Failure Modes and Effects Analysis: An Experience from the E-Bike Domain
Software failures can have catastrophic and costly consequences. Functional Failure Mode and Effects Analysis (FMEA) is a standard technique used within Cyber-Physical Systems (CPS) to identify software failures and assess their consequences. Simulation-driven approaches have recently been shown to be effective in supporting FMEA. However, industries need evidence of the effectiveness of these approaches to increase practical adoption. This industrial paper presents our experience with using FMEA to analyze the safety of a CPS from the e-Bike domain. We used Simulink Fault Analyzer, an industrial tool that supports engineers with FMEA. We identified 13 realistic faults, modeled them, and analyzed their effects. We sought expert feedback to analyze the appropriateness of our models and the effectiveness of the faults in detecting safety breaches. Our results reveal that for the faults we identified, our models were accurate or contained minor imprecision that we subsequently corrected. They also confirm that FMEA helps engineers improve their models. Specifically, the output provided by the simulation-driven support for 38.4% (5 out of 13) of the faults did not match the engineers' expectations, helping them discover unexpected effects of the faults. We present a thorough discussion of our results and ten lessons learned. Our findings are useful for software engineers who work as Simulink engineers, use the Simulink Fault Analyzer, or work as safety analysts.