Master Thesis - OUFTI-1
Master Thesis - OUFTI-1 Master Thesis - OUFTI-1
4.3.8 Sensitivity analysis During the description of the modeling strategy, it was highlighted that several parameters play an important role on the accuracy of the obtained FE model. In this section, the eect that a variation of some of these parameters causes on the PCB dynamic response, will be studied. Mass of the sensor used during the experimental test The rst analysis concerns the mass of the sensor used to realize the measurements during the test. Indeed, this sensor brings a local increase of mass and stiness on the PCB, just as each electronic component. To obtain accurate results, this fact has normally to be taken into account in our model, which is never the case when a FE model is realized. So, the question is: what is the real eect of the sensor on the PCB dynamic response To try to answer to this question, a sensitivity analysis will be performed by integrating sensors of several mass in our model. Then, the shape of the fourth mode of the OBC 2 card will be studied for 3 cases: a sensor of 0.2 g (as the sensor used in our case), one of 1 g and the last of 2 g. To realize this, a concentrate mass is added to the model. However, this mass has to be placed at a strategic point to obtain results which highlight its inuence on the mode shape. Indeed, if this mass was placed on a vibration node, nothing could be observed because it would not be excited. So, to realize this choice, the initial shape of the fourth mode is necessary. This one is given in Figure 4.22. Figure 4.22: Initial shape of the OBC 2 card's fourth mode 97
According to this particular shape, it was chosen to place the sensor at the level of the measurement point 1 (see Figure 4.15), which is situated in one of the two corners on the opposite side of the P C 104 connector, because it is this part of the electronic card which presents the greatest deformations and so, which participates the most to this mode. Table 4.8 presents the natural frequencies obtained in each case and their deviations with regard to the initial one, and Figure 4.23 shows the eect on the mode shape. Cases Natural frequencies (Hz) Frequency deviations (%) Initial 907.68 / Sensor of 0.2 g 893.81 1.53 Sensor of 1 g 862.66 4.96 Sensor of 2 g 847.62 6.62 Table 4.8: Natural frequencies obtained by adding sensors of several mass to the FE model Figure 4.23: Mode shapes obtained by adding sensors of several mass to the FE model 98
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- Page 131 and 132: Appendix A Schemas of solar panels
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4.3.8 Sensitivity analysis<br />
During the description of the modeling strategy, it was highlighted that several parameters<br />
play an important role on the accuracy of the obtained FE model. In this section, the<br />
eect that a variation of some of these parameters causes on the PCB dynamic response,<br />
will be studied.<br />
Mass of the sensor used during the experimental test<br />
The rst analysis concerns the mass of the sensor used to realize the measurements<br />
during the test. Indeed, this sensor brings a local increase of mass and stiness on the<br />
PCB, just as each electronic component. To obtain accurate results, this fact has normally<br />
to be taken into account in our model, which is never the case when a FE model is realized.<br />
So, the question is: what is the real eect of the sensor on the PCB dynamic response <br />
To try to answer to this question, a sensitivity analysis will be performed by integrating<br />
sensors of several mass in our model. Then, the shape of the fourth mode of the OBC 2<br />
card will be studied for 3 cases: a sensor of 0.2 g (as the sensor used in our case), one of<br />
1 g and the last of 2 g.<br />
To realize this, a concentrate mass is added to the model. However, this mass has to<br />
be placed at a strategic point to obtain results which highlight its inuence on the mode<br />
shape. Indeed, if this mass was placed on a vibration node, nothing could be observed<br />
because it would not be excited. So, to realize this choice, the initial shape of the fourth<br />
mode is necessary. This one is given in Figure 4.22.<br />
Figure 4.22: Initial shape of the OBC 2 card's fourth mode<br />
97
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