Functionalities of HardLimiter and Limiter

[jinningwang]

@cuihantao
Hi Hantao,

I noticed that the doc of HardLimiter said it is an alias of Limiter, and I'm curious that whether the HardLimiter can actually limit a variable in ANDES? Since Limiter cannot do that, I don't think HardLimiter can do that?

This will affect the PIAWHardLimit since the output is added with a Limiter. Does it mean the output may not be actually limited?
If this is true maybe we should replace the output Limiter with an AntiWindup?

Regards,
Jinning

[cuihantao]

HardLimiter and Limiter do not actually limit the variables. They process the input variables and spits out the flags, zi, zl, and zu. It is up to the user to construct the equation, making use of the flags.

Use GainLimiter if you want the outputs to be pegged at limits when hit.

For PIAWHardLimit, the output is its y variable, which already uses the limiter output flags.

[jinningwang]

Thanks for your reply.

Then I have another question: will AntiWindup realize the function of 'actual limit variables'? If so we don't need to build the equations with Limiter flags.

Regards,
Jinning

[cuihantao]

Yes, AntiWindup is a special case where the variables are set in TDS. It can not be set through its own equation because it depends on the equation.

Search for system.antiwindup in TDS.py.

[jinningwang]

Thanks, I'll take a look at it.

Regards,
Jinning

[cuihantao]

Docs improved. Thanks! @jinningwang