20.4:1 Metal Gearmotor 25Dx65L mm HP 12V with 48 CPR Encoder

Hello,I need parameters for calculating transfer function of this motor. I will do a project at 12 volts with this dc motor, but I do not have tools to measure for calculations.
Ra: Armature Resistance
La: Armature Inductance
Ia: Armature Current
Ea: Input Voltage (Volt)
Eb: Contrast Electromotive Voltage
Ki: Moment Constant
Kb: Contrasting Electromotive Constant
Ty: The Moment of Load
Tm: Mechanical Moment
Wm: Rotor Angular Velocity
Jm: Shaft Inertia
Bm: Viscous Friction Coefficient

Can you help me for this project?


Many of the parameters you are interested in can be derived from the performance curves in our 25D gearmotor datasheet, which is available on the product page under the “Resources” tab.

Here is a link to a forum post I wrote which outlines how to can do that.

Please note, unlike the motor discussed in that forum post, the inductance of our 12V high-power 25D motors is about 1.4mH.

For moment of inertia calculations, the output shaft on our 25D gearmotors is stainless steel.

- Patrick

Hello again, I calculated the other parameters as you said, but I think it is not correct when calculating the moment of inertia. How should I go about calculating the moment of inertia? Is there a formula you use?

I typically will just refer to this Engineering Toolbox page or this Wikipedia page to find mass moment of inertia equations. Engineering Toolbox or MatWeb would probably be good places to find a density value for stainless steel.

Please keep in mind that this method will not account for the inertia of the gears or the motor’s armature (which we have not characterized), so it will only be a low-side approximation.

- Patrick