Research On Key Techniques Of Force Feedback In Virtual Surgery Simulation Based On Deformable Models

Virtual surgery simulation is a virtual reality system used to simulate all kinds of phenomenon of surgery. For surgical simulation to be a useful training and simulation tool it must be realistic with respect to tissue deformation, tool interactions, visual rendering, force feedback and real-time response.In this thesis, some key technologies of virtual surgery simulation system for nasopharyngeal carcinoma and liver cancer are investigated systematically. Firstly, a Half-Edge data structure is used for geometry modeling for the head and liver. Then,a mass-spring model is used for physical modeling. In virtual surgery simulation system for nasopharyngeal carcinoma, a collision detection method based on Oriented Bounding Box is used because of the requirements of high accuracy in this system. In virtual surgery simulation for liver cancer, a collision detection method based on Axis-Aligned Bounding Boxes is used to satisfy the higher frame rates in haptic feedback and return collision point and the triangle. In virtual deformation simulation for liver cancer, we calculate the deformation based on virtual mass spring model. In virtual cutting simulation for liver cancer, the cutting path is generated and the virtual spring is disconnected in this path. Then four kinds of mesh patterns were reconstructed. Using the force feedback device, a synchronize mechanism was adopt to improve the stability of the force output. This paper proposes a snap force maching-vertex algorithm to deal with the collision point within the scope of threshold. In virtual cutting simulation, a kind of friction is added to make the effect of cutting more authentic.The main contributions of this thesis are mainly lie in the following aspects:1. A twice detection method was proposed to improve the phenomenon of the force puncture in virtual surgery simulation system for nasopharyngeal carcinoma.2. A synchronize mechanism was adopt to improve the stability of the force output in virtual surgery simulation system for nasopharyngeal carcinoma.3. This paper proposes a snap force maching-vertex algorithm to deal with the collision point within the scope of threshold in virtual deformation simulation.4. In virtual cutting simulation, a kind of friction is added. The force feedback is made up of spring and friction, which makes the effect of cutting more authentic.