4,728 research outputs found
Force/Torque Sensing for Soft Grippers using an External Camera
Robotic manipulation can benefit from wrist-mounted force/torque (F/T)
sensors, but conventional F/T sensors can be expensive, difficult to install,
and damaged by high loads. We present Visual Force/Torque Sensing (VFTS), a
method that visually estimates the 6-axis F/T measurement that would be
reported by a conventional F/T sensor. In contrast to approaches that sense
loads using internal cameras placed behind soft exterior surfaces, our approach
uses an external camera with a fisheye lens that observes a soft gripper. VFTS
includes a deep learning model that takes a single RGB image as input and
outputs a 6-axis F/T estimate. We trained the model with sensor data collected
while teleoperating a robot (Stretch RE1 from Hello Robot Inc.) to perform
manipulation tasks. VFTS outperformed F/T estimates based on motor currents,
generalized to a novel home environment, and supported three autonomous tasks
relevant to healthcare: grasping a blanket, pulling a blanket over a manikin,
and cleaning a manikin's limbs. VFTS also performed well with a manually
operated pneumatic gripper. Overall, our results suggest that an external
camera observing a soft gripper can perform useful visual force/torque sensing
for a variety of manipulation tasks.Comment: Accepted for presentation at 2023 IEEE International Conference on
Robotics and Automation (ICRA
Visual Contact Pressure Estimation for Grippers in the Wild
Sensing contact pressure applied by a gripper can benefit autonomous and
teleoperated robotic manipulation, but adding tactile sensors to a gripper's
surface can be difficult or impractical. If a gripper visibly deforms, contact
pressure can be visually estimated using images from an external camera that
observes the gripper. While researchers have demonstrated this capability in
controlled laboratory settings, prior work has not addressed challenges
associated with visual pressure estimation in the wild, where lighting,
surfaces, and other factors vary widely. We present a model and associated
methods that enable visual pressure estimation under widely varying conditions.
Our model, Visual Pressure Estimation for Robots (ViPER), takes an image from
an eye-in-hand camera as input and outputs an image representing the pressure
applied by a soft gripper. Our key insight is that force/torque sensing can be
used as a weak label to efficiently collect training data in settings where
pressure measurements would be difficult to obtain. When trained on this weakly
labeled data combined with fully labeled data that includes pressure
measurements, ViPER outperforms prior methods, enables precision manipulation
in cluttered settings, and provides accurate estimates for unseen conditions
relevant to in-home use.Comment: Accepted for presentation at the 2023 IEEE/RSJ International
Conference on Intelligent Robots and Systems (IROS 2023
ForceSight: Text-Guided Mobile Manipulation with Visual-Force Goals
We present ForceSight, a system for text-guided mobile manipulation that
predicts visual-force goals using a deep neural network. Given a single RGBD
image combined with a text prompt, ForceSight determines a target end-effector
pose in the camera frame (kinematic goal) and the associated forces (force
goal). Together, these two components form a visual-force goal. Prior work has
demonstrated that deep models outputting human-interpretable kinematic goals
can enable dexterous manipulation by real robots. Forces are critical to
manipulation, yet have typically been relegated to lower-level execution in
these systems. When deployed on a mobile manipulator equipped with an
eye-in-hand RGBD camera, ForceSight performed tasks such as precision grasps,
drawer opening, and object handovers with an 81% success rate in unseen
environments with object instances that differed significantly from the
training data. In a separate experiment, relying exclusively on visual servoing
and ignoring force goals dropped the success rate from 90% to 45%,
demonstrating that force goals can significantly enhance performance. The
appendix, videos, code, and trained models are available at
https://force-sight.github.io/
Ponderomotive effects in multiphoton pair production
The Dirac-Heisenberg-Wigner formalism is employed to investigate
electron-positron pair production in cylindrically symmetric but otherwise
spatially inhomogeneous, oscillating electric fields. The oscillation
frequencies are hereby tuned to obtain multiphoton pair production in the
nonperturbative threshold regime. An effective mass as well as a
trajectory-based semi-classical analysis are introduced in order to interpret
the numerical results for the distribution functions as well as for the
particle yields and spectra. The results, including the asymptotic particle
spectra, display clear signatures of ponderomotive forces.Comment: 9 pages, 3 Tables, 3 Figure
Recommended from our members
Adaptive model reference control of highly maneuverable high performance aircraft
This thesis presents an adaptive model reference controller for a highly
maneuverable high performance aircraft, in particular, a modified F18. An adaptive
controller is developed to maneuver an aircraft at a high angle of attack. Thus, the
aircraft is required to fly over a highly nonlinear flight regime. The adaptive controller
presented in this thesis can be viewed as a combination of a linear and a nonlinear
controller. Around a fixed flight condition the adaptive controller converges to a linear
controller; however, the controller remains a nonlinear controller during maneuvers.
The contributions of this thesis lie in two areas. The first area is in control.
A successful application of linear adaptive control is presented for a highly nonlinear
system. A new method is used to generate the reference trajectory. The reference
model uses output feedback to improve the reference trajectory. It is shown that this
improvement is necessary because of the control limitations. This work is also
important to the control of highly maneuverable high performance aircraft. A
successful adaptive controller has been developed to rapidly maneuver an aircraft to
a high angle of attack. The main focus of this thesis is adaptive control
Trend analysis of tuberculosis case notifications with scale-up of antiretroviral therapy and roll-out of isoniazid preventive therapy in Zimbabwe, 2000-2018.
OBJECTIVES: Antiretroviral therapy (ART) and isoniazid preventive therapy (IPT) are known to have a tuberculosis (TB) protective effect at the individual level among people living with HIV (PLHIV). In Zimbabwe where TB is driven by HIV infection, we have assessed whether there is a population-level association between IPT and ART scale-up and annual TB case notification rates (CNRs) from 2000 to 2018. DESIGN: Ecological study using aggregate national data. SETTING: Annual aggregate national data on TB case notification rates (stratified by TB category and type of disease), numbers (and proportions) of PLHIV in ART care and of these, numbers (and proportions) ever commenced on IPT. RESULTS: ART coverage in the public sector increased from 1.1 million PLHIV patients) by December 2018, while IPT coverage among PLHIV in ART care increased from <1% (98 PLHIV) in 2012 to ~33% (373 917 PLHIV) by December 2018. These HIV-related interventions were associated with significant declines in TB CNRs: between the highest CNR prior to national roll-out of ART (in 2004) to the lowest recorded CNR after national IPT roll-out from 2012, these were (1) for all TB case (510 to 173 cases/100 000 population; 66% decline, p<0.001); (2) for those with new TB (501 to 159 cases/100 000 population; 68% decline, p<0.001) and (3) for those with new clinically diagnosed PTB (284 to 63 cases/100 000 population; 77.8% decline, p<0.001). CONCLUSIONS: This study shows the population-level impact of the continued scale-up of ART among PLHIV and the national roll-out of IPT among those in ART care in reducing TB, particularly clinically diagnosed TB which is largely associated with HIV. There are further opportunities for continued mitigation of TB with increasing coverage of ART and in particular IPT which still has a low coverage
Visual Estimation of Fingertip Pressure on Diverse Surfaces using Easily Captured Data
People often use their hands to make contact with the world and apply
pressure. Machine perception of this important human activity could be widely
applied. Prior research has shown that deep models can estimate hand pressure
based on a single RGB image. Yet, evaluations have been limited to controlled
settings, since performance relies on training data with high-resolution
pressure measurements that are difficult to obtain. We present a novel approach
that enables diverse data to be captured with only an RGB camera and a
cooperative participant. Our key insight is that people can be prompted to
perform actions that correspond with categorical labels describing contact
pressure (contact labels), and that the resulting weakly labeled data can be
used to train models that perform well under varied conditions. We demonstrate
the effectiveness of our approach by training on a novel dataset with 51
participants making fingertip contact with instrumented and uninstrumented
objects. Our network, ContactLabelNet, dramatically outperforms prior work,
performs well under diverse conditions, and matched or exceeded the performance
of human annotators
Dispersion Relations and Rescattering Effects in B Nonleptonic Decays
Recently, the final state strong interactions in nonleptonic B decays were
investigated in a formalism based on hadronic unitarity and dispersion
relations in terms of the off-shell mass squared of the meson. We consider
an heuristic derivation of the dispersion relations in the mass variables using
the reduction LSZ formalism and find a discrepancy between the spectral
function and the dispersive variable used in the recent works. The part of the
unitarity sum which describes final state interactions is shown to appear as
spectral function in a dispersion relation based on the analytic continuation
in the mass squared of one final particles. As an application, by combining
this formalism with Regge theory and SU(3) flavour symmetry we obtain
constraints on the tree and the penguin amplitudes of the decay .Comment: 17 pages, Latex, 2 figure
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