On Tue, Mar 9, 2010 at 12:15 PM, Torsten Dreyer wrote:
> Hi,
>
> I am about to commit a change that adds anti windup logic to the pi-simple-
> controller (FGPISimpleController) which currently lacks such functionality.
>
> The FGPIDController has some anti windup logic but that controller does not
> suit very well for some solutions and one might (I do) want to use the pi-
> simple-controller instead, if this just had some anti windup.
>
> My question is: should I add a switch to make the pi-simple-controller
> behave
> like it currently does, e.g. add something like
> <anti-windup>true</anti-windup>
> and default that switch to 'false'?
> This should be a good idea if some autopilots relied on wound up
> PISimpleController. Or is it oversized backwards-compatibility?
> I can't imagine a single case where wind-up is a good idea - but who
> knows...
>
> Comments?
> Torsten
>
> BTW. the patch is really simple:
> double output = prop_comp + int_sum;
> - output = clamp( output );
> - set_output_value( output );
> + double clamped_output = clamp( output );
> + if( output != clamped_output ) // anti-windup
> + int_sum = clamped_output - prop_comp;
> +
> + set_output_value( clamped_output );
>
Speaking as the author of the original PISimpleController code I think some
anti-windup logic would be a good additive feature. I don't think we would
need a switch to maintain the old behavior (unless we want to demonstrate to
someone why anti-windup is a good idea ... but in that case, the switch
should be to turn it off, not turn it on.)
Another thing that would be possibly interesting is the addition of a D
component which I never included.
Generally I use the more advanced PID controller for everything except P
only controllers.
Regards,
Curt.
--
Curtis Olson: http://baron.flightgear.org/~curt/
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