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Technical Report on Vibration-Damping Materials and Their Performance Measurement 14

31. Supplementary Materials

3. Response and Linearity of the Excitation Force of the Electromagnetic Vibrator

The measurement block diagram is shown in Figure 8.

  • Figure 8

First, cancel the added mass with a vibrator and configure the mechanical system as shown in the diagram. Use the same electromagnetic detector. Measure the output of the impedance head and the current flowing through the electromagnetic detector. Since the gaps of the MP-910 and MP-912 are different, the generated 'force' is also different. Therefore, normalize the horizontal axis by the maximum value of the applied voltage. It is normalized by the maximum output of the impedance head.

frequency characteristics

The force response of the two types of actuators is shown in Figure 9, the current response in Figure 10, and the frequency response function of current/force in Figure 11.

The MP-910 with a DC resistance of 1 kΩ is affected by its own impedance, exhibiting a dip in force response at approximately 8 kHz. Consequently, the frequency response function of current/force has a peak at this frequency. In contrast, the MP-912 with a DC resistance of 100 Ω has a relatively straightforward characteristic in the 10 kHz range. This indicates that, compared to the voltage response corresponding to the input voltage of the electromagnetic actuator, the current response voltage of the electromagnetic actuator achieves better symmetry around the resonance frequency. (Figure 12)

Regarding the vibration force, it cannot be read from the diagram as it is normalized, but the vibration force is approximately 0.05N/W (at 1mm gap, 1kHz). To obtain a practical force of 0.5N, about 100V is required for the MP-910 and about 38V for the MP-912.

  • Figure 9
  • Figure 10
  • Figure 11
  • Figure 12

Linear Amplification of Vibration

The voltage applied to the electromagnetic vibrator was gradually changed, and the excitation linearity was measured. Its characteristics are shown in Figures 13 to 16. It can be seen that there is considerable linearity.

  • Figure 13
  • Figure 14
  • Figure 15
  • Figure 16

4. Conclusion

  • The characteristics of electromagnetic detectors and vibrators have not been extensively measured in the past. While the cantilever beam method is frequently used, there was a question about whether the input to the electromagnetic vibrator truly measures force. As a result of this measurement, it was found that measuring the input current to the electromagnetic vibrator is closer to measuring 'force' than measuring voltage.

  • It was found that the accuracy of speed detection and speed generation is higher than expected.

  • We have measured two types of electromagnetic detectors and vibrators manufactured by our company, and we plan to measure those from other companies in the future.

  • As for the electromagnetic vibrator, it seems that winding many coils could yield a large excitation force, but this actually increases impedance, which is counterproductive. It has been found that using a thick wire and winding it a moderate amount (about 1000 times) to achieve a direct current resistance of several tens of ohms is sufficient.