Views: 3 Author: Site Editor Publish Time: 2020-02-17 Origin: Site
In addition to the hysteresis property, another property that affects the positioning accuracy of piezoelectric ceramic is creep property. When the voltage is applied to the piezoelectric ceramic sheet, the piezoceramic wafer ceramic will immediately expand and generate corresponding displacement. After a long period of time, the length of the piezoelectric ceramic will continue to generate slight elongation deformation. We call it the subsequent slight length deformation creep. The creep variable can be calculated by the following formula. The creep coefficient of piezoelectric ceramics is about 1% - 2%.
Creep variable depends on total displacement, creep coefficient, external load, time, etc. Creep is also understood to depend on the logarithm of time. Creep under static or quasi-static operation is tested by experiments to obtain creep curve,it is creep characteristics of PST 150 / 5x5 / 60
In this experiment, the creep coefficient depends on the PZT piezoelectric material, structure and environmental conditions (such as. G. loading force). 10 s creep is 1.2 μ m and 100 s creep is 1.8 μ M. Creep actually stops a few seconds after the displacement (voltage) stops.
When the periodic signal is used to drive the piezoelectric ceramics, the creep characteristics will not destroy the repetitive positioning accuracy of the peak value and peak value of the Pzt ceramics components, because the creep characteristics have a strong time certainty, and the creep variables are almost the same in each sinusoidal cycle. The full amplitude displacement of the sinusoidal signal is 20 μ m, and the repetitive positioning accuracy of the peak value and peak value is better than 20 mm, it is about 1% of the full amplitude.
We can draw a conclusion that even if the closed-loop is not used in the dynamic operation, the peak to peak displacement of piezoelectric ceramics can reach a very high repetitive positioning accuracy, which only depends on the performance of piezoelectric controller. We recommend the core modular controller of E00 / E01 series with resolution tomorrow.
If it works under static or quasi-static conditions, the creep characteristics will have a certain impact on the positioning accuracy. At this time, we can use the closed-loop piezoelectric ceramics and controllers, and the piezoelectric ceramic crystal with built-in high-precision sensor, which can detect the position signal in real time and feed it back to the piezoelectric controller. The piezoelectric controller adjusts the voltage in real time through PID algorithm to correct the displacement, so as to achieve .The full amplitude is 0.05% of the repeated positioning accuracy.
