On Sunday 09 June 2013 22:10:05 Kent A. Reed did opine: > On 6/9/2013 9:08 PM, Jon Elson wrote: > > Gene Heskett wrote: > >> Looking at its voltage output, with the motor disabled so there is no > >> feedback,off = 0.125 volts > >> click fwd button= 0.382 diff = 0.257 > >> click + button = 0.942 diff = 0.560 > >> click + again = 1.584 diff = 0.642 > >> click + again = 2.302 diff = 0.718 > >> click + again = 3.094 diff = 0.792 > >> click + again = 3.970 diff = 0.876 > >> click + again = 4.940 diff = 0.970 > >> click + again = 6.04 diff = 1.100 > >> click + again = 7.33 diff = 1.29 > >> click + again = 8.88 diff = 1.55 > >> click + again = 9.90 diff = 1.02 > > > > URK! It isn't even monotonic! That is harder to fix with a > > piecewise-linear > > interpolation. (Some simplistic codes won't handle that.) > > Ummm, I expect you mean the differences aren't monotonic, Jon. > > Actually, plotting Gene's data as a set of twelve points X, V where X is > the number of clicks, I get a pretty decent graph --- looks like a > parabolic curve opening upward, with a bit of a burble in the next to > last point (or last two depending on how you look at data). > > Trying a second-order curve fit (using the free tool simfit, but there's > lots of other tools) got me a decent looking result with a plot of > residuals that also gives the impression that the last two points are > questionable compared to the rest. > > I don't chose simply to post the results because I don't believe any > single experimental run is sufficient. Repeat this experiment three or > more times, Gene, so we can begin to get an idea of the quality of the > data and then we can talk. > > Regards, > Kent
I likely will, but need a decent temp, dry day to do it. And looking at the radar, thats definitely NOT on the menu for the next day, maybe 2. As a generalized solution to the non-linearities that appear to be inherent in a PWM system with real hardware, what do you think of a digital PFMGEN, then using something like an LM2907 on the other end of the cable to do the D/A conversion? It seems to me that method, with its potential for sub 1% accuracies, would transfer the majority of the errors found into the motor controller itself. That would require cobbling up something for hal to generate the set pulse width, frequency modulated pulse train, which will have its own granularity problems given the need for an update speed suitable for 1 or 2 rps stuff. Also, I am not done putzing with the c41 as I think I overshot the mark a bit by adjusting a resistor while looking for a near zero volts output when the PWMGEN is off. I have a couple more things to try to restore the low voltage linearity a bit, and to dump a VBe's worth of its output in order to get the zero lockout reset low enough. Today wasn't conducive to productive thinking as it was 90+ in the shop and muggy as heck. Uncomfortable at best. 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> Remember that there is an outside world to see and enjoy. -- Hans Liepmann 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
