Messages

3981

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 20, 2018, 02:39:42 AM »

Hi Mick,
in recent years entry level  PC based oscilloscopes have become very very much cheaper and yes something like an Arduino could be pressed into
service. The technical requirements for an oscilloscope for tuning servos is fairly modest and you could very easily get a highly useful PC based instrument
for less than 100 pound, such instruments will often have a built in programmable signal generator.

I may do a little searching around and try to make some sensible recommendations for you.

Even with a suitable instrument you will have to learn to use it and then learn to apply the information obtained from its use to tune your servos.
That is not for the faint hearted, to make sense of things you will be required to be absolutely familiar with diagrams of the type I posted earlier.
Not only will you have to understand them but do some basic calculations with the data obtained.

Depending on your inclination it could be a fascinating learning experience which you may enjoy.....well within the parameters of a challenging and rewarding
hobby......or it could put you off for life!!

Craig

3982

General Mach Discussion / Re: Inches vs. MM

« on: July 19, 2018, 09:20:49 PM »

Hi,
you've posted in the Mach4 section of the forum, you'll get better results in the Mach3 section.

Have a look at Config/Native units. What are they?

Have you referenced (homed) your machine PRIOR to engaging soft limits?
Do you have home switches that even allow you to reference (home)?

Display table mode only works when soft limits also works, ie the machine is referenced.

These last two issues are related.

Craig

3983

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 19, 2018, 05:43:30 PM »

Hi Mick,
if and how much improvement could be had is at best a wild guess, I would say that you could improve the
underlying servo velocity loop by 50%.

Given that you have followed written instruction only I think you have achieved a good result. To do better
you will need a scope and sig-gen to inform your tuning. While you could use the CSMIO scope and Mach/CSMIO
as a signal source I suspect the confusion that it would generate would make any gains difficult.

If I were doing it I would use my signal generator to produce a step signal, actually a 10V amplitude square wave
of period 10sec, and observe the error with the scope. I would be looking to improve the speed of response
with a 9% overshoot (sometimes called the Gibbs overshoot). RV2 would be left wide open. The tuning would be
principally done with RV1 (tacho gain) and RV4 (stability). Thereafter I would use my signal generator to produce a sine
wave and measure and plot the Bode frequency response and therefore deduce the gain and phase margins.

Does any of that sound familiar to you? If not then I suspect trying to do it by forum post will drive you up the wall!
I think your existing solution is good enough. You might in time come back and revisit it but I would suggest you move on
to other matters and make some chips.....

All in all I think you are to be congratulated on the result you have achieved given your unfamiliarity of feedback
control systems.

Craig

3984

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 19, 2018, 03:13:13 PM »

Hi,

The forward gain does seem rather low suggesting the amp or motor may be at fault in some way

I agree, I'm of the opinion that the velocity loop is still a long way short of where it could and should be.
Consequently the CSMIO tuning just makes the best of what is rather than the best of which it is capable.

Describing the tuning process has not been effective, and a signal generator/scope is indicated. In absence of that then
the performance of OPs current settings will have to be deemed adequate.

Craig

3985

Mach4 General Discussion / Re: work zero in mach 4

« on: July 19, 2018, 02:56:25 PM »

Hi,

I have limit switches that i use as a home switch as well. Is that not a good idea?

My preference has always been separate home and limit switches although the vast majority of users combine them. I understand you use a
UC100 which does not have many spare inputs so you'll probably be required to combine them.

I have an ESS and so have plenty of inputs and have individually wired switches, because I can. It works extremely well with no operator
confusion.

Craig

3986

Mach4 General Discussion / Re: variable

« on: July 19, 2018, 09:17:15 AM »

Hi,
sorry, hadn't tested it properly....I needed to convert regvalue back into a string to use mcRegSetValueString() and also
had a typo in the path to your new register.

Code: [Select]

function m150()
local inst=mc.mcGetInstance()
local hreg=mc.mcRegGetHandle(inst,'ESS/Encoder_0')
local regvalue=mc.mcRegGetValueString(hreg)
regvalue=tonumber(regvalue)
regvalue=(regvalue*5)/1.141
regvalue=tostring(regvalue)
hreg=mc.mcRegGetHandle(inst,'gRegs0/newreg45')
mc.mcRegSetValueString(hreg,regvalue)
end
if (mc.mcInEditor()==1)then
m150()
end
Each time you MDI m150() the procedure will occur.

Craig

3987

Mach4 General Discussion / Re: variable

« on: July 19, 2018, 09:04:38 AM »

Hi,

and divide by

Divide by what? I substituted a number 1.141 just as an example.

First you need to create a new register.

Go to Configure/Plugins/Regfile click on the Global Regs  and then the green cross to create a new global register. Type in a name
and an initial value, if you want one and whether its persistent, ie saved at the end of the session.

Now open the ZeroBrane editor and create this macro:

Code: [Select]

function m150()
local inst=mc.mcGetInstance()
local hreg=mc.mcRegGetHandle(inst,'ESS/Encoder_0')
local regvalue=mc.mcRegGetValueString(hreg)
regvalue=tonumber(regvalue)
regvalue=(regvalue*5)/1.141
hreg=mc.mcRegGetHandle(inst,'gReg0/newreg45')
mc.mcRegSetValueString(hreg,regvalue)
end
if (mc.mcInEditor()==1)then
m150()
end
Note because I don't have a CSMIO I called an ESS register 'Encoder_0', you would substitute the path to your CSMIO register.

Craig

3988

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 19, 2018, 04:59:52 AM »

Hi,

Was just following the Norwin manual with regards RV2.

I presume you mean this piece of the manual:

5.3.1 COMMAND GAIN
In some situations it may be necessary to scale down the command signal in order to reduce the
top speed of the motor. This is done by adjusting the potentiometer RV2 on the personality
module.

I contend that limiting the axis speed, as opposed to setting the axis speed in Machs tuning is not what is meant by 'In some situations it may.... '

Craig

3989

Mach4 General Discussion / Re: work zero in mach 4

« on: July 19, 2018, 03:53:56 AM »

Hi Ken,
if you don't have home switches, which I guess is quite likely as you are still experimenting, then if you hit <Ref All> the machine will
reference itself to its current location, sometimes called 'Home in Place'. That will mean that the machine co-ordinates of the current location
will be 0,0,0. The axis LEDs will go green, which informs you that the machine is referenced.

Referencing means MACHINE COORDINATES. They are what Mach (3 or 4) uses as native positioning but are not usually used by us, mere humans
that we are. For us we would jog to one corner of the material and the zero each axis. Note that 'zeroing' an axis is different to 'referencing' an axis.
When we 'zero' an axis or axes we are setting WORK COORDINATES. Work coordinates are much more user friendly, its easy to visualize 2 inches
from the left corner and 2 inches up from the left corner of a piece of wood you are working on say. Work coordinates are intimately related to offsets.
The offsets are the translation from Machine Coordinates to Work Coordinates and are used by Mach but seldom by us. Further if you follow the
procedure...reference (home) the machine, jog to the start of the job and then 'zero' the machine the offsets are automatically defined and stored.

Craig

3990

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 19, 2018, 03:34:09 AM »

Hi,
when you think about it servo drives have been getting smarter for many years.

Back in the 70's and 80's all servos were like Mick's. You needed a controller that could close the loop and apply PID dynamics.
In the late 80's digital servo drives became common where the drive could read an encoder and apply PID dynamics. That meant the controller
was not required to close the loop. Gecko 320 is an example of this idea. They work OK but are not particularly sophisticated, certainly not in comparison
to the CSMIO/P-A of our current debate, nor, in comparison to modern AC servo drives either.

In the 90's microprocessor technology had improved to the point that Field Oriented Control was feasible and has advanced rapidly ever since with increasingly
sophisticated control options. More recently still they are in themselves a single axis motion controller, able to apply limits and home autonomously. Strictly speaking
a  PC with realtime ethernet you could have a CNC machine without a motion controller at all, just a trajectory planner in the PC and motion control that is distributed amongst
the servo drives.

All of this points to the trend that servos and their matching drives are becoming evermore capable. I guess you might say that manufacturers are taking advantage
of the processing power of microprocessors/FPGAs/DSPs. I think the medium to long term prospects of highly sophisticated and expensive motion control boards
is poor as servo drives take the challenge.

Craig