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RISS 인기검색어
- 검색키워드
- 저자 : Armaghan Darbandi (검색결과 5 건)
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SCALABLE HOLISTIC SCHEDULING OF SAFETY-CRITICAL SYSTEMS ON IN-VEHICLE TDMA NETWORKS
Armaghan Darbandi,Myung Kyun Kim 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.5
Recently, the authors have proposed a scalable holistic scheduling approach for time-triggered applications on FlexRay, under end-to-end deadline and data dependency constraints. This approach divides the problem to two sub-problems that can be solved separately. The first sub-problem optimally schedules the set of messages to minimize number of used slots, and with respect to information exchanges between tasks and messages, end-to-end deadlines and FlexRay protocol constraints. The second sub-problem optimally schedules the set of tasks to minimize tasks response times, with respect to the solution returned by the first sub-problem. In this paper, our goal is to increase the scalability of our solution to each subproblem. We propose a greedy heuristic approach for the first sub-problem that can find feasible solutions at a low runtime cost. In addition, to resolve assignment conflicts, we apply rescheduling the conflicted application with offset modification and priority promotion procedures. Furthermore, we show that the task scheduling in the second sub-problem can be divided into K independent child sub-problems, where K is the number of ECUs. Our experiments show high scalability and efficiency of our approaches comparing with our optimization-based approaches in the previous work.
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Smart Message Schedule Configuration for Static Segment of Flexray
Armaghan Darbandi,Myung Kyun Kim 한국산학기술학회 2015 SmartCR Vol.5 No.4
FlexRay is designed to support highly sophisticated interaction among electronic component units in modern automobiles. This protocol supports high data rates, up to 10 Mbit/s, and is a hybrid protocol which divides the time into two segments; static segment and dynamic segment. In static segment the time-triggered messages and in dynamic segment event-triggered messages are scheduled. This paper addresses message scheduling subject to precedence constraints in static segment of FlexRay. Our objective is to obtain optimum and sub-optimum scheduling solutions with respect to minimizing the number of used slots, and subject to the FlexRay specifications. We formulate the optimization problem using Integer Linear Programming, and we present a greedy heuristic which helps to reduce the search space of our optimization and achieves sub-optimal solutions more quickly. Our experiments on a prototypical application from a major automotive OEM demonstrate the efficiency of our proposed approaches.
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Improved Schedulability Analysis of Real-Time Sporadic Tasks with EDF Preemptive Scheduling
Darbandi, Armaghan,Kim, Myung-Kyun The Korea Institute of Information and Commucation 2012 Journal of information and communication convergen Vol.10 No.4
This paper proposes an analysis method to check the schedulability of a set of sporadic tasks under earliest deadline first (EDF) scheduler. The sporadic task model consists of subtasks with precedence constraints, arbitrary arrival times and deadlines. In order to determine the schedulability, we present an approach to find exact worst case response time (WCRT) of subtatsks. With the technique presented in this paper, we exploit the precedence relations between subtasks in an accurate way while taking advantage of the deadline of different subtasks. Another nice feature of our approach is that it avoids calculation time overhead by exploiting the concept of deadline busy period. Experimental results show that this consideration leads to a significant improvement compared with existing work.
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SCHEDULE CONSTRUCTION UNDER PRECEDENCE CONSTRAINTS IN FLEXRAY IN-VEHICLE NETWORKS
Armaghan Darbandi,윤석훈,김명균 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.4
As embedded time-triggered applications have widely replaced mechanical systems in modern automobiles, holistic scheduling of tasks and messages of such applications on in-vehicle networks has become a critical issue. For offering QoS (Quality of Service) guarantees, the holistic schedule must satisfy numerous constraints such as protocol specifications, delay constraints and precedence constraints between tasks schedules and messages transmissions. Existing approaches to this problem search through a vast design space of all possible joint task and message schedules. This leads to a high complexity and limits the scalability of such approaches for scheduling the large scale systems. To cope with this problem, we propose an approach that divides the holistic scheduling problem to two sub-problems: the sub-problem of message scheduling and the sub-problem of task scheduling, while precedence relations and end-to-end information passing between task instances and messages are preserved and the end-to-end deadlines are guaranteed. This helps to reduce the workload on the problem solvers and improves efficiency and scalability. In the first sub-problem, our approach optimizes scheduling the set of messages and allocates time windows for scheduling each task with respect to precedence constraints, end-to-end deadlines and FlexRay protocol specifications. The length of each time window helps to preserve the respective tasks schedulability and to provide flexibility for both task and message scheduling. The objective is defined with respect to extensibility issues. In the second sub-problem, our approach optimizes schedule of the set of tasks with respect to their allocated time windows and timing constraints. The objective is defined with respect to latency issues. We optimize the solution to each sub-problem using Mixed Integer Linear Programming optimization framework. Performance evaluations show that, compared with existing holistic scheduling approaches, our approach is more scalable and obtains better solutions in a reasonable amount of time.
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