On Sunday 09 June 2013 20:56:19 andy pugh did opine: > On 10 June 2013 00:20, Gene Heskett <ghesk...@wdtv.com> wrote: > > And this is with Pgain > > > > at about 40, but there is a speed instability, an almost random 50 rpm > > wandering that doesn't go away if I turn off the pwm dither, > > Any PID tuning for a nonlinear system is likely to be a compromise. > > The lincurve module is actually modelled on the type of structure we > use at work to control nonlinear systems. Typically the P, I and D > terms are the output of such a lookup table. > (Which is why, rather unusually, that module has IO pins as well as > outputs). > > So, rather than setting up a 12-entry linearisation curve, you could > try a 3-entry curve to provide the P-term for your system.
That Andy, would need a lot better man page description than what I can 'read between the lines' and pull out. Probably my fault, but lots of our man pages are wanting in that dept. The commandment to make it fit on one monitor screen results at best in very limited descriptions, or so it seems to me. Thinking back on the charge pump based tachometer I used for a speedometer for several years, about 125k miles on that car, I went looking for a 'pfmgen' module, but found none in our 'hal songs' list. If I could find that old schematic & bring it forward 50 years with modern parts, it would make an extremely linear conversion for spindle speed controlling. With modern op-amps, that circuit could easily be a .001% accuracy freq to voltage converter. With 1st generation npn transistors, it was easily 1% accurate. But that particular Radio Craft, or maybe Popular Electronics magazine it was in has I suspect, had the last extant copy recycled into butt wipe by now. Newer, isn't always better. I even, for about 20 minutes, tried to learn what the pwmgen module might be able to do in the PDM mode, but it seemed even harder to control then. The man page tells you how to put it in that mode, but leaves you on your own to determine how it actually works. Having a pfmgen module available might encourage the hardware folks to design a controller interface for it. That would turn any non-linearities found into something we could squarely blame on the motor controller interface. Google finds the LM2907 as being a suitable one chip solution. So all we really need is the pfmgen module. Hint... Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> I have always noticed that whenever a radical takes to Imperialism, he catches it in a very acute form. -- Winston Churchill, 1903 A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
