Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Problem with calculating the stiffness of a magnetic bearing, using the sensitivity physics interface
Posted Jul 5, 2014, 4:01 p.m. EDT 2 Replies
Please login with a confirmed email address before reporting spam
Hi
I am a student in electrical engineering, and I am very new with COMSOL multi physics. I have got this project where I am to design a magnetic bearing with permanent magnets. To do this, I want to make some simulations in COMSOL, so that I can investigate the force generated and the stiffnes of the bearing. At first I found this tutorial on the COMSOL website
www.comsol.com/model/axial-magnetic-bearing-using-permanent-magnets-14367,
The tutorial uses the 2D axisymmetri, and uses the "magnetic fields (mf) " physics to calculate the force on the bearing, and it uses the "sensitivity" physics, to calculate the stiffness, which is the differential of the force. It also uses the "deformed geometry" physics, but I am not sure why? Well, It all works, and everything is fine, but now I wanted to also see the force in the lateral axis of the magnetic bearing, and I found out that to do this, I had to make a full 3D model. So that is what I did.
The basic build up of the model is as in the tutorial, but now I have made to ring magnets in 3D, where both of them are magnetized in the downward direction (-z), and I calculate the force on the inner ring magnet as a function of it's axial displacement dZ, using "Force Calculation" of the "Magnetic fields" physics, and parameterization. The problem is that even though I can calculate the force on this inner magnet, as a function of its displacement dZ, I get zero at all points of dZ when i calculate the stiffness with the sensitivity physics. The physics are set up as in the 2D model, but I still can't calculate the stiffness. I don't have the "deformed geometry" physics anymore because I thought that it wasn't need with a 3D model, where I don't deform any geometry, and it seems like it is able to calculate the force at least, so I still don't think it has anything to do with that, but well I am not sure, because I am not an expert with COMSOL.
I would be very happy if anyone is able to tell me what could be wrong, and why I cant calculate the stiffness. I have attached the model, but it is without any computed data, because else, the file will be too large to attach in this forum.
Regards
Adam
I am a student in electrical engineering, and I am very new with COMSOL multi physics. I have got this project where I am to design a magnetic bearing with permanent magnets. To do this, I want to make some simulations in COMSOL, so that I can investigate the force generated and the stiffnes of the bearing. At first I found this tutorial on the COMSOL website
www.comsol.com/model/axial-magnetic-bearing-using-permanent-magnets-14367,
The tutorial uses the 2D axisymmetri, and uses the "magnetic fields (mf) " physics to calculate the force on the bearing, and it uses the "sensitivity" physics, to calculate the stiffness, which is the differential of the force. It also uses the "deformed geometry" physics, but I am not sure why? Well, It all works, and everything is fine, but now I wanted to also see the force in the lateral axis of the magnetic bearing, and I found out that to do this, I had to make a full 3D model. So that is what I did.
The basic build up of the model is as in the tutorial, but now I have made to ring magnets in 3D, where both of them are magnetized in the downward direction (-z), and I calculate the force on the inner ring magnet as a function of it's axial displacement dZ, using "Force Calculation" of the "Magnetic fields" physics, and parameterization. The problem is that even though I can calculate the force on this inner magnet, as a function of its displacement dZ, I get zero at all points of dZ when i calculate the stiffness with the sensitivity physics. The physics are set up as in the 2D model, but I still can't calculate the stiffness. I don't have the "deformed geometry" physics anymore because I thought that it wasn't need with a 3D model, where I don't deform any geometry, and it seems like it is able to calculate the force at least, so I still don't think it has anything to do with that, but well I am not sure, because I am not an expert with COMSOL.
I would be very happy if anyone is able to tell me what could be wrong, and why I cant calculate the stiffness. I have attached the model, but it is without any computed data, because else, the file will be too large to attach in this forum.
Regards
Adam
Attachments:
2 Replies Last Post Jul 7, 2014, 6:50 a.m. EDT
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Maybe the deformed geometry is necessary to allow for the movement of your parts?
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Yes, by this time, I think you are right. So I have added the deformed geometry physics to the model, and set it up in the same way as in the tutorial. But now the computation is very slow and in the end it gives me an error about that it won't converge. I feel like I should have the deformed geometry, but I don't know how to use it correctly.
Does anybody know what I am doing wrong?
updated model attached.
Regards
Adam
Does anybody know what I am doing wrong?
updated model attached.
Regards
Adam
Attachments: