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? 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 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ 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
