Mohamed Khalgui

BROMETH: Methodology to design safe reconfigurable medical robotic systems

This research paper deals with the development of a medical robotized control system for supracondylar humeral fracture treatment. Concurrent access to shared resources and applying reconfiguration scenarios can jeopardize the safety of the system.

RWiN: New Methodology for the Development of Reconfigurable WSN

This paper presents new challenges for the development of reconfigurable wireless sensor networks (RWSNs) that adapt dynamically their behaviors to their environment under different properties. An RWSN is a set of networked nodes that execute reconfigurable software tasks for the control of local sensors. We propose a new design methodology named RWiN of an RWSN using unified modeling language (UML) to analyze, construct, develop, and verify easily RWSN architectures. For that, we formulate a metamodel of RWSN based on UML to describe a zone-based architecture that uses a communication protocol for the optimization of distributed reconfigurations. To control the design complexity, we model each agent of this architecture by nested state machines. To verify the temporal constraints by communicating agents, each one is modeled by a timed automaton. The paper’s contribution is applied to a case study, which is simulated with TRMSim-WSN and UPPAAL environment to expose the originality of this new architecture.

A multi-agent architectural solution for coherent distributed reconfigurations of function blocks

The paper deals with distributed Multi-Agent Reconfigurable Embedded Control Systems following the International Industrial Standard IEC61499 in which a Function Block (abbreviated by FB) is an event-triggered software component owning data and a control application is a network of distributed blocks that should satisfy functional and temporal properties according to user requirements. We define an architecture of reconfigurable multi-agent systems in which a Reconfiguration Agent is affected to each device of the execution environment to apply local reconfigurations, and a Coordination Agent is proposed for coordinations between devices in order to guarantee safe and adequate distributed reconfigurations. A Communication Protocol is proposed to handle coordinations between agents by using well-defined Coordination Matrices. We specify both reconfiguration agents to be modelled by nested state machines, and the Coordination Agent according to the formalism Net Condition-Event Systems (Abbreviated by NCES) which is an extension of Petri nets. To validate the whole architecture, we check by applying the model checker SESA in each device functional and temporal properties to be described according to the temporal logic “Computation Tree Logic”. We have also to check all possible coordinations between devices by verifying that whenever a reconfiguration is applied in a device, the Coordination Agent and other concerned devices react as described in user requirements. We present a tool applying simulations of this distributed architecture in order to check interactions and reactivities of agents. The paper’s contributions are applied to two Benchmark Production Systems available in our research laboratory.

Safe reconfigurations of agents-based embedded control systems

The development of safe reconfigurable embedded control systems is a tremendous task since they must fulfill functional as well as safety requirements. In this paper the authors propose an agent-based approach to handle safe reconfigurations of control systems. The specification of the solution is covered by a set of UML-compliant metamodels. More specifically, the different software architectural configurations of the control system are described as a set of inter-connected software components. The reconfiguration is thus assured by an autonomous software agent which interacts with users and applies several forms of reconfiguration at different granularity levels of the systems architecture. Three architectural levels are defined in order to consider all possible reconfiguration scenarios of embedded control systems. In order to bring the reconfigurable system into safe behaviors after any reconfiguration, the agent has the ability of monitoring the systems environment and to apply appropriate reconfigurations under well-defined constraints.

Dual mode for vehicular platoon safety

In order to cope with uncertainties in a platoon, this paper proposes a reconfigurable multi-agent architecture to address the platoon safety problem by handling two modes: the normal mode and the degraded mode. At this stage of research, the normal mode is characterized by the interaction between agents over a Vehicle-to-Vehicle (V2V) communication network while the degraded mode simply involves sensors for a local perception. The switching from the normal mode to the degraded one is triggered when the communication quality is considered not fully reliable. A PID (Proportional Integral Derivative) controller is proposed to regulate the inter-vehicle distance and orientation. Two models are proposed in this paper: in the first one, the management operations such as splitting and joining are set up while the second is mainly modeled to assess the implemented controller quality. In this paper, the safety of a platoon is represented by the quality of tracking and the inter-vehicle distance. The mentioned features are assessed for both modes through a formal verification using the Uppaal software. We prove the efficiency of the proposed platoon model for several situations such as merging, following or leaving the platoon by verifying different properties using the model checking. The evaluation of the second model, simulated by the Webots software, proves the impact of the number of vehicles on the platoon performance and the vehicle tracking quality. We conclude that when the platoon reaches a certain number of vehicles, the safety criterion is no more reliable.

GR-TNCES: New extensions of R-TNCES for modelling and verification of flexible systems under energy and memory constraints

This study deals with the formal modeling and verification of Adaptive Probabilistic Discrete Event Control Systems (APDECS). A new formalism called Generalized Reconfigurable Timed Net Condition Event Systems (GR-TNCES) is proposed for the optimal functional and temporal specification of APDECS. It is composed of behavior and control modules. This formalism is used for the modeling and control of unpredictable as well as predictable reconfiguration processes under memory and energy constraints. A formal case study is proposed to illustrate the necessity of this formalism and a formal verification based on the probabilistic model checker Prism.

UML-Based Design and Validation of Intelligent Agents-Based Reconfigurable Embedded Control Systems

The paper examines UML-based design and validation of reconfigurable embedded control systems which can have multiple software architectural configurations such that each one is designed by a set of inter-connected software components. To handle dynamic reconfiguration scenarios, the authors define a software agent which interacts with users and applies several forms of reconfiguration at different granularity levels of the systems architecture. The agent has the ability of monitoring the systems environment and to apply appropriate and valid reconfiguration scenarios under well-defined constraints. Three architectural levels are defined in order to consider all possible reconfiguration forms of embedded systems. The authors define a set of UML-compliant metamodels to describe the knowledge about the reconfiguration agent, the system architecture, the reconfiguration scenarios, and the reconfiguration events. Validity of reconfigurations scenarios are checked using an UML-based environment which allows evaluating architectural and reconfiguration constraints. The proposed reconfiguration approach is applied to the FESTO production system.

Specification Approach using GR-TNCES: Application to an Automotive Transport System.

The features of probabilistic adaptive systems are especially the uncertainty and reconfigurability. The structure of a part of the system may be totally unknown or partially unknown at a particular time. Openness is also an inherent property, as agents may join or leave the system throughout its lifetime. This poses severe challenges for state-based specification. The languages in which probabilistic reconfigurable systems are specified should be clear and intuitive, and thus accessible to generation, inspection and modification by humans. This paper introduces a new approach for specifying adaptive probabilistic discrete event systems. We introduce the semantics of GR-TNCES to optimize the specification of unpredictable timed reconfiguration scenario running under resources constraints. We also apply this approach to specify the requirements of an automotive transport system and we evaluate its benefits.

Modeling and Simulation of an Energy Efficient Skid Conveyor using ZIZO

This paper introduces a method for modeling and simulation of a production system with different energy modes. We aim to save the energy in an assembly automobile production line platform using sensitive sensors. A new prototype model is proposed using an extension of Petri nets called GR-TNCES (generalized reconfigurable timed net condition event systems). We also present a simulation of this model with a proposed tool ZIZO to show the energy gain compared to standard production line model.

A New Approach for Optimal Implementation of Multi-core Reconfigurable Real-time Systems.

This paper deals with a multi-core reconfigurable real-time system specified with a set of implementations, each of which is raised under a predefined condition and executes multiple functions which are in turns executed by threads. The implementation as threads generates a complex system code. This is due to the huge number of threads and the redundancy between the different implementations which may lead to an increase in the energy consumption. Thus we aim in this paper to optimize the system code by avoiding the redundancy between implementations and reducing the number of threads while meeting all related real-time constraints. The proposed approach adopts mixed integer linear programming (MILP) techniques in the exploration phase in order to provide a feasible task model. An optimal reconfigurable POSIX-based code of the system is manually generated as an output of this technique. An application to a case study and performance evaluation confirm and validate the expected results.