75:1 Metal Gearmotor 25Dx69L mm HP 12V with 48 CPR Encoder

Hello everyone,We need some parameters for calculating transfer function of this motor.
can you help me ?

Ra: Armature Resistance
La: Armature Inductance
ia: Armature Current
ea: Input Voltage (Vort)
eb: Contrast Electromotive Voltage
Ki: Moment Constant
Kb: Contrasting Electromotive Constant
Ty: The Moment of Load
Tm: Mechanical Moment
Wm: Rotor Angular Velocity
Um: Angular Position of the Rotor
Jm: Shaft Inertia
Bm: Viscous Friction Coefficient


From your list, it seems like you might not understand the purpose for finding the transfer function of a DC motor. In a system model, the DC motor is generally the plant of your system. It is the part in the system for which you provide an input (voltage) based on a target output (like angular velocity or position) and feedback that have been processed by a control scheme (like PID). So it does not make sense to ask for many of the parameters you listed because they are either inputs, outputs, or intermediated values from your system model. They are not part of the motor transfer function. In your list, these include the armature current, input voltage, contrast electromotive voltage, moment of load, mechanical moment, rotator angular velocity, and angular position.

The FAQs tab on the product page describes how you can find many of the parameters you need using the specification we provide. This way, you can determine armature resistance, the electromotive force constant, the motor torque constant (I think this is what you meant by “moment constant” in your list).

You should be able to measure the armature inductance using an LCR meter. You will need to calculate the moment of inertial for your load (listed as “The moment of load” in your list) and the shaft. To calculate the moment of inertia of your shaft, the dimensions of the shaft are available in the motor’s dimension diagram. The shaft is made of stainless steel.

We do not have any specifications for the motor’s viscous friction coefficient, but for most applications, it is probably okay to assume that it will be negligible.

Here is a resource with more information about DC motor modeling.