How To Calculate Rms Speed

How to Calculate RMS Torque

Block and Tackle Series Volume iii – How to Calculate RMS Torque

Question:

How exercise I calculate RMS (Root Mean Square) Torque for a given axis motion contour in my application?

Respond:

In our last Block and Tackle posting, we touched on operating a motor in a hotter ambient temperature. For this posting, we have a wait at the Root Mean Foursquare (RMS) Torque and why it is of import. Typically an axes' motion profile is broken upward into multiple segments, each segment is found to require a specific torque for a specific amount of time to complete the desired move. For example, this tin include torque required to accelerate, traverse (confronting an external strength and/or friction), decelerate, and dwell. Each of these segments affects the corporeality of heating the motor experiences and thus the equivalent steady state continuous requirement utilized to select the right motor. The RMS Torque adding considers non only the amount of torque, but also the duration of that torque (by segment). Our example below illustrates how to summate Trms of your motion profile.

The below movement profile would be broken up into eight (8) unlike segments, each with a required torque T_ten and time t_x.

Motion Profile with Segmentation

To calculate Trms, use this equation:

RMS Torque Formula

Where T_i = torque required past and during segment i, and t_i = time elapsing (t₁-t₀) of segment 1, etc.. Note the additional torque required by the motor to over come some external/thrust force (greater than friction alone) during segment ii, and the lack of this required torque during the dwell segment iv and viii.

Going back to the example motion profile above and the chart of that motility profile:

Motion Profile Table with Segmentation

Therefore, if you lot do the math – and we volition spare y'all writing this into a very long equation, the result is:

Trms = RMS Example = ii.74 lb-ft or three.715_Nm (1.35582_Nm/lb-ft.)

About the Author

This blog was a collaborative endeavor amid a team of motion and automation experts here at Kollmorgen, including engineers, customer service and design experts. Wherever you are in your project, we're here to help.

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