Steven D. Eppinger

A Model-Based Method for Organizing Tasks in Product Development

This research is aimed at structuring complex design projects in order to develop better products more quickly. We use a matrix representation to capture both the sequence of and the technical relationships among the many design tasks to be performed. These relationships define the “technical structure” of a project, which is then analyzed in order to find alternative sequences and/or definitions of the tasks. Such improved design procedures offer opportunities to speed development progress by streamlining the inter-task coordination. After using this technique to model design processes in several organizations, we have developed a design management strategy which focuses attention on the essential information transfer requirements of a technical project.

Sourcing By Design: Product Complexity and the Supply Chain

This paper focuses on the connection between product complexity and vertical integration using original empirical evidence from the auto industry. A rich literature has addressed the choice between internal production and external sourcing of components in the auto industry. More recent literature has developed the concept of product architecture as another choice variable that may be one of the important contributors to product complexity. In this paper, we connect these two important decisions and study them jointly. We use the property rights approach to argue that complexity in product design and vertical integration of production are complements: that in-house production is more attractive when product complexity is high, as firms seek to capture the benefits of their investment in the skills needed to coordinate development of complex designs. We test this hypothesis with a simultaneous equations model applied to data from the luxury-performance segment of the auto industry. We find a significant and positive relationship between product complexity and vertical integration. This has implications for optimal incentive structures within firms, as well as for interpreting firm performance.

Identifying controlling features of engineering design iteration

Engineering design often involves a very complex set of relationships among a large number of coupled problems. It is this complex coupling that leads to iteration among the various engineering tasks in a large project. The design structure matrix DSM is useful in identifying where iteration is necessary. The work transformation matrix model developed in this paper is a powerful extension of the DSM method which can predict slow and rapid convergence of iteration within a project, and predict those coupled features of the design problem which will require many iterations to reach a technical solution. This model is applied to an automotive brake-system development process in order to illustrate the models utility in describing the main features of an actual design process.

Modeling impacts of process architecture on cost and schedule risk in product development

To gain competitive leverage, firms that design and develop complex products seek to increase the efficiency and predictability of their development processes. Process improvement is facilitated by the development and use of models that account for and illuminate important characteristics of the process. Iteration is a fundamental but often unaddressed feature of product development (PD) processes. Its impact is mediated by the architecture of a process, i.e., its constituent activities and their interactions. This paper integrates several important characteristics of PD processes into a single model, highlighting the effects of varying process architecture. The PD process is modeled as a network of activities that exchange deliverables. Each activity has an uncertain duration and cost, an improvement curve, and risks of rework based on changes in its inputs. A work policy governs the timing of activity execution and deliverable exchange (and thus the amount of activity concurrency). The model is analyzed via simulation, which outputs sample cost and schedule outcome distributions. Varying the process architecture input varies the output distributions. Each distribution is used with a target and an impact function to determine a risk factor. Alternative process architectures are compared, revealing opportunities to trade cost and schedule risk. Example results and applications are shown for an industrial process, the preliminary design of an uninhabited combat aerial vehicle. The model yields and reinforces several managerial insights, including: how rework cascades through a PD process, trading off cost and schedule risk, interface criticality, and occasions for iterative overlapping.

Understanding bandwidth limitations in robot force control

This paper provides an analytical overview of the dynamics involved in force control. Models are developed which demonstrate, for the one-axis explicit force control case, the effects on system closed-loop bandwidth of a) robot system dynamics that are not usually considered in the controller design; b) drive-train and task nonlinearities; and c) actuator and controller dynamics. The merits and limitations of conventional solutions are weighed, and some new solutions are proposed. Conclusions are drawn which give insights into the relative importance of the effects discussed.

Model-based Approaches to Managing Concurrent Engineering

SUMMARY As design managers begin to implement concurrent engineering in order to reduce development time, design procedures can become more complex, potentially taking even greater time to complete. This paper discusses the basis for such design task complexity and presents a method for representing these constraints within a design process model. These models are used to explore several approaches for design process management. It is shown that while the feedback characteristic of concurrent engineering is essential to enhance design quality, this feedback causes iteration which can use up valuable engineering time. For concurrent engineering to save time, we require a framework for evaluating which tasks are vital to begin early in the development cycle, and which tasks should be left for later.

Identifying modular and integrative systems and their impact on design team interactions

The typical approach to developing complex products is to decompose the product into systems, and these into components. We introduce a new notion of system modularity based upon the way components share design interfaces across systems. Modular systems are those whose design interfaces with other systems are clustered among physically adjacent systems, whereas integrative systems are those whose interfaces are physically distributed or functionally integrative across all or most other systems. Our research method allows us to study how system modularity impacts design team interactions. Our approach is illustrated by analyzing the development of an aircraft engine.

A simulation-based process model for managing complex design projects

This paper presents a process modeling and analysis technique for managing complex design projects using advanced simulation. The model computes the probability distribution of lead time in a stochastic, resource-constrained project network where iterations take place among sequential, parallel, and overlapped tasks. The model uses the design structure matrix representation to capture the information flows between tasks. We use a simulation-based analysis to account for many realistic aspects of design process behavior which were not possible in previous analytical models. We propose a heuristic for the stochastic, resource-constrained project scheduling problem in an iterative project network. The model can be used for better project planning and control by identifying leverage points for process improvements, and for evaluating alternative planning and execution strategies. An industrial example is provided to illustrate the utility of the model.

On dynamic models of robot force control

A series of lumped-parameter models is developed in an effort to predict the dynamics of simple force-controlled robot systems. The models include some effects of robot structural dynamics, sensor compliance, and workpiece dynamics. A qualitative analysis suggests that the robot dynamics contribute to force-controlled instability.

The new practice of global product development

Many manufacturers already have established product development activities in different countries around the world. As a rule, the current approach includes colocation of cross-functional teams to foster close collaboration among engineering, marketing, manufacturing and supply-chain functions. The results to date ? better product designs, faster time to market and lower-cost production ? have been satisfactory. However, growth and innovation can now be much more effective if manufacturers tie their decentralized development organizations into a cohesive, unified global product development operation. In this article, the authors introduce new empirical frameworks to guide managers toward such practices. Citing exemplars such as Hewlett-Packard, Eastman Kodak, Hyundai Motors, Haier, Alcatel and Cummins, the authors explain why GPD has come of age and demonstrate a three-stage approach that puts product development in the context of a company?s relationships with outside partners. The article draws from extensive interviews with engineering managers at more than 100 companies in 15 countries in North America, Europe and Asia. Additional data are from a recently completed study on GPD that PTC has conducted with BusinessWeek Research Services, interviewing and surveying more than 1,100 engineering managers worldwide.