Actuator Gain Parameters

X-Series and R-Series Actuators
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FahadRazaKhan
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Joined: Thu May 07, 2020 5:32 am
Location: Japan

Actuator Gain Parameters

Post by FahadRazaKhan » Fri May 15, 2020 2:19 am

Hi,

I am working with Igor and trying to adjust the actuator gains to get better performance. However, I could not find the description of XML gain parameters such as target_lowpass, output_lowpass, min_output, max_output, min_target, max_target, and punch.
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dave_rollinson
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Re: Actuator Gain Parameters

Post by dave_rollinson » Fri May 15, 2020 2:49 pm

Fahad,

There is some info on the various parameters on our docs pages at:
https://docs.hebi.us/core_concepts.html ... ller_gains

Below the diagram and table describing the parameters are some overall tips on tuning controller gains.

If you're not using it already, I highly recommend using Scope while tuning. You can run Scope while your API code is running, or on a separate computer by connecting wirelessly or wired to Igor's network. From Scope you can adjust gains on the fly while the robot is running and plot the various position / velocity / torque readings from the actuators. The PWM plot in Scope can be particularly useful to see how the various controllers are responding and combining during tuning.

Hope that helps get you started. If you have more questions please let us know.

Thanks!
-Dave
FahadRazaKhan
Posts: 13
Joined: Thu May 07, 2020 5:32 am
Location: Japan

Re: Actuator Gain Parameters

Post by FahadRazaKhan » Sat May 16, 2020 3:57 am

Thanks Dave , I really appreciate your support. Another thing I want to be clear about is what is the difference between motor inertia and gear inertia @ motor? Which one needs to be used when you are just concerned about output torque? Also, I could not find the damping/viscous coefficients and static friction constants. Is it possible to provide these constants specifically for the X8-3?
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jwhitman
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Re: Actuator Gain Parameters

Post by jwhitman » Wed Jun 03, 2020 1:01 pm

As per the damping/viscous coefficients and static friction constants, in my experience they vary between modules even of the same type, and can change over time as they get dirty or worn in. I think its also impacted by really small tolerances in the gears, which change as they wear down. I've seen this to be also true for other geared actuators, so its not just the Hebi modules where this is a problem.
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