Real-time volume haptic rendering with S-chain model

Abstract

This dissertation presents a new model which can simulate the haptic behavior of deformable volumetric objects in real-time and suggests various real-time haptic rendering method. We call this model shape-retaining chain-linked model or S-chain model. Most biomedical objects are deformable and highly non-homogeneous. For realistic haptic rendering of these objects, it is necessary to consider a high-resolution volumetric model consisting of hundreds of thousands of volume elements whose material properties can be different from those of others. Main difficulty in the haptic rendering of these high-resolution volumetric objects is to compute and generate stable feedback force from the objects that have hundreds of thousands of volume elements within a haptic update time (1msec). In our model, springs are used in order to represent material properties of volume elements like a mass-spring model. One of the key differences between the S-chain model and a mass-spring model is that our model is not formulated through employing a dynamically coupled force-deformation relationship. Our deformed configuration is computed by propagating outward the unabsorbed human operator’s input from the interaction point as if a chain is pulled or pushed. The deformed configuration is then used to compute the object’s internal potential energy that is reflected to the human operator. This simple nature of our model allows the much faster calculation of the deformation and the feedback force from the volumetric deformable object than the conventional model (an FEM or a mass-spring model). In most haptic rendering technique, the interaction between human operator and virtual object occurs at a single point at a time. Since the interaction occurs at a single node, the simulation of the interaction is relatively straightforward. However, in reality, the very interface of the contact where one touches is often not a point but a portion of an area. Moreover, it is very common to have more...