Yuan-Shin Lee

Optimal Tool Orientation for Five-Axis Tool-End Machining by Swept Envelope Approach

This paper presents a swept envelope approach to determining the optimal tool orientation for five-axis tool-end machining. The swept profile of the cutter is determined based on the tool motion. By analyzing the swept profile against the part geometry, four types of machining errors (local gouge, side gauge, rear gouge, and global collision) are identified. The tool orientation is then corrected to avoid such errors. The cutters swept envelope is further constructed by integrating the intermediate swept profiles, and can be applied to NC simulation and verification. This paper analyzes the properties of the swept profile of a general cutter in five-axis tool-end machining. The relation of the swept profile, the part geometry, the tool motion, and the machining errors is developed. Therefore, the error sources can be detected early and prevented during tool path planning. The analytical results indicate that the optimal tool orientation occurs when the curvature of the cutters swept profile matches with the curvature of the local part surface. In addition, the optimal cutting direction generally follows the minimum curvature direction. Computer illustrations and example demonstrations are shown in this paper. The results reveal the developed method can accurately determine the optimal tool orientation and efficiently avoid machining errors for five-axis tool-end machining.

Virtual prototyping and manufacturing planning by using tri-dexel models and haptic force feedback

This paper presents a new method of using the tri-dexel volumetric models and a haptics force feedback for virtual prototyping and manufacturing planning. In the proposed method, the initial polyhedral surface model is converted to a tri-dexel volumetric model by using a depth-peeling dexelization algorithm. In the virtual prototyping process, the tri-dexel volumetric model is updated by the swept volume of a moving cutter via a haptic force feedback interface device. A collision detection algorithm is proposed for the virtual sculpting and the pencil-cut planning with real-time haptic force feedback to the users. Tool paths are generated for machining the virtual sculpted parts via the simulation and verification on a virtual CNC machine tool before they are actually machined. Computer implementation and practical examples are also presented in this paper. The proposed method enables the haptic-aided virtual prototyping and manufacturing planning of complex surface parts.

Interactive Computer-Aided Design for Molecular Docking and Assembly

AbstractThis paper presents a computer-aided design system for molecular docking and nanoscale 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). The developed haptic force-torque feedback will enable researchers to visualize, touch, manipulate and assemble molecules in a virtual environment. The presented techniques can be used in the computer-aided molecular design to provide the researchers a realtime tool to better understand molecular interactions and to evaluate possible pharmaceutical drugs and nanoscale devices. Computer implementation and illustrative examples are also presented in this paper.

Investigating Human Performance in a Virtual Reality Haptic Simulator as Influenced by Fidelity and System Latency

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.

Computer-aided molecular design (CAMD) with force-torque feedback

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 ligands behavior towards the binding site of a receptor. Computer implementation and illustrative examples are also presented in this paper.

Evaluation of an Augmented Virtual Reality and Haptic Control Interface for Psychomotor Training

This study investigated the design of a virtual reality (VR) simulation integrating a haptic control interface for motor skill training. Twenty-four healthy participants were tested and trained in standardized psychomotor control tasks using native and VR forms with their nondominant hands in order to identify VR design features that might serve to accelerate motor learning. The study was also intended to make preliminary observations on the degree of specific motor skill development that can be achieved with a VR-based haptic simulation. Results revealed significant improvements in test performance following training for the VR with augmented haptic features with insignificant findings for the native task and VR with basic haptic features. Although performance during training was consistently better with the native task, a correspondence between the VR training and test task interfaces led to greater improvement in test performance as reported by a difference between baseline and post-test scores. These findings support use of VR-based haptic simulations of standardized psychomotor tests for motor skill training, including visual and haptic enhancements for effective pattern recognition and discrete movement of objects. The results may serve as an applicable guide for design of future haptic VR features.

Snapping algorithm and heterogeneous bio-tissues modeling for medical surgical simulation and product prototyping

This paper presents a novel technique for modeling soft biological tissues as well as the development of an innovative interface for bio-manufacturing and medical applications. Heterogeneous deformable models may be used to represent the actual internal structures of deformable biological objects, which possess multiple components and non-uniform material properties. Both heterogeneous deformable object modeling and accurate haptic rendering can greatly enhance the realism and fidelity of virtual reality environments. In this paper, a tri-ray node snapping algorithm is proposed to generate a volumetric heterogeneous deformable model from a set of object interface surfaces between different materials. A constrained local static integration method is presented for simulating deformation and accurate force-feedback based on the material properties of a heterogeneous structure. Biological soft tissue modeling is used as an example to demonstrate the proposed techniques. By integrating the heterogeneous deformable model into a virtual environment, users can both observe different materials inside a deformable object as well as interact with it by touching the deformable object using a haptic device. The presented techniques can be used for surgical simulation, bio-product design, bio-manufacturing, and medical applications.

Five-Axis High Speed Machining of Sculptured Surfaces by Surface-Based NURBS Path Interpolation

AbstractThis paper presents a new surface-based NURBS path interpolation for 5-axis high speed machining (HSM) of sculptured surfaces. Detailed formulation of the new time-parameter NURBS path interpolation is proposed to convert the NURBS part surface into time-variable parameterized tool paths for 5-axis sculptured surface machining. Based on the machine configurations, the surfacebased NURBS path interpolation directly derives the pivot point location and the spindle orientation to control the machine motion. With the proposed new method, the traditional chordal and linearization deviation errors in 5-axis NC machining can be reduced. Computer implementations and illustrative examples are also presented in this paper. The presented techniques can be used in the CAD/CAM systems and the NC controllers for 5-axis high speed machining of sculptured surfaces.

Energy-Field Optimization and Haptic-Based Molecular Docking and Assembly Search System for Computer-Aided Molecular Design (CAMD)

This paper presents a new system using a haptic device with an automatic molecular docking and assembly search method for the problems of molecular docking and molecular assembly in computer-aided molecular design (CAMD). The developed haptic force-torque feedback provides the users an intuitive tool for understanding the interactions among molecules while an automatic docking and assembly search method, NanoDAS, assists the user on determining the docking and assembly feasibility. The proposed system can be used as a tool to screen out candidate molecules that are infeasible, in terms of geometry and energy, to dock or assemble into a larger molecule. This identification of feasible molecules can significantly improve and accelerate the discovery and design of new pharmaceutical drugs and nanoscale devices in CAMD. Computer implementation and illustrative examples are also presented in this paper.

Swept Tool Envelope and Machining Potential Field for 5-Axis Sculptured Surface Machining

This paper presents the machining potential field (MPF) and the explicit solutions of swept envelopes for 5-axis sculptured surface machining. The properties of the swept envelopes are analyzed. The results help us realize the geometric matching in tool-tip machining and understand the geometric machinability in tool-side machining. The complement of the swept envelope, which represents the in-process workpiece, is also addressed. It finally presents the swept envelope applications in tool orientation determination, machining interference avoidance, and run-time simulation. When a solid object moves, it creates a three-dimensional swept volume. This swept volume defines a space where is ever occupied by the object during its motion. Anything inside this occupied space is collided with the object, while anything outside the space is collision-free. The swept envelope defines the boundary between the collision and collision-free space. Therefore, the swept envelope plays an important role in a wide variety of geometric applications such as geometric construction, robot workspace configuration, and collision detection (1, 2). Swept envelope computation is usually difficult because of the nonlinearity of the problem. It is generally impossible to obtain closed form expressions for the swept envelope created by objects with arbitrary geometric shapes (1, 3). Fortunately the majority of tool geometry for robots and NC machining is axial symmetry and defined by surfaces of revolution. These tools usually can be decomposed into geometric primitives, such as spheres, tori, cylinders, and cones (4). Due to their simplicity, the swept envelopes of the geometric primitives can be easily determined and explicitly presented. The swept envelopes of the original tools can then be integrated by the swept envelopes of their primitives (5). This paper details the determination of the swept envelope of axial symmetric tools, and its applications. It first analyzes tool geometry and its decomposition of geometric primitives. Then it discusses the tool position and the tool motion. Based on the tool geometry and motion, the explicit solution of the swept envelope is derived. It further analyzes the properties of the swept envelope. The results deduce us how to match the tools with the part geometry, and reveals the machinability of the geometry. The construction of the complement of the swept envelope is also discussed. After illustrating examples in computer applications, we conclude in the final section.