Demystifying the three magic lifts of IFI

Anyone who has frequented the tower of IFI has faced the challenge of the three lifts: Two are collaborating with one button to push, the third is apart with its own button, and this lift seems slower. Which button to push to minimize the waiting time to get served? The demand from others in the building depends on the random number of people present in the tower and when they will come and go and when they take their lunch, hence the time of day. At the same time, the wait also depends on where the various lifts are relative to you, and it is an opaque algorithm deciding which one of the two collaborating lifts that will be dispatched to you first. The slower lift will surely get to you as soon as it can, but is that faster than one of the other two? And how much will it delay all others waiting if you decide to push both buttons risking that the last arriving lift to your floor will be left empty? Is it possible to develop a game theoretic strategy for which button to push when you want the lift so that everyone gets a fair and shortest possible waiting time?

Research questions

  1. How can the three magic lifts best be modelled?
  2. What data is necessary to identify the unknown parameters of the system model?
  3. How can the system model be validated?
  4. What are the system model’s uncertainties, and how can they be quantified or bounded?
  5. How can the identified model be used in optimization, and is there a strategy that will ensure fairness among players?

Methodology

This thesis will take you on a journey from the ground floor of data acquisition about the lifts’ positions and demands. Then you will be lifted through the concepts of stochastic processes to model the arrivals, Markov Decision Processes and Finite State Machines for identifying and modelling the two collaborative lifts, arriving at queuing theory to compute the waiting times. Finally, the door is open for stochastic optimization to answer the key questions.

These classical approaches should be compared with taking the staircase of reinforcement learning and stepwise improve a deep learning model of the lifts' behaviours in response to the stochastic user demands. An issue with a deep learning model is the lack of quantified confidence in its results, and it can be difficult to assess the uncertainties. It could therefore be better to develop a multi-agent model of the lifts and the behaviour of the people at IFI, and then use ensemble simulations to address the uncertainty in your optimized solutions.

What you will learn

For the first part of the journey you will need some prior knowledge about data collecting devices, like a camera, how to program these, and possibly image classification by machine learning algorithms. You will learn:

For the last parts of the journey you will learn advanced scientific methods for

No prior knowledge is necessary in these areas, but you must appreciate some advanced mathematics. This journey is not for the faint-hearted!

Published Aug. 21, 2026 3:43 PM - Last modified Aug. 21, 2026 3:43 PM

Supervisor(s)

Scope (credits)

60