D2.1 Report on the architecture of the FEV
This document outlines work carried out in the HEMIS project concerning:
- definition of the generic architecture of the FEV identifying the main functional subsystems;
- the Preliminary Hazard Analysis (PHA); and
- the RAMS (Reliability, Availability, Maintainability and Safety) analysis
This work is aligned with the requirements of ISO 26262 standard for the functional safety of electrical and electronic systems in automotive applications.
A generic Fully Electrical Vehicle (FEV) architecture is developed, representing the common features expected of such vehicles. It includes vehicles equipped with range extenders, as well as the purely battery powered.
The in-vehicle network architecture assumes five functional domains: powertrain domain, chassis and safety domain, body and electronics domain, infotainment domain and communication domain. The electrical powertrain which is described here as the Electrical Transmission, is at the heart of the Powertrain Domain. However, other functional domains may also influence the Powertrain Domain. The architecture therefore focuses mainly on the Powertrain Domain, but also includes some elements of other functional domains that may impact on the Electrical Transmission functions. The main domains that have been analyzed are the Powertrain Domain, and the Chassis and Safety Domain; the Electrical Transmission being the primary interest for the purposes of HEMIS.
The generic architecture has been used to produce the Preliminary Hazard Analysis (PHA). The objective of the Preliminary Hazard Analysis is to translate system hazards into design constraints, or functional safety requirements.
The focus of the analysis is identifying the most critical functional hazards relating to acceleration and deceleration, vehicle handling and stopping distance. Non-functional hazards including explosion, fire and exposure to hazardous voltages and substances are also considered. Both functional hazards and non-functional hazards related to EMC issues are identified too.
The identified hazards are classified using the ISO 26262 risk criteria and the classification takes into consideration example situations. Each situation is assessed in terms of the severity of the hazard for the vehicle occupants and the road users, the probability of exposure to the hazard and the controllability of the hazardous situation that might be expected of the driver.
The RAMS analysis consists of the Fault Tree Analysis (FTA), the Failure Mode and Effect Analysis (FMEA) and the definition of mission profile. The two different views, FTA and FMEA analysis, which complement each other, ensure completeness.
A fault tree is a logic diagram that displays the interrelationships between a potential critical event (hazard) in the FEV, and the reasons for this event.
The purpose of the FMEA is to identify possible failure modes of the system components, evaluate their influence on system behavior, and propose proper countermeasures to suppress or mitigate these effects. The severity, probability of occurrence and likelihood of detection can also be assessed in order to drive a risk priority number that can be used to rank the failure modes. This helps to decide which of them require corrective action.
Besides the definition of the architecture of the FEV, it is also necessary to make assumptions related to variables such as driver behavior, reference infrastructure or traffic situation, which are shown in the mission profile.
The architecture definition and analysis reported in this deliverable provide the basis for the work in all of the project work packages.
In the WP3 both the architecture of the Electrical Transmission and its RAMS analysis will be carried out in further detail.
In the WP4 and WP5 the variables to be monitored will be selected and the monitoring system will be developed in the WP6. In this work driving cycles will be taken into account to assess the value of the monitored variables in different FEV road driving scenarios.
Driving cycles have been defined by various national and international bodies in order to allow vehicle characteristics such as fuel efficiency and tailpipe emissions to be compared between vehicles and with related standards. The typical driving cycle consists of a specified sequence of accelerations, decelerations, steady speeds and stops, and is often simulated using a dynamometer in a laboratory. The tests of our system will be based on the New European Drive Cycle (NEDC).
The NEDC has been developed to represent the typical usage of light-duty vehicles in Europe. It consists of four recurring ECE-15 city driving cycles along with an extra urban EUDC driving cycle with a maximum speed of 120 km/h.