Difference between revisions of "MC-Basic:axis.FOLLOWINGMODE"

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|DESCRIPTION=
 
|DESCRIPTION=
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This property puts the axis into following mode.
  
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When the drive is disabled, the position command (PCMD) is continually set equal to the position feedback.  In situations where the drive takes control over the motion of the motor (such as in drive-controlled homing), the axis must be explicitly put into FOLLOWINGMODE. Otherwise, the MC reports a position following error.
+
In a state of disabled drive, the position command (PCMD) is continually set equal to the position feedback. This state of an axis is called '''FOLLOWING MODE'''. When the drive is enabled again the PCMD sent will have the value of the last sample (when it was in following mode), so no jumps will occur.  In situations where the drive takes control over the motion of the motor (such as in drive-controlled homing), the axis must be explicitly put into FOLLOWINGMODE. Otherwise, the MC would report a position following error.
  
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This property put the axis in FOLLOWINGMODE. There are different modes of the follwing-mode:
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There are different following-mode types:
  
 
* hard-following (PCMD = PFB) automatically entered by the system when drive is disabled  
 
* hard-following (PCMD = PFB) automatically entered by the system when drive is disabled  
 
* user-following (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = 1)
 
* user-following (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = 1)
 
* soft-following (PCMD = PFB) same as hard-follwing (fmode=2)
 
* soft-following (PCMD = PFB) same as hard-follwing (fmode=2)
−
* user-following-BIT3 (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = -2) with drive's PCMD exit
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* user-following-BIT3 (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = -2) with drive's PCMD exit (fmode=-2)
−
* user-following-BIT3 (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = -3) with drive's PFB exit
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* user-following-BIT3 (PCMD = PCMD<sub>0 </sub>) freezing the PCMD value (not changing) (fmode = -3) with drive's PFB exit (fmode=-3)
  
  
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{{ Note/Important | Querying the fmode property returns 0 for regular working mode and '''1 for all other types''' of following modes!}}
 
  
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{{ Note | Be careful when setting following mode to 2, as it closes a loop around the position variable of the drive it can lead to instability - run away!}}
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{{ Note/Important |Querying the fmode property returns 0 for regular working mode and '''1 for all other types''' of following modes!<br>
 +
'''''There is now way to query the actual following-mode type!'''''}}
 +
 
 +
{{ Note |Be careful when setting following mode to 2, as it closes a feedback-loop around position variable of the drive. It can lead to instability - motor run away!}}
 +
 
 +
 
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{{Note/Warning|Disabling drive automatically activates '''''hard-following''''' mode from whatever mode the axis was previously in!}}
  
  

Revision as of 10:02, 23 November 2011

This property puts the axis into following mode.

In a state of disabled drive, the position command (PCMD) is continually set equal to the position feedback. This state of an axis is called FOLLOWING MODE. When the drive is enabled again the PCMD sent will have the value of the last sample (when it was in following mode), so no jumps will occur. In situations where the drive takes control over the motion of the motor (such as in drive-controlled homing), the axis must be explicitly put into FOLLOWINGMODE. Otherwise, the MC would report a position following error.

There are different following-mode types:

  • hard-following (PCMD = PFB) automatically entered by the system when drive is disabled
  • user-following (PCMD = PCMD0 ) freezing the PCMD value (not changing) (fmode = 1)
  • soft-following (PCMD = PFB) same as hard-follwing (fmode=2)
  • user-following-BIT3 (PCMD = PCMD0 ) freezing the PCMD value (not changing) (fmode = -2) with drive's PCMD exit (fmode=-2)
  • user-following-BIT3 (PCMD = PCMD0 ) freezing the PCMD value (not changing) (fmode = -3) with drive's PFB exit (fmode=-3)


For BIT3 see: SERCOS drive status word



IMPORTANT.svgIMPORTANT
Querying the fmode property returns 0 for regular working mode and 1 for all other types of following modes!
There is now way to query the actual following-mode type!
NOTE-Info.svgNOTE
Be careful when setting following mode to 2, as it closes a feedback-loop around position variable of the drive. It can lead to instability - motor run away!


WARNING.svgWARNING
Disabling drive automatically activates hard-following mode from whatever mode the axis was previously in!

Short form

<axis>.Fmode

Syntax

<axis>.FollowingMode = <value>

Availability

  • fmode = 0/1 - All versions
  • fmode = 2 From 4.4.2
  • fmode = -2/-3 From 4.9.0

Type

Long

Range

  • 0 –( Default ) When axis is enabled and the Position Error is monitored
  • 1 -When axis is disabled  or can be set by the user.  It freezes the PositionCommand.. And PositionCommand will update on the end (when user enters Fmode=0) by reading the IDN47 from the drive. (This can take some time as it is done through SERCOS service channel).
  • 2 -soft-following-mode, keeps PositionCommand equal to PositionFeedback .
  • -2 -user-following by (PCMD = PCMD0 )- drive status'-BIT3 control using AT cyclic telegram's IDN47 for new PCMD on exit
  • -3 -user-following by (PCMD = PCMD0 )- drive status'-BIT3 control using AT cyclic telegram'sPFB for new PCMD on exit

Default

0

Scope

Configuration, Task or Terminal

Limitations

To set the value within a task, the axis must be attached to that task (using the ATTACH command).

Examples

X_Axis.FollowingMode = ON

See Also

Retrieved from "http://softmc.servotronix.com/index.php?title=MC-Basic:axis.FOLLOWINGMODE&oldid=97818"