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Reliability Analysis for Electronic/Electrical Systems

Reliability in electronic/electric systems refers to the ability of a system or component to perform its required functions consistently and without failure over a specified period under normal operating conditions. It encompasses both the longevity of the system (how long it operates before failure) and its consistency. Reliability is typically quantified using metrices like Mean Time Between Failures (MTBF), Failure Rate, and Availability. High reliability often correlates with high upfront cost but reduces maintenance and operational down time, making it critical for mission-critical and high-stakes applications

Methods for Reliability Analysis

Failure Rate Prediction

Define the failure rate (λ) and its significance in predicting the reliability of E/E systems. Taking Bill of Materials as an input and calculate the failure rate data from reliability prediction data handbooks (SN29500, IEC 62380, MIL-HDBK-217F, 217plus, NPRD, EPRD). After getting basic failure rate from catalogue, apply component parameters or values as per BOM to get the actual failure rate.
Figure 3 Eigenmode Analysis Plots

Reliability Block Diagram

Introduce Reliability Block Diagram (RBD) as a graphical representation of system components and their interconnections. Take the schematic as an input and create the RBD with individual components and connect it with series and parallel connections. Apply the exponential distribution w.r.t Mission time define the system reliability.

Fault Tree Analysis

Fault Tree Analysis is a top-down approach to identify potential causes or failure. Fault Tree create with logical OR, AND and NOT gates. We will define the FTA with components and its failure rate. Here also with using exponential distribution define the MTTF, MTBF, PMHF, PFD, Probability, Unavailability and Criticality.

Failure Mode and Effect Analysis

Failure Mode and Effect Analysis is a systematic method for evaluating the potential failure modes of the system, their causes, and effects on the system operation. FMEA is a bottom to top approach that defines the causes and effects. Based on cause and effects define the Severity, Occurrence and Detection and find the RPN. For RPN calculation we will give SOD values from the FMEA standards (VDA-AIAG, SAEJ 1739).

Failure Mode and Effect Criticality Analysis

Failure Mode and Effect Criticality Analysis is extension of FMEA that adds the assessment of criticality to prioritize failure modes based on their impact on the overall system and performance. FMECA is also a bottom-up approach like FMEA. Here we will take the design FMEA and add the conditional probability and mission time. Calculate the criticality value from severity, mission time, conditional probability, and failure rate.

Conclusion:

A model-based approach for evaluating the reliability of E/E systems in Automotive or other safety-critical domains provides a structured, quantitative framework for assessing system performance, identifying potential failure modes, and ensuring that systems meet functional and safety requirements. By integrating various reliability techniques such as Failure rate calculations, RBD, FTA, FMEA, and FMECA manufacturers can proactively manage and mitigate reliability risks over the system life cycle.

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