Attitude Maneuver Tests, CMG, Agility, Three-Axis Free Dynamics Simulator, Singularity, Null Motion

What is it about?

This paper presents attitude maneuver demonstration tests using control moment gyroscopes mounted in a three-axis free dynamics simulator that provides an on-ground test environment of free rotational movement around three axes using the air-floating method. The issue of torque error between the torque command and the actual output torque is discussed in relation to the singularity-robust based steering law for spacecraft maneuvers. The torque error is analyzed using singular value decomposition to determine its magnitude and direction. Based on the analysis, feedback control and steering laws are proposed to reduce the torque error. Before conducting the maneuver demonstration test, a preliminary simulation is performed using a simplified dynamics model, control law, and steering law. The maneuver test results indicate that the dynamics simulator successfully accomplishes agile, large angle, and rest-to-rest multitarget maneuvers as well as precision pointing.

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Why is it important?

This study aims to present control and steering laws designed to mitigate the torque error and demonstrate agile maneuver tests using the simplified control and steering laws, as implemented in the dynamics simulator. First, in Section 2, the dynamics simulator configuration will be introduced. Second, Section 3 provides an overview of the dynamics model, control law, and steering law proposed by Kanzawa et al. Third, in Section 4, the torque error induced by the singularity-robust based steering law with null motion will be analyzed using SVD theory to determine its magnitude and direction. Based on the analysis, feedback control and steering laws will be proposed to produce less torque errors in the vicinity of a singularity. In Section 5, before conducting the maneuver demonstration tests using the dynamics simulator, a preliminary simulation is performed on the basis of the simplified model to predict the behavior of the dynamics simulator and CMGs. Finally, in Section 6, the maneuver demonstration test results are shown, and the tested performance is compared with the predicted performance obtained through numerical simulation.