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ISO 26262 describes a safety engineering approach in which the safety of a system is considered from the early stages of design through a process of elicitation and allocation of system safety requirements. These are expressed as automotive safety integrity levels (ASILs) at system level and are then progressively allocated to subsystems and components of the system architecture. In recent work, we have demonstrated that this process can be automated using a novel combination of model-based safety analysis and optimization metaheuristics. The approach has been implemented in the HiP-HOPS tool, and it leads to optimal economic decisions on component ASILs. In this paper, first, we discuss this earlier work and demonstrate automatic ASIL decomposition on an automotive example. Secondly, we describe an experiment where we applied two different modes of ASIL decomposition.

The number of software-intensive and complex electronic automotive systems is continuously increasing. Many of these systems are safety-critical and pose growing safety-related concerns. ISO 26262 is the automotive functional safety standard developed for the passenger car industry. It provides guidelines to reduce and control the risk associated with safety-critical systems that include electric and (programmable) electronic parts. The standard uses the concept of Automotive Safety Integrity Levels (ASILs) to decompose and allocate safety requirements of different stringencies to the elements of a system architecture in a top-down manner: ASILs are assigned to system-level hazards, and then they are iteratively decomposed and allocated to relevant subsystems and components. ASIL decomposition rules may give rise to multiple alternative allocations, leading to an optimization problem of finding the cost-optimal allocations.

Failure Modes and Effects Analysis (FMEA) is a well established safety analysis technique used for the assessment of safety critical engineering systems in the automotive industry. Although FMEA has been shown to be useful, the analysis is typically restricted to the effects of single component failures; even partial analysis of combinations or sequences of multiple failures is in practice considered too complex, laborious and costly to perform. In this paper, we describe a new technique in which FMEAs are semi-automatically built from the topology of a system and component-level specifications of failure data. The proposed technique allows an extended form of “combinatorial & sequential FMEA” in which assessment of the effects of combinations and sequences of failures becomes feasible and cost effective.

The California Bureau of Automotive Repair (BAR) has prepared an inspection/maintenance pressure test for gasoline-powered motor vehicle evaporative systems. The test has been added to the California Smog-Check procedure for 1995 and earlier model-year vehicles. The test pressurizes the vehicle evaporative system to 14″ H2O, followed by a leak decay test. If the pressure decay is more than a specified value, the vehicle is considered to have failed the test. Unlike previous pressure testing performed by the U.S. Environmental Protection Agency and some states, this specified value is fuel volatility, temperature and fill-level dependent. This results in a test which can be expected to consistently pass vehicles with leaks below a certain threshold size, and to consistently fail the majority of vehicles with leaks above this threshold.

In 1997 and 1998, the California Air Resources Board (CARB) conducted an extensive evaporative emissions test program to assess the feasibility of reducing evaporative emissions standards from the current 2 gram per test total hydrocarbon (THC) standard. Seven vehicles were tested and five modified in order to determine what emissions levels would be feasible. Emissions reductions of approximately 40% resulted from these modifications. The ARB also conducted studies of non-fuel background emissions and of emissions test variability.

Design concepts for the International Space Station Water Processor (WP) will be validated as discrete flight experiments on-board the Space Shuttle Spacehab. This paper summarizes the results of a study into sample stability within a modified Teflon cell culture bag assembly to support an upcoming Spacehab evaluation of the WP Volatile Removal Assembly (VRA). Results indicate that a lack of adequate preservation results in significant sample analyte degradation over the course of 2-3 week due to increased microbial activity. Results were utilized for the definition of an optimal preservation approach based on the anticipated VRA Flight Experiment samples.

Engine calibrations are inexpensive methods for reducing exhaust emissions since only software modifications are required. The California Air Resources Board staff conducted a test program to investigate the effectiveness of engine calibration techniques to reduce the newly regulated aggressive driving exhaust emissions or “off-cycle” emissions. Consisting of stoichiometric and rich “bias” calibration, these engine calibration techniques were applied to fourteen late-model vehicles. The engine calibration techniques reduced the off-cycle emissions substantially on most vehicles. To comply with the proposed off-cycle standards for California low-emission vehicles and ultra-low-emission vehicles, these techniques will be a cost-effective method to reduce off-cycle emissions.

The ability to remove semi-volatile organic compounds such as alcohol from waste water streams has challenged the design of the International Space Station (ISS) water processor. The current ISS water processor utilizes an aqueous phase catalytic oxidation system to convert these organic compounds to their corresponding organic acids, and to some extent carbon dioxide, which are then easily removed via ion exchange resin. This oxidation system also provides a microbiological control function within the water processor. This paper summarizes testing conducted utilizing both simulated and real waste water on a development catalytic oxidizer. In addition, information is presented on the system schematic and reactor configuration planned for the upcoming Volatile Removal Apparatus flight experiment scheduled for STS 84 to be flown in May 1997.