Travel time operator: simulation model results not equal to hand calculation

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Frans DG asked Oct 30, '20 hermione12 commented Jul 29, '22

Travel time operator: simulation model results not equal to hand calculation

Dear reader,

The issue: the travel time of my operator in the simulation model is not the same as my hand calculations. The operator has a speed of 1.11 m/s, acceleration of 0.44 m/s, and deceleration of 1 m/s. The model is set to meters and seconds.

I created a situation in which an operator has to travel from node A to node B. The distance traveled is 11.6 meters according to the operator's statistics. I used a Staytime activity in the dashboard to measure the time the operator travels. This was equal to 11.71 seconds.

However, if I calculate the travel time by hand, I get a travel time of 12.27 seconds. I used the following equation:

distance = 0.5*acceleration*(t1)^2 + speed*t2 + 0.5*deceleration*(t3)^2

I assumed a constant acceleration, therefore, t1 = 1.11 / 0.44 and t3 = 1.11 / 1. As for t2, this has been determined by dividing the remaining distance (distance when there was no acceleration) by 1.11 (the speed).

Since I assumed that the acceleration and deceleration are constant, the outcome of my hand calculations should be the shortest time possible, which is 12.27 seconds.

I could understand if the operator in the simulation model would take a little longer, for instance, if the acceleration and/or speed would not be constant. However, as I see it, the travel time in the simulation model can never be shorter than the hand calculation.

Can somebody please explain why this happens?

With kind regards,

Frans

Software Version:

FlexSim 20.1.2

operator flexsim 20.1.2

· 1

Ben Wilson ♦♦ commented · Nov 09, 2020 at 11:50 PM

Hi @Frans DG, was Allister Wilson's answer helpful? If so, please click the red "Accept" button on their answer. Or if you still have questions, add a comment and we'll continue the conversation.

If we haven't heard back from you within 3 business days we'll auto-accept an answer, but you can always unaccept and comment back to reopen your question.

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Answer 1 · 2020-10-30T11:00:13Z

Allister Wilson answered Oct 30, '20 hermione12 commented Jul 29, '22

Presumably there's a problem with your test setup or the way you're measuring time, in the attached model an operator with the same acceleration / deceleration / speed as yours takes 12.27s to travel 11.6m as expected.

20201030_operator_travel_time.fsm

20201030-operator-travel-time.fsm (30.4 KiB)

· 6

Frans DG commented · Oct 30, 2020 at 11:36 AM

This is odd. Indeed, in your model, it is working fine. In case I find the problem, I will add it to this post. It most likely has to do with the AutoCad drawing that I added to the model. Perhaps something went wrong with the scaling.

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hermione12 commented · Jul 27, 2022 at 05:43 AM

hey @Allister Wilson can you please share the same model in 20.0.0 version? It would be a great help!!

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Allister Wilson hermione12 commented · Jul 27, 2022 at 06:53 AM

Is there a reason you can't install a more recent version of FlexSim?
Nothing in that model requires a license to access, if that's what you were worried about.

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hermione12 Allister Wilson commented · Jul 27, 2022 at 07:13 AM

I am using Flexsim 20.0 version. I am not able to open the model. So I asked for the 20.0 version for your model so as to refer.

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