Is the Matlab magnetic levitation model example correct?

Hello.

I don't know what to think. The maglev mathematical equation used in every single Neural Network Toolbox user guide and in the 'maglev' plant model look like this:

But lately, my friend told me that his example (also in Matlab) looked like this:

Moreover, the second equation is the result, other people got when building the equation from scratch.

That leaves me with a question. Which one is correct and why? It is very important thing to me, so if any of you could help me, please do.

Kind regards, Mat.

Answer 1

[Greg Heath]

If you Google

 differential equations magnetic levitation

you will find the y^-2 form

Thank you for formally accepting my answer.

Greg

Answer 2

[Mat]

I understanutd than, but so I don't have any doubts - is the mathematical equation presented in Matlab user's guide and in their examples incorrect?

Answer 3

[David Sanchez]

The force experienced by the ball under the influence of electromagnet is given by

F = mg - Kf (i/y)^2

where i is the current in electromagnet (Ampere), y is the distance of the ball from the electromagnet face

Then, the second equation presented by you is the correct one.