Optimized adaptive control for evaluation of artificial hip joint volumetric wear by coordinate measuring

Compared with the gravimetric method, geometric method in terms of coordinate measurement (CMM) is endowed with advantage of direct determining wear volume and distribution on the articulating surfaces of artificial hip prostheses. The current volumetric measurement usually requires more measuring points and computational cost to surpass the limitations of bad repeatability and low accuracy. A new method of CMM measurement is proposed for collecting density of data adapted to the surface profile of worn area, controlling and optimizing probe contact angle and reconstructing calculative socket on the same region with better measuring accuracy and relatively lower calculating cost. UHMWPE cups are chosen to validate this approach. The results show that the repeatability error of volume evaluation is reduced by 49.3% with half as much as measurement cost for previous method and the accuracy is improved by 32.4%-46.7%, a correlation (R²=0.9228) exists between the new method and gravimetric method, showing its effectiveness, and the developed method enables to reconstruct the worn surface with detailed distribution.