Publishable JRP Summary Report for ENG56 DriveTrain


Nowadays, electrical energy is mainly generated by fossil resources such as coal, oil, and natural gas, as well as nuclear fuel. However, these energy resources will be exhausted during the next generations and their immense usage leads to environmental pollution, e.g. by carbon dioxide emissions, fracking induced chemical soil contamination, and nuclear waste. To overcome the main problems associated with fossil fuels and nuclear fuels energy and to guarantee sustainable energy for the future, renewable energy resources are essential. Wind energy systems (WES) are regarded as one of the most promising technologies for the generation of renewable energy. Since 1980 every 3-4 years this technology has doubled its nominal output power. Today, the maximum power provided is 7 MW / WES and in the future, it is likely that 20 MW / WES is possible. However, there are only a few WES that reach the desired lifetime of 20 years without at least two mechanical failures of major components. This has a large impact as the failure of mechanical components can lead to downtimes of several days or even weeks resulting in high operation costs and poor reliability. These issues are likely to become worse when offshore installations become more common with the additional access and safety issues associated with an offshore application, therefore more reliable drivetrain components are mandatory. A principal problem is that neither NMIs nor calibration services offer calibrated measuring standards for drivetrain components. This project will go beyond state of the art by addressing this problem.

Need for the project

According to the roadmap and forecast of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany (BMU), the share of wind power in electricity generation has to achieve 25 % by 2025, based on today’s electricity consumption. This step alone would reduce Germany’s carbon dioxide emissions by 20 % and therefore provides evidence of the importance of wind energy for climate protection. The directive 2009/28/EC on renewable energy, implemented by EU Member States in December 2010, sets ambitious targets for all EU Member States, such that the EU will reach a 20 % share of energy from renewable sources by 2020. WES are regarded as one of the most promising technologies for the generation of renewable energy to meet these government targets but reliability with the drivetrain components needs to be improved. The high costs associated with the repair of drivetrain components and also lost power generation due to unplanned maintenance is a common problem for renewable energy suppliers. New approaches will be developed to deliver measurement standards and procedures to enable the reliable estimation of a quantitative measurement uncertainty for highly accurate drivetrain components (for bearings, shafts and gears) as demanded in international guidelines and will be optimized for industrial use.  The measurement uncertainty is an indispensable parameter to characterize the quality of a measurement. Reliable measurements (measurement uncertainty << tolerance), for which highly accurate measurement standards are essential, are the first step towards a trustworthy quality control of the complete manufacturing process.

Scientific and technical objectives

The project focuses on traceable 2D-3D measurements on high accurate components of drivetrains. These are shafts up to 3 m in length and 1 m in diameter, large bearings up to 3 m in diameter, internal and external involute gears up to 3 m in diameter, and brakes up to 1 m in diameter.

The project addresses the following scientific and technical objectives:

  • To provide candidate solutions for measuring and characterising 2D and 3D size, form, waviness and surface roughness parameters in large drivetrain components, establishing functional characterisation parameters in accordance with the GPS requirements defined in ISO 14253 and ISO/TS 17450

  • To research and develop measurement standards and calibration procedures for establishing traceability and estimating measurement uncertainty of drivetrain components

  • To establish and quantify the key additional sources of uncertainty that influence industrial measurement capability, with particular reference to environmental effects

  • To develop a virtual measuring process which includes all the significant uncertainty contributions from the workpiece, environment, measuring strategy, and measuring instrument

  • To test the developed measurement standards in industry and critically analyse the performance compared to traditional standards, such as gauge blocks, step gauges, etc.

Expected results and potential impact

New measurement standards, procedures and good practice guides have been developed and will now be disseminated to standardisation committees and applied in industry. It is assumed, that they will support the identification and quantification of sources of uncertainty as will be the coming development of a virtual measuring process. After having improved the metrology, the manufacturing of drivetrain components can be improved and such the lifetime of renewable energy power generators could be extended, and probably also their failure rate minimised. The best practice guides will allow the consideration of the temperature influence on the measurement uncertainty under harsh environmental conditions and the effects of gravity and clamping effects on large components. Also, the direct application of measurement data within finite element analysis (FEA) packages and design software will allow the prediction of both failure modes and functional performance of drivetrain components.

It is assumed that 30 % of all failures in WES are caused by mechanical problems. The outputs from this project may reduce the production costs by 25 % which would lead to WES becoming cheaper and therefore more frequently installed with the same investment. The mandatory installation of traceable measurements into the manufacturing process will lead to increased turnover for measurement equipment and calibration suppliers. As a result, this project indirectly will increase the cost efficiency of the production of renewable energy. In the case of off-shore WES the possible improvements in the lifetime of the components might even be more important than the monetary aspect for investment decisions.

The outcome of this project will not only provide technological benefits to European industries but it will also facilitate strong economic and social development. Based on certified products, Europe will strengthen and extend its position in the global market. There is a visible need for calibrated material standards to be used in drivetrain production. Training among the consortium and the distribution of knowledge will provide new services to overcome the growing requests which are forecasted for the next years. The project is a cornerstone for the European political goal of reducing CO2 emissions by 40 % by 2030 at least for power generation and might help in accelerating the realisation of this target.

Project results have been disseminated at 18 conferences and in 24 publications thus far.  In addition, the project has been promoted at several trade fairs.  A training on involute gear measurement was carried out as well as a workshop on bearings and several individual gear training sessions have been conducted for industry.

The following results have been achieved in the first thirty months of the project and discussed at the semi-annual JRP meetings held in Prague, Torino, Espoo, Newcastle, and Lyngby.

2D and 3D metrology strategies for drivetrain components 

    Preliminary good practice guides for shaft, gear, and bearing measurements has been drafted and guides for gear and bearing metrology have been completed. These guides have been applied within measurement campaigns in industry which will be used to gain information for the final guides. A fitting procedure for involute profiles has been extended to include superfinished surfaces. For braking systems, a deep surface metrology review has been completed. After having selected gear samples and manufacturing of special gear standards, numerous 2D and 3D measurements have been carried out at these. The metrology techniques have been disseminated within the consortium via metrology trainings. A new profile roughness measurement approach for involute helical gears has been published. An analysis of probe dynamics for waviness, form, and roughness measurements has been conducted.

    The consortium has organised a workshop to assess the current challenges in dimensional, form, waviness and roughness metrology for bearings and to discuss project tasks relating to industrial bearing manufacturing with industry. There were 19 participants including representatives from European and US industries.

      Novel measurement standards and calibration procedures

        Several involute artefacts with and without waviness were designed and manufactured and measurement results of the gear measurands and spectral analyses have been achieved. Moreover, a large bearing measurement standard of 600 mm inner diameter with thermo sensors and a bearing segment have been designed, manufactured and calibrated. Test gears have been manufactured and superfinished. In this regard small test gears have also been manufactured with different finishing processes. The design and manufacturing of a large scale bearing element thickness measurement device (LSBET) has been completed and an intercomparison with a 3D CMM has been conducted. Furthermore, a ball-bar measurement standard has been designed and manufactured and a suitable measurement strategy has been developed. A portable shaft measurement standard (“interferometric step-gauge”) for traceable large shaft measurements has been designed and built. Moreover, a root fillet measurement standard has been manufactured and calibrated. A report about the evaluation of ISO 1328-1:2013 filter and data density recommendations has been completed. In addition, a new profile roughness measurement approach for involute helical gears has been published in the Measurement Science and Technology Journal, ISSN (electronic): 1361-6501 relating to the transformation of profile deviations made in an arbitrary co-ordinate system into a gear functional co-ordinate system.

          Measurement uncertainty under typical conditions in industry

            Surveys on typical conditions for large gear and large bearing metrology, as well as typical supports and clamping fixtures for large rings (like in bearings) have been completed. Four industrial contributors were included for each survey Thermalisation experiments have been carried out by using a climate chamber. The effect of self-weight deformation of large rings has been investigated. Measurements of a planet gear were successfully completed.
            First evaluations regarding the measurement strategy and the key influence factors for direct drives have been conducted. The measurement uncertainty due to elastic deformation of the wind power generator tower has been analysed. The involute gear artefact was measured and model for estimating the measuring uncertainty was derived.

              Virtual measuring process for traceably measuring large drivetrain components

                A software platform for the investigation of gravitational and thermal contributors of the uncertainty has been implemented and applied for practical applications. This was used to generate a 3D model and an FEA dealing with gravitational influences on an end plate of a gearbox. Different theories (e.g. FEM and Kriging) for the thermalisation of large drivetrain components have been tested and discussed. VMP models have been applied to simulate geometrical deformations of a large ring by gravitational influences and by temperature. Recently, the model for the gravitational influence has been improved. Data sets from test gear for evaluation of roughness and waviness data have been prepared for modeling of gear tribological contact to predict gear performance. An analysis of probe dynamics for waviness, form, and roughness measurements has been conducted. The probing system dynamics is important for coordinate measuring machine (CMM) performance, particularly when probing in scanning mode. The dependence of influence of scanning parameters (different scanning speeds within the range of the machine specification, different workpiece orientations inside the measurement volume and different stylus lengths) on measurement uncertainty in the case of involute gear profile scanning was investigated.

                  Validation of measurement strategies and determination of achievable measurement uncertainty in industrial environment

                    First results have been discussed with industry and will help to analyse the performance of traditional standards. A bearing measurement standard produced in the project was measured and the newly developed measurement strategy was validated in industry. The preliminary good practice guides are currently under practical test in an industrial intercomparison campaign under industrial environmental conditions. The gained experience will influence the contents of the coming final good practice guides.

                      JRP start date and duration:

                      01 September 2014, 36 months


                      Dr Karin Kniel, PTB        Tel: +49 531 592 5300           E-mail:

                      JRP website address:


                      JRP-Partner 1 PTB, Germany

                      JRP-Partner 2 CMI, Czech Republic

                      JRP-Partner 3 DTU, Denmark

                      JRP-Partner 4 INRIM, Italy

                      JRP-Partner 5 VTT, Finland

                      JRP-Partner 6 NCL, United Kingdom

                      JRP-Partner 7 NPL, United Kingdom

                      JRP-Partner 8 HexMet, Germany

                      JRP-Partner 9 MDM, Italy

                      JRP-Partner 10 Mitutoyo, Germany

                      JRP-Partner 11 Zeiss, Germany

                      (associated Home Organisation):

                      Jari Juhanko

                      Aalto, Finland

                      (associated Home Organisation):

                      Martin Peterek

                      RWTH, Germany

                      (associated Home Organisation):

                      Henry Peredur Evans

                      CARD, United Kingdom

                       (associated Home Organisation):

                      Tomo Bozovic

                      MER, Montenegro

                      The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union