DC Motor Modeling

[jophuds]

Hi,

I'm trying to model a DC Motor in simulink and I've got the expression I can't get certain values for this expression from the motor's datasheet.
Haas anyone else modeled a DC Motor in simulink and if so how did they do it or has anyone any good info. or links on this kind of stuff.
Thanks very much
joe.

 

[Lewish]

The SimPowerBlockset has several working models for DC motors.

 

[robotboy]

Why on earth would anyone use Simulink for motor modeling? This is a conserved mixed-technology system; current, voltage, thermal, magnetics, etc. And after you have the motor... what next? What loads will you attached? And what design questions are you trying to ask? (e.g. What happens when the shaft experiences a large inertia change due to the load?) Much better to use a lumped-sum simulator like Saber. Simulink excels however for non-conserved, signal-flow (control) systems.

That said... Anyway since a DC motor is linear (and I assume you mean a DCPM motor), is typically a 2-pole system, and trivial to write out a level-1 Laplace transform, but needs a couple pieces (again need to apply feedback for conservation of energy). If you have done this correctly you likely would not be asking this question, because the terms for armature resistance, inductance, inertia, damping, kt, and ke would be staring at you. These are the typical parameters found on any DCPM motor spec sheet.

If you care to share your derived expression (or model somehow), I'm sure I or someone can tell you what's wrong. Since Simulink models are so verbose, I cannot post my DCPM motor version here (yeah despite my earlier complaint, I did construct one for fun - It works, but not anything I would make design decisions from).

Hope this helps!

 

[jophuds]

Thanks for the reply robotboy,

The spec sheet I had for the motor didn't provide the info, but I got a similiar motor with spec's I needed.

The reason I am modelling it in simulink is that I am also trying to model a fuzzy control logic block, and since matlab has a nice little fuzzy logic toolbox, I decided it would be easiest to use.

If you have any thoughts on a better method or any good papers or sites on this type of thing, i'd really appreciate it.

 

[nootherhandle]

hi

I don't know how complex a model you guys are talking about.
I think you can implement a fairly good PMDC model in Matlab.

I agree with Robotboy that you might need to account for variable shaft inertia etc. ... Where I disagree with him is in the solution ( "use Sabre" ) ...

... the solution is to allow for that in your model ... don't simplify your equations to a Transfer function. Model your equations straight --- so you can incorporate the changes as "inputs" to your PMDC model.

I have what I think is a decent model that should be more than sufficient to test out the Fuzzy Logic toolbox.
-- contact me at ramesh_gkAThot_mail.com ( rewrite that address with @ in place of AT and without the underscore in hot_mail.com)

 

[MachinaMan]

Hi jophuds,

Someone has already done this. You can get the Mechatronics Simulink Library (aka MSL). Just google it and download it.

This library has sevral motor models built in to blocks and ready to use, all you have to do is insert your specs into the block.

hope this helps,

René