Do Gearheads and Encoders Affect DC Motor Inertia and Time Constant?

[etinios]

Hello,

I'm doing my thesis on dc motor position control, using the Simulink's Real Time windows target.The dc motor is Faulhaber 2342024CR(DC micromotor). First of all, I need to simulate the motor so as to have a full simulation of the whole system(motor,servoamplifier). The problem is that the values given by the manufacturer do not correspond to the real ones. Can anyone tell me if the inertia and the time constant of the motor change if the motor is combined with a gearhead and an encoder?The manufacturer says that these values vary but I have found a difference quite big:tm(time constant)=0.006sec(datasheet) and tm=0.028sec(real). Is it possible?How does the inertia change?Thanks you in advance!I am desperate!I cannot find the model:(

 

[tvavanasd]

Can anyone tell me if the inertia and the time constant of the motor change if the motor is combined with a gearhead and an encoder?The manufacturer says that these values vary but I have found a difference quite big:tm(time constant)=0.006sec(datasheet) and tm=0.028sec(real). Is it possible?How does the inertia change?Thanks you in advance!I am desperate!I cannot find the model:(

Yes, inertia is definitely affected by adding a gear reducer and encoder (and additional load if applicable).

Jm = motor inertia

Jsystem (measured at motor shaft) = Jm + Jencoder + Jreducer + Jload / ratio^2

Note that load inertia seen at the reducer input is reduced by the square of the gear ratio.

I expect that the time constant will increase proportionally with inertia.

Consider the system as a whole, not the motor alone.

Found the following from a quick search that you may find interesting:

http://www.control.com/thread/1001363524