Volumetric singularity index for a steering law of control moment gyros

Control moment gyros (CMGs) are main actuators of many artificial satellites for attitude control. However, there are singular conditions where control torque along a certain direction cannot be generated. As a solution to this problem, an index is introduced to determine how close the configuration of CMGs is to the singular conditions, and control laws use this singularity index to keep CMGs away from the singular conditions. Here, a new singularity index is proposed and its effectiveness is verified. This index is a kind of volume of three-dimensional bodies that is made by torque vectors of CMG modules. This index can check the singular conditions exactly, and it is faster than other indices to calculate the 1st and 2nd derivatives of the index which are necessary for control laws. The computing speed is important for performances of embedded control systems. The proposed index has been tested by a simulation technique. Especially, a test bench has been developed, and one CMG module is realized by servo motors. The proposed index has been verified to work well without any problem with a hardware CMG module by several tests. © ICROS 2017.