When does a control system compute? Digital, mechanical and open-loop systems

2026-04-17

AI Summary

This study investigates whether control systems—including non-digital and purely mechanical ones—inherently possess computational properties. By systematically introducing the Abstract/Representational Theory (ART) into control theory for the first time, the authors model the controlled plant as a representational entity and analyze canonical cases such as digital thermostats, electromechanical thermostats, centrifugal governors, and open-loop artificial systems. The analysis reveals that all examined control systems perform computation to varying degrees, thereby challenging the long-standing view in cognitive science that treats the centrifugal governor as a paradigmatic non-computational counterexample. These findings offer novel theoretical support for computationalism in cognitive science, suggesting that computation may be a more pervasive feature of control mechanisms than previously assumed.

Technology Category

• Cognitive Modeling & Cognitive Systems: Computational Creativity
• Knowledge Representation and Reasoning: Computational Complexity of Reasoning
• Intelligent Robots: Behavior Learning & Control

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: Research challenges in human and human-AI computation
• Social Networks and Social Media: Computational social science

Abstract

Control systems are ubiquitous in modern technology, comprising an engineered plant to be kept within specific, often fine-tuned, limits, and a separate controller that ensures this is the case. While modern controllers often employ digital computers, other examples are purely mechanical, or even biological. It is an open question whether computation is happening within all controllers by virtue of them being part of a control system. Abstraction/ Representation theory (ART) has been developed to tackle just this question of whether a physical system is computing. Here, we demonstrate how to use ART to model control systems, and analyse them for computational properties. We determine that the plant of a control system is (a proxy for) the representational entity necessary in ART for the existence of any computation: the plant is the user of the controller. We consider specific systems: a digital thermostat, an electro-mechanical thermostat, the purely mechanical centrifugal governor, and an open-loop human-controlled heating system. We show that all these systems, and control systems in general, are performing some degree of computation. As an initial use of these results, we apply them to computationalism within cognitive theory: we show the governor is computing, so it cannot play its role of counter-example in the question of whether the brain is too.

Problem

• control systems
• computation
• Abstraction/Representation theory
• computationalism
• physical computing

Innovation

• Abstraction/Representation Theory
• control systems
• computation
• centrifugal governor
• computationalism