Discrepancy between simscape and analytical solution

I am trying to simulate the behaviour of an electromechanical actuator, to model the BLDC I am using the block "Permanent Magnet

Synchronous Machine" with "Mechanical input" set into Mechanical rotational port.

The output of the block comprehends the rotor velocity in rad/s between the various informations.

I also connected the Mechanical rotational port to a set of gears modeled through simscape blocks (i'll provide an image to clarify).

When I compute the actuation speed through a direct conversion of the motor velocity from rad/s to mm/s i obtain a value which is different from the one coming from the set of simscape gears.

In the picture the green line is the mechanical rotational port of the aforementioned block, while the series of gain is the simple conversion of the motor velocity from rad/s to mm/s

Am I using some of these blocks in the wrong way? It actually would seem to me a pretty straightforward application but apparently I'm missing something.

The gear ratio are all correct and so are the units of measure of the conversion blocks of the simscape section of the image.

At the moment I was using for the feedback control the velocity computed directly with the gains (black line) while I was using the green one only to apply the load to the motor, since otherwise I don't see a way to model an external load, could this be a correct approach to the problem?

Thank you in advance, i will be extremly greatful to the ones who will answer, if you need more details feel free to ask me anything that could make the problem more clear to understand.

[Yifeng Tang]

Sharing the actual model may help more people understand your question.

Some other information can also be useful:

What is the expected answer? What does the model show?

Any intermediate answer you can look into, for example the speed at the plentary gears in between? Try compare to the Simscape results in the Simscape Result Explorer and see where the results appear to be different.

A simple way to model external load is to use a damper/friction + a mass/inertia. At least you'll get more resistance (load) as speed increases, which is usually the case, and get some time constant behavior. Adjust the damping coefficient will give you different level of load.

[Alberto Moretti]

Sorry for the late answer and thank you for your time.

When looking at the speed in rad/s directly exiting the Permanent Magnet Synchronous machine block it is close to the actual maximum rotational speed of the motor ideally computed, on the other hand the angular velocity of the Simscape section comes to a maximum way before that.

Concerning the Load, I actually need a constant one but thank you for the advice.

I will try the comparison between the Simscape Result Explorer. The fact is that at this point I don't know which data to believe