topic Re: Find Nearest Open Slot Exception in FlexSim Forum

Find Nearest Open Slot Exception

amit_k2 — Wed, 04 Nov 2020 19:59:45 GMT

[ FlexSim 20.2.3 ]

I'm modifying the logic from this post to find the nearest slot in multiple racks that use AGV network. But I end up getting following error, perhaps due to queries that I am using while finding a storage slot. Also @anthony.johnson mentioned to use Vec3.project() method to query multiple racks, which I don't know how do. Any pointers are appreciated. Sample model is attached.

time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Find Nearest Slot>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Find a Storage Slot>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Which Rack?>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Slot Placement Strategy>variables/codeNode
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Find Nearest Slot>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Find a Storage Slot>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Which Rack?>labels/1/2
time: 120.000000 exception: FlexScript exception: MODEL:/Tools/ProcessFlow/ProcessFlow/Slot Placement Strategy>variables/codeNode

NearestSlotTwinForkAGV_11.4.2020.fsm

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Thu, 05 Nov 2020 15:13:35 GMT

The project method of a location just finds the point in 3D space relative to another object - and it takes two parameters in the example the FromObject and the ToObject. By setting the ToObject to model() it's asking for the absolute location in model space and not relative to the containing object/Rack.

By subtracting one location in model space from another you get the vector between the two - and the magnitude of that is the distance between them.

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Thu, 05 Nov 2020 15:39:18 GMT

I've altered the queries to this but it's still causing an exception

You appear to be using findSlot to assign the token label slotItem, but that's probably going to be a slot, while parameter two above is clearly assuming it's a slotItem.

Re: Find Nearest Open Slot Exception

amit_k2 — Thu, 05 Nov 2020 18:45:58 GMT

@jason.lightfoot Thanks for the response. Here is what I changed based on your latest comment :

1. Find a Storage Slot now assigns to token label MySlot, which I assume is a slot. and made corresponding changes to where this label is used.

Query 2 in above image checks all racks in the model that have label "Active" with value 1. Do I have to modify this to find an empty slot in any rack with the project method? Also, the label "MySlot" is used to define the rack to which it belongs and set destination for the AGV to drop off.

After running the model, along with the exception, I now get a invalid FlexScript code error in Query 2 in "Find Nearest Slot" activity.

Invalid FlexScript code: ((param(1).as(Storage.Slot).project(param(2).as(Storage.Slot).StorageObject,model())) - (param(3).as(Storage.Slot).location.project(param(4).as(Storage.Slot).storageObject,model()))).magnitude

Do you think the way "Which Rack?" and "destination" activities are defined are causing this issue?

NearestSlotTwinForkAGV_11.5.2020.fsm

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Thu, 05 Nov 2020 18:57:06 GMT

Attached is a version of the model without transport assigning to closest free slot across two Racks.

nearestslottwinforkagv-1142020_jl_4.fsm

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Thu, 05 Nov 2020 18:58:17 GMT

I've changed a few things that were not needed or missing - see the other comment with the model attached (ending jl_4.fsm)

Re: Find Nearest Open Slot Exception

amit_k2 — Thu, 05 Nov 2020 19:56:22 GMT

I really appreciate your help on this topic and I now better understand what you did with the queries.

Any reason, why you removed the transport logic in this model? When I added the AGV logic, the pallets disappear when the AGV arrives at the loading point and the model crashes. This logic is part of a bigger model and the AGV functionality is a key part of it.

NearestSlotTransport.fsm

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Thu, 05 Nov 2020 23:25:30 GMT

Yes - with the transport in place, the search for a matching slot-item wasn't finding anything. I'll try and get to the bottom of why that is.

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Fri, 06 Nov 2020 17:55:35 GMT

This is not looking good - it seems the logic is finding the same slot due to the fact the item first assigned to the slot has not arrived. Current state uploaded.nearestslottwinforkagv-1142020_jl_6.fsm

Re: Find Nearest Open Slot Exception

amit_k2 — Fri, 06 Nov 2020 19:12:05 GMT

Thank you for the response.

I now suspect that for the labels below on the second pallet :
1. slotItem has no path
2. matchingSlot has no path

and that might be leading to crashing of the model.

FindNearestSlot_Crashing_AK_1104.fsm

Re: Find Nearest Open Slot Exception

joerg_vogel_HsH — Fri, 06 Nov 2020 19:51:37 GMT

Hi Jason, there is a condition, you must set to assign a slot that it gets reserved.

The query must limit the items physical to enter the slot wether by hasSpace method or length property. HasSpace implies an item in storage system with known dimensions of size.

I had a similar problem, when I tried to find slots and hold them only as data at tokens. Slots can store an unlimited amount of items without a size.

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Sat, 07 Nov 2020 12:25:19 GMT

Thanks @Jörg Vogel - we already have that accounted for in our queries - the plot thickens....

Re: Find Nearest Open Slot Exception

jason_lightfoot_adsk — Sat, 07 Nov 2020 12:32:42 GMT

In the ..jl_6 model, the second pallet's token get's these label values where the matching slot is the same as the found slot

This is correct as the depth of the slot is the ysize of the storage object

The crash is something to do with using the AGVNavigator for offset travel on the load/unload task with the rack's pick face not facing the control point. If you select another option or rotate the pick face towards the control point then the crash doesn't happen. I'll create a bug report for this aspect.

Attached is an updated version.

nearestslottwinforkagv-1142020_jl_7.fsm

Re: Find Nearest Open Slot Exception

amit_k2 — Sat, 07 Nov 2020 23:05:10 GMT

@jason.lightfoot Thanks! About the crashing, I had ran into a similar problem while working on other parts of my actual model and @Phil BoBo mentioned that - "the AGVs offset travel code is getting into a stack overflow error, since the AGV is not doing any offset travel, the simplest solution is to turn it off." I hope this helps with the debugging.

Also, finding a matching slot and assigning the destination using a ternary operator to the item would work if there are only 2 racks in the model. How would I go about extending this to multiple racks? Perhaps, using the matching slot as a storage object?

Thanks again for the help!