Design And Implementation Of Force Feedback Technology In Virtual Surgery System

With great limitations of traditional surgical and the rapid development of the computer virtual reality technology, virtual surgery system came into being combined with modern medical technology. Virtual surgery system can not only improve of surgical efficiency greatly, but also take a big effectiveness of learning, training. It can also be used for surgical preoperative planning and rehearsal of the rare surgery. Now more and more advanced force feedback devices were produced and provide a hardware foundation for increased operator in immersive virtual surgery system.In virtual surgery system, human organs can be divided into three kinds, such as rigid object, deformable object and fluid object. In this text we focus on the force feedback algorithm of the rigid object and deformable object. Virtual surgery system needs the real-time feedback. Modeling of human organs is the basis of the study of virtual surgery, throughout the collision detection algorithm. Final the calculation of the force feedback and real-time feedback determine the operator’s feel.In force feedback proses of rigid body, there is smaller area of the surgical instruments involved in the collision detection compared with human organs. So we can use one step to determine whether a collision has occurred, by making a sequence list of the surgical instrument. In the phase of accurate collision detection, we use the vector discriminant method instead of the Brute-force method. In the end we use Virtual-proxy method to method the force.About the deformable body, we use a composite deformation algorithm based on physical meaning, because of the shortage of dynamics simulation in the old traditional flexible body deformation algorithm. First, we chose the GEL dynamics engine, which is a filling sphere model introduced a skeleton technology, to simulate the dynamic characteristic and overall deformation of deformable body, and to get the result of collision detection. As the filled sphere model is short on local deformation simulation and the calculation of force is too simple, we build a spring-mass model in the surface of deformable body,by using the idea of layered force which could only point to the center of the deformable body rather than all the surface of the body. Through layered rendering of virtual force, the operator’s tactile sensations can be enhanced.