How to compute a FRF with MANATEE/Ansys coupling?

Introduction

Starting from v1.07.01, MANATEE software dedicated to the e-NVH design optimization of e-machines includes a coupling with Ansys Mechanical APDL® FEA software. MANATEE therefore includes an APDL code generator to couple MANATEE to an existing Ansys mechanical FEA model or build a new Ansys mechanical FEA lamination model from scratch ("concept stator").

The following tasks can be automated:

  • definition of geometry and meshing (optional, for "concept" stator or rotor)
  • application of material properties including stack orthotropic properties (optional, for "concept" stator or rotor)
  • application of ideal boundary conditions (optional, for "concept" stator or rotor)
  • application of electromagnetic excitations (distributed or as lumped magentc forces)
  • solver and post processing

This feature enables to automatically create scripts to run a wave Frequency Response Function (FRF) on any MANATEE generated geometry or on an existing model. The unit-wave FRF are then used in MANATEE to compute vibrations according to Electromagnetic Vibration Synthesis algorithm. Direct application of operational magnetic forces is also possible.

APDL generation script

To use this feature, you need to define a MANATEE simulation that use the FRF wave mechanical workflow:

Input.Simu.is_mechanics=1; % Run the mechanical module
Input.Simu.type_mech_workflow = 4; % Wave FRF workflow
Input.Simu.type_FEA_model = 2; % Ansys

To further parametrize the coupling, a separated script is added with:

Input.Simu.FRF_FEA_proj = 'My_script_name';

This script mostly defines the mesh and the method to call Ansys. An example can be found in Mechanics\APDL\Projects. This script works in the same way that default_proj or default_machine does: it is a template with all the available input parameters and their description. To create a new project, you first need to copy/paste this script. As always, you have to make sure that the name of your script is unique in your Matlab path to avoid any conflict.

This script contains the following parameters:

Input.Simu.FEA.output_name = 'cylinder_SM_STA_001_APDL_wave'; % Name of the resulting file (in Mechanics/APDL/Results
Input.Simu.FEA.overwrite_results = 1; % 1 To erase /Mechanics/APDL/Results/<project name> current folder before running the simulation
Input.Simu.FEA.ansys_path = 'C:\Program Files\ANSYS Inc\v170\ansys\bin\winx64\MAPDL.exe';

Input.Simu.FEA.N_list = [2,1,1,1,8,2,6,6]; % Mesh discretization of the tooth
Input.Simu.FEA.NLay = 20; % Number of mesh layers in axial direction (Z)
Input.Simu.FEA.ND = 200; % Maximum number of structural modes to be included during modal expansion

Calling Ansys APDL from Matlab

Input.Simu.FEA.ansys_path correspond to the command to call Ansys directly. You can provide option for this call. You can find the options that you need thanks to the "ANSYS Mechanical APDL Launcher": http://www.padtinc.com/blog/the-focus/starting-ansys-products-from-the-command-line For instance, to follow the example provided in the link, you can set:

Input.Simu.FEA.ansys_path = '"C:\Program Files\ANSYS Inc\v140\ANSYS\bin\winx64\ansys140.exe"  -g -p ane3flds -np 2 -acc nvidia -dir "c:\temp" -j "grgewrt1" -s read -m 5000 -db 1000 -l en-us -lstp1 32 -t -d win32 -custom "/temp/myansys.exe"';

MANATEE will automatically set the following options for the call:

  • -b (call ANSYS in batch mode)
  • -j MANATEE (name of the job)
  • -dir Mechanics/APDL/Results/"project_name" (initial working directory)
  • -i Mechanics/APDL/Results/"project_name"/"APDL file name" (input APDL command file for the simulation)
  • -o MANATEE.out (output file name)

Note that in this example, ansys_path is defined with " " around Windows path with space in it to avoid errors (C:\Program Files without " " would be interpreted as using the command C:\Program with the argument Files)

If MANATEE fails to call Ansys, generated APDL file is still available in Mechanics/APDL/Results/"project_name"/"APDL file name" to be run manually in Ansys APDL.

Mesh definition

Lamination mesh is generated starting from a single tooth that is then replicated by rotation. Therefore lamination mesh depends on tooth geometry. Coupling between MANATEE and Ansys Mechanical enables to use any slot shape available in MANATEE. Input.Simu.FEA.N_list defines tooth mesh according to following rules:

  • The value in the list corresponds to the number of mesh elements on the corresponding line
  • Lines are sorted from lamination tooth tip to yoke (cf next figure)
  • The mesh is assumed symmetrical (therefore there is no need to enter twice the values for lines 2 to 7 in this example)
  • First value is always half the number of tooth tips elements. This value is automatically doubled to ensure that tooth tip element number is even, making sure that there is a node at tooth tip center to apply laumped magnetic forces
    Slot 10 mesh setup in Ansys
    Slot 10 mesh setup in Ansys

Input.Simu.FEA.N_list = [2,1,1,1,8,2,6,6] means:

  • 4 elements on line 1
  • 1 element on the lines 2
  • 1 element on the lines 3
  • 1 element on the lines 4
  • 8 elements on the lines 5
  • 2 elements on the lines 6
  • 6 elements on the lines 7
  • 6 element on line 8
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