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Using a VAE-SOM architecture for anomaly detection of flexible sensors in limb prosthesis
School of Information Science and Engineering, Fudan University, Shanghai, China.ORCID iD: 0000-0002-2046-3008
KTH, School of Industrial Engineering and Management (ITM), Engineering Design.ORCID iD: 0000-0002-8028-3607
Department of Computer and Information Science, Linköping University, Linköping, Sweden.
School of Information Science and Engineering, Fudan University, Shanghai, China.
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2023 (English)In: Journal of Industrial Information Integration, ISSN 2452-414X, Vol. 35, article id 100490Article in journal (Refereed) Published
Abstract [en]

Flexible wearable sensor electronics, combined with advanced software functions, pave the way toward increasingly intelligent healthcare devices. One important application area is limb prosthesis, where printed flexible sensor solutions enable efficient monitoring and assessing of the actual intra-socket dynamic operation conditions in clinical and other more natural environments. However, the data collected by such sensors suffer from variations and errors, leading to difficulty in perceiving the actual operational conditions. This paper proposes a novel method for detecting anomalies in the data that are collected for measuring the intra-socket dynamic operation conditions by printed flexible wearable sensors. A discrete generative model based on Variational AutoEncoder (VAE) is used first to encode the collected multi-variant time-series data in terms of latent states. After that, a clustering method based on the Self-Organizing Map (SOM) is used to acquire discrete and interpretable representations of the VAE encoded latent states. An adaptive Markov chain is utilized to detect anomalies by quantifying state transitions and revealing temporal dependencies. The contributions of the proposed architecture conclude as follows: (1) Using the VAE-SOM hybrid model to regularize the continues data as discrete states, supporting interpreting the operational data to analytic models. (2) Employing adaptive Markov chains to generalize the transitions of these states, allowing to model the complex operational conditions. Compared with benchmark methods, our architecture is validated via two public datasets and achieves the best F1 scores. Moreover, we measure the run-time performance of this lightweight architecture. The results indicate that the proposed method performs low computational complexity, facilitating the applications on real-life productions.

Place, publisher, year, edition, pages
Elsevier BV , 2023. Vol. 35, article id 100490
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-333982DOI: 10.1016/j.jii.2023.100490ISI: 001045906000001Scopus ID: 2-s2.0-85165005873OAI: oai:DiVA.org:kth-333982DiVA, id: diva2:1788125
Funder
EU, Horizon Europe, 825429
Note

QC 20230816

Available from: 2023-08-15 Created: 2023-08-15 Last updated: 2025-03-20Bibliographically approved
In thesis
1. Supporting Self-Management in Cyber-Physical Systems by Combining Data-driven and Knowledge-enabled Methods
Open this publication in new window or tab >>Supporting Self-Management in Cyber-Physical Systems by Combining Data-driven and Knowledge-enabled Methods
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cyber-Physical Systems (CPS) refer to intelligent systems that combine computational and physical capabilities to enable advanced functionalities, such as autonomous behaviors, human-machine interaction, and machine collaboration in complex environments. Addressing these functionalities often necessitates the adoption of Artificial Intelligence (AI) techniques which are extensively utilized for operational perception and decision-making. However, due to the inherently data-intensive and opaque nature of most AI-enabled components, combined with unforeseen environments, the integration of AI-enabled techniques into CPS presents significant engineering challenges in quality management. Self-management, as an embedded system feature, extends conventional CPS with capabilities for operation monitoring, planning and adaptation. It is often considered as a necessary mechanism for ensuring the quality and trustworthiness of AI-enabled components. However, implementing self-management in AI-enabled CPS presents several challenges: The concept of self-management varies depending on the audience and application, making its definition and implementation more complex. Additionally, the data-intensive nature of AI-enabled components requires extra effort to ensure consistent performance across operational domains, especially under unforeseen conditions. To cope with these challenges, this thesis proposes to integrate data-driven and knowledge-enabled methods for self-management through the following efforts: 1) Proposing conceptual frameworks that define the necessary and sufficient functionalities for self-management, with the support for situation awareness regarding the internal and environmental conditions; 2) Developing condition monitoring modules within the proposed conceptual frameworks for the situation-awareness to analyze system status; 3) Creating human-explainable data-driven methods for understanding operational conditions; 4) Designinglearning-based agents to dynamically and effectively address vulnerabilities inAI-enabled systems that could lead to system failures or compromise the operational safety. This thesis consolidates key concepts and introduces novel features for self-management in CPS by synthesizing insights from existing research and addressing their limitations. It provides a framework for designing learning based agents that leverage data synthesis to achieve self-management. Additionally, the thesis develops data-driven methods integrated with knowledge enabled models to enhance situation awareness and trustworthiness, effectively addressing the complexity and opacity of AI-enabled computing processes.

Abstract [sv]

Cyberfysiska system (CPS) är intelligenta system som kombinerar beräknings-mässiga och fysiska förmågor för att möjliggöra avancerade funktioner, som autonoma beteenden, interaktion mellan människa och maskin och maskinsamarbete i komplexa miljöer. För att hantera dessa funktionaliteter används ofta artificiell intelligens (AI), särskilt inom operativ perception och beslutsfattande. Men på grund av att de flesta AI-komponenter är dataintensiva och svårgenomtränglig, i kombination medoförut-sedda miljöer, innebär integrationen av AI-komponenter i CPS betydande tekniska utmaningar när det gäller kvalitetshantering.

Självförvaltning, som en inbyggd systemfunktion, utökar konventionella CPS med funktionaliteter för driftsövervakning, planering och anpassning. Den anses ofta vara en nödvändig mekanism för att säkerställa kvaliteten och pålitligheten hos AI-komponenter.

Att implementera självförvalt-ning i AI-aktiverade CPS innebär dock flera utmaningar: Begreppet tolkas olika beroende på målgrupp och tillämpning, vilket gör definitionen och implementeringen mer komplex. Dessutom kräver AI-komponenter ofta extra ansträngningar för att säkerställa konsekvent prestanda över olika operativa domäner, särskilt under oförutsedda förhållanden.

 

För att adressera dessa utmaningar föreslår denna avhandling en integrering av datadrivna och kunskapsbaserade metoder för självförvaltning genom följande insatser: 1) Utveckling av konceptuella ramverk som definierar de nödvändiga och tillräckliga funktionerna för autonom hantering, med stöd för situationsmedvetenhet om både interna och externa förhållandena; 2) Implementering av tillståndsövervakningsmoduler inom de föreslagna konceptuella ramverken för att analysera systemstatus och förbättra situationsmedvetenheten; 3) Skapande av förklarbara datadrivna metoder som möjliggör en bättre förståelse av operativa förhållanden; 4) Design av inlärningsbaserade agenter för att dynamiskt och effektivt hantera sårbarheter i AI-baserade system, förebygga systemfel och säkerställa driftsäkerhet.

Denna avhandling samlar nyckelbegrepp och introducerar nya funktioner för autonom hantering i cyberfysiska system genom att sammanställa insikter från befintliga studier och adressera deras begränsningar. Den presenterar ett ramverk för att utforma inlärningsbaserade agenter som utnyttjar datasyntes för att uppnå autonom hantering. Vidare utvecklas datadrivna metoder som kombineras med kunskapsbaserade modeller för att förbättra situationsmedvetenhet och pålitlighet, samtidigt som de komplexa och svårgenomträngliga databehandlingsprocesserna i AI-drivna komponenter hanteras.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2025. p. 83
Series
TRITA-ITM-AVL ; 2025:9
Keywords
Cyber-Physical Systems, Artificial Intelligence, Deep Learning
National Category
Engineering and Technology
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-361423 (URN)978-91-8106-234-2 (ISBN)
Public defence
2025-04-10, M1 / https://kth-se.zoom.us/j/62678100345, Brinellvägen 64 A, Stockholm, 09:00 (English)
Opponent
Supervisors
Available from: 2025-03-20 Created: 2025-03-19 Last updated: 2025-04-08Bibliographically approved

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Su, PengOttikkutti, SuranjanTahmasebi, Kaveh NazemZou, ZhuoZheng, Li-rongChen, DeJiu

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