Restart Strategies for Constraint-Handling in Generative Design Systems

Product alternatives suggested by a generative design system often need to be evaluated on qualitative criteria. This evaluation necessitates that several feasible solutions which fulfill all technical constraints can be proposed to the user of the system. Also, as concept development is an iterative process, it is important that these solutions are generated quickly; i.e., the system must have a low convergence time. A problem, however, is that stochastic constraint-handling techniques can have highly unpredictable convergence times, spanning several orders of magnitude, and might sometimes not converge at all. A possible solution to avoid the lengthy runs is to restart the search after a certain time, with the hope that a new starting point will lead to a lower overall convergence time, but selecting an optimal restart-time is not trivial. In this paper, two strategies are investigated for such selection, and their performance is evaluated on two constraint-handling techniques for a product design problem. The results show that both restart strategies can greatly reduce the overall convergence time. Moreover, it is shown that one of the restart strategies can be applied to a wide range of constraint-handling techniques and problems, without requiring any fine-tuning of problem-specific parameters

Strategies for consumer control of complex product forms in generative design systems

In recent years, the number of products that can be tailored to consumers' needs and desires has increased dramatically; there are many opportunities to individualize the colors, materials or options of products. However, current trends indicate that the future consumer will not be satisfied with mere material and color choices, but will desire control over form as well. While it is technically feasible to allow consumers to partially mass-customize the form of products subject to functional and production constraints through the use of a generative design system, the question of how the control of form should be presented to the user arises. The issue becomes especially important when the product form is based on complex morphologies, which require in-depth knowledge of their parameters to be able to control them fully. In this paper, we discuss this issue and present and test two strategies for controlling complex forms in consumer-oriented generative design systems, one offering the user full control over the design ("total control" strategy), while the other automatically generates designs for the user ("no control" strategy). The implementation of those two control strategies in a generative design system for two categories of products (bookshelf and table) and five types of morphologies are described and tested with a number of design interested participants to estimate their level of satisfaction with the two control strategies. The empirical study shows that the participants enjoyed both the total control and no control strategies. The development of the full control modes for the five morphologies was on the other hand not straightforward, and in general, making the controls meaningful to the consumer can be difficult with complex morphologies. It seems that a consumer-oriented generative design system with two different control strategies, as the ones presented in this article, would offer the most satisfaction

Study of the sequential constraint-handling technique for evolutionary optimization with application to structural problems

Engineering design problems are most frequently charac-terized by constraints that make them hard to solve and time-consuming. When evolutionary algorithms are used to solve these problems, constraints are often handled with the generic weighted sum method or with techniques specific to the prob-lem at hand. Most commonly, all constraints are evaluated at each generation, and it is also necessary to fine-tune different parameters in order to receive good results, which requires in-depth knowledge of the algorithm. The sequential constraint-handling techniques seem to be a promising alternative, be-cause they do not require all constraints to be evaluated at each iteration and they are easy to implement. They neverthe-less require the user to determine the ordering in which those constraints shall be evaluated. Therefore two heuristics that allow finding a satisfying constraint sequence have been developed. Two sequential constraint-handling techniques using the heuristics have been tested against the weighted sum technique with the ten-bar structure benchmark. They both performed better than the weighted sum technique and can therefore be easy to implement, and powerful alternatives for solving engineering design problems

Out of focus - The limits of a borderline profession

The elusive chimaera “design” has been, in turn, an idea, a plan, a purpose, a sketch, a process, the result of a process, the core of a profession and the core of emerging professions… As such, the concept of what design is, will remain contradictory and resist to being ever determined in the absolute: the limitations of design are those that are imposed by those who define them. On an abstract level, there is no fear and there are no boundaries; but then, stretching the term to verge on the all-encompassing for a political agenda, the design profession and its research community is already instrumental for disentitling it of relevance: positioning design as the panacea for all problems afflicting the world. If design and design research will ever mature, the reflections on it will have to be put into a context: if there can ever be a design science – as long as it remains a science of the artificial, linked to human activity – it will be irredeemably linked to a field of application. Otherwise, it will lead to cursory outcomes of shallow depth, promoting a process of mere scientification and aggrandisation

Genetiska algoritmer och deras tillämpningar inom konstruktion och design

This Master’s Thesis has shown possible applications of genetic optimization algorithms (GA) within design. A framework for structural optimization with genetic algorithms was built and used to show the possibilities of using GA to create concept designs given just the boundary conditions and requirements of a structure. A comparison between the optimization of the load bearing beam of an automated crane using traditional development methods and using the developed framework was then carried out and was found to give very promising results. The final project was to adapt a very light and strong structure found in nature, which can be described by a Voronoi diagram, to a table using GA. The use of natural structures in design has long been prohibited by the complexity of the structures, which makes them very difficult to adapt in a way that is possible to manufacture, cost effective and structurally sound. The developed computer application made it possible for a customer to define an arbitrary contour of a table, the position of the legs and its height and then have it optimized to be as light and strong as possible and still meet manufacturing requirements

Gait Biomechanics While Walking Down an Incline After Exhaustion

This gait biomechanics study investigated stride length (SL), stride duration (SDN), the peak values of ground reaction forces (GRFspeak), required coefficient of friction (RCOFpeak), leg joints’ angles (anglepeak), angular velocity (angvelx.peak), angular acceleration (angaccx.peak), minimum angle (anglemin.) of the foot, and muscles’ electromyography (EMG) during the stance phase (SP) of the dominant leg following an exhaustive stair ascent on a stair machine. Data were collected by a three-dimensional motion capture system synchronized with EMG and force plate while walking down a 10° inclined stationary walkway. Although the leg muscles’ EMG showed no significant local muscle fatigue (LMF) during post-exhaustive walking downwards, the SL was significantly (

Constraint-handling techniques for generative product design systems in the mass customization context

Generative product design systems used in the context of mass customization are required to generate diverse solutions quickly and reliably without necessitating modification or tuning during use. When such systems are employed to allow for the mass customization of product form, they must be able to handle mass production and engineering constraints that can be time-consuming to evaluate and difficult to fulfill. These issues are related to how the constraints are handled in the generative design system. This article evaluates two promising sequential constraint-handling techniques and the often used weighted sum technique with regard to convergence time, convergence rate, and diversity of the design solutions. The application used for this purpose was a design system aimed at generating a table with an advanced form: a Voronoi diagram based structure. The design problem was constrained in terms of production as well as stability, requiring a timeconsuming finite element evaluation. Regarding convergence time and rate, one of the sequential constraint-handling techniques performed significantly better than the weighted sum technique. Nevertheless, the weighted sum technique presented respectable results and therefore remains a relevant technique. Regarding diversity, none of the techniques could generate diverse solutions in a single search run. In contrast, the solutions from different searches were always diverse. Solution diversity is thus gained at the cost of more runs, but no evaluation of the diversity of the solutions is needed. This result is important, because a diversity evaluation function would otherwise have to be developed for every new type of design. Efficient handling of complex constraints is an important step toward mass customization of nontrivial product forms

An approach to constraint-based and mass-customizable product design

In traditional product development, several iterations are usually necessary to obtain a successful compromise between constraints emanating from engineering, manufacturing, and aesthetics. Moreover, this approach to product development is not well suited for true mass-customization, as the manufacturing company remains in control of all aspects of the shape of the product-to-be. In this article, we propose an alternative approach that would (1) allow for an improved integration of industrial design into the product development process and (2) enhance the creative repertoire of industrial designers, which (3) would result in significantly improved prospects for mass-customization. The industrial design process may benefit from using advanced and aesthetically interesting morphologies emanating from the areas of mathematics and nature. Such complex morphologies can only be manipulated (analyzed and represented) by means of specific algorithms. On one hand, this requires a shift from established industrial design practice, where the industrial designer is in total control of the product form; on the other hand, it makes it fully possible to compute form so that it complies with engineering and manufacturing constraints. In this setup, the industrial designer still has control of the final result, in that she or he can choose from a set of valid forms. This approach would greatly reduce the number of iterations in the product development process between industrial design, engineering, and production. Naturally, such an approach also allows for advanced masscustomization by allowing consumers to use these tools. Within this approach, a table generation system has been developed: A system that generates tables whose support structure is based on a Voronoi diagram that fulfills structural and manufacturing constraints while being aesthetically appealing