Understanding HingedRigidBodyStateEffector

[AmolikaSoni]

Hey all,
I am working on a simulation for Solar Panel Deployment using the HingedRigidBodyStateEffector module. I have used the example scenarioDeployingPanel.py for reference and it works (mostly). As I was going through the code of HingedRigidBodyStateEffector module I encountered the function HingedRigidBodyStateEffector::updateEffectorMassProps where multiple frame conversions using DCMs are done. These conversions are to convert from hinge frame to body frame mostly. There is one conversionthis->dcm_SH = eigenM2(this->theta);which I am not able to understand. This code line means that we are converting the frame about the 2nd axis of the hinged body. Now from what I see is that this means my solar panel deployment is supposed to be happening about the Y axis. Why and how this axis was fixed? And also, there is no formal documentation available for it! @schaubh please help!

[schaubh]

The hinged rigid body module assumes the panel frame is rotating about the 2nd body axis. The module documentation at

http://hanspeterschaub.info/basilisk/Documentation/simulation/dynamics/HingedRigidBodies/hingedRigidBodyStateEffector.html

links to the journal paper that discusses this work in more detail. Or, see the dissertation by Dr. Cody Allard (No. 15) at

http://hanspeterschaub.info/phd.html

This module has some assumptions on the hinged body as outlined in this paper and dissertation. There is a newer effector called the spinningBodyOneDOFEffector at
http://hanspeterschaub.info/basilisk/Documentation/simulation/dynamics/spinningBodies/spinningBodiesOneDOF/spinningBodyOneDOFStateEffector.html
It is a more general version where the panel inertias and center of mass location can be arbitrary.