J. Mech. Des 139(12), 121101; doi: 10.1115/1.4037627
Inayat Ullah, Dunbing Tang, Qi Wang and Leilei Yin
J. Mech. Des 139(12), 121101; doi: 10.1115/1.4037627
Delivering a variety of products with minimal lead time is a critical issue given today’s competitive manufacturing industry. Many design and production firms address the challenges of variety by adopting a product family manufacturing strategy. Product families are a broad range of artifacts, known as product variants, which share a number of common components. Thus, engineering changes in a product family affect the product under consideration and other product variants in the family. This increases the difficulty of predicting the change propagation within a family of products. This paper introduces a seven-step change propagation approach that predicts and evaluates the impact of change propagation across product variants. Interdependencies and logical relationships between directly connected components are captured using a Component-based Design Structure Matrix. This highlights the different change propagation paths that are available in the product’s structure. Risk analysis in terms of lead time is performed at the component level. The results demonstrate that avoiding project delays requires selecting suitable change propagation paths in a family of products.
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Effectiveness of an immersive virtual environment for collaboration with gesture support using low-cost hardware
Joshua Q. Coburn, John L. Salmon and Ian Freeman
J. Mech. Des 140(4), 042001 ; doi: 10.1115/1.4039006
Before the widespread use of modern computer systems, engineers worked in highly collaborative groups around large drawings tables. Today, the engineering design environment is more solitary, and collaboration often requires leaving the tools of the design environment. The highly distributed nature of today's workforce has caused a rapid proliferation of remote meetings and impeded the explanation of 3D information. While Virtual Reality (VR) has been proposed as a solution to these problems, the high cost and low availability of such systems has limited their impact. This paper presents a collaborative VR environment with support for hand gestures using readily-available, low-cost VR hardware. The environment allows multiple distributed participants to join a 3D virtual meeting, each with an independent view point, and walk around the virtual room to view the other participants as well as 3D engineering artifacts. The system supports natural communication gestures such as pointing, showing relative location, relative size, and orientation though physical hand motions. Additionally, participants can sketch in 3D using special input gestures. This allows for the communication of design concepts, design changes, and design issues. A user study is presented that demonstrates 45% faster communication compared against modern remote meeting software. Communication clarity and understanding are also improved. Future work will add deeper integration with modern engineering software and explore new design methods enabled by collaborative VR technology.
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Co-design is the integrated optimization of the physical plant and controller for an engineering system. The challenge in co-design is determining both time-invariant (physical design) variables and time-variant (control) variables. In co-design, as the size of the problem (number of variables) becomes large, the problem can become too difficult for an all-at-once solution. Our approach extends earlier research by creating a class of multi-subsystem co-design problems where both design and control are formulated and solved. A scalable test problem is used for comparing the proposed decentralized co-design optimization approach against a centralized approach. Results of this study show that the computational time of the proposed decentralized approach increases approximately linearly with respect to an increase in the number of subsystems (variables), while the computational cost of the centralized approach increases nonlinearly.
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Sheng Yang and Yaoyao Fiona Zhao
J. Mech Des 140(3):031702-031702-12. doi:10.1115/1.4038922
Part count reduction (PCR) is one motivation for using additive manufacturing (AM) processes. PCR helps simplify product structure, eliminate auxiliary connecters, and reduce assembly difficulties and cost. However, PCR may also increase manufacturing difficulty and the irreplaceability of failed subcomponents. This paper presents a pioneering investigation of how AM-enabled PCR (AM-PCR) impacts lifecycle activities. A new set of design rules and principles are proposed for PCR that lead to lowered cost and enhanced performance. The PCR problem is formulated as a combinatory optimization problem where the objective is minimizing lifecycle cost/performance ratio while ensuring conformance to all constraints (e.g. manufacturing, maintenance, and recycling). To address the challenge of computational cost, a dual-level screening and refinement product redesign framework is presented that first searches for the minimum grouping solution and then refines the remaining combinations using design optimization. This approach will help designers automate the part count reduction process enabled by additive manufacturing while exploring new design innovation opportunities.
Automatic Enumeration of Feasible Kinematic Diagrams for Split Hybrid Configurations With a Single Planetary Gear
Power-split hybrid electric vehicles embody two electric machines in addition to the internal combustion engine, and it employs one or more planetary gear sets (PG) while disposing of the transmission. Most of the prior studies on the design of power-split hybrids focused on finding optimal powertrain configurations, which are configurations specifying the components connections. However, a selected powertrain configuration cannot be physically realized as it does not specify the components arrangements in three dimensional space. Therefore, a given powertrain configuration should be depicted into feasible kinematic diagrams, which are used to generate the three dimensional drawings used for manufacturing. Multiple kinematic diagrams can be depicted for a given powertrain configuration as each kinematic diagrams specifies the exact components arrangements in addition to their connections. In this work, an automatic approach is developed to generate all the feasible kinematic diagrams for any given power-split powertrain configuration with a single PG. First, all the possible components arrangements, i.e. positioning diagrams, are generated. Then, a set of developed feasibility rules are applied on each positioning diagram in order to filter out infeasible components arrangements. Lastly, feasible kinematic diagrams are depicted for each feasible positioning diagram, and a set of preferred design criteria are used to select arrangements that best suit the vehicle’s manufacturability, packaging, maintenance, and cost. The proposed methodology guarantees automatically finding the components arrangements that best suit the desired vehicle through the search of the entire design space.
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Dipanjan Ghosh, Andrew Olewnik, Kemper Lewis, Junghan Kim and Arun Lakshmanan
J. Mech. Des 139(9), 091401 (Jul 12, 2017); doi: 10.1115/1.4036780
Understanding consumer perceptions of products and the potential impact of those perceptions on purchase decisions is critical information that should influence product development decisions. Though firms often seek consumer feedback on products, such feedback often occurs long after product use and lacks specific details about the interaction, usage context, etc. This work introduces a novel framework – Cyber-Empathic Design – that integrates sensor data and real-time user feedback to develop a more accurate model of user perceptions. The framework is applied to a case study focused on user perceptions of shoes. The results of this work demonstrate the potential for product developers to leverage the IoT (internet-of-things) movement, real-time user feedback, and advances in machine learning to connect user perceptions to specific engineered product features.
Figure: Data collection method (left) and resulting perceptual model (right).
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Configuration design problems are common in everyday life as well as engineering, with examples ranging from the selection and arrangement of furniture for a living room to the type of problem-solving used by NASA engineers to return Apollo 13 safely to Earth. There are many theoretical approaches for solving configuration design problems but few studies have examined how humans naturally solve them. This work used data-mining techniques (specifically hidden Markov models) to study the behavioral patterns shown by humans solving two distinct configuration design problems. Mining this data revealed beneficial process heuristics that are potentially generalizable to the entire class of configuration design problems. The trained models indicate that designers proceed through four procedural states, beginning in a state dominated by topology design and progressing to a final state with a focus on parameter design. The mined models also indicate that high-performing designers opportunistically tune parameters early in the process, enabling a more effective and nuanced search for good solutions.
Reinforcing ribs can significantly increase the stiffness of panels. In this study, we formulate a computational design method to determine the optimal position, dimensions and orientation of ribs made of stock plates and welded to a panel to maximize its stiffness. Typical applications of welded rib reinforcements are large metallic structures with low production volumes, for which other processes such as machining or stamping are either infeasible or too costly. These applications include, for example, ship hulls, fuel tanks, aircraft wing structures and linkage components in heavy machinery. To determine the optimal ribs layout, we formulate a topology optimization technique whereby a feature-based geometric representation of the rib is smoothly mapped onto a finite element mesh for analysis. This mesh remains fixed throughout the optimization, thus circumventing re-meshing upon changes in the ribs layout. Importantly, our method enforces geometric constraints to ensure manufacturability, namely that: a) ribs must remain vertical at all times to ensure a good quality weld; b) the ribs dimensions must not exceed those of available stock plates; c) ribs should not encroach the space above holes on the panel used for routing other components or for access; and d) there must be a minimum spacing between ribs to ensure adequate access for the welding gun. Ours is the first method to determine the optimal layout of welded ribs made of flat plates within a 3-dimensional design envelope that satisfies the foregoing geometric constraints.
Hairong Wang; Shaowei Fan; Hong Liu
J. Mech. Des. 2016; 139(1):012304-012304-12
The force and/or motion transmissibility and the analyticity of inverse kinematics for a thumb mechanism depend on thumb configuration. This paper presents a general framework for the thumb configuration and performance evaluation in the design of dexterous robotic hand. The thumb configuration is described by the functional analysis of human thumb, and the thumb of robotic hand is generalized into fifteen configurations. A performance evaluation method is proposed based on kinetostatic and dynamic dexterity as well as workspace. The kinetostatic dexterity is based on a Jacobian matrix condition number. A dynamic dexterity measure is presented via acceleration analysis, which keeps a clear geometric meaning. The proposed method is applied to evaluate the performance of three examples, which cover thumb configurations of most existing dexterous hands. Performance evaluation results demonstrate the effectiveness of the proposed method. Using these results and the proposed performance evaluation method, meaningful design principles are presented to guide the design of the thumb configuration.
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Inspiration and Fixation: The Influences of Example Designs and System Properties in Idea Generation
Luis A. Vasconcelos; Carlos C. Cardoso; Maria Sääksjärvi; Chih-Chun Chen; Nathan Crilly
J. Mech. Des. 2017; 139(3):031101-031101-13
External inspiration stimuli can be very effective to help designers arrive at new ideas that they would be otherwise unlikely to generate. However, exposure to external stimuli can also hinder creativity and fixate designers on particular features of such stimuli. We conducted an experiment with novice designers to compare the inspiration effects from two stimuli types: a concrete example solution (a bike) and an abstract property that a solution might incorporate (modularity). Working alone in a short design session, participants were asked to generate ideas to eliminate the need for people to have multiple bikes as they grow up. We found that exposure to either the concrete example or the abstract property reduced the total number of ideas generated and how diverse those ideas were, and that exposure to both stimuli (together) reduced these measures even further. We also found that each stimulus affected participants differently, encouraging ideas like one type of stimulus, while discouraging ideas like the other type. These findings reinforce the idea that external stimuli can hinder creativity and should be accessed carefully. They also show how concrete and abstract stimuli can produce similar inspiration effects, challenging our intuitions about how to encourage wide-ranging ideas. This has the potential to shape how design is taught and how inspiration tools are developed.
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This section includes brief descriptions of articles soon to be or recently published by the Journal of Mechanical Design. These featured articles highlight recent research developments and emerging trends in mechanical design. For Abstracts and Full Articles please see ASME's Digital Collection.