VBA Macro for construction of an EM 3D model of a tyre and part of the vehicle

Transcription

1 VBA Macro for construction of an EM 3D model of a tyre and part of the vehicle Guillermo Vietti, Gianluca Dassano, Mario Orefice LACE, Politecnico di Torino, Turin, Italy. guillermo.vietti@polito.it Work partially funded by Regione Piemonte in the frame of the contract RIJ09N 1

2 Contents: 1. Goals 2. Geometry and main parts of the structure 3. Description of the parts of the script. Main features 5. Some examples of outcomes representation and uses. Conclusions 2

3 Goals: Study of the EM propagation channel (from a Sensor Node inside the tyres to the TX / RX device mounted on the vehicle), in two different frequency bands. Analyis of the effects of different: types of tyre, angular positions of tyre, steering wheel angles, weights of vehicle, air pressure, types of ground. Estimation of attenuation introduced by all mechanical obstacles between these two radio devices. Evaluation of the multipath effect in the signals received by both devices. Plot of the near/far field pattern in this complex and large structure at different configurations. 3

4 Brief description of main tyre elements (explode animated view) 1.Inner Liner - part of a tyre consisting of one or several plies of rubberized cord fixed on bead rings. 2.Breaker - inner part of a tyre which consisting of rubberized plies of steel or textile cord and located between tread and carcass, designated for load impact softening while driving. 3.Tread - outer rubber part of a tyre with molded pattern, which provides adhesion to the road and prevents carcass damages..cap ply (breaker ply) - protective ply located between steel breaker and tread, provides breaker protection from mechanical damages and prevents rubber separation. 5.Bead - hard part of a pneumatic tyre case which provides its fixing on a wheel rim..side wall - outer rubber. All metallic elements are simulated with PEC material in order to simplify the calculation

5 We have developed a Visual Basic (VBA) script that controls all CST STUDIO SUITE TM tools to design all mechanical elements in the space around the tyre in a vehicle in a full parametric way. 5

6 Main script parts 1. Definition of all parameters of the geometry (definition of variables): lengths, widths, thickness, radius, and of all materials like dielectric and magnetic relative constants, losses. 2. Definition of variable/s of iterative cycle (for instance: the angular position of sensor inside of tyre, variable from 0 to 30 to know the EM propagation in each situation). 3. Setting of all units of the project (mm, GHz, s).. Setting the background material (Vacuum).

7 5. Definition of structure : Definition of all materials, choosing the dielectric and magnetic properties given by the tire maker. Design of the skeleton of the tyre extruding the radial closed curves. These curves reflect the deformation of the tire due to vehicle weight and the air pressure inside. With a loft operation of two consecutive curves a solid shape is created, adding all angular shapes we will create a complete solid object named sidewall. Insertion of the tread with the same technique. Insertion of metallic belts inside the tire rubber. All steel cords in carcass and breaker are simulated with a continuous metallic cylindrical shape after verifying the similar EM behavior in the work frequency bands. Insertion of the fully inner liner inside the tire. Trim of fully inner liner shape with a vacuum object. Creation of the rim. Switch from global coordinates placed in the center of tyre to local coordinates in the radial location inside the tyre under the belt. Creation of SN box with the antennas using the local coordinate system. Reactivation of global coordinate system in the center of tyre. Design of all radial closed curves that will create the fender shape with many loft operations between two consecutive planar curves. Design with many cylindrical and angular objects of the shape of a simplified disc brake. Design of a very simplified suspension. 7

8 . Setting of frequency range for the simulation 7. Definition of two discrete ports using two picked point in each antenna extremes of sensor, and setting of input impedance of these port.. Definition of the boundary conditions. All boundary planes around the structure are set to open to simulate the open space except the ground plane; it will be set like an electric plane (E tan =0) or a conducting wall to take into account the losses of the real ground. 9. Definition of many 3D electric field monitors at each frequency of interest with an iterative cycle.. Definition of many electric field probes in all coordinated directions in planned positions. 11. Set all mesh properties, enabling the subgridding tool and fixing a dense local mesh in the main SN, in order to take into account small details of these elements, which with an sparse general mesh can be ignored.

9 . Updating of mesh. 7. Setting the transient solver parameters.. Starting of simulation. 9. Reading magnitudes and phases for each defined probe and saving these like.txt file.. Reading the electric field monitors for each frequency and saving these tridimensional complex vectors like.txt file. 11. Save the project with a name that identifies the value of cycle parameter. 12. Restarting the parametric cycle routine. 9

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11 Script capable of changing the tyre deformation due to the vehicle weight and internal air pressure changing the value of one variable in the script definition Perspective view Left view Front view 11

12 It is very easy to change the tire orientation changing the value of the variable defined to control the steering wheel angle in the script sentence Perspective view Bottom view 12

13 In a similar way, it is easy to modify the suspension load changing the value of variable defined in order to control the distance from tyre to fender Perspective view Front view 13

14 Some examples of the outcomes obtained with this script. Different types of representations 1

15 Example 1: Comparison between the sensor inside the tire and in the free space Sensor inside the tire Sensor in the free space Perspective view (Sensor detail) 15

16 E(x,y,z) at.5 GHz in the main coordinates planes (Sensor in the free space) 1

17 E(x,y,z) at.5 GHz in the main coordinates planes (Sensor inside the tyre) 17

18 E(x,y,z) at.5 GHz in the boundary planes (Sensor in the free space) 1

19 E(x,y,z) at.5 GHz in main coordinates planes (Sensor inside the tyre) 19

20 Example 2: Comparison between two widths of the tyre with a dipole inside, two orientations EM model Size 1 Width: 23 mm Dipole oriented along the axis of rotation High: 9.7 mm Size 2 Width: 291 mm (Scaled 120 %) High: 9.7 mm Dipole oriented perpendicular to the axis of rotation 20

21 E-field average magnitude at 2. GHz on y=0 cut plane (clamp to range Min:0, Max:00 V/m) Dipole oriented along the axis of rotation Size 1: Width: 23 mm High: 9.7 mm Size 2:Width: 291 mm (Scaled 120 %) High: 9.7 mm Dipole oriented perpendicular to the axis of rotation 21

22 E-field average magnitude at 2. GHz on z=0 cut plane(clamp to range Min:0, Max:00 V/m) Dipole oriented along the axis of rotation Size 1: Width: 23 mm High: 9.7 mm Size 2:Width: 291 mm (Scaled 120 %) High: 9.7 mm Dipole oriented perpendicular to the axis of rotation 22

23 E-field average magnitude at 2. GHz on x=131 cut plane(clamp to range Min:0, Max:0 V/m) Dipole oriented along the axis of rotation Size 1: Width: 23 mm High: 9.7 mm Size 2:Width: 291 mm (Scaled 120 %) High: 9.7 mm Dipole oriented perpendicular to the axis of rotation 23

24 E-field average magnitude at 2. GHz on x=151 cut plane(clamp to range Min:0, Max:0 V/m) Dipole oriented along the axis of rotation Size 1: Width: 23 mm High: 9.7 mm Size 2:Width: 291 mm (Scaled 120 %) High: 9.7 mm Dipole oriented perpendicular to the axis of rotation 2

25 Example 3: Study of received signal outside of the tire in different positions for different azimuthal position of the source (SN). Probes situation (orientation along X, Y, Z axis) Perspective view Left view Front view θ = -90, -5, 0, 5, 90 d=15 cm θ = -90, -5, 0, 5, 90 25

26 Probe Positions. Numbers. Front view. 9 SN 12 θ = -90, -5, 0, 5,

27 Excitation signal in the port (.5 GHz carrier) 27

28 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :1). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 2

29 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :2). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 29

30 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :3). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 30

31 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 31

32 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :5). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 32

33 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 33

34 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :7). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 3

35 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 35

36 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :9). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 3

37 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 37

38 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :11). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 3

39 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :12). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 39

40 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :13). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 0

41 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :1). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 1

42 Probes for SN Angular position θ = 0, Signals vs. time Probe Signal (Number :15). SN angular position: 0 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 2

43 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :1). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 3

44 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :2). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns

45 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :3). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 5

46 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns

47 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :5). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 7

48 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns

49 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :7). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 9

50 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 50

51 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :9). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 51

52 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 52

53 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :11). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 53

54 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :12). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 5

55 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :13). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 55

56 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :1). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 5

57 Probes for SN Angular position θ = 5, Signals vs. time Probe Signal (Number :15). SN angular position: 5 degrees Y Sensor Node Z X 2 Amplitude Along: X direction Along: Y direction Along: Z direction time ns 57

58 Example : Electric field magnitude animated pattern at.5 GHz in different cut planes 5

59 Example 5: Comparison with a real car model at 2. GHz 59

60 Example : Comparison with measurements Total Field level measured on a plane at 20 cm from tyre side. Tyre edge Tyre edge SN SN With tyre Without tyre 0

61 Conclusions: This program allows to analyze a complex and large structure iteratively eliminating the need to rebuild the geometry for different mechanical and electrical conditions reducing strongly the computing time. The possibilty of automatically saving the main outcomes like text file for each cycle of simulation permits at the end of the overall simulation to elaborate easily these data with other softwares as MatLab, Microsoft Excel, ecc. It is very easy define many field monitors and probes at different locations to find the optimal position of radio devices. This VBA script allows to non expert CST users to change and to optimize the complex structure and save the outcomes in text format. It is possible to choose the degree of accuracy of the representation of the geometry, in order to minimize the meshing load. 1

62 Thank you for you attention. 2