Packing of Generic, Three-Dimensional Components Based on Multi-Resolution Modeling

A method of optimizing layouts of three-dimensional objects of arbitrary geometry with simulated annealing is presented in this paper. Using multi-resolution models, this approach is able to generate optimal layouts of three-dimensional objects in reasonable time. An example of packing highly non-convex objects illustrates the power of this method.

Axiomatic Design Applied to Manufacturing Systems Design

In earlier work, the axiomatic design theory has been analyzed for applications on product design and the production processes that pertain to it, where parts manufacture and assembly take place in flexible and automatic manufacturing systems. The conclusion is that the original model cannot handle the manufacturing aspects in a satisfactory manner. This report proposes an expansion of the axiomatic design model, with a life-cycle approach as take-off. The expansion of the model consists of the introduction of a so-called Manufacturing World with different spaces, where various types of processes and support functions can be developed in agreement with the axiomatic principles. The spaces and their relationships have been defined along with explanations of work procedures. An explanatory example is given.

Experimental Study of a Variable Pressure Damper on Automotive Valve Motion

A variable pressure damper (VPD) is used here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve bouncing phenomenon. The friction force on the valve spring is found experimentally, and the corresponding friction coefficient is also determined. Dynamic valve displacements at different speeds with different friction forces are calibrated. Bouncing and floating of the valve are observed when the camshaft reaches high speed. From the measured valve displacement, the VPD is shown to have significant improvement in reducing valve bouncing distance and eliminating floating. However, experimental results indicate that the valve bouncing can not be eliminated completely when the camshaft speed is at 2985 rpm.

Generalized Abbe Principle: Position Error Propagation in Machine Elements

In the quest for ever finer levels of technology integration, mechanical linkages reach their precision limits at about 5micrometers per meter of workspace. Beyond this physical limit, all six dimensional degrees of freedom need to be precisely ascertained to account for mechanical imperfections. This paper substantiates Wu’s vision of “precision machines without precision machinery.” A formulation and statistical characterization of position and orientation error propagation in rigid bodies are presented for two extreme models of measurement. It is shown that error distribution is uniquely dependent upon the design of the measurement plan. The theoretical foundations presented were evolved in the course of designing precision machinery. Other potential applications include: fixture design, metrology, and geometric tolerance verification.

Optimum Design of a Planar Robotic Manipulator

A general optimization methodology for the optimal design of robotic manipulators is presented and illustrated by its application to a realistic and practical three link re volute-joint planar manipulator. The end-effector carries out a prescribed vertical motion for which the weighted average torque requirement from electrical driving motors is minimized with respect to positional and dimensional design variables. In addition to simple physical bounds placed on the variables the maximum deliverable torques of the driving motors represent further constraints on the system. The optimization is carried out via a penalty function formulation of the constrained problem to which a proven robust unconstrained optimization method is applied. The problem of degeneracy or lock-up, which may occur for certain choices of design variables, is successfully dealt with by means of a specially proposed procedure in which a high artificial objective function value is computed for such “lock-up trajectories”. Designs are obtained that represent substantial reduction in torque requirement in comparison to that of arbitrarily chosen practical designs.

Recent Refinements in the Multi-Point Approximation Method in Conjunction With Adaptive Mesh Refinement

Application of the Multi-point Approximation Method (MAM) to structural optimization is considered. Structural analyses are performed by means of the finite element method with Adaptive Mesh Refinement (AMR). The required discretization errors are changed during the optimization process to achieve a higher computational efficiency. A straightforward combination of the MAM and AMR may yield complications, which are discussed in detail. Therefore, several modifications in the MAM are necessary. An alternative strategy for determining the explicit approximation functions using a weighted least-squares fitting is proposed. The applied weight coefficients reflect the levels of the discretization errors. The approximation functions are fitted with a sub-set of the available structural response analyses. An alternative move limit strategy is given. On the basis of several numerical examples it is shown that the proposed modifications improve the convergence characteristics of the MAM when combined with AMR. Moreover it is demonstrated that the proposed refinements are also beneficial for optimization of systems with noisy objective and constraint functions.

A Development of Wire Path Searching Module Using Extended RCA Method

This study deals with a development of wire path searching module as a part of automotive wire harness design system. Wire path searching module manages the free space, finds transition locations, and creates bundle paths to dramatically reduce a tedious iterative routing process which results in easy optimization of the bundle paths. A prime policy in the system configuration is to compromise between man’s and computer’s ability, and make it possible a designer’s leading role in designing process. Human input is indispensable to cope with the special cases which were not considered in the initial design stage of the system. In this study, we improve the previous shortest-path-finding algorithm (VGraph and RCA method) into a new method called Extended RCA. Bundles, connectors and transitions are handled as objects so one can manage and modify physical properties of the objects easily. Therefore a verification is allowed at any desired stage of design. The reuse of previous result is facilitated by using Dependency Structure, which represents the mutual relations among connectors, transitions, and bundles. Dependency Structure makes it possible the elimination of redundant calculating process, and consequently shorter routing time.

Design of Modular Product Architectures in Discrete Design Spaces Subject to Life Cycle Issues

A product’s architecture affects the ability of a company to customize, assemble, service, and recycle the product. Much of the flexibility to address these issues is locked into the product’s design during the configuration design stage when the architecture is determined. The concepts of modules and modularity are central to the description of an architecture, where a module is a set of components that share some characteristic. Modularity is a measure of the correspondence between the modules of a product from different viewpoints, such as functionality and physical structure. The purpose of this paper is to investigate formal foundations for configuration design. Since product architectures are discrete structures, discrete mathematics, including set theory and combinatorics, is used for the investigation. A Product Module Reasoning System (PMRS) is developed to reason about sets of product architectures, to translate design requirements into constraints on these sets, to compare architecture modules from different viewpoints, and to directly enumerate all feasible modules without generate-and-test or heuristic search approaches. The PMRS is described mathematically and applied to the design of architectures for a hand-held tape recorder. Life cycle requirements are used as design criteria.

Computer-Aided Modelling of Cloth Deformation

A constrained finite element method for modelling cloth deformation is developed. The bending deformation and the geometric constraint of developable surfaces of the cloth objects are considered. The representation of large rotation and the motion of rigid body are described using the current coordinates with the geometric constraint. The effectiveness of the present method is verified by comparing the thread deformation with the exact solution of catenary. Several examples are given to show that the proposed method converges quickly and is thus computationally efficient.

Qualitative Evaluation of Engineering Designs Using Fuzzy Logic

The paper describes a Qualitative Evaluation System developed using a fuzzy expert system. The evaluation system gives a qualitative rating to design solutions by considering manufacturability aspects, choice of materials and some special preferences. The information is used in decision support for engineering design. The system is an integrated part of a decision support tool for engineering design called the ‘Adaptive Search Manager’ (ASM). ASM uses an adaptive search technique to identify multiple design solutions for a 12 dimensional Turbine Blade Cooling System design problem. Thus the task has been to develop a fuzzy expert system that can qualitatively evaluate any design solution from a design space using a realistically small number of fuzzy rules. The developed system utilises a knowledge separation and then a knowledge integration technique. The design knowledge is first separated into three categories: inter variable knowledge, intra variable knowledge and heuristics. Inter variable knowledge and intra variable knowledge are integrated using a concept of “compromise”. The qualitative evaluation system can evaluate any design solution within the 12 dimensional design space, but uses only 44 fuzzy rules and one function that implements the inter variable knowledge.