Dynomotion

Group: DynoMotion Message: 10691 From: troy_ojalehto Date: 12/18/2014
Subject: Kflop with Kstep Resonance help needed

Hi Tom,


I also posted this to the cnczone forum but wanted to post here also as you seem to write a lot in this one.


I'm building some 4 axis gantry style machines with Kflop + Kstep in closed loop stepper mode. XY axes have 270 oz-in 2.8A steppers wired in series with 900CPR (3600 ct) encoders and 5mm pitch ball-screws connected with flexible alum couplings. Everything works great except I am experiencing some resonance at low velocities in XY that cause some undesirable vibrations when doing certain slow moves, especially interpolating circles. I have attached a screen shot of the normal step response plot at normal max vel as well as a plot with the velocity limited to 4000 to cause it to stay in the resonant range-The heavy blue banding shows the resonant area. I'm currently using Low Pass 2nd filter at 110 Hz Q1.41. Have also tried adding a notch filter at 4000 Hz 1 damping, to no effect. (Assume velocity of 4000 steps per sec equates to 4000 Hz?) Have also played with other filter combos without having any effect on the resonance. Problem persists with PID values all set to zero also.


Is this mid band resonance?

Can someone recommend an IIR filter or other settings that might address this? Switch to a different coupler style?


Thanks!

Troy

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Group: DynoMotion Message: 10693 From: Tom Kerekes Date: 12/18/2014
Subject: Re: Kflop with Kstep Resonance help needed [2 Attachments]
Hi Troy,

Interesting problem.   See my reply on cnczone:


Regards
TK
 

Group: DynoMotion Message: 10709 From: Tom Kerekes Date: 12/22/2014
Subject: Re: Kflop with Kstep Resonance help needed [2 Attachments]
Hi Troy,

Were you able try the method we posted on cnczone?

Checkout the video
 
Regards
TK

Group: DynoMotion Message: 10713 From: az@aimele.com Date: 12/23/2014
Subject: Re: Kflop with Kstep Resonance help needed
Troy:
Are your couplings aluminum with a spiral cut?  If so, I've found that this type of coupling has too much torsional spring and in many cases gets to it's resonance too easily.  If so, you may be best served by using a coupling with more rotational stiffness  like a Zero Max disc coupling or possibly an accordion coupling like a R+W  or even a jaw type coupling like a Guardian Curved jaw.

Good Luck.
AZ



------- Original Message -------
From : Tom Kerekes tk@... [DynoMotion][mailto:DynoMotion@yahoogroups.com]
Sent : 12/18/2014 12:30:32 PM
To : DynoMotion@yahoogroups.com
Cc :
Subject : RE: Re: [DynoMotion] Kflop with Kstep Resonance help needed

 

Hi Troy,

Interesting problem.   See my reply on cnczone:


Regards
TK