On Sat, 5 Sep 2015 20:47:54 -0700 (PDT), liangxiaoxiao138@gmail.com
wrote:

? 2000?8?2???? UTC+8??3:00:00?John Becich???

I've got a small DC brush-type gear motor, and I don't know the moment of
inertia. I'm trying to compose feedback control system equations.

I have measured the MOI of a flywheel that is about a foot in diameter, by >> setting it up in a torsional pendulum and timing its period of oscillation. >> This period was successfully compared to the period of oscillation of
another mechanical object with known MOI. Unfortunately, I doubt that there >> is any such simple method to measure the MOI of the gear motor.

...

Torsional pendulum was the technique many years ago, but now I think
MOI is calculated using cad software.

d. young

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在 2000年8月2日星期三 UTC+8下午3:00:00，John Becich写道：

I've got a small DC brush-type gear motor, and I don't know the moment of inertia. I'm trying to compose feedback control system equations.

I have measured the MOI of a flywheel that is about a foot in diameter, by setting it up in a torsional pendulum and timing its period of oscillation. This period was successfully compared to the period of oscillation of
another mechanical object with known MOI. Unfortunately, I doubt that there is any such simple method to measure the MOI of the gear motor.

You can assume that I know the internal DC resistance, "R," and internal inductance, "L," of this motor. I have instruments such as oscilloscope, memory o-scope, and spectrum analyzer, as well as pulse generator and servo amplifier. Is there some technique for measuring the MOI with these instruments? I would thing I could set up some kind of resonance and measure, electonically, the frequency of resonance, etc. Of course, I'd
have to know WHICH resonance was pertinent to the MOI!

Do I have to consider the MOI of the motor armature and all the gears in the gear train? Ouch!

This gear motor is about the size of an adult human hand, and weighs roughly three pounds. Output with no load is 6 RPM @ 24VDC. Current draw would
then be 0.15 amps.

Meanwhile, I'll try to contact the manufacturer in the hope it can tell me what I need to know. That's the non-technical solution!

Thanks,
John

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