Artificial Intelligence, Machine Learning, IoT, Robotics, and Digital Twins: A Comprehensive Review of Intelligent Technologies
Keywords:
Artificial Intelligence, Machine Learning, Internet of Things, Robotics, Digital Twin, Intelligent Systems, Embodied AI, Edge Intelligence.Abstract
Artificial intelligence (AI), machine learning (ML), the Internet of Things (IoT), robotics,
and digital twin technology together constitute the core technological pillars of the current
intelligent systems era, each with a distinct history, methodological foundation, and body
of research, yet increasingly studied and deployed in relation to one another. This paper
presents a comprehensive review of these five intelligent technologies, examining each
discipline in turn before surveying the intersections and synergies between them. For each
technology, the review summarizes its conceptual foundations, principal methods and
sub-domains, and current market trajectory, drawing on recent industry data: the global AI
market, valued at an estimated $757.58 billion in 2025, dwarfs the digital twin market ($21.14
billion in 2025) and the artificial intelligence robotics market ($6.11 billion in 2025) by more
than an order of magnitude, even as the underlying physical substrate of these systems,
the population of internet-connected IoT devices, is projected to grow from approximately
18.8 billion in 2024 to 40 billion by 2030. The review then examines cross-cutting themes,
including AI-augmented IoT (AIoT), digital twin-enabled robotics, and edge intelligence,
and surveys representative application domains spanning manufacturing, healthcare,
transportation, and smart infrastructure. Critical open challenges are discussed, including
data interoperability across technologies, computational and energy constraints, security
and privacy risks in interconnected systems, and the widening gap between AI software
capability and physical robotics hardware maturity. The paper concludes by identifying
emerging directions, including embodied AI, generative AI-augmented digital twins, and
standardized cross-technology interoperability frameworks. This review is intended to
serve as a consolidated, evidence-based reference for researchers and practitioners across
these five intelligent technology domains.
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