Re: AXIS CALIBERATION AND THE SAME OLD DIRTY POSITION COUNTER STUCK PROBLEM!! !

[Ray Henry <rehenry-at-up.net>]

Hi Babar

Just a quick note on a couple of the ini setings.  I hope that others 
will pitch in and help with some of the other questions.

> 	LINEAR_UNITS=0.03937007874016

This sets the unit of distance to 1 inch.  If you want to use inches for 
the machine you should leave all the instances of this 0.039... number 
alone.

Each axis has a simulation section.  It is all of the stuff between 

; Parameters for Inland Motor BMHS-0701 X 20 
and
COUNTS_PER_REV =                4096

These will not do you any good for the tuning of a real machine.

INPUT_SCALE is the variable that you will need to change to make each 
axis move an inch when you command an inch.  Since you do not know the 
pitch of the screws or the ratio between it and the encoder, I'd set up 
an indicator on an axis and command a small move.  Start with something 
like 0.100 from the jog increment and measure how far the axis moves.  
Then make a ratio of the distance you asked it to move divided by the 
distance the axis moved.  Multiply the current INPUT_SCALE in the ini you 
are using by this ratio and it should give you a value close to what you 
need to put in INPUT_SCALE.  

When you have done this one time, you can command longer distances, 
nearer to the full travel of your indicator and repeat the ratio 
computation.

Hope this helps.

Ray

On Tuesday 03 December 2002 11:51 pm, you wrote:
> Hi !
> we have got our board repaired (pld replaced) by STG
> but the problem of counter stuck when dc-servo is run
> from testing dialog box (by setting voltages) is still
> there.
> We had tried installing EMC with STG-II on a pentium-1
> machine
> with 64-MB ram. Now we see a bit improvement in
> position counter stucking. now we see this problem
> occuring for over 5V for each axis.
> in past this used to happen for voltages over 3. This
> seems to be good improvement by use of a slow machine.
> now we are running the x and y axis by limiting output
> voltage to +/-4V. (we have z-axis encoder problem
> therefore z -axis is not being touched). Have
> tuned the coefficients as follows
> P = 100
> I = 1
> D = 0
>
> VELOCITY FEED FORWARD GAIN = 1
> and all other set to 0
> now we can jog both the axis smoothely. we even have
> run them in mdi and auto mode.
>
>
> PROBLEMS RELATED WITH CALIBERATION
> we want to caliberate our milling so that a 1 inch
> travel in emc becomes 1 inch in real!! we dont know
> what screw picth we have for our all the three axis. I
> tried to find them in machine manual but didnt found
> them. instead i've found these:
>
> 	positioning accuracy: +/-0.001 in (+/- .03mm)
> 	system resolution: 0.0005 in (0.01 mm)
> 	repeatability: +/- 0.0005 in (0.01 mm)
> 	encoder lines: 200
>
> some parameters found in the ini are not
> understandable even after reading the help files.
> these are:
>
> 	INPUT_SCALE = ?
> in trajectory section there is a parameter called:
>
> 	LINEAR_UNITS=0.03937007874016
> what is it and do we need to change it?
>
> in [AXIS_X] section there are these parameters called:
> 	UNITS=0.03937007874016
> 	MAX_VELOCITY
>
> The following soft limits?
> 	MIN_LIMIT = -1000
> 	MAX_LIMIT = 1000
>
> we are using 200 lines encoder so i have set
> 	COUNTS_PER_REV = 800
> is this right?
>
>
> PROBLEMS RELATED WITH COUNTER STUCKING:
> - i had heard that multiple read pulses to IC7166
> during a single read   operation result in wrong
> position counts reading. Can anyone tell me   if the
> various code modules of emc software might be reading
> the       position counter latches simultaniously in
> different threads? or is    there any protection of
> position counter latches being accessed only   by a
> particular code module and a particular thread?
>
> - did anyone check? if the code that is reading the
> position counter
>   latches and validating the position counts is cpu
> clock dependent?
>
> - what may be the impact of fast frequency at
> quadrature inputs?
>   because we see counter stuck problem only when there
> is fast motion.
>
>
> HISTORY:
> we are using bdiemc209-01 also had tried bdiemc212-01
> but found same position counter stucking problem.
>
> used generic.ini modified and renamed it to our
> milling machine hurco.ini to suit our STG-II board
> mounted at address = 0x200. we are using tkEMC
> display.
>
> for auxiliary output we are using LPT port at address
>  = 0x378
>
> have Quadrature encoder with with differential
> outputs.
>
> we had implemented the star ground. and infact played
> alot with various grounding options but no use. now i
> suspect that the problem lies with some code module in
> emc. which troubles.
>
> all the cycle times found in the ini were played with
> but no use
> in our counter stucking problem
>
> various board base addresses of STG-II were tried but
> no improvement
> in our counter stucking problem.
>
> regards
> babar
>
>
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