Roche, M., Mammetti, M., and Crifaci, C., "Wavelet Analysis for the Characterization of Abrupt and Transient Phenomena in Electric Drivelines," SAE Technical Paper 2015-01-2238, 2015, doi:10.4271/2015-01-2238.
Emissions and fuel consumption reduction for the year 2020 have led to the development of new powertrain solutions. The development of new electric concepts presents vehicle integration challenges, involving among others, NVH. Energy flow is controlled by inverters that transform the energy from DC to AC by working at frequencies of the order of kilohertz with a control strategy that can abruptly switch, and motors introduce high orders and electro-magnetic forces due to their topology, inducing phenomena that are not present in internal- combustion engine vehicles. In Particular, a common characteristic of permanent magnet motors is cogging torque, which is due to the attraction of the rotor poles and stator slots that induces a torque ripple causing comfort challenges at low speed and low torque conditions. Special care must be paid to the integration challenges when adapting an ICE platform to an electric powertrain due to the new excitation sources and frequency levels that the electric powertrain introduces.In this work, the continuous wavelet transform which is a relatively recent mathematical tool that presents a minimized time support was used due to its capability to analyze abrupt and transient phenomena. Wavelet analysis provides a different focus for studying the abovementioned abrupt effect of the control strategy and cogging torque which is useful for improving the overall NVH experience of the driver of an electric vehicle. This paper describes new sources of excitation in electric vehicles and their effect on noise and vibration, and demonstrates the advantages of wavelet transform to deepen the study of transient information for meeting the challenges that the development of new vehicle concepts presents.