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Wood, Robert

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Wood

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Robert

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Wood, Robert
Author's Publications: search.filters.isAuthorOfPublication.79d9d4bc-077c-416e-8694-19d17ae53050

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Now showing 1 - 10 of 19
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    Untethered Flight of an Insect-Sized Flapping-Wing Microscale Aerial Vehicle
    (Springer Science and Business Media LLC, 2019-06) Karpelson, Michael; Wood, Robert; Jafferis, Noah; Helbling, Elizabeth
    Heavier-than-air flight at any scale is energetically expensive. This is greatly exacerbated at small scales and has so far presented an insurmountable obstacle for untethered flight in insect-sized (mass less than 500 milligrams and wingspan less than 5 centimetres) robots. These vehicles thus need to fly tethered to an offboard power supply and signal generator owing to the challenges associated with integrating onboard electronics within a limited payload capacity. Here we address these challenges to demonstrate sustained untethered flight of an insect-sized flapping-wing microscale aerial vehicle. The 90-milligram vehicle uses four wings driven by two alumina-reinforced piezoelectric actuators to increase aerodynamic efficiency (by up to 29 per cent relative to similar two-wing vehicles) and achieve a peak lift-to-weight ratio of 1 to 1, demonstrating greater thrust per muscle mass than typical biological counterparts6. The integrated system of the vehicle together with the electronics required for untethered flight (a photovoltaic array and a signal generator) weighs 259 milligrams, with an additional payload capacity allowing for additional onboard devices. Consuming only 110–120 milliwatts of power, the system matches the thrust efficiency of similarly sized insects such as bees. This insect-scale aerial vehicle is the lightest thus far to achieve sustained untethered flight (as opposed to impulsive jumping8 or liftoff).
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    Ultra-sensitive and resilient compliant strain gauges for soft machines
    (Springer Science and Business Media LLC, 2020-11-11) Araromi, Oluwaseun A.; Graule, Moritz; Dorsey, Kristen; Castellanos, Samantha; Foster, Jonathan; Hsu, Wen-Hao; Passy, Arthur; Vlassak, Joost; Weaver, James; Walsh, Conor; Wood, Robert
    Soft machines are a promising new design paradigm for human-centric devices and systems required to interact gently with their environment. For soft machines to respond intelligently to their surroundings, compliant sensory feedback mechanisms are needed. Specifically, soft alternatives to strain gauges – possessing high resolution at low strain ranges (< 5%), could unlock promising new capabilities in soft systems. However, currently available sensing mechanisms typically possess either high strain sensitivity or high mechanical resilience, but not both. The lack of robustness of available compliant and highly sensitive sensing mechanisms has confined their operation to laboratory settings, inhibiting their widespread deployment. Here we present a versatile and compliant transduction mechanism for high-sensitivity strain detection with high mechanical resilience. The mechanism relies upon changes in ohmic contact between stiff, micro-structured, anisotropically conductive meanders encapsulated by stretchable films. The mechanism achieves high sensitivity, with gauge factors greater than 85,000, while being adaptable to use with high-strength conductors, producing sensors resilient to adverse loading conditions. The sensing mechanism also exhibits high linearity, as well as insensitivity to bending and twisting deformations - important features for soft device applications. The potential impact of our technology is shown through the construction of a sensor-integrated, lightweight, textile-based arm sleeve, which is able to recognize gestures without encumbering the hand. We demonstrate predictive tracking and classification of discrete gestures and continuous hand motions via detection of small muscle movements in the arm. The sleeve demonstration shows the potential of the SCARS technology for the development of unobtrusive, wearable biomechanical feedback systems and human-computer interfaces.
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    Data-Driven Design of a Dexterous Robotic Microsurgery System
    (ASME International, 2012) Hammond, Frank; Talbot, Simon; Wood, Robert; Howe, Robert
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    Measurement System for the Characterization of Micro-Manipulation Motion and Force
    (ASME International, 2013) Hammond, Frank; Talbot, Simon; Wood, Robert; Howe, Robert
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    Fluid-driven origami-inspired artificial muscles
    (National Academy of Sciences, 2017) Li, Shuguang; Vogt, Daniel; Rus, Daniela; Wood, Robert
    Artificial muscles hold promise for safe and powerful actuation for myriad common machines and robots. However, the design, fabrication, and implementation of artificial muscles are often limited by their material costs, operating principle, scalability, and single-degree-of-freedom contractile actuation motions. Here we propose an architecture for fluid-driven origami-inspired artificial muscles. This concept requires only a compressible skeleton, a flexible skin, and a fluid medium. A mechanical model is developed to explain the interaction of the three components. A fabrication method is introduced to rapidly manufacture low-cost artificial muscles using various materials and at multiple scales. The artificial muscles can be programed to achieve multiaxial motions including contraction, bending, and torsion. These motions can be aggregated into systems with multiple degrees of freedom, which are able to produce controllable motions at different rates. Our artificial muscles can be driven by fluids at negative pressures (relative to ambient). This feature makes actuation safer than most other fluidic artificial muscles that operate with positive pressures. Experiments reveal that these muscles can contract over 90% of their initial lengths, generate stresses of ∼600 kPa, and produce peak power densities over 2 kW/kg—all equal to, or in excess of, natural muscle. This architecture for artificial muscles opens the door to rapid design and low-cost fabrication of actuation systems for numerous applications at multiple scales, ranging from miniature medical devices to wearable robotic exoskeletons to large deployable structures for space exploration.
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    Biocompatible Pressure Sensing Skins for Minimally Invasive Surgical Instruments
    (Institute of Electrical and Electronics Engineers (IEEE), 2016) Arabagi, Veaceslav; Felfoul, Ouajdi; Gosline, Andrew H.; Wood, Robert; Dupont, Pierre
    Kinematic models of concentric tube robots have matured from considering only tube bending to considering tube twisting as well as external loading. While these models have been demonstrated to approximate actual behavior, modeling error can be significant for medical applications that often call for positioning accuracy of 1–2mm. As an alternative to moving to more complex models, this paper proposes using sensing to adaptively update model parameters during robot operation. Advantages of this method are that the model is constantly tuning itself to provide high accuracy in the region of the workspace where it is currently operating. It also adapts automatically to changes in robot shape and compliance associated with the insertion and removal of tools through its lumen. As an initial exploration of this approach, a recursive on-line estimator is proposed and evaluated experimentally.
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    Controllable water surface to underwater transition through electrowetting in a hybrid terrestrial-aquatic microrobot
    (Nature Publishing Group UK, 2018) Chen, Yufeng; Doshi, Neel; Goldberg, Benjamin; Wang, Hongqiang; Wood, Robert
    Several animal species demonstrate remarkable locomotive capabilities on land, on water, and under water. A hybrid terrestrial-aquatic robot with similar capabilities requires multimodal locomotive strategies that reconcile the constraints imposed by the different environments. Here we report the development of a 1.6 g quadrupedal microrobot that can walk on land, swim on water, and transition between the two. This robot utilizes a combination of surface tension and buoyancy to support its weight and generates differential drag using passive flaps to swim forward and turn. Electrowetting is used to break the water surface and transition into water by reducing the contact angle, and subsequently inducing spontaneous wetting. Finally, several design modifications help the robot overcome surface tension and climb a modest incline to transition back onto land. Our results show that microrobots can demonstrate unique locomotive capabilities by leveraging their small size, mesoscale fabrication methods, and surface effects.
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    Artificial insect wings of diverse morphology for flapping-wing micro air vehicles
    (IOP Publishing, 2009) Shang, J K; Combes, Stacey A.; Finio, B M; Wood, Robert
    The development of flapping-wing micro air vehicles (MAVs) demands a systematic exploration of the available design space to identify ways in which the unsteady mechanisms governing flapping-wing flight can best be utilized for producing optimal thrust or maneuverability. Mimicking the wing kinematics of biological flight requires examining the potential effects of wing morphology on flight performance, as wings may be specially adapted for flapping flight. For example, insect wings passively deform during flight, leading to instantaneous and potentially unpredictable changes in aerodynamic behavior. Previous studies have postulated various explanations for insect wing complexity, but there lacks a systematic approach for experimentally examining the functional significance of components of wing morphology, and for determining whether or not natural design principles can or should be used for MAVs. In this work, a novel fabrication process to create centimeter-scale wings of great complexity is introduced; via this process, a wing can be fabricated with a large range of desired mechanical and geometric characteristics. We demonstrate the versatility of the process through the creation of planar, insect-like wings with biomimetic venation patterns that approximate the mechanical properties of their natural counterparts under static loads. This process will provide a platform for studies investigating the effects of wing morphology on flight dynamics, which may lead to the design of highly maneuverable and efficient MAVs and insight into the functional morphology of natural wings.
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    A Resilient, Untethered Soft Robot
    (Mary Ann Liebert Inc, 2014) Tolley, Michael T.; Shepherd, Robert F.; Mosadegh, Bobak; Galloway, Kevin C; Wehner, Michael; Karpelson, Michael; Wood, Robert; Whitesides, George
    A pneumatically powered, fully untethered mobile soft robot is described. Composites consisting of silicone elastomer, polyaramid fabric, and hollow glass microspheres were used to fabricate a sufficiently large soft robot to carry the miniature air compressors, battery, valves, and controller needed for autonomous operation. Fabrication techniques were developed to mold a 0.65-meter-long soft body with modified Pneu-Net actuators capable of operating at the elevated pressures (up to 138 kPa) required to actuate the legs of the robot and hold payloads of up to 8 kg. The soft robot is safe to interact with during operation, and its silicone body is innately resilient to a variety of adverse environmental conditions including snow, puddles of water, direct (albeit limited) exposure to flames, and the crushing force of being run over by an automobile.
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    A 3D-printed, functionally graded soft robot powered by combustion
    (American Association for the Advancement of Science (AAAS), 2015) Bartlett, Nicholas; Tolley, M. T.; Overvelde, Johannes; Weaver, J; Mosadegh, Bobak; Bertoldi, Katia; Whitesides, George; Wood, Robert
    Roboticists have begun to design biologically inspired robots with soft or partially soft bodies, which have the potential to be more robust and adaptable, and safer for human interaction, than traditional rigid robots. However, key challenges in the design and manufacture of soft robots include the complex fabrication processes and the interfacing of soft and rigid components. We used multimaterial three-dimensional (3D) printing to manufacture a combustion-powered robot whose body transitions from a rigid core to a soft exterior. This stiffness gradient, spanning three orders of magnitude in modulus, enables reliable interfacing between rigid driving components (controller, battery, etc.) and the primarily soft body, and also enhances performance. Powered by the combustion of butane and oxygen, this robot is able to perform untethered jumping.