Moves not getting to position

Moves not getting to position

We have an odd situation with an MC4N running EtherCAT drives.
The issue is that axis 1 is not getting to the commanded position via MOVEABS.

The command MOVEABS is where we are hanging because the move seems to cancel.

We did a the test with all programs stopped, and issuing commands at the Terminal #0 prompt.

DPOS at 7.5.
Then I do a MOVEABS(0), and DPOS gets to and stops at 5.7.
Then I do a MOVEANS(-0.75). DPOS gets to -0.559 and the move stops.
After a few manual MOVEABS(1), MOVEABS(4.5), MOVEABS(0)…all seems ok again.

Note this does not happen consistently, and may take several dozen cycles to show up (this is a pick and place system).
Also, as far as I know, this is only happening on axis 1 of the 2 axis system. What could be causing it?

============================================================================================
We checked the program and axis settings and noticed that there are limit sensors allocated to FWD_IN and REV_IN. We suggested to check that the sensors are giving a solid signal and not intermittently going off during the moves.

An engineer visited the site and disabled the overtravel limit switches for the suspect axis. It ran for 1.5hrs with no issues!
The conclusion is that the limit sensors were triggering the FWD_IN and REV_IN inputs and cancelling the moves.

    • Related Articles

    • MOVEABS not ending in Target positon

      The cause the problem is that a MOVEABS takes ENDMOVE of the previous move as the start point. When we cancel the move in the MTYPE, it stops before ENDMOVE so it is not a valid start point any more. Here is a possible solution but it is not perfect. ...

    • Moving traverse from point to point repeatedly

      2 suggestions: 1. Move to positions BASE(0) REPEAT MOVEABS(position1) MOVEABS(position2) UNTIL event=TRUE 2. Move to sensor position1 and position 2 are set to be beyond the sensor postion BASE(0) REPEAT MOVEABS(position1) WAIT UNTIL IN(1)=ON CANCEL ...

    • MOVEABSSEQSP type problem

      Work out how many points per second are being executed in the MOVEABSSEQSP. If more than one per msec then that is not possible even with the MOVEABSSEQ type move. The other consideration is the vector length in the buffer. The LIMIT_BUFFERED value ...

    • AN-307 Move Embedded Parameters

      Move Embedded Parameters are a new feature within the Trio MC4XX Motion Coordinator system software. Each move can have up to 2 user parameters per axis pass through the motion buffers and become available during the motion for processing. The first ...

    • 'Forward' speed change during move

      FORWARD commands do not need to buffer. Just set FORWARD once and leave it running. You can change SPEED any time on the fly. SPEED set to 0 will stop the axis. A negative SPEED value will make the axis move in reverse. You only need to CANCEL when ...