Determination of the Minimum Distance Between Moving Objects Including Velocity Information

The rapid determination of the minimum distance between objects is of importance in collision avoidance for a robot maneuvering among obstacles. Currently, the fastest algorithms for the solution of this problem are based on the use of optimization techniques to minimize a distance function. Furthermore, to date this problem has been approached purely through the position kinematics of the two objects. However, although the minimum distance between two objects can be found quickly on state-of-the-art hardware, the modelling of realistic scenes entails the determination of the minimum distances between large numbers of pairs of objects, and the computation time to calculate the overall minimum distance between any two objects is significant, and introduces a delay which has serious repercussions on the real-time control of the robot. This paper presents a technique to modify the original optimization problem in order to include velocity information. In effect, the minimum distance calculation is performed at a future time step by projecting the effect of present velocity. This method has proven to give good results on a 6-dof robot maneuvering among obstacles, and has allowed a complete compensation of the lags incurred due to computational delays.

Five-Axis Constrained and Optimal Orientation Planning

The five-axis constrained and optimal orientation planning is formulated as a design optimization problem that incorporates the process machine’s kinematic constraints with the workpiece and tool geometry, to obtain a constrained setup orientation which exploits the maximum capabilities of existing machines. This work will introduce this problem, and will obtain the setup orientation for two different types of rotation structures, i.e., tool rotation and table rotation in O(N) time. Further, the obtained constrained setup orientation, will be augmented to incorporate the workpiece surface magnitude, along with different machine rotation structures, to obtain an optimal setup orientation for different machine rotation structures. The drilling process is also introduced and formulated as additional constraints to the optimization problem. The primary application of the introduced algorithms, is the machining process, where, they can efficiently reduce the number of tool motions and surface finishing processes. However, the solution is very suitable for many manufacturing applications, such as inspection, assembly, robotics, painting, welding, aerospace, electronic surface mount technology, and etc.

Issues in Product Life Cycle Engineering Analysis

Traditional engineering analysis of product designs has focused primarily on a product’s operational performance without considering costs of manufacturing and other stages downstream from design. In contrast, life cycle analysis of a product during its initial development can play a crucial role in determining the product’s overall life cycle cost and useful life span. This paper examines product life cycle engineering analysis - measurement of product operational performance in a life cycle context. Life cycle engineering analysis is thus considered both as an extension of traditional engineering analysis methods and as a subset of a total product life cycle analysis. The issues critical to life cycle engineering analysis are defined and include product life cycle data modeling and analysis, analysis tools and their performance regimes, performance tradeoff measurement and problems of life cycle engineering analysis in an organizational context. Recommendations are provided for future research directions into life cycle engineering analysis in the context of integration architectures for concurrent engineering.

An Area Preserving Transformation Algorithm for Press Forming Blank Development

An efficient algorithm is presented to determine the blank shape necessary to manufacture a surface by press forming. The technique is independent of material properties and instead uses surface geometry and an area conservation constraint to generate a geometrically feasible blank shape. The algorithm is formulated as an approximate geometric interpretation of the reversal of the forming process. The primary applications for this technique are in preliminary surface design, assessment of manufacturability, and location of binder wrap. Since the algorithm exhibits linear time complexity, it is amenable to implementation as an interactive design aid. The algorithm is applied to two example surfaces and the results are discussed.

A Form Verification System for the Conceptual Design of Complex Mechanical Systems

This paper presents a summary of research into the development and implementation of a domain independent, computer-based model for the conceptual design of complex mechanical systems (Ouellette, 1992). The creation of such a design model includes the integration of four major concepts: (1) The use of a graphical display for visualizing the conceptual design attributes; (2) The proper representation of the complex data and diverse knowledge required to design the system; (3) The integration of quality design methods into the conceptual design; and (4) The modeling of the conceptual design process as a mapping between functions and forms. Using the design of an automobile as a case study, a design environment was created which consisted of a distributed problem solving paradigm and a parametric graphical display. The requirements of the design problem with respect to data representation and design processing were evaluated and a process model was specified. The resulting vehicle design system consists of a tight integration between a blackboard system and a parametric design system. The completed system allows a designer to view graphical representations of the candidate conceptual designs that the blackboard system generates.

A Sequential Approximation Method for Structural Optimization Using Logarithmic Barriers

A sequential approximation technique for non-linear programming is presented here that is particularly suited for problems in engineering design and structural optimization, where the number of variables are very large and function and sensitivity evaluations are computationally expensive. A sequence of sub-problems are iteratively generated using a linear approximation for the objective function and setting move limits on the variables using a barrier method. These sub-problems are strictly convex. Computation per iteration is significantly reduced by not solving the sub-problems exactly. Instead at each iteration, a few Newton-steps are taken for the sub-problem. A criteria for moving the move limit, is described that reduces or eliminates stepsize reduction during line search. The method was found to perform well for unconstrained and linearly constrained optimization problems. It requires very few function evaluations, does not require the hessian of the objective function and evaluates its gradient only once per iteration.

Layout of Plate Structures for Improved Dynamic Response Using a Homogenization Method

A model to compute average properties for Mindlin plates of rapidly varying thickness was introduced in [SOT93]. The model was designed to be of use in computations of the optimum shape and layout of plates using the technique introduced by Bendsøe and Kikuchi [BEN88]. In this paper we discuss the utilization of the model to determine the optimum layout of plate structures that maximizes a function of the structure’s natural frequencies. A simply supported square plate is used to illustrate the problem of optimization in the presence of repeated natural frequencies. An automotive application is presented to illustrate the usefulness in design practice.

Genesis of Ribbed Plate and Shells With Isotropic Density Dependent Material

An essential part in the genesis of structures or optimal material distribution is the relation between elastic behaviour and material density. This approach makes use of a isotropic material model, which leads to very simple working conditions. The isotropic model is directly formulated and utilized without employing homogenization based on an artificial microstructure. It is shown in theoretical considerations and demonstrated by examples, that this idea works also very easily with plate and shells, even for very general layer structures.

Abstraction As a Configuration Design Methodology

Configuration design can be thought of as a process of generating artifacts by assembling pre-defined components. This paper introduces a method for reducing the size of configuration problems by abstracting components to higher levels of abstraction. At higher abstraction levels, less important detail is temporarily ignored, and each component represents a family of lower-level components. Configuration is then performed at the highest level, explicitly enumerating all configurations at that level. Any complete configuration at the highest level is recursively instantiated to lower levels. At the same time, any incomplete configuration at the highest level is eliminated, thereby eliminating all possible lower-level instantiations of that configuration. In this manner, all configurations of components at the lowest level of abstraction are implicitly enumerated.

A Robust Optimization Method for Systems With Significant Nonlinear Effects

This paper describes a robust optimization methodology for design involving either complex simulations or actual experiments. The proposed procedure optimizes the worst case response that consists of a weighted sum of expected mean and response variance. The estimation scheme for expected mean and variance adopts the modified 3-point Gauss quadrature integration to assure superior accuracy for systems with significant nonlinear effects. We apply the proposed method to the robust design of geometric parameters of heat treated parts to minimize the cost of post heat treatment operations. The paper investigates the major factors influencing geometric distortions due to heat treatment and the rules of thumb in design. The study focuses on relating dimensional distortion to the design of part geometry. To illustrate the utility of the proposed method, we present the formulation of a case study on allocation of dimensions of preheat treated (green) shafts to minimize the cost of post heat treatment operations. The final result is not presented yet pending the completion of further experiments.