Jump to content
OMRON Forums

Commanded velocity fluctuation


ulhasfegade

Recommended Posts

Firmware version:2.6.1.0

Controller: CK3M

Servo update frequency 4KHz.

 

In my machine B axis is defined as

#5-> 1#5->5965233B

Coord[1].FRAxes = $1C0  //XYZ
Coord[1].FR2Axes=$0

I am commanding as per the following program.

G01 B0 F1000

dwell 500

B-10

dwell 500

B0

When I plot graph for commanded velovity and acceleration, it shows velocity is oscillates after  acceleration is complete. Due to these fluctuations, acceleration feed forward is also fluctuating and creating noise in the motor.

Can you suggest what should the cause?

 

 

image.thumb.png.82a71129ed112f4f6d4cb06d8d589cc0.png

Link to comment
Share on other sites

  • 2 weeks later...
  • Replies 10
  • Created
  • Last Reply

Top Posters In This Topic

  • 5 weeks later...

I have conducted following two test on other motor

1. When the acceleration is restricted to 60mm/sec^2, the commanded feed of 2000mm/min only reaches a maximum value of 1741mm/min with ripples.

2. However, If a feed of 1400mm/min is set instead, the velocity reaches the commanded value without any additional fluctuations.  

I could not understand why in case 1 motor does not reach to commanded feed.

 

image.thumb.png.993216ccd23c84fd1f0aa7a03670ebc6.png

image.png

Link to comment
Share on other sites

If I increase the acceleration from 60mm/sec^2 to 100mm/sec^2, then it is able to reach to 2000mm/min ( I have set Coord[x].Ta=0 ,Coord[x].Td=0 ,Coord[x].Ts=0.02 with segmentation enabled). Acceleration is changed with Motor[x].InvaMax.  It looks like that some other parameter is limiting the maximum speed other then Motor[x].InvaMax.

Link to comment
Share on other sites

  • 4 weeks later...

Why do you say that it looks like some other parameter is limiting the maximum speed, other than Motor[x].InvaMax?  If increasing Motor[x].InvaMax from 60 to 100  mm/s^2 allows the max speed to be reached, isn't that the parameter that was limiting the speed?  By the way, being that this is "inverse of maximum acceleration" increasing from 60 to 100 is affected by changing the value from 0.017 to 0.01 (1/60 to 1/100), right?

Link to comment
Share on other sites

  • 2 weeks later...

1. As I could not see any logical reason for INVAMax limiting the maximum speed. It can only increase the acceleration time. 

2. We have axis assignment as #1->#1->1677722X, and calculated INVAMax for 60mm/sec^2 and 100mm^sec^2 based on this. 

I request you to simulate at your end

 

 

Link to comment
Share on other sites

Too much acceleration limiting (big acceleration times or low acceleration values) will also limit motor speed. The motor does not have enough “time” to reach programmed velocity.

image.png.f4798b876a1096c0804008a905c7035d.png

See the “Power PMAC User’s Manual” in the subsection “Acceleration Specification” (677) under section “Linear Move Mode” starting on page 672.

image.png.f94433438d7ac7fa85f58741653e62b2.png

 

Link to comment
Share on other sites

I could understand this topic. Case  explained in the manual is with less distance   where motor must start to decelerate to reach and stop at programed point. But in this case, there is large travel distance is programed so that axis can reach to programed velocity.  See the graph below. I have programed the velocity of 2000mm/min but it could only reach up to 1741mm/min and it continues with that velocity for quite some time before starting to decelerate. Also velocity is not constant at 1741mm/min but have lot of oscillations. 

Only one motor is programed in this case and no coordinated movement with other axis.

 

image.png.65395ca0e249a943235e6806142d7693.png

Link to comment
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...