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2019


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A semi-analytical model for dynamic analysis of non-uniform plates

Gozum, M. M., Serhat, G., Basdogan, I.

Applied Mathematical Modelling, 76, pages: 883–899, December 2019 (article)

Abstract
Dynamic properties of the plate structures can be enhanced by introducing discontinuities of different kinds such as using surface-bonded discrete patches or spatially varying the stiffness and mass properties of the plate. Fast and reliable design of such complex structures requires efficient and accurate modeling tools. In this study, a novel semi-analytical model is developed for the dynamic analysis of plates having discrete and/or continuous non-uniformities. Two-dimensional Heaviside unit step functions are utilized to represent the discontinuities. Different from existing numerical methods based on Heaviside functions, a numerical technique is proposed for modeling the discontinuities that are not necessarily aligned with the plate axes. The governing equations are derived using Hamilton's principle and Rayleigh–Ritz method is used for determining the modal variables. The surface-bonded patches are used to demonstrate discrete non-uniformities where variable-stiffness laminates are selected to represent continuous non-uniform structures. Natural frequencies and mode shapes obtained using the proposed method are validated with finite element analyses and the existing results from the literature. The results show that the developed model performs accurately and efficiently.

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DOI [BibTex]

2019


DOI [BibTex]


A Robotic Framework to Facilitate Sensory Experiences for Children with Autism Spectrum Disorder: A Preliminary Study
A Robotic Framework to Facilitate Sensory Experiences for Children with Autism Spectrum Disorder: A Preliminary Study

Javed, H., Burns, R., Jeong, M., Howard, A. M., Park, C. H.

ACM Transactions on Human-Robot Interaction (THRI), 9(1), December 2019 (article)

Abstract
The diagnosis of Autism Spectrum Disorder (ASD) in children is commonly accompanied by a diagnosis of sensory processing disorders. Abnormalities are usually reported in multiple sensory processing domains, showing a higher prevalence of unusual responses, particularly to tactile, auditory, and visual stimuli. This article discusses a novel robot-based framework designed to target sensory difficulties faced by children with ASD in a controlled setting. The setup consists of a number of sensory stations, together with two different robotic agents that navigate the stations and interact with the stimuli. These stimuli are designed to resemble real-world scenarios that form a common part of one’s everyday experiences. Given the strong interest of children with ASD in technology in general and robots in particular, we attempt to utilize our robotic platform to demonstrate socially acceptable responses to the stimuli in an interactive, pedagogical setting that encourages the child’s social, motor, and vocal skills, while providing a diverse sensory experience. A preliminary user study was conducted to evaluate the efficacy of the proposed framework, with a total of 18 participants (5 with ASD and 13 typically developing) between the ages of 4 and 12 years. We derive a measure of social engagement, based on which we evaluate the effectiveness of the robots and sensory stations to identify key design features that can improve social engagement in children.

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DOI [BibTex]

DOI [BibTex]


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Multi-objective optimization of composite plates using lamination parameters

Serhat, G., Basdogan, I.

Materials & Design, 180(107904), October 2019 (article)

Abstract
Laminated composite plates are extensively used in various industries due to their high stiffness-to-weight ratio and directional properties that allow optimization of the stiffness characteristics for specific applications. In multi-objective optimization problems, optimal designs for individual performance metrics may be conflicting, necessitating knowledge on the design requirements for different metrics and potential trade-offs. In this paper, a multi-objective design methodology for laminated composite plates with dynamic and load-carrying requirements is presented. Lamination parameters are used to characterize laminate stiffness matrices in a compact form resulting in a convex design space. Single and multi-objective optimization studies are carried out to determine the optimal stiffness properties. For improving the dynamic performance, maximization of the fundamental frequency metric is aimed. For enhancing the load-carrying capability, buckling load and equivalent stiffness metrics are maximized. Conforming and conflicting behavior of multiple objective functions for different plate geometries, boundary conditions and load cases are presented by determining Pareto-optimal solutions. The results provide a valuable insight for multi-objective optimization of laminated composite plates and show that presented methodology can be used in the design of such structures for improving the dynamic and load-carrying performance.

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DOI [BibTex]

DOI [BibTex]


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Lamination parameter interpolation method for design of manufacturable variable-stiffness composite panels

Serhat, G., Basdogan, I.

AIAA Journal, 57(7):3052–3065, July 2019 (article)

Abstract
Variable-stiffness laminates have lately drawn attention because they offer potential for additional structural performance improvements. In the optimization studies, laminate stiffness properties can be described efficiently by using lamination parameters, which is a well-established formulation for constant-stiffness laminates. However, ensuring manufacturability in the design of variable-stiffness laminates with lamination parameters is difficult. In this paper, a novel method for the design of variable-stiffness composite panels using lamination parameters is proposed. The method constrains the design space by controlling the magnitude and direction of change for the lamination parameters, and subsequently leads to a smooth change in the fiber angles. The method is used to maximize the fundamental frequencies of several panels as example cases. The solutions are calculated for various panel geometries and boundary conditions using the developed finite element analysis software. After finding optimal lamination parameter distributions, corresponding discrete fiber angles and fiber paths are retrieved, and the minimum radii of curvature are calculated. The results demonstrate that the proposed design method provides manufacturable smooth fiber paths while using the compact stiffness formulation feature of lamination parameters.

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DOI [BibTex]


Implementation of a 6-{DOF} Parallel Continuum Manipulator for Delivering Fingertip Tactile Cues
Implementation of a 6-DOF Parallel Continuum Manipulator for Delivering Fingertip Tactile Cues

Young, E. M., Kuchenbecker, K. J.

IEEE Transactions on Haptics, 12(3):295-306, June 2019 (article)

Abstract
Existing fingertip haptic devices can deliver different subsets of tactile cues in a compact package, but we have not yet seen a wearable six-degree-of-freedom (6-DOF) display. This paper presents the Fuppeteer (short for Fingertip Puppeteer), a device that is capable of controlling the position and orientation of a flat platform, such that any combination of normal and shear force can be delivered at any location on any human fingertip. We build on our previous work of designing a parallel continuum manipulator for fingertip haptics by presenting a motorized version in which six flexible Nitinol wires are actuated via independent roller mechanisms and proportional-derivative controllers. We evaluate the settling time and end-effector vibrations observed during system responses to step inputs. After creating a six-dimensional lookup table and adjusting simulated inputs using measured Jacobians, we show that the device can make contact with all parts of the fingertip with a mean error of 1.42 mm. Finally, we present results from a human-subject study. A total of 24 users discerned 9 evenly distributed contact locations with an average accuracy of 80.5%. Translational and rotational shear cues were identified reasonably well near the center of the fingertip and more poorly around the edges.

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DOI Project Page [BibTex]


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The Perception of Ultrasonic Square Reductions of Friction With Variable Sharpness and Duration

Gueorguiev, D., Vezzoli, E., Sednaoui, T., Grisoni, L., Lemaire-Semail, B.

IEEE Transactions on Haptics, 12(2):179-188, January 2019 (article)

Abstract
The human perception of square ultrasonic modulation of the finger-surface friction was investigated during active tactile exploration by using short frictional cues of varying duration and sharpness. In a first experiment, we asked participants to discriminate the transition time and duration of short square ultrasonic reductions of friction. They proved very sensitive to discriminate millisecond differences in these two parameters with the average psychophysical thresholds being 2.3–2.4 ms for both parameters. A second experiment focused on the perception of square friction reductions with variable transition times and durations. We found that for durations of the stimulation larger than 90 ms, participants often perceived three or four edges when only two stimulations were presented while they consistently felt two edges for signals shorter than 50 ms. A subsequent analysis of the contact forces induced by these ultrasonic stimulations during slow and fast active exploration showed that two identical consecutive ultrasonic pulses can induce significantly different frictional dynamics especially during fast motion of the finger. These results confirm the human sensitivity to transient frictional cues and suggest that the human perception of square reductions of friction can depend on their sharpness and duration as well as on the speed of exploration.

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DOI [BibTex]

DOI [BibTex]


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How Does It Feel to Clap Hands with a Robot?

Fitter, N. T., Kuchenbecker, K. J.

International Journal of Social Robotics, 2019 (article) Accepted

Abstract
Future robots may need lighthearted physical interaction capabilities to connect with people in meaningful ways. To begin exploring how users perceive playful human–robot hand-to-hand interaction, we conducted a study with 20 participants. Each user played simple hand-clapping games with the Rethink Robotics Baxter Research Robot during a 1-h-long session involving 24 randomly ordered conditions that varied in facial reactivity, physical reactivity, arm stiffness, and clapping tempo. Survey data and experiment recordings demonstrate that this interaction is viable: all users successfully completed the experiment and mentioned enjoying at least one game without prompting. Hand-clapping tempo was highly salient to users, and human-like robot errors were more widely accepted than mechanical errors. Furthermore, perceptions of Baxter varied in the following statistically significant ways: facial reactivity increased the robot’s perceived pleasantness and energeticness; physical reactivity decreased pleasantness, energeticness, and dominance; higher arm stiffness increased safety and decreased dominance; and faster tempo increased energeticness and increased dominance. These findings can motivate and guide roboticists who want to design social–physical human–robot interactions.

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[BibTex]

[BibTex]


Tactile Roughness Perception of Virtual Gratings by Electrovibration
Tactile Roughness Perception of Virtual Gratings by Electrovibration

Isleyen, A., Vardar, Y., Basdogan, C.

IEEE Transactions on Haptics, 2019 (article) Accepted

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[BibTex]

[BibTex]

2016


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An electro-active polymer based lens module for dynamically varying focal system

Yun, S., Park, S., Nam, S., Park, B., Park, S. K., Mun, S., Lim, J. M., Kyung, K.

Applied Physics Letters, 109(14):141908, October 2016 (article)

Abstract
We demonstrate a polymer-based active-lens module allowing a dynamic focus controllable optical system with a wide tunable range. The active-lens module is composed of parallelized two active- lenses with a convex and a concave shaped hemispherical lens structure, respectively. Under opera- tion with dynamic input voltage signals, each active-lens produces translational movement bi-directionally responding to a hybrid driving force that is a combination of an electro-active response of a thin dielectric elastomer membrane and an electro-static attraction force. Since the proposed active lens module widely modulates a gap-distance between lens-elements, an optical system based on the active-lens module provides widely-variable focusing for selective imaging of objects in arbitrary position.

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link (url) DOI [BibTex]

2016


link (url) DOI [BibTex]


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Wrinkle structures formed by formulating UV-crosslinkable liquid prepolymers

Park, S. K., Kwark, Y., Nam, S., Park, S., Park, B., Yun, S., Moon, J., Lee, J., Yu, B., Kyung, K.

Polymer, 99, pages: 447-452, September 2016 (article)

Abstract
Artificial wrinkles have recently been in the spotlight due to their potential use in high-tech applications. A spontaneously wrinkled film can be fabricated from UV-crosslinkable liquid prepolymers. Here, we controlled the wrinkle formation by simply formulating two UV-crosslinkable liquid prepolymers, tetraethylene glycol bis(4-ethenyl-2,3,5,6-tetrafluorophenyl) ether (TEGDSt) and tetraethylene glycol diacrylate (TEGDA). The wrinkles were formed from the TEGDSt/TEGDA formulated prepolymer layers containing up to 30 wt% of TEGDA. The wrinkle formation depended upon the rate of photo-crosslinking reaction of the formulated prepolymers. The first order apparent rate constant, kapp, was between ca. 5.7 × 10−3 and 12.2 × 10−3 s−1 for the wrinkle formation. The wrinkle structures were modulated within the kapp mainly due to variation in the extent of shrinkage of the formulated prepolymer layers with the content of TEGDA

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Objective assessment of robotic surgical skill using instrument contact vibrations

Gomez, E. D., Aggarwal, R., McMahan, W., Bark, K., Kuchenbecker, K. J.

Surgical Endoscopy, 30(4):1419-1431, 2016 (article)

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[BibTex]

[BibTex]


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Cutaneous Feedback of Fingertip Deformation and Vibration for Palpation in Robotic Surgery

Pacchierotti, C., Prattichizzo, D., Kuchenbecker, K. J.

IEEE Transactions on Biomedical Engineering, 63(2):278-287, February 2016 (article)

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[BibTex]

[BibTex]


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Structure modulated electrostatic deformable mirror for focus and geometry control

Nam, S., Park, S., Yun, S., Park, B., Park, S. K., Kyung, K.

Optics Express, 24(1):55-66, OSA, January 2016 (article)

Abstract
We suggest a way to electrostatically control deformed geometry of an electrostatic deformable mirror (EDM) based on geometric modulation of a basement. The EDM is composed of a metal coated elastomeric membrane (active mirror) and a polymeric basement with electrode (ground). When an electrical voltage is applied across the components, the active mirror deforms toward the stationary basement responding to electrostatic attraction force in an air gap. Since the differentiated gap distance can induce change in electrostatic force distribution between the active mirror and the basement, the EDMs are capable of controlling deformed geometry of the active mirror with different basement structures (concave, flat, and protrusive). The modulation of the deformed geometry leads to significant change in the range of the focal length of the EDMs. Even under dynamic operations, the EDM shows fairly consistent and large deformation enough to change focal length in a wide frequency range (1~175 Hz). The geometric modulation of the active mirror with dynamic focus tunability can allow the EDM to be an active mirror lens for optical zoom devices as well as an optical component controlling field of view.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Peripheral vs. central determinants of vibrotactile adaptation

Klöcker, A., Gueorguiev, D., Thonnard, J. L., Mouraux, A.

Journal of Neurophysiology, 115(2):685-691, 2016, PMID: 26581868 (article)

Abstract
Long-lasting mechanical vibrations applied to the skin induce a reversible decrease in the perception of vibration at the stimulated skin site. This phenomenon of vibrotactile adaptation has been studied extensively, yet there is still no clear consensus on the mechanisms leading to vibrotactile adaptation. In particular, the respective contributions of 1) changes affecting mechanical skin impedance, 2) peripheral processes, and 3) central processes are largely unknown. Here we used direct electrical stimulation of nerve fibers to bypass mechanical transduction processes and thereby explore the possible contribution of central vs. peripheral processes to vibrotactile adaptation. Three experiments were conducted. In the first, adaptation was induced with mechanical vibration of the fingertip (51- or 251-Hz vibration delivered for 8 min, at 40× detection threshold). In the second, we attempted to induce adaptation with transcutaneous electrical stimulation of the median nerve (51- or 251-Hz constant-current pulses delivered for 8 min, at 1.5× detection threshold). Vibrotactile detection thresholds were measured before and after adaptation. Mechanical stimulation induced a clear increase of vibrotactile detection thresholds. In contrast, thresholds were unaffected by electrical stimulation. In the third experiment, we assessed the effect of mechanical adaptation on the detection thresholds to transcutaneous electrical nerve stimuli, measured before and after adaptation. Electrical detection thresholds were unaffected by the mechanical adaptation. Taken together, our results suggest that vibrotactile adaptation is predominantly the consequence of peripheral mechanoreceptor processes and/or changes in biomechanical properties of the skin.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Silent Expectations: Dynamic Causal Modeling of Cortical Prediction and Attention to Sounds That Weren’t

Chennu, S., Noreika, V., Gueorguiev, D., Shtyrov, Y., Bekinschtein, T. A., Henson, R.

Journal of Neuroscience, 36(32):8305-8316, Society for Neuroscience, 2016 (article)

Abstract
There is increasing evidence that human perception is realized by a hierarchy of neural processes in which predictions sent backward from higher levels result in prediction errors that are fed forward from lower levels, to update the current model of the environment. Moreover, the precision of prediction errors is thought to be modulated by attention. Much of this evidence comes from paradigms in which a stimulus differs from that predicted by the recent history of other stimuli (generating a so-called {\textquotedblleft}mismatch response{\textquotedblright}). There is less evidence from situations where a prediction is not fulfilled by any sensory input (an {\textquotedblleft}omission{\textquotedblright} response). This situation arguably provides a more direct measure of {\textquotedblleft}top-down{\textquotedblright} predictions in the absence of confounding {\textquotedblleft}bottom-up{\textquotedblright} input. We applied Dynamic Causal Modeling of evoked electromagnetic responses recorded by EEG and MEG to an auditory paradigm in which we factorially crossed the presence versus absence of {\textquotedblleft}bottom-up{\textquotedblright} stimuli with the presence versus absence of {\textquotedblleft}top-down{\textquotedblright} attention. Model comparison revealed that both mismatch and omission responses were mediated by increased forward and backward connections, differing primarily in the driving input. In both responses, modeling results suggested that the presence of attention selectively modulated backward {\textquotedblleft}prediction{\textquotedblright} connections. Our results provide new model-driven evidence of the pure top-down prediction signal posited in theories of hierarchical perception, and highlight the role of attentional precision in strengthening this prediction.SIGNIFICANCE STATEMENT Human auditory perception is thought to be realized by a network of neurons that maintain a model of and predict future stimuli. Much of the evidence for this comes from experiments where a stimulus unexpectedly differs from previous ones, which generates a well-known {\textquotedblleft}mismatch response.{\textquotedblright} But what happens when a stimulus is unexpectedly omitted altogether? By measuring the brain{\textquoteright}s electromagnetic activity, we show that it also generates an {\textquotedblleft}omission response{\textquotedblright} that is contingent on the presence of attention. We model these responses computationally, revealing that mismatch and omission responses only differ in the location of inputs into the same underlying neuronal network. In both cases, we show that attention selectively strengthens the brain{\textquoteright}s prediction of the future.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Touch uses frictional cues to discriminate flat materials

Gueorguiev, D., Bochereau, S., Mouraux, A., Hayward, V., Thonnard, J.

Scientific reports, 6, pages: 25553, Nature Publishing Group, 2016 (article)

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[BibTex]

[BibTex]

2012


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Evaluation of Tactile Feedback Methods for Wrist Rotation Guidance

Stanley, A. A., Kuchenbecker, K. J.

IEEE Transactions on Haptics, 5(3):240-251, July 2012 (article)

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[BibTex]

2012


[BibTex]


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Creating realistic virtual textures from contact acceleration data

Romano, J. M., Kuchenbecker, K. J.

IEEE Transactions on Haptics, 5(2):109-119, April 2012, Cover article (article)

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[BibTex]

[BibTex]


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Construct Validity of Instrument Vibrations as a Measure of Robotic Surgical Skill

Gomez, E. D., Bark, K., Rivera, C., McMahan, W., Remington, A., Lee, D. I., Williams, N., Murayama, K., Dumon, K., Kuchenbecker, K. J.

Journal of the American College of Surgeons, 215(3):S119-120, Chicago, Illinois, USA, 2012, Oral presentation given by Gomez at the {\em American College of Surgeons (ACS) Clinical Congress} (article)

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[BibTex]

[BibTex]

2005


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Contact Location Display for Haptic Perception of Curvature and Object Motion

Provancher, W. R., Cutkosky, M. R., Kuchenbecker, K. J., Niemeyer, G.

International Journal of Robotics Research, 24(9):691-702, sep 2005 (article)

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[BibTex]

2005


[BibTex]