Does anybody here know if there's a name for the "ordinary" root locus
plot that one gets dragged through in control engineering school? I
mean the one where you have the sum of a polynomial plus a polynomial
times a constant, i.e. it's linear in the parameter being varied.

Just "root locus" plot won't do, because you can have a polynomial that isn't linear in the parameter and make a perfectly nice little plot, you just can't flog the subject endlessly until your students can draw plots by hand in their sleep for systems with 10 poles and 5 zeros or whatever other perverse variations your sadistic mind can dream up.

And yes, almost nobody uses them in control design. I'm presenting them because it's a handy way to understand certain compensation schemes and because its a very powerful way of visualizing what happens to your system stability when you vary some parameter.

Just "root locus" plot won't do, because you can have a polynomial that isn't linear in the parameter and make a perfectly nice little plot, you just can't flog the subject endlessly until your students can draw plots by hand in their sleep for systems with 10 poles and 5 zeros or whatever other perverse variations your sadistic mind can dream up.

And yes, almost nobody uses them in control design. I'm presenting them because it's a handy way to understand certain compensation schemes and because its a very powerful way of visualizing what happens to your system stability when you vary some parameter.

--

Tim Wescott

Wescott Design Services

Tim Wescott

Wescott Design Services

Click to see the full signature.