The field of autonomous vehicle system engineering is one of keen research and development interest for many areas of automotive engineering. Along with electrification, the short to medium term future of automotive engineering across many disciplines is likely to include adaptations for increasing levels of automation. We can also see existing pilot programs increasing their operational design domain to encompass a greater number of tasks in more of our transport infrastructure, as well as evolving legislative requirements. For a brake system, the task of autonomous driving (with or without human presence) mandates redundancy in many subsystem elements. Indeed, defining a meaningful brake concept for an autonomous vehicle requires a systemic analysis of both the operational organisation of the control system, as well as the performance and redundancy requirements for such a system. In this paper, the authors will present a redundant brake system concept which addresses the necessary braking tasks from both an operational and redundancy viewpoint. The concept vehicle is envisaged for fully autonomous driving as well as human driving, utilising modular electric drivetrain and associated brake energy recovery. We will demonstrate a systematic construction of the major braking tasks, and how these tasks are distributed and replicated in a redundant brake system architecture. Having established and organised the major braking tasks, the paper will then consider the necessary system performance in a fully functional and (partially) failed state. For each state, braking performance targets will be set against a variety of longitudinal and lateral dynamic metrics. The paper will then consider each major task during a transition from a fully functional state to a failed state and offer a categorisation regime for the braking tasks during such a transition event. With this categorisation, it is then possible to define which tasks must be continual during a handover event, and those where an interruption of task may be safely allowed. Finally, for the most safety critical tasks, a safety analysis will be presented, which allows for a Fault Tolerant Time Interval (FTTI) of the task to be defined. By defining the brake system concept using this task-centric approach, it is possible to consider the architectural layout options for the concept vehicle and consider these layout options against a cohesive requirement set.

BrakeBetter: Mr. Deaglán Ó Meachair; Applus IDIADA: Mr. Carlos Jose Sierra, Mr. Prashanth Dhurjati, Mr. Alessandro Pezzano, Fabio Squadrani