All functional safety standards have some definition of “risk” and the automotive standard ISO 26262 is no exception. Risk is related to the exposure, the severity of the outcome, and in the case of ISO 26262, the controllability in relation to a specific vehicle hazard or hazards associated with the behavior of the vehicle or part of the vehicle. Thus hazards are central to understanding the risk associated with systems.
When considering traditional power train systems, based on internal combustion engines or centralized electric motors, hazards are most usually limited to unintended acceleration and deceleration. The situation is complicated somewhat with the introduction of electronically controlled differentials, which can induce limited amounts of induced yaw, as can ABS and ESC. In a similar manner, replacing the centralized driveline system with in-wheel electric motors brings with it a similar set of issues.
In this paper we describe the work undertaken to qualitatively identify the hazards associated with in-wheel motors and to quantify the vehicle level effects that could be expected. With this being done to ensure that, when realized as an engineering object, the level of controllability and hence the residual risk to a vehicle fitted with in-wheel motors remains within tolerable bounds.
