How to measure box arrival interval at an OutPort (Cycle Time) for a Dashboard in FlexSim?

[ayeong_jo]

Hello,

I would like to measure the arrival interval of boxes at an OutPort and display it on a dashboard in FlexSim.

My model is configured as follows:

-There are two Queues that generate boxes.

-Queue1: generates a box every 10 seconds

-Queue2: generates a box every 30 seconds

-An AGV transports boxes from the Queues to an OutPort.

What I want to measure is how many seconds pass between box arrivals at the OutPort.

For example:

Arrival time of second box – Arrival time of first box
= Cycle time (time interval until the next box arrives)

Using this value, I would like to display the following metrics on a dashboard:

-MIN CYCLE TIME

-AVERAGE CYCLE TIME

-MAX CYCLE TIME

(The dashboard format I want to create is shown in the attached image.)

From what I found in the FlexSim forum, it seems that this might be implemented using Global Tables or Statistics Collectors, but I am not sure how to start configuring it.

Could you please suggest the recommended approach or configuration method to collect this data and build the dashboard?

Thank you for your help.

[FelixMoehlmann]

I think the simplest option would be to use a Tracked Variable.

- Add a label to the queue that will track the previous entry time. Make sure it gets reset to 0 on model reset.

- Add a Tracked Variable to the toolbox (Time Series).

- In the entry trigger of the queue, set the Tracked Variable to the last interval value (current model time - time stored in label) and then update the label with the current time. In the attached model I don't log an interval for the first item by adding a condition that the previous entry time must be larger than 0.

- Add a Tracked Variable table chart to the dashboard and link the Tracked Variable to it.

[ayeong_jo]

Thank you very much for your quick response and for explaining the method using Tracked Variables. It was very helpful.

I also wanted to ask if it would be possible to implement the same logic using a Statistics Collector.

Specifically, I am wondering if it is possible to record the box arrival times at the OutPort using a Statistics Collector, and then use that data to calculate the time interval between consecutive box arrivals and display it on a dashboard.

Learning how to implement this using a Statistics Collector would be very helpful for applying similar logic to other cases in the future.

Thank you again for your help and support.

[FelixMoehlmann]

You could use the same approach. The last entry time is stored on a label on the object (though now as part of the "On Row Added" trigger of the Statistics Collector, to guarantee that the timing is correct) and the collector just calculates the difference between that value and the current model time. This is, in my opinion, the better approach, since it allows to combine the statistics of multiple obejcts into a single collector, since each object tracks its own last entry time.

For just one object, you can of course also just read the entry time from the previous row and do the calculation with that.

In both cases you would then use a Calculated Table to generate the aggregate data shown in the dashboard table.

[ayeong_jo]

Thank you for suggesting a different method.

I applied the same logic, but I am still getting an error during the simulation.
It seems the problem is related to the label in the Outport, but I cannot find the exact cause.

The error message is:
time: 27.585523 exception: FlexScript exception: MODEL:/Outport>variables/entrytrigger at line 14

[FelixMoehlmann · Accepted solution]

The entry trigger is still configured to set the Tracked Variable value which does not exist in your model. The entry trigger serves no purpose since the label value is now updated in the collector's trigger. It can be removed.

You also need to set the Calculated to update whenever values are read from it (like when a dashboard chart is drawing data from it).

[ayeong_jo]

In Question2, the calculated interval includes the first arrival time.
Because of this, the average interval value is higher than expected at the beginning.

What I want is:

The first result value should be
→ (second arrival time - first arrival time)

To solve this, I modified the condition in
Statistics Collector → Triggers.

The first arrival time is still included in the result

 

How can I exclude the first arrival from the calculation?

[FelixMoehlmann · Accepted solution]

For the collector that uses the label on the object you can use the Condition field on the Events tab to not generate a row for the first event.

With how the other collector is currently working it needs that row to calculate the next interval. You could at most return some placeholder value for the interval and later exclude it from the query in the Calculated Table (partition).

[ayeong_jo]

Thank you so much. All my questions about the Statistics Collector have been fully resolved.
I really appreciate your help!