"Invalid node remove command" at UNLOAD

Hi all,

in my model I regularly get an "Invalid node remove command" when a robot unloads a part to a pallet.
Does it mean that the node "part" cannot be removed from the robot? Has anybody an idea what could be the reason for that?

Many thanks and best regards
Lydia

Hi Lydia,

usually the invalid noderemove command is rised when Flexsim try to delete a node that has been previously removed. Probably you writed some trigger in your model that delete something that Flexsim try to delete subsequently.

Luciano

Hi Lydia, I looked at your model. You have a robot removing parts from a standard conveyor which is causing the error because of the situation Luciano described. When you remove (steal) an item before it has reached the end of the conveyor, the outstanding event related to that item on that conveyor still lives. For a while objects will steal the item back and forth in your model but eventually after the item reaches a sink, the last object to have the item stolen from it will be puzzled why the item no longer exists.

Options to replace the conveyor
1. MergeSort Conveyor
2. BasicConveyor
3. TaskExecuter that travels to infinity
4. BasicFR with an object inside of it that moves by kinematics

I have attached an example of the 4th option, I call it a simple conveyor because it is straight and is not designed to be blocked (no accumulation logic). Early in the model run you can see the object I call "Belt" (nested inside the SimpleConveyor) when it travels out of the model view to infinity. There is a Control GUI button to write a task sequence to pick an item from the conveyor.

Thank you so much, Kris!

I substituted the Conveyor by a MergeSort Conveyor but am still having problems, namely
- If I add a sink to the output port of the conveyor in order to destroy the parts not picked, the parts go directly into the sink when arriving at the Conveyor!
- If I do not add a sink, the parts stay alive after leaving the Conveyor. They seem to cause problems then.

How could I resolve this?

What do you mean by:

Originally Posted by Kris Geisberger

For a while objects will steal the item back and forth in your model ... the last object to have the item stolen from it ...

Many thanks again and best regards,
Lydia.

Hi Lydia, you might want to refer to the users manual MergeSort page. You have to specify fixed entry and exit points for each input and output port connection. I assumed fixed points would be too limited for you, and in order to get a task executer to pickup from the MergeSort you would likely have to use a queue and some fancy code to get it to behave the way you want. My recommendation is to use the BasicFR solution I attached in the original post, I just included a v4.52 model as well so you can have a look.

To answer your second question I have attached a model showing the "stealing" effect I was referring to. Execute the code in the script window when there is an item on the conveyor to pick. Again, this happens because we remove the item without removing the event associated with the item and the conveyor... this event marks the end of travel on the conveyor for the item. You will get the invalid node removal error if you connect sinks after the queues in the model.

All that said, one might suggest calling destroyeventsofobject(conveyor,-1,0,NULL,item) just after (same time as) picking an item from a standard conveyor, but there could be situations where this may not work so use caution if you do this.

Thank you very much, Kris!

Now I decided to substitute the sink for parts with a queue with huge capacity and to keep the standard conveyor, which works fine. (If I try to destroy the parts in the queue, though, the old problem occurs.)

By the way, is the destroyeventsofobject command mentioned somewhere in the users manual?

Thanks a lot again and best regards, Lydia.

It's in the Command Reference in the user manual:

destroyeventsofobject(obj object [, num simtime, num code, str data, node involved])

Description: Destroys events associated with the given object. The first parameter, object, is the only required parameter. Other parameters are optional and provide a filter for choosing which events to destroy, as follows:

time: If greater than or equal to the time that that the command is called, this parameter will filter events by their time. If the event's time is not equal to the time passed in, then the event will not be destroyed. Pass -1 if you don't want this as a filter.

code: If greater than 0, this parameter filters events by their event code. If the event's code is not equal to the code passed in, the event will not be destroyed.

data: If not NULL, this parameter filters events by the data string associated with the event. If the event's data string is not equal to the string passed in, the event will not be destroyed.

involved: If not NULL, this parameter filters events by their involved node or object. If the event's involved node is not equal to the node passed in, the event will not be destroyed.

Example: destroyeventsofobject(rank(model(),2))


greetings

Carsten

Hi Carsten,

thanks, but where can I find the Command Reference (sorry, maybe stupid question ...)?

Best regards, Lydia.

Hi Lydia,

just open the Flexsim users manual (Help > Users Manual). On the left side is a tab called Content (or Inhalt if you are using a german windows). The third chapter from bottom is Command Reference.

Another way is "Command" in the help menu. But in this case you get only the alphabetical index.

If you are looking for a special command you can use the short cut STRG+F to search inside the view of the commands.

greetings

Carsten

Many thanks, Carsten.

Originally Posted by Carsten Seehafer

Another way is "Command" in the help menu. But in this case you get only the alphabetical index.
If you are looking for a special command you can use the short cut STRG+F to search inside the view of the commands.

This works fine, and there is even a "Categorical" section!

Originally Posted by Carsten Seehafer

just open the Flexsim users manual (Help > Users Manual). On the left side is a tab called Content (or Inhalt if you are using a german windows). The third chapter from bottom is Command Reference.

I cannot find this, maybe due to my version (4.52).

Best regards, Lydia.

I wasn't aware that you are using version 4.52. In 4.52 the commands list has a "Categorical" section but it isn't in the users manual.

I've made a screenshot of the users manual in 5.1.2