Send continuosly position value to PLC without Multitasking

Hello,
I'd like to have your opinion about this application and its possible implementations.
A IRB4600 must check if the top layer of a pallet is full (there are no holes), i.e. it goes in the center of the pallet, do a SearchL until the ultrasonic sensor detect a distance < x mm (it measure the height of the pallet basically), then start a movement that could be a spiral with center the pallet's center or another movement that can reach all the points on the pallet top surface (still have to be chosen the best one). During this movement, the robot must send its position to the PLC, which is also receiving the values from the ultrasonic sensor; then the PLC compares all the values it is receiving and if all the ultrasonic sensor values are similar then it means the top layer of the pallet is full. 
The robot has not the Multitasking option.
So I have thought to 3 possible solutions:
1) During the movement, I activate a temporal trap routine that each 0.x s send the position to PLC
2) Perform the movement as a series of close MoveJ, at the end of each of them I send the position to PLC
3) Buy Multitasking option

I'd like not to buy Multitasking, but maybe in the first 2 cases the computational load could be high. Or maybe, considering that it would be just for a short movement, it can still be a good solution.
What do you think?

Comments

  • matti
    matti Germany
    Hallo,
    why not making that decision on the robot controller without PLC?
  • They want the PLC to do everything, it's a given project's requirement. Moreover all the sensors are direct input of PLC.
  • Newman
    Newman Sweden
    I would try a time interrupt at 0.1s.

    Or a bunch of MoveLSync’s.
    -----------------
    David
    Swedish freelance ABB robot programmer
  • EricH
    EricH Germany
    So, you want to check not only the height of the pallet, but also whether the surface on the side is within parameters?

    Is an ultrasonic sensor suitable for this application? Maybe a distance sensor with a laser would be more suitable.
  • Yes, I have to check if they put a pallet with layers without "holes", there must not be missing boxes in the top layer at the start.
    Unfortunately the ultrasonic sensor is what we have, but I think it is enough.