Kinetix Auxiliary Feedback

[consol 0]

Hi, I've an application as follows: ControlLogix L62 Machine with 7 Servos running from Kinetix 6000. An encoder connected to the auxiliary input on one of the Kinetix drives. This encoder returns a 0-360 deg rotation position. I'm using this encoder to activate different devices (solenoids, rotary index table). I'm using the LIM instruction, with the encoder feedback as input, to activate a flag that operates a relay controlling a rotary index table. However, there seems to be a lag on the encoder reading. (I'm about 10degrees too late when triggering outputs) I'm wondering if I'm addressing the encoder feedback properly. The encoder is connected to the aux input of a feedback only axis. (ENC03) I'm addressing this as ENC03.AuxPositionFeedback. The Aux Position Feedback is selected as a realtime attribute on the axis. Is this the fastest method of retrieving the position feedback? Is there a better way to do this kind of application. I've looked at the MAOC function but I'm not sure how to use it. I'd appreciate any advice or help you guys can give. Thanks, Tim

[ElecPneuGuy 1]

You might get a lag as the Kinetix system processes the encoder feedback and gets the feedback to the processor. Might be a scan time issue... What I do for encoder feedback is use an encoder on DeviceNet. Seems to work really well. But to be faster, as I understand it, use an AMCI module. The data in decoded in the card itself and is not scan time dependent.

[consol 0]

This is the conclusion I'm coming to. I'm a bit surprised. I thought the realtime attributes were just that: 'real time'. The rotation that I'm looking at is not really high speed, approx 95 rpm. I'll look in to the AMCI unit. My client wants to avoid any type of bus system (unfortunately). Thanks, Tim

[TimD 0]

For the best performance, you'll have to use the MAOC instruction and if possible, use an outputcard directly linked to MAOC instruction. Is the task already running in a fast periodic task (with an update rate of ex. 2ms?)

[consol 0]

Yes, I've a periodic task at 1ms. Current scan time is 4ms. There's very little in the program at the moment. Do you have any example of the MAOC? I tried using it but couldn't get the CAM window to synch with the encoder. (0' on the CAM was 40' on the encoder) Wouldn't the CAM outputs update have the same issue as the encoder update? How do I link an output card to the MAOC? Thanks, Tim

[WildPointer 0]

If you are at 95 rpm this would equate to 95 rpm / 60 seconds * 360 Degrees / 1000 ms/sec = 0.57 Degrees /Millisecond. Therefore a 10 degree error is 17 ms of lag. I believe that your encoder signal will only update at your "coarse update rate". You might want to look at this. ( Property Of Motion Group ) Also have you checked the RPI of your output card. ( Property of your output card ) Just a couple suggestions.

[consol 0]

Hi, The coarse update rate is at 2ms and I've set the RPI of the output card to 2ms. I've checked the contactor circuit... but will take another look at it in the morning. Thanks, Tim

[consol 0]

OK... (Red faced here) Problem was the contactor. 24VDC coil had a 10-15ms lag on disconnect! Switched to an AC contactor and I'm getting an immediate stop. So, sorry for the wild-goose chase and thanks for all the help. Tim