Re: [Emc-users] Servo Following Error

[Peter C. Wallace]

On Tue, 17 Dec 2013, Jeshua Lacock wrote:

> Date: Tue, 17 Dec 2013 18:09:18 -0700
> From: Jeshua Lacock 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: [Emc-users] Servo Following Error
> 
>
> Greetings,
>
> I dusted off my CNC machine which required a bit of TLC.
>
> The system is now perfectly stable and all axis work using both Manual 
> Control and MDI. Shortly after I try to run gcode it stops with most often a 
> following error or sometimes something is silently throwing the estop.
>
> I am using Pico's universal stepper controller with their gecko interface.
>
> Please see a plot of the axis that is causing the following error on my test 
> gcode:
>
>   http://3dtopo.com/z-servo-plot.png
>
> I am really stumped, any advice would be greatly appreciated!
>


maybe out of velocity headroom?



>
> Thanks,
>
> Jeshua Lacock
> Founder/Engineer
> 3DTOPO Incorporated
> 
> Phone: 208.462.4171
>
>
> --
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Peter Wallace
Mesa Electronics

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Re: [Emc-users] Servo Following Error

[Jeshua Lacock]

On Dec 17, 2013, at 6:49 PM, "Peter C. Wallace"  wrote:

> maybe out of velocity headroom?

Hi Peter,

Thanks, but I have the speed and acceleration way down for now. It used to work 
much much faster….


Thanks again,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated

Phone: 208.462.4171


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Re: [Emc-users] Servo Following Error

[Jeshua Lacock]

p.s.

It still can go plenty fast (200+ ipm) using manual control or MDI...

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Re: [Emc-users] Servo Following Error

[Peter C. Wallace]

On Tue, 17 Dec 2013, Jeshua Lacock wrote:

> Date: Tue, 17 Dec 2013 18:57:25 -0700
> From: Jeshua Lacock 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: Re: [Emc-users] Servo Following Error
> 
>
> p.s.
>
> It still can go plenty fast (200+ ipm) using manual control or MDI...

If my math is right it looks like it blew up at >200 IPM
(d/dt pos ~4 so ~4 IPS or 240 IPM)

Does the error happen in the same place if you run the program again?


>
> --
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Peter Wallace
Mesa Electronics

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Re: [Emc-users] Servo Following Error

[Jeshua Lacock]

On Dec 17, 2013, at 7:17 PM, "Peter C. Wallace"  wrote:

> On Tue, 17 Dec 2013, Jeshua Lacock wrote:
> 
>> Date: Tue, 17 Dec 2013 18:57:25 -0700
>> From: Jeshua Lacock 
>> Reply-To: "Enhanced Machine Controller (EMC)"
>>
>> To: "Enhanced Machine Controller (EMC)" 
>> Subject: Re: [Emc-users] Servo Following Error
>> 
>> 
>> p.s.
>> 
>> It still can go plenty fast (200+ ipm) using manual control or MDI...
> 
> If my math is right it looks like it blew up at >200 IPM
> (d/dt pos ~4 so ~4 IPS or 240 IPM)
> 
> Does the error happen in the same place if you run the program again?

Hi Peter,

It looks like Max Velocity was at the default max (912 in/min) for that test, 
but I confirmed it does the same thing with max velocity set way low like 16 
in/min.

Interesting it would go that fast though because currently the limits I have 
set for testing in the config file are far lower than that. E.g. that 
MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set to 
30.65.

It does seem to stop on the same gcode line for any given gcode file.


Best,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171


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Re: [Emc-users] Servo Following Error

[Peter C. Wallace]

On Tue, 17 Dec 2013, Jeshua Lacock wrote:

> Date: Tue, 17 Dec 2013 19:29:46 -0700
> From: Jeshua Lacock 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: Re: [Emc-users] Servo Following Error
> 
>
> On Dec 17, 2013, at 7:17 PM, "Peter C. Wallace"  wrote:
>
>> On Tue, 17 Dec 2013, Jeshua Lacock wrote:
>>
>>> Date: Tue, 17 Dec 2013 18:57:25 -0700
>>> From: Jeshua Lacock 
>>> Reply-To: "Enhanced Machine Controller (EMC)"
>>>
>>> To: "Enhanced Machine Controller (EMC)" 
>>> Subject: Re: [Emc-users] Servo Following Error
>>>
>>>
>>> p.s.
>>>
>>> It still can go plenty fast (200+ ipm) using manual control or MDI...
>>
>> If my math is right it looks like it blew up at >200 IPM
>> (d/dt pos ~4 so ~4 IPS or 240 IPM)
>>
>> Does the error happen in the same place if you run the program again?
>
> Hi Peter,
>
> It looks like Max Velocity was at the default max (912 in/min) for that test, 
> but I confirmed it does the same thing with max velocity set way low like 16 
> in/min.
>
> Interesting it would go that fast though because currently the limits I have 
> set for testing in the config file are far lower than that. E.g. that 
> MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set 
> to 30.65.
>
> It does seem to stop on the same gcode line for any given gcode file.

can you add a plot of the commanded velocity?

>
>
> Best,
>
> Jeshua Lacock
> Founder/Engineer
> 3DTOPO Incorporated
> <http://3DTOPO.com>
> Phone: 208.462.4171
>
>
> --
> Rapidly troubleshoot problems before they affect your business. Most IT
> organizations don't have a clear picture of how application performance
> affects their revenue. With AppDynamics, you get 100% visibility into your
> Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro!
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>

Peter Wallace
Mesa Electronics

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Re: [Emc-users] Servo Following Error

[Jeshua Lacock]

On Dec 17, 2013, at 7:33 PM, Peter C. Wallace  wrote:

> On Tue, 17 Dec 2013, Jeshua Lacock wrote:
> 
>> Date: Tue, 17 Dec 2013 19:29:46 -0700
>> From: Jeshua Lacock 
>> 
>> On Dec 17, 2013, at 7:17 PM, "Peter C. Wallace"  wrote:
>> 
>>> On Tue, 17 Dec 2013, Jeshua Lacock wrote:
>>> 
 Date: Tue, 17 Dec 2013 18:57:25 -0700
 From: Jeshua Lacock 
 
 p.s.
 
 It still can go plenty fast (200+ ipm) using manual control or MDI...
>>> 
>>> If my math is right it looks like it blew up at >200 IPM
>>> (d/dt pos ~4 so ~4 IPS or 240 IPM)
>>> 
>>> Does the error happen in the same place if you run the program again?
>> 
>> It looks like Max Velocity was at the default max (912 in/min) for that 
>> test, but I confirmed it does the same thing with max velocity set way low 
>> like 16 in/min.
>> 
>> Interesting it would go that fast though because currently the limits I have 
>> set for testing in the config file are far lower than that. E.g. that 
>> MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set 
>> to 30.65.
>> 
>> It does seem to stop on the same gcode line for any given gcode file.
> 
> can you add a plot of the commanded velocity?

Sure thing, please see:

http://3dtopo.com/z-servo-plot2.png

It is now the 4th channel (purple).

You can also see my LinuxCNC window and the line it stops at for this file.


Best,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated

Phone: 208.462.4171


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Re: [Emc-users] Servo Following Error

[Jon Elson]

On 12/17/2013 07:09 PM, Jeshua Lacock wrote:
> Greetings,
>
> I dusted off my CNC machine which required a bit of TLC.
>
> The system is now perfectly stable and all axis work using both Manual 
> Control and MDI. Shortly after I try to run gcode it stops with most often a 
> following error or sometimes something is silently throwing the estop.
>
> I am using Pico's universal stepper controller with their gecko interface.
>
> Please see a plot of the axis that is causing the following error on my test 
> gcode:
>
>   http://3dtopo.com/z-servo-plot.png
>
> I am really stumped, any advice would be greatly appreciated!
>
>
>

Ah, you say the Gecko interface.  So, you probably are using
brush servo motors and the Gecko 320 step-servo drive.
It may just be running out of dynamic range.  What is your
power supply voltage?  I see in the delta plot that the velocity
is ramping up to 5 units, meaning 5 encoder counts/servo
period, or typically 5000 counts/second.  Taking a wild 
assumption
of 500 cycle/rev encoders, that would be 2.5 revs/second or
150 RPM, which doesn't sound very fast.  But, if they are
500 count/rev encoders, that would be 600 RPM.  Depending
on the motor and the supply voltage, that could be as fast as
it can go.

Also, there are parameters in the .ini file such as
MAX_VELOCITY
PID_MAX_VEL
OUTPUT_SCALE

OUTPUT_SCALE is a **divider**, so larger numbers reduce the
output command to the step generator.  Generally, it is left at
1.0 (or -1.0 to reverse direction).
MAX_VELOCITY and PID_MAX_VEL are in user units per SECOND.
PID_MAX_VEL should be slightly higher than MAX_VELOCITY to
give the PID calculation a little headroom for acceleration.
Make sure these ini file settings are sufficient for your 
machine.

It looks from your plot that the move is about .4" per second,
or 24 IPM.  Figure out how many RPM you need to move at that
speed, then work backwards from supply voltage and motor
ratings to see if the voltage can give that speed.

Feel free to contact me if the above hints don't point you
to the solution.

Jon
Jon

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Re: [Emc-users] Servo Following Error

[Jon Elson]

On 12/17/2013 08:29 PM, Jeshua Lacock wrote:
>
>
> It looks like Max Velocity was at the default max (912 in/min) for that test, 
> but I confirmed it does the same thing with max velocity set way low like 16 
> in/min.
Turning MAX_VELOCITY down in the INI file will make it 
worse.  OR,
do you mean turning it down in the GUI (Axis?)  Depending on 
LinuxCNC
version, the GUI max velocity slider may not limit your
rapid\feed (G0) moves!  So, make sure you can move at the 
desired
speeds in G1 first.  If it only fails in G0, then it is most 
likely that
you have set excessive velocities in your [TRAJ] section.
> Interesting it would go that fast though because currently the limits I have 
> set for testing in the config file are far lower than that. E.g. that 
> MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set 
> to 30.65.
My reading of the plot is about one vertical unit at .2" 
(200m) in half
a second, or .4" per second = 24 IPM.  That's a rough guess 
by eye.
Also, the error trace is very suspicious!  It hums along at 
a very small
error (~.0005" or less) for the entire move, then suddenly 
surges to
.010" or so when it trips the following error limit.  The 
only thing I can
figure is that the next command is for a MUCH higher velocity,
which the motion hardware cannot perform.
>
> It does seem to stop on the same gcode line for any given gcode file.
>
That is also quite bizarre, if true.  If the "same line" of 
the G-code file
tells it to do something different, it would be odd for that 
to cause
a fault.

Jon

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Re: [Emc-users] Servo Following Error

[Jeshua Lacock]

On Dec 17, 2013, at 8:26 PM, Jon Elson  wrote:

> n 12/17/2013 08:29 PM, Jeshua Lacock wrote:
>> 
>> 
>> It looks like Max Velocity was at the default max (912 in/min) for that 
>> test, but I confirmed it does the same thing with max velocity set way low 
>> like 16 in/min.
> Turning MAX_VELOCITY down in the INI file will make it 
> worse.  OR,
> do you mean turning it down in the GUI (Axis?)  Depending on 
> LinuxCNC
> version, the GUI max velocity slider may not limit your
> rapid\feed (G0) moves!  So, make sure you can move at the 
> desired
> speeds in G1 first.  If it only fails in G0, then it is most 
> likely that
> you have set excessive velocities in your [TRAJ] section.
>> Interesting it would go that fast though because currently the limits I have 
>> set for testing in the config file are far lower than that. E.g. that 
>> MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set 
>> to 30.65.
> My reading of the plot is about one vertical unit at .2" 
> (200m) in half
> a second, or .4" per second = 24 IPM.  That's a rough guess 
> by eye.
> Also, the error trace is very suspicious!  It hums along at 
> a very small
> error (~.0005" or less) for the entire move, then suddenly 
> surges to
> .010" or so when it trips the following error limit.  The 
> only thing I can
> figure is that the next command is for a MUCH higher velocity,
> which the motion hardware cannot perform.
>> 
>> It does seem to stop on the same gcode line for any given gcode file.
>> 
> That is also quite bizarre, if true.  If the "same line" of 
> the G-code file
> tells it to do something different, it would be odd for that 
> to cause
> a fault.

OK - thanks everyone for their help!

I actually just plugged the power supply directly into the wall instead of 
through a SSR controlled by the USC.

Must be some sort of interference?



Best,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated

Phone: 208.462.4171


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Re: [Emc-users] Servo Following Error

[Jon Elson]

On 12/17/2013 08:50 PM, Jeshua Lacock wrote:
> On Dec 17, 2013, at 7:33 PM, Peter C. Wallace  wrote:
>>
>> can you add a plot of the commanded velocity?
>
> Sure thing, please see:
>
> http://3dtopo.com/z-servo-plot2.png
>
> It is now the 4th channel (purple).
>
>
No, that is MEASURED velocity from the encoder.  I think the
COMMANDED velocity will be quite instructive, but I'm
not sure there  is a hal signal that displays that.

But, you are running version 2.5.3, and I think that version may
not obey the GUI velocity limits on G0 moves, which I 
clearly see
in your screenshot.  So, you might change those few G0's
at the beginning of your G-code programs to G1 and see if
that prevents the problem.  If so, then you may need to turn
down the MAX_VELOCITY in the [TRAJ] section of your .ini
file.  Or, possibly, the velocity is fine but the 
MAX_ACCELERATION
value is too high.

Jon


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Re: [Emc-users] Servo Following Error

[andy pugh]

On 18 December 2013 02:29, Jeshua Lacock  wrote:
>
>
> It looks like Max Velocity was at the default max (912 in/min) for that
> test, but I confirmed it does the same thing with max velocity set way low
> like 16 in/min.
>
> Interesting it would go that fast though because currently the limits I
> have set for testing in the config file are far lower than that. E.g. that
> MAX_VELOCITY for that drive is currently set to 30.5 and PID_MAX_VEL is set
> to 30.65.


The INI file numbers are in units per second. So that MAX_VELOCITY is set
to 1830 in/min.

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