paper: Servo Power Worksheet

[JamesTerm]

Originally Posted by apalrd

Could you possibly add a note that stall torque * free speed is NOT power, even though that's the formula the FRC rules require?

Actual power is torque * speed @ a given operating point. The point of peak power for a brushed DC motor is around 1/2 speed (1/2 torque as well, since the curves are linear), so the actual mechanical power will be 1/4 of the "servo rated power" using the FRC specified formula.

I don't know why FRC specifies the formula they do, it's wrong.


I do like the worksheet, though.

I realize that I am 3 years late to reply to this, but this is where the rule stands today:

PWM COTS servos with a maximum power rating of 4W each at 6VDC
Per the Servo Industry, Servo Max Power Rating = (Stall Torque) X (No Load Speed)

I don't know what "No Load Speed" means... I have not looked at previous years game manuals yet, but wonder if this issue was ever addressed.

[GeeTwo]

Originally Posted by JamesTerm

I don't know what "No Load Speed" means... I have not looked at previous years game manuals yet, but wonder if this issue was ever addressed.

No Load speed for a servo is the same as "free speed" for a motor - the speed that it moves when there is no load (other than the internal friction and inertia of the motor and gearing). Another way of viewing this is as zero output torque (all of the torque of the motor has been used up in friction). As was noted earlier, if you assume that the torque and speed scale in an inverse linear fashion (usually a decent approximation), the peak mechanical power output is at one-half of the no load speed, and one-half of the stall torque, which is one-quarter of the max power rating.

[JamesTerm]

Ah... no load as in... "NO" load... rather than no as in No. (an abbreviation for number). Got it... thanks.