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PEA driving system

Estimation of PEA deformation through interferometry

Description

PEA driving system

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Estimation of PEA deformation through interferometry

In order to train a hysteresis/creep model, measurements of the PEA (Piezoelectric Actuator) applied voltage v and corresponding deformation z are necessary.
If the Atomic Force Microscope (AFM) is not equipped with deformation sensor, signal z cannot be masured.
Nevertheless, it can be estimated starting from the measurement of the deflection signal x [1], according to the following procedure:

1. a mirror is placed instead of the AFM sample;
2. the cantilever is moved up and down by applying a triangular signal, ensuring that no contact occurs between the cantilever tip and the mirror;
3. by properly regulating the inclination angle of the mirror, an interference pattern x(t) is obtained;
4. in the time interval between two extrema of x(t), the PEA vertically moves of a quantity Δz=λ/4, being λ the wavelength of the laser beam; this information can be exploited to estimate signal z(t) [1].

The zip file contains three files:

• estim_z.m: MATLAB function which generates signal z(t) starting from the PEA applied voltage v(t) and the interference signal x(t).
• example.m: demo file which employs function estim_z.
• data.mat: contains the measurements of signals v(t) and z(t) necessary to run demo example.m.

See the documentation of function estim_z (type "help estim_z" in the MATLAB command line) for all details.

References

1. Oliveri A., Lodi M., Storace M., Raiteri R., "Application of a low-cost piezoelectric displacement estimation technique based on laser interferometry for hysteresis open-loop compensation in an AFM scanner", Physica B: Condensed Matter, in press.