Re: control law modification

Peter Nachtwey wrote:

Bo wrote:

Y(s) = C/s[s^2+4.2s+9] = C/s(s+ (-2.1+j2.1))(s + (-2.1-j2.1));


This is a type 1 under damped two pole system. Think of pushing a
spring with a mass on the other end. This could be a simple model for
a hydraulic system. This system will not go back to 0 because it is a
type 1 system or position system. Position systems stay where you
leave them if there is no other force applied. Velocity systems and
temperature systems will go to 0 or ambient. These are type 0 systems.

-- snip --
Peter Nachtwey

Your conclusions are correct, but sadly you're backwards on your type numbers. From "Design of Feedback Control Systems" by Hostetter, Sevant and Stefani: the system type is the number of s = 0 numerator roots in the error transmittance.

One generally induces a certain type number by piling on the integrators in the controllers, although sometimes the plant will give you one or two for free.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
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