716 research outputs found
Technical Report: A Contact-aware Feedback CPG System for Learning-based Locomotion Control in a Soft Snake Robot
Integrating contact-awareness into a soft snake robot and efficiently
controlling its locomotion in response to contact information present
significant challenges. This paper aims to solve contact-aware locomotion
problem of a soft snake robot through developing bio-inspired contact-aware
locomotion controllers. To provide effective contact information for the
controllers, we develop a scale covered sensor structure mimicking natural
snakes' \textit{scale sensilla}. In the design of control framework, our core
contribution is the development of a novel sensory feedback mechanism of the
Matsuoka central pattern generator (CPG) network. This mechanism allows the
Matsuoka CPG system to work like a "spine cord" in the whole contact-aware
control scheme, which simultaneously takes the stimuli including tonic input
signals from the "brain" (a goal-tracking locomotion controller) and sensory
feedback signals from the "reflex arc" (the contact reactive controller), and
generate rhythmic signals to effectively actuate the soft snake robot to
slither through densely allocated obstacles. In the design of the "reflex arc",
we develop two types of reactive controllers -- 1) a reinforcement learning
(RL) sensor regulator that learns to manipulate the sensory feedback inputs of
the CPG system, and 2) a local reflexive sensor-CPG network that directly
connects sensor readings and the CPG's feedback inputs in a special topology.
These two reactive controllers respectively facilitate two different
contact-aware locomotion control schemes. The two control schemes are tested
and evaluated in the soft snake robot, showing promising performance in the
contact-aware locomotion tasks. The experimental results also further verify
the benefit of Matsuoka CPG system in bio-inspired robot controller design.Comment: 17 pages, 19 figure
Autonomous Soft Robotic Fish Capable of Escape Maneuvers Using Fluidic Elastomer Actuators
In this work we describe an autonomous soft-bodied robot that is both self-contained and capable of rapid, continuum-body motion. We detail the design, modeling, fabrication, and control of the soft fish, focusing on enabling the robot to perform rapid escape responses. The robot employs a compliant body with embedded actuators emulating the slender anatomical form of a fish. In addition, the robot has a novel fluidic actuation system that drives body motion and has all the subsystems of a traditional robot onboard: power, actuation, processing, and control. At the core of the fish's soft body is an array of fluidic elastomer actuators. We design the fish to emulate escape responses in addition to forward swimming because such maneuvers require rapid body accelerations and continuum-body motion. These maneuvers showcase the performance capabilities of this self-contained robot. The kinematics and controllability of the robot during simulated escape response maneuvers are analyzed and compared with studies on biological fish. We show that during escape responses, the soft-bodied robot has similar input–output relationships to those observed in biological fish. The major implication of this work is that we show soft robots can be both self-contained and capable of rapid body motion.National Science Foundation (U.S.) (NSF IIS1226883)National Science Foundation (U.S.) (NSF CCF1138967)National Science Foundation (U.S.) (1122374
A Soft Robotic Wearable Wrist Device for Kinesthetic Haptic Feedback
Advances in soft robotics provide a unique approach for delivering haptic feedback to a user by a soft wearable device. Such devices can apply forces directly on the human joints, while still maintaining the safety and flexibility necessary for use in close proximity to the human body. To take advantage of these properties, we present a new haptic wrist device using pressure-driven soft actuators called reverse pneumatic artificial muscles (rPAMs) mounted on four sides of the wrist. These actuators are originally pre-strained and release compressive stress under pressure, applying a safe torque around the wrist joints while being compact and portable, representing the first soft haptic device capable of real-time feedback. To demonstrate the functional utility of this device, we created a virtual path-following task, wherein the user employs the motion of their wrist to control their embodied agent. We used the haptic wrist device to assist the user in following the path and study their performance with and without haptic feedback in multiple scenarios. Our results quantify the effect of wearable soft robotic haptic feedback on user performance. Specifically, we observed that our haptic feedback system improved the performance of users following complicated paths in a statistically significant manner, but did not show improvement for simple linear paths. Based on our findings, we anticipate broader applications of wearable soft robotic haptic devices toward intuitive user interactions with robots, computers, and other users
Self-folding with shape memory composites
Origami-inspired manufacturing can produce complex structures and machines by folding two-dimensional composites into three-dimensional structures. This fabrication technique is potentially less expensive, faster, and easier to transport than more traditional machining methods, including 3-D printing. Self-folding enhances this method by minimizing the manual labor involved in folding, allowing for complex geometries and enabling remote or automated assembly. This paper demonstrates a novel method of self-folding hinges using shape memory polymers (SMPs), paper, and resistive circuits to achieve localized and individually addressable folding at low cost. A model for the torque exerted by these composites was developed and validated against experimental data, in order to determine design rules for selecting materials and designing hinges. Torque was shown to increase with SMP thickness, resistive circuit width, and supplied electrical current. This technique was shown to be capable of complex geometries, as well as locking assemblies with sequential folds. Its functionality and low cost make it an ideal basis for a new type of printable manufacturing based on two-dimensional fabrication techniques.National Science Foundation (U.S.) (award number CCF-1138967)National Science Foundation (U.S.) (award number EFRI-1240383
Nicotine Normalizes Intracellular Subunit Stoichiometry of Nicotinic Receptors Carrying Mutations Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy
Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE)
is linked with high penetrance to several distinct nicotinic receptor
(nAChR) mutations. We studied (α4)_3(2β)_2 versus
(α4)_2(β2)_3 subunit stoichiometry for five channel-lining M2 domain
mutations: S247F, S252L, 776ins3 in α4, V287L, and
V287M in β2. α4 and β2 subunits were constructed with all
possible combinations of mutant and wild-type (WT) M2 regions,
of cyan and yellow fluorescent protein, and of fluorescent
and nonfluorescent M3-M4 loops. Sixteen fluorescent
subunit combinations were expressed in N2a cells. Forster
resonance energy transfer (FRET) was analyzed by donor recovery
after acceptor photobleaching and by pixel-by-pixel
sensitized emission, with confirmation by fluorescence intensity
ratios. Because FRET efficiency is much greater for adjacent
than for nonadjacent subunits and the α4 and β2 subunits
occupy specific positions in nAChR pentamers, observed FRET
efficiencies from (α4)_3(β2)_2 carrying fluorescent α4 subunits
were significantly higher than for (α4)_2(β2)_3; the converse was
found for fluorescent 2 subunits. All tested ADNFLE mutants
produced 10 to 20% increments in the percentage of intracellular
(α4)_3(β2)_2 receptors compared with WT subunits. In contrast,
24- to 48-h nicotine (1 µM) exposure increased the proportion
of (α4)_2(β2)_3 in WT receptors and also returned subunit
stoichiometry to WT levels for α4S248F and β2V287L nAChRs.
These observations may be relevant to the decreased seizure
frequency in patients with ADNFLE who use tobacco products
or nicotine patches. Fluorescence-based investigations of
nAChR subunit stoichiometry may provide efficient drug discovery
methods for nicotine addiction or for other disorders
that result from dysregulated nAChRs
Ovarian Hyperstimulation Syndrome with pleural effusion: a case report
In corporate governance systems boards perform three functions: the interlocking function (from a resource-dependency and network perspective), a monitoring function (from an agency perspective), and a strategic function (from a strategic choice perspective). In a one-tier board the board of directors incorporates non-executive directors (outsiders, they sometimes represent the interests of key-stakeholders) and executive directors (top management) of the firm. In a two-tier board there is a clear distinction between the directors as members of a supervisory board and the top management team. The board serves in this respect as a supervisory board vis à vis the management board. In the Netherlands a two-tier board is prevalent. Firms who act under the structural regime have boards that are characterized by the co-option principle. This means that board members have to act in the best interest of the firm and ultimately choose each other (and are not chosen by the
shareholders or other stakeholders). Co-option has some advantages, but also some clear drawbacks, such as the potentiality of groupthink. The structural regime and other governance regimes, in which the relationship between supervisory board and management board is established, have moderating effects on the hypothesized relationships between the three functions and performance of firms.
CSi - a joint industry project into CPTUs in silty soils
publishedVersio
Remodeling of Abdominal Aortic Angulation and Curvature After Endovascular Aneurysm Repair in Patients With vs Without Late Type Ia Endoleak or Endograft Migration
Purpose: To investigate aortic remodeling of the supra- and infrarenal aorta from preoperative to 1 month and midterm follow-up after endovascular aneurysm repair (EVAR) by analyzing changes in angulation and curvature in patients with vs without late type Ia endoleak or device migration. Materials and Methods: From a multicenter database, 35 patients (mean age 76 +/- 5 years; 31 men) were identified with late (>1 year) type Ia endoleak or endograft migration (>= 10 mm) and defined as the complication group. The control group consisted of 53 patients (mean age 75 +/- 7 years; 48 men) with >1-year computed tomography angiography (CTA) follow-up and no evidence of endoleaks. Suprarenal and infrarenal angles were measured on centerline reconstructions of the preoperative, 1-month, and midterm CTA scans. The value and location relative to baseline of maximum suprarenal and infrarenal curvature were determined semiautomatically using dedicated software. Changes were determined at 1 month compared with the preoperative CTA and at midterm compared with 1 month. Results: Preoperative suprarenal angulation was significantly greater in the complication group compared to the controls (34 degrees +/- 18 degrees vs 24 degrees +/- 17 degrees, p=0.008). It decreased significantly at 1 month in the complication group (29 degrees +/- 16 degrees, p=0.011) and at midterm follow-up in the controls (20 degrees +/- 19 degrees, p Conclusion: At midterm follow-up, significant differences in supra- and infrarenal angulation and curvature were observed between patients with vs without type Ia endoleak or migration. The location of the maximum curvature shifted distally in patients with complications. The aortic morphology is more stable during midterm follow-up in the patients without endoleaks
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