Different Sizes of Piezoelectric Ceramics used for ultrasonic motors(二)

The application of piezoelectric ceramics of different shapes includes TRUM-45II, TRUM. The TRUM-45 II piezoelectric disk element has an outer diameter of 45 mm and an inner diameter of 30 mm, when is using PZT piezoelectric ceramics, its A, B two phases have 7 areas; TRUM 80 I is 80 mm diameter diameter 79 mm, using P-41 piezoelectric ceramics, its A, B two phases of each area. The two-phase admittance characteristic of the motor is measured by an impedance analyzer. The two-phase admittance characteristic curve of the piezo disk vibration sensor of the motor under no-load conditions, small preload, and large preload is shown in Figure 4.8, 4-9 and direct measurement parameters are tables 3.4, 4.5, and 4.7, from which the stator equivalent circuit parameters can be obtained respectively.

As the pre-pressure increases, the admittance circle of piezoelectric element sensor gradually decreases, the G and B values decrease, and the resonance frequency and anti-resonance frequency gradually increase. It can be seen from the test results of the parameters that the enthalpy gradually decreases, which corresponds to the gradual decrease in the diameter of the admittance circle; the free capacitance is basically unchanged, which is the material intrinsic. The reflection of performance does not change with changes in external conditions; the value of resonance frequency and anti-resonance frequency gradually increase, and are consistent with admittance diagrams.

From the results of parameter identification, it can be seen that the internal resistance of the piezo ceramic cylinder becomes large, the static capacitance Cd basically remains unchanged,the mechanical quality factor becomes smaller, and the enthalpy increases continuously. This is mainly due to the fact that the pre-pressure change will increase the contact interface between the stator and the rotor, and increase the use of energy. When the PZT material piezoceramic rings increases to a certain extent, the contact interface will block the area of the rotor and increase the friction of the stator surface. 

A part of the energy is dissipated, so that the admittance becomes smaller and the internal resistance becomes larger, so that the surface temperature of the motor rises. If the 22khz piezoceramic rings is too large, the frequency of the vibration will become high, and long-term work will cause the friction material to wear at the same time, the piezoelectric ceramic will be easily cracked and the output performance of the motor will be reduced. It is important to further explain the choice of suitable pre-stress. At the same time, the maximum conductance GR of A and B phases can be found. It is resonance frequency mound, parallel resonance plant and half power point five, Q is not much difference for two high symmetry.