Donald R. Riley

CAD/CAM for dental restorations-some of the curious challenges

The current state of the art for production of dental restorations is reviewed, and DentiCAD, a system being developed by Maryland University and Minnesota University which is capable of producing dental crowns, is described. DentiCAD can produce dental restorations that fit at least as well as those that are cast. Some of the challenges and difficulties that have arisen during development are addressed. Some of the questions that, because of the new technology, can now be addressed and that are presenting new challenges are discussed.<<ETX>>

A systematic procedure for type synthesis of mechanisms with literature review literaturbe-sprechung

Abstract Type synthesis is the process of determining possible mechanism structures to perform a given task or combination of tasks without regard to the dimensions of the components. The “structure” or “topology” of a mechanism is defined by the number of links, the number of joints and their type (revolute, prismatic, etc.), the connectivity of the links and joints, and which links are to be considered ground and input(s). A systematic procedure for type synthesis, suitable for computer implementation, is introduced. The large body of literature pertaining to type synthesis is discussed in the context of the proposed procedure.

A case-based approach to planar linkage design

We describe a method to store and retrieve design cases of four-bar linkages. The method abstracts relevant features from the planar curve that characterizes each linkage design, and records these features at several levels of abstraction. This allows use of a fast multi-level retrieval procedure, that successively eliminates inappropriate cases at each level. The retrieval incorporates tolerance measures and allows for incomplete problem specifications. Adaptation methods are then used to transform the cases retrieved to match the new design problem. Results of experimental studies to evaluate the efficacy of our method are presented.

Type selection of robot and gripper kinematic topology using expert systems

Robots are used for many different applications including underwater recovery, welding, inspection, pick-and-place operations, space exploration, and assembly. Each task im parts different functional demands on the robot topology including the gripper. An improper choice of the basic kine matic chain may demand sophisticated control algorithms to undo poor type selection. This paper suggests techniques of type synthesis based on graph theory and expert systems that will aid in proper kine matic topology. This new area of kinematic research has high potential for aiding the robot designer.

A network based expert system for intelligent design of mechanisms

Linkage-type mechanisms have numerous applications in industry especially for automation Unfortunately, they are less popular due to lack of proper design tools. This paper describes our efforts to remove the technological barrier in mechanisms design automation. Although the ideas presented apply to automation of mechanisms design in general, the paper discusses the development of an expert system for a particular sub-set of mechanisms called Dwell mechanisms. Many essential and desirable motion characteristics of mechanisms are so implicit that they are difficult to control by analytical methods. By systematically and extensively studying the entire motion characteristics of hundreds of linkages, a comprehensive classification system and heuristics were developed. This qualitative classification scheme led to a finite set of linkage models that cover the entire design space in the sense that any possible design falls under one or more of the models. Our system, called Dwell-Expert, incorporates this design expertise to select the best linkage model for a given set of design specifications and to compare that model against alternatives. The new design methodology and its implementation in AGNESS (A Generalized Network-based Expert System Shell) are explained. A design example is also presented. Our system can reduce even an experienced designer’s initial-design time from a day or more to a minute or less, assuming specifications have already been formulated. Such results motivate extension of this design methodology to other areas of mechanical design and engineering design in general.

Triad Synthesis for up to Five Design Positions With Application to the Design of Arbitrary Planar Mechanisms

Utilisation des triades pour la synthese des mecanismes plans devant passer par cinq points donnes au plus

Application of beams on elastic foundation and B-spline solution methodologies to parametric analysis of intramedullary implant systems

A simple numerical technique for parametric evaluation of orthopaedic implant systems, to be used as a screening tool before complex structural analysis (e.g. Finite Element Method), is the subject of this paper. A modified Beams on Elastic Foundation model (with non-constant foundation modulus) is solved using this numerical technique based on B-spline differential equation modelling. A model with variation in the modulus of the foundation, as solved with this spline technique, was compared with a model with constant foundation modulus, solvable with closed form techniques. While deflections were smaller, the reaction force was up to ten times greater for the models with constant modulus of foundation, compared with varying modulus. The model presented in this paper is a refinement of previous models using closed form solution techniques for foundations with constant moduli. It is primarily useful for detecting trends in parametric analyses, or to select specific cases for further analysis by more computationally intensive analytic methods.

CAD/CAM for dental restorations-challenges and possibilities

A computer-aided design and manufacturing (CAD/CAM) system under development to produce dental restorations briefly described. The advantages and possibilities created by the automation are discussed. The problems encountered during the development of the system are also addressed. The system is expected to reduce the time needed to produce a restoration, standardize the quality of the product, and allow the use of new materials.<<ETX>>

Integrated CAD of mechanisms

Abstract There are three major components in an integral linkage design package: synthesis, analysis and design/drafting. Through the utilization of existing design software and integration tools, such a system is being developed at the University of Minnesota. This paper presents the prototype system along with a detailed example. The system, not yet all encompassing, ties the three major components together into one useful design tool utilizing LINCAGES for synthesis, DRAM for analysis, and ICEM DESIGN/DRAFTING for the design/drafting component. The example illustrates the use of the package in the design of a six-bar stamper mechanism. The design process is followed through from initial problem definition to the final analysis of the mechanism.

Automated System For Stereometric Analysis Of The Human Face

A system that uses stereophotogrammetry to semi-automatically generate three-dimensional facial soft tissue surfaces is presented. The basis of the system is the stereometric technique of Direct Linear Transformation (DLT) which is utilized to eliminate the elaborate instrumentation of present day systems. Automatic digitizing using a scanning image analyzer will require no hand digitizing, and a lightweight headframe will provide orientation information for use in evaluating facial changes. The system is computer based to provide graphic images of the resulting data to ease understanding and to provide the beginnings of a large data base concerning human facial form.