Robot Motor Factor (RMF)

[lanamor]

I'm reading over Admin's robot dynamics tutorial and I see his RMF section. The concept seems pretty straight forward but I'm no math wiz so I was wondering if I could get an accuracy check on my understanding.

The motor http://www.robotmarketplace.com/products/ML-50.html would have a RMF of 43?

I do use the max efficiency stat and not the stall torque correct? I assume the max efficiency would be the same as some sort of continues or sustained use stat.

A 10lb robot that moved at walking speed with 2 powered 4" diameter wheels would need a RMF more or less of about 13?

  Are my calculations way off?

[lanamor]

Well that drew a big blank so lets try it this way. How do you calculate/decide what motors to use for your project? Do you have a formula or do you just buy more than enough motor?

[Admin]

I do use the max efficiency stat and not the stall torque correct? I assume the max efficiency would be the same as some sort of continues or sustained use stat.

When you use the RMF calculator it will tell you the Motor Rotation Speed (rpm or rps). Look up the motor datasheet and choose the torque given at that rpm. You'd only use stall torque if rpm was 0

Efficiency is something you can only guess with rough calculations or by measuring it. You have to build the system to measure it, so 75% is a good guess.

A 10lb robot that moved at walking speed with 2 powered 4" diameter wheels would need a RMF more or less of about 13?

  Are my calculations way off?

Yeap you did it right. Of course if that number is too high, you can always reduce acceleration.