High-speed atomic force microscopy (AFM) has been rapidly developed in recent years. To reduce the oscillation of the scanner, a single-tone sinusoidal wave is widely used as a scanning wave rather than a triangular wave in high-speed AFM. However, the sinusoidal wave is nonlinear, resulting in a nonconstant relative linear velocity between the sample and the tip while scanning in the x-direction. If a traditional proportional-integral controller is still used as a feedback controller in the z-direction, the control errors will be enormous. Therefore, the paper proposes a new adaptive velocitydependent proportional-integral controller. The relationship between the proportional-integral parameters and the linear velocity is achieved by fitting the experimental results. The adaptive and traditional controllers are compared against each other in some examples. The experiments demonstrate that the adaptive controller decreases the control errors in the z-direction to a half, which provides more precise AFM images.
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