How to maximize the output torque of a motor

VEX V5 General Discussion
1

For hanging, we want the maximum torque output from a motor. According to the picture below, how to maximize the output torque?

set_velocity(100, PERCERNT)
set_velocity(50, PERCENT)
set_velocity(50, RPM) # red cartridge
set_velocity(11, VOLT)

image
image982Ă—542 35.4 KB

2

A motor puts out its maximum torque when it is stalled (i.e., trying to turn but failing), just because of the physics of how motors work. The blue Torque line in your graph shows that the torque of Vex motors is essentially constant up to about 50% of maximum RPM, because the Vex motors have controllers that limit themselves to about half the maximum torque to prevent overheating.

When your robot is trying to hang, the motor will put out as much torque as it needs to to move as instructed, up to that maximum torque, or any smaller value you set with Motor.setMaxTorque(). You can make sure you’re getting the maximum torque possible using “hangMotor.setMaxTorque(100, percent);” but I’m pretty sure it defaults to 100 percent.

Reducing the velocity as you’re trying to do doesn’t help. If you tell it to spin at 100% velocity, it will put out as much torque as it can within those limits, and if that’s not enough to get it up to 100% it will go slower just because that’s what happens when you don’t have enough torque.

5 Likes
3

First, there’s probably not much difference between 100% velocity and 11 volts if the motor’s loaded beyond its capabilities… in either case you will hit safety limits.

That said… I’ve seen some stuttering when motors are turning extremely slow at high loads with a PWM control setup. So, in that case, 11 volts might be better.

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4

Thank you both very much!

After reducing some weight, now it can barely hang. It is interesting to notice that it works for one port but not another. I suspect that the two ports have different maximum voltage for some reason. As turbodog indicated, perhaps it is safer to set 11 volts.

5

By the way, what is the difference between

set_velocity(100, PERCERNT)

and

set_velocity(11, VOLT)

?

6

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