Research Of Soft Tissue Deformation Supporting Force Feedback

The purposes of Virtual Surgery are to provide a realistic environment and well function of interactivity. In recent years, the technology of force feedback has being used in virtual surgery simulation system to improve the reality and interactivity. Yet, the force feedback device needs to be updating 1000Hz, so it requires the speed of the algorithm should be very fast, even to get more fast speed at the cost of precision. This paper has deeply studied different types of force feedback models. The model which is obtained from human body slice is a human liver physical model.At first, we add force feedback module to the linear elasticity finite elements model, and make equivalent between collision detection and the intersection of line segment which is defined by the new and old position of the scalpel and surface triangles. Then we calculate the linear feedback force bases on three different types of intersection. Through analysis of biomechanics property of soft tissue, we apply the non-linear characteristic to soft tissue force feedback model. Add non-linear factor to the force feedback model that is based on the premise that the direction of original linear feedback force keeps invariable, and we create the non-linear force feedback model, so the feed-back force can be more realistic.This paper studies other calculate model that it think of the front of scalpel as an implicit sphere and this sphere interacts with the surface triangles. We use the volume of the intersection to calculate the feedback force. At first, we make equivalent between collision detection and the intersection of sphere and surface triangles. Then we project the intersection to the triangle plane;calculate the area of intersection and depth of intersection. So we can obtain the volume. At last, according to the equivalent between force and volume, we can calculate the feedback force.For the first method is validated in the static linear elasticity finite elements model, the result indicates shows well non-linear property and adjustive property.The second method is validated in a dynamic model, also we obtain well feedback force. And the feedback force has non-linear property from the calculate method.