Ciao Luca When you create static gains (e. g. sys = tf (12) or sys = ss (17)) with control-oo, sampling time is set to -1, which means "unspecified". This way, you can connect them conveniently with other systems (e.g. sys2 = tf (1, [1, 1]) or sys3 = ss (-1, 1, 1, 0, 0.1)), which are either continuous or discrete. This feature is also necessary to allow expressions like Q = 1 + L, where L is the open loop and Q is the return difference.
Stable poles have real parts < 0 (continuous) or are within the unit circle (discrete). When you set tol greater than zero, barely stable poles (possibly due to numerical "noise") are regarded as unstable as well. Regards, Lukas Reichlin BTW: You may encounter the expression digital = ! isct (sys) in my code. It means that static gains are treated as continuous systems. Note that it is not the same as digital = isdt (sys), where static gains would be treated as discrete systems. > Hi, Lukas. > > > Some comments. > > > isct > ---- > > Why in isct [0] you check > ltisys.tsam == -1 > ? > > > isct/isdt > ---------- > > Did you consider "empty models and static gains" [2] in isct [0] and > isdt [1]? > > > isstable > ---------- > > Why is "tol" argument needed in lti/isstable [3]? > > > > Cheers, > Luca Favatella > > > > > [0] > http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/extra/control-oo/inst/%40lti/isct.m?revision=6325 > [1] > http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/extra/control-oo/inst/%40lti/isdt.m?revision=6325 > > [2] > http://www.mathworks.com/access/helpdesk/help/toolbox/control/ref/isct.html > > > [3] > http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/extra/control-oo/inst/%40lti/isstable.m?revision=6325 > > ------------------------------------------------------------------------------ > Come build with us! The BlackBerry(R) Developer Conference in SF, CA > is the only developer event you need to attend this year. Jumpstart > your > developing skills, take BlackBerry mobile applications to market and > stay > ahead of the curve. Join us from November 9 - 12, 2009. Register now! > http://p.sf.net/sfu/devconference > _______________________________________________ > Octave-dev mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/octave-dev ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Octave-dev mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/octave-dev
