Automation platform and safety considerations

Safety issues of automation

One safety issue with automation is that while it is often viewed as a way to minimize human error in a system, increasing the degree and levels of automation also increases the consequences of error. For example, one nuclear event was largely due to over-reliance on "automated safety" systems. Unfortunately, in the event, the designers had never anticipated the actual failure mode which occurred, so both the "automated safety" systems and their human overseers were innundated with vast amounts of largely irrelevant information. With automation we have machines designed by (fallible) people with high levels of expertise, which operate at speeds well beyond human ability to react, being operated by people with relatively more limited education (or other failings, as in the Bhopal disaster or Chernobyl disaster). Ultimately, with increasing levels of automation over ever larger domains of activities, when something goes wrong the consequences rapidly approach the catastrophic. This is true for all complex systems however, and one of the major goals of safety engineering for nuclear reactors, for example, is to make safety mechanisms as simple and as foolproof as possible (see Safety engineering and passive safety).

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Safety engineering is an applied science strongly related to systems engineering. Safety engineering assures that a life-critical system behaves as needed even when pieces fail.

Safety engineers distinguish different extents of defective operation: A "failure" is "the inability of a system or component to perform its required functions within specified performance requirements", while a "fault" is "a defect in a device or component, for example: a short circuit or a broken wire"[1]. System-level failures are caused by lower-level faults, which are ultimately caused by basic component faults. (Some texts reverse or confuse these two terms. See NUREG-0492 page V-1.) The unexpected failure of a device that was operating within its design limits is a "primary failure", while the expected failure of a component stressed beyond its design limits is a "secondary failure". A device which appears to malfunction because it has responded as designed to a bad input is suffering from a "command fault".[2] A "critical" fault endangers one or a few people. A "catastrophic" fault endangers, harms or kills a significant number of people.

Safety engineers also identify different modes of safe operation: A "probabilistically safe" system has no single point of failure, and enough redundant sensors, computers and effectors so that it is very unlikely to cause harm (usually "very unlikely" means, on average, less than one human life lost in a billion hours of operation). An inherently safe system is a clever mechanical arrangement that cannot be made to cause harm – obviously the best arrangement, but this is not always possible. A fail-safe system is one that cannot cause harm when it fails. A "fault-tolerant" system can continue to operate with faults, though its operation may be degraded in some fashion.