Functional Safety for Hybrid and Electric Vehicles

Hybrid and electric vehicles present a promising trade-off between the necessary reductions in emissions and fuel consumption, the improvement in driving pleasure and performance of today's and tomorrow's vehicles. These hybrid vehicles rely primarily on electronics for the control and the coordination of the different sub-systems or components. The number and complexity of the functions distributed over many control units is increasing in these vehicles. Functional safety, defined as absence of unacceptable risk due to the hazards caused by mal-function in the electric or electronic systems is becoming a key factor in the development of modern vehicles such as electric and hybrid vehicles. This important increase in functional safety-related issues has raised the need for the automotive industry to develop its own functional safety standard, ISO 26262.

The aim of the paper is to briefly introduce the ISO 26262 standard and the specific hazards associated with hybrid and electric vehicles. The paper will highlight how the risk-based approach of ISO 26262 can influence the safety integrity level of some safety related functions specific to hybrid and electric vehicles. It will also highlight how well established safety related functions, such as torque monitoring of a conventional internal combustion engine can be influenced through vehicle hybridization. A vehicle safety concept for the torque monitoring of an electric vehicle will then be presented. The results of the implementation of this functional safety concept in an electric vehicle developed by the company FEV GmbH will be shown as example. The first measurements made in the vehicle show that the monitoring concept fulfills the reaction time requirement to ensure that unintended torque increase do not lead to uncontrollable vehicle acceleration.