symmetric system are carried out based on GPOPS toolbox and the analysis results illustrate the feasibility the proposed algorithm.