Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 5:38 PM, andy pugh wrote:
> On 23 March 2017 at 22:20, hubert  wrote:
>> My Bad it should have been this link
>> http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-40C-100-E250-AC-Servo-Actuator-/111964401976?hash=item1a11993138:g:3JsAAOSwSzdXCcXg
> Don't rush into buying one. I set up a search on eBay and got mine for
> $250 after about 2 weeks of looking.
>
> And take note of what I say about the encoder unless you get the
> matching drive.
>
If I am reading this manual correctly this Actuator is 4 wire 
incremental pulse.  What are you using for a driver?


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Re: [Emc-users] More Renishaw questions

[Dave Caroline]

Ken I have a LT02 and that is switched on by a just about any infrared
pulse waveform and the return appears to be 115k baud optical, I am
building my own OMM with an arduino MI as soon as I get around to it,
had to get a fast opto diode an opto transistor I first obtained was
deaf and too slow (less than an inch to get a signal)

Results will be on the web soon.

Dave Caroline

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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 22:20, hubert  wrote:
> My Bad it should have been this link
> http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-40C-100-E250-AC-Servo-Actuator-/111964401976?hash=item1a11993138:g:3JsAAOSwSzdXCcXg

Don't rush into buying one. I set up a search on eBay and got mine for
$250 after about 2 weeks of looking.

And take note of what I say about the encoder unless you get the
matching drive.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 5:06 PM, andy pugh wrote:
> On 23 March 2017 at 21:45, hubert  wrote:
>> I am contemplating purchase of this one
>> http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-17C-100-E250-AC-Servo-Actuator-/111964389396?hash=item1a11990014:g:jCQAAOSwjMJXCcGL
>> If I read it right it has 100 to one step down ratio and 2500 pulses per
>> revolution, I don't know what the E signifies.  I am assuming that the
>> 2500 pulses is for 1 revolution of the Servo motor, not the output drive.
> Be very sure that you can drive the FHA-nnC variant, I think they have
> a serial absolute encoder.
> The (much older) FHA-nnB have ordinary quadrature encoders and hall sensors.
>
My Bad it should have been this link
http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-40C-100-E250-AC-Servo-Actuator-/111964401976?hash=item1a11993138:g:3JsAAOSwSzdXCcXg


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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 21:45, hubert  wrote:
> I am contemplating purchase of this one
> http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-17C-100-E250-AC-Servo-Actuator-/111964389396?hash=item1a11990014:g:jCQAAOSwjMJXCcGL
> If I read it right it has 100 to one step down ratio and 2500 pulses per
> revolution, I don't know what the E signifies.  I am assuming that the
> 2500 pulses is for 1 revolution of the Servo motor, not the output drive.

Be very sure that you can drive the FHA-nnC variant, I think they have
a serial absolute encoder.
The (much older) FHA-nnB have ordinary quadrature encoders and hall sensors.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 21:24, hubert  wrote:
> I think I will buy the camlocks and start there.  I like your split
> model but how would you machine the recesses for the cam lock? ball
> mill?  You mention making a casting.  Do you think it would accommodate
> the 40 MM size as well?

If I was to make the split version I would:
1) Make the part that bolts to the drive. Machine only the rear
register and 8x screw holes for the drive and 6 x for the front half
2) make the part that bolts to the front, bolt it on and machine the
taper with an allowance.
3) Mount on the harmonic drive, then use the drive to index round to
machine and bore the camlock cam holes and stud holes on the
horizontal axis of my mill.
4) in-situ grind the taper using the horizontal axis of the mill.

My casting is only wide enough for the 25 size. Even the 25 is wider
than my T-slot table.
https://goo.gl/photos/E3qxr2sGSaSodqJo8


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atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 4:13 PM, andy pugh wrote:
> On 23 March 2017 at 20:33, hubert  wrote:
>> I found this
>> http://harmonicdrive.de/mage/media/catalog/category/1018853_FHA_C_en.pdf
>> reference on harmonic drives
>> and noticed the 25 or 32 etc in the model number seemed to reflect
>> approximately the internal bore of the hollow shaft.  I have some desire
>> to be able to move things from my lathe to the Mill and since the lathe
>> spindle bore is 40MM it sounds like a choice of 40 would be practical.
>>   From the dimensions in the above catalog seem to still fit within a
>> 250MM swing or in my case 10"(254mm).
>>
>> Is this above catalog representative of the offerings on ebay?
> Slightly more dimensions here:
> http://www.harmonicdrive.net/products/rotary-actuators/hollow-shaft-actuators/fha-c
>
> Bores are slightly larger than size-code.
>
> The larger sizes might make it easier to mount a D1 spindle nose, but
> the problem that 6 into 8 doesn't go remains.
> FHA17 has 6 holes, but is probably too small.
>
I am contemplating purchase of this one 
http://www.ebay.co.uk/itm/Harmonic-drive-systems-Used-FHA-17C-100-E250-AC-Servo-Actuator-/111964389396?hash=item1a11990014:g:jCQAAOSwjMJXCcGL
If I read it right it has 100 to one step down ratio and 2500 pulses per 
revolution, I don't know what the E signifies.  I am assuming that the 
2500 pulses is for 1 revolution of the Servo motor, not the output drive.

I think once satisfied with the 4th Axis I may want to play with an 
FHA17 as a 5th axis.

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Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 3:14 PM, andy pugh wrote:
> On 23 March 2017 at 17:01, hubert  wrote:
>> I have a Grizzly G0709 lathe and they offer these as spare parts.
>>
>> http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com
> Do they list the entire spindle? It would save some machining.
That was my thoughts as well they list it but say it is na.

I think I will buy the camlocks and start there.  I like your split 
model but how would you machine the recesses for the cam lock? ball 
mill?  You mention making a casting.  Do you think it would accommodate 
the 40 MM size as well?
>
>


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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 20:33, hubert  wrote:
> I found this
> http://harmonicdrive.de/mage/media/catalog/category/1018853_FHA_C_en.pdf
> reference on harmonic drives
> and noticed the 25 or 32 etc in the model number seemed to reflect
> approximately the internal bore of the hollow shaft.  I have some desire
> to be able to move things from my lathe to the Mill and since the lathe
> spindle bore is 40MM it sounds like a choice of 40 would be practical.
>  From the dimensions in the above catalog seem to still fit within a
> 250MM swing or in my case 10"(254mm).
>
> Is this above catalog representative of the offerings on ebay?

Slightly more dimensions here:
http://www.harmonicdrive.net/products/rotary-actuators/hollow-shaft-actuators/fha-c

Bores are slightly larger than size-code.

The larger sizes might make it easier to mount a D1 spindle nose, but
the problem that 6 into 8 doesn't go remains.
FHA17 has 6 holes, but is probably too small.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 2:09 PM, andy pugh wrote:
> On 23 March 2017 at 18:15, hubert  wrote:
>> SkyFire the builder of my mill offers a complete
>> ready to hook to my Mesa 7I86 8" Harmonic Drive for about $2000.  It
>> isn't my dream solution, but doesn't break my bank either.
> Looking at the spec and the screws holding the rotary table on, it
> might be a very similar drive internally.
>
> But being stepper-driven I assume not exactly the same.
>
I found this 
http://harmonicdrive.de/mage/media/catalog/category/1018853_FHA_C_en.pdf 
reference on harmonic drives
and noticed the 25 or 32 etc in the model number seemed to reflect 
approximately the internal bore of the hollow shaft.  I have some desire 
to be able to move things from my lathe to the Mill and since the lathe 
spindle bore is 40MM it sounds like a choice of 40 would be practical.  
 From the dimensions in the above catalog seem to still fit within a 
250MM swing or in my case 10"(254mm).

Is this above catalog representative of the offerings on ebay?

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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 17:01, hubert  wrote:
> I have a Grizzly G0709 lathe and they offer these as spare parts.
>
> http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com

Do they list the entire spindle? It would save some machining.



-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] More Renishaw questions

[andy pugh]

On 23 March 2017 at 18:28, Ken Strauss  wrote:
> >From postings on this list earlier this year I believe that Sarah Armstrong
> and Rene Hopf (and perhaps others) have had some success interfacing to a
> Renishaw MP10 or similar probe. I recently got an MP7 so I'm very interested.

I decided not to bother with the inductive link on mine, and only
retained the probe itself, hard-wiring it to a GPIO.
I got a little bit fancy with a home-made "Magsafe" style connector,
in case I ever forgot to remove it before starting the spindle.

This approach saves me a fair bit of headroom, which is a plus with my
small mill.

https://goo.gl/photos/snGgoumya4gXL3Ar8

I kept the ball interface betwixt the probe and the arbour, there is a
gap where the screws are to allow the probe-ball to be centred.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] More Renishaw questions

[Ken Strauss]

I haven't managed to find an OMM + MI7 for an affordable price (this is only
a hobby). My current plan (hope) is to build the equivalent of an OMM. I
assume that what is required is something like a Vishay TEMD1000 photodiode
feeding a TIA and then follow with an Arduino or something similar to decode
the contact/battery low signals. It would be great if I could start with
something that is known to work to acquire the IR signal.

> -Original Message-
> From: Erik Friesen [mailto:e...@aercon.net]
> Sent: Thursday, March 23, 2017 2:39 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] More Renishaw questions
>
> Do you have an OMI, or are you trying to connect directly with your own?
>
> On Thu, Mar 23, 2017 at 2:28 PM, Ken Strauss 
> wrote:
>
> > >From postings on this list earlier this year I believe that Sarah
> > Armstrong
> > and Rene Hopf (and perhaps others) have had some success interfacing
> > to a Renishaw MP10 or similar probe. I recently got an MP7 so I'm very
> > interested.
> >
> > Can anyone provide details of the electronics that they used used to
> > detect and cleanup the IR signal? What was the range for reliable
pickup?
> >
> >
> >
> > 
> > --
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>

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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 18:15, hubert  wrote:
> SkyFire the builder of my mill offers a complete
> ready to hook to my Mesa 7I86 8" Harmonic Drive for about $2000.  It
> isn't my dream solution, but doesn't break my bank either.

Looking at the spec and the screws holding the rotary table on, it
might be a very similar drive internally.

But being stepper-driven I assume not exactly the same.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] More Renishaw questions

[Erik Friesen]

Do you have an OMI, or are you trying to connect directly with your own?

On Thu, Mar 23, 2017 at 2:28 PM, Ken Strauss 
wrote:

> >From postings on this list earlier this year I believe that Sarah
> Armstrong
> and Rene Hopf (and perhaps others) have had some success interfacing to a
> Renishaw MP10 or similar probe. I recently got an MP7 so I'm very
> interested.
>
> Can anyone provide details of the electronics that they used used to detect
> and cleanup the IR signal? What was the range for reliable pickup?
>
>
>
> 
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[Emc-users] More Renishaw questions

[Ken Strauss]

>From postings on this list earlier this year I believe that Sarah Armstrong 
and Rene Hopf (and perhaps others) have had some success interfacing to a 
Renishaw MP10 or similar probe. I recently got an MP7 so I'm very interested.

Can anyone provide details of the electronics that they used used to detect 
and cleanup the IR signal? What was the range for reliable pickup?



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Re: [Emc-users] Thing with a square hole

[hubert]

On 3/23/17 10:01 AM, andy pugh wrote:
> On 23 March 2017 at 01:23, hubert  wrote:
>> How are you  approaching this project?   I am assuming that you
>> are starting with a plate that will be attached to the 4th axis and
>> machining that plate to accept the cam lock studs and cam locks.  In my
>> case I can get a complete set(6 ea) of locks from my Lathe source for US
>> $36.  Are there any precautions that I should watch for when I attempt
>> this project?
> The basis of the project is a harmonic drive with integral motor and
> through-shaft.
> I have an FHA-25 size, but FHA-32 might be better.
>
> The current model drives (FHA-25C) seem to have a serially interfaced
> encoder, which looks complicated.
> The FHA-25B is a model that HD have no data on, but I found a document from 
> ESO
> http://www.ls.eso.org/lasilla/support/electronics/Documentation/PDF/3P6-DSD-ESO-60400-0001.pdf
> Which gives the pinout and wire colours (if you look carefully) and
> that is a simple quadrature encoder + hall sensor setup and so rather
> easier to drive.
>
> eBay has a few of these drives, at widely differing prices, some with
> the dedicated servo amp.
> http://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=FHA-25B_PrefLoc=2&_sop=15
>
> Mine is a FHA-25B-3015-E150C-SP
>
> I am making a pattern to make a cast-iron housing for bolting to my
> mill table, designed around a max swing of 250mm. Making extra
> castings is trivial at that point.
>
> The output face of the drive has a circle of 8 x M6 holes on a 74mm
> PCD. This is actually slightly awkward for a D1-4 spindle nose, which
> has 3 pins and tangential retainers. I could only get 3 bolts in if I
> kept the standard tangential retainers, so I am using axial retainers.
> D1-5 already has axial retainers, but also has 6 studs.
>
> I have modelled the D1-5 nose and attempted to fit the 74mm PCD holes
> in. It's not pretty. two of the holes are impossible, I think, and the
> others need to be counterbored so deep that the heads are lower than
> the D1 cams (or they have to go through them). And they eat into the
> retaining taper.
> http://a360.co/2nMOEnm should let you view the 3D-model of the D1-4.
That looks like a D1-5 to me.  As my starting point I have a 10" Rotary 
table that I have fitted with small stepper.  I will use it to do form 
and fit experiments.  I am contemplating either purchase of building a 
Harmonic drive system.  SkyFire the builder of my mill offers a complete 
ready to hook to my Mesa 7I86 8" Harmonic Drive for about $2000.  It 
isn't my dream solution, but doesn't break my bank either.  I still need 
to do more research into Harmonic Drives to determine what is feasible.
>
> I think that the answer would be to make the dummy-spindle-nose in two
> parts, one that bolts to the harmonic drive, and then a second section
> that bolts to that which has the taper.
> (then in-situ grind the locating taper, ideally).



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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 17:49, hubert  wrote:
> If you look in the GO790 Manual or parts list it shows the part.

Here is a way to make a nose with "embedded" screw heads.

http://a360.co/2mUXk6s

You can see inside with the "explode" slider.

I might even make mine this way, it will let me use all the mounting
screws and makes retaining the cams rather easy.


-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[hubert]

Should be GO709

http://www.grizzly.com/products/g0709/parts


On 3/23/17 12:49 PM, hubert wrote:
> If you look in the GO790 Manual or parts list it shows the part.
>
>
> On 3/23/17 12:20 PM, andy pugh wrote:
>> On 23 March 2017 at 17:01, hubert  wrote:
>>> I have a Grizzly G0709 lathe and they offer these as spare parts.
>>> http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com
>> Pity there is no picture to be sure that it is the right part.
>>
>>
>
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Re: [Emc-users] Thing with a square hole

[hubert]

If you look in the GO790 Manual or parts list it shows the part.


On 3/23/17 12:20 PM, andy pugh wrote:
> On 23 March 2017 at 17:01, hubert  wrote:
>> I have a Grizzly G0709 lathe and they offer these as spare parts.
>> http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com
> Pity there is no picture to be sure that it is the right part.
>
>


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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 17:01, hubert  wrote:
> I have a Grizzly G0709 lathe and they offer these as spare parts.
> http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com

Pity there is no picture to be sure that it is the right part.


-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Different acceleration profiles - something that would remove the discontinuity in the first derivative of the acceleration ?

[Nicklas Karlsson]

> Hello Everybody,
> 
> what Sebastian so eloquently described is what I originally meant,
> however what the other people that replied added is also relevant I
> think. The linear velocity phase results in a constant acceleration that
> will have a Dirac delta function in its first order derivative, and that
> is not desirable, due to the frequencies introduced.

Jerk could change value instantly since it depends on voltage. There is a more 
less linear correlation between current and torque. Derivative of current 
depends on inductance and voltage.  Then jerk is integrated to acceleration it 
will be a continuous function.

These are physical limitations in an ordinary servo motor.

I brought it up because I thought to keep within physical limitations is a good 
idea.


> I must admit that my understanding of DC motor internals is somewhat
> buried, also the last time I implemented a state control is 15y ago...So
> I ll not follow up on these suggestions, although they would probably
> tackle the problem at the root.

The DC machine model is rather simple if you understand electrical circuits. 
Dynamic model will be the same after commutation for a BLDC and very similar 
after a transformation for a PMSM, size of constants may however vary.


> Many years ago I implemented a sin^2(x) acceleration profile that was
> jerk free, ...

There must be some jerk otherwise there will be neither acceleration nor 
velocity. I think a limit on the jerk will be a good solution. I wrote some 
equation earlier and jerk i limited by speed because there will be a speed 
dependent back-emf in the motor, jerk to increase speed is not possible at 
maximum speed.

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Re: [Emc-users] Thing with a square hole

[hubert]

I have a Grizzly G0709 lathe and they offer these as spare parts.

http://www.grizzly.com/parts/P07090108?utm_campaign=zPage_source=grizzly.com


On 3/23/17 10:01 AM, andy pugh wrote:
> On 23 March 2017 at 01:23, hubert  wrote:
>> In my
>> case I can get a complete set(6 ea) of locks from my Lathe source for US
>> $36.
> Link?
>


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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 01:23, hubert  wrote:
> In my
> case I can get a complete set(6 ea) of locks from my Lathe source for US
> $36.

Link?

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Thing with a square hole

[andy pugh]

On 23 March 2017 at 01:23, hubert  wrote:
> How are you  approaching this project?   I am assuming that you
> are starting with a plate that will be attached to the 4th axis and
> machining that plate to accept the cam lock studs and cam locks.  In my
> case I can get a complete set(6 ea) of locks from my Lathe source for US
> $36.  Are there any precautions that I should watch for when I attempt
> this project?

The basis of the project is a harmonic drive with integral motor and
through-shaft.
I have an FHA-25 size, but FHA-32 might be better.

The current model drives (FHA-25C) seem to have a serially interfaced
encoder, which looks complicated.
The FHA-25B is a model that HD have no data on, but I found a document from ESO
http://www.ls.eso.org/lasilla/support/electronics/Documentation/PDF/3P6-DSD-ESO-60400-0001.pdf
Which gives the pinout and wire colours (if you look carefully) and
that is a simple quadrature encoder + hall sensor setup and so rather
easier to drive.

eBay has a few of these drives, at widely differing prices, some with
the dedicated servo amp.
http://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=FHA-25B_PrefLoc=2&_sop=15

Mine is a FHA-25B-3015-E150C-SP

I am making a pattern to make a cast-iron housing for bolting to my
mill table, designed around a max swing of 250mm. Making extra
castings is trivial at that point.

The output face of the drive has a circle of 8 x M6 holes on a 74mm
PCD. This is actually slightly awkward for a D1-4 spindle nose, which
has 3 pins and tangential retainers. I could only get 3 bolts in if I
kept the standard tangential retainers, so I am using axial retainers.
D1-5 already has axial retainers, but also has 6 studs.

I have modelled the D1-5 nose and attempted to fit the 74mm PCD holes
in. It's not pretty. two of the holes are impossible, I think, and the
others need to be counterbored so deep that the heads are lower than
the D1 cams (or they have to go through them). And they eat into the
retaining taper.
http://a360.co/2nMOEnm should let you view the 3D-model of the D1-4.

I think that the answer would be to make the dummy-spindle-nose in two
parts, one that bolts to the harmonic drive, and then a second section
that bolts to that which has the taper.
(then in-situ grind the locating taper, ideally).

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Different acceleration profiles - something that would remove the discontinuity in the first derivative of the acceleration ?

[Gene Heskett]

On Thursday 23 March 2017 07:01:19 MH wrote:

> Hello Everybody,
>
> what Sebastian so eloquently described is what I originally meant,
> however what the other people that replied added is also relevant I
> think. The linear velocity phase results in a constant acceleration
> that will have a Dirac delta function in its first order derivative,
> and that is not desirable, due to the frequencies introduced.
>
> I must admit that my understanding of DC motor internals is somewhat
> buried, also the last time I implemented a state control is 15y
> ago...So I ll not follow up on these suggestions, although they would
> probably tackle the problem at the root.
>
> Many years ago I implemented a sin^2(x) acceleration profile that was
> jerk free, I wondered if anybody else had implemented such a thing in
> the linuxcnc's TP.
>
Speaking from my electronics/broadcasting experience, where we have used 
a single sine^2(x) pulse as a general test signal for over 50 years, I 
can testify that if we had that in the tp, (and in the siggen module as 
a 4th choice of test signal shapes) it would be a most welcome addition 
to linuxcnc.  That single pulse on line 19  during the old ntsc vertical 
interval, picked out and viewed by the trained eye on an oscilloscope 
tells us everything we need to know about how well our transmitters were 
tuned. With the added advantage of being able to fine tune the 
transmitter while broadcasting a normal programming schedule.

If contributed to linuxcnc, that would be a major improvement milestone 
for linuxcnc.

> But using the feed forward terms is a very nice suggestion from Eric,
> ty for that, I ll do that today.
>
> BR
> Max.
>
> Am 22.03.2017 um 20:03 schrieb Sebastian Kuzminsky:
> > On 03/22/2017 12:50 PM, Nicklas Karlsson wrote:
> >>> Hello,
> >>>
> >>> I want to ask if anybody has worked on different acceleration
> >>> profiles for linuxcnc ? I am looking for something that would
> >>> remove the discontinuity in the first derivative of the
> >>> acceleration ?
> >>>
> >>> BR
> >>> Max.
> >>
> >> I guess to start with the DC motor model for example here
> >> https://www.electrical4u.com/torque-equation-of-dc-motor/ would be
> >> a good idea. Driving this with a limited voltage and current would
> >> probably be a good model for the limitations.
> >
> > I think Max is asking about changes to the LinuxCNC trajectory
> > planner that implement variable (non-constant) acceleration, aka
> > "limited jerk".
> >
> > Currently when you start from a stand-still, command a move, and
> > come to rest at the end of the move, LinuxCNC implements a
> > trapezoidal velocity profile.  This starts with a
> > constant-acceleration phase until it reaches the maximum speed for
> > the move, then enters a constant-velocity, zero-acceleration "cruise
> > phase", and finishes with a
> > constant-deceleration phase back to zero velocity.  Each phase
> > transition has an instant of infinite jerk, when acceleration goes
> > from one constant value to another in a single motion cycle.
> >
> > I think Yishin Li (https://github.com/yishinli) has done some work
> > in the area of jerk-limited trajectory planning, but AFAIK it has
> > not shown up as a pull request to our repo yet.
>
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Different acceleration profiles - something that would remove the discontinuity in the first derivative of the acceleration ?

[MH]

Hello Everybody,

what Sebastian so eloquently described is what I originally meant,
however what the other people that replied added is also relevant I
think. The linear velocity phase results in a constant acceleration that
will have a Dirac delta function in its first order derivative, and that
is not desirable, due to the frequencies introduced.

I must admit that my understanding of DC motor internals is somewhat
buried, also the last time I implemented a state control is 15y ago...So
I ll not follow up on these suggestions, although they would probably
tackle the problem at the root.

Many years ago I implemented a sin^2(x) acceleration profile that was
jerk free, I wondered if anybody else had implemented such a thing in
the linuxcnc's TP.

But using the feed forward terms is a very nice suggestion from Eric, ty
for that, I ll do that today.

BR
Max.








Am 22.03.2017 um 20:03 schrieb Sebastian Kuzminsky:
> On 03/22/2017 12:50 PM, Nicklas Karlsson wrote:
>>> Hello,
>>>
>>> I want to ask if anybody has worked on different acceleration profiles
>>> for linuxcnc ? I am looking for something that would remove the
>>> discontinuity in the first derivative of the acceleration ?
>>>
>>> BR
>>> Max.
>>
>> I guess to start with the DC motor model for example here 
>> https://www.electrical4u.com/torque-equation-of-dc-motor/ would be a good 
>> idea. Driving this with a limited voltage and current would probably be a 
>> good model for the limitations.
> 
> I think Max is asking about changes to the LinuxCNC trajectory planner 
> that implement variable (non-constant) acceleration, aka "limited jerk".
> 
> Currently when you start from a stand-still, command a move, and come to 
> rest at the end of the move, LinuxCNC implements a trapezoidal velocity 
> profile.  This starts with a constant-acceleration phase until it 
> reaches the maximum speed for the move, then enters a constant-velocity, 
> zero-acceleration "cruise phase", and finishes with a 
> constant-deceleration phase back to zero velocity.  Each phase 
> transition has an instant of infinite jerk, when acceleration goes from 
> one constant value to another in a single motion cycle.
> 
> I think Yishin Li (https://github.com/yishinli) has done some work in 
> the area of jerk-limited trajectory planning, but AFAIK it has not shown 
> up as a pull request to our repo yet.
> 
> 

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Re: [Emc-users] Different acceleration profiles --> state feedback control (error in sign)

[Nicklas Karlsson]

Robust control work so well research in control theory has really dried,
then can you tell me how to make robust control so we could change from PID
with feed forward to robust control?


2017-03-22 23:28 GMT+01:00 Eric Keller :

> I think you want to use feed-forward terms as well.  If you look at
> robust control, which pretty much obliterated pole-placement and
> optimal state feedback control, the general case includes feed-forward
> terms. This negates the problem that there always has to be an error
> in order for there to be control action.  Integrators will, in
> general, promote oscillation.
> Robust control can work so well that research in control theory has
> really dried up.
>
>
> On Wed, Mar 22, 2017 at 5:43 PM, Nicklas Karlsson
>  wrote:
> > There is an error in sign, it should be: (angle_ref -
> angle_mesaured)*gain1 + (velocity_ref - velocity_measured)*gain2 +
> (current_ref - current_measured)*gain3. From the set reference value for
> position the model is used used to calculate set reference value for all
> three values. There may also be an individual integrator for each.
> >
> > 
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