Cover Story: Li C, Zhu L L, Yang X D, et al. Research on the measurement method of artificial knee joint based on normal vector tracking[J]. Opto-Electron Eng, 2021, 48(7): 210059

Artificial knee joint plays an important role in improving the joint condition of patients. The manufacturing deviation of the artificial knee joint will directly affect the treatment effect of the patients, so it is necessary to measure and evaluate the artificial knee joint surface with high precision in the actual medical production to guide the processing to improve the manufacturing quality. However, the geometric size of the artificial knee joint is large and the facial shape is complex， and there are great differences in knee joint shape of different patients. Prof. Zhang Xiaodong of Tianjin University designed and built a multi-degree-of-freedom rotary scanning measurement system based on inductive linear displacement sensor (LVDT).  This method performs curve fitting on the measured points, predicts the changing trend of the measured surface and adaptively adjusts the sampling position and posture of the LVDT to make it measure approximately along the normal direction of the sampling point, so as to realize the adaptive rotation measurement of the complex and unknown surface with large slope to achieve high-precision measurement and evaluation of the artificial knee joint surface shape.