Seminar Notice (4/26(Fri) 2:30pm, Didier Rémond at INSA-Lyon)
Instantaneous Angular Speed and Associated Angular Approaches in Rotating Machines
Didier Rémond, INSA-Lyon
For many years, we have developed an original measurement technique on rotating machines using optical encoders. This measurement was first used to characterize the excitation of geared mechanical power transmissions through the measurement of the Transmission Error. Recently, we have generalized the use of this technology to the measurement of Instantaneous Angular Speed (IAS) by angular sampling. This method makes it possible to very precisely locate non-integer periodicities in the rotation. Thanks to an implicit angular sampling, it also offers the possibility of generalizing the notion of order and introduces the angular or event frequency. This Instantaneous Angular Speed measurement opens up new perspectives in bearing fault detection, even on complex architectures. Several examples of applications such as automotive gearboxes or wind turbines demonstrate the interest of this approach in dealing with non-stationary operating conditions. The whole of this experiment leads us today to propose a description of the localized phenomena, related to a rotating discrete geometry, in the form of differential equations as a function of the angle rather than as a function of time. The first results of this alternative modeling open perspectives in the understanding and the characterization of these periodic phenomena. It led us to propose new models of mechanical behavior of bearings introducing tangential effects and guaranteeing a more phenomenological interpretation of the measured responses. Simple and/or original tools for signal processing will also be presented, giving access to previously unknown quantities. Finally, the modeling of an electric machine will be presented in this theoretical framework, emphasizing the interest of the angular approach in the writing of the electromagnetic model and its coupling to the mechanical model. In particular, we will show that it is more reasonable to think that power supply fluctuations are due to changes in rotor speed than to airgap variations of the machine.