Hi Stuart, Do you have some part numbers for these drives?
----- Original Message ----- From: "Stuart Stevenson" <stus...@gmail.com> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Wednesday, September 15, 2010 3:22 PM Subject: Re: [Emc-users] simple servo amplifier > On Wed, Sep 15, 2010 at 12:07 AM, Jon Elson <el...@pico-systems.com> > wrote: > >> Stuart Stevenson wrote: >> > Gentlemen, >> > The servo amps on the Enshu have different accel/decel shapes. The >> > PID.output trace has a sharp corner to it. The trace raises a little >> > and >> > then turns almost straight up. The decel trace is MUCH more rounded. >> > Does >> > this sound like an amplifier problem? >> > >> Not necessarily. It may just be a symptom of friction. During >> acceleration, the motor >> is not only accelerating the mass, it is also fighting the friction of >> the slide, both have the same >> mathematical sign. On deceleration, it must fight the mass of the >> table, which exactly >> mirrors the accel condition, BUT the friction is now of opposite sign, >> and is HELPING >> the deceleration. So, you can't perfectly optimize FF2 to cover both >> conditions. >> > once again pictures trump words - my explanation was not correct as you > will > see > the acce/decel look the same but the beginning and ending phases of each > are > not balanced > and the trace is the axis following error not the PID.output - I should > have > said PID.error and axis following error - I had looked at the output trace > so that must have been stuck in one of the holes in my head > >> >> I wouldn't look at the PID.output, but just at following error, and set >> FF2 to balance >> the error of the two situations. If you have large discontinuities at >> the accel/decel >> time, then you may have to reduce acceleration in the .ini file, you may >> be asking for >> too much accel. >> > I am thinking it would be possible to convert this Fanuc amp to a >> simple >> > amp by fooling the tach feedback. This servo amp accepts the encoder >> > feedback on two terminals and converts these two signals into a tach >> voltage >> > for comparison to the velocity signal. Would it be possible to do one >> > of >> two >> > things to convert it to a simple amp with no tuning to the motor. >> > I think the best way would be to find where the chip ouputs the >> matching >> > tach voltage and connect the velocity signal voltage at that point. The >> amp >> > would think the motor is following the signal perfectly and require no >> > output adjustment. >> > >> Well, I happen to think a real velocity servo amp is just about >> unbeatable. It does require >> some more tuning than some other systems, but can be expected to perform >> better under >> a wide variety of conditions. >> > so far in my world a Fanuc servo system is about as real as you can get > I don't think it is any better than what EMC can do and maybe not as good > and certainly not (by me) as adjustable. > I have no way of adjusting any parameters on these amps. There are some > pots > and jumpers. > Does anyone know how to change the parameters without using a Fanuc > control? > Does anyone have the information explaining the jumpers and pots? I have > some information about the pots but nothing about the jumpers. > > >> > or >> > I could use an ADC to accept the velocity signal and generate an >> encoder >> > pulse to match what would be seen as feedback from the motor. >> > Either way this feedback would be perfectly matched to the input. >> > EMC2's tuning would then have complete and total control of the servo >> > motor (axis motion) >> Not sure how an analog-digital converter would be used here. More >> likely, you'd need >> > > This Fanuc servo system has a servo amp that accepts: > an analog velocity signal from the control > digital signals to close the loop from the motor - an encoder on the motor > sends pulses to the servo and the control > The Fanuc servo motor has no tach. > > I propose using an ADC to convert the analog velocity signal to a pseudo > encoder pulse to replace the motor feedback. > I think this would remove the tuning from the servo amp as the amp would > see > the motor as perfectly following the velocity signal at all times. > Even better would be to shunt the velocity signal directly to the tach > signal the chip on the control generates. > Even better would be to disable the internal tuning by shifting jumpers. > Maybe (I am not sure) better would be to have a procedure to tune the amps > and motors as a unit. This may be better but I don't like it as well as > any > of my other thoughts. > > a digital to analog converter to produce the simulated tach signal. >> But, most servo amps >> can be converted to torque mode, usually by pulling a jumper that >> bypasses the >> velocity error amp. But, I still feel that a velocity servo with a real >> tach should work >> well, and you need a VERY high resolution encoder to move smoothly >> without a tach. >> >> Maybe you could post the trace you are concerned about. >> > pictures are here > http://www.mpm1.com:8080/machines/enshu > > there are pictures of all three axes both positive and negative moves > thanks > Stuart > > -- > dos centavos > ------------------------------------------------------------------------------ > Start uncovering the many advantages of virtual appliances > and start using them to simplify application deployment and > accelerate your shift to cloud computing. > http://p.sf.net/sfu/novell-sfdev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -------------------------------------------------------------------------------- No virus found in this incoming message. 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