Active disturbance rejection control design for atomic force microscopy in Z-axis

In order to improve the scanning performance of an atomic force microscopy (AFM), advanced position control of the piezoelectric actuator along the z-axis should be carefully designed to enhance the control precision, speed and robustness. In this paper, active disturbance rejection controller (ADRC) is applied to replace the traditional Proportional-Integral-Derivative (PID) controller to improve the control performance of an AFM along its z-axis. Specifically, firstly we set up the transient profile generator to obtain the error signal more reasonably. Then, the tracking differentiator is designed to replace the traditional differentiator to reduce the noise amplification of output signals and realize fast tracking of input signals. Afterwards, we design an extended state observer to implement the state estimation. In this way, the entire ADRC is designed for the AFM in z-axis to improve the control speed, precision, as well as the robustness of the AFM system. Simulation results demonstrate the effectiveness of the proposed controller.