Research On Force Feedback Model For Oral Virtual Surgery

With the rapid development of virtual reality technology,virtual surgery,as a typical application of virtual reality technology in the medical field,has developed from traditional visual interaction to tactile interaction.Therefore,the research of the force feedback model has become the key technology of virtual surgery.A good force feedback model and force feedback algorithm can bring a stronger sense of immersion to virtual surgery.Based on the application of virtual reality technology in oral medical education and training,this thesis studies the two stages of force feedback,namely the geometric modeling stage and the force feedback modeling stage.Based on the current force feedback model,an improvement scheme is proposed.The problem of discontinuous and unstable feedback force output is solved,and a haptic perception experiment of needle and tooth interaction is designed to verify the improved model and optimization algorithm.The extended experiment of the improved model is carried out.The main research content of this thesis includes the following aspects:1)Establishment of the geometric model.Firstly,the grid model and the voxel model were described in detail,and then the obtained point cloud model was realized by using the Delaunay triangulation algorithm,and then based on the grid model,the cube voxelization algorithm based on octree is adopted to realize the voxelization of the grid model,so as to obtain a high-resolution tooth geometric model.Facilitate the subsequent establishment of the force feedback model.2)Establishment of force feedback model.Firstly,the advantages and disadvantages of common force feedback models are detailed,and the Virtual-proxy model is selected as the preferred one to build the force feedback model.However,the tooth surface is not absolutely smooth,and the Virtual-proxy model cannot simulate the friction force well.An improved Virtual-proxy model is proposed in this thesis,which introduced the friction model into the Virtual-proxy model and increased the friction on the model surface.By designing the haptic perception experiment,force mutation is solved through the improved Virtual-proxy model.The continuity and stability of feedback force and the reality of virtual operation are improved.3)Calculation of feedback force.The traditional force feedback algorithm only calculates the ordinary feedback force without introducing the coulomb friction force into the calculation.In this thesis,the force feedback algorithm was optimized based on the improved Virtual-proxy model,and the friction force was added to the feedback force calculation.According to the valid data,the feedback force calculated by the optimized force feedback algorithm was close to the real clinical oral surgery experience,and the accuracy was increased by 2.2%,which meets the requirements of the oral virtual surgery system.This thesis focuses on the research of the force feedback model in the oral virtual surgery system.Firstly,the tooth voxel model is obtained by geometric modeling of the existing tooth point cloud model.Then an improved Virtual-proxy model is proposed,the force feedback model is established on the basis of the voxel model,and the corresponding force feedback optimization algorithm is designed.Finally,the feasibility and high accuracy of the model are verified by experiments.