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Reliability Analysis

SAC carries out reviews and reliability related design analyses for circuit schematics like derating, reliability estimation, Failure Mode Effects and Criticality Analysis (FMECA), Worst Case Circuit Analysis (WCCA) for critical circuits and Fault Tree Analysis (FTA) for complex onboard systems/ subsystems. Reliability estimation enables checking adequacy of the systems design against the apportioned reliability goal. Apart from the numerical estimates of the reliability, the analysis brings out a number of other features e.g., reliability block diagram (RBD) shows the functional redundancy.

Derating is the procedure of using parts at stress levels below the manufacturer's rating to ensure the margin in the design and decrease failure rates which in turn enhances reliability. Derating procedures/criteria may vary with different types of parts and their application. Derating or stress analysis is carried out to analyze thermal and electrical stresses on each electronic part of every circuit.

SAC also carries out Failure Mode Effects and Criticality Analysis (FMECA), viz. functional FMECA, interface FMECA and piece-part FMECA for identification of failures, as well as assess criticality of these failures, identifying the end effect along with detection mechanism and mitigation techniques. All primary failure modes are identified and their effect on system performance is evaluated. This enables the identification of components/subsystems contributing significantly towards system single point failures and unreliability.

Similarly, Fault Tree Analysis (FTA) which is an inductive approach is carried out for complex missions to find out critical failures. WCCA (Worst Case Circuit Analysis) is another important activity for critical circuit blocks to evaluate circuit performance throughout the mission life. It accounts for device parameter tolerances, changes in environmental conditions as well as operating conditions.