Author Topic: csmio/a offset problems  (Read 2210 times)

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Offline peterklos

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csmio/a offset problems
« on: July 03, 2016, 12:12:26 AM »
Hi I am trying to tune a CSMIO/A to a analog servo motor and the offset value on the PID tune  is randomly  changing from .012 to around  +3v , i can see this on my CRO their is no axis command during this time .
Any ideas
Peter

Offline Hood

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Re: csmio/a offset problems
« Reply #1 on: July 03, 2016, 03:52:45 AM »
Do you have the Vel in Machs motor tuning set to an equivalent value to that of the rpm for 10v set in the servo drive?
If there is a big difference then you will find it extremely hard, if not impossible, to tune.

What I mean by the above is

If you have the servo drive set to 10v = 4000 rpm and you gearing between motor and drive is 2:1 and your screw pitch is 5mm then for 10v the motor will move at 4000rpm so Velocity in motor tuning needs to be set to 4000/2 x 5 - 10,000mm/min.

If you have the motor tuning set to less then you will have problems. For example if the motor tuning was set to 5,000mm/min then the CSMIO will expect that the motor will do 2000rpm when it gets 10v but the drive will be turning the motor at 4000rpm. That will mean the motor shoots off faster than the IP-A expects so it applies an opposite command to try and control but the motor shoots off the opposite way and the IP-A then tries to bring under control and it shoots off the other way and so it continues.

Hood

Offline peterklos

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Re: csmio/a offset problems
« Reply #2 on: July 04, 2016, 02:22:36 AM »
Hi Hood , thanks for the reply looks like on the CSlabs posts you have the bull by the horns and your knowledge is appreciated , my project is retrofitting a very large cnc , its mass is around 8 ton and the x axis  gantry about 3 ton so which is exciting when the P gain goes into a 3 ton oscillator  ! i think the problem i have is that the AC brushless drives are very large and their is a huge amount of EMF and harmonics from the 3 phase 425 v supply  which is stuffing up the pc and CS labs system , I have experience with many retrofits ( Linux EMC and Fanuc ) but tuning this one has been a night mere. I am not sure like like the idea of 3 stages of PID gain / command positioning and acceleration   , 1 in the servo drive , 2 in CS labs , 3 in Mach3 each one has an influence on each other , and if you dont start with a snappy well tuned servo drive its points less continuing. i am looking at big front end filters and decoupling the supply rails . thanks for your help . Peter

Offline Hood

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Re: csmio/a offset problems
« Reply #3 on: July 04, 2016, 02:55:01 PM »
Don't really have any tuning in Mach, just values for accel, Vel and Steps per unit and they are all fixed. As for the others (drive and IP-A tuning) , I would imagine that would be needed for any controller if using Velocity control.

Hopefully the filtering will help, let us know please.

Hood