A constraint-based methodology for product design with virtual reality

This paper presents a constraint-based methodology for product design with advanced virtual reality technologies. A hierarchically structured and constraint-based data model is developed to support product design from features to parts and further to assemblies in a VR environment. Product design in the VR environment is performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction to establish constraints between objects, and are further realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix and derived from constraints between objects by constraint solving. A procedure-based degrees-of-freedom combination approach is presented for 3D constraint solving. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. An intuitive method is presented for recognizing pairs of mating features between assembly components. Examples are presented to demonstrate the efficacy of the proposed methodology

Virtual reality for assembly methods prototyping: a review

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment (Ritchie et al. in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented

Semi-automated approach to shape optimal design of planar structures

This paper presents a general algorithm, using IDEAS programmability features to integrate different phases of shape optimization process. The present work is mainly concentrated on planar structures, defined by thin or shell finite elements. Interactive programs are generated to convert input data to geometric models, to define mesh areas, to generate finite element mesh and to execute adaptive mesh refinement techniques. The importance of automated mesh generation and refinement is highlighted and various optimization methods are considered. Further, a special attention is given to integration issues of shape optimization capabilities into CAD environment. To demonstrate the developed algorithm, an automotive rear suspension torque arm is selected for finite element analysis and shape optimization. The practical example highlights the important features of IDEAS programs and analysis results are explained by plotting stress contours for different steps during the optimization procedure. As a whole, the stress has been given to m develop a general approach, rather than concentrating on specialized areas of shape optimal design process

Evaluation of automated decisionmaking methodologies and development of an integrated robotic system simulation. Appendix A: ROBSIM user's guide

The purpose of the Robotics Simulation Program is to provide a broad range of computer capabilities to assist in the design, verification, simulation, and study of robotics systems. ROBSIM is program in FORTRAN 77 for use on a VAX 11/750 computer under the VMS operating system. This user's guide describes the capabilities of the ROBSIM programs, including the system definition function, the analysis tools function and the postprocessor function. The options a user may encounter with each of these executables are explained in detail and the different program prompts appearing to the user are included. Some useful suggestions concerning the appropriate answers to be given by the user are provided. An example user interactive run in enclosed for each of the main program services, and some of the capabilities are illustrated

MICADO: Models of Interactive Constraints for the Assembling of 1D Deformable Objects

This paper introduces a set of Lagrangian constraints, allowing most needed interaction and combinations of one-dimensional deformable elements for creating complex structures. The proposed tools can potentially be used with a large set of available 1D-models. All constraints formulation are compatible with linear, displacement-based, integration schemes. The proposed constraints allow for real-time complex structure simulation, and also novel interactions between simulated objects. Various examples are provided, illustrating the benefit of the proposed numerical tools

Evaluation of automated decisionmaking methodologies and development of an integrated robotic system simulation, appendix A

A generic computer simulation for manipulator systems (ROBSIM) was implemented and the specific technologies necessary to increase the role of automation in various missions were developed. The specific items developed were: (1) Capability for definition of a manipulator system consisting of multiple arms, load objects, and an environment; (2) Capability for kinematic analysis, requirements analysis, and response simulation of manipulator motion; (3) Postprocessing options such as graphic replay of simulated motion and manipulator parameter plotting; (4) Investigation and simulation of various control methods including manual force/torque and active compliance control; (5) Evaluation and implementation of three obstacle avoidance methods; (6) Video simulation and edge detection; and (7) Software simulation validation. This appendix is the user's guide and includes examples of program runs and outputs as well as instructions for program use

Rapid near-optimal trajectory generation and guidance law development for single-stage-to-orbit airbreathing vehicles

General problems associated with on-board trajectory optimization, propulsion system cycle selection, and with the synthesis of guidance laws were addressed for an ascent to low-earth-orbit of an air-breathing single-stage-to-orbit vehicle. The NASA Generic Hypersonic Aerodynamic Model Example and the Langley Accelerator aerodynamic sets were acquired and implemented. Work related to the development of purely analytic aerodynamic models was also performed at a low level. A generic model of a multi-mode propulsion system was developed that includes turbojet, ramjet, scramjet, and rocket engine cycles. Provisions were made in the dynamic model for a component of thrust normal to the flight path. Computational results, which characterize the nonlinear sensitivity of scramjet performance to changes in vehicle angle of attack, were obtained and incorporated into the engine model. Additional trajectory constraints were introduced: maximum dynamic pressure; maximum aerodynamic heating rate per unit area; angle of attack and lift limits; and limits on acceleration both along and normal to the flight path. The remainder of the effort focused on required modifications to a previously derived algorithm when the model complexity cited above was added. In particular, analytic switching conditions were derived which, under appropriate assumptions, govern optimal transition from one propulsion mode to another for two cases: the case in which engine cycle operations can overlap, and the case in which engine cycle operations are mutually exclusive. The resulting guidance algorithm was implemented in software and exercised extensively. It was found that the approximations associated with the assumed time scale separation employed in this work are reasonable except over the Mach range from roughly 5 to 8. This phenomenon is due to the very large thrust capability of scramjets in this Mach regime when sized to meet the requirement for ascent to orbit. By accounting for flight path angle and flight path angle rate in construction of the flight path over this Mach range, the resulting algorithm provides the means for rapid near-optimal trajectory generation and propulsion cycle selection over the entire Mach range from take-off to orbit

SUPPORTING FUNCTIONALITY-BASED DESIGN IN COMPUTER-AIDED DESIGN SYSTEMS

Designs are conceptualized in terms of the functions they need to accomplish. The need for a new product design arises as a result of the identification of a new functionality to be accomplished by the product. That is, design is functionality driven. However, existing CAD tools are not equipped to capture functionality or reason in such a fashion to support design for product functionality. This research proposes a new design formalism to enable functionality-driven design of mechanically engineered products. This procedure provides a methodology that allows a designer to model product functionality and to carry out conceptual design with the aid of a computer. It also serves as a bridging tool between the conceptual design phase and detailed design phase of a product. Thus, the primary objective of this research is to develop a methodology that will support the following activities in CAD systems: functionality modeling, functionality data structuring, and form conceptualization.The functionality modeling methodology developed in this work includes the use of operands, operators, and coupling bonds to describe product functionality in CAD systems. The Universal Modeling Language (an object-oriented programming technique) is used to model product functionality in computer systems. The tools developed in this research provide a means of modeling and propagating product functionality information to downstream design activities. The propagation of functionality as a constraint is achieved using Extensible Markup Language (XML) data files. These tools also provide a mechanism for verifying and enforcing constraints on solid CAD models. The functionality definition interface is implemented with a customized Microsoft Visio graphics engine.The tools developed in this research provide a means of modeling and propagating product functionality information to downstream design activities. It also provides a mechanism for verifying and enforcing constraints on solid CAD models. The functionality definition interface is implemented with a customized Microsoft Visio graphics engine