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A process for sound conformance testing of cyber-physical systems

The term Hybrid System is used to describe a modelling formalism of systems that combine discrete and continuous aspects; for instance, a system where a controller (discrete component) is connected to a physical system (continuous component). Systems that encompass tightly integrated digital and phy...

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Main Author: ARAUJO, Hugo Leonardo da Silva
Other Authors: SAMPAIO, Augusto Cezar Alves
Format: masterThesis
Language: eng
Published: Universidade Federal de Pernambuco 2019
Subjects:
Engenharia de software
Métodos formais
Online Access: https://repositorio.ufpe.br/handle/123456789/29687
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spelling ir-123456789-296872019-10-26T02:21:38Z A process for sound conformance testing of cyber-physical systems ARAUJO, Hugo Leonardo da Silva SAMPAIO, Augusto Cezar Alves CARVALHO, Gustavo Henrique Porto de http://lattes.cnpq.br/4993643802908151 http://lattes.cnpq.br/3977760354511853 Engenharia de software Métodos formais The term Hybrid System is used to describe a modelling formalism of systems that combine discrete and continuous aspects; for instance, a system where a controller (discrete component) is connected to a physical system (continuous component). Systems that encompass tightly integrated digital and physical components and deal with spatial and temporal metrics, besides involving human interaction, are known as Cyber-Physical Systems (CPS). Model-based testing of CPSs is a recent subject in the literature, and it is still being actively researched and developed. The analysis of CPSs is usually complex due to their multidisciplinary nature, with such systems dealing with aspects of different subject areas such as computer science, physics and control systems. In this work, we propose a process for sound conformance testing of cyberphysical systems. The main goal of this process is to provide a practical and semi-automatic solution to testing CPSs. Some of the steps of our process were mechanized through the use of a prototype tool that we have developed. This project was conceived during the literature review in our research when we realized the absence of a structured process with systematic steps for conformance testing of CPSs. We first focused on studying the existing conformance testing strategies of hybrid systems and settled on working with (τ, ε)-conformance relation. In this conformance notion, the outputs of both specification and implementation models are compared under the same input stimuli. It makes use of temporal (τ) and spatial (ε) margins of error to determine if the output behaviours are close enough to each other. In conformance verification strategies based on this relation, an issue related to soundness was brought to our attention, which made us shift our focus to solve this problem through reachability analysis. We noticed that the sampling rate, used to observe the system behaviour at discrete points, was closely related to the soundness problem identified. This motivated the definition and partial automation of a process to support conformance testing of CPSs. The proposed process involves five steps: (i) automatic sampling rate computation; (ii) margins of error definition (temporal and spatial); (iii) performing reachability analysis to obtain sound verdicts; (iv) conformance testing (test generation, test execution and verdict attainment); (v) result analysis and parameters tuning. Additionally, we have performed an empirical analysis to shown how our approach can be used in practice describing a few usage scenarios as well as implementing two case studies: a combustion engine controller and a pneumatic suspension system. CAPES O termo Sistema Híbrido é usado para descrever sistemas que combinam elementos contínuos e discretos; por exemplo, um sistema em que um controlador digital (elemento discreto) está conectado à um sistema físico (elemento contínuo). Sistemas desse tipo, que envolvem componentes físicos e digitais altamente integrados e que lidam com métricas temporais e espaciais, além de envolverem interação humana, são conhecidos como sistemas ciber-físicos (SCF). Neste contexto, o uso de técnicas de teste baseadas em modelos (do inglês, Model Based Testing) em sistemas ciber-físicos é um assunto recente e está sendo ativamente pesquisado e desenvolvido. A análise de SCFs é de alta complexidade devido à multidisciplinaridade de tais sistemas, que combinam aspectos de diversas áreas como ciência da computação, física e sistemas de controle. Neste trabalho, nós propomos um processo para teste de conformidade de sistemas ciber-físicos. O objetivo desse processo é oferecer uma abordagem prática que provê uma solução semi-automática para o teste de SCFs. Algumas etapas do processo foram mecanizadas a partir de um protótipo de ferramenta desenvolvido. Este projeto foi concebido durante a revisão da literatura, quando percebeu-se a falta de um processo estruturado com passos sistematizados para a realização de testes de conformidade em SCFs. Em primeiro plano, a pesquisa foi direcionada para o estudo das relações de conformidade existentes, o que resultou em um foco maior na relação (τ, ε)-conformance. Nesta relação de conformidade, as saídas dos modelos da especificação e da implementação são comparadas sob o mesmo estímulo de entrada. Ela faz uso de margens de erro temporais (τ) e espaciais (ε) para determinar se o comportamento de saída dos modelos estão suficientemente próximas. Em estratégias de verificação de conformidade com base nesta relação, um problema relacionado à propriedade de inconsistência (soundness) da relação foi percebido, o que fez com que o foco da pesquisa fosse voltado a resolver esse problema via análise de alcançabilidade. Identificou-se que a taxa de amostragem, utilizada para observar o comportamento do sistema em pontos discretos, estava fortemente relacionada ao problema de inconsistência encontrado. Isto motivou a definição e automação parcial de um processo para apoiar o teste de conformidade de SCFs. O processo é organizado em cinco passos: (i) computação automática da taxa de amostragem; (ii) definição das margens de erro temporais e espaciais (τ e ε, respectivamente); (iii) execução da análise de alcançabilidade com o objetivo de assegurar a consistência da análise; (iv) teste de conformidade (geração e execução dos testes e obtenção do veredito); (v) análise dos resultados e ajuste de parâmetros. Além disso, foi realizada uma análise empírica para mostrar como essa abordagem pode ser usada na prática. Descrevemos alguns cenários de uso e dois estudos de caso: um controlador de um motor de combustão e um sistema de suspensão pneumática. 2019-03-13T21:15:15Z 2019-03-13T21:15:15Z 2017-08-17 masterThesis https://repositorio.ufpe.br/handle/123456789/29687 eng openAccess Attribution-NonCommercial-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nc-nd/3.0/br/ application/pdf Universidade Federal de Pernambuco UFPE Brasil Programa de Pos Graduacao em Ciencia da Computacao
institution REPOSITORIO UFPE
collection REPOSITORIO UFPE
language eng
topic Engenharia de software
Métodos formais
spellingShingle Engenharia de software
Métodos formais
ARAUJO, Hugo Leonardo da Silva
A process for sound conformance testing of cyber-physical systems
description The term Hybrid System is used to describe a modelling formalism of systems that combine discrete and continuous aspects; for instance, a system where a controller (discrete component) is connected to a physical system (continuous component). Systems that encompass tightly integrated digital and physical components and deal with spatial and temporal metrics, besides involving human interaction, are known as Cyber-Physical Systems (CPS). Model-based testing of CPSs is a recent subject in the literature, and it is still being actively researched and developed. The analysis of CPSs is usually complex due to their multidisciplinary nature, with such systems dealing with aspects of different subject areas such as computer science, physics and control systems. In this work, we propose a process for sound conformance testing of cyberphysical systems. The main goal of this process is to provide a practical and semi-automatic solution to testing CPSs. Some of the steps of our process were mechanized through the use of a prototype tool that we have developed. This project was conceived during the literature review in our research when we realized the absence of a structured process with systematic steps for conformance testing of CPSs. We first focused on studying the existing conformance testing strategies of hybrid systems and settled on working with (τ, ε)-conformance relation. In this conformance notion, the outputs of both specification and implementation models are compared under the same input stimuli. It makes use of temporal (τ) and spatial (ε) margins of error to determine if the output behaviours are close enough to each other. In conformance verification strategies based on this relation, an issue related to soundness was brought to our attention, which made us shift our focus to solve this problem through reachability analysis. We noticed that the sampling rate, used to observe the system behaviour at discrete points, was closely related to the soundness problem identified. This motivated the definition and partial automation of a process to support conformance testing of CPSs. The proposed process involves five steps: (i) automatic sampling rate computation; (ii) margins of error definition (temporal and spatial); (iii) performing reachability analysis to obtain sound verdicts; (iv) conformance testing (test generation, test execution and verdict attainment); (v) result analysis and parameters tuning. Additionally, we have performed an empirical analysis to shown how our approach can be used in practice describing a few usage scenarios as well as implementing two case studies: a combustion engine controller and a pneumatic suspension system.
author2 SAMPAIO, Augusto Cezar Alves
format masterThesis
author ARAUJO, Hugo Leonardo da Silva
author_sort ARAUJO, Hugo Leonardo da Silva
title A process for sound conformance testing of cyber-physical systems
title_short A process for sound conformance testing of cyber-physical systems
title_full A process for sound conformance testing of cyber-physical systems
title_fullStr A process for sound conformance testing of cyber-physical systems
title_full_unstemmed A process for sound conformance testing of cyber-physical systems
title_sort process for sound conformance testing of cyber-physical systems
publisher Universidade Federal de Pernambuco
publishDate 2019
url https://repositorio.ufpe.br/handle/123456789/29687
_version_ 1648654602670702592
score 13.657419

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