An Artificial Hormone-based Algorithm for Production Scheduling

Artificial hormone systems are inspired by the natural endocrine system that adjusts the metabolism of tissue cells in our body. By connecting decisions and actions in a system to the production and evaporation of artificial hormones, it is possible to create a bio-inspired self-organizing algorithm.

Application areas for such algorithms are problems with many agents to be coordinated, where existing optimization approaches come to their limit. An example of such a problem is the production of logic and power integrated circuits (ICs) in the semiconductor industry. Unlike the high-volume production of memory ICs, wafer production in the logic and power sector has a large product mix. This involves many processing steps and dynamic changes of involved machines.

Weekly workloads can involve around 100 000 operations on thousands of machines. Optimizing such a system for work in progress and flow factor is an NP-hard problem. At this size, existing dispatching rules and linear optimization methods cannot cope with the NP-hard search space, thus not optimize the entire system.

To address this issue, we have modeled a production plant as a self-organizing system of agents that interact with each other in a non-linear way. As it is common in the semiconductor industry, wafers are combined in groups of 25 pieces forming a so-called lot. In our approach, an artificial hormone systems is used to express a lot's urgency and the need for new lots at a machine type, thus providing a system using local information for optimization. The algorithm builds upon five principles, which are 

• (i) machines produce hormone to attract lots, 
• (ii) hormone diffuses process-upstream, 
• (iii) incoming lots diffuse hormone, 
• (iv) lots are prioritized by their timing, and 
• (v) lots are attracted by hormone. 

Via these mechanisms, machines can balance their workload by pulling required lots towards them. The algorithm has been implemented and evaluated in a NetLogo simulation model. Simulation results indicate that the artificial hormone system improves around 5% for overall production time and flow factor compared to a baseline algorithm. Future work will investigate if the hormone algorithm can be used on top of existing production systems. In a productive system an improvement of 5% would be highly notable.

More information can be found on the SWILT project webpage and in the paper

Wilfried Elmenreich, Alexander Schnabl, and Melanie Schranz. An artificial hormone-based algorithm for productionscheduling from the bottom-up. In Proceedings of the 13th International Conference on Agents and Artificial Intelligence. SciTePress, February 2021.

Click triangle for Bibtex entry

@inproceedings{elmenreich:Hormone:21,
  author = {Elmenreich, Wilfried and Schnabl, 
    Alexander and Schranz, Melanie},
  title = {An artificial hormone-based algorithm
    for production scheduling from the bottom-up},
  booktitle = {Proceedings of the 13th International 
    Conference on Agents and Artificial Intelligence},
  year = {2021},
  month = feb,
  publisher = {SciTePress}
}  
  

The Next Big Thing in Artificial Evolution

As announced in a previous blogpost, Prof. A. E. Eiben gave a very interesting talk on the next big in thing in artificial evolution during his visit at the Alpen-Adria-Universität Klagenfurt. Eiben presented a vision about having animate artefacts that are able to evolve and self-reproduce in physical spaces. To make this happen, he gives a notion of the integration of "hard" vs. "soft" evolutionary computation, the former meaning evolutionary optimiziation and design while the latter refering to artificial life, swarm robotics, and artificial societies.

Gusz Eiben's talk was attracting many people and lead to a vivid discussion afterwards about technology, possibilities, societal implications and parallels to existing sci-fi stories from Philip K. Dick or movies such as Terminator. So I think it is appropriate to say this talk was truly presenting science beyond fiction.

• A.E. Eiben, S. Kernbach, and Evert Haasdijk, Embodied artificial evolution: Artificial evolutionary systems in the 21st Century, Evolutionary Intelligence, 5(4):261-272, 2012
• A.E. Eiben. Introduction on Evolutionary Computing, Book, Springer, Natural Computing Series, 2003, ISBN: 3-540-40184-9
• More information on Eiben's work

Prof. A. E. Eiben at Lakeside Labs: The Next Big Thing in Artificial Evolution

Professor Àgoston E. Eiben will give an interesting talk at the Lakeside Labs / Alpen-Adria-Universität Klagenfurt on April 10th 2014, 15:00 CET, Room L4.1.114  

Abstract:
This talk presents a vision about the upcoming breakthrough in artificial evolution: animate artefacts that (self-)reproduce in physical spaces. In other words, we witness the “Evolution of Things”, rather than just the evolution of digital objects, leading to a new field of Embodied Artificial Evolution. After presenting this vision some of the technical challenges are elaborated and related to the main algorithmic/technical requirements to the current know-how in evolutionary computing. Finally, Prof. Eiben will speculate about possible applications, their societal impacts, and argue that these developments will radically change our lives.

For those who cannot attend or want to warm up on the topic, we recommend Eiben's TED talk "Evolution at Work":

Bio:
A.E. Eiben is a professor of Computational Intelligence on the VU University Amsterdam and Visiting Professor in the Department of Electronics of the University of York, UK. He is one of the European early birds of Evolutionary Computing; his first EC paper dates back to 1989 and he co-authored the first comprehensive book on the subject. He has been organizing committee member of practically all major international evolutionary computing conferences and editorial board member of related international journals. He have also coordinated or participated in several EU research projects. Prominent themes in his work include multi-parent recombination methods, evolutionary constraint handling, evolutionary art, artificial life, and evolutionary robotics. Furthermore, he is concerned with methodological issues, especially the design and calibration of evolutionary algorithms (parameter tuning off-line as well as parameter control on-line). Lately he became interested in artificial evolutionary systems that are physically embodied in real time and real space. This goes far beyond conventional evolutionary computing in digital spaces and implies great new opportunities and challenges – see his TEDx talk and a journal paper on the vision, and the The Triangle of Life framework for a possible implementation in robotic systems that can self-reproduce. On the long term, a broad range of possible “incarnations” can emerge and form a radically new way of engineering. Furthermore, they can serve as an apparatus to investigate deep scientific questions about evolution in a new substrate, different from carbon-based life as we know it.

Solving the „Tracking Game“

Guest article from Doris A. Behrens


Games taking place in a shared environment are characterized by the fact that the effectiveness of individual decisions heavily depends on the decisions of other players. Our algorithm OPTGAME is able to approximate the evolution of choices to be made if a number of independent decision makers seek to reach individually desirable states. The evolution of states subject to control is described by a system of nonlinear difference equations. We call this a „tracking game“, since is an extension of the linear regulator problem (also known as „tracking problem“) that is well known from LQ optimal control theory.
OPTGAME is a tool that steers the control and state paths towards desired outcomes. It is novel in a way that it works for game theoretic systems with nonlinear constraints. It searches for equilibrium solutions by iteratively applying a sequence of local linearization and optimization over the entire planning horizon. The tool yields three types of non-cooperative equilibrium solutions (open-loop Nash equilibrium, feedback Nash equilibrium, feedback Stackelberg equilibrium) plus one cooperative solution (Pareto-optimal strategy).
An example for such a game could be the decision-making within a monetary union such as the European Monetary Union (EMU). In this game all but one player represent countries with intentions for economic growth, employment and limited budget deficit and one player represents the European Central Bank, aiming solely at price stability. Besides trade-offs between state variables, for example the well-known trade-off between unemployment and price stability (see Phillips curve), there are strong economic interdependencies due to international trade.

European Monetary Union

For instance, if a single country aims at economic growth, one option could be to increase the demand for goods and services from the public sector. This increases production in response to demand, which in turn increases incomes. However, within an open economy the future success strongly depends on the situation and behavior of the other member countries. In order to find a solution for this problem it is necessary to estimate the countries’ individual parameters as well as the degree of economic interdependencies (like trade) between countries.
Such models, in order to be accurate are inherently nonlinear, which cannot be solved analytically by a linear model such as the LQ game. In our work we apply OPTGAME to a monetary union macroeconomic model based on the nonlinear MUMOD1 model. In this model, there are basically two groups of countries, one economically stronger than the other, all experiencing a brief period of recession.

Doris A. Behrens is a senior re-
searcher working on optimization
in techno-socio-economic systems
at the Alpen-Adria-Universität
Klagenfurt

Without policy intervention all countries would experience a deep recession and an enormous increase in public debt. By applying OPTGAME for different solution concepts we learn that macroeconomic properties like public debt, economic growth, inflation, etc. can be significantly improved with system-aware control actions of players.

The OPTGAME tool is available as MATLAB implementation upon request (Contact Doris A. Behrens).

Literature:

Doris A. Behrens, Reinhard Neck, Approximating Solutions for Nonlinear Dynamic Tracking Games, Computational Economics, Springer, February 2014. DOI: 10.1007/s10614-014-9420-4

Reinhard Neck, Doris A. Behrens, A macroeconomic policy game for a monetary union with adaptive expectations. Atlantic Economic Journal, 37(4), 335–349, 2009. DOI: 10.1007/s11293-009-9186-6f