1,039 research outputs found
Walking Stabilization Using Step Timing and Location Adjustment on the Humanoid Robot, Atlas
While humans are highly capable of recovering from external disturbances and
uncertainties that result in large tracking errors, humanoid robots have yet to
reliably mimic this level of robustness. Essential to this is the ability to
combine traditional "ankle strategy" balancing with step timing and location
adjustment techniques. In doing so, the robot is able to step quickly to the
necessary location to continue walking. In this work, we present both a new
swing speed up algorithm to adjust the step timing, allowing the robot to set
the foot down more quickly to recover from errors in the direction of the
current capture point dynamics, and a new algorithm to adjust the desired
footstep, expanding the base of support to utilize the center of pressure
(CoP)-based ankle strategy for balance. We then utilize the desired centroidal
moment pivot (CMP) to calculate the momentum rate of change for our
inverse-dynamics based whole-body controller. We present simulation and
experimental results using this work, and discuss performance limitations and
potential improvements
Straight-Leg Walking Through Underconstrained Whole-Body Control
We present an approach for achieving a natural, efficient gait on bipedal
robots using straightened legs and toe-off. Our algorithm avoids complex height
planning by allowing a whole-body controller to determine the straightest
possible leg configuration at run-time. The controller solutions are biased
towards a straight leg configuration by projecting leg joint angle objectives
into the null-space of the other quadratic program motion objectives. To allow
the legs to remain straight throughout the gait, toe-off was utilized to
increase the kinematic reachability of the legs. The toe-off motion is achieved
through underconstraining the foot position, allowing it to emerge naturally.
We applied this approach of under-specifying the motion objectives to the Atlas
humanoid, allowing it to walk over a variety of terrain. We present both
experimental and simulation results and discuss performance limitations and
potential improvements.Comment: Submitted to 2018 IEEE International Conference on Robotics and
Automatio
3-Hydroxy-2,6-dinitroacetophenone: an unusual substitution pattern resulting from nitration of 3-hydroxyacetophenone
Nitration of 3-hydroxyacetophenone gives 2,6-dinitro-3-hydroxyacetophenone, C8H6N206, in which the nitro groups have entered the sterically least favourable positions in the aromatic nucleus. None of the expected
substitution in the 4-position was observed. The two nitro groups flanking the carbonyl side chain are different in that one is in the plane of the aryl ring but the other
is twisted well out of the plane
Bright Lenses and Optical Depth
In gravitational lensing, the concept of optical depth assumes the lens is
dark. Several microlensing detections have now been made where the lens may be
bright. Relations are developed between apparent and absolute optical depth in
the regime of the apparent and absolute brightness of the lens. An apparent
optical depth through bright lenses is always less than the true, absolute
optical depth. The greater the intrinsic brightness of the lens, the more
likely it will be found nearer the source.Comment: 18 pages including 4 figures, AASTeX, ApJ in pres
Commensurate antiferromagnetic ordering in Ba(Fe{1-x}Co{x})2As2 determined by x-ray resonant magnetic scattering at the Fe K-edge
We describe x-ray resonant magnetic diffraction measurements at the Fe K-edge
of both the parent BaFe2As2 and superconducting Ba(Fe0.953Co0.047)2As2
compounds. From these high-resolution measurements we conclude that the
magnetic structure is commensurate for both compositions. The energy spectrum
of the resonant scattering is in reasonable agreement with theoretical
calculations using the full-potential linear augmented plane wave method with a
local density functional.Comment: 5 pages, 3 figures; accepted for publication in Phys. Rev. B Rapid
Com
- …