Spacecraft 3-Axis Attitude Control by Space Robot Motion

This palper is concerned with a spacecraft attitude control by a space robot motion. The space robot motion IS characterized by the nonholonomic nature, in wlucli a closed trajectory in the robot joint space yields an attitude cliange of the spacecraft. Tlvo dimensional. i.e.. planer. robot motion lias been extensively discussed by mruiy authors. Especially, an approach using Green's Tlieorem lias been widely applied since the attitude cliruige of a spacecraft is given by line integrals along each joint tra.jectory. A robot motion with closed joint trqjcctories can be transferred to a surface integral. Based on the above considerations, a simple and approximate method for a spacecraft 3-axis attitude control is proposed in this paper. A space robot is mounted on a spacecraft and is assumed to have three rotary joints. ylw. pitcli and pitcli one. Tlie spacecraft attitude will be controlled by the space robot motion where closed trajectory. cubic-like, in three dimensional joint space will be repeated cyclically. This corresponds to tlie closed trajectory motion on reduced tluee-two dimensional joint spaces and approximate method of two dimensional, planer. operation. A simulation result is also presented to show the validity of tlus approach.