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Originally Posted by Hachiban VIII
Okay I'm sure this has been discussed somewhere. I have searched but couldn't find exactly what I wanted...
I recently had a discussion with our team's programming mentor. I told her I had designed our prototype drive train to run at the desired speed when the motors were turning at 50% of their max speed. I did this because I figured at this point speed and torque would be highest (proportional to each other).
She said that in reality 75% of max speed is a better number to aim for, and that 50% was just theoretical. I then asked my dad and he said it didn't matter, and that 100% would be just fine.
So who's right? I don't want my drivetrain running at max power constantly just to maintain the desired speed. That would drain the battery. I also don't want to have poor acceleration because there isn't enough power.
Any help?
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I ALWAYS set up motors and gear trains so the desired motor speed is 75% of freespeed. There are some basic reasons for this.
First, no power transmssion system is going to run at freespeed. There is always drag on the system that slows things down even if it is just a little bit. Going with 75% gives you a little margin. Margin is almost always a good thing.
Second, as you stated earlier, you don't want to run things flat out, this is wisdom. See comments about margin above.
Third, running at 75% gives you margin in terms of POWER output. A motor's power output is maximum at 50% of freespeed. At 75% and 25% of freespeed you are getting about 50% power output. If you run at 75% and run into an obstacle that slows you down, you actually begin to get more power from the motor. This extra power might help you blow hrough the obstruction. (hopefully it is not a hard stop on your arm) On the other hand if you run at 50 %, when you slow down you will be getting even less power than you were before.
This holds true for DC electric motors in general. Drive, arm, it doesn't matter.
i hope this helps