Dual bipod winch foam cutter

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10 Jul 2011 17:54 #11360 by Rick G
Have you checked that your scale is correct, command the machine to move 1" and it does in fact move 1"?
1/8 micro step may be smoother than 1, but you may give up some speed depending on your computer's latency. And of course you will have to adjust your scale for this.
Have you tried changing settings in stepconfig to determine your best speed and smooth movement?

Rick G

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10 Jul 2011 19:00 #11363 by bvandiepenbos
I am not using stepconf ...it does not support bipod machine configuration does it?
I started with the german guys "hotwinch" .hal and .ini files,then edited pinouts to match my driver board.

~*Brian

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10 Jul 2011 19:03 #11364 by bvandiepenbos
I will check the scale.

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10 Jul 2011 19:20 - 10 Jul 2011 19:21 #11365 by bvandiepenbos
I still don't understand what values (or how to calculate) to use in the hotwinch.hal
Specifically here...

# joint 0
setp stepgen.0.position-scale [AXIS_0]SCALE
setp stepgen.0.steplen 1
setp stepgen.0.stepspace 0
setp stepgen.0.dirhold 27000
setp stepgen.0.dirsetup 27000

setp stepgen.0.maxaccel [AXIS_0]STEPGEN_MAXACCEL
net xpos-cmd axis.0.motor-pos-cmd => stepgen.0.position-cmd
net xpos-fb stepgen.0.position-fb => axis.0.motor-pos-fb
net xstep <= stepgen.0.step
net xdir <= stepgen.0.dir
net xenable axis.0.amp-enable-out => stepgen.0.enable

why is steplen only 1
why is stepspace 0
how is dirhold 27000 calculated
how is dirsetup 27000 calculated



I just ran stepconf and made up another fictitious machine,
put in 1000 for all timing values, this is what the .hal looked like...
setp stepgen.0.steplen 1
setp stepgen.0.stepspace 0
setp stepgen.0.dirhold 3600
setp stepgen.0.dirsetup 3600

aaaggghh, I am more confused than ever..
seems steplen is always 1, stepspace is always 0
I entered 1000 in stepconf, so how was 3600 calculated

sorry for being so thick headed, but I am just not getting it.
~*Brian
Last edit: 10 Jul 2011 19:21 by bvandiepenbos.

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10 Jul 2011 20:52 #11368 by andypugh
bvandiepenbos wrote:

aaaggghh, I am more confused than ever..
seems steplen is always 1, stepspace is always 0
I entered 1000 in stepconf, so how was 3600 calculated


What is your base period?
If the step length is less than the base period, then there is no point worrying about the exact number.

Though I am a bit surprised, because I thought that "reset" needed a real time.

I don't suppose you might be putting in timings in uS rather than nS (I am not too sure what is needed)

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10 Jul 2011 21:22 #11369 by btvpimill
I am going to go out on a limb here as I am not so well versed yet. but

I entered 1000 in stepconf, so how was 3600 calculated

I think you are confusing yourself over 2 different things. the 1000 pps would have something to do with velocity or accel. the dirhold/setup have to do with the pulse timing for your driver chip. Now if you are saying you did enter 1000 in the setup/hold section, then I am confused with you.

Hopefully someone will correct me if I am wrong, if not, hopefully it will help a little.

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11 Jul 2011 00:59 #11371 by bvandiepenbos
base period 33000
dirhold 27000
dirsetup 27000
scale 7.874

stepconf asks for ns

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11 Jul 2011 01:01 #11372 by bvandiepenbos
I am still confused.

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11 Jul 2011 09:48 #11384 by andypugh
bvandiepenbos wrote:

I am still confused.


I have been looking at the stepgen source, and I am now a little less confused.
git.linuxcnc.org/gitweb?p=emc2.git;a=blo...1742086cfbb5;hb=HEAD
Line 709 onwards.

Basically stepgen chooses a base period such that the period is long enough to not need more than one thread period per step. This makes sense, as the base period can be adjusted to nanoseconds, whereas if you are using multiple thread periods per step the resolution is in tens of uS. Whilst step_time is nominally in nS, setting it to 1 just means that it is set high when stepgen runs and there is a step request, and then low next thread execution.
In practice actual step time isn't set by the stepgen step_len parameter, but by the parport reset_time parameter. There is a function of the parport driver where a programmable time after setting the pins to the new configuration it sets pins in the reset mask back to zero. stepconf uses this (line 805) as it means you can have double the step rate.

The setup and hold time parameters are calculated in line 719/720 and seem to be the number you put in the boxes + the latency you put in the latency box. Does that fit?

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11 Jul 2011 13:59 #11402 by Rick G
Brian,

Just to avoid any further confusion on our part you have ..

Run Latency test for an extended period.
Taken the results of the Latency test and the timming praramters for your drivers and run them through Stepconfig on ficitious machine.
Taken these results and checked/editied your machine configuration.
Tried these and checked if the Scale is right (command 1" movement and machine moves 1")
Checked to make sure you are appling the correct amps to motors.

And motors run but not smooth.

Rick G

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