For embedded closed-loop control systems. http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html Comments welcome (particularly if I made some stupid mistake). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Article: Measuring Frequency Response
Started by ●March 25, 2005
Reply by ●March 25, 20052005-03-25
Tim Wescott wrote:> For embedded closed-loop control systems. > > http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > > Comments welcome (particularly if I made some stupid mistake).Hi Tim, Yummy, thanks. -- _______________________________________________________________________ Christopher R. Carlen Principal Laser/Optical Technologist Sandia National Laboratories CA USA crcarleRemoveThis@BOGUSsandia.gov NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
Reply by ●March 25, 20052005-03-25
"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message news:1148ve9mlhq6uf4@corp.supernews.com...> For embedded closed-loop control systems. > > http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > > Comments welcome (particularly if I made some stupid mistake). > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.comYes, your 'stupid mistake' was.... I don't know what the fuck you think you're on about. Now, is that my problem? DNA
Reply by ●March 25, 20052005-03-25
in article 1148ve9mlhq6uf4@corp.supernews.com, Tim Wescott at tim@wescottnospamdesign.com wrote on 03/25/2005 16:08:> For embedded closed-loop control systems. > > http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > > Comments welcome (particularly if I made some stupid mistake).just a first impression, i can't tell from the body of the article, but it appears in the code that you are doing swept frequency measurements. are you, or am i reading the code wrong ("startF", "stopF"). if you are doing *linearly* swept frequency measurements and your sweep rate is not slow enough, you might want to review: http://groups-beta.google.com/group/comp.dsp/msg/0763020cf20587c3 it's just to show what the apparent frequency response is and then how to correct for any deterministic error. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●March 25, 20052005-03-25
On Fri, 25 Mar 2005 13:08:25 -0800, Tim Wescott <tim@wescottnospamdesign.com> wrote:>For embedded closed-loop control systems. > >http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > >Comments welcome (particularly if I made some stupid mistake).Tim, I just did a quick read and it looks like you've covered the topic pretty well. Not much I'd add, actually. Well organized, stated pretty simply, well explained. I think you could expect a red or blue ribbon at the science fair. ;) Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●March 25, 20052005-03-25
robert bristow-johnson wrote:> in article 1148ve9mlhq6uf4@corp.supernews.com, Tim Wescott at > tim@wescottnospamdesign.com wrote on 03/25/2005 16:08: > > >>For embedded closed-loop control systems. >> >>http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html >> >>Comments welcome (particularly if I made some stupid mistake). > > > just a first impression, i can't tell from the body of the article, but it > appears in the code that you are doing swept frequency measurements. are > you, or am i reading the code wrong ("startF", "stopF").Note to self: make sure that it's clear that I'm doing swept-sine measurements.> > if you are doing *linearly* swept frequency measurements and your sweep rate > is not slow enough, you might want to review: > > http://groups-beta.google.com/group/comp.dsp/msg/0763020cf20587c3 > > it's just to show what the apparent frequency response is and then how to > correct for any deterministic error. >The sweep is exponential, and some extremely vague handwaving in there about making it slow enough -- I should think about how to clarify that. Generally the method as I use it, with the exponential sweep, moves things slowly enough that the transient response doesn't cause a great deal of difficulty -- particularly if you have the system operating in closed-loop, which generally causes the transient to settle out much faster than the initial sine wave. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●March 25, 20052005-03-25
holy shit! have we caught another troll? (geez i hope not. my spray can of Troll-Away is almost empty.) in article g201e.8099$ME3.575@newsfe1-gui.ntli.net, Genome at ilike_spam@yahoo.co.uk wrote on 03/25/2005 17:13:> > "Tim Wescott" <tim@wescottnospamdesign.com> wrote in message > news:1148ve9mlhq6uf4@corp.supernews.com... >> For embedded closed-loop control systems. >> >> http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html >> >> Comments welcome (particularly if I made some stupid mistake). >> >> -- >> >> Tim Wescott >> Wescott Design Services >> http://www.wescottdesign.com > > Yes, your 'stupid mistake' was.... > > I don't know what the fuck you think you're on about. > > Now, is that my problem? > > DNA > >-- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●March 25, 20052005-03-25
Tim Wescott wrote:> For embedded closed-loop control systems. > > http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > > Comments welcome (particularly if I made some stupid mistake). > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.comHi, you may want to consider adding a brief discussion about interpreting the results. For example the amount and location of peaking in the closed loop response can give a rough idea of the loop bandwidth and the stability margin ( From the closed loop peaking, can you tell the gain and phase margin separately or not??). Also I'm sure you are familiar with Venabale which uses some similar techniques. http://www.venable.biz/ Mark
Reply by ●March 25, 20052005-03-25
"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message news:1148ve9mlhq6uf4@corp.supernews.com...> For embedded closed-loop control systems. > > http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > > Comments welcome (particularly if I made some stupid mistake). > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.comI think you may have a typo in your discussion of eq. 7. You refer to a �"Pi/2 term" which I don't see.
Reply by ●March 26, 20052005-03-26
In article <1148ve9mlhq6uf4@corp.supernews.com>, Tim Wescott <tim@wescottnospamdesign.com> wrote:>For embedded closed-loop control systems. > >http://www.wescottdesign.com/articles/FreqMeas/freq_meas.html > >Comments welcome (particularly if I made some stupid mistake).Figure 5 etc would be better if the Right hand scale showed the 45, 90 and 180 degree points directly. The font on the equations is a bit small. -- -- kensmith@rahul.net forging knowledge
