Help needed in reversible conveyor

Hi everyone. I am trying to build a conveyor system, which the first section of it is a reversible conveyor.

I used 2 conveyor which placed on the same position to simulate the effect, and they move in opposite direction.

There is an ASRS which transport objects to the conveyor by tasksequence A, then pickup the objects reaching the end of conveyor and store them back in rack, by tasksequence B.

But my model got some error, which the tasksequence B stopped in the middle of simulation. If I replace the tasksequence by a direct reference to the ASRS unit, the problem solved, but I want use tasksequence in this case, as I want to perform pick / place offset function.

Does anyone know how to solve this problem? Or anyone got any hints on how this problem happens?

First of all, you should tell the ASRS vehicle "Do not travel offsets for load/unload tasks" in the parameters window, because you are manually telling it to travel the offsets in your tasksequence. This is redundant and might cause problems.

Now for the real problem. I noticed that the tasksequence B (transporting into the rack from the conveyor) is stopped being called because the input port of the rack is blocked, not because of any conflicting tasksequences. I also noticed that when you set the maximum content of the Rack to be 1000, it is not blocked anymore. PLEASE don't use this as your solution, because it doesn't solve the source of the problem. Read on.

A Rack is a Fixed Resource. To determine whether a FixedResource is full or not, it keeps track of how many objects are in the FixedResource, how many objects have requested transport out of the FixedResource, and how many objects have requested transport into the FixedResource. When deciding whether to be full or not, the FixedResource calculates its "content" by something similar to this:

getvarnum(current, "nroftransportsin")+content(current)

You're using TASKTYPE_LOAD and TASKTYPE_UNLOAD in your tasksequences, which do not correctly update nroftransportsin or nroftransportsout. If you use TASKTYPE_FRLOAD and TASKTYPE_FRUNLOAD instead, then these variables are correctly updated, and your tasksequence works like you think it should.

The solution works fine.

One more thing, is there any means to check if the ASRS is doing a tasksequence? I would like to block the backward conveyor when the taskexecuter is going to pick up a item.

Thanks for your kind help!

You could put in a sendmessage task in your tasksequence and on that message block the conveyor. And a second sendmessage could resume the conveyor again.

Steven

Thanks for your help, Steven. This method works.