Rotor Eccentricity modeling in Flux. Easy parametrization with new 6 degrees of freedom feature
Altair EmployeeNew Flux Feature : Six degrees of freedom mechanical set
In the 2022.1 Flux Version, there is a new type of Mechanical set that allows you to drive your system with 6 degrees of freedom :
Figure 1 - Six degrees of freedom mechanical set
This mechanical set's movement is driven by 3 Parameters I/O that are automatically created in the Data Tree :
Figure 2 - Six degrees of freedom movement parameters
Those parameters respectively drive the movement along X-Axis, Y-Axis and the rotation around Z-Axis.
Rotor eccentricity modeling in Flux
Type of eccentricities
With this feature, you can now generate a rotor eccentricity in your eMachine models. There are 2 common eccentricity types : Static eccentricity is when the rotor axis is shifted from the stator axis, but the rotor still rounds about its own axis. That means that eccentricity coordinates doesn't vary with time. On the other hand, Dynamic eccentricity is when axis are shifted but the rotor rounds about the stator axis. In this case, eccentricity coordinates vary with time and the rotor center draws a circle over time. There is also mixed eccentricity that is a combinaison of those 2 phenomena.
Figure 3 - Eccentricity types and parameters
New macro presentation (Create_eccentered_Mechanical_set.PFM.zip )
This macro automatically creates the mechanical set that will eccenter the rotor during solving. It creates the 6DOF mechanical set and sets up the parameters with formula that simulate whichever type of eccentricity you want. It is simple to use as it only requires the following inputs :
Figure 4 - Create_eccentered_mechanical_set macro input window
Once this macro has been run, you only need to assign the new mechanical set to your rotor regions (shaft, magnets, ...), define the stator current with the same frequency as the rotation and run your solving scenario.
Post Processing
Once you have solved your project, electro-magnetics parameters can be manipulated the same way that you are used to with your other Flux projects. For example, the impact of eccentricity on your magnetic flux density can be observed by plotting it on a path in the airgap :
Figure 5 - Magnetic flux density along a path in the airgap comparison between an eccentered (blue curve) and non-eccentered (pink curve) model
Step by step eccentricity modeling guide
Attached to this article, you may find a step by step powerpoint "Eccentricities in Flux - step by step modeling.ppsx" that guides you in modeling a rotor eccentricity on an example model "IkerMAQ_fullmotor_1_ini.FLU.zip". In the example a static eccentricity (10% of the 2.5mm airgap) is setup with the macro. Then a transient magnetic scenario is solved and some electromagnetic parameters are postprocessed. Furthemore, you may also find an OML Compose script that plots the harmonic content of the Maxwell Pressure in your airgap. This graph is obtained by exporting a text file from a 2D spatio-temporal curve of Maxwell Pressure (figure 6a) in Flux. Those data are then imported in Compose (figure 6b) and a 2D-FFT is then performed to obtain the figure 6c that gives harmonic content (using the SpatialPlotComputation.zip)
