RMP220 question about yaw rate discrepancy

RMP 210, 220, 440LE, 440SE, 440 Omni
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ChrisC
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RMP220 question about yaw rate discrepancy

Post by ChrisC » Fri Oct 04, 2013 10:41 am

When trying to send a yaw rate to the RMP, the user defined feedback bitmap(at element 57 of the returned array) returns the target yaw rate to be 3 times greater my desired yaw rate. Is there a reason for that?

sdnalloh
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Re: RMP220 question about yaw rate discrepancy

Post by sdnalloh » Fri Oct 04, 2013 11:25 am

During testing, I found that yaw_rate_target_rps (page 62 of the RMP 440 SE User Manual) quite accurately represented the yaw rate I commanded.

I recommend you check your units and conversions. This feedback variable is in radians/second.

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phussey
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Re: RMP220 question about yaw rate discrepancy

Post by phussey » Mon Oct 07, 2013 1:23 pm

A very important note is that the yaw rate command is normalized to the maximum yaw rate. Meaning the input command is unitless (-1.0...1.0). Since the default max yaw rate is ~3 rad/s; commanding 1.0 would result in a yaw rate of 3.0 rad/s. This is also true for the velocity controller, obviously different scaling. This information can be found in the manual.

I think if it were a conversion issue it would be off by a much larger factor (180/pi = 57.29578), or smaller depending which side of the conversion you're on.
PATRICK HUSSEY
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STANLEY INNOVATION, INC
www.stanleyinnovation.com

Phillip.Wong
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Re: RMP220 question about yaw rate discrepancy

Post by Phillip.Wong » Mon Oct 07, 2013 9:40 pm

Thank you phussey and sdnalloh! Your posts are incredibly helpful.

That was exactly my problem. I wasn't aware of the normalization happening, so now I have excellent control over the yaw rate/angular velocity. After some testing, the velocity inputted isn't normalized/scaled. Its not a problem since I can adjust accordingly, its more of just an observation. However, it could be possible its still an error on my end.

ChrisC
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Re: RMP220 question about yaw rate discrepancy

Post by ChrisC » Wed Oct 09, 2013 11:13 am

Velocity commands are also normalized against the configurable parameters. Have you had a chance to review the motion command structure which is defined on page 39 of the User Manual - RMP 440 SE?

If the defaults were used during installation the document will be located in the following directory: C:\Program Files\Segway\RMP_Applications\Documentation

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