Using reversible computing to achieve fail-safety

This paper describes a fail-safe design approach that can be used to achieve a high level of fail-safety with conventional computing equipment which may contain design flaws. The method is based on the well-established concept of reversible computing. Conventional programs destroy information and hence cannot be reversed. However it is easy to define a virtual machine that preserves sufficient intermediate information to permit reversal. Any program implemented on this virtual machine is inherently reversible. The integrity of a calculation can therefore be checked by reversing back from the output values and checking for the equivalence of intermediate values and original input values. By using different machine instructions on the forward and reverse paths, errors in any single instruction execution can be revealed. Random corruptions in data values are also detected. An assessment of the performance of the reversible computer design for a simple reactor trip application indicates that it runs about ten times slower than a conventional software implementation and requires about 20 kilobytes of additional storage. The trials also show a fail-safe bias of better than 99.998% for random data corruptions, and it is argued that failures due to systematic flaws could achieve similar levels of fail-safe bias. Potential extensions and applications of the technique are discussed

A synthesis of logic and bio-inspired techniques in the design of dependable systems

Much of the development of model-based design and dependability analysis in the design of dependable systems, including software intensive systems, can be attributed to the application of advances in formal logic and its application to fault forecasting and verification of systems. In parallel, work on bio-inspired technologies has shown potential for the evolutionary design of engineering systems via automated exploration of potentially large design spaces. We have not yet seen the emergence of a design paradigm that effectively combines these two techniques, schematically founded on the two pillars of formal logic and biology, from the early stages of, and throughout, the design lifecycle. Such a design paradigm would apply these techniques synergistically and systematically to enable optimal refinement of new designs which can be driven effectively by dependability requirements. The paper sketches such a model-centric paradigm for the design of dependable systems, presented in the scope of the HiP-HOPS tool and technique, that brings these technologies together to realise their combined potential benefits. The paper begins by identifying current challenges in model-based safety assessment and then overviews the use of meta-heuristics at various stages of the design lifecycle covering topics that span from allocation of dependability requirements, through dependability analysis, to multi-objective optimisation of system architectures and maintenance schedules

Development and Validation of Functional Model of a Cruise Control System

Modern automobiles can be considered as a collection of many subsystems working with each other to realize safe transportation of the occupants. Innovative technologies that make transportation easier are increasingly incorporated into the automobile in the form of functionalities. These new functionalities in turn increase the complexity of the system framework present and traceability is lost or becomes very tricky in the process. This hugely impacts the development phase of an automobile, in which, the safety and reliability of the automobile design should be ensured. Hence, there is a need to ensure operational safety of the vehicles while adding new functionalities to the vehicle. To address this issue, functional models of such systems are created and analysed. The main purpose of developing a functional model is to improve the traceability and reusability of a system which reduces development time and cost. Operational safety of the system is ensured by analysing the system with respect to random and systematic failures and including safety mechanism to prevent such failures. This paper discusses the development and validation of a functional model of a conventional cruise control system in a passenger vehicle based on the ISO 26262 Road Vehicles - Functional Safety standard. A methodology for creating functional architectures and an architecture of a cruise control system developed using the methodology are presented.Comment: In Proceedings FESCA 2016, arXiv:1603.0837

Confidence: Its role in dependability cases for risk assessment

Society is increasingly requiring quantitative assessment of risk and associated dependability cases. Informally, a dependability case comprises some reasoning, based on assumptions and evidence, that supports a dependability claim at a particular level of confidence. In this paper we argue that a quantitative assessment of claim confidence is necessary for proper assessment of risk. We discuss the way in which confidence depends upon uncertainty about the underpinnings of the dependability case (truth of assumptions, correctness of reasoning, strength of evidence), and propose that probability is the appropriate measure of uncertainty. We discuss some of the obstacles to quantitative assessment of confidence (issues of composability of subsystem claims; of the multi-dimensional, multi-attribute nature of dependability claims; of the difficult role played by dependence between different kinds of evidence, assumptions, etc). We show that, even in simple cases, the confidence in a claim arising from a dependability case can be surprisingly low

Towards Declarative Safety Rules for Perception Specification Architectures

Agriculture has a high number of fatalities compared to other blue collar fields, additionally population decreasing in rural areas is resulting in decreased work force. These issues have resulted in increased focus on improving efficiency of and introducing autonomy in agriculture. Field robots are an increasingly promising branch of robotics targeted at full automation in agriculture. The safety aspect however is rely addressed in connection with safety standards, which limits the real-world applicability. In this paper we present an analysis of a vision pipeline in connection with functional-safety standards, in order to propose solutions for how to ascertain that the system operates as required. Based on the analysis we demonstrate a simple mechanism for verifying that a vision pipeline is functioning correctly, thus improving the safety in the overall system.Comment: Presented at DSLRob 2015 (arXiv:1601.00877