Example Problem #3 Maxwell 2D Hall Sensor: Rotational Motion using Parametrics

E04_pro, pg. 2 7/25/02 Hall Sensor Description: Constrain the model such that the target wheel rotates one tooth pitch dependent upon a variable called ‘Angle’, and the gap between the target wheel and the pole piece varies. A post processing macro will be created to calculate the average normal component of flux density through the top and bottom cell. We will then solve 181 separate physics problems, and these solutions will be used to create a Maxwell SPICE model. Target Wheel Permanent Magnet Pole Piece Cell Top Cell Bot Hall IC Gap between pole piece and target wheel

E04_pro, pg. 3 7/25/02 Hall Sensor - 2D Modeler Step 1: In the Maxwell Projects window, select the hall sensor magnetostatic problem from Example 1, and then click on ‘Copy’. Check the box next to ‘Model Only’ and give the new name of the project as ‘hall_par’ for Hall sensor parametric analysis.  When you select ‘Model Only’, the software copies the geometry, material setup, boundaries and sources; everything except the field solution.

E04_pro, pg. 4 7/25/02 Hall Sensor - 2D Modeler  Add rotational constraint: ‘Constraint/Add /Rotation’ the anchor point is (0,0) and the target is anywhere inside that Target_Wheel,  change the name of this constraint form ‘c1’ to ‘Angle’. Check this by constraint by rotating the wheel 6, 22, and 55 degrees. Do this by clicking on clicking on ‘Constraint/Modify /Edit Variables’ and change the value of ‘Angle’ from zero to 6.  Enforce this by clicking on ‘Constraint /Enforce’. Repeat this for other values of angle.

E04_pro, pg. 5 7/25/02 Hall Sensor - 2D Modeler  Add a line behind the permanent magnet as a reference which will be used to move the permanent magnet, pole piece, and Hall IC assembly. Click on ‘Object/Polyline’ and use coordinates (50, 3) and (50, -3); turn on the hatches by clicking on ‘Edit/Attributes/By Clicking’. Add vertices using the ‘Reshape/Vertex/Insert’ and ‘Reshape /Vertex/Align’. Use the drawing below as a guide to insert all constraints. Constrain the permanent magnet first, then turn off the visibility by clicking on ‘Edit/Visibility/By Item’; this will prevent you from over constraining the object. Each constraint will dependent upon a independent variable called ‘Gap’ which is the distance from the target wheel to the Hall IC, NOT the distance from the reference line. The Gap varies from 1 to 3 mm.  Add constraints by clicking on ‘Constraint /Add/ Point to Point’. Pick the reference line as the anchor point. Save and Exit when finished

E04_pro, pg. 6 7/25/02 Hall Sensor - Materials Step 2: The same materials that were used in the static problem, will be used here again; so there isn’t any change in the material manager. Step 3: Use the same boundary conditions as before. Step 4: Solve the nominal problem by clicking on ‘Solve/Nominal Problem’ Step 5: Click on ‘Post Process/Nominal Problem’  Next we need to create a macro to calculate the average normal component of flux density across each hall cell. Click on ‘File/Macro/Start Recording’ and use the name Flux_Calc. Click on ‘Data/Calculator’ to enter the plane calculator and perform the following operations:

E04_pro, pg. 7 7/25/02 Hall Sensor – Post-Proc. Macro Load B_x:Qty / BScal ? / ScalarX Integrate:Geometry / Surface / cell_top Integrate (choose the button with the integral symbol) Integrate:Number / Scalar / 1 Geometry / Surface / cell_top Integrate Divide:Divide (choose the division symbol “/” ) Evaluate Write / Enter “Flux_top” for both the name entries Load B_x:Qty / BScal ? / ScalarX Integrate:Geometry / Surface / cell_bot Integrate (choose the button with the integral symbol) Integrate:Number / Scalar / 1 Geometry / Surface / cell_bot Integrate Divide:Divide (choose the division symbol “/” ) Evaluate Write / Enter “Flux_bot” for both the name entries Choose “Done” to exit the Field Calculator and File / Macro / Stop Recording to complete the post-processor macro. This result is the total B_x in the top cell This result is the area of the top cell

E04_pro, pg. 8 7/25/02 Hall Sensor - Parametric Setup Exit the Post – Processor Step 6: Click on ‘Setup Solution/Variables’ and add the variables ‘Gap’, and ‘Angle’, to the table by clicking on ‘Variables/Add’.  Click on ‘Data/Sweep’: Gap from 1 to 3 in 3 steps; click on Accept Angle from 0 to 60 in 61 steps; click on Accept  Click on OK to append these values to the parametric table. Next click on ‘Variables/ Animate’ and then ‘Start’ to verify that all of the constraints used don’t violate any rules.  Save this parametric table and exit this window by clicking on ‘File/Save’ and then ‘File/Exit’ Step 7: Click on ‘Setup Executive Parameters/Post Process Macros’ and then click on the macro Flux_calc and Add it to the list. Step 8: Click on ‘Setup Solution/Options’ and set the number of passes to 10 and the percent error to 0.1%. Click on ‘OK’. Solve the variable table by clicking on ‘Solve/Variables’

E04_pro, pg. 9 7/25/02 Hall Sensor – Examine Results Step 10: Post Process the variables by clicking on ‘Post Process/Variables’. Sort the table by clicking on ‘Data/Sort’ and pick Gap/Add and then Angle/Add. Click on ‘Plot/New’ and select Angle for the Abscissa, and Flux_Top - Flux_Bot for the Ordinate, finally click on Family of Curves and then OK.  This data will be used to create a lookup table in SPICE or Simplorer, so that the entire circuit including electronics and magnetics can be simulated