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Uptime Engineering GmbH
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8010 Graz, Austria
Tel: +43 (0)316 711 921

eMail: office@uptime-engineering.com

Hybrid & Electric Drivetrain

E-Car loading

Overview

  • The hybrid electric or fully electric drivetrain is now the most popular form of new drive train concept currently under development at most automotive companies. The success of such technology is largely due to the fact that almost all of the related sub-systems have been in operation for decades in other industries. Thus, outstanding performance and efficiency is expected within a short time to market.
  • As usual during such a technology transition phase, the established combustion engine has remained the main energy source for hybrid vehicles. However, recent concepts indicate that this trend is due to fade out. The next years will bring a large variety of drive trains, including purely electrical cars of radical light-weight design.
  • Several core components of electric drive trains, like the electric motor, have been in operation for more than a century. Yet achieving a highly dynamic and efficient traction unit with mobile HV-energy storage, to be operated reliably under various climate conditions, is a significant challenge. Moreover, a strong OEM trend towards vertical technology integration demands electrics and electronics, control and high voltage technology, electro-chemistry to be integrated into the environment of vehicle development.

Challenges

  • Validation time: electric drivetrains are validated in distributed programs, which are run in parallel by the OEM plus several Tier 1 suppliers. Project management is even more demanding under these circumstances than in classical drivetrain projects. A systematic monitoring of the component maturity level is inevitable for keeping track on the demanding validation schedules. Common tools, like a centralized database for durability test definitions and test results are key to success.
  • Load profiles: varying customer preferences and usage profile can strongly influence the system load of hybrid drivetrain components, since two energy sources are available for vehicle traction. This is a major challenge to validation as the reference load spectra are no longer determined by the vehicle speed distribution. This demands a comprehensive and systematic investigation of actual field load profiles extended beyond SOP to gain satisfying statistics on vehicle operation.
  • New components, new load cases: frequent switching between traction and generative braking is a good example for a new load case, which stresses the electric/electronic components. A systematic investigation into the corresponding failure modes delivers the basis for target oriented simulation and durability tests that are tailored toward reliability demonstration considering realistic load conditions.
  • Known components, new load cases: depending on the drivetrain concept, ICE components can be subject to drastic changes in load spectra (idle operation, motoring, starts frequency, quasi static operation, regenerative braking, etc.). Classical validation procedures typically do not address these features to the necessary extent.
  • Variants: different drivetrain configurations are a major source of deficient reliability as their validation requirements quickly exceed available time and budget. For hybrid drivetrain designs this is aggravated by the additional variance in vehicle operation modes.

Solutions

  • Limitation of variants: An important element is the assessment of co-validation, i.e. the transfer of validation results from a tested configuration to another variant. Taking-over of test results is justified only for parts, that are equal with respect to the failure modes under consideration. Therefore the careful tracking of parts-equivalence is required for this approach.
  • Failure modes: the results of a detailed assessment of the potential failure modes affecting the drivetrain can be fed back to the product development to support design for reliability. Furthermore the correct understanding of the failure physics is a vital element for the definition of suitable tests and for design of the overall validation programmes.
  • Field load profiles: a careful assessment of the expected combined with understanding of the system control strategy also contributes to the design of effective tests.
  • Software: Many of the techniques and solutions available at Uptime Engineering to support reliability optimisation hybrid & electric drivetrains are included in the modules of our Uptime Solutions software.