基于MLS-MWS混合模型的软组织建模  

Soft Tissue Modeling Based on MLS-MWS Mixing Method

作　　者：陈卫东[1,2] 刘波[1] 朱奇光[1,2] 

机构地区：[1]燕山大学信息科学与工程学院,河北秦皇岛066004 [2]河北省特种光纤与光纤传感重点实验室,河北秦皇岛066004

出　　处：《中国生物医学工程学报》2016年第6期699-704,共6页Chinese Journal of Biomedical Engineering

基　　金：国家自然科学基金(61201112);河北省自然科学基金(F2016203245);河北省普通高等学校青年拔尖人才计划(BJ2014056)

摘　　要：针对无网格模型计算量大和边界处理繁琐的问题,提出一种基于改进最小二乘近似函数的无网格强弱势混合模型(MLS-MWS)。首先,基于场理论将模型划分为内部域和外部域,在内部域中,不与自然边界相连接的节点通过无网格强势法来构建平衡方程,该方法无数值积分,从而达到计算量的减少;在外部域中,通过无网格局部弱势法来弱化边界问题。其次,在强势方法中,需利用最小二乘近似式表示位移的二阶导数,针对其计算量大和效率低的问题,提出改进移动最小二乘近似函数和导数,通过将节点值进行两次MLS导数插值,求出该节点的二阶导数,进一步简化计算;最后采用PHANTOM触觉交互设备,对肝脏模型进行拉伸与挤压的形变模拟实验。实验结果表明,MLS-MWS混合模型相比无网格伽辽金模型,单步执行时间从17.3 ms减少到13.8 ms,频率从56.80帧/s提高到72.46帧/s。该混合模型结合无网格强弱势法和双重无网格配点法,达到优势互补,有效提高模型的实时性。Targeting to problem of the large computation amount of mesh-free model and tedious boundary processing, MLS-MWS based on the improved least square approximation was proposed in this work. At first, the model was divided into the internal domain and external domain based on the field theory. In the internal domain, nodes far from the natural boundary constructed the equation of equilibrium with the mesh-free method. The method has no numerical integration, which may reduce the computation amount. In the external domain, the boundary problem was weakened through the mesh-free partial weak method. Secondly in the strong method, second-order derivative of the displacement should be indicated with the least square approximation equation. Targeting tothe large computation amount of mesh-free model and low efficiency, it was proposed to improve the moving least square approximation function and derivate, and MLS derivative interpolation was carried out for the node value, for working out the second-order derivative and further simplifying the computation. Eventually, deformation simulation experiment of stretching and squeezing the liver model was carried out with the PHANTOM touch interactive equipment. According to the results, the single-step execution time of MLS-MWS combined model was reduced to 13.8 ms from the original 17.3 ms of the mesh-free model, while the frequency was improved from 56.80 frames/s to 72.46 frames/s. The mixed model integrated advantages of the mesh-free weak-strong method and dual mesh-free point-allotting method, which improved the instantaneity of the model effectively.

关 键 词：软组织建模 无网格法 双重配点无网格法 MLS-MWS模型 

分 类 号：R31[医药卫生—基础医学]