Simulating queues in front of ski lifts

[Nico]

Dear all,

I am currently working on my master's thesis. The goal is to simulate the waiting line in front of a chair lift at a ski resort. I may have future questions, so I hope we can keep this topic open for other questions on the same model.

I started adding objects and need to set the properties for the servers now. Currently I am struggling to find the correct setting that allows me to process entities at a fixed time interval. I want the red barriers in front of the moving walkway to open every 7.2 seconds (interval between two chairs). The servers are called "Schranke" in my screenshot. Moreover, every barrier should open at the same time, i.e. all six servers are supposed to process one entity at the same point of time regardless of its arrival. 

Thanks for your help!

Nico

[dsturrock]

A couple quick thoughts:

• Both from your description and from what I know about chair lifts, it seem that using a conveyor might be the best modeling approach.
• You might consider using a combiner instead of a server to synchronize all waiting skiers together into a lift car. 

[Nico]

Dear Dave,

thanks for your reply. Yes, I used a conveyor for the moving walkway but I am not interested in the lift itself. It's only about the queue in front of it. Until now I wasn't able to find a proper solution for the problem described above...

 

[Tom van Es]

Hi Nico,

I haven't tried this out, so I can't guarantee this to work, but you could specify a Timer that goes off every 7.2 seconds. Additionally, you'd create a process that runs on the triggering event with the name of that Timer. This process Assigns a new value of 1 to Schranke1...Schranke6.CurrentCapacity. I'm unsure whether a delay is required for the entities to move through the system, but I'd try adding a Delay of Math.Epsilon after this Assign step, to ensure they do. Then, with a new Assign step, change the CurrentCapacity of Schranke 1 through 6 back to 0. 

You may have to change the Initial capacity of all your gates to 0 in the Facility window. Also, make sure you change the Off Shift Rule to finish work that has already started, on all your gates.

Hope this works.

Tom

[Nico]

Hi Tom,

thanks for your help! I've found a solution on my own in the meantime (probably not as sophisticated as yours but it works well). 

I additionally modelled a small version of the lift itself and created a wait process. The triggering event is "vehicle exits Node X". I used the process for my servers ("after processing"). So whenever a chair exits the node, the gates will open. This is actually quite close to reality where the gate opening interval is not fixed but depends on the speed of the lift and the point in time when an empty chair arrives.

All the best,
Nico

[Tom van Es]

Hi Nico,

Glad to hear you solved it in the meantime. It seems like your solution better represents what happens in reality, glad you sorted it out, and thanks for sharing!

Kind regards,

Tom