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.
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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.
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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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Development and Evaluation of a Mechanical Stance-Controlled Orthotic Knee Joint With Stance Flexion
Jan Andrysek; Matthew J. Leineweber; Hankyu Lee
J. Mech. Des. 2017; 139(3):035001-035001-7
People with severe impairment of the lower body caused by conditions such as polio or stroke often rely on assistive devices for mobility. Knee orthosis plays an important role in restoring mobility by stabilizing the weakened lower limb and providing support for standing and walking. Concurrently, the orthosis should allow for natural and efficient movement of the limb as required for walking. The focus of this work is to develop a new method for controlling orthotic knee joints. The new control method uses a mechanical system to monitor loading and timing events and patterns, and apply knee-locking function when the limb is loaded. A prototype was built and tested on a polio patient and demonstrated the feasibility of this approach for providing reliable orthotic function. Further work aims to test the knee joint on a larger group of individuals within the community.
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Design and Characterization of a Continuous Rotary Minimotor Based on Shape Memory Wires and Overrunning Clutches
An attractive but little explored field of application of the shape memory technology is the area of rotary actuators, in particular for generating endless motion. This paper presents a miniature rotary motor based on shape memory alloy (SMA) wires and overrunning clutches which produces high output torque and unlimited rotation. The concept features a SMA wire tightly wound around a low-friction cylindrical drum to convert wire strains into large rotations within a compact package. The seesaw motion of the drum ensuing from repeated contraction-elongation cycles of the wire is converted into unidirectional motion of the output shaft by an overrunning clutch fitted between drum and shaft. Following a design process formerly developed by the authors, a six-stage prototype with size envelope of 48´22´30 mm is built and tested. Diverse supply strategies are implemented to optimize either the output torque or the speed regularity of the motor with the following results: maximum torque = 20 Nmm; specific torque = 6.31´10-4 Nmm/mm3; rotation per module = 15 deg/cycle; free continuous speed = 4.4 rpm.
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Christine A. Toh, Andrew A. Strohmetz and Scarlett R. Miller
J. Mech. Des 138(10), 101105; doi: 10.1115/1.4034107
Concept selection is a critical stage of the engineering design process because of its potential to influence the direction of the final design. While formalized selection methods have been developed to increase its effectiveness and reduce human decision-making biases, research that understands these biases in more detail can provide a foundation for improving the selection process. One important bias that occurs during this process is ownership bias, or an unintentional preference for an individuals’ own ideas over the ideas of others. However, few studies have explored ownership bias in a design setting and the influence of other factors such as the gender of the designer or the “goodness” of an idea. In order to understand the impact of these factors in engineering design education, a study was conducted with 110 engineering students. The results from this study show that male students tend to show ownership bias during concept selection by selecting more of their own ideas while female students tend to show the opposite bias, the Halo Effect, by selecting more of their team members’ concepts. In addition, participants exhibited ownership bias for ideas that were considered good or high quality, but the opposite bias for ideas that were not considered good or high quality. These results add to our understanding of the factors that impact team concept selection and provide empirical evidence of the occurrence of ownership bias and the effects of gender and idea goodness in engineering design education.
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Cityplot is a new visualization technique for engineering design that uses a dimensionally-reduced representation of the design decisions to represent the mapping from the decisions to the criteria upon which a design is judged. The shown Cityplot depicts possible CubeSat constellations to support the 2007 Earth Science Decadal Survey. Each constellation is comprised of up to 4 CubeSats and each CubeSat can select from a list of 7 instruments. Possible CubeSat constellations are “cities” and are placed in a 2d space to be visualized. An individual constellation can also be seen as a table of instruments (rows) being present (black) on a given CubeSat (columns). The benefits, costs and risks of each possible constellation are represented as color-coded “buildings” in each “city”. The criteria in this example are: a tiered count of satisfied Decadal objectives (blue), the average CubeSat Technology Readiness Level (red), lifecycle cost (green), maximum number of lost instruments upon loss of a single satellite (black). A taller building indicates the possible constellation performs better in that criteria. Dark purple “roads” between two designs indicate that only one instrument is either added to or removed from one CubeSat to make one constellation identical to the other. Cityplot simultaneously shows sensitivity of criteria to decisions, criteria tradeoffs and design families via a quick intuitive view of the design space.
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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.