How to simulate orthogonal torque rods perfectly using simscape and simulink?

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I am preparing a model a magnetorquer on simscape and its 3 axis control circuit using PID controller in simulink. I have got a partial success in that regard, but there are issues in the same.

1. I am giving just the yaw component to move two torque rods and keeping one stationary i.e. the stationary torque rod will move on its own axis (thus producing torque and move the other two axes). I am trying to do that, but ultimately all three rods come in motion.

2. There are problems in the frames of the rod, and the sphere connecting them, I presume. How to fix that?

Answer 1

[Nicolas Schmit]

When you apply a torque to one of the rod, it starts spinning around its axis. But since the rods have masses, the two other rods that are moving off-axis create inertia forces that eventually makes your system moving around all three axes. If you modify your system so that the joint is at the center of each rod, or add counter weights to make the make the inertia matrix diagonal at the joint, your will not have this problem anymore.

Also, you should also always add a World Frame to your model so that there is a common reference to define the position and orientation.

[Adarsh Agrawal]

That actually made sense. Thanks for your answer. Our issue is resolved now!