Messages

4261

Mach4 General Discussion / Re: ESS + Mach4 + Clearpath = Motor error input goes where?

« on: June 20, 2018, 09:27:33 AM »

Hi,
AC servos are the next generation of servos by comparison to DC servos. The smarts provided by the manufacturer for tuning is the proof of the pudding.
Make no mistake PID tuning is in there, its just that you haven't had to concern yourself with it.

To make use of the scope what you need to do is either expand the following error window greatly or even turn it off. Go to Mach and icrease the acceleration of your X axis to something
very high, in effect infinite. Then if you issue an MDI:
G0 X100
then the X axis will attempt to move to the programmed location very quickly and will only be limited by the maximum speed the servo can accelerate. If you have the scope 'on' to
observe you will see the following error of the axis. As you decrease the acceleration of the X axis in Machs tuning page the following error will reduce. When it reduces to what you determine is
acceptable, lets say 0.05mm then you have established the maximum acceleration your X axis can achieve and you can set your following error window to just accommodate it.

Craig

4262

Mach3 under Vista / Re: Mach3, Windows 7, XP Mode

« on: June 20, 2018, 07:01:02 AM »

Hi,
OK those shot suggest that Mach is installed and running correctly and that the parallel port and pulse engine are running OK.

How have you set up your machine? May I suggest that you post a  shot of your Ports and Pins pages.

Another suggestion is DO NOT TRY TO ASSIGN ALL INPIUTS/OUTPTS AT ONCE. It will almost certainly fail and you will be so confused that you can't work out what the fault/faults are.
Much better is to assign one input or output at a time. Then you will learn those things that work and those that don't. Usually once you have those first few hurdles under your
belt assigning all the other IO comes much easier.

The first input you should try is an Estop switch. You will need a physical switch. Attach it to pin 10 or port 1. Assign that pin and port in Machs Inputs page. You should now be able to disable
Mach (the Reset Button blinks red) by hitting the switch. That confirms that an input to your breakout board is being successfully communicated back to Mach.

Let us know how you get on.

Craig

4263

Mach4 General Discussion / Re: Implementation of physical buttons

« on: June 20, 2018, 06:07:38 AM »

Hi,
open Configure/Plugins/ESS and on the Pins Config page give the input pin, port1,pin10 for example, used for the button of interest a suitable alias, and maybe an active low status.
While still within the ESS configuration screen open the Input Signals page and scroll down and enable one of the general purpose inputs Input10 say, and attach the pin alias
you have allocated to that button. Hit <apply> so that the changes are save to the .ini file.

You can then enter some code into the SigLib table at the top of the Screen Load script, if you follow this example:

[mc.ISIG_INPUT10]=function(state)
      if (state=1) then
               CycleStart()
       end
end

It may not be clear how this simple statement can effect what you wish.

In Mach3 the program would occasionally, every 25ms or so, interrogate all its input signals to see if any had activated. This is called polling. Its not very efficient, it checks each input in turn whether it needs
it or not and then waits for a long time before it checks it again. Mach4 is much better. Whenever ANY signal, input or output changes state it runs the signal script. It doesn't wait until some sampling time
it acts as soon as a signal changes. If for instance one of Machs internal signals changes, say AXIS0_STOPPED the the signal script will run. We are not interested in this signal so we don't act on it. If however
ISIG_INPUT10 changes we are interested in doing something. This is how Mach goes about it:

It runs the Signal Script  as per usual and the standard script is:
if SigLib[sig] ~= nil then
    SigLib[sig](state);
end

I know....so simple ...how can such a simple three lines do anything useful? All Mach knows at this point is that signal number <sig> has changed to <state>.
What happens is that Mach looks into the SigLib table, a Lua data structure to see if there is an entry in the table that matches <sig>. In our case there is in the form of ISIG_INPUT10.
Given that the test is affirmative Mach now executes the function associated with that entry and passes the variable <state> to the function. Mach now executes the function if <state>=1,
which in our case is yet another function called CycleStart() which is already in the screen load script.

This is an example of two important principles and concepts in Lua. The first is the table. Lua has ONLY one data structure, the table. The individual elements of the table may be arranged
in numerical order 1,2,3 etc. like we would an array in more familiar computer languages, but they can also be named out of order with positive AND negative arguments OR with STRING
arguments. Thus we could have a table:

MyFictiousTableInLua {
[1]='my first entry'
[2]='my second entry'
[2.345]= 'my third entry but note the real as opposed integer argument, perfectly legal in Lua'
[ARG4]='my fourth entry but with a string argument, again perfectly legal in Lua, even a mixed one like this'
[5] = function('it is also legal to have numbers , strings, functions and even a whole other table as an entry')
}

This is just an example of how flexible tables can be in Lua. As often happens in Lua what appears to be a very simple idea has remarkable flexibility and can
convey properties and possibilities well beyond what the simple idea would indicate.
The second  principle is a 'function as a first class value'. Thus you can see the last entry in my nonsense example table is a function whereas all the previous entries were
numbers or strings. A function can be treated just as another number...very simple and clever and allows Lua to perform great feats of computing despite being such a simple
language.

The upshot is that SigLib, a simple table in Lua, is in fact a table that contains functions, one function for each of the signals that we are interested in. Very clever, simple,
elegant and very lean computationally.

Lua is a real eye opener, I thought NFS had made a mistake when I first started to use it but these deceptively simple ideas mean that Lua is very powerful indeed. I
have very much changed my mind. C/C++ can do just about anything but is tightly typed and you have to manage your own memory. Lua is almost type free and
memory management is automatic such a boon to Mach4
When coding I have this link open pretty much permanently:

https://www.lua.org/manual/5.2/

Craig

4264

Mach4 General Discussion / Re: ESS + Mach4 + Clearpath = Motor error input goes where?

« on: June 19, 2018, 08:58:16 PM »

Hi,
I have a second hand Allen Bradley servo I use for a spindle motor. It has tuning software installed on my PC
to program the drives EPROM.

Amgonst the many many features of the software is a 'scope'. It allows you to follow various variables against
time for instance. Given that I use my servo as a spindle I've never really played with it. As a position
servo you can cause it to display position error (actual encoder count vs programmed position) in time.
It updates at the servo refresh rate, about 20kHz, so is hardly a 'high bandwidth oscilloscope' but none the less
provides a very useful visual indication of following error, all for the sake of a few keystrokes to program/set it up.

I don't know whether Teckincs have provided a similar facility for their Clearpath servos. Such a facility would go a long
way to answering your query about following error window verses positional accuracy. Note that such a display would
include the effects of the mass of the axis and its friction. Very useful and informative.

Years ago when I was at University studying this stuff much of the gear was analogue (resolvers, synchros, storage scopes
and some very groovy long stroke LDVT's), and while digital offer a few wrinkles of it own the principles of feedback
control remain the same. The gear was all expensive, often many many times the value of the servos and amps!

Craig

4265

Mach4 General Discussion / Re: Computer to run Mach4/Mach3

« on: June 19, 2018, 08:41:32 PM »

Hi,
a Widows 10 version comparison:

http://wincom.blob.core.windows.net/documents/Win10CompareTable_FY17.pdf

Craig

4266

Mach4 General Discussion / Re: Computer to run Mach4/Mach3

« on: June 19, 2018, 08:38:03 PM »

Hi,
it would appear that the Enterprise version of the LattePanda 4G/64G is still available:

https://www.dfrobot.com/product-1585.html

and for $209....

Craig

4267

Mach4 General Discussion / Re: Computer to run Mach4/Mach3

« on: June 19, 2018, 06:43:36 PM »

Hi,
yes I notice that the OS variant has changed. as of a month or so ago the LattePanda was advertised as
being shipped with Window 10 Enterprise, the Enterprise variant allowed you to turn off updates.

I am not interested any more in a parallel port, of no use whatever with Windows 10. I do like the built
in Arduino though.

Craig

4268

Mach4 General Discussion / Re: Implementation of physical buttons

« on: June 19, 2018, 06:39:10 PM »

Hi,

I am assuming this list will be like the DoOEMbuttons from mach3?

No, I don't think so.
Open the screen editor and look at the 'Action' property of some of the buttons, the jog buttons for instance.
If you click on it you will find a drop down list of stock actions. Nice to have a look at but not particularly useful
just at the moment.

You really need to set up input pins with the ESS plugin and then put functions/actions in the SigLib table.

Craig

4269

Mach4 General Discussion / Re: ESS + Mach4 + Clearpath = Motor error input goes where?

« on: June 19, 2018, 03:19:58 PM »

Hi,
if you stand back a bit from your system consider this:

If you issue a step change in position to your machine it will attempt to drive to the new location. If you have set the following error window wide enough that it doesn't
fault at least! The machine will approach its new location and may overshoot and the return for another go.

In classical control engineering parlance that behavior is described by two numerical variables:
OmegaN(atural) which is a measure of the speed of the response of your axis, generally the faster the better and
Zeta the damping figure, 0 is no damping and the machine overshoots wildy, 1 is slightly overdamped and it doesn't overshoot at all, and 0.7071 damping is considered optimal.

These two figures will allow you to calculate the maximum following error for any given input. You may have seen these figures of merit when talking about a servos PID ability.
and its closely related. The dynamics of the servo will be changed by the mass and friction of the axis that the servo is bolted into. Thus if you can calculate OR measure
the dynamics of your axis you can determine the absolute error for any given input. As it turns out calculating it is not easy unless you have very good and extensive
information about your servo/axis. Measuring it is a realistic alternative but will require a sophisticated setup.

Craig

4270

Mach4 General Discussion / Re: Computer to run Mach4/Mach3

« on: June 19, 2018, 02:57:28 PM »

Hi,
that's really good value....

A new PC with Windows 10 preinstalled (4G/64G):

https://www.lattepanda.com/products/3.html

Craig