Electronic Throttle Control _ A Dependability Case Study

The so-called Electronic Throttle Control unit was a big step towards reducing important parameters like fuel consumption or exhaust emmission. Due to its safety-criticality, a dependability study was initiated by the manufacturer Siemens Automotive. As the most important result, values could be stated for the quantitative estimation of the safety-critical and the availability-relevant cases. The study was based on the existing safety concept, but after this study, a slightly changed system architecture of the ECU was proposed to VDA (Verband der Automobilindustrie), which enhances availability and safety of the ECU significantly, at about the same cost. For this study, a new kind of Markov evaluation method was used, called TEFT (Time-Extended Fault Trees). This was necessary to deal with concepts like multiple faults, faulty states, and time. In this paper, the questions raised by the Electronic Throttle Control system are described, together with our way to solve these problems.