INTRODUCTION This paper is intended to document the activities, tools and techniques that have been used to quantitatively assess the risk associated with an in-wheel electric motor in line with ISO 26262 Part 3[ 19]. The paper is divided into five main sections as follows: •Part 1 examines the environment in which the motor operates, including the driver and impacts of regulation. •Part 2 examines the vehicle level effects of in-wheel motor failure at the vehicle level using a black-box approach. •Part 3 approaches the problem using analytical methods supplemented by detailed vehicle modeling. •Part 4 syntheses the results of both investigations. •Part 5 briefly considers the impact of the results from part 4 on the functional safety concept. Performing what is essentially the same study twice may at first seem odd. However as we hope will become evident from reading this paper, having that alternative independentapproach has greatly increased our confidence in the final result. PART 1: ENVIRONMENT The concept for an electric vehicle powered by in-wheel electric motor is simple. Place an electric machine (i.e. a motor/generator) at two or four corners of the vehicle in order to replace the centralized drive train with an electric transmission. The potential advantages of this arrangement are numerous; it frees up significant amounts of space within a vehicle, it simplifies the routing of the steering, and it removes the need for a differential. In addition it simplifies the implementation of torque vectoring and provides a mechanism to use the electric machines as a component of the antilock brake system (ABS) and electronic stability control (ESC) [ 14]. Fitting in-wheel electric motors to hybrid vehicles has similar advantages; for example adding two electric in-wheel motors to the rear axle of a front wheel drive vehicle is relatively straight forward conceptually. If the vehicle is 2013-01-0180 Published 04/08/2013 Copyright © 2013 SAE International doi:10.4271/2013-01-0180 saealtpow.saejournals.org Using Vehicle Simulation to Investigate Controllability Michael Ellims and Helen Elizabeth Monkhouse Protean Electric Ltd. Damian Harty and Teena Gade Coventry Univ. ABSTRACT 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. CITATION: Ellims, M., Monkhouse, H., Harty, D. and Gade, T., "Using Vehicle Simulation to Investigate Controllability," SAE Int. J. Alt. Power. 2(1):2013, doi:10.4271/2013-01-0180. ____________________________________ 18Downloaded from SAE International by University of Minnesota, Thursday, August 02, 2018small enough, one could even conceive of the friction components of the service brake being deleted from the rear of the vehicle. At the conceptual le