Lots counting errors at using the DDCSV with MPG

DAMIGO

Hi ytliu,

I tried your parameter settings for the #448. It does not change much or stabilize the counting. I understand that one mode is moving the motor so long i turn the wheel,
the other mode should exactly move the motor as the given value as turn by the mpg. I tried fast moving I tried slow moving, nothing changes or move the motor precise.
The digital display shows a not continous incrementing like described in the first posting.

So I measured the signals with an oscilloscope, and they are fine, no noise, no spikes, no glitches. Sadly I can not upload any pictures here from the measurement.

Kind regards
Daniel

DAMIGO

Hi ytliu,

thank you very much for your detailed explainations. I appreciate you effort to solve and to have a good product and Service.

Well this analysing I am through already. Also used 2 MPG plus a Quadrature Encoder. All of them Shows same behaviour. Please be informed my colleque Jay from the USA which have also a
DDCSV modul, has the same issues with unprecise counting. We both guess that there is a debouncer and a stable counting mechanism missing in the software.
The electronic in my humble opionion is really fine.

As Example: If am slowly turning I get Stepwidth is 0.5:

+0.5
+0.5
+0.4
+0.6
+0.5

now I turn back:
-0.5
-0.6
-0.4
-0.5
-0.5

Ist really ate the same counting back. For sure if I move very fast the MPG then it happens that's missing such counting easily and having values between 0.2-0.4.
But for now I would like to know, how this values are coming, because per tick you have to count 0.5 (given value) and to move the motor for 0.5, there can be
no way of 0.4 or 0.6 because the stepwidth is set to 0.5. So if the device would have a distortion or problem then it would miss one time 0.5 or having a 0.5 too much,
but not a value like 0.4 or 0.6.

Simulated electronic distortion:

MPG turn (tick)              Value
1                                  +0.5
1                                  +0.5
1                                  +0 or -0.5 (ooops device miss a tick or interprete the signalform wrongly)
1                                  +0.5
and so on.

   A: ___|-----|___
   B: _____|-----|____

If you respect rising and falling signal and you have a stepwidth 0.5 a counting of 2x 0.25 (rising and falling edge respected , dual Resolution)
If you respect only rising Signal and you have a counting stepwidth 0.5 a counting of 0.5 (single precision, single Resolution)

but never a range between 0.1 to 0.5 at a stepwidth of 0.5, it is just digital signal

DAMIGO

Dear enjoy_cnc,

My actual parameters, have actually the parameter from 431 set to 0.010, but it does not change at the
described behaviour:

[Motor Parameters]
34 X axis pulse equivalency =640,00
35 Y axis pulse equivalency =640,00
36 Z axis pulse equivalency =640,00
38 A axis pulse equivalency =640,00

[MPG parameters]
428 =Enable
429 =Low
430 =Standard
431 =0.010
432 =Low
434 =Low
448 =Open (also tried with Close, no difference)

Kind regards
Daniel

Can you guys, update this forum software for having the option to upload the pictures or data files,
else i have to send them all the time via email to you.

DAMIGO

Dear enjoy_cnc, Dear ytlui,

I tried your recommendation of your setting with 10000 als pulse equivalent, this setting reduced this error very very much, only at very
fast moving it seems it miss some signals from the MPG, seems the used optocoupler are maybe too slow. But nevertheless this error
got very very much reduced. and i got some times an error between +/- 0.001 to 0.006

So now i set my final values from my real motors, stepper power controller and leadscrew:

x/y has a leadscrew of 10mm/rev
z has a leadscrew of 2mm/rev

x/y motor set to 800 pulse per turn
z motor set to 400 pulse per turn

calculated values are then:
34 X axis pulse equivalency =80,00
35 Y axis pulse equivalency =80,00
36 Z axis pulse equivalency =200,00

with this values the error got seriously worst for x/y
turn 1 tick to pos = +0.013
turn 1 tick to neg = -0.012
if i turn more the mpg it it does not continous increment predictable stable values,
they jump like crazy between 0.010 - 0.019 some thing there in between.
Roll a dice for the next final position

for z at beginning and very slow slow turning it works +0.01 +0.1 etc.
but if i move just a little faster the mpg then i get +0.015 +0.01 +0.015 as
incremental or decremental values but always a difference of 0.005 as error
if this error occurs. That seems be not nice but somehow still accceptable.

The machine which I have, can work up to a precision to around 0.02 mm.

I can try to set higher revolution values for the x/y axis for minimizing the error,
but i will get weaker power on the motors if the have to move faster. for the Z
axis due the 2mm leadscrew I have to stay at the values of 200 thats a precision
of 0.005

At further testing and analysing, I think I found the problem:

At your email soon you will find the excel sheet calculation for the precision of the parameters,
I guess you will need to add some more information in your manual about the resolution in relation
of leadscrew and motor puls per revolution provided by the power stepper. Then the values
are explainable and also somehow the unprecision of the values. Seems sometimes a rounding error too.

DAMIGO

Dear all,

thank you for the analysing and trying to sort out the problem, we come to the
solutuion more near...

And mega thanks for the advice with the high mode :-) finally i can upload the stuff.

Well if the calculated precision value 0.0125 mm/stp and the MPG set to 0.01
then at moving positiv one tick i get: +0.013 (correct because last digit round up)
and in neg direction 0.012 (correct rounded). If you know this  speciality then
everything is explainable that with the presetting of 640 mm/step and 0.01 mpg precision
can not work because:

I assumed for the 640 mm/stp value:
16 x microsteps
5mm leadscrew
200step (1,8 degree) motor
gives a minimum resolution of 0.01563

So if you use then this value 0.01 as mpg precision, it will drives you
mad with the driven distance with the precision which can not be
reached of it. And if you turn the mpg you get non explainable values
which are rather jumpy.

So I add a calcsheet which i got from another cnc forum from
http://www.machsupport.com/forum/index.php/topic,16315.0.html
(you will need libreoffice or openoffice for the file which i add or load it from
the other forum which is in MS-Office).

With help of this file you can calculate the precision of your combination
of steps, leadscrew, motor and set microsteps. this calc minimum resolution
is the value which you need to set for the MPG precision.

If you have combination like my machine with different settings you
need to calc for all axis and readjust the parameters so that you find
a base together. for me was it then to set my setup for the Z axis to
a precision of 0.005 and the x,y Axis to precision of 0.01 (required to
change the microsteps from 4 to 5 to gain 1000 steps for 10mm leadscrew).
This is then the common base of 0.01 and this  i can set inside the MPG parameter
and the behaviour is then as mostly expected, but sometimes in rarely cases it miss
sometimes a signal. But for me still somehow OK.