On Tue, 8 Jan 2013, Viesturs L?cis wrote: > Date: Tue, 8 Jan 2013 13:35:28 +0200 > From: "[UTF-8] Viesturs L?cis" <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: [Emc-users] LinuxCNC craziness > > Hello! > > Today I came back to client's site to finish the plasma table and now > I am desperate to understand, what is wrong with this machine. > > I had control box and motors with me at home, where I had plugged > motors directly in control box and got everything working 1st or 2nd > of january. All the following days I turned the control box every day > to check, if motors behave properly. And they did - I could jog them, > they moved ok, when I told to home all joints (since there were no > homeswitches attached, I always interrupted that procedure with Esc > key). Everything seemed just fine. > > Today as I arrived, I plugged all the cables in control box and > plugged motors to their cables, so now the difference is that motors > are not plugged directly in control box, but through their cables, > which are from 7 to 11 m long. > And now I see several things that I completely do not understand: > 1) if I set bldc value positive, motor will turn sometimes positive, > sometimes negative direction. This is changing as I restart LinuxCNC > application. I _do not_ change any settings between these attempts to > run LinuxCNC, so I have no explanation for this; > 2) when motion is enabled, mostly encoder 0, but very few times > encoder 1 will report a positive velocity, which corresponds to more > than 10 motor revolutions per second, but: > a) motor _is not_ moving; > b) it drops to 0 as soon as I set _any_ bldc value to a non-zero > number, for example, +0.01 or -0.01; > c) machine frame is grounded, control box case is grounded, signal > cable shields are gounded; > 3) One motor does not turn as good as I would like, so I tried to > adjust lead-angle value. As I change it back and forth, trying one > value, then another and then returning to previous one, each time it > will behave differently with one and the same value - in one case it > can go up to 200 mm/sec with bldc.value = 0.7 and -80 mm/sec and > trigger overcurrent on 7i39 with bldc.value -0.70 and next time it can > do completely opposite. I am playing with values in range of 90 to 100 > degrees and increment them by 2. > > Does anyone have any idea, what is all this about? > > -- > Viesturs
Sounds like you have a severe noise issues, which is not terribly surprising with 11M motor cables. First thing I would do would be to add a common mode choke around the U/V/W Motor wires at each 7I39 end of the motor cable: Laird-Signal Integrity Products 28B1122-100 is a good choice here. Another thing to do is increase the encoder filtering if you have not already done this: See the hostmot2 manual page, raw mode section (you need to enable raw-mode) Don't know if there's a HAL example of using raw-write but here's an approximation: setp hm2_[HOSTMOT2](BOARD).0.write-address 13312 # (0x3400) setp hm2_[HOSTMOT2](BOARD).0.write-data 8 (divide/10) setp hm2_[HOSTMOT2](BOARD).0.write-strobe TRUE This will change the filter time constant for all encoders from 300 nS to 3 usec (assumimg the filter bit is set in the hal file hal) This will lower the maximum count rate from 6.66 MHz to 660 Khz, so you need to make sure this is still fast enough at your maximum speed Other things Shielded motor wires shielded encoder cables (differential signals on twisted pairs) shield terminated at 7I39 (differential adapter) end and open at motor end > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > ------------------------------------------------------------------------------ > Master SQL Server Development, Administration, T-SQL, SSAS, SSIS, SSRS > and more. Get SQL Server skills now (including 2012) with LearnDevNow - > 200+ hours of step-by-step video tutorials by Microsoft MVPs and experts. > SALE $99.99 this month only - learn more at: > http://p.sf.net/sfu/learnmore_122512 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics ------------------------------------------------------------------------------ Master SQL Server Development, Administration, T-SQL, SSAS, SSIS, SSRS and more. Get SQL Server skills now (including 2012) with LearnDevNow - 200+ hours of step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only - learn more at: http://p.sf.net/sfu/learnmore_122512 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
