On 02/03/2011 02:49 PM, emc-users-requ...@lists.sourceforge.net wrote:
> Les, I thought that friction is not at all proportional to speed?
>
> It is a value that only depends on the direction (sign) of speed, not on the
> value of speed.
>
> Am I mistaken?
If I remember properly, Tormach goes over
On Thu, Feb 03, 2011 at 09:23:17AM -0800, Kirk Wallace wrote:
>
> Here is a link for bearing information:
> http://www.timken.com/en-us/products/Documents/5918_09-09-29.pdf
> http://www.timken.com/en-us/products/Pages/Catalogs.aspx
>
> I found the spindle section especially informative, but goi
Les Newell wrote:
> That would be FF0. Assuming the friction is directly proportional to
> speed then FF0 will increase the output directly proportional to the
> commanded speed. It does mean that it will over compensate a bit while
> accelerating up to speed but that is fine because you need mo
Thinking about it, there are three friction components. Dry friction is
proportional to load (i.e if you put a heavy load on the table it will
be harder to turn). Viscous friction is proportional to speed. Stiction
is the initial resistance to movement and is mainly dependent on how
long the sl
On Thu, Feb 3, 2011 at 2:25 PM, andy pugh wrote:
> On 3 February 2011 19:56, Igor Chudov wrote:
>
> >> Assuming that the input to the PID is position, then I have a feeling
> >> you could get the same effect by using a very large gain on FF1 with a
> >> limit (maxcmdD) set to ever so slightly le
On 3 February 2011 19:56, Igor Chudov wrote:
>> Assuming that the input to the PID is position, then I have a feeling
>> you could get the same effect by using a very large gain on FF1 with a
>> limit (maxcmdD) set to ever so slightly less than the current required
>> to move the table.
> Since
On Thu, 2011-02-03 at 13:09 -0600, Igor Chudov wrote:
... snip
> Anyhow, how hard do you think is it for a C++ programmer to add a friction
> compensation to EMC? Ergo, look at Andy's post from a while ago:
>
> http://www.mail-archive.com/emc-users@lists.sourceforge.net/msg22729.html
>
> It would
On Thu, Feb 3, 2011 at 1:33 PM, andy pugh wrote:
> On 3 February 2011 19:09, Igor Chudov wrote:
>
> > It would appear that friction compensation (let me call it FFF for now)
> is
> > just one more term,
>
> As somebody else said, inverse-deadband ought to do what you want.
> (I have seen a comp
On 3 February 2011 19:09, Igor Chudov wrote:
> It would appear that friction compensation (let me call it FFF for now) is
> just one more term,
As somebody else said, inverse-deadband ought to do what you want.
(I have seen a comp somewhere to do that).
Assuming that the input to the PID is posi
On Thu, Feb 3, 2011 at 1:18 PM, Les Newell wrote:
> That would be FF0. Assuming the friction is directly proportional to
> speed then FF0 will increase the output directly proportional to the
> commanded speed. It does mean that it will over compensate a bit while
> accelerating up to speed but th
That would be FF0. Assuming the friction is directly proportional to
speed then FF0 will increase the output directly proportional to the
commanded speed. It does mean that it will over compensate a bit while
accelerating up to speed but that is fine because you need more power to
accelerate an
On Thu, Feb 3, 2011 at 1:00 PM, Kirk Wallace wrote:
> On Thu, 2011-02-03 at 12:33 -0600, Igor Chudov wrote:
> ... snip
> > Guys! Please! This is _NOT_ sticktion!
> ... snip
>
> Sorry about that. I'm not trying to say it is stiction. I was trying to
> explore ways to prove it isn't or to find a mea
On Thu, 2011-02-03 at 12:33 -0600, Igor Chudov wrote:
... snip
> Guys! Please! This is _NOT_ sticktion!
... snip
Sorry about that. I'm not trying to say it is stiction. I was trying to
explore ways to prove it isn't or to find a means to find the true
nature of the joint dynamics. The frustrating
On Thu, Feb 3, 2011 at 12:21 PM, andy pugh wrote:
> On 3 February 2011 18:12, Kirk Wallace
> wrote:
> >
> > I would look at the maximum motor RPM, decide on an maximum joint rate,
> > then set up a pulley ratio to match, so that the motor has the maximum
> > mechanical advantage.
>
> However, th
On Thu, Feb 3, 2011 at 12:12 PM, Kirk Wallace
wrote:
> On Thu, 2011-02-03 at 15:16 +0200, Slavko Kocjancic wrote:
> > That's not problem of friction at all!.
> >
> > The worst you have is 'sticky' axis.
> > That means you need a lot more power to start to move axis and when
> already
> > moving th
On 3 February 2011 18:12, Kirk Wallace wrote:
>
> I would look at the maximum motor RPM, decide on an maximum joint rate,
> then set up a pulley ratio to match, so that the motor has the maximum
> mechanical advantage.
However, this is a commercially-made CNC rotary table. You would have
to assum
On Thu, 2011-02-03 at 15:16 +0200, Slavko Kocjancic wrote:
> That's not problem of friction at all!.
>
> The worst you have is 'sticky' axis.
> That means you need a lot more power to start to move axis and when already
> moving the required power is a way smaller.
> And if that ratio is big then
On Thu, 2011-02-03 at 21:51 +1100, Erik Christiansen wrote:
> On Wed, Feb 02, 2011 at 11:48:05PM +, andy pugh wrote:
> > On 2 February 2011 10:22, Erik Christiansen wrote:
> >
> > > Ah, if it surfaces, and a scanner is conveniently close to hand, it'd be
> > > interesting to see, but your ide
S, Igor Chudov piše:
> On Thu, Feb 3, 2011 at 7:16 AM, Slavko Kocjancic wrote:
>
>> That's not problem of friction at all!.
>>
>> The worst you have is 'sticky' axis.
>> That means you need a lot more power to start to move axis and when already
>> moving the required power is a way smaller.
>>
>
Igor Chudov wrote:
> On Thu, Feb 3, 2011 at 7:16 AM, Slavko Kocjancic wrote:
>
>
>> That's not problem of friction at all!.
>>
>> The worst you have is 'sticky' axis.
>> That means you need a lot more power to start to move axis and when already
>> moving the required power is a way smaller.
On Thu, Feb 3, 2011 at 7:16 AM, Slavko Kocjancic wrote:
> That's not problem of friction at all!.
>
> The worst you have is 'sticky' axis.
> That means you need a lot more power to start to move axis and when already
> moving the required power is a way smaller.
>
No.
This is an axis with frict
That's not problem of friction at all!.
The worst you have is 'sticky' axis.
That means you need a lot more power to start to move axis and when already
moving the required power is a way smaller.
And if that ratio is big then tuning PID is near imposible. You can have low
static error or low (or
On Wed, Feb 02, 2011 at 06:31:24PM +, Steve Blackmore wrote:
>
> I don't use any belville washers, I thread the handle end the shaft. A
> nut and washer takes up the endfloat slack against the bearings and I
> thread the inside of one half of an Oldham coupling to match. That then
> screws on
On Wed, Feb 02, 2011 at 11:48:05PM +, andy pugh wrote:
> On 2 February 2011 10:22, Erik Christiansen wrote:
>
> > Ah, if it surfaces, and a scanner is conveniently close to hand, it'd be
> > interesting to see, but your ideas on how best to take up the slack are
> > most valuable.
>
> I need
On 2 February 2011 10:22, Erik Christiansen wrote:
> Ah, if it surfaces, and a scanner is conveniently close to hand, it'd be
> interesting to see, but your ideas on how best to take up the slack are
> most valuable.
I needed an excuse to re-familiarise myself with Inventor, so
http://picasaweb.
On Wed, Feb 2, 2011 at 1:57 PM, Kirk Wallace wrote:
> On Wed, 2011-02-02 at 12:13 -0700, kil...@bobodyne.com wrote:
> ... snip
> > Are you talking about a constant friction or somethingmore like
> > sticktion where the initia zero-velocity friction is much higher than the
> > constant velocity fri
On Wed, 2011-02-02 at 12:13 -0700, kil...@bobodyne.com wrote:
... snip
> Are you talking about a constant friction or somethingmore like
> sticktion where the initia zero-velocity friction is much higher than the
> constant velocity friction?
... snip
That's a good point. With any kind of friction
> What do you mean by step-response, sorry.
It's a set of data showing how your system responded
when you changed the target by "a step".
> I am OK, right now my following error is something like
> 2-3 minutes of arc
2-3 minutes of arc tell me you're controlling something
rotat
On Wed, Feb 2, 2011 at 1:13 PM, wrote:
> > DC servo motor with encoder like feedback (it has a resolver adn resolver
> to
> > quadrature converter card).
>
> > Well, I would really like a tuning component that compensates for
> friction.
> > P,I,D are not quite it.
> >
> > I already tuned P to be
> DC servo motor with encoder like feedback (it has a resolver adn resolver to
> quadrature converter card).
> Well, I would really like a tuning component that compensates for friction.
> P,I,D are not quite it.
>
> I already tuned P to be quite high, almost as high as possible but still
> witho
On Wed, Feb 2, 2011 at 12:58 PM, wrote:
> > Now, guys, I am really wondering if there is a way in EMC2 to compensate
> for
> > high friction?
>
> Do you have an encoder feedback system or an open-loop system?
>
>
DC servo motor with encoder like feedback (it has a resolver adn resolver to
quadrat
> Now, guys, I am really wondering if there is a way in EMC2 to compensate for
> high friction?
Do you have an encoder feedback system or an open-loop system?
If you have an encoder-feedback system, this set of pages might help
you understand the steps required to tune a PD controller bor best
pe
Now, guys, I am really wondering if there is a way in EMC2 to compensate for
high friction?
--
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On Wed, 2 Feb 2011 21:22:26 +1100, you wrote:
>Ah, that's just what I was puzzling over. How to remove the end-float in
>a way that works, yet isn't horribly complicated. I figured that the
>axial space in the eccentric housing has to either be a tight fit on the
>length of the worm plus thrust be
On Fri, Jan 28, 2011 at 09:15:30AM +, andy pugh wrote:
> On 28 January 2011 04:24, Erik Christiansen wrote:
>
> > Is slack best taken up by carefully measuring existing slack, almost
> > making enough room for the thrust bearings, then skimming to fit?
> > (A shim is easier to trim to size, p
On 28 January 2011 04:24, Erik Christiansen wrote:
> Is slack best taken up by carefully measuring existing slack, almost
> making enough room for the thrust bearings, then skimming to fit?
> (A shim is easier to trim to size, perhaps.)
I am not entirely sure what you are asking.
I ended up mak
On Thu, Jan 27, 2011 at 01:42:09PM +, andy pugh wrote:
>
> My manual-to-cnc conversion of a small rotary table ended up with me
> adding a needle roller support at the worm end, and a pair of angular
> contact bearings outboard to take the thrust loads and eliminate the
> end float.
>
> It no
is the 'strange brown colored grease' gritty? then look for rust
just pastey, waxy? may well be cosmolene ( rust preventative )
--
Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)!
Finally, a world-class
On Thu, Jan 27, 2011 at 11:50 AM, Steve Blackmore wrote:
> On Thu, 27 Jan 2011 08:21:33 -0600, you wrote:
>
> >No air fittings that I can find. I will try to open up this RT. I opened
> one
> >end of it and found strange brown colored grease near the 90 degree gear.,
>
> I'd be tempted to take it
On Thu, 27 Jan 2011 08:21:33 -0600, you wrote:
>No air fittings that I can find. I will try to open up this RT. I opened one
>end of it and found strange brown colored grease near the 90 degree gear.,
I'd be tempted to take it apart, clean it out and relube. Like you say
in your write up, it's pr
No air fittings that I can find. I will try to open up this RT. I opened one
end of it and found strange brown colored grease near the 90 degree gear.,
On Thu, Jan 27, 2011 at 7:37 AM, andy pugh wrote:
> On 27 January 2011 13:17, Igor Chudov wrote:
>
> >> It is called a Troyke U12PNC. Here's ar
On 27 January 2011 13:28, Erik Christiansen wrote:
> Unfortunately it's after loosening the lock, and adjusting that
> eccentric worm mount that I have quite a few degrees of slack in the
> worm.
This is probably end-float in the worm.
My manual-to-cnc conversion of a small rotary table ended u
On 27 January 2011 13:17, Igor Chudov wrote:
>> It is called a Troyke U12PNC. Here's are pictures and many details:
I don't suppose there are any air fittings indicating that it has a clamp?
--
atp
"Torque wrenches are for the obedience of fools and the guidance of wise men"
-
On Thu, Jan 27, 2011 at 11:29:33AM +, Steve Blackmore wrote:
> Hi Erik - the handle housing is made eccentric to allow adjustment of
> the worm and wheel engagement. Loosen the locks then adjust the
> eccentric so it's just binding, (that should reduce nearly all the slack
> in the handle) the
On Thu, Jan 27, 2011 at 2:43 AM, Steve Blackmore wrote:
> On Wed, 26 Jan 2011 22:03:33 -0600, you wrote:
>
> >Eric, the friction on my linear axes is not anywhere close to the friction
> >in the rotary table. IIRC, it takes less than an amp to move my X axis,
> and
> >over 3 amps to move the rota
On Thu, 27 Jan 2011 21:15:00 +1100, you wrote:
>Many thanks for the tuning tips, Steve. It's a Vertex which allows
>nearly 15° of handle movement with the table locked. I'll try your
>suggestions.
Hi Erik - the handle housing is made eccentric to allow adjustment of
the worm and wheel engagemen
On 27 January 2011 03:01, Jon Elson wrote:
> (For completeness, FF0 is feedforward proportional to position, not a
> really helpful
> term.)
It seems to me that FF0 would be ideal for a closed-loop spindle speed
control PID.
The FF0 term gives you the PWM duty cycle directly proportional to
spee
On Thu, Jan 27, 2011 at 08:43:25AM +, Steve Blackmore wrote:
> There are a plethora of Indian, Taiwanese and Chinese tables out there
> and quality and design varies greatly. Shoba, Soba & Vertex spring to
> mind. Some have bearings, some not, but all needed at least the worm
> running in with
On Wed, 26 Jan 2011 22:03:33 -0600, you wrote:
>Eric, the friction on my linear axes is not anywhere close to the friction
>in the rotary table. IIRC, it takes less than an amp to move my X axis, and
>over 3 amps to move the rotary table. It has a tight worm drive.
>
>I will indeed look at lubing
On Wed, Jan 26, 2011 at 9:53 PM, Erik Christiansen
wrote:
> On Wed, Jan 26, 2011 at 03:43:33PM -0600, Igor Chudov wrote:
> >
> > I finally got the table work with EMC2 (thanks to Jon), and have a
> problem
> > with is a high following error. The error is 0.04 degrees. Since there is
> a
> > consid
On Wed, Jan 26, 2011 at 03:43:33PM -0600, Igor Chudov wrote:
>
> I finally got the table work with EMC2 (thanks to Jon), and have a problem
> with is a high following error. The error is 0.04 degrees. Since there is a
> considerable reduction ratio in the work drive, the following error amounts
>
Igor Chudov wrote:
> My question is what servo tuning parameters could I use to compensate for
> high friction. It seems that I almost need FF(-1) or something like that?
>
FF1 is feedforward proportional to velocity. FF2 is feedforward
proportional to
acceleration. Neither of these will real
I have a rotary table (4th axis) that has considerable friction.
I know this because the DC servo motor requires at least about 4 amps, to
turn the table.
The rotary table has a tight worm drive, not some sort of a ballscrew, and
the drive is hard to turn. I did try that without the motor, by han
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