Reliability Engineering

Take the case of an aircraft - its navigation and control systems are certainly perceived as too significant to fail. Hence, they are constructed with immense redundancy. For instance, an airplane has more than one navigation computer, so that if one fails, others can take over immediately without any disruption.

For instance, in a system where the failure rate \( \lambda \) is 0.01 (this means one failure per 100 unit hours), after 50 unit hours the reliability of the system can be computed using the formula \( R(t) = e^{-0.01*50} \) which amounts to approximately 0.61 or 61%.

The ABS (Anti-lock Braking System) in a vehicle, for instance, is critical to preventing accidents when the driver brakes suddenly. ABS is meticulously designed using reliability engineering principles, including the use of redundancy and diversity, to ensure that even in the event of a part failure, overall system performance is not compromised.

The Jet Propulsion Laboratory (JPL) uses reliability engineering in the design process for rovers including "Curiosity" and "Perseverance", ensuring these complex systems can operate independently on Mars' harsh environment.

Google, for example, uses Site Reliability Engineering (SRE) to automate and maintain their large-scale systems. SRE uses software engineering techniques to make systems scalable, reliable, and efficient.

Consider a component with a constant failure rate \( \lambda = 0.001 \) (one failure per thousand unit hours). The reliability of this component after 100 hours can be calculated as \( R(t) = e^{-0.001*100} \), which is approximately 0.90 or 90%. The failure density function at the same time, \( f(t) = 0.001 e^{-0.001*100} \), is approximately 0.001 or 0.1%.

For the case of the component discussed previously, the calculated 90% reliability means that out of 100 components running for 100 hours, we can expect 90 to still be operational, while around 10 would most likely have failed.

If, for instance, an unusually high number of failures were to occur towards the beginning of the lifetime (infant mortality), a manufacturer might need to take a closer look at the production process to identify and address any defects.

As a Reliability Engineer, the task would be to identify potential points of failure in this system and develop strategies to mitigate them. This would involve evaluating each component for failure modes, conducting a Failure Mode and Effects Analysis (FMEA), establishing the criticality of each failure mode, and defining ways to enhance the reliability of the entire system.

For instance, redundancy is one principle commonly applied in these plants. Important systems are designed with redundant backup subsystems to take over if the primary system fails. The backup systems are often independent of the main system to prevent a single-point failure from taking down the entire plant.

Case Study 2 – Telecommunication Industry: A telecommunication company noticed intermittent disruptions in its services. This was impacting customer satisfaction and also leading to a potential loss of business. The reliability engineering team involved identified a specific type of signal interference as a core cause and worked closely with the software engineers to redesign the signal processing algorithm.