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M. A. McEvoy, N. Correll (2014): Shape Change Through Programmable Stiffness. International Symposium on Experimental Robotics (ISER), Springer Verlag, Marrakech, Morocco, 2014.
We present a composite material with embedded sensing and actuation that can perform permanent shape changes by temporarily varying its stiffness and applying an external moment. Varying stiffness is a complementary approach to actuator-chain based approaches that can be accomplished using a large variety of means ranging from heat, electric field or vacuum. A polycaprolactone (PCL) bar provides stiffness at room temperature. Heating elements and thermistors are distributed along the bar so that local regions can be tuned to a specific temperature/stiffness. Applying an external moment using two tendon actuators then lets the material snap into a desired shape. We describe the composite structure, the principles behind shape change using variable stiffness control, and forward and inverse kinematics of the system. We present experimental results using a 5-element bar that can assume different global conformations using two simple actuators.
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M. A. McEvoy, N. Correll (2014): "Thermoplastic variable stiffness composites with embedded, networked sensing, actuation, and control. In: Journal of Composite Materials, 49 (15), pp. 1799-1808, 2014.
We present a composite material consisting of a thermoplastic base material and embedded, networked sensing, actuation, and control to vary its stiffness locally based on computational logic. A polycaprolactone grid provides stiffness at room temperature. Each polycaprolactone element within the grid is equipped with a dedicated heating element, thermistor, and networked microcontroller that can drive the element to a desired temperature/stiffness. We present experimental results using a 4 × 1 grid that can assume different global conformations under the influence of gravity by simply changing the local stiffness of individual parts. We describe the composite structure and its manufacturing, the principles behind variable stiffness control using Joule heating, local sliding mode control of each polycaprolactone bar’s temperature and function, and limitations of the embedded multi-hop communication system. The function of the local temperature controller is evaluated experimentally.
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D. Hughes, N. Correll (2014): A Soft, Amorphous Skin that can Sense and Localize Texture . In: IEEE International Conference on Robotics and Automation (ICRA), pp. 1844-1851, Hong Kong, 2014.
We present a soft, amorphous skin that can sense and localize textures. The skin consists of a series of sensing and computing elements that are networked with their local neighbors and mimic the function of the Pascinian corpuscle in human skin. Each sensor node samples a vibration signal at 1KHz, transforms the signal into the frequency domain, and classifies up to 15 textures using logistic regression. By measuring the power spectrum of the signal and comparing it with its local neighbors, computing elements can then collaboratively estimate the location of the stimulus. The resulting low-bandwidth information, consisting of the texture probability distribution and its location are then routed to a sink anywhere in the skin in a multi-hop fashion. We describe the design, manufacturing, classification, localization and networking algorithms and experimentally validate the proposed approach. In particular, we demonstrate texture classification with 71\% accuracy and centimeter accuracy in localization over an area of approximately three square feet using ten networked sensor nodes.
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N. Farrow, N. Sivagnanadasan, N. Correll (2014): Gesture Based Distributed User Interaction System for a Reconfigurable Self-Organizing Smart Wall. In: Proceedings of the 8th International Conference on Tangible, Embedded and Embodied Interaction (TEI), pp. 245-246 , ACM 2014.
We describe user interactions with the self-organized amorphous wall, a modular, fully distributed system of computational building blocks that communicate locally for creating smart surfaces and functional room dividers. We describe a menu and a widget-based approach in which functions are color-coded and can be selected by dragging them from module to module on the surface of the wall. We also propose an on-off switch gesture and a dial gesture each spanning multiple units as canonical input mechanisms that are realized in a fully distributed way.
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S. Ma, H. Hosseinmardi, N. Farrow, R. Han, N. Correll (2012): Establishing Multi-Cast Groups in Computational Robotic Materials. In: IEEE International Conference on Cyber, Physical and Social Computing , Besancon, France, 2012.
We study an efficient ad hoc multicast communication protocol for next-generation large-scale distributed cyber-physical systems that we dub Computational Robotic Materials (CRMs). CRMs tightly integrate sensing, actuation, computation and communication, and can enable materials that can change their shape, appearance and function in response to local sensing and distributed information processing. As CRMs potentially consist of thousands of nodes with limited processing power and memory, communication in such systems poses serious challenges. For example, when processing a gesture recorded by the CRM, only a subset of nodes involved in its detection should communicate amongst themselves for distributed proessing. In previous work, we propose a Bloom filter-based approach to label the multicast group with an approximate error-resilient multicast tag that captures the temporal and spatial characteristics of the sensor group. A Bloom filter is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set. We describe our Bloom filter-based multicast communication (BMC) protocol, and report experimental results using a 48-node Computational Robotic Material test-bed engaged in shape and gesture recognition.
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H. Profita, N. Farrow, N. Correll (2012): Flutter. In: Adjunct Proceedings of the 16th International Symposium on Wearable Computers (ISWC), pp. 44-46, 2012.
Hearing is one of the fundamental sensory inputs that permits us to respond to and navigate our surrounding environment. Without intact hearing, the inability to detect warning signals such as fire alarms, police sirens, and honking horns can place individuals with impaired hearing at a significant disadvantage while navigating their environment. Common assistive technologies such as hearing aids, cochlear implants, and hearing dogs provide a means for individuals to respond to their environment more intuitively, however, the situation or context can render these aids inappropriate. Developing a wearable system to tactilely relay information can empower an individual with a hearing impairment to move confidently throughout their environment without the extraneous need of having small pieces of technology that can easily get lost (hearing aid) or the need of a canine escort (supervision can increase cognitive demand and requires one hand to maintain control of the dog). Flutter integrates function and fashion to relay information about the auditory environment for a holistic feedback system. If a sudden or loud alert is detected, such as the honk of a horn or the blare of a fire truck, the leaflets of the garment will begin to flutter in the direction and with the intensity of the signal for haptic notification.
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N. Correll, C. Onal, H. Liang, E. Schoenfeld, D. Rus (2010): Soft Autonomous Materials - Using Programmed Elasticity and Embedded Distributed Computation. In: Oussama Kahtib, Vijay Kumar; Sukhatme, Gaurav (Ed.): International Symposium on Experimental Robotics (ISER). Springer Tracts in Advanced Robotics., 2010.

The impressive agility of living systems seems to stem from modular sensing, actuation and communication capabilities, as well as intelligence embedded in the mechanics in the form of active compliance. As a step towards bridging the gap between man-made machines and their biological counterparts, we developed a class of soft mechanisms that can undergo shape change and locomotion under pneumatic actuation. Sensing, computation, communication and actuation are embedded in the material leading to an amorphous, soft material. Soft mechanisms are harder to control than stiff mechanisms as their kinematics are difficult to model and their degrees of freedom are large. Here we show instances of such mechanisms made from identical cellular elements and demonstrate shape changing, and autonomous, sensor-based locomotion using distributed control. We show that the flexible system is accurately modeled by an equivalent spring-mass model and that shape change of each element is linear with applied pressure. We also derive a distributed feedback control law that lets a belt-shaped robot made of flexible elements locomote and climb up inclinations. These mechanisms and algorithms may provide a basis for creating a new generation of biomimetic soft robots that can negotiate openings and manipulate objects with an unprecedented level of compliance and robustness.

 

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