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Analysis And Research On Critical Non-functional Property Of Safety-Critical Embedded Real-Time Software

Posted on:2012-11-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:S L GuiFull Text:PDF
GTID:1228330368498522Subject:Computer application technology
Abstract/Summary:PDF Full Text Request
Safety-critical embedded real-time systems (SCERTS) are used more and more widely in so many safety-critical domains, which have rigorous requirements on task execution time and failure effect, such as aerospace, medical equipment, automotive electronics, and nuclear system. This class of systems has rigorous requirements on its non-functional properties (NFPs) besides the correct requirements on function. If the expected NFPs cannot be satisfied, the systems mightbe fail, which would result in great loss of people’s lives or property. Therefore, how to analyze and evaluate whether the NFPs of SCERTS are satisfied is an import research direction, whose results could provide the necessary system information and design guide to system designers.For solving the above issues, this dissertion considers two main NFPs: real-time and reliability, systematically and completely analyzes the currect most important engineering techniques and theoretical methods for NFPs from the perspective of software engineering and of software computational model respectively, presents two real-time analysis techniques and a reliability model, so that system designers could analyze and evaluate the performance of systems as early as possible at design phase, then illustrates the detailed analysis process in a prototype of avionics by the presented analysis techniques. The main contributions of this dissertion are in the following:1. For embedded real-time software (ERTS) on small-scale distributed real-time systems, presents a schedulability analysis technique based on automata theory, establishes a formal task model on distributed systems, by using action automata and environment automata models the task execution semantics and the external event arrival patterns respectively, translates the schedulability analysis to the reachability analysis of the locations in automata network, proves the decidability of schedulability under certain scheduling policies, gives the decidable conditions for scheduling policies, implements a schedulability analysis tool, named SCT, for distributed systems, avoid the pessimistic results of traditional analysis techniques by overly estimating the worst case which could never occur in real execution. The comparisons show that SCT can be used to model systems and analyze schedulability easily, and provides the most accurate results;2. For embedded real-time software (ERTS) on large-scale distributed real-time systems, starts with the schedulability analysis of tasks on a specific class of these systems: bi-directional multistage pipeline system, accounts for the task execution overlap among nodes, derives an end-to-end delay bound formula for tasks, then extend this system model to generalized system model. The simulation results show that this technique could derive better end-to-end delay bound for tasks under most cases, so that more tasks could be allowed into the system;3. For generalized ERTS, presents a general reliability model to analyze reliability of the task execution model at software design phase, based on the relationship between real-time property and the execution time cost for fault tolerance. In this reliability model, task failure rates and the corresponding fault-tolerant mechanisms are both defined to model non-permanent failures, generated by hardware or design defects in software itself, and the corresponding failure handling costs. By analyzing the probability of tasks being schedulable in the worst arrival pattern of failures, reliability and schedulability are combined into one analysis framework. An algorithm for reliability analysis under static-priority scheduling policy is presented, as well as an improved one. When no assumptions of faults existing in task model, this reliability model regresses to a generic schedulability model;4. Chooses a typical class of SCERTS,“avionics”, to model, analyzes another important NFP: partition configuration policy, defines an optimal partition configuration policy, gives the proof of policy ENATF being the optimal partition configuration policy, implements a partition configuration and simulation tool PCT, then gives an instance of avionics, by which shows in detail how to use the schedulability analysis technique, reliability analysis technique and the optimal partition configuration policy presented in this dissertion.Currently, there are lots of challenges existing in research domain of NFP of SCERTS, the methods and techniques presented in this dissertion provide a new perspective to research NFP for other researchers, and theoretical and technological support to the research and development of real-time systems with self-owned intellectual property.
Keywords/Search Tags:safety-critical, real-time systems, non-functional properties, schedulability, formal methods, reliability model, avionics, partition configuration policy
PDF Full Text Request
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