On Saturday, January 29, 2011 04:22:51 pm Igor Chudov did opine: > On Sat, Jan 29, 2011 at 8:50 AM, Peter C. Wallace <[email protected]> wrote: > > On Sat, 29 Jan 2011, Igor Chudov wrote: > > > Date: Sat, 29 Jan 2011 07:43:42 -0600 > > > From: Igor Chudov <[email protected]> > > > Reply-To: "Enhanced Machine Controller (EMC)" > > > > > > <[email protected]> > > > > > > To: "Enhanced Machine Controller (EMC)" > > > <[email protected] > > > > > > Subject: [Emc-users] Jerky 4th axis motor rotor movement > > > > > > I am working on getting 4th axis to work. While it does move as > > > > commanded, > > > > > it does so in a visibly jerky way. > > > > > > At first I thought that it was mechanical issue inside the rotary > > > table, such as rust, poor gear meshing, eccentricity etc. > > > > > > I took off the motor and even the lovejoy coupling. The motor, with > > > the attached resolver etc, is now completely alone, lying on a foam > > > pad on > > > > the > > > > > floor. > > > > > > The way this system works is that the motor has a little tiny > > > toothed > > > > belt > > > > > going to the resolver, wires from resolver go into "Resolver to > > > > Quadrature > > > > > Encoder Converter", and from there into PPMC as an input. > > > > > > The bad news is that even without anything on the shaft, it still > > > moves > > > > in a > > > > > jerky way. > > > > > > What I mean by this is not just vibration, but the fact that it > > > > periodically > > > > > accelerates and decelerates.FASTER-slower-FASTER-slower etc. > > > > > > This shakes the whole motor as it moves. > > > > > > I have a feeling that acceleration happen at predictable angles of > > > the > > > > motor > > > > > shaft. It is not just some random vibration from a poorly tuned > > > feedback loop. I think that it turns faster in some quadrants and > > > slower in some other quadrants. > > > > > > I know several facts: > > > > > > 1) If I apply a constant voltage to the motor, from a DC power > > > supply, > > > > the > > > > > motor turns smoothly like a clock. > > > 2) I believe that at least over a whole number of turns, the > > > resolver is accurate. Say, if I command the RT to move by 360 > > > degrees, it does move > > > > by > > > > > 360 degrees exactly and ends up at the perfect mark./ > > > 3) If I try to apply force to deflect motor shaft, in some positions > > > it > > > > is > > > > > easier to move the shaft in one direction that another. The shaft > > > springs back, since there is a P factor (I and D are 0), but > > > clearly it is harder > > > > to > > > > > turn it in one direction than another. This depends on shaft > > > opsition. > > > > > >> From this, I conclude that this is a feedback based issue, such as > > >> the > > > > > > resolver or resolver converter somehow being behind and ahead on > > > > reporting > > > > > its position, which leads to uneven rate of speed. > > > > > > Any ideas? > > > > Sounds like classic quadrature error in the resolver. Are you sure you > > have the resolver wired correctly? > > > > Not sure. I thought so, but I will check again. > > > > > > I would check that the sine and cosine output peak amplitudes are the > > same (peak amplitudes will be 90 degrees of shaft rotation apart for > > a 1X resolver) > > > > a 2 channel Scope is nice for this but if you dont have a scope a DVM > > will do > > What sort of a DVM would work? What about things like Fluke handheld > meters? The frequency is 10 kHz. > > Thanks Peter. > It shouldn't make much difference as log as the shaft is turned slowly enough that the meters a/d circuitry can keep up.
-- 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) <http://tinyurl.com/ddg5bz> This is now. Later is later. ------------------------------------------------------------------------------ Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! Finally, a world-class log management solution at an even better price-free! Download using promo code Free_Logger_4_Dev2Dev. Offer expires February 28th, so secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsight-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
