Research On Hysteresis Modeling And Real-time Correction Of Scanning Images In Atomic Force Microscope

Atomic force microscope(AFM)has been widely used in the fields of physics,chemistry and biology,such as three-dimensional shape detection,nanomaterial processing,and biological property detection.It has highest sensitivity and highest detection accuracy among the three-dimensional shape detection instruments.However,in three-dimensional scanning process,AFM has inaccurate positioning of the scanning points due to the characteristics of piezoelectric actuators hysteresis,which seriously affects the quality of the scanned image and limits the performance of the AFM.In this thesis,a hysteresis model combining sinusoidal function and linear function is proposed according to the experimental phenomenon,and the model parameter can be resolved from the AFM scanned images.The established hysteresis model can be integrated into the AFM scanning program to realize real-time correction of hysteresis in 3D scanning process.The dissertation mainly introduces the following parts:(1)The hysteresis characteristics of piezoelectric actuators were studied and analyzed.According to the experimental phenomena,a hysteresis model based on sinusoidal function and linear function was established,which can effectively compensate the hysteresis error.(2)According to the working mode of piezoelectric actuators in AFM 3D scanning process,the expression form of hysteresis model in scanned images was derived.The model parameter is calculated from the coordinates of matched feature points in the trace and retrace images of ordinary sample.And it has achieved good results using the solved hysteresis model to directly correct the hysteresis of scanned images.(3)The existing atomic force microscope hardware system was modified,and a hardware PID feedback control circuit was built to effectively improve the scanning speed.(4)Real-time hysteresis correction based on proposed hysteresis model was implemented on the modified atomic force microscope experimental platform,and relevant experimental tests were carried out.Experiments show that the hysteresis of AFM scanned images can be reduced by more than 90% under different scanning frequencies and scanning ranges.Based on this model,real-time correction of hysteresis was easily realized.This model can be integrated into commercial AFM without changing the hardware,which has good application value.