Experienced Designers Research Articles

Accuracy and strength of a joint loaded by suddenly applied torque

The influence of the required quality (fit and degree of accuracy) of prismatic joints to achieve guaranteed clearance was a speciality of experienced designers. The problem becomes quite complicated owing to stresses arising in the joint elements during torque transmission under dynamic loading.

Integral attachment using snap‐fit features: a key to assembly automation. Part 2 ‐ bringing order to integral attachment: attachment‐level design

This second of a six‐part series presents a hierarchical scheme for classifying integral snap‐fits at the attachment level, bringing great order to where there appeared to be chaos. The scheme is then used to enumerate all possible design options. The proliferation of plastic parts, and the ability to mould such parts of great complexity at little cost penalty, has resulted in the growing use of integral attachment in the form of snap‐fit features in designs. Heretofore, the great diversity of part geometry and integral snap‐fit features has made it appear that design possibilities may be unbounded, and that attempts at optimization might be intractable. The result shows that options can quickly be reduced to a small enough number to allow designers to compare every possibility, thereby making true optimization a practical reality. As such, the scheme guides new designers and validates choices for experienced designers in ways never before possible.

An empirical study of coupling and control flow metrics

This paper describes the development of a methodology and associated measures for assessing control flow and both the implicit and explicit coupling of hierarchical and network models of system designs. The methodology concentrates on the assessment of the intra-module attribute of embeddedness of control flow structures and the inter-module attribute of implicit complexity of module coupling. The associated measures were developed and validated in collaboration with two commercial organizations whose interests were in reducing development time and corrective maintenance activity; data from these projects are presented here. The application of the measures has been supported by the development of a meta-CASE tool. The measures have shown considerable success in identifying areas of system designs requiring redefinition. However, subjective evaluation by experienced system designers has also provided some promising results, suggesting that qualitative analysis still has a role to play in the ‘quality’ debate.

MENTAL IMAGERY AS A DESIGN TOOL

The role of visualization and mental imaging during the early creative phase in design problem solving is neither fully understood nor recognized. The experiment reported in this paper explores the role of imaging by using an experienced industrial designer and blindfolding him during the act of design. The results obtained clearly indicate that the subject was able to use his mental imagery to assist in his thinking process almost like other depictive displays such as sketching. The findings offer some clues to the designer's internal mental world. The designer created a virtual model in his ''mind's eye,'' manipulated and altered it, assisted all along by his hand gestures. The way he was able to willfully bend the contents of the mental images and make them behave according to his wishes during the development of his ideas appears more impressive and richer than what has been documented so far in the research literature on imagery.

A Topological-Based Dc Analysis Program For Analog Integrated Circuits

This paper presents a new and unique DC analysis program for analog integrated circuits. The simulation program uses no iterative techniques and solves the DC operating point of a circuit by using a topological approach to drive the analysis. A library of node types found in analog circuits allows the simulation program to model groups of devices rather than single devices. The program mimics the actions of an experienced designer when analyzing a circuit by hand. Benchmark results of DCAANT are presented that show DCAANT can generate approximate values very fast.

An approach to functional synthesis of mechanical design Concepts: Theory, applications, and emerging research issues

AbstractConceptual design is an early stage in the design process that involves the generation of solution concepts to satisfy the functional requirements of a design problem. Usually, there are many solutions to a design problem; therefore, there is scope for producing improved designs if one could explore a solution space larger than is presently possible. An approach would be to use the computer to synthesize a wide variety of concepts for a given problem, and allow designers to explore these before developing the most promising ones. Adopting a research approach based on developing basic representations, knowledge base, and reasoning procedures adequate for synthesizing concepts of existing devices and mechanisms, a computer program for synthesis of solutions to a class of mechanical design problems has been developed. For a given design problem, the program can produce an exhaustive set of solution concepts, in terms of their topological and spatial configurations, which can then be explored by designers. The program has been tested in two ways: (1) by comparing the candidate solutions produced by the program with those produced by designers in two real design case studies, and (2) by using three experienced designers to evaluate the solutions, generated by the program, for their novelty and usefulness. This paper presents the theoretical basis, research method, the theory and implementation of the synthesis approach. Also, the results of the above case studies and evaluations, and a discussion of further issues highlighted by the evaluations are presented.

The robustness of feedback systems with bounded complexity controllers

H/sub /spl infin// methods for the analysis and design of robust feedback control systems have sometimes been criticized for an apparent conservatism. However, recent results have shown that they can provide the least conservative results possible under a particular set of assumptions. For example, a ball in the v-gap metric is the largest set of plants that can be guaranteed to be stabilized a priori by a controller known only to satisfy a bound on the induced norm of a particular closed-loop operator. Nevertheless, there are examples of uncertainty which, whilst large when measured by the v-gap metric, would be regarded as relatively benign by an experienced designer of control systems. The present paper examines the possibility that in arriving at this judgment, such a designer is implicitly using the knowledge that he will always choose the least complex controller necessary to do the job. It is shown that, given an appropriate bound on the complexity of the controller, significantly stronger a priori robustness results can be obtained.

Supporting evaluation in design

Design problem-solving requires designers to be creative and to express evaluative judgments. Designers propose successive partial solutions and evaluate these solutions with respect to various criteria and constraints. Evaluation plays a major role in design because each successive evaluation step guides the course of design activity. However, evaluation of design solutions is difficult for both experienced and inexperienced designers because: (1) in complex domains, no single person can know all the relevant criteria and constraints, and (2) design solutions must be evaluated from multiple, and sometimes conflicting, perspectives. Domain-oriented design environments have been proposed as computational tools supporting designers to construct and evaluate design solutions. Critiquing systems embedded in these environments support evaluation activities by analysing design solutions for compliance with criteria and constraints encoded in the systems' knowledge-base. To investigate the impact of such systems, we have designed, built, and evaluated a domain-oriented design environment for a specific area: phone-based interface design. Professional designers were observed using the design environment to solve a complex design task. Analyses of these design sessions enabled us to identify reactions common to all designers, as well as reactions depending on the designers' level of domain experience.

The priorities established among data sources when instructional designers revise written materials

The objective of the study was to investigate the priorities instructional designers establish among data sources when they revise written materials and the relationship of their practice to standard models of formative evaluation. Two modules of printed instructional material were revised by each of eight experienced instructional designers under three treatment conditions, using a counterbalanced design. Data were collected using a think-aloud procedure. The think-aloud protocol was segmented, coded and analysed. Results show that instructional designers were significantly more likely to incorporate their own knowledge into revisions than to use feedback data, and when they did use feedback data, they preferred learner comments. They did not accurately assess their use of their own knowledge or of feedback data; they thought they used feedback data more than the results showed. These instructional designers reflected some aspects of the standard instructional design model when they revised instructional materials, but their experience has caused many of the procedures to become internalized, so they are invisible in the protocols. This research was funded in part by a grant from the Social Sciences and Humanities Research Council of Canada.

Design of Flexible Pavements and Overlay Using an Expert System

EXSPAV is an expert system program established for use in flexible pavement and overlay design. It helps transfer and facilitate the knowledge of experts and results of research and practice to the hands of the less experienced design engineer. It incorporates a versatile design approach, which also facilitates the prediction of the structural performance of pavements. EXSPAV was developed in the EXSYS environment and assimilates Ohio State University's predictive program of flexible pavement structural performance. It also has an overlay design module. EGYPAV is a knowledge-based pavement design program developed in the structure of EXSPAV. Its knowledge base was compiled through consultation with experts from the Roads and Bridges Authority, local universities, and construction companies. The base reflects experience, data, and research results for traffic, environmental conditions, pavements, and material characterization in Egypt. It also includes suggested designs of pavement structure for various combinations of design parameters. The program user may check the suggested design and find its structural performance through the inference engine–deterministic model interaction of the EGYPAV itself.

Design of Flexible Pavements and Overlay Using an Expert System

EXSPAV is an expert system program established for use in flexible pavement and overlay design. It helps transfer and facilitate the knowledge of experts and results of research and practice to the hands of the less experienced design engineer. It incorporates a versatile design approach, which also facilitates the prediction of the structural performance of pavements. EXSPAV was developed in the EXSYS environment and assimilates Ohio State University's predictive program of flexible pavement structural performance. It also has an overlay design module. EGYPAV is a knowledge-based pavement design program developed in the structure of EXSPAV. Its knowledge base was compiled through consultation with experts from the Roads and Bridges Authority, local universities, and construction companies. The base reflects experience, data, and research results for traffic, environmental conditions, pavements, and material characterization in Egypt. It also includes suggested designs of pavement structure for various combinations of design parameters. The program user may check the suggested design and find its structural performance through the inference engine-deterministic model interaction of the EGYPAV itself.

HYPEREX—A generic expert system to assist architects in the design of routine building types

A research project involving the development of a knowledge-based expert system for building design is currently being undertaken by the author in the Department of Architecture, University of Western Australia. The project's objective is to explore the use of portable, easy-to-use knowledge-based expert systems that use the knowledge of experienced architects to assist lessexperienced architects formulate well-resolved building design concepts. The system, called HYPEREX (HYPEREXpert) differs from other building-related expert systems in two significant ways. First, it deals with the design of buildings as entireties rather than small, non-integrated parts of buildings. Second, it is developed from one of the simplest and most practical computer environments presently available, namely HyperCard. The paper introduces the overall objectives and scope of the research. A generic framework for an expert system to aid in the establishment of overall building design is proposed. A means for implementing the generic framework using Hypercard, in the form of the HYPEREX system, is presented followed by an example of the application of HYPEREX to the design of primary schools.

An intelligent system for design optimization of electromagnetic devices

An intelligent system for the design optimization of electromagnetic devices is presented. The system comprises a back-propagation neural network in conjunction with an optimizing Hopfield Net for performing search and optimization functions. An adaptive algorithm is used to improve the response of the system in a dynamic environment. Data can be input by an experienced designer in addition to a case generator from the finite element (FE) solutions. Optimal designs are obtained quickly once the artificial neural network (ANN) is trained with a variety of topologies. Results of implemented examples are provided to show the effectiveness of the proposed system. >

CAHL — computer aided hybrid layout software

Abstract Thick film hybrid is the oldest microelectronic technology, yet it has been the last to move into using computer aided/ automated design methods. CAHL, or Computer Aided Hybrid Layout, is a simple yet powerful software package that allows experienced professional design engineers and students alike to create thick film hybrid circuits quickly. The software can handle conventional and complementary processes. Features include automatic resistor sizing, cross-over and via formation; parameter extraction; generation of SPICE simulation files; net lists, pick-and-place machine position information and component trim information files to assist with manufacture and testing.

Early Retirement for Weaponeers?

Department of Energy`s Lawrence Livermore Laboratory`s once-vital nuclear weapons division is now in dire straits. The laboratory was established in 1952, during the titanic struggle over the hydrogen bomb, has grown steadily from $7 million to its peak of $1.1 billion in 1991. The future for key members of their most experienced weapons design team is uncertain. Over the past two years, Livermore`s operating budget has fallen by 12.5 percent or $127.6 million. Nearly 750 employees, 10 percent of the work force, accepted early retirement offers last year. Further budget cuts will force another 300 to 600 personnel out by the end of 1995. The future resides in the U.S. Congress.

A New Method to Design Blockers

Summary This paper investigates a new method to design blocker geometry in rib-web type closed die forging. By examining various forging and blocker geometries, it was found that blocker geometry can be generated by eliminating high frequency mode from finisher geometry. In order to formalize the procedure, low pass filters, which can convert finisher to blocker geometry, are proposed. Also discrete Fourier transform is used for computational efficiency. The blocker geometry designed by the present method are compared with the one by an experienced designer. The blocker geometries are also validated by using FEM simulation. Present results shows that the frequency approach may offer a promising method to design blocker automatically.

Numerical optimization techniques for structural-acoustic design of rectangular panels

Numerical methods are commonly used to calculate the noise radiation from vibrating structures in order to evaluate the acoustic performance of a particular design. Improvements are then often achieved through trial and error by an experienced designer. While automated numerical optimization techniques are extensively utilized in many fields of structural design, their application to acoustic problems has been limited. In this paper, methods for the design optimization of 'quiet' structures using mathematical programming techniques are investigated. The objective of this fundamental study is to develop effective, general methods for sizing optimization of acoustically radiating structures. The specific design example addressed here is the optimal thickness distribution of isotropic, lightly damped, rectangular, flat plates with clamped edges. Acoustic response to applied point forces is minimized either at a single frequency, or over a wide frequency bandwidth. Radiated sound power is calculated using a discretized Rayleigh integral formulation, in conjunction with a finite element solver (SAPIV) for the solution of the structural problem. The CONMIN optimization program is used. It is shown that the selection of appropriate objective functions and constraints is critical to the success of the optimization process for this multi-disciplinary, computational expensive problem. Potential candidates for objective functions and/or constraints include: total weight, placement of structural natural frequencies, mode shape, mean square velocity, radiation efficiency or total radiated sound power. Several alternative formulations are presented and their effectiveness is compared. It is demonstrated that significant reductions in radiated sound power can be achieved by optimal thickness variation.

Seismic Behavior of Moment‐Resisting Steel Frames: Analytical Study

An analytical investigation into the seismic performance of steel moment‐resisting frames is presented. The International Conference of Building Officials (ICBO) provisions regarding seismic design of steel moment frames are summarized, and potential problems and discrepancies are noted. The results of prior research are reviewed, and prototype three‐, eight‐, and 20‐story frames are designed by an experienced designer. The inelastic responses of these frames are then determined for a range of different earthquake acceleration conditions. The analysis shows that strong‐column weak‐beam (SCWB) frames result in much smaller story drifts and better distribution of inelastic deformation and energy dissipation among elements in the structure than comparable weak‐column strong‐beam (WCSB) frames. The difference was most significant with earthquake acceleration records that cause significant yielding. Steel frames performed adequately if a spine of SCWB joints is used over the height of the structure. The computed results were compared to the results of past experiments. The comparison suggests the SCWB frames should be capable of sustaining the required deformations. The comparison did not provide a clear answer for WCSB frames, and so a series of experiments were performed. These experiments are described in the companion paper.

ARIADNE: A constraint-based approach to computer-aided synthesis and modeling of Analog integrated circuits

The ARIADNE approach to computer-aided synthesis and modeling of analog circuits is presented. It is a mathematical approach based on the use of equations. Equations are regarded as constraints on a circuit’s design space and analog circuit design is modeled as a constraint satisfaction problem. To generate and efficiently satisfy constraints, advanced computational techniques such as constraint propagation, interval propagation, symbolic simulation, and qualitative simulation are applied. These techniques cover design problems such as topology construction, modeling, nominal analysis, tolerance analysis, sizing and optimization of analog circuits. The advantage of this approach is the clear separation of design knowledge from design procedures. Design knowledge is modeled in declarative equation-based models (DEBMs). Design procedures are implemented into general applicable CAD tools. The ARIADNE approach closely matches the reasoning style applied by experienced designers. The integration of synthesis and modeling into one frame and the clear separation of design knowledge from design procedures eases the process of extending the synthesis system with new circuit topologies, turning it into an open design system. This system can be used by both inexperienced and experienced designers in either interactive or automated mode.

A prototype expert system for fishway design

The design of structures for fish passage in rivers and streams provides an opportunity to apply expert system concepts to a design problem. Fishways contribute to the sustainable development of water resources projects by providing a path that allows fish migrations to be maintained. A prototype expert system (FDES) has been developed to recommend the most suitable fishway type for given design conditions. A recommendation is provided on the basis of fishway hydraulics, fish passage performance, and cost requirements. Fishway design demands expertise in various scientific disciplines such as hydrology, hydraulics, and fish biology. Expert system technology may be used to reduce design time requirements and to serve as a teaching aid to inexperienced engineers by organizing and accessing the cumulative knowledge of the most experienced designers. The rule-based expert system development tool, VP-Expert, supplies the backward chaining control structure for accessing the knowledge within the prototype.