The objective of this study was to demonstrate the utility of an established model of human motor behavior for assessing the fidelity of a virtual reality (VR) and haptic-based simulation for fine motor task performance. This study was also to serve as a basis for formulating general performance-based simulator-design guidelines toward balancing perceived realism with simulator limitations, such as latency resulting from graphic and haptic renderings. A low-fidelity surgical simulator was developed as an example VR for study, and user performance was tested in a simplified tissue-cutting task using a virtual scalpel. The observed aspect of the simulation included a discrete-movement task under different system-lag conditions and settings of task difficulty. Results revealed user performance in the VR to conform with Fitts' law of motor behavior and for performance to degrade with increasing task difficulty and system time lag. In general, the findings of this work support predictions on human performance under various simulator-design conditions using an established model of motor-control behavior and formulation of human-performance-based simulator-design principles.

In this paper, we present a mitered offsetting method of a triangular mesh. Though our main target application is machining tool path generation, it can also be applied to shelling/hollowing of solid objects, collision avoidance in robot path planning, and so on. Previous literature on mesh offsetting mostly suggest inserting a portion of a cylinder (or a ball) in order to fill the gap between offset faces adjacent to a sharp edge (or a sharp vertex, respectively). The gap filling elements (cylinders or balls) are approximated by a number of small triangles depending on the offset error tolerance. Those small gap filling triangles not only increase tool path computation time, but also cause harmful effect in the accuracy of the machined result around the sharp edges. In this research, we try to reduce the number of gap filling triangles while meeting the given tolerance by introducing the concept of mitered offset, which is popularly used in 2D profile machining practice. We borrowed and modified the notion of quadric error metric (QEM) from the mesh simplification area. A modified version of QEM is used for robust computation of the offset vertex position which minimizes the sum of squared distance error from the faces around the original mesh vertex. If the error is within tolerance, the offset vertex is accepted. Otherwise, the offset vertex is split repeatedly until the error is acceptable. Vertex split occurs at the sharp features. A rigorous foundation is given to the mitered offset of 3D mesh with sharp features as well as smooth regions. The experimental results indicate that only a small number of triangles are added in offset mesh.

This paper presents a new method for computer-aided molecular design (CAMD) and molecular assembly. A lab-built 5-DOF (degree of freedom) haptic device and the driving computational engine have been developed to provide force-torque feedback to the users for computer-aided molecular design (CAMD). An energy minimization method is proposed for finding collision-free molecular configurations in real-time for molecular docking and assembly. The proposed haptic force-torque feedback provides the users an intuitive tool for understanding the interactions among molecules. The presented techniques can be used in the computer-aided molecular design to provide the scientists or the designers a real-time intuitive guide for manipulating the ligand and understanding of the ligand's behavior towards the binding site of a receptor. Computer implementation and illustrative examples are also presented in this paper.

A new method to realize stable and realistic cutting simulation using an impedance display haptic device and microcomputer is presented in this paper. Material removal or cutting simulation is a critical task in dental preparation surgery simulation. In this paper, a piecewise contact force model is proposed to approximately describe the cutting process. Challenging issues of minimizing the difference between the cutting simulation and haptic contact simulation are analyzed. The proposed contact-based simulation method is developed for a one-dimensional cutting task and can be expanded to three-dimensional cases. Local model-based multirate simulation cutting architecture is proposed and force control of the haptic device is decoupled from the cutting simulation loop, which can both ensure high fidelity of dynamical simulation as well as maintain stability of the haptic device. The cutting operation is realized using spherical and cylindrical shaped tools. An experiment based on the Phantom desktop proves that fidelity in one-dimensional cutting can be realized and stability in three-dimensional cutting can be ensured using the force-filtering method.