Markov chains (or discrete-time Markov chains, DTMC) based fault tolerance approaches

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Background on AAL

Ambient Assisted Living is a hot topic in Europe. Several projects have been conduct in order to address different aspects and to try covering the inherent needs to a home-keeping situation. Several projects and researches have been conducted in the domain of AAL systems for elderly persons and people with diseases (specifically in the industrial and developed countries). In recent years, the EU has funded a number of projects promoting independent living for elderly. As examples of these projects, the project funded by the ICT Policy Support Program under the Competitiveness and Innovation framework Program (CIP) [ICT PSP], and the Seventh (FP7-2007-2013) Framework Programs for Research and Technological Development [Cordis, 2016].
The AAL Joint Program [AALJP, 2016] is exactly focused on this topic. Several AAL projects address smart homes for the elderly. The solutions proposed by the AAL projects are based on created technologies. They are developed in a close loop with the users, and the projects are expected to result in commercialization in the near future. However, the proposed solutions tend to be specific for a certain class of illnesses and the scientific novelty can be limited. In many of them, services provided are mostly based on a one-to-one correspondence between sensor data and actions that the system performs.
The projects funded by this program are categorized, according to the afforded solutions, into six key groups [AALJP, 2016]:
– ICT based solutions for the prevention and management of chronic conditions for elderly people.
– ICT based solutions for advancement of social interaction of elderly people.
– ICT based solution to provide enhancement in the independency of elderly people.
– ICT based solution to provide mobility solutions to elderly people.
– ICT based solution to provide services that facilitate the self-management of daily life activities.
– ICT based solution to support occupation in life for elderly people.

Projects in AAL

The AAL Joint Program is a collaborative association of twenty European Union member states, in addition to three Associated States. They group together the AAL Association, whose main objective is to enhance the quality of life of elderly people through the use of Information and Communication Technology (ICT). Their main activity is to found R&D projects in the AAL domain and to publish annual calls for project proposals.
GiraffPlus Project:
GiraffPlus (January 2012- December 2014) is an EU project that was funded by the CIP and the FP7 [Coradeschi et al, 2013] in the area of ICT for ageing well. This project deals with enhancing the well-being of elderly people and extends their independency of living, by the early detection of possible health problems to decline them and providing services to assist those having deficiencies [Cesta et al, 2013]. The main components of GiraffPlus system consist of a network of sensors that are ubiquitously integrated in the home and categorized into physiological and environmental sensing devices. The collected data from these sensors is interpreted by an intelligent system which, in turn, prompts alarms or reminders for two kinds of users: the elderly users at home (primary users) and related caregivers and health professional (secondary users). The system consists also of telepresence robot, the Giraff robot, which is controlled over the internet by a remote user to move inside the home, in order to assist the elderly users to sustain their social contacts with other users. Giraff robot has an interface (similar to Skype) and is equipped with communication facilities [Cesta et al, 2013], as illustrated in figure 1.2.
The project newness, compared to other AAL systems, can be summarized in the following:
– Easy communication tool through the robot;
– The system uses a high level reasoning approach for context recognition, configuration planning and personalization and interaction services;
– The development of a system that contains both sensor network and a telepresence robot. Apart from other AAL projects, GiraffPlus has been evaluated in real homes, where it has been installed in at least 15 homes in three EU countries (Italy, Spain and Sweden).
The system developers have followed an evaluation strategy of several steps in order to develop a solution based on the acceptance of the users (by including both primary and secondary users in the experimentation of the system). An initial integrated version of the system has been implemented in order to develop a first version of the solution (including the robot, as well as the different used sensors) with the participation of the primary and secondary users.
Also, a first visualization module has been achieved to envisage different activities in the system. This visualization has been evaluated with secondary users (since the evaluation with primary users is still under development [Coradeschi et al, 2013]). The system, in general, is still under development according to the plan of the project work.

Projects conducted in Lab-STICC

In recent years, the themes of aging and assistance to individuals with disabilities are particularly among the topics to which Brittany Region and the General Council of Morbihan bear interest and help funding projects aiming to find solutions. In 2003, they financed the project COHAND and in 2005 the project QUATRA which includes several stakeholders in the field such as the Lab-STICC, the IRISA laboratories and the center of rehabilitation and Functional Rehabilitation of Kerpape (CMRRF) [Lankri, 2009].
The team work MOCS (Méthodes, Outils pour Circuits et Systèmes) of Lab-STICC participated for several years in projects related to home automation to support dependent persons [Allègre, 2012]. The research area « pervasive systems for disability assistance » brings together the work to application purpose, methodological flows for the deployment of home automation systems that must be the least invasive as possible while ensuring an acceptable level of quality of services. This theme is based on a close cooperation of many years with the center of rehabilitation and Functional Rehabilitation of Kerpape that has plenty of home automation infrastructures. Brittany Region and the General Council of Morbihan have shown a special interest in the problem of dependency for several years and have funded projects that aim at bringing novel technological solutions.
COHAND Project:
In the context of Home Automation, COHAND [Belabbas, 2007] focused mainly on two aspects. The first is the linkage range of services / navigation, which is piloted by the system, in order to facilitate the user navigation, through the wheelchair, to the desired service place. The second is the quality of service that ensures that the system can best provide the service even in the presence of hazards (obstacles or service failures).
This project has focused on the environmental control and the mobility of people with disabilities in the studying of the services offered and the navigation of electric wheelchair [Belabbas et al, 2006a, Belabbas et al, 2006b]. When selecting a service, the system pilots the wheelchair and services related to navigation (e.g. open doors, turn on the lights) to finally activate the requested service (e.g. watching television). The system contains reconfiguration rules in case of failure. The used approach, to calculate the appropriate way to access the service, is based on topological models representing the environment. The topological model is a non-deterministic model of all the possible paths from any area to any other one. The system is able to reconfigure (change path and use of equipment with similar capabilities) to provide the requested service anyway. The system has the ability to respond quickly and efficiently to occurring changes. The intelligent wheelchair cooperates with the environment control through wireless communication, and the proposed approach provides several rules controlling the interaction between the wheelchair and the environment. These rules are based on types of transfer.
This project led to an experimental simulation platform. From a practical point of view, it is not deployable in reality, and therefore it was unusable as a whole for dependent people.
QUATRA Project:
Following the COHAND project, this project leads to a real experimental platform tested in CMRRF Kerpape [De Lamotte et al, 2008] in collaboration with the Lab-STICC. It targets people with severe disabilities. The architecture (connecting terminals) has been defined to ensure the delivery of home automation services. The user, equipped with a PDA can get connected 1) to a mobile terminal embedded in his chair to control it and, 2) to the fixed terminals distributed in the environment. Several experiments have been made for testing a set of scenarios that meet the needs of patients in the center.
In order to facilitate the access to everyday services, the users can control their home automation appliances (shutters, doors…) through a single interface as well as multimedia services through a suitable interface, where a set of basic services and scenarios are published. Upon activation of a scenario, the system automatically generates and activates the sequence of commands to meet the request of the user.
The advantage of this approach resides in the fact that the user does not have to make an effort as it is at his disposal to have full control on the equipment of his house with one or two selections via the adapted interface. QUATRA mainly aimed at using consumer electronic components. This project has taken place in a real experimental platform deployed to users in real situations. The QUATRA project outputs have been the subject of experiments in the Kerpape Centre, in rooms for disabled patients equipped with home automation devices.

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Conception of system elements related with reconfiguration concepts

According to the definition of the reconfiguration concept, and based on the objective of developing a framework, allowing services reconfiguration, this section introduces the main system elements definitions to be realized in the high-level abstract representation of system reconfiguration elements. To conduct this objective, we start by an example introducing the main notions that could be presented in a home automation system, and from the example, we can derive the main conceptions of the reconfigurable system elements.
In the example, we consider that a disabled elderly person living in an apartment which consists of a bedroom, a living room, a kitchen and a bathroom. The apartment is equipped with a set of sensors and actuators that are distributed around in the rooms in order to sense both the environment and the resident, in addition to monitor, analyze and make interventions according to the data delivered by the sensors. The proposed architecture here is the same architecture as the one in the system deployed in Kerpape apartment and consists of the following elements:
– Intelligent wheelchair equipped with a PDA (to control and connect with other smart devices in the apartment);
– Lights of two types: ceiling lights and wall lights that can have controls ON / OFF;
– Electric shutters with up / down controls;
– Doors equipped with electric door openers;
– Electrical Bed;
– Rails ceiling to move the bed to the bathroom and vice versa (with the Up / Down controls and forward / backward);
– Automated windows with the Open / Close commands;
– Controlled plugs;
– Calling facility (connected to a call center);
– Multimedia Facilities;
– Work table and removable electrical cooking elements controllable: Up/Down;
– Entry audio-video returning information on the TV screen;
– Contactors to indicate the doors open state;
– Detector in case of non-supply or fire alarm;
– Temperature Sensors;
– Brightness sensors;
– Presence detectors associated with the light sensors.
Several reconfiguration plans scenarios could be proposed for each element of the list above (a reconfiguration plan in the case of failure in the execution of the service related to each sensor/actuator). Suppose that the resident is willing to go to his/her bedroom from the living room at night by using the wheelchair:
– The controller of the bedroom door should open the door to allow for the resident to move inside the room. In case of door opening failure, the system makes an emergency call to a caregiver, or to a relative, to assist the resident;
– When the door is opened, then automatically the ceiling light in the bedroom is switched on (or the wall lights in the room will be switched on as alternatives of the ceiling light);
– When the presence detector detects that there is nobody in the living room, the lights is switched off. If the lights in the bedroom are failed to switch on, thus the living room lights still on until they are switched off by the user;
– When the presence detector perceives that the resident is in the bedroom and that he/she is in the bed (by the bed sensor detector), then, the system switches off the light(s) and closes the bedroom door. In the case of failure in execution of the last commands, the system sends a command to the relative to assist in the termination of the commands.
The use-case diagram of the proposed scenario is illustrated in figure 2.1 where ellipses represent the service and the main components participating in the execution of the particular service as well as the users participating in performing this service. In the use case-diagram, three types of arrow can be illustrated:
– An arrow connecting users to the service and functions;
– The arrow titled {include} (representing that the parent ellipse “move to bedroom” should comprise the child ellipse, e.g. switch on the light;
– The arrow titled {extend} represents that the parent ellipse, or function, comprises but not obligatory the child function (the function switch-on the light may comprise switching on the wall light).

Table of contents :

General introduction
1. Research Context
2. Problem raised in this research
3. Objectives to be achieved in the thesis
4. Organization of thesis manuscript
Context, Requirements and State-of-the-Art Review
1.1. Introduction
1.2. Ambient Assisted Living
1.3. Home Automation
1.4. Requirements categorization
1.5. Expected Contribution of this thesis
1.6. State-of-the-Art Review
1.6.1. Background on AAL
1.6.2. Projects in AAL
1.6.3. Projects conducted in Lab-STICC
1.6.4. Synthesis and Discussion
1.7. Conclusions
Characteristics and needs for fault tolerance and reconfiguration modeling
2.1. The expected direction of work
2.2. Reconfiguration concept and system elements definitions
2.2.1. Fundamental concepts definition
2.2.2. Conception of system elements related with reconfiguration concepts
2.3. Fault tolerance
2.3.1. Major characteristic of fault tolerance for AAL systems
2.3.2. Fault Tolerance methodologies
2.4. Service failure approaches
2.4.1. Bayesian Networks based fault tolerance approach.
2.4.2. Markov chains (or discrete-time Markov chains, DTMC) based fault tolerance approaches
2.4.3. Boolean logic based fault tolerance computation approach:
2.5. System Abstract formalization
2.5.1. Importance concept and system abstraction
2.5.2. Proposed Fault Tolerance approach
2.6. Fault Tree Analysis
2.6.1. FTA concept definition
2.6.2. Fault Tree analysis and system life cycle
2.6.3. Ongoing research activities
2.7. Proposition of a dynamic reconfiguration approach
2.8. Illustrative example
2.9. Conclusion
System design, analysis and behavior workflow
3.1. Introduction
3.2. System workflow
3.3. System design model structure
3.4. System’s analysis modeling process
3.4.1. The system analysis Meta-Model
3.4.2. The system Fault Tree Analysis model
3.4.3. The Design model-to-FTA model transformation rule
3.5. System’s behavior
3.5.1. The system behavior Meta-Model
3.5.2. The system behavior model
3.5.3. The Design model-to-Behavior model transformation rule
3.6. Illustrative example
3.7. Conclusions
Proposition of a Bayesian-based fault analysis approach
4.1. Proposition of a Bayesian-based fault analysis approach
4.2. Proposed approach based on FTA
4.2.1. Importance factors
4.2.2. COST function
4.2.3. Hybrid Probabilistic/Importance proposed approach
4.2.4. Hybrid approach behavior and simulation results (Conjunctive AND gate):
4.2.5. Hybrid approach behavior and simulation results (Disjunctive OR gate):
4.3. Illustrative example
4.4. Conclusion
Workflow verification and proposed experimental validation
5.1. Introduction
5.2. Proposition of a verification framework
5.2.1. Conceptual system verification
5.2.2. Experiment’Haal
5.2.3. Illustrative example
5.3. Proposition of validation framework
5.4. Conclusions
Conclusions and perspectives
6.1. Conclusions
6.1.1. Context of the work
6.1.2. Main objective of the work
6.1.3. Proposed contributions to reach the objectives
6.1.4. The prototype representation of the workflow
6.1.5. Experimental validation framework
6.1.6. Obtained results
6.2. Perspectives
Bibliography..

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