168 research outputs found
Tactile-Sensitive NewtonianVAE for High-Accuracy Industrial Connector Insertion
An industrial connector insertion task requires submillimeter positioning and
grasp pose compensation for a plug. Thus, highly accurate estimation of the
relative pose between a plug and socket is fundamental for achieving the task.
World models are promising technologies for visuomotor control because they
obtain appropriate state representation to jointly optimize feature extraction
and latent dynamics model. Recent studies show that the NewtonianVAE, a type of
the world model, acquires latent space equivalent to mapping from images to
physical coordinates. Proportional control can be achieved in the latent space
of NewtonianVAE. However, applying NewtonianVAE to high-accuracy industrial
tasks in physical environments is an open problem. Moreover, the existing
framework does not consider the grasp pose compensation in the obtained latent
space. In this work, we proposed tactile-sensitive NewtonianVAE and applied it
to a USB connector insertion with grasp pose variation in the physical
environments. We adopted a GelSight-type tactile sensor and estimated the
insertion position compensated by the grasp pose of the plug. Our method trains
the latent space in an end-to-end manner, and no additional engineering and
annotation are required. Simple proportional control is available in the
obtained latent space. Moreover, we showed that the original NewtonianVAE fails
in some situations, and demonstrated that domain knowledge induction improves
model accuracy. This domain knowledge can be easily obtained using robot
specification and grasp pose error measurement. We demonstrated that our
proposed method achieved a 100\% success rate and 0.3 mm positioning accuracy
in the USB connector insertion task in the physical environment. It
outperformed SOTA CNN-based two-stage goal pose regression with grasp pose
compensation using coordinate transformation.Comment: 7 pages, 4 figure
Learning Compliant Stiffness by Impedance Control-Aware Task Segmentation and Multi-objective Bayesian Optimization with Priors
Rather than traditional position control, impedance control is preferred to
ensure the safe operation of industrial robots programmed from demonstrations.
However, variable stiffness learning studies have focused on task performance
rather than safety (or compliance). Thus, this paper proposes a novel stiffness
learning method to satisfy both task performance and compliance requirements.
The proposed method optimizes the task and compliance objectives (T/C
objectives) simultaneously via multi-objective Bayesian optimization. We define
the stiffness search space by segmenting a demonstration into task phases, each
with constant responsible stiffness. The segmentation is performed by
identifying impedance control-aware switching linear dynamics (IC-SLD) from the
demonstration. We also utilize the stiffness obtained by proposed IC-SLD as
priors for efficient optimization. Experiments on simulated tasks and a real
robot demonstrate that IC-SLD-based segmentation and the use of priors improve
the optimization efficiency compared to existing baseline methods.Comment: Accepted to IROS202
Development of UPS-SMES as a protection from momentary voltage drop
We have been developing the UPS-SMES as a protection from momentary voltage drop and power failure. The superconducting system is suitable as electric power storage for large energy extraction in a short time. The most important feature of superconducting coil system for the UPS-SMES is easy handling and maintenance-free operation. We have selected low temperature superconducting (LTS) coils instead of high temperature superconducting (HTS) coils from the viewpoint of cost and performance. However, it is difficult for the conventional LTS coils to fulfill maintenance-free operation since the cooling methods are either pool boiling with liquid helium or forced flow of supercritical helium. Thus, a conduction cooled LTS pulse coil has been designed as a key component of the UPS-SMES. The development program of 1 MW, 1 sec UPS-SMES is explained
Ground-state properties of the one-dimensional attractive Hubbard model with confinement: a comparative study
We revisit the one-dimensional attractive Hubbard model by using the
Bethe-ansatz based density-functional theory and density-matrix renormalization
method. The ground-state properties of this model are discussed in details for
different fillings and different confining conditions in weak-to-intermediate
coupling regime. We investigate the ground-state energy, energy gap, and
pair-binding energy and compare them with those calculated from the canonical
Bardeen-Cooper-Schrieffer approximation. We find that the Bethe-ansatz based
density-functional theory is computationally easy and yields an accurate
description of the ground-state properties for weak-to-intermediate interaction
strength, different fillings, and confinements. In order to characterize the
quantum phase transition in the presence of a harmonic confinement, we
calculate the thermodynamic stiffness, the density-functional fidelity, and
fidelity susceptibility, respectively. It is shown that with the increase of
the number of particles or attractive interaction strength, the system can be
driven from the Luther-Emery-type phase to the composite phase of
Luther-Emery-like in the wings and insulating-like in the center.Comment: 13 pages with 10 figures and 2 table
Development of 1 MJ Conduction-Cooled LTS Pulse Coil for UPS-SMES
A 1 MW, 1 s UPS-SMES is being developed for a protection from a momentary voltage drop and an instant power failure. As a key technology of the UPS-SMES, we developed a prototype LTS pulse coil with a stored energy of 100 kJ and conducted cooling and excitation tests in 2005. The operation test of the prototype UPS-SMES using this 100 kJ coil with power converters have been performed in 2006. A 1 MJ coil was designed before the fabrication of the 100 kJ prototype coil. The superconductor, the electric insulation technique, the winding method, and the cooling structure used for the 100 kJ coil were based upon the 1 MJ coil design. The successful performance test results of the prototype 100 kJ coil validated the design concept and fabrication technique of the 1 MJ coil. According to the achievement of the prototype 100 kJ UPS-SMES, the 1 MJ conduction-cooled LTS pulse coil has been fabricated successfully. The successful experimental results of the 100 kJ prototype coil with power converters and the fabrication procedure of the 1 MJ full size coil are described
Inhibition of EP4 Signaling Attenuates Aortic Aneurysm Formation
BACKGROUND: Aortic aneurysm is a common but life-threatening disease among the elderly, for which no effective medical therapy is currently available. Activation of prostaglandin E(2) (PGE(2)) is known to increase the expression of matrix metalloproteinase (MMP) and the release of inflammatory cytokines, and may thus exacerbate abdominal aortic aneurysm (AAA) formation. We hypothesized that selective blocking of PGE(2), in particular, EP4 prostanoid receptor signaling, would attenuate the development of AAA. METHODS AND FINDINGS: Immunohistochemical analysis of human AAA tissues demonstrated that EP4 expression was greater in AAA areas than that in non-diseased areas. Interestingly, EP4 expression was proportional to the degree of elastic fiber degradation. In cultured human aortic smooth muscle cells (ASMCs), PGE(2) stimulation increased EP4 protein expression (1.4 ± 0.08-fold), and EP4 stimulation with ONO-AE1-329 increased MMP-2 activity and interleukin-6 (IL-6) production (1.4 ± 0.03- and 1.7 ± 0.14-fold, respectively, P<0.05). Accordingly, we examined the effect of EP4 inhibition in an ApoE(-/-) mouse model of AAA infused with angiotensin II. Oral administration of ONO-AE3-208 (0.01-0.5 mg/kg/day), an EP4 antagonist, for 4 weeks significantly decreased the formation of AAA (45-87% reduction, P<0.05). Similarly, EP4(+/-)/ApoE(-/-) mice exhibited significantly less AAA formation than EP4(+/+)/ApoE(-/-) mice (76% reduction, P<0.01). AAA formation induced by periaortic CaCl(2) application was also reduced in EP4(+/-) mice compared with wild-type mice (73% reduction, P<0.001). Furthermore, in human AAA tissue organ cultures containing SMCs and macrophages, doses of the EP4 antagonist at 10-100 nM decreased MMP-2 activation and IL-6 production (0.6 ± 0.06- and 0.7 ± 0.06-fold, respectively, P<0.05) without increasing MMP-9 activity or MCP-1 secretion. Thus, either pharmacological or genetic EP4 inhibition attenuated AAA formation in multiple mouse and human models by lowering MMP activity and cytokine release. CONCLUSION: An EP4 antagonist that prevents the activation of MMP and thereby inhibits the degradation of aortic elastic fiber may serve as a new strategy for medical treatment of AAA
Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material
We present photometric, spectroscopic and polarimetric observations of the
intermediate-luminosity Type IIP supernova (SN) 2021gmj from 1 to 386 days
after the explosion. The peak absolute V-band magnitude of SN 2021gmj is -15.5
mag, which is fainter than that of normal Type IIP SNe. The spectral evolution
of SN 2021gmj resembles that of other sub-luminous supernovae: the optical
spectra show narrow P-Cygni profiles, indicating a low expansion velocity. We
estimate the progenitor mass to be about 12 Msun from the nebular spectrum and
the 56Ni mass to be about 0.02 Msun from the bolometric light curve. We also
derive the explosion energy to be about 3 x 10^{50} erg by comparing numerical
light curve models with the observed light curves. Polarization in the plateau
phase is not very large, suggesting nearly spherical outer envelope. The early
photometric observations capture the rapid rise of the light curve, which is
likely due to the interaction with a circumstellar material (CSM). The broad
emission feature formed by highly-ionized lines on top of a blue continuum in
the earliest spectrum gives further indication of the CSM at the vicinity of
the progenitor. Our work suggests that a relatively low-mass progenitor of an
intermediate-luminosity Type IIP SN can also experience an enhanced mass loss
just before the explosion, as suggested for normal Type IIP SNe.Comment: 18 pages, 16 figures, resubmitted to MNRAS after addressing referee
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