Lionel Havet - Academia.edu (original) (raw)

Papers by Lionel Havet

With the increasing amount of electronics, making best usage of the bandwidth becomes of primary ... more With the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this "traffic shaping" strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive

2016 Sixth International Symposium on Embedded Computing and System Design (ISED)

The innovation in the field of automotive embedded systems has been increasingly relying on softw... more The innovation in the field of automotive embedded systems has been increasingly relying on software-implemented functions. The control laws of these functions typically assume deterministic sampling rates and constant delays from input to output. However, on the target processors, the execution times of the software will depend on many factors such as the amount of interferences from other tasks, resulting in varying delays from sensing to actuating. Three approaches supported by tools, namely TrueTime, T-Res, and SimEvents, have been developed to facilitate the evaluation of how timing latencies affect control performance. However, these approaches support the simulation of control algorithms, but not their actual implementation. In this paper, we present a model interpretation engine running in a co-simulation environment to study control performances while considering the run-time delays in to account. Introspection features natively available facilitate the implementation of selfadaptive and fault-tolerance strategies to mitigate and compensate the run-time latencies. A DC servo controller is used as a supporting example to illustrate our approach. Experiments on controller tasks with injected delays show that our approach is on par with the existing techniques with respect to simulation. We then discuss the main benefits of our development approach that are the support for rapid-prototyping and the re-use of the simulation model at run-time, resulting in productivity and quality gains.

arXiv (Cornell University), Dec 1, 2012

This paper presents a complete processing chain for decoding intracranial data recorded in the co... more This paper presents a complete processing chain for decoding intracranial data recorded in the cortex of a monkey and replicates the associated movements on a JACO robotic arm by Kinova. We developed specific modules inside the OpenViBE platform in order to build a Brain-Machine Interface able to read the data, compute the position of the robotic finger and send this position to the robotic arm. More precisely, two client/server protocols have been tested to transfer the finger positions: VRPN and a light protocol based on TCP/IP sockets. According to the requested finger position, the server calls the associated functions of an API by Kinova to move the fingers properly. Finally, we monitor the gap between the requested and actual fingers positions. This chain can be generalized to any movement of the arm or wrist.

Combining static priority and weighted round-robin like packet scheduling in AFDX for incremental... more Combining static priority and weighted round-robin like packet scheduling in AFDX for incremental certification and mixed-criticality support

The Kalray MPPA2 manycore processor implements a clustered architecture, where clusters of cores ... more The Kalray MPPA2 manycore processor implements a clustered architecture, where clusters of cores share a local memory, and communicate through a RDMA-capable network-on-chip (NoC). This NoC has been designed to allow guaranteed delays by the adequate configuration of traffic limiters at ingress and the choice of routing. We first present the challenges related to the routing of concurrent flows and a strategy that solves it. Routing challenges include deadlock-free routing, which is always an issue on wormhole switching networks, fairness of resource allocation between flows, and ensuring the feed-forward property required by deterministic network calculus (DNC). Second, we present a linear formulation based on DNC for computing end-to-end delay bounds of concurrent feed-forward flows on the MPPA2 NoC. Finally, we compare this linear formulation to a classic formulation originally designed for the AFDX avionics networks.

Deficit Round Robin (DRR) policy can be used at the outgoing ports of communication switches to s... more Deficit Round Robin (DRR) policy can be used at the outgoing ports of communication switches to schedule distinct classes of frames, providing each class with a guaranteed share of the network bandwidth. The independence between traffic classes helps to improve the incremental design process, incremental certification and scheduling flows with mixed criticalities. DRR leads however to a less efficient use of hardware resources, this is why we also envisage the combined use of DRR and Static Priority (SP). We then provide a first quantitative assessment on a realistic case5study about the use of DRR, possibly combined with SP, in avionics networking and shed some light on its range of applicability.

We introduce a novel Model-Driven Development (MDD) flow which aims at more simplicity, more intu... more We introduce a novel Model-Driven Development (MDD) flow which aims at more simplicity, more intuitive programming, quicker turnaround time and real-time predictability by leveraging the use of model-interpretation and providing the language abstractions needed to argue about the timing correctness on a high-level. The MDD flow is built around a language called Cyber-Physical Action Language (CPAL). CPAL serves to describe both the functional behaviour of activities (i.e., the code of the function itself) as well as the functional architecture of the system (i.e., the set of functions, how they are activated, and the data flows among the functions). CPAL is meant to support two use-cases. Firstly, CPAL is a development and design space exploration environment for CPS with main features being the formal description, the editing, graphical representation and simulation of CPS models. Secondly, CPAL is a real-time execution platform. The vision behind CPAL is that a model is executed a...

Computer Standards & Interfaces, 2020

Cyber-Physical Systems are usually subject to dependability requirements such as safety and relia... more Cyber-Physical Systems are usually subject to dependability requirements such as safety and reliability constraints. Over the last 50 years, a body of efficient fault-tolerance mechanisms has been devised to handle faults occurring at run-time. However, properly implementing those mechanisms is a time-consuming task that requires a great deal of know-how. In this paper, we propose a general framework which allows system designers to decouple functional and non-functional concerns, and express nonfunctional properties at design time using domain-specific languages. In the spirit of generative programming, functional models are then automatically "augmented" with dependability mechanisms. Importantly, the real-time behavior of the initial models in terms of sampling times and meeting deadlines is preserved. The practicality of the approach is demonstrated with the automated implementation of one prominent software fault-tolerance pattern, namely N-Version Programming, in the CPAL model-driven engineering workflow.

Sensors (Basel, Switzerland), Jan 20, 2018

Model-Driven Engineering (MDE) is widely applied in the industry to develop new software function... more Model-Driven Engineering (MDE) is widely applied in the industry to develop new software functions and integrate them into the existing run-time environment of a Cyber-Physical System (CPS). The design of a software component involves designers from various viewpoints such as control theory, software engineering, safety, etc. In practice, while a designer from one discipline focuses on the core aspects of his field (for instance, a control engineer concentrates on designing a stable controller), he neglects or considers less importantly the other engineering aspects (for instance, real-time software engineering or energy efficiency). This may cause some of the functional and non-functional requirements not to be met satisfactorily. In this work, we present a co-design framework based on timing tolerance contract to address such design gaps between control and real-time software engineering. The framework consists of three steps: controller design, verified by jitter margin analysis ...

IFAC Proceedings Volumes, 2009

In order to improve mobility in cities, new initiatives of Intelligent Transportation Systems are... more In order to improve mobility in cities, new initiatives of Intelligent Transportation Systems are emerging based on free-access electric vehicles. Making the vehicles everywhere at any time available requires a dispatching of these vehicles over a city, this could be accomplished at a large scale by trailing several vehicles without mechanical link with a leading driven vehicle (platooning). This paper first proposes a methodology to assess the performances of such urban platoon of vehicles using different platooning algorithms, taking into account a real operational architecture which means communications delays, tasks jitters, data sampling and finite resources. As a result some timing properties requirements are provided for the choice of each vehicle operational architecture for the deployment of the platooning function. Secondly an analysis is made on platooning operational architecture in order to evaluate the robustness of the platoon of vehicle under transient faults leading to information losses for the control of the vehicles.

This paper presents a complete processing chain for decoding intracranial data recorded in the co... more This paper presents a complete processing chain for decoding intracranial data recorded in the cortex of a monkey and replicates the associated movements on a JACO robotic arm by Kinova. We developed specific modules inside the OpenViBE platform in order to build a Brain-Machine Interface able to read the data, compute the position of the robotic finger and send this position to the robotic arm. More pre- cisely, two client/server protocols have been tested to transfer the finger positions: VRPN and a light protocol based on TCP/IP sockets. According to the requested finger position, the server calls the associ- ated functions of an API by Kinova to move the fin- gers properly. Finally, we monitor the gap between the requested and actual fingers positions. This chain can be generalized to any movement of the arm or wrist.

2010 IEEE 15th Conference on Emerging Technologies & Factory Automation (ETFA 2010), 2010

Wireless Sensor and Actuator Networks (WSANs) combine sensors and actuators interconnected by wir... more Wireless Sensor and Actuator Networks (WSANs) combine sensors and actuators interconnected by wireless networks in order to perform distributed sensing and acting tasks. Closed-loop controllers can therefore be deployed on WSANs; such systems have to meet specific requirements in terms of performance, dependability, energy and cost which raises great challenges due to the unreliability of wireless communications. A way to ensure that a system meets the required properties is to model it and go through its analysis. Building a model requires both deep knowledge on the system as well as on the used framework. Therefore there is a need for frameworks well-suited to the targeted systems and to the properties to verify. We propose an approach meeting these conditions and a simulation framework, Samovar, based on Matlab / Simulink, allowing the modeling of the network protocols (Mac and routing services) and the resources sharing policy thanks to the TrueTime toolbox. Several classes of components (application, nodes, networks and middleware) and a clear semantics for their composition are identified. Furthermore, the design of Samovar was also driven by the need to transfer easily software components model between the concrete systems and its simulated model. The modeling and simulation method as well as the Samovar framework are illustrated on a Pursuit Evasion Game.

With the increasing amount of electronics, making best usage of the bandwidth becomes of primary ... more With the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this "traffic shaping" strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive experiments shown in this chapter give insight into the fundamental reasons why offsets are efficient, and demonstrate that offsets actually provide a major performance boost in terms of response times. These experimental results suggest that sound offset strategies may extend the lifespan of CAN further, and may defer the introduction of FlexRay and additional CAN networks.

2012 9th International Conference on Ubiquitous Intelligence and Computing and 9th International Conference on Autonomic and Trusted Computing, 2012

Existing sensors and actuators, that can be used in an AAL (ambient assisting living) environment... more Existing sensors and actuators, that can be used in an AAL (ambient assisting living) environment, work on heterogeneous network protocols, e.g., WiFi, Bluetooth, EIB/KNX and Zigbee. For a given sensor/actuator, the choice of its underlying communication protocol is optimized according to its bandwidth and/or energy needs. However, integrating sensors/actuators of heterogeneous network protocols into an AAL system arises interoperability problems. In this paper, we present MPIGate, a multi-protocol gateway and interface for assisted living applications. Besides its multiple communication drivers for supporting the different protocols, MPIGate also proposes a database for storing the last updated sensor data as well as an user interface for both transparent data access and easy application development. MPIGate has been deployed in a smart home technical test bed at our LORIA labs. We presents some first results and discuss the lessons learnt.

IFAC Proceedings Volumes, 2007

This paper presents NETCARBENCH, a benchmark devoted to improve the assessment, the understanding... more This paper presents NETCARBENCH, a benchmark devoted to improve the assessment, the understanding and the comparability of techniques and tools used in the design of in-vehicle communication networks. This benchmark is motivated by the increasing use of algorithms intended to optimize the resource utilization in the design and configuration of automotive communication systems. For instance, typical objectives are the minimization of the network bandwidth usage and the reduction of the worst case response times of the frames. The main contribution of NETCARBENCH is to allow a finegrained user-defined parameterization of the generated message sets by means of XMLconfiguration files that specify the characteristics of the message sets and the variability thereof. Experiments suggest that the outcomes of NETCARBENCH are satisfactory in terms of their closeness to the input specifications. NETCARBENCH and its user manual are freely available under the GNU General Public License.

With the increasing amount of electronics, making best usage of the bandwidth becomes of primary ... more With the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this "traffic shaping" strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive

2016 Sixth International Symposium on Embedded Computing and System Design (ISED)

The innovation in the field of automotive embedded systems has been increasingly relying on softw... more The innovation in the field of automotive embedded systems has been increasingly relying on software-implemented functions. The control laws of these functions typically assume deterministic sampling rates and constant delays from input to output. However, on the target processors, the execution times of the software will depend on many factors such as the amount of interferences from other tasks, resulting in varying delays from sensing to actuating. Three approaches supported by tools, namely TrueTime, T-Res, and SimEvents, have been developed to facilitate the evaluation of how timing latencies affect control performance. However, these approaches support the simulation of control algorithms, but not their actual implementation. In this paper, we present a model interpretation engine running in a co-simulation environment to study control performances while considering the run-time delays in to account. Introspection features natively available facilitate the implementation of selfadaptive and fault-tolerance strategies to mitigate and compensate the run-time latencies. A DC servo controller is used as a supporting example to illustrate our approach. Experiments on controller tasks with injected delays show that our approach is on par with the existing techniques with respect to simulation. We then discuss the main benefits of our development approach that are the support for rapid-prototyping and the re-use of the simulation model at run-time, resulting in productivity and quality gains.

arXiv (Cornell University), Dec 1, 2012

This paper presents a complete processing chain for decoding intracranial data recorded in the co... more This paper presents a complete processing chain for decoding intracranial data recorded in the cortex of a monkey and replicates the associated movements on a JACO robotic arm by Kinova. We developed specific modules inside the OpenViBE platform in order to build a Brain-Machine Interface able to read the data, compute the position of the robotic finger and send this position to the robotic arm. More precisely, two client/server protocols have been tested to transfer the finger positions: VRPN and a light protocol based on TCP/IP sockets. According to the requested finger position, the server calls the associated functions of an API by Kinova to move the fingers properly. Finally, we monitor the gap between the requested and actual fingers positions. This chain can be generalized to any movement of the arm or wrist.

Combining static priority and weighted round-robin like packet scheduling in AFDX for incremental... more Combining static priority and weighted round-robin like packet scheduling in AFDX for incremental certification and mixed-criticality support

The Kalray MPPA2 manycore processor implements a clustered architecture, where clusters of cores ... more The Kalray MPPA2 manycore processor implements a clustered architecture, where clusters of cores share a local memory, and communicate through a RDMA-capable network-on-chip (NoC). This NoC has been designed to allow guaranteed delays by the adequate configuration of traffic limiters at ingress and the choice of routing. We first present the challenges related to the routing of concurrent flows and a strategy that solves it. Routing challenges include deadlock-free routing, which is always an issue on wormhole switching networks, fairness of resource allocation between flows, and ensuring the feed-forward property required by deterministic network calculus (DNC). Second, we present a linear formulation based on DNC for computing end-to-end delay bounds of concurrent feed-forward flows on the MPPA2 NoC. Finally, we compare this linear formulation to a classic formulation originally designed for the AFDX avionics networks.

Deficit Round Robin (DRR) policy can be used at the outgoing ports of communication switches to s... more Deficit Round Robin (DRR) policy can be used at the outgoing ports of communication switches to schedule distinct classes of frames, providing each class with a guaranteed share of the network bandwidth. The independence between traffic classes helps to improve the incremental design process, incremental certification and scheduling flows with mixed criticalities. DRR leads however to a less efficient use of hardware resources, this is why we also envisage the combined use of DRR and Static Priority (SP). We then provide a first quantitative assessment on a realistic case5study about the use of DRR, possibly combined with SP, in avionics networking and shed some light on its range of applicability.

We introduce a novel Model-Driven Development (MDD) flow which aims at more simplicity, more intu... more We introduce a novel Model-Driven Development (MDD) flow which aims at more simplicity, more intuitive programming, quicker turnaround time and real-time predictability by leveraging the use of model-interpretation and providing the language abstractions needed to argue about the timing correctness on a high-level. The MDD flow is built around a language called Cyber-Physical Action Language (CPAL). CPAL serves to describe both the functional behaviour of activities (i.e., the code of the function itself) as well as the functional architecture of the system (i.e., the set of functions, how they are activated, and the data flows among the functions). CPAL is meant to support two use-cases. Firstly, CPAL is a development and design space exploration environment for CPS with main features being the formal description, the editing, graphical representation and simulation of CPS models. Secondly, CPAL is a real-time execution platform. The vision behind CPAL is that a model is executed a...

Computer Standards & Interfaces, 2020

Cyber-Physical Systems are usually subject to dependability requirements such as safety and relia... more Cyber-Physical Systems are usually subject to dependability requirements such as safety and reliability constraints. Over the last 50 years, a body of efficient fault-tolerance mechanisms has been devised to handle faults occurring at run-time. However, properly implementing those mechanisms is a time-consuming task that requires a great deal of know-how. In this paper, we propose a general framework which allows system designers to decouple functional and non-functional concerns, and express nonfunctional properties at design time using domain-specific languages. In the spirit of generative programming, functional models are then automatically "augmented" with dependability mechanisms. Importantly, the real-time behavior of the initial models in terms of sampling times and meeting deadlines is preserved. The practicality of the approach is demonstrated with the automated implementation of one prominent software fault-tolerance pattern, namely N-Version Programming, in the CPAL model-driven engineering workflow.

Sensors (Basel, Switzerland), Jan 20, 2018

Model-Driven Engineering (MDE) is widely applied in the industry to develop new software function... more Model-Driven Engineering (MDE) is widely applied in the industry to develop new software functions and integrate them into the existing run-time environment of a Cyber-Physical System (CPS). The design of a software component involves designers from various viewpoints such as control theory, software engineering, safety, etc. In practice, while a designer from one discipline focuses on the core aspects of his field (for instance, a control engineer concentrates on designing a stable controller), he neglects or considers less importantly the other engineering aspects (for instance, real-time software engineering or energy efficiency). This may cause some of the functional and non-functional requirements not to be met satisfactorily. In this work, we present a co-design framework based on timing tolerance contract to address such design gaps between control and real-time software engineering. The framework consists of three steps: controller design, verified by jitter margin analysis ...

IFAC Proceedings Volumes, 2009

In order to improve mobility in cities, new initiatives of Intelligent Transportation Systems are... more In order to improve mobility in cities, new initiatives of Intelligent Transportation Systems are emerging based on free-access electric vehicles. Making the vehicles everywhere at any time available requires a dispatching of these vehicles over a city, this could be accomplished at a large scale by trailing several vehicles without mechanical link with a leading driven vehicle (platooning). This paper first proposes a methodology to assess the performances of such urban platoon of vehicles using different platooning algorithms, taking into account a real operational architecture which means communications delays, tasks jitters, data sampling and finite resources. As a result some timing properties requirements are provided for the choice of each vehicle operational architecture for the deployment of the platooning function. Secondly an analysis is made on platooning operational architecture in order to evaluate the robustness of the platoon of vehicle under transient faults leading to information losses for the control of the vehicles.

This paper presents a complete processing chain for decoding intracranial data recorded in the co... more This paper presents a complete processing chain for decoding intracranial data recorded in the cortex of a monkey and replicates the associated movements on a JACO robotic arm by Kinova. We developed specific modules inside the OpenViBE platform in order to build a Brain-Machine Interface able to read the data, compute the position of the robotic finger and send this position to the robotic arm. More pre- cisely, two client/server protocols have been tested to transfer the finger positions: VRPN and a light protocol based on TCP/IP sockets. According to the requested finger position, the server calls the associ- ated functions of an API by Kinova to move the fin- gers properly. Finally, we monitor the gap between the requested and actual fingers positions. This chain can be generalized to any movement of the arm or wrist.

2010 IEEE 15th Conference on Emerging Technologies & Factory Automation (ETFA 2010), 2010

Wireless Sensor and Actuator Networks (WSANs) combine sensors and actuators interconnected by wir... more Wireless Sensor and Actuator Networks (WSANs) combine sensors and actuators interconnected by wireless networks in order to perform distributed sensing and acting tasks. Closed-loop controllers can therefore be deployed on WSANs; such systems have to meet specific requirements in terms of performance, dependability, energy and cost which raises great challenges due to the unreliability of wireless communications. A way to ensure that a system meets the required properties is to model it and go through its analysis. Building a model requires both deep knowledge on the system as well as on the used framework. Therefore there is a need for frameworks well-suited to the targeted systems and to the properties to verify. We propose an approach meeting these conditions and a simulation framework, Samovar, based on Matlab / Simulink, allowing the modeling of the network protocols (Mac and routing services) and the resources sharing policy thanks to the TrueTime toolbox. Several classes of components (application, nodes, networks and middleware) and a clear semantics for their composition are identified. Furthermore, the design of Samovar was also driven by the need to transfer easily software components model between the concrete systems and its simulated model. The modeling and simulation method as well as the Samovar framework are illustrated on a Pursuit Evasion Game.

With the increasing amount of electronics, making best usage of the bandwidth becomes of primary ... more With the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this "traffic shaping" strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive experiments shown in this chapter give insight into the fundamental reasons why offsets are efficient, and demonstrate that offsets actually provide a major performance boost in terms of response times. These experimental results suggest that sound offset strategies may extend the lifespan of CAN further, and may defer the introduction of FlexRay and additional CAN networks.

2012 9th International Conference on Ubiquitous Intelligence and Computing and 9th International Conference on Autonomic and Trusted Computing, 2012

Existing sensors and actuators, that can be used in an AAL (ambient assisting living) environment... more Existing sensors and actuators, that can be used in an AAL (ambient assisting living) environment, work on heterogeneous network protocols, e.g., WiFi, Bluetooth, EIB/KNX and Zigbee. For a given sensor/actuator, the choice of its underlying communication protocol is optimized according to its bandwidth and/or energy needs. However, integrating sensors/actuators of heterogeneous network protocols into an AAL system arises interoperability problems. In this paper, we present MPIGate, a multi-protocol gateway and interface for assisted living applications. Besides its multiple communication drivers for supporting the different protocols, MPIGate also proposes a database for storing the last updated sensor data as well as an user interface for both transparent data access and easy application development. MPIGate has been deployed in a smart home technical test bed at our LORIA labs. We presents some first results and discuss the lessons learnt.

IFAC Proceedings Volumes, 2007

This paper presents NETCARBENCH, a benchmark devoted to improve the assessment, the understanding... more This paper presents NETCARBENCH, a benchmark devoted to improve the assessment, the understanding and the comparability of techniques and tools used in the design of in-vehicle communication networks. This benchmark is motivated by the increasing use of algorithms intended to optimize the resource utilization in the design and configuration of automotive communication systems. For instance, typical objectives are the minimization of the network bandwidth usage and the reduction of the worst case response times of the frames. The main contribution of NETCARBENCH is to allow a finegrained user-defined parameterization of the generated message sets by means of XMLconfiguration files that specify the characteristics of the message sets and the variability thereof. Experiments suggest that the outcomes of NETCARBENCH are satisfactory in terms of their closeness to the input specifications. NETCARBENCH and its user manual are freely available under the GNU General Public License.