4. Testing in a laboratory environment

Once evaluated in a laboratory environment, the demonstrator was integrated to engine tests. Packaging of the system was made of silicon sealant. A full-scale demonstrator was evaluated and submitted to qualification testing before ground engine testing. Figure 13 presents the system validation phase:


• A vibrator is used to induce vibration to the piezoelectric beams of the vibration harvesters. Levels applied are random spectrum, according to

Compressive loads were applied to the mechanical link with the system clamped to it. Thermal difference (80/120°C) was applied at each end of the link to establish a thermal gradient close to the application to feed thermal harvesters. A piezoelectric buzzer was used to apply excitation to the vibration harvesters. The regulated voltage from the power module was checked and also the read write memory

The autonomy of the system was reached for a thermal gradient of 10°C for the

The system was submitted to ground testing inside a real engine. During the tests, system failed to be autonomous. Measurement done externally showed that the vibration and energy sources were lower than forecasted for the sizing of the

thermal harvester and a vibration level of 1 g at 100 Hz (Figure 14).

application specification.

Laboratory validation of the sensor system.

system.

17

Figure 13.

Figure 12.

Reading distance with dipole antenna.

Structural Health Monitoring from Sensing to Processing DOI: http://dx.doi.org/10.5772/intechopen.86758

voltage output at the microcontroller level.

• The press plates can be heated allowing to apply application temperature level to the system.

Figure 11. A dipole antenna above a perfect electric conductor (PEC) and its image [6].

Figure 12. Reading distance with dipole antenna.

Even if the UHF-RFID is being used in a large number of economic areas, there is already a large market where this technology did not bring any answer. Metal placed with RFID tags is one of the greatest challenges to the RFID technology, and a lot of researches have been putting large efforts to solve this problem in the last decade. In particular, the classical dipole antennas are not effective when put near

This specific problem is explained in Figure 11, which shows that the image dipole below the metal surface has an opposite current from that of the original dipole. If the space between the dipole and its image is very small (much less than one wavelength), then the total effective current approaches zero. Therefore, the total radiation field is negligible. The RFID is then unable to capture power from the reader. Looking for a solution to this problem, some ideas have been explored in the last

• Increasing the distance between the antenna and the metal surface

Dipole antenna demonstrated weak communication capability for the project application environment. An anti-metal antenna design has been investigated [10–22] to propose an alternative to dipole antenna as shown (Figure 12).

Once evaluated in a laboratory environment, the demonstrator was integrated to

• The thrust link is mounted on a hydraulic press able to generate compressive

• The press plates can be heated allowing to apply application temperature level

engine tests. Packaging of the system was made of silicon sealant. A full-scale demonstrator was evaluated and submitted to qualification testing before ground

engine testing. Figure 13 presents the system validation phase:

• The demonstrator is assembled on a real thrust link.

A dipole antenna above a perfect electric conductor (PEC) and its image [6].

to metallic surfaces.

years and are well explained in [6, 7]:

Advances in Structural Health Monitoring

• Inserting high permeability isolator

• Using frequency-selective surfaces

• Using an anti-metal antenna design

4. Testing in a laboratory environment

force similar to the real application.

to the system.

Figure 11.

16

Figure 13. Laboratory validation of the sensor system.

• A vibrator is used to induce vibration to the piezoelectric beams of the vibration harvesters. Levels applied are random spectrum, according to application specification.

Compressive loads were applied to the mechanical link with the system clamped to it. Thermal difference (80/120°C) was applied at each end of the link to establish a thermal gradient close to the application to feed thermal harvesters. A piezoelectric buzzer was used to apply excitation to the vibration harvesters. The regulated voltage from the power module was checked and also the read write memory voltage output at the microcontroller level.

The autonomy of the system was reached for a thermal gradient of 10°C for the thermal harvester and a vibration level of 1 g at 100 Hz (Figure 14).

The system was submitted to ground testing inside a real engine. During the tests, system failed to be autonomous. Measurement done externally showed that the vibration and energy sources were lower than forecasted for the sizing of the system.

Figure 14. Thermal and vibration harvesters' characteristics.
