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Stop request during PTO acceleration causes PTO to freeze

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Have anyone noticed that if you request Stop PTO when it's still in acceleration mode it is very likely the module will freeze. Motor comes to immediate stop, but Current Velocity tag will stay at "Min Velocity" value.
PTO is then unresponsive to PTO move requests and controller usually needs reset.

This issue is present only when PTO stop mode with deceleration is selected. If Stop mode is "Halt" (immediate stop), this wont happen. 

On the oscillogram you can see that after PTO freezes, velocity tag stay above 0 while the Motor is actually still.
"Busy" bit in PTO Move block remains 1.

This is really problematic, since it's very likely to get PTO into this state with short moves (when PTO is near 0 absolute point) or with hand jog short movements.
This freeze issue will never happen if PTO stop request is sent when PTO is at it's target speed.

I attached simple test program where this issue can be reproduced imediatelly... If button "Start/Stop Move" is pressed for a short amout of time,  PTO will get stop request at "Problematic Speed" which will freeze PTO.

Is this a bug?


USC-B10-B1 Testni projekt.ulpr

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  • 4 weeks later...

I opened the ticket on 25jun, with the simple code attached where bug can be reproduced 100% of the time,  got an answer to upgrade PLC FW which should solve the issue.
As expected it didn't, so I wrote them back a few times over the weeks. Still no answer.

This bug is blocking my project since using hand jog usually ends in freezed PLC.

I highly discourage using PTO option on UID0808THS with UniLogic SW, because I found 2 bugs on my first simple project, which left me with bunch of time lost on programing and discovering what is going on and probably in the future investing money in another solution.

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Hello Rivka.

I appreciate the effort of your team, but the fix was just partial and in very limited way of use, so my experience and opinion arround PTO use haven't changed much -  currently it is not suited to be used at any application.
I'm in contact with Nir Manor sending him example programs where PTO freezes. 

After applying the fix you sent there are lots of bugs left:
- PTO also very likely freezes if you request PTO move to 0 (absolute move) and send a "Stop" request when the motor is already close to 0 position and so decelerating.

- When motor is very close to 0 (absolute move) and you request PTO move to 0 it will first time give Move error (with Err ID7 - not enough pulses to move), but if you request PTO move to 0 again, motor will overshoot the 0 point by large amount of pulses - prety easy to crash the machine this way."

PTO freeze when Dec. time is shorter than Acc time and PTO stop request is sent while PTO is still accelerating.

PTO freeze when ACC/DEC times are the same (but higher value  - ca 800ms) and stop request is sent right after PTO starts acceleration

What I'm writing here are not edge cases, but normal use of hand jog function.
Hope all this bugs get to be resolved soon... 



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