Schedulability-Driven Frame Packing for Multi-Cluster Distributed Embedded Systems

We present an approach to frame packing for multi-cluster distributed embedded systems consisting of time-triggered and event-triggered clusters, interconnected via gateways. In our approach, the application messages are packed into frames such that the application is schedulable. Thus, we have also proposed a schedulability analysis for applications consisting of mixed event-triggered and time-triggered processes and messages, and a worst case queuing delay analysis for the gateways, responsible for routing inter-cluster traffic. Optimization heuristics for frame packing aiming at producing a schedulable system have been proposed. Extensive experiments and a real-life example show the efficiency of our frame-packing approach

Securing Real-Time Internet-of-Things

Modern embedded and cyber-physical systems are ubiquitous. A large number of critical cyber-physical systems have real-time requirements (e.g., avionics, automobiles, power grids, manufacturing systems, industrial control systems, etc.). Recent developments and new functionality requires real-time embedded devices to be connected to the Internet. This gives rise to the real-time Internet-of-things (RT-IoT) that promises a better user experience through stronger connectivity and efficient use of next-generation embedded devices. However RT- IoT are also increasingly becoming targets for cyber-attacks which is exacerbated by this increased connectivity. This paper gives an introduction to RT-IoT systems, an outlook of current approaches and possible research challenges towards secure RT- IoT frameworks

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To reduce the latency of time-sensitive flows in Ethernet networks, the IEEE TSN Task Group introduced the IEEE 802.1Qbu Standard, which specifies a 1-level preemption scheme for IEEE 802.1 networks. Recently, serious limitations of this scheme w.r.t. flows responsiveness were exposed and the so-called multi-level preemption approach was proposed to address these drawbacks. As is the case with most, if not all, real-time and/or time-sensitive preemptive systems, an appropriate priority-to-flow assignment policy plays a central role in the resulting performance of both 1-level and multi-level preemption schemes to avoid the over-provisioning and/or the sub-optimal use of hardware resources. Yet on another front, the multi-level preemption scheme raises new configuration challenges. Specifically, the right number of preemption level(s) to enable for swift transmission of flows; and the flow-to-preemption-class assignment synthesis remain open problems. To the best of our knowledge, there is no prior work in the literature addressing these important challenges. In this work, we address these three challenges. We demonstrate the applicability of our proposed solution by using both synthetic and real-life use-cases. Our experimental results show that multi-level preemption schemes improve the schedulability of flows by over 12% as compared to a 1-level preemption scheme, and at a higher abstraction level, the proposed configuration framework improves the schedulability of flows by up to 6% as compared to the dominant Deadline Monotonic Priority Ordering.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDP/UIDB/04234/2020); also by FCT through the European Social Fund (ESF) and the Regional Operational Programme (ROP) Norte 2020, under grant 2020.09636.BD.info:eu-repo/semantics/publishedVersio

Schedulability Analysis and Optimization for the Synthesis of Multi-Cluster Distributed Embedded Systems

Abstract 1 We present an approach to schedulability analysis for the synthesis of multi-cluster distributed embedded systems consisting of timetriggered and event-triggered clusters, interconnected via gateways. We have also proposed a buffer size and worst case queuing delay analysis for the gateways, responsible for routing inter-cluster traffic. Optimization heuristics for the priority assignment and synthesis of bus access parameters aimed at producing a schedulable system with minimal buffer needs have been proposed. Extensive experiments and a real-life example show the efficiency of our approaches. 1

Error handling and controller design for controller area network-based networked control system

Networked Control System (NCS) is a feedback control system which dynamic process is running via the communication channel. Surrounded by many choices of network types that can be used to establish an NCS, Controller Area Network (CAN) is a popular choice widely used in most real-time applications. Under harsh environment, fault at transmission line for CAN-based NCS is more prominent compared to fault in network nodes. Fault in bus line of CAN will induce data error which will result in data dropout or/and time delay which consequently lead to performance degradation or system instability. In this thesis, strategies to handle fault occurrence in CAN bus are proposed in order to properly analyse the effect of fault to CAN-based NCS performance. To implement the strategies, first, fault occurrences are modelled based on fault inter-arrival time, fault bursts duration and Poisson law. By using fault and message attributes, Response Time Analysis (RTA) is performed and the probability of NCS message that misses its deadline is calculated based on Homogeneous Poisson Process (HPP). A new error handling algorithm per-sample-error-counter (PSeC) is introduced to replace native error handling of CAN. PSeC mechanism is designed based on online monitoring and counting of erroneous sensor and control signal data at every sampling instance and it gives a bound parameters known as Maximum Allowable Number of Data Retransmission (MADR). If the number of retransmission for NCS message violates the value of MADR, the data will be discarded. With the utilization of PSeC mechanism to replace the Native Error Handling (NEH) of CAN, the probability of NCS message that misses its deadline can be translated to the probability of data dropout of NCS message. Despite the PSeC has prevented network from congestion which can lead to prolonged loop delay, it also introduces one-step loop delay and data dropout. Therefore, the controller that is able to compensate the effect of delay and data dropout should be introduced. Thus, a control algorithm is designed based on Lyapunov stability theory formulated in Linear Matrix Inequality (LMI) form by taking into account network delay and data dropout probability. In order to proof the efficacy of the strategies, Steer-by-Wire (SbW) system is used and simulated in TrueTime MATLAB R /Simulink environment. Simulation results show that the strategies of introducing PSeC mechanism and the designed controller in this work have superior performance than NEH mechanism for CAN-based NCS environment in terms of integral of the absolute error (IAE) and energy consumption

CSP channels for CAN-bus connected embedded control systems

Closed loop control system typically contains multitude of sensors and actuators operated simultaneously. So they are parallel and distributed in its essence. But when mapping this parallelism to software, lot of obstacles concerning multithreading communication and synchronization issues arise. To overcome this problem, the CT kernel/library based on CSP algebra has been developed. This project (TES.5410) is about developing communication extension to the CT library to make it applicable in distributed systems. Since the library is tailored for control systems, properties and requirements of control systems are taken into special consideration. Applicability of existing middleware solutions is examined. A comparison of applicable fieldbus protocols is done in order to determine most suitable ones and CAN fieldbus is chosen to be first fieldbus used. Brief overview of CSP and existing CSP based libraries is given. Middleware architecture is proposed along with few novel ideas