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How to configure feed_backward in PID

Posted: Fri Oct 30, 2020 6:26 am
by husch
In the iROS HEBI tutorial of motion control, it is mentioned that when using strategy 4, we can disable effort feedback in effort PID, as shown in the graph attached.
But how do we disable it? There is no configuration for feed_backward in gain configuration, either in xml format or in Scope tool.
Thanks a lot :-)
BTW, the tutorial in iROS is very helpful.

<group_gains>
<control_strategy>4</control_strategy>
<effort>
<kp>0.25</kp>
<ki>0</ki>
<kd>0.001</kd>
<feed_forward>1</feed_forward>
<dead_zone>0</dead_zone>
<i_clamp>0.25</i_clamp>
<punch>-0</punch>
<min_target>-10</min_target>
<max_target>10</max_target>
<target_lowpass>1</target_lowpass>
<min_output>-1</min_output>
<max_output>1</max_output>
<output_lowpass>0.9</output_lowpass>
<d_on_error>0</d_on_error>
</effort>
</group_gains>

Re: How to configure feed_backward in PID

Posted: Fri Oct 30, 2020 8:52 am
by florian_enner
You can "disable" the effort feedback portion by only using the FeedForward term (=1) and setting Kp,Kd,Ki to zero. This way the torque controller serves as a unit conversion from actuator specific units to Nm/rad.

Re: How to configure feed_backward in PID

Posted: Fri Oct 30, 2020 10:47 am
by husch
Yes, of course!! It makes sense.
Thanks a lot :-)