Adaptive velocity-dependent proportional-integral controller for high-speed atomic force microscopy | JoVE Visualize

Area of Science:

Surface Science
Microscopy Techniques
Control Systems Engineering

Background:

High-speed atomic force microscopy (AFM) increasingly utilizes sinusoidal scanning waves to mitigate issues associated with traditional triangular waveforms.
Sinusoidal scanning, while reducing scanner oscillation, introduces nonlinearities leading to variable relative velocities between the tip and sample.
Existing proportional-integral controllers struggle with these velocity variations, resulting in substantial control errors, particularly at high scanning speeds.

Purpose of the Study:

To develop and validate a novel adaptive velocity-dependent proportional-integral controller for high-speed AFM.
To address the significant control errors caused by nonlinear velocity variations in sinusoidal AFM scanning.
To enhance the precision and quality of AFM images obtained at various scanning speeds.

Main Methods:

Implementation of an adaptive proportional-integral controller where controller parameters are dynamically adjusted based on the instantaneous scanning velocity.
Experimental validation by comparing the performance of the adaptive controller against a traditional proportional-integral controller.
Quantitative analysis of control errors in the z-direction under different scanning conditions.

Main Results:

The proposed adaptive controller significantly reduces control errors in the z-direction by approximately 50% compared to traditional controllers.
Experimental results demonstrate improved AFM image quality due to minimized control errors.
The adaptive controller proves effective in enhancing image precision across both low and high scanning speeds.

Conclusions:

The adaptive velocity-dependent proportional-integral controller is a superior solution for managing nonlinear velocity variations in high-speed AFM.
This advancement leads to more accurate and higher-resolution AFM imaging.
The developed controller offers a practical method for improving the performance of existing and future high-speed AFM systems.